This section is for attacking a planet from orbit. The next section is for defending a planet from orbit.

After all the interplanetary battles are over, and the defender's space fleets have been reduced to ionized plasma or fled in panic, the pendultimate stage is entered. The defenders orbital and planetary fortresses have to be neutralized, or at least neutralized enough so that ground troops can be inserted to set up a beachhead.

But please understand that bombing a planet back into the stone age is something that makes more sense in simplistic space operas, not in realpolitik.


A consideration for this:

If warfare is about causing the maximum destruction, these space siege scenarios make sense.

If warfare is about achieving political objectives by other means, you need to either leave someone to negotiate the surrender with, or leave something worth occupying.

If you're looking for numbers of boots on the ground to do occupation, look at the rules in Squadron Strike, which I had vetted by people who teach the US Army occupation duty and body counts.

One of the problems with wargames on this scale is that they're usually divorced from realpolitik.

A good way to illustrate this is that if the real world worked like most space gamers think planetary conquest worked, we'd'v'e given India a northern coast by making sure that Afghanistan had a mean altitude of 200 meters below datum...

Ken does have a good point. The motivation of the invaders puts limits on the allowed invasion techniques. If the invaders want slaves, it is counterproductive to kill every living thing on the defending planet. If the invaders want real estate, it is counterproductive to dust the planet with enough radioactive material to render it uninhabitable for the next ten thousand years. And so on.


The further underlying problem is: what do the aliens want? What is there that's easier to get by invading than by mining elsewhere in the solar system/local group/galaxy? The objective drives the means of invasion. Political domination is most easily achieved through infiltration — many politicians are easily bought or controlled through a combination of threats and gifts. (As Winchell posted while I typed!) Objectives beyond that seem like more trouble than they are worth.

James Sterrett

The lack of a logical reason for invasion is up to the author to devise a solution for. Some of the motivational questions can be side-stepped by assuming the invasion is not an alien one, but instead a hypothetical human interstellar empire attempting to invade a human colony world. The motivation of the empire can be something stupidly human like "gotta collect 'em all!". This is actually the motivation in Larry Niven and Jerry Pournelle's The Mote In God's Eye. In that novel, there once was a loosely allied human interstellar empire that collapsed in a bloody secession war. The new imperium rose from the ashes, grimly determined that such wars will not happen ever again, and all human worlds must be incorporated into the empire with no exceptions.

If one must have aliens invading because they want some crucial resource, I like to use an analogy. Ordinary resources are not worth it. I don't care what you saw in the TV show V, Markus Baur points out that aliens invading Terra to steal our water makes about as much sense as Eskimos invading Central America to steal their ice. The same goes for gold, uranium, or our women. But what if we hand-wave an unknown resource, something that our scientists have not even discovered yet? (Wow, Zzazel! Their planet is incredibly rich in polka-dotted quarks!)

Then us poor humans will find ourselves in the same spot as a primitive African tribe who does not understand why these Western stranger want to bulldoze their village in order to dig up the dirt. The westerners tell the tribesmen that the dirt is called "Coltain", from which they can extract something called "Tantalum", which is absolutely vital for something called a "Cell Phone." But to the tribesmen, it looks just like the same dirt that is everywhere else, and more specifically, in places that are not under their beloved village. This causes hard feelings, but unfortunately the westerners have something else called "automatic rifles".





Proceed (+/-)? +




[SSP image elided from file]

The ultimate sanction available to the Existential Threats Primary Working Group at this time remains the use of weapons in contravention to Chapter I of the Ley Accords, to wit, weapons inducing severe uncontrolled stellar perturbation up to and including sequence change.

Three weapons systems matching this criterion are currently provisionally available under CASE DYSPEPTIC FLARE, representing extremal response cases to otherwise uncontrollable excessionary-level existential threats. Deployment of any of these weapons systems indicates a willingness to sterilize entire star systems, and in itself constitutes a x-level photon and particle radiation hazard to nearby (range < 868 light-orbits, typical) star systems. These systems are:

  • DYSPEPTIC FLARE SHANK, deployment of relativistic kill vehicle from the deterrent fleet maintained by the Black Flotilla on stellar impact course, inducing megascale coronal mass ejection; and
  • DYSPEPTIC FLARE EMBRACE, use of extended iron-bombing or (untested/theoretical) twist-pinch device to induce stellar core collapse/artificial nova; and
  • DYSPEPTIC FLARE HELLFIRE, deployment of CALYX HOLLOW or other strangelet device to stellar target, causing supernova-equivalent conversion event.

(WARNING: DYSPEPTIC FLARE HELLFIRE has intrinsic and unknown black-level-plus existential threat potential, since the energetic conversion event may (p > δ) spread undecayed strangelets at relativistic speeds sufficient to prolong their lifespan, enabling them to reach other star systems, where they may in turn trigger conversion events; as a worst-case scenario this could lead to self-replicant galactic annihilation.

As such, deployment of DYSPEPTIC FLARE HELLFIRE is absolutely prohibited except when the Transcendent warmind certifies that the x-risk prompting its deployment is of severity/range greater than the projected worst-case result.)

Note that as an extremal response case, deployment of CASE DYSPEPTIC FLARE requires consensus approval of the Imperial Security Executive, subject to override veto by vote of the Fifth Directorate overwatch, and Transcendent warmind approval.

Note also that special release conditions (noted below) apply to DYSPEPTIC FLARE, including but not limited to certified prior release of minimum three non-extremal response cases in failure state; threat (p > 0.5) of SKYSHOCK activity; unlimited collateral budget approval; and strategic ethics stricture <= ABYSSAL.


Communicating ANY PART of this NTK-A document to ANY SOPHONT other than those with preexisting originator-issued clearance, INCLUDING ITS EXISTENCE, is considered an alpha-level security breach and will be met with the most severe sanctions available, up to and including permanent erasure.

Proceed (+/-)?

Orbital Bombardment

For an in-depth look at the topic, go to the indispensable Future War Stories.

If the concept of a huge cannon indirectly attacking targets over the horizon is "artillery", the concept of attacking planetary ground targets from orbit is "ortillery." (term was invented by Game Designer's Workshop)

While it is possible to target the enemy even if the only friendly observers are in orbit, accuracy will be much improved if there is a human or robot on the ground close to the target giving target coordinates. These are called artillery observers, spotters, forward observer, fire support specialist, or fister. Though I suppose in this case they will be called ortillery observers instead.

Of course ortillery shares with artillery the ever-present danger of "friendly fire. If your army units are on the planet battling enemy units, and you have ortillery assets in orbit, often you will need to call down ortillery strikes on hostile positions. But there are many assorted failure modes that will result in the strike hitting your units instead. Weapon malfunctions, ortillery operator mistakes, inaccurate target coordinates, there are many opportunities for things to go badly wrong.

At the basic level one drops nuclear warheads. Next one uses kinetic energy weapons such as Project Thor or The Moon is a Harsh Mistress. Next is Colony Drop. Next is Asteroid Bombardment. Next is Relativistic Weapons. Finally there is the Planetary Nut-Cracker.


      The military threat potential created by the SPS system and its sub-systems is a reality that must be taken into account in planning if the perceived threat of any SPS system put up by the USA or any combination of organizations headquartered in the Western World is to be minimized. By doing this, as we’ve seen, the risk that the expensive SPS system will become a primary military target can be reduced.

     There’s already a military threat from space, but it’s not a primary threat.

     As of 1981, there are military operations going on in earth orbital space that involve unmanned command, control, communications, and intelligence (“C-cubed-I”) activities using various sorts of unmanned satellites. There have also been manned C-cubed-I activities being conducted from time to time by the Soviet Union with its cosmonauts in the Salyut space stations.

     Thus, the military organizations of both the USA and the USSR (and perhaps the PRC) are already taking advantage of the high ground of earth orbit.

     But, because of the United Nations’ 1967 “Treaty on the Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies,” weapons of mass destruction are prohibited from being placed on the Moon and other celestial bodies in space by treaty signatories.

     Nobody really knows what would happen if a signatory nation abrogated this Treaty of Principles and began deploying some sort of space weapon with a thermonuclear warhead. It’s just an agreement on principles. The most recent failure of the UN and its members to do anything in the Iranian hostage affair in spite of actions from the World Court confirms the principle of international law that says any treaty is effective only if nations tacitly abide by it, because there’s no mechanism to enforce any provision of any UN treaty. No UN member nation has yet to agree to surrender any of its national sovereignty to the UN.

     Therefore, in spite of UN treaties and a host of international agreements, a nation could covertly deploy one or more space weapons systems in conjunction with the SPS system by employing adapters that would enhance the military capabilities of the system. These military adapters fall into three major c/ategories:

  1. Adapters for force delivery.
  2. Adapters for remote sensing.
  3. Adapters for military support.

     Each of these three categories must be discussed to get the total picture because it may not be obvious that the SPS system offers opportunities to deploy military adapters. For example, the SPS system offers entirely new possibilities for force delivery in the space environment.

     First, an SPS unit can supply ten gigawatts of electrical power.

     Second, an SPS unit (along with LEO Base and GEO Base) is a permanently manned space facility.

     Third, an SPS unit is a geosynchronous orbital platform with complete housekeeping functions.

     Adapters for force delivery fall into three sub-categories:

     1. An SPS unit can be used as a base for projectile weapons which could be used to attack other satellites and even Earth targets. Such weapons include rocket-propelled missiles as well as simple projectiles such as rocks. Simple projectiles could evolve as a primary space weapon system because they could be launched with SPS-powered catapults or mass drivers. A mass driver launching hundreds of kilogram-mass projectiles per minute amounts to a Space Gatling Gun.

     Any projectile weapon capable of atmospheric entry could be targeted against Earth surface sites.

     For some applications it isn’t necessary for projectiles to carry any sort of a warhead at all because their masses and velocities—their kinetic energies—make them destructive in and of themselves. The impact of kilogram masses at several hundred meters per second can’t help but produce damage to space facilities, especially to critical components such as solar arrays, antennas, etc. Larger masses traveling at lower velocities become hazardous to larger facilities and their components.

     Projectile weapons without warheads and utilizing only their kinetic energies for destructive power against specific military targets on the ground or in space could be deployed as part of an SPS unit without violating any provision of any UN treaty.

     The UN Space Treaty prohibits only weapons of mass destruction. Projectile weapons with no nuclear warheads whatsoever can have destructive capabilities that can be pin-pointed. Even an Earth bombardment projectile weapon system deployed on an SPS need not be a weapon of mass destruction; it could be designed and launched in such a way that it would possess sharply limited military destructiveness against precise targets.

     Such selective weapon systems might be tolerated. However, city-busting weapons, nuclear or not, would increase the vulnerability of the SPS system, making the system a prime target in the opening moments of any war because the SPS system could not be permitted to launch its large projectiles. We would have transferred today’s doctrine of Mutually Assured Destruction (MAD) into space … and it might not work there as well as it apparently has on Earth. (As of this writing (1981), MAD has prevented all-out thermonuclear war between superpowers. How long the balance of terror can be maintained is a guessing game.)

     2. The second sub-category of force delivery adapters involves devices or vehicles called “manipulators.” Manipulators manipulate other space craft. As part of the SPS itself, or mounted on SPS deep space ships, or even mounted on their own specially-designed space vehicles, a manipulator could be used to do one of several things. It could seize a satellite having military potential or use, thus perpetrating a new activity called “satnapping. ” A satnapper would simply pull a satellite out of space, put it aboard, and hold it. Or a manipulator could be used to reach out and destroy or damage part of a satellite that was too large to satnap, thereby engaging in the activity of satellite mutilation ("satmute"). Since the USSR has already demonstrated the capability to reliably rendezvous and dock with another satellite using a remotely-controlled, unmanned satellite, satmute could be carried out by remotely-controlled space vehicles if there was a suspicion that the target satellite might be booby-trapped or carry some sort of self-defense system.

     3. The third sub-category of SPS military force delivery adapters involves the gee-whiz, Buck Rogers weapons that are only hinted at by both the USA and the USSR: the directed energy or beam weapons such as high energy lasers and particle beam weapons.

     There’s been a lot written about these beam weapons in the popular press as well as in the scientific and trade press. They’re real and they work. There is a very good possibility that beam weapons could be deployed in space in the 1980 decade. However, they require large amounts of electrical power to function and would thus need to be housed in large satellites. But in the 1990 decade, they could be deployed as part of an SPS unit. In fact, they may be deliberately placed on an SPS unit for defensive purposes.

     Not all directed energy or beam weapons are useful in space, and some are useful only for restricted targeting.

     Both types of high energy lasers (HEL)—continuous wave (CW) and pulsed—would be useful for space-to-earth targeting, but only from low earth orbits (LEO). This is because the Earth’s atmosphere acts to reduce their intensities, often by as much as a factor of 15 for some types of HEL(CW) devices. This atmospheric interaction reduces the effective range of HEL’s. Therefore, for Earth bombardment, HEL’s would have to be positioned in LEO (160 kilometers from surface of Terra) and receive their power by relay from the SPS system in geosynchronous Earth orbit (35,786 kilometers from surface of Terra). It's in the space-to-space targeting area that HEL’s become attractive as weapons. They can be used for SPS defense because they are very effective at short ranges and in the vacuum of orbit. For example, by 1990 an HEL(CW) could have the capability to produce ten megawatts of energy in a one microradian (0.00005729 degrees) beam width (last time I checked in 2020 lasers were not quite there yet). Such an HEL(CW) could produce a beam with delivered power density of three kilowatts per square centimeter at a distance of a thousand kilometers (620 miles). That ’s enough to vaporize steel in a very short period of time. Thus, HEL’s will be militarily useful for space-to-space anti-satellite attacks, for SPS self-defense against projectile weapon attack, for enforcing blockades, and as a very effective anti-ballistic missile (ABM) defense to be used against ICBM’s when they rise above the Earth’s atmosphere on their way from Earth launch to Earth target.

     Particle beam weapons (PBW’s) are somewhat more than lasers because PBW’s produce charged or uncharged subnuclear particles, whereas lasers produce beams of photon energy. PBW’s conceived and possibly built to date include neutral hydrogen, proton (H+), electron, neutron, and gamma ray units.

     PBW’s cannot be used for Earth bombardment from space. The Earth’s atmosphere interacts so strongly with all of these particle beam types that their effectiveness against ground targets is zilch.

     Only one form of PBW appears at this time to be useful for space-to-space targeting: the neutral hydrogen PBW. Proton or hydrogen PBW’s suffer from the fact that beams don’t propagate well in vacuum unless the beams are fully neutralized, and the charged nature of the proton PBW beams makes them extremely difficult to focus and aim because of the Earth’s magnetic field (the field bends the beam in unexpected directions). Neutron and gamma ray PBW’s have beam divergences that are too great for weapon use (they cannot be focused on the target) … at least with technology that can be forecast for the next quarter of a century (2006 or so).

     There are other ways to use the energy output of an SPS unit for military purposes in the sub-category of directed energy weaponry.

     Primary among these methods is the use of SPS-powered r-f transmitters for electronic warfare and electronic countermeasures.

     It’s quite unlikely that the SPS power beam itself could be used even against other satellites because of the low power density nature of the beam sub-system. With the types of SPS transmitting antennas presently planned or available, it’s extremely difficult, if not impossible, to focus the power beam sufficiently to achieve any effect against another space vehicle or facility unless the vehicle or satellite were to fly into the beam of the SPS only a few kilometers away. In that case, the spacecraft thus irradiated might become temporarily warm, but it is unlikely that a power beam operating up in the region of 2450 megaHertz could cause any damage to properly shielded internal components or circuitry.

     The only possible way that an SPS power beam could be used against a ground target such as a city would be as a psychological weapon.

     The various potential threats of military utilization of an SPS system and its various component sub-systems is summarized in Table VI for space-to-Earth threats and in Table VII for space-to-space threats.

     Table VII also has a bearing on our later discussions of the military vulnerability of the SPS system.

     It should also be obvious that the availability of technology doesn ‘t make any particular threat feasible or real, although it can make the threat perceptually real.

     And many times in warfare or even in diplomatic relations between nations, history tells us that a perceived threat or capability is often as effective as if it were real. On a personal basis, it’s sometimes called “bullying” if it’s used by an antagonist or “bluffing” if you or your friends and allies use it, especially in a poker game.

     The SPS system does have apparent military utility, but not as many people have claimed: as an incendiary space-to-Earth attack weapon. The SPS system permits many new military operations and space weapons systems to become feasible in the space environment, but the SPS is not one of those weapon systems.


     Weapon: Continuous wave high energy laser.
     Target: Terrestrial structures and vehicles.
     Period: Mid-term.
     Comments: HEL(CW) could be deployed in space by the late 1980’s. Deployment in GEO impractical due to long ranges. LEO HEL(CW) could deliver 100 times solar flux in beam 1 microradian wide, but atmospheric effects could reduce intensity by factor of 5-15.

     Weapon: Pulsed high energy laser.
     Target: Terrestrial structures and vehicles.
     Period: Near-term to Mid-term, possibly infeasible.
     Comment: Level of capability increases with time. Use in GEO probably infeasible for Earth attacks because of ranges. In late 1990s, values are 20 megawatts output, beam width 1.5 micnoradians.

     Weapon: Particle beam weapon.
     Target: Terrestrial structures and vehicles.
     Period: Infeasible
     Comment: Unlikely to be used for space-to-Earth because of effects of interaction with atmosphere.

     Weapon: Entry vehicle.
     Target: Terrestrial structures.
     Period: Near-term.
     Comment: Earth bombardment, second strike capability. Warhead not needed if large and fast enough. Capabilities increase with time.

     Weapon: SPS power beam.
     Target: Terrestrial structures.
     Period: Infeasible.
     Comment: Insufficient energy density for incendiary use.

     Weapon: SPS power beam.
     Target: People.
     Period: Far-term to infeasible.
     Comment: Possible but implausible psych war use

     Weapon: SPS power beam.
     Target: Electrical equipment.
     Period: Far-term.
     Comment: Use in jamming communications

     Weapon: SPS power beam.
     Target: Weather modification.
     Period: Infeasible.
     Comment: Requires too much power

     Weapon: SPS power beam.
     Target: Customers.
     Period: Far-term.
     Comment: Denial of power is possible

     Weapon: Radio frequency transmitter.
     Target: Radio frequency equipment.
     Period: Mid-term.
     Comment: Electronic warfare use on any frequency.

     Weapon: Radio frequency transmitter.
     Target: People.
     Period: Mid-term.
     Comment: Direct broadcast of propaganda

     Weapon: Radio frequency transmitter.
     Target: Weather modification.
     Period: Infeasible.
     Comment: Requires too much power

     Weapon: Radio frequency sensors.
     Target: Radio frequency emissions.
     Period: Mid-term.
     Comment: Electronic and signal intelligence gathering.

     Weapon: Optical/infra-red sensors.
     Target: Structures and vehicles.
     Period: Near-term.
     Comment: Reconnaissance and surveillance

     Weapon: Radars.
     Target: Structures and vehicles.
     Period: Near-term.
     Comment: Reconnaissance and surveillance

     Weapon: Radio frequency and laser communications
     Target: People
     Period: Near-term
     Comment: Military communications and control


     Weapon: Continuous wave high energy laser.
     Target: Space craft and missiles.
     Period: Near-term to mid-term.
     Comment: Level of capability increases with time. Could be deployed in space by late 1980s. Capabilities 10 megawatts and 1 microradian beam width, 3000 watts/square cm. at 1000 kilometers suitable for ASAT, ABM, self defense, blockade.

     Weapon: Pulsed high energy laser.
     Target: Space craft and missiles.
     Period: Near-term to mid-term.
     Comment: Level of capability increases with time. Electrically powered types suitable for GEO deployment because of solar electric power availability. Late 1990s: 20 megawatts output, 1.5 microradian beam width, 250 watts/square cm. at 100 km. suitable for self defense, attack nearby satellites, blockade. LEO deployment for ABM with power relay from SPS.

     Weapon: Particle beam weapon (neutral hydrogen).
     Target: Space craft and missiles.
     Period: Possible mid-term, far-tenn.
     Comment: 50-100 megawatts input required to deposit 100 calories per gram at 1000 km. SPS power relay to LEO required for ABM use.

     Weapon: Particle beam weapon (H+ or electron).
     Target: Space craft and missiles.
     Period: Infeasible.
     Comment: High intensity of less than fully neutralized beams don’t propagate well in vacuum. Geomagnetic anomalies make focus and aim difficult.

     Weapon: Particle beam weapon (neutron or gamma ray).
     Target: Space craft and missiles.
     Period: Infeasible.
     Comment: Beam divergence too great.

     Weapon: Orbital interceptors.
     Target: Space craft.
     Period: Near-term.
     Comment: In development. Space torpedoes or mines. Nuclear or conventional warheads.

     Weapon: Nuclear detonations.
     Target: Space craft.
     Period: Near-term.
     Comment: Weapons exist if deployed. May destroy attacker’s systems by electromagnetic pulse.

     Weapon: SPS space transportation vehicles.
     Target: Space craft and non-specific.
     Period: Near-term.
     Comment: ASAT carrier. Support, shelter, logisitics.

     Weapon: SPS power beam.
     Target: Space craft and missiles.
     Period: Far-term.
     Comment: Insufficient power for physical damage against even moderately shielded targets at close range. Electronic warfare use possible.

     Weapon: Radio frequency transmitter.
     Target: Space craft.
     Period: Far-term.
     Comment: Electronic warfare only.

     Weapon: Radio frequency sensors.
     Target: Space craft and radio frequency emissions.
     Period: Near-term.
     Comment: Electronic intelligence, capability depends on receiver sensitivity at given frequency and signal processing ability.

     Weapon: Optical and infra-red sensors.
     Target: Space craft.
     Period: Near-term.
     Comment: Reconnaissance and surveillance.

     Weapon: Radar
     Target: Space craft.
     Period: Near-term.
     Comment: Reconnaissance and surveillance, tracking.

     Weapon: Radio frequency and laser communication.
     Target: Space craft.
     Period: Near-term.
     Comment: Military communications and control.

     Weapon: LEO and GEO Bases.
     Target: Non-specific.
     Period: Mid-term.
     Comment: Usage as shelter, logistic support.

     Weapon: Space facilities for CBW.
     Target: People.
     Period: Mid-term but may be infeasible.
     Comment: Chemical and biological warfare (CBW) facilities in separate modules to permit isolation and secrecy. May not offer advantages over Earth-based facilities.

     Weapon: Deep Space Freighter.
     Target: Space craft.
     Period: Mid-term but may be infeasible.
     Comment: Inspection, but long-range sensors on space facilities may accomplish all goals at lower cost and risk.

     Weapon: Deep Space Freighter.
     Target: Space craft.
     Period: Mid-term, but may be infeasible.
     Comment: Used for satnap and satmute, but booby traps and satellite self defense could make use too risky.


     Weapon: Continuous-wave high energy laser.
     Target: Space craft.
     Period: Near-tenn & Mid-term.
     Comment: Level of capability increases with time. For the late 1980s. A plausible HEL(CW) is a chemical laser, 10 megawatt output, 4 meter mirror, beam width 1.5 microrads.

     Weapon: Pulsed high energy laser.
     Target: Space craft.
     Period: Near-term and Mid-term.
     Comment: Level of capability increases with time. For the late 1980s, a plausible HEL(P) is a closed cycle carbon dioxide electrodynamic laser with 10 megawatts output, 4 meter mirror, beam width 3.5 microrads, rep rate a function of target characteristics and range.

     Weapon: Particle beam weapon.
     Target: Space craft.
     Period: Infeasible.
     Comment: Neutral or pulsed charged beam considered infeasible because Earth’s atmosphere interactions prevent ground-to-space or space-to-ground use.

     Weapon: Orbital interceptor (ASAT)
     Target: Space craft.
     Period: Near-term.
     Comment: Under development in USA. Conventional or nuclear warhead.

     Weapon: SPS pilot beam.
     Target: SPS
     Period: Far-term or infeasible.
     Comment: Used as covert communications relay to other military space facilities, probably infeasible because cheaper and more effective means exist.

     Weapon: Radio frequency transmitter.
     Target: SPS
     Period: Far-term or infeasible.
     Comment: Used to jam the pilot beam, but feasibility depends upon design of pilot beam steering equipment.

     Weapon: SPS space transportation system.
     Target: Non-specific.
     Period: Near-term.
     Comment: Used for transportation of men and equipment including ASAT weapons.

     Weapon: Launch sites.
     Target: Non-specific.
     Period: Infeasible.
     Comment: Not a threat because facilities can be used for military and commercial purposes.

From SPACE POWER by G. Harry Stine (1981)

“You’re Liiriani, yes?” The recruiter eyed the tattered uniforms on those crowding into his prefab. “Ex-military. Wait… you’re Temple Guard? The ones left behind after the fall of Mantaniir?”

“Yeah. I was at Mantaniir. We all were.” The scarred veteran’s lip curled, and he spat. “Proud Mantaniir. Glorious Mantaniir. Mantaniir the Unfallen, Guardian of the Holies, all of that. Well, it didn’t fall, or we’d be dead. It was swept aside like it was nothing.”

“The first day could have been the last day. We —“

…were prepared, we were ready, we were the last line of defense for Iliir itself, and we knew they were coming at dawn. They’d told us that much. But we heard nothing. Saw nothing. Not until dawn.

We’d never fought a space war before. No-one understood what it meant that we’d lost the high orbitals. Not until the k-rods started falling, and then it was too late to help us. The minefields down-valley went in the first wave — to give us time to see what was killing us. The flak towers went in the next, along with communications and sensors. Then they started drunkwalking their shots around the valley, blasting walls, barracks, everything left of the fortress flat. What was left of us had run for the bunkers by then, and down through them into the deep tunnels. Couldn’t so much as get a shot off. We were down there for days — any time someone made a run for it, or poked so much as a nose-tip above ground, they dropped a k-rod on them. We had no power — if any generators started up, that bunker got a k-rod within minutes. Just hiding in the dark.

And then the machines hit us, wolves and spiders. From both sides — we heard later that their stormtroopers bypassed us and dropped on Iliir directly. Wolves, the little ones, ‘bots that run in packs, wall, ceiling, or floor, see in the dark, spit bullets or tear a man’s leg off themselves. And then the spiders, big eight-legged bastards with fire and cutting torches and rockets. All howling to each other like the gods below. And they wouldn’t die! Enough explosive might stop one, but if it wasn’t torn apart, it’d fix itself — or the rest of them would — and come after you again.

So we surrendered. The spiders herded us outside again, up among the craters, and fenced us in with electrowire. A couple of us tried to make a break for it. They didn’t get past the perimeter. Spiders didn’t care — they just sat there watching us, day and night. A couple of days later, one of their armor boys came by to look us over, and left us a crate of rat-bars and a medkit. Then he left us there with just the spiders to watch us. That was the only enemy we saw in the entire battle.

Two weeks later, we got word that the war was over, the Council had been captured, surrendered, were killed, one of those. The spiders all marched back into a shuttle and left us alone, then, so we scavenged what we could, tried to stay alive. A week after that, the new Council had all of us who’d let Iliir fall through our ‘heretical incompetence’ shoved aboard an old ore freighter and dumped us on this craphole planet.

“— are what’s left of the Liirian Temple Guard, yeah. Seventh Fist Ileer, commanding. And me an’ the boys’ll fight for you. Nothing else left for us now. But only if we’re fighting men. Nothing that don’t bleed and won’t die.”

— Sagivv’s Company recruitment interview, Márch, eight months after the Liir Conflict


The entire cost analysis raises the question of the alternative to invasion.  The basic strategy is to destroy the planet’s orbital defense and force the defender to surrender under threat of bombardment.  If the defender refuses, the attacker can land forces with impunity and support them with orbital bombardment.  The options for bombardment are the same as for normal space warfare: lasers and kinetics.

Lasers have a number of excellent qualities for attacking surface targets.  First, they respond at the speed of light, so troops on the ground don’t have to wait very long for fire support, and any potential target can’t move out of the way.  Second, their accuracy is very good, which is useful when attacking targets that are in a populated area.  However, lasers also have their drawbacks.  First and foremost, the atmosphere absorbs frequencies above the visible spectrum quite effectively, preventing lasers operating in those frequencies from attacking surface targets.  As such frequencies are the most efficient for attacking other spacecraft, it is entirely possible that specialized bombardment craft would be required.  While some lasers (such as FELs) can alter their frequency, the same does not apply to the optics involved, making such capability superfluous.  Secondly, the laser is a line-of-sight weapon, and is affected by the distance it must travel, both in total and through the atmosphere.  This sets tradeoffs between accuracy and time on station.  A laserstars in low orbit will obviously have the smallest spot sizes and best pointing accuracy, but it only sees the target for a few minutes on each pass.  Even when it can see the target, its low altitude means that for a significant portion of its orbit it will be shooting through a lot of the atmosphere.  Furthermore, the planet’s rotation will ensure that the next pass will have a groundtrack well away from the target (unless it is located on the equator or at the poles), which limits availability to a pass or two a day.  

Higher altitudes have lower accuracy due to increased range, but greater availability per pass, thanks to the higher angle.  Moreover, the orbit can be made elliptical, which ensures that more of the orbit can be spent over the target.  The theoretical optimum, ignoring the effects of range, is a geostationary orbit, which keeps the ship directly over the area of interest.  The angle of fire through the atmosphere is a potential problem when shooting at higher latitudes.  This can be partially solved through the use of Molniya orbits, which give improved coverage in such areas.  Targets near the pole do not suffer the normal problems of groundtrack movement, as the target is close to the groundtrack no matter what.

The use of multiple laser platforms can solve many of these problems, and the question then becomes finding the balance between coverage and the minimum number of platforms.  As a first approximation, somewhere between 12 and 24 bombardment platforms will be required for constant global coverage, although less could be used if stationed in very high orbit.  However, coverage itself might not be sufficient, particularly in hotly-contested areas, where multiple platforms would likely be required at all times.  Significant study has already been done in this area (although done with respect to missile defense instead of planetary bombardment, many of the underlying principles apply) and the author will not investigate that topic further.

Before a discussion of kinetic bombardment, a basic treatment of the projectiles used (orbit-to-surface kinetics, or OSKs) is in order.  A general rule for OSKs is that the area density will need to be at least 10 tons/m (strictly speaking, the area density needs to be at least that of the atmosphere of the target body, and the numbers given are for Earth).  If the area density is below this threshold, the object will reach the ground at low velocity, while objects with area densities higher than 10 tons/m2 will still be moving quickly at impact, making them potential weapons.  To put that into perspective, an OSK made of iron will need to be about 1.27 m long to achieve the required area density (independent of diameter) while one made of tungsten will only need to be .52 m long.  This length in turn sets the minimum feasible diameter to avoid buckling, and ratios of 20 or 30 to 1 are probably feasible, giving a minimum mass on the order of 5 kg for the tungsten rod and 14 kg for the iron.  Buckling is unlikely to be a design driver, however, as a shape with a flared base is more stable on entry.  A larger OSK will, all else being equal, be more efficient than a smaller one, retaining more of its mass and velocity on impact.

Another potentially serious problem is entry heating.  An OSK depends upon retaining as much of its velocity as possible, which in turn means that it will be receiving large heat loads when it is low in the atmosphere.  When dealing with the heat loads present in OSKs, ablation will occur, and the projectile must be carefully designed to avoid having said ablation destroy its aerodynamic characteristics.  This problem could also occur if the projectile was damaged, which would ease the problem of surface defense.  If the projectile successfully impacts the target, it will tend to penetrate and bury itself in the target, limiting damage to the surrounding area.  In fact, this effect has been compared to a shaped charge.

All of the above applies mostly to OSKs that are long in proportion to their diameter.  If the projectile is instead about equal in length and diameter, it will tend to produce a crater and do more damage to the surrounding area.  The problem, however, is that this requires a large projectile.  For tungsten, the OSK will need to mass approximately 2.7 tons for cratering to occur, while an iron projectile will need to be 16.1 tons and a typical rocky projectile (3 g/cc) will be about 110 tons.  It should be noted that even for cratering kinetics, the damage is still downwards and outwards, which is not optimal for area effects such as attacking troops.  

It appears that the best way to achieve area effects with OSKs is to intentionally break up the OSK near the ground, producing something akin to a meteor airburst.  The best-known example of this phenomena is the Tunguska Event of 1908, but similar meteor “explosions” occur frequently.  The Chelyabinsk Meteor in February of 2013 is another excellent example of a projectile producing bomb-like effects when it breaks up, although it was much larger than would be practical for military use.  What occurs is that the sudden transition from a single, low-drag object to a large number of small, high-drag objects dumps a large amount of energy into the atmosphere in the form of heat, which produces effects akin to an explosion.  The exact form and magnitude of this effect is uncertain, but it appears that a fireball would be formed and would continue on the course of the OSK.  There would also be some blast, but the exact dynamics of the outcome are currently unknown to the author.  Either the blast or the fireball would be useful against area targets such as troops or light vehicles, which traditional OSKs are largely ineffective against.

While the OSK is in the lower atmosphere, it will be sheathed in plasma due to its velocity.  This prevents both the use of onboard sensors and communication with the outside world (although there have been suggestions that communications could be made possible).  This renders traditional OSKs useless against maneuvering targets, as they are, at best, inertially guided for the last few minutes of their flights.  It is possible that the plasma sheathe will provide protection against lasers, but the magnitude of the effect is unknown.

This raises another option, an OSK that intentionally dumps most of its energy and finishes its flight at only 2 km/s or so.  This actually increases penetration, and allows guided projectiles to be used.  Some form of heat shield would be required, but that is a fairly simple matter to build.  This sort of kinetic would be useful against targets like tanks, particularly if deployed from an “Orbital Death Pod” of some sort.  Other types of conventional munitions could also be carried in the ODPs, such as cluster munitions, nuclear weapons (although most OSK research is based on ICBM RVs) or even autonomous UAVs.  The main drawback to this type of OSK is that it is somewhat more vulnerable to planetary defenses, as it sheds most of its speed before impact, which potentially puts it in the kill envelope of many SAMs.  They are, however, less vulnerable than manned drop pods, as they can decelerate much more quickly, and thus hold their velocity lower in the atmosphere.

The deployment of OSKs is subject to some of the same constraints of orbital mechanics as are laser bombardment platforms, but there are significant differences in the effects of said constraints.  First off, OSKs, unlike lasers, do not have instant response times.  Times as low as 12 minutes have been cited, but these require large numbers (40-150) of satellites in low orbit to achieve continuous coverage, and the projectiles will enter the atmosphere at low velocity, reducing lethality.    A requirement for continuous coverage obviously does not apply for strategic bombardment, but it does suggest that small sub-busses might be used for ground support.  If the launching platform is at an altitude of 6000 km, the flight time will be approximately 75 minutes, while a geostationary launcher will have a flight time of about 12 hours, although these can be reduced somewhat with more delta-V.  The delta-V requirements for deployment vary significantly, depending on range and entry angle.  A high entry angle is desirable, to minimize the distance traversed in the lower atmosphere, but requires more delta-V than a shallow trajectory.  

Crossrange is another serious concern, and would require yet more delta-V.  The exact magnitudes involved vary significantly with the initial orbit and the time between launch and impact.  See Appendix B of Space Weapons, Earth Wars for more details.

All of this suggests that large rail/coilguns might be the weapons of choice for general planetary bombardment, massive concentrations of projectiles might not be necessary and the savings over missiles could be substantial.  The delta-V requirements (generally somewhere between 10 and 15 km/s) are well within the capabilities of coilguns, and the logistics advantages would be substantial.

The tactics required to neutralize planetary defenses (see Section 4) will vary based on the type of defense.  While a number of systems are fixed, and thus can be dealt with via massive firepower, mobile systems are a much tougher target to handle.  Hunting mobile targets is quite likely the only place where any sort of ground forces have a place.  These would be small teams, similar to the LRRPs (Long Range Reconnaissance Patrols) of Vietnam, tasked with locating hidden missile launchers (likely the truck-mounted missiles discussed in Section 4) and reporting their location to the bombardment forces.  It has been suggested that these teams instead be used to attack the launchers directly, but there are three major drawbacks to this.  The first is that the logistics burden of moving people is significantly higher than that of moving kinetics, and lasers have very low logistical requirements.  Even with low casualty rates, the mass economy of this strategy is dubious in the extreme.  Secondly, even if the mass efficiency is slightly better, the fact that human casualties are part of this scheme is likely to doom it.  Lastly, it is impossible to directly tell what gave a position away from a kinetic strike, but a ground raid is quite obvious.  The countermeasure is thus to move hunter-killer teams to the area and guard the other launchers.  If a kinetic strike takes out a platform, the defender has to decide between looking for LRRPs (or UGVs), looking for UAVs, putting more camouflage up, trying for better indirect camouflage (operational patterns and radio discipline, for instance), or hunting for spies.  It should be noted, however, that such teams more or less require low-orbit fire support, given the time lag in kinetic drops from high orbit.  

There might be an occasional target that cannot be killed directly from orbit, but there are several ways of dealing with such targets.  One possibility is a weapon similar to the W54Davy Crocket” atomic rocket launcher of the Cold War.  This has the advantage of operating outside the envelope of most defensive systems deployed against orbital attack.  The team operating it would still have the difficult task of getting it in place and getting away, but the chances of doing so are probably fairly good.  Another option is a cruise missile dropped well away from the defenses, which then flies in on its own.  Some versions of the Tomahawk cruise missile have ranges as long as 2,500 km, while the AGM-129 ACM has a range of 3,700 km.  These are significantly larger than the danger zone of even long-range SOMs, giving the missile more or less free entry into the atmosphere.  The warhead could be either nuclear or conventional, as required by the nature of the target.  Such missiles would remain vulnerable to air defenses, but their small size, relatively low cost, and lack of need to return to orbit make them an attractive proposition.  It has also been suggested that commando teams could be used directly against certain strategic targets, generally command and control, but the ease with which these can be defended against such attacks makes them a dubious proposition compared to orbital or remote bombardment.

Redirected asteroids are often proposed as a means of attacking planetary targets.  The usual logic goes that they are “free” and thus the cheap way of destroying a planet.  From a military point of view, however, asteroids are nearly useless.  First off, small asteroids are not suitable for use in this manner.  While purpose-built kinetics can be used to hit targets with minimal collateral damage, any natural asteroid of comparable size will either slow down to the point of uselessness or disintegrate in the upper atmosphere.  Larger asteroids (>1 km) are useless except for ecocide.  While this might occasionally be the goal, it falls outside the scope of this paper.  A medium-sized asteroid, such as the aforementioned Chelyabinsk Meteor, might have some uses, but it would be unreliable, and difficult to use, as that meteor is estimated to have mass 11,000 tons.  The damage mechanism would be the same as that proposed above for airbust kinetics, except for a lack of precise control and a much higher lower size limit.  (Oddly enough, when RAND studied this issue for Space Weapons, Earth Wars, they noted the use of asteroids for airbust, but neglected to apply it to man-made kinetics.)

The biggest problem with asteroids is their ease of use relative to nuclear weapons.  Hauling an asteroid from the belt is quite difficult, and truly silly.  More plausibly, there are a significant number of earth-crossing asteroids which might be suitable for this use.  The number available (and thus the minimum lag time) is based upon the amount of delta-V that can be applied, and when.  For example, 10-meter iron asteroids (about the minimum size that can be considered as a useful weapon) hit the Earth about 3 times a century.  If one is diverted that passes within 1.35 light-seconds (the distance of the moon), there are about two a week available.  Larger objects will pass by less often, although stony asteroids become viable weapons as the size increases.  These types of asteroids probably have windows of a few months.  Particularly in the case of smaller asteroids, the primary delay driver will be the diversion process.

The diversion itself will not take that long.  With a few months lead time, the delta-V required is generally in the tens or hundreds of m/s, which given projected mass driver technology would involve the use of 30% of the object as remass at the upper end.  The power requirements will likely force this acceleration to be made over a fairly long period, pushing the lag even higher.  If the asteroid is diverted later, the delta-V requirements skyrocket.  At one month out, 1 km/s is passed, at which point about half of the asteroid is being used as remass.

The time lag is the greatest drawback to the use of asteroids for any sort of bombardment.  Assuming that the defender is somewhere near technological parity, he will be able to deflect away any asteroid you can send towards him given enough time.  Depending on the exact nature of the asteroid in question, the time he has available could vary significantly.  If the incoming asteroid is intended to take out a city, even a small deflection quite late would send it over rural or uninhabited territory, greatly reducing damage.  This forces the attacker to guard the asteroid for months while it is moved into position, and the logistics costs of doing so are quite high.  There is a significant economy of scale in bigger asteroids, however.  They require the same protection as the smaller ones, and the cost scaling of the mass driver will be negligible compared to the cost of the naval forces deployed to protect it.  Furthermore, the asteroid itself cannot be deflected as easily at the last instant, either through a last-ditch effort to break through the fleet guarding it or after the fleet has pulled off to avoid following it into the atmosphere.

The above concepts are often associated with the name ‘Project Thor’, which is believed to be the Air Force’s original study of the idea of orbital bombardment.  However, the author has found no reason to believe this to be the case.  There was an official Project Thor, but it was a study of fragmentation ballistics, and had nothing to do with orbital bombardment.  Moreover, research has been unable to turn up any official studies of orbital kinetic bombardment that are above the level of that done in Space Weapons, Earth Wars.  The name Project Thor appears to have originated with Jerry Pournelle, who thought of the concept while working in operations research, and appears to have popularized the term.  The author believes it was his personal term, and in no way official.

The primary alternative for destroying strategic ground targets is nuclear weapons.  The cost of a comparable nuclear weapon is almost certain to be no greater than that of the asteroid-deflection operation, particularly when the fleet operations costs are factored in, and depending on the technologies involved, it is very likely to be significantly less.  The nuclear weapons are also more accurate and predictable, and have none of the lag problems associated with asteroids.  The only area where an asteroid wins over a nuclear weapon is in dealing with terminal defenses.  While a nuclear weapon (which would almost certainly resemble an ICBM RV) can be engaged and destroyed by ABM-class weapons, an asteroid would be virtually unaffected by any defenses after it entered the atmosphere.  A nuclear weapon fired at it might be able to disrupt it and cause it to dump its energy high in the atmosphere, but that might still have serious climatic effects, as well as the possibility of some damage on the surface, and the damage done by the nuclear weapon itself.

All in all, the disadvantages in redirecting even NEOs are likely to outweigh any possible cost advantages.  The only practical reason to do so might be for purposes of psychological effects.  The defenders would know exactly how difficult it is to use an asteroid as a weapon, and the fact that it was done anyway would send a very clear message.  Another vaguely possible cause would be a total ban on the use of nuclear weapons, but given that such a ban shows no signs of happening today, and would be next to impossible to enforce, and that nuclear-electric drives are assumed throughout this paper, this is unlikely.  As Space Weapons, Earth Wars put it: “Because much cheaper, more responsive weapons of mass destruction are readily available, this one is likely to remain safely in the realm of science fiction.”  For a more irreverent treatment of the issue, Google “Rocks are not free”.

A related issue that deserves a brief mention is the use of spacecraft as weapons against ground targets.  This is unlikely, to say the least.  As mentioned above, a sectional density of 10 tons/m2 is required to make it through the atmosphere with a reasonable amount of velocity remaining.  While common ships might reach this threshold, they are almost certain to fail structurally long before impact.  When they break up, the pieces are unlikely to retain sufficient sectional density to reach the ground.  The result is a high-altitude airburst, which, given expected vessel sizes, is unlikely to do significant damage.  It has even been suggested that vessels be intentionally designed to break up on atmospheric entry to reduce the risk to people on the ground.  Even if the ship was theoretically capable of doing damage to ground targets, there still remains the issue of actually hitting the target, and the prospects on that front are dubious at best.

The basic strategy of the attacker during a planetary invasion is to destroy enough of the surface defenses by bombardment to be able to dictate terms to the defender, or support troops should that be necessary.  The mechanism by which to do this is more or less that of moving into range and dueling with them.  This in turn reveals the locations of the fixed defenses, and forces the mobile ones to either fire their missiles (which then renders them ineffective for the rest of the siege) or risk revealing their location.  The weapons can be forced to fire to protect targets on the ground, as the spacecraft will have to fight them instead of conducting its bombardment mission.  The attacker would continue to do so until he had reduced the defenses to a point that he could seriously consider landing troops. This would not be the point at which all of the defenses had been eliminated, but the point at which the attacker could provide cover for a landing from his fleet, and do so with confidence that he could protect both his fleet and the drop pods.

Before the actual landing, the attacker would probably call the defenders and offer good terms for them if they were to surrender at this time, and tell them that the terms would become much worse if the landing went through.  Most defenders would probably surrender at this time, as they can no longer expect to resist with hope of long-term success.  If they refuse, they either consider death better than capitulation, or believe that they can defeat the landing.  At this juncture, a reputation for honesty and honor would greatly help the attacker.  Conversely, if the defender waits until the attacker begins to land and opens fire, the attacker will probably show no mercy and destroy the defender’s cities.  This holds the leaders hostage to the people, ensuring they go through with their side of the bargain.

It has been suggested that in some cases, the attackers cannot offer terms, primarily due to unreasonable political leadership.  This situation is outside the scope of this paper, but the other side of the same problem, an unreasonable defender, is not.  In this case, clearing as much of the orbital defenses as possible is vital, so that the ground troops can have access to continuous space support.  This should serve as a massive force multiplier, allowing a reasonable amount of troops to capture the world.  Occupation is likely to be a much bigger problem, but it is one that lies outside the scope of this paper.

by Byron Coffey (2016)

(ed note: this game is a sequel to the tabletop game StarForce: Alpha Centauri. Due to the odd background universe, literally the only valuable thing a planet has to offer is the colonists. Therefore in the game StarSoldier, the soldiers have to avoid causing civilian casualties at all costs.)

"Teleships" are starships, their faster-than-light movement is called "shifting". A "StarGate" is a sort of orbital fortress defending the planet from invading Teleships. The "Heissen Field" is a weapon that allows starships in orbit to render everybody on the planet unconsious. Everybody that is unprotected, defending StarSoldiers are unaffected.)



Undisputed control of local space is a doctrinal prerequisite to any attempt by a StarForce to induce a Heissen Field and land StarSoldiers on an unfriendly planet. It is therefore usually the case that only one side—the side attacking, in the strategic sense—that will be able to call upon off-surface support. And being extremely destructive, Orbital Ground Support is only utilized in extreme circumstances. In any event, the provision of support bombardment by even "unopposed" StarForces is somewhat problematic, as the presence of automated and StarSoldier manned defensive missile batteries and laser banks on the surface of the planet has the capacity to make things difficult for orbiting Teleships. A StarForce may not move or defend itself telesthetically within the proximity of the gravity fields which characterize solar systems, and so is dependent upon "conventional" kinetic drive (Energy Modulation Packs) and computer-directed laser interception for those tasks. Faced with a powerful surface defense utilized to capacity, Teleships generally adopt variable geometary orbits, which allow them to approach closely to the planet for brief and unpredictable passes. At least two StarForces (eight TeleShips) are required to provide effective ground support under such circumstances.


The rest of the city seemed to have died of neglect rather than violence. It certainly hadn't been bombed out. Harkaman thought most of the fighting had been done with subneutron bombs or Omega-ray bombs, that killed the people without damaging the real estate. Or bio-weapons; a man-made plague that had gotten out of control and all but depopulated the planet.

From SPACE VIKING by H. Beam Piper (1962)

The Gravity Gauge

This is sort of the outer space equivalent of holding the high ground.

Two people throwing rocks at each other is pretty much a fair fight. If one person is on a hill, they have an advantage. And if one person is at the bottom of a well, that's not fair at all. By analogy, it is beyond unfair if one person is in orbit. The lucky one in orbit does not need to use bullets, missiles or nuclear weapons; a nice selection of rocks and boulders will do. Nudge a rock hard enough to de-orbit it, and it will strike with most of the kinetic energy difference between orbit and the ground. The poor slob on the ground, however, has to use huge rockets just to boost weapons up to the level of orbital person. This is called the gravity gauge.

Please note that "unfair" does NOT mean "impossible".


     "Have you ever wondered why the Patrol consists of nothing but officers—and student officers, cadets?"
     "Mmm, no, sir."
     "Naturally you wouldn't. We never wonder at what we grow up with. Strictly speaking, the Patrol is not a military organization at all."
     "I know, I know—you are trained to use weapons, you are under orders, you wear a uniform. But your purpose is not to fight, but to prevent fighting, by every possible means. The Patrol is not a fighting organization; it is the repository of weapons too dangerous to entrust to military men.
     "With the development last century of mass-destruction weapons, warfare became all offense and no defense, speaking broadly. A nation could launch a horrific attack but it could not even protect its own rocket bases. Then space travel came along.
     "The spaceship is the perfect answer in a military sense to the atom bomb, and to germ warfare and weather warfare. It can deliver an attack that can't be stopped—and it is utterly impossible to attack that spaceship from the surface of a planet."
     Matt nodded. "The gravity gauge."
     "Yes, the gravity gauge. Men on the surface of a planet are as helpless against men in spaceships as a man would be trying to conduct a rock-throwing fight from the bottom of a well. The man at the top of the well has gravity working for him.
     "We might have ended up with the tightest, most nearly unbreakable tyranny the world has ever seen. But the human race got a couple of lucky breaks and it didn't work out that way. It's the business of the Patrol to see that it stays lucky.
     "But the Patrol can't drop an atom bomb simply because some pipsqueak Hitler has made a power grab and might some day, when he has time enough, build spaceships and mass-destruction weapons. The power is too great, too awkward—it's like trying to keep order in a nursery with a loaded gun instead of a switch.
     "The space marines are the Patrol's switch."

(ed note: of course the gravity gauge isn't quite as much of a problem when the planetary defenses include huge laser weapons. Lasers had not been invented yet when the novel was written. But as Heinlein observes below, lasers are pretty worthless if you are being bombarded by house-sized bolders.)

From SPACE CADET by Robert Heinlein (1948)


Back in the 1950s, Robert Heinlein and others made a rather startling observation:

Robert Heinlein 1950
The most important military fact of this century is that there is no way to repel an attack from outer space.
General Thayer: The reason is quite simple. We are not the only ones who know that the Moon can be reached. We're not the only ones who are planning to go there. The race is on — and we'd better win it, because there is absolutely no way to stop an attack from outer space. The first country that can use the Moon for the launching of missiles… will control the Earth. That, gentlemen, is the most important military fact of this century.
Robert Heinlein 1965
I flatly stand by this one. True, we are now working on Nike-Zeus and Nike-X and related systems and plan to spend billions on such systems—and we know that others are doing the same thing. True, it is possible to hit an object in orbit or trajectory. Nevertheless this prediction is as safe as predicting tomorrow's sunrise. Anti-aircraft fire never stopped air attacks; it simply made them expensive. The disadvantage in being at the bottom of a deep "gravity well" is very great; gravity gauge will be as crucial in the coming years as wind gauge was in the days when sailing ships controlled empires. The nation that controls the Moon will control the Earth—but no one seems willing these days to speak that nasty fact out loud.
Robert Heinlein 1980
I have just heard a convincing report that the USSR has developed lasers far better than ours that can blind our eyes-in-the-sky satellites and, presumably, destroy our ICBMs in flight. Stipulate that this rumor is true: It does not change my 1950 assertion one iota. Missiles tossed from the Moon to the Earth need not be H-bombs or any sort of bomb—or even missile-shaped. All they need be is massive… because they arrive at approximately seven miles per second. A laser capable of blinding a satellite and of disabling an ICBM to the point where it can't explode would need to be orders of magnitude more powerful in order to volatilize a house-size chunk of Luna. For further details see my THE MOON IS A HARSH MISTRESS.

However, it might not be quite as bad as Heinlein thought.

Orbiting a string of nuclear weapons aimed at Earth would be an easy way of conquering the world. Or a Lunar missile base. This was why it was outlawed in the SALT II treaty of 1979. Robert Heinlein wrote about this in his novel Space Cadet and the short story "The Long Watch".

Or maybe it wasn't such a good idea in the first place. The blog Tales Of Future Past points out that neither the Moon nor Earth orbital bases turned out to offer any sort of advantage over surface-based missiles. Lunar bases are easy to target, require missiles with huge amounts of delta-V to deliver the nuclear weapon to the target on Earth, and will take days of transit time. Orbital bombs have utterly predictable orbits and can be seen by everybody (unlike ground based missiles), can only be sent to their target at infrequent intervals (unlike ground based missiles), and will require a deorbiting rocket with pretty much the same delta-V as a ground base missile. So what is the advantage? Please note that not all of these drawbacks apply to enemy spacecraft laying siege to Terra.

Attacking spacecraft dropping nuclear weapons would be somewhat like the situation faced by nations threatened by enemy intercontinental ballistic missiles except that in this case the weapons have no boost phase. The discredited Strategic Defense Initiative had all sorts of ideas of how to deal with the problem. For our purposes, ignore any solution that depends upon the boost phase (since there isn't any), space-based programs are "orbital fortresses", and ground-based programs are "planetary fortresses".

Rick Robinson is of the opinion that the gravity gauge is not quite as one-sided as it appears. In an essay entitled Space Warfare I - The Gravity Well he makes his case. The main point is that the orbiting invading spacecraft have nowhere to hide, while the defending ground units can hide in the underbrush.


(ed note: Ah, Luke Campbell points out that I'm wrong, there will be a boost phase.)

Another detail — munitions will have a boost phase, otherwise they will just end up drifting next to the spacecraft that released them. So either the spacecraft boosts the munition using a gun or cannon or coilgun or something that can impart enough delta-V to de-orbit it, or the munition de-orbits itself in a similar fashion using a rocket.


One of the great arguments for selling the space programme to the American People was that if they didn't conquer space, then someone else would and that someone would use space to start lobbing atomic bombs back at the Free World. Collier's magazine ran a major series on World War III that warned of the danger of Soviet missile bases on the Moon attacking a defenceless Earth, and the film Destination Moon claimed that the Moon had to be conquered because the nation that controls the Moon controls the world.

It wasn't just speculation either. Back in the 1950s, the prospect of an atomic Pearl Harbour from space was taken seriously by the Eisenhower administration and was one of the reasons why the launch of Sputnik in 1957 was so harrowing. It wasn't just that the Soviets had stolen a march on the West, but that they might have gained the nuclear high ground first.

At first glance, the idea of space-based weapons, whether on the Moon or in Earth orbit, seems logical enough. The bomber had revolutionised warfare; allowing armies to launch assaults out of sight of one another and made cities vulnerable to massive attacks. Space, by extension, should provide an even greater advantage. Weapons could be set above their targets indefinitely and attacking one's enemy would be like dropping stones down a well. By contrast, attacking an orbital or lunar base would require fighting against the full force of the Earth's gravity and the vagaries of the weather.

Fortunately, neither the Moon nor Earth orbital bases turned out to offer any sort of advantage over surface-based missiles, which could strike targets quickly and accurately from silos or submarines yet were easily protected or hidden. Moon bases, on the other hand, were easily targeted, required very large rockets to deliver their bombs with any speed, and an attack took many hours or even days to execute. Orbital bombs were just as bad. Low orbiting bombs only passed over their targets occasionally and predictably, and being over target in a satellite is not like being in a bomber. The bomb still had to be got to Earth and that meant either a rocket engine as large as that of a surface-based missile or having your bomb spiral gently in with all the delays and problems that involves.

By 1967, the military of the superpowers had reached the conclusion that though space might be ideal for reconnaissance and communication, it was a dud as a staging area for nuclear attack and a treaty was signed banning nuclear weapons from a place where no one wanted to put them anyway; rendering the opening space scenes of 2001: a Space Odyssey with its orbital bombs obsolete before the prints even came back from the chemists.


When the interstellar rocket comes of age someone will fly to the moon. Who will be first? Will the return trip be an attack on the United States? A scientist describes how possible that may be

     The idea that someday we will find a way to bridge the gulf between the earth and the planets has fascinated men for centuries. The moon in particular, since it is much the nearest, has been the object of innumerable fictional expeditions into space. Most of them have been incredible romances but a few have that semblance to scientific basis in fact.

     Of all the contrivances devised for leaving the surface of the earth there is only one that holds real promise for space flight——the rocket. The balloon and airplane must depend upon the atmosphere for flight but the natural medium for the rocket is a vacuum. Generally regarded as little more than toys before World War II. government research has developed rockets that have attained elevations of more than a hundred miles. Yet each fresh triumph seems merely a preliminary step toward the main goal. Nothing will ever satisfy us short of getting to the moon.

     Now a new. more advanced sort of interplanetary project is being proposed, one that might be described as a moon rocket working in reverse. It is to begin where the moon rocket will leave off: in it a rocket aimed at the earth will leave the moon. Admitting that the idea sounds fantastic. we must also admit that the atomic bomb and radar contact with the moon would have sounded equally fantastic twenty years ago. Perhaps we should at least take the trouble to see what lies behind this idea of a “moon-to-earth rocket."

     Once you start thinking about the moon realistically. as if it were a subdivision over in the next county, it will soon begin to dawn on you that this could be the world"s ideal military base. Certainly, when space travel comes into being, the first nation to gain control of the moon will be able to control the earth; for it will have a powerful ally in the force of gravitation.

     The mass of the moon is so small in proportion to its size that gravity upon its surface is only one sixth of what it is on the earth. In other words, objects on the moon weigh only one sixth as much as they weigh here. They would feel one sixth as heavy to us. A sack of cement guaranteed to tip the scales at 60 pounds in Chicago would register barely ten pounds in the crater Plato. A man transported to the moon would feel like Hercules. easily able to toss about huge rocks he could barely lift back home in Vermont.

     Similarly, explosives and propellants would have far more power on the moon, owing to the sixfold decrease in gravity. In an artillery duel between planets the advantage would be all on the side having the lower surface gravity to cope with. Shooting at the earth from the moon would be like throwing rocks downhill.

     Assume that a nation hostile to the United States secretly launches upon an all-out program of rocket research. Eventually it gains technical knowledge far surpassing others in this field. (This is what happened in Germany about 1935 when the Nazis began experimenting with a rocket similar to the V-2. When the first V-2s struck England in September, I944, the Allies were incapable of retaliating.) Soon it is busy producing rockets capable of sustained flights at altitudes of hundreds and thousands of miles.

     Finally after many failures comes the supreme achievement. Some experts take a rocket all the way to the moon, effect a landing, and live to make the return trip to earth. Now military work goes ahead with a rush. In an incredibly short time a base is established upon the moon. with its own power plant, fully equipped to manufacture all the weapons needed for the conquest of the earth.

     Whether such a daring project is ten or ten thousand years in the future, there is today nothing, from the purely scientific standpoint, to prevent our launching a rocket at the earth from the moon. The formulas expressing the laws of flight through space are no military secret. Positions of the earth and the moon are calculated a year in advance by the U.S. Naval Observatory and published in the American Ephemeris and Nautical Almanac. Anyone who desires can begin laying his plans on paper immediately for the rocket conquest of the earth, just as if a base upon the moon were already in existence.

     Suppose we try to anticipate the future by making such plans ourselves. No one would dare attempt to foretell the course of discovery in electronic or nuclear physics, but there is no corresponding uncertainty about the motions of bodies in space. The position of the moon a thousand years hence can be determined today with a margin of error that would seem trifling to anyone except an astronomer.

     Let’s say that the calculations necessary to launch a body from the moon so as to strike a selected point upon the earth have been carried through rigorously by an enemy. For this purpose, New York City has been chosen as the first target.

     We will begin detailing the evening's attack problem by briefing the reader quickly regarding conditions under which a lunar military base would be -operated. The essential facts upon which astronomers are well agreed can be summarized in a few words.

     The surface of the moon is exceedingly rough and broken, crossed by several steep mountain ranges and studded with thousands of craters. As a friend of mine from the Middle West once remarked, it would make mighty poor farming land. Although the craters resemble volcanoes in certain respects their origin is still a matter of speculation. If they were once volcanoes it is certain that they are quite extinct now, for there is no accepted record of one ever having been seen in eruption.

Data on Lunar Conditions

     The most delicate tests have failed to reveal any trace of lunar atmosphere. Therefore, it seems work on the moon would have to be done in a hard vacuum, as physicists call it. The first expeditions would be compelled to carry their own supply of oxygen and water, but eventually it should be possible to produce those necessities chemically from mineral deposits. We should expect to find the same elements on the moon that occur on the earth, although not necessarily in the same abundance.

     Without an atmospheric blanket to shield the surface from the rays of the sun by day, or prevent the escape of heat into space at night, the range in temperature on the moon is far more extreme than it is upon the earth. During the lunar day, which lasts for two of our weeks, the bare rocks become hotter than boiling water; while during the equally long lunar night their temperature falls far below that of dry ice. Yet probably a few feet below ground enough warmth remains from the sun’s rays to keep the temperature above the freezing point.

     Instead of appearing light blue as it does on earth the sky is uniformly black because there is no air to diffuse sunlight. The stars are always visible as sharp unwinking points of light even when the sun is shining among them. On the equator the earth looms overhead as a bluish-tinted globe with white polar caps, four times as big as the moon appears to us. The earth hangs almost fixed in the sky only shifting back and forth very slightly during the course of a month.

     Trying to work under such abnormal conditions would be a severe handicap. Living quarters and other installations would have to be in airtight chambers underground. To venture outside without wearing a space suit inflated to atmospheric pressure would be instantly fatal. A man would burst like a deep-sea fish brought up from the depths of the ocean. As there is no air on the moon to carry sound, communication out of doors would have to be by portable radio or sign language.

     Is the moon inhabited? This is a question that no one can answer definitely but it is hard to see how life could survive under such unfavorable conditions. It is safe to say that the moon is a desolate world utterly devoid of life.

     Returning now to what we shall call Operation Knickerbocker (Knickerbocker refers to people or objects from Manhattan ), the general approach to the problem of hitting the earth from the moon is not so different in principle from that of a man who is preparing to shoot at a jack rabbit from a moving automobile. After making allowance for his own motion, the hunter aims at where he estimates the rabbit and the bullet meet.

     In some ways the astronomer’s problem is simpler than the hunter‘s; in others, it is much more complex.

     Rabbits are unreliable animals prone to changing course suddenly, without warning. Even if a rabbit obligingly ran with uniform velocity in a straight line the hunter might have his aim spoiled by a bump in the road. But we can rely upon the earth and moon to keep moving smoothly around the sun year after year in docile obedience to the law of gravitation.

     On the other hand, gravitation is a complicating factor in launching a rocket into space. It would be disastrous to neglect the gravitational attraction of the earth and moon, for they never cease to influence the rocket over every inch of its path. It is somewhat as if the hunter and rabbit were able to exert an influence on the course of a bullet after it leaves the gun. Nor are the earth and moon the only bodies that would act upon a rocket. Although 93,000,000 miles away from the rocket’s path, the sun is so massive that during most of the flight it would out-pull the earth and moon combined.

     We are now confronted by one of the most famous problems in the history of science: the problem of what would happen if three or more bodies were turned loose in space with nothing but the law of gravitation to guide them. The greatest mathematicians have never been able to find a practical general solution to the interstellar problem, although plenty of them have tried. Any particular case, however, can be solved by a slow and tedious process called numerical integration, whereby the answer is obtained a little bit at a time, like a detective gathering clues which, added together, enable him to reconstruct the crime.

     We will suppose that the message containing the last-minute instructions to the enemy chief of staff has been received and that all arrangements have been completed for launching his Diana I, the first rocket ever to be fired at the earth. The base is situated upon a comparatively level expanse about a hundred miles northwest of the great crater Eratosthenes on the southern edge of the Imbrium Mare, or Sea of Showers, as it was named by the old astronomers.

     The zero hour is set at 7:00 A.M. Eastern standard time, of March 3l, 1949, which corresponds to slightly past midnight by local lunar reckoning. The lunar landscape is brightly illuminated by the earth overhead. Africa and Europe can be readily discerned near the center of the disk, with eastern Asia just visible near the twilight zone.

Seconds of Tension

     In the underground control room technicians are seated before the mechanism that will send the rocket into space. A clock synchronized with the quartz crystal oscillator at the U.S. Naval Observatory in Washington indicates the seconds till 700 hours—fifty-eight—fifty-nine—zero!

     There is no sound as the rocket rises vertically from the launching cradle, a column of flame streaming from its exhaust. The ground crew watches anxiously as the Diana I rapidly gains altitude. But with not a breath of air to disturb its motion the take-off is perfect. Soon the automatic pilot begins to incline the missile gracefully toward the east.

     An astronomer notes that it is heading in the direction of the star Alpha in the constellation of Libra the Balance. He nods with satisfaction—exactly on course.

     When the flame from the exhaust suddenly dies, the watchers know the rocket is finally on its way. No more fuel is needed to keep it moving now—it is a free body in space. Were it not aimed for collision with the earth, the Diana I would revolve around the sun indefinitely, a tiny man-made planet among the myriad natural inhabitants of the solar system.

     Diagram 1 shows the rocket’s progress for the first six hours. It moves away from the moon in a nearly straight line, slowing down a trifle at first but soon going at a pretty steady rate of about 8,000 miles an hour toward its rendezvous with New York.

     When Diana I crosses the halfway mark, at 120,000 miles. the sun is rising at New York on the morning of Friday, April 1, 1949. In New York. then, people are awakening. scanning the headlines over their coffee, and beginning to make plans for the day, never dreaming of the death that is rushing at them from outer space.

     By 8 o’clock the speed of the rocket is quickening under the mounting attraction of the earth. At 11 o’clock it is 10,200 miles from New York and moving at a 15,700-mile-an-hour clip. Forty minutes later its mission is ended. Diagram 2 shows its approach to the earth during the final minutes.

Easy to Miss the Target

     It is doubtful if the first rocket would be launched with such precision that it would speed unerringly to the target as we have described. An error of a tenth of a mile per second at the start could throw the rocket several thousand miles off course by the time it had covered the distance between the moon and the earth.

     In actual practice the first rocket might, instead of hitting New York, land far to the west in the Aleutian Islands or even miss the earth entirely. But as soon as ballistic experts on the moon were able to determine how far off their first shot was, they would correct their aim for the second.

     Suppose they are luckier than they deserve on the third and fourth shots, which land on Manhattan and Queens, and the fifth and sixth which drop less than 50 miles away. There would be no respite even when the United States is turned away from the moon. Methodically the men on the moon could proceed with their work of destruction. Secure from reprisal they would be in no hurry to press the attack.

     In modern warfare the psychological effect of a new weapon is often almost as important as its capacity to destroy. From this standpoint a rocket attack from the moon should be eminently successful. Attempts to trace the source of the attack would be practically hopeless. Rockets would seem to be arriving from all directions out of nowhere. There would be a terrible frustration at being unable to fight back. The nation that secretly initiated the attack could loudly protest its innocence. pretending to be as bewildered and mystified as ourselves. It might even arrange to have a few rockets fall in its own territory to make this story sound convincing.

     We have attempted to describe war as it might come in the future. Is there any possibility that manned rockets will reach the moon during our lifetime?

     There are many who scoff at the mere mention of such a notion. Others feel we are just as good as on the moon right now. (Several inquiries have been received by the government land office regarding title to land acquired on the moon.) The truth of the matter is that most people are simply guessing or indulging in wishful thinking. But one amateur rocket society, whose members design and test real rockets and so should be thoroughly aware of the difficulties to be overcome, went on record in June, 1946, as believing that manned rockets will complete the round trip to the moon within approximately two decades.

     The trouble with trying to get reliable information is that the only individuals who really know how much progress has been made toward space travel are scientists working for the government. and their knowledge is a profound military secret. The government has been releasing very little information on rockets lately.

     So who can say how close we are to making a lunar hop?

From ROCKET BLITZ FROM THE MOON by Robert S. Richardson
Collier's Magazine, October 23, 1948

If we had a base on the moon, either the Soviets must launch an overwhelming nuclear attack toward the moon from Russia two to two-and-a-half days prior to attacking the continental U.S., or Russia could attack the continental U.S. first, only and inevitably to receive from the moon some 48 hours later sure and massive destruction.

From Aviation Week; September 29, 1958
by Brig. General Homer A. Boushey, deputy director of advanced technology, USAF

      On 28 January 1958, U.S. Air Force Brigadier General Homer A. Boushey, Deputy Director of U. S. Air Force Research and Development, spoke before the Aero Club of Washington. The weekly news magazine U.S. News & World Report took note and published excerpts from his speech.

     Boushey warned the Aero Club of dire consequences should the Soviet Union seize control of the Moon. He presented his speech four months after Soviet engineers had launched 83.6-kilogram Sputnik 1, the first artificial satellite, three months after they had launched the dog Laika on board 508.3-kilogram Sputnik 2, and three weeks after the failure of Vanguard TV-3, the first U.S. attempt to launch a satellite.

     When Boushey is described in any detail, he is often portrayed as a strangelovian Cold Warrior. He is, however, better seen as an early U.S. rocketry and spaceflight proponent. He had enrolled in Stanford University to study engineering in 1929, but the Wall Street Crash of that year and consequent Great Depression intervened, so in 1932 he joined the U.S. Army Air Corps. During training at Randolph Field, Texas, he encountered a copy of U.S. rocketry pioneer Robert Goddard's seminal 1919 monograph A Method of Reaching Extreme Altitudes.
     Goddard had launched the world's first liquid-propellant rocket, named "Nell," on 16 March 1926, in Auburn, Massachusetts. The rocket flew 184 feet, or roughly half the length of a Saturn V Moon rocket. He received funding support for his rocket experiments from the Smithsonian Institution, which published his monograph, and from the wealthy Guggenheim family. The latter's support enabled Goddard to move his experiments to the wide-open spaces of New Mexico in 1930.
     Boushey completed his aeronautical engineering degree at Stanford in 1936, and joined the Aircraft Laboratory at Wright Field in Ohio. While there, he corresponded with and visited Goddard. The two men became fast friends; Goddard would become the godparent of one of Boushey's daughters.
     In August 1941, Boushey served as the test-pilot for a series of U.S. government-funded rocket-assisted take-off experiments. These employed solid-propellant rocket motors to boost a single-seater Ercoupe airplane off a runway. Theodore Von Kármán of the Guggenheim Aeronautical Laboratory at California Institute of Technology led the rocket development effort. The plane's single propeller was removed for the final test on 23 August; Boushey then took off under rocket thrust alone, making him the first American to pilot an exclusively rocket-powered aircraft.
     During the Second World War, Boushey commanded the first U.S. jet-powered fighter group. In the days after the Japanese capitulation, he flew over Hiroshima, allowing him to observe firsthand the devastation nuclear weapons could cause.

     In his January 1958 talk, Boushey acknowledged that there existed in the nascent U.S. space community "divided opinion as to whether or not a manned or unmanned Moon base has any military significance." He then presented arguments in favor of a military lunar base.
     The Moon, he explained, is 239,000 miles away, a distance a rocket might cross in about two days. Boushey noted that the Moon is a synchronous rotator, which means that it keeps the same face turned always toward Earth. Telescopes on the moon's Earth-facing Nearside could thus monitor military activities on the revolving Earth as they passed in and out of view. Boushey estimated that objects as small as 100 feet wide might be visible. Conversely, the Farside hemisphere is always turned away from Earth. Boushey believed that this would make it an ideal location for conduct of secret military operations beyond the reach of prying eyes in Russia.
     Earth's Moon, Boushey declared, could also provide "a retaliation base of unequaled advantage." If the U.S. gained control of the Moon, then the Soviets would be unable to attack the United States without suffering "sure and massive destruction." They could either attack the U.S. first and endure a counter-strike from the Moon about 48 hours later, or they could launch missiles at the Moon first. The U.S. military lunar base would, of course, immediately detect the light and heat of the Soviet missiles' rocket exhaust and launch a retaliatory strike.
     Boushey then spoke what are probably the most famous words in his speech: "[i]t has been said that 'he who controls the Moon controls the earth.' Our planners must carefully evaluate this statement for, if true — and I, for one, think it is — then the U.S. must control the Moon."
     The excerpts from Boushey's speech in U.S. News & World Report contained no overt mention of the possibility that U.S. missiles might be launched from the Moon preemptively; that is, that the U.S. Moon base might be used to destroy the Soviet Union with little risk of retaliation. Boushey did, however, describe attributes of the Moon that would make a preemptive attack feasible.
     The Moon's weak gravitational pull, coupled with its lack of an atmosphere, would permit missiles to be "catapulted" from their siloes, thereby avoiding use of easily detected rocket motors. Hiding the siloes on the Farside would further increase the odds that a U.S. attack would go unnoticed until warheads entered Earth's atmosphere over Soviet territory.
     Building and maintaining the U.S. military lunar base would not, Boushey maintained, have to break the bank. He assumed that the Moon would be found to be made of the same elements as the Earth, so that the "possibilities of construction and creation of an artificial environment [would be] virtually unlimited." Electricity from solar panels made on the Moon could be stored using massive lunar-made flywheels which, once spun up by lunar-made electric motors, could spin for weeks in the absence of atmospheric friction. By using the flywheels to turn the electric motors, the latter could become generators for supplying the base with electricity during the two-week lunar night.

     Boushey ended his speech by offering an alternative to lunar militarization. He pointed out that on "January 16 [1958] Secretary [of State John Foster] Dulles proposed the formation of an international commission to insure [sic] the use of outer space exclusively for peaceful purposes, and if the Soviet premier is sincere in decrying the production of ever-more-powerful weapons he will jump at the chance. In 10 years," he added, "the opportunity of jointly imposing control may have been lost."
     Almost exactly nine years after Boushey delivered his speech, on 27 January 1967, the U.S., the Soviet Union, and the United Kingdom signed the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies. The following October, they called upon other nations of the world to sign and ratify what had by then become known as The Outer Space Treaty. Among other far-reaching provisions, it required that the Moon not be put to any military purpose. The Outer Space Treaty, which took effect on 10 October 1967, became the rock upon which the body of international space law is built.
     By the time The Outer Space Treaty took effect, Boushey had been retired from the Air Force for a little more than six years. He ended his career at age 52 in July 1961 as Commander of the Air Force Arnold Engineering Development Center in Tennessee. By that time, President Dwight Eisenhower had passed over the military in favor of civilian U.S. space exploration under the aegis of NASA. Despite military support for NASA programs and some brave starts, such as the Dyna-Soar spaceplane and the Manned Orbiting Laboratory, U.S. military spaceflight would be limited mainly to automated surveillance satellites until the Space Shuttle era.
     Soon after his retirement, Boushey became an outspoken critic of the escalating war in Indochina. Despite this, President Richard Nixon recognized his key role in U.S. astronautics by inviting him to the 13 August 1969 "Astronauts' Dinner" held in Los Angeles to celebrate the July 1969 triumph of Apollo 11, the first piloted Moon landing.
     In 1982, while the Administration of President Ronald Reagan called for expansion and modernization of the U.S. nuclear arsenal, Boushey co-sponsored California's Nuclear Freeze ballot initiative, which passed overwhelmingly. In 1985, he joined other retired U.S. military officers in Moscow to draft an agenda for nuclear arms control. He cited his 1945 flight over Hiroshima when he declared that political leaders did not adequately grasp the destructive power of nuclear weapons. The man who had spoken out for a U.S. military Moon base in 1958 spoke out against nuclear weapons to the end of his days. Boushey died in 2000 on Christmas Day at the age of 91.


"Who Controls the Moon Controls the Earth," Homer A. Boushey, U.S. News & World Report, 7 February 1958, p. 54.
"Gen. Homer Boushey dies; he was a pioneer in rocket-powered aircraft," The Almanac, 3 January 2000 ( — accessed 2/1/20).
"Homer A. Boushey," Keay Davidson,, 6 January 2000 ( — accessed 2/1/20).

From HE WHO CONTROLS THE MOON CONTROLS THE EARTH (1958) by David S. F. Portree (2015)

Ever since the dawn of the space age lunar base proponents have had a difficult time explaining exactly why a lunar base is needed and what it can do that justifies its immense cost. NASA is currently struggling with that issue right now. But in the late 1950s the United States Air Force had what its leadership believed was a clear rationale for building a base on the Moon: use the Moon to spy on the Earth and throw nuclear bombs at America’s enemies from the ultimate retaliatory high ground. Dr. Strangelove would have approved. Fortunately, saner heads prevailed.

This is not their story.

Instead, this is the story of the contractor teams that for a brief time were given a nearly impossible goal by the US Air Force: find something useful to do on the Moon, preferably involving bombs.

Tossing bombs from high places

The concept of the Moon as a strategic base apparently dates at least back to 1948 and an article by Robert S. Richardson titled “Rocket Blitz From the Moon” in the mass-market Collier’s magazine. The article was beautifully illustrated by famed space artist Chesley Bonestell. In one Bonestell painting a bullet-shaped rocket (illogically equipped with large aerodynamic fins) is blasting off from a lunar crater. Another rocket stands prepped in the background and a lunar base is tucked into the side of a mountain. In the next illustration—probably Bonestell’s most dramatic painting ever—Manhattan has been blasted with at least three atomic bombs.

Richardson’s article focused primarily on the physics of the Moon: the low gravity, the lack of air, the trajectory and velocity calculations for firing rockets at the Earth. Rather than advocate that the United States should build a lunar rocket base, Richardson warned that another country could undertake a secret project to develop a lunar base and achieve strategic surprise against the United States. He did not clearly explain why the Moon would be a good place for basing missiles other than presumed safety from Earth observation, and noted that it would take at least a day for a rocket to reach Earth with its warhead. Considering that there were other means of basing long-range strategic weapons that did not involve the massive cost of a space program and a lunar base, Richardson’s idea was fanciful at best. But Collier’s was a large circulation magazine, not a science fiction pulp, and this short article certainly reached a big audience.

Richardson was not the only person writing about the possibilities of using space as a platform for attacking Earth. Robert Heinlein co-wrote a non-fiction article in August 1947, also for Collier’s, called “Flight into the Future.” Heinlein and his co-author, US Navy Captain Caleb Laning, suggested basing atomic weapons in orbit, and Heinlein later used this idea in his book Space Cadet. The 1950 movie Destination Moon, which Heinlein co-wrote, also echoed a similar theme (see “Heinlein’s ghost (part 1)”, The Space Review, April 9, 2007). One of the characters in the movie explains why a lunar base is necessary: “There is absolutely no way to stop an attack from outer space. The first country that can use the Moon for the launching of missiles will control the Earth. That, gentlemen, is the most important military fact of this century.” (Decades later, Allen Steele would explore the idea of a missile base on the Moon in his novel The Tranquility Alternative.)

In December 1956, the commander of Air Research and Development Command, Lieutenant General Thomas S. Power, established a Guided Missile and Space Vehicle Working Group. Three months after Sputnik, in December 1957, that group issued a “Special Report Concerning Space Technology” that laid out an “ARDC Five Year Projected Astronautics Program” including a “Manned Lunar-Based Intelligence System,” with a projected first flight in 1967. By January 1958 the Air Force initiated Program 499, a “Lunar Base System” and by March the Air Force was formalizing plans for a “Manned Lunar Base Study.”

It did not take the Air Force leaders long to start talking about their plans in public. In January 1958 USAF Brigadier General Homer A. Boushey spoke in front of the Aero Club of Washington, DC. Boushey’s speech was reported in U.S. News & World Report under the title “Who Controls the Moon Controls the Earth.” Boushey justified the Moon base in terms of national security using language that could have been taken straight from Heinlein’s Destination Moon eight years before: “The Moon provides a retaliation base of unequaled advantage,” Boushey said. “If we had a base on the Moon, the Soviets must launch an overwhelming nuclear attack toward the Moon from Russia two to two-and-one-half days prior to attacking the continental U.S. first, only and inevitably to receive, from the Moon—some 48 hours later—sure and massive destruction.”

Boushey was not the only Air Force officer publicly calling for a Moon base to provide retaliatory capability. In early March 1958, Air Force Lieutenant General Donald L. Putt spoke before the House Armed Services Committee about various possible responses to the Soviet Sputnik launch, including a base on the Moon. According to a Time magazine report, “Since the Moon’s gravitation is only one-sixth as strong as the Earth’s, it should be easier to shoot at the Earth from the Moon than in the other direction (The Gravity Gauge). The Moon’s lack of atmosphere might make it possible to catapult Earth-bound missiles out of deep shafts. Both the Moon base and its weapon launchers could be on the far side of the Moon, forever invisible from the Earth, but all of the turning Earth could be examined from the Moon with telescopes.” Putt also made a suggestion that seems amazing when looking back on fifty years of space history: “We should not regard control of the Moon as the ultimate means of ensuring peace among the Earth nations,” Putt said. “It is only a first step toward stations on planets far more distant… from which control over the Moon might then be exercised. Nevertheless, the Moon appears to be of such significance that we should not let another nation establish a military capability there ahead of us.”

And so in the fall of 1958 the advanced systems studies office of the Air Force Ballistic Missiles Division in Los Angeles commissioned several studies by defense contractors to evaluate the strategic value of manned spaceflight. These were “Systems Requirement” studies. SR-181 was called the Strategic Earth System Study (or alternatively, the Global Surveillance System), SR-182 the Strategic Interplanetary Study, and SR-183 the Lunar Observatory Study. All three of the studies apparently included a nuclear weapons component. SR-183 eventually gave birth to SR-192, a Lunar Strategic System study. That’s not where it ended, either. A declassified 1963 report lists several other studies as well: SR-17527, the Military Test Space Station; SR-17532, the Permanent Satellite Base and Logistic Study; SR-79503, the Strategic Orbital System, SR-79814, the Space Logistics, Maintenance and Rescue System; SR-79821, the Earth Satellite Weapon System; and SR-79822, the Advanced Earth Satellite Weapon System. Clearly the Air Force had a lot of people looking at various projects for putting humans in space for “strategic” purposes, as well as orbiting nuclear weapons. Dr. Strangelove would have been orgasmic.

Unfortunately for historians, none of these studies has been found and released, nor has anyone discovered significant supporting documentation like memos, letters, and other paperwork associated with the studies—all of these references (the ones in quotes above), with the exception of the magazine articles quoting Generals Boushey and Putt, tend to be footnotes or citations in other reports. Researching the history of early Air Force lunar base studies is like reading Wikipedia: every article refers to some other article that refers to another article that, at best, refers to a list of documents or studies, not the actual documents or studies themselves.

The Lunar Observatory Study summary report was declassified in the 1970s, but is only nine pages long and lacks many details. These reports may still exist somewhere, buried in dusty government archives next to the Ark of the Covenant or even in the garage of some retired Air Force officer who once illegally took a copy home. For the most part historians simply know that they existed, but almost nothing about what they addressed. The most likely explanation for their demise is that they were the victim of Secretary of Defense Robert McNamara, who took over the Pentagon in 1961. McNamara’s whiz kids applied systems analysis and economic models to weapons systems and many of the Air Force’s pie-in-the-sky ideas were soon canceled for the simple reason that they were incredibly expensive ways of doing things that really did not require doing. Although McNamara has a legacy overshadowed by Vietnam, in the early 1960s he managed to kill a number of dubious and expensive Air Force programs, and it seems probable that the military lunar base was one of them.

But it is also apparent that there was no discussion of lunar missile bases in the highly active deterrence theory community at the time these Air Force studies were underway. By the late 1950s the RAND Corporation was producing voluminous studies on deterrence theory, including the need for survivable nuclear forces capable of riding out a first strike and smashing the commies into dust. Some of RAND’s most famous thinkers—the “wizards of Armageddon” to use Fred Kaplan’s immortal phrase, men like Bernard Brodie, Herman Kahn, Henry Kissinger, and Albert Wohlstetter—were writing publicly about deterrence theory. Lunar bases equipped with nuclear weapons do not appear in any of this literature. The late, great Brodie’s seminal book Strategy in the Missile Age, first published in 1959, makes no mention of the Moon as a missile base. Thus, it appears that the Air Force’s strategic space studies had no discernible impact on Cold War nuclear deterrence and are little more than a footnote in Cold War history.

However, their impact on the American space program—and thus, space history—may be greater than historians have recognized. The fact that these Air Force SR studies have not been found has apparently distorted the historical record of early American lunar planning. A similar Army study, known as Project Horizon and conducted at the same time, has been declassified in its entirety for many years, and attracted much more attention from historians. But the Air Force studies involved many more companies and personnel and lasted over a longer period of time, and it is possible that they have had a subtle legacy that has been overlooked by space historians.

A lonely ambassador and keen observer

Fortunately for historians, there is some new information on the Air Force’s SR-183 study effort in the form of detailed notes taken by NASA official Edwin P. Hartman who attended a mid-point briefing on the lunar study. Hartman’s records are preserved in the National Archives regional office for southern California at Laguna Niguel, south of Los Angeles. They provide much more detail and insight into the Air Force lunar study than has been previously disclosed.

Starting in the early 1950s, Hartman was the head of the Western Support Office of the National Advisory Committee on Aeronautics (NACA), which was absorbed into NASA when it was created in fall 1958. Hartman’s job was to serve as the representative of NACA and then NASA in southern California. NACA conducted aeronautics research and did not buy much hardware, and so Hartman was in many ways a lonely ambassador representing NACA’s interests in southern California, as well as the organization’s eyes and ears on the West Coast. As NASA increased in size and began to sign hardware development contracts with aerospace companies in California, the agency increased its presence on the West Coast and Hartman’s role changed. By the early 1960s the agency needed representatives at the factories that were building the Apollo spacecraft and the Saturn rockets. But during the 1950s Hartman was pretty much the sole agency representative, traveling to various aerospace companies and obtaining briefings on their work and then reporting back to his bosses in Washington, such as NACA director Hugh Dryden.

Hartman was a keen and meticulous observer and his reports from this era are a treasure trove for many reasons, including the fact that so many corporate records have never been preserved. Hartman reported not only on what projects the companies were undertaking, but also their key figures and personalities and even the companies’ financial situations and organizational and other problems. Although his memos represent his personal point of view, and sometimes humorously demonstrate the difficulties for an airplane expert to adapt to the new subject of spaceflight (for instance, referring to “turns” around the Earth instead of “orbits”), in some cases history has revealed that Hartman’s observations were extremely astute.

Charity work with taxpayer money

In late March 1959 Hartman attended several briefings at the Ballistic Missile Division in Los Angeles conducted by industry teams on the results of their studies concerning SR-183, the lunar systems or lunar observatory study. According to Hartman, there were four industry teams, consisting of North American Aviation’s Missile Development Division and RCA; Boeing, Westinghouse, and Aerojet Nucleonics; Republic Aviation and Systems Corp. of America; and United Aircraft Corp. and Minneapolis-Honeywell. The Douglas Missiles Division participated on its own. Somewhat surprisingly, Lockheed, which then had the most active space program, the WS-117L reconnaissance satellite program funded by the Air Force, was not a participant. According to a 1992 history paper by Lockheed employee R.D. Allen, the company did bid on the studies, but was apparently not selected. By late 1958 Ballistic Missile Division officers were concerned that Lockheed was overextended and so they may have banned the company from participating in the study effort.

The briefings occurred over several days and Hartman missed the final briefing by United Aircraft and Minneapolis-Honeywell and therefore did not report on their work. These companies were presenting their results at the mid-point of the one-year study. After these briefings, information on the study leaked (or was officially given) to Aviation Week magazine, as happened again in September 1959 when the study was concluded. But Aviation Week lacked the detail that Hartman provided about the Air Force effort in his extensive notes. The Army study was apparently initiated in March 1959, only shortly before the Aviation Week article appeared, but the decision to finish the Project Horizon study before the rival Air Force finished its study was undoubtedly due to a desire to beat the Air Force to the punch.

There is conflicting information about whether the studies were funded by the Air Force or undertaken using company money. According to the final summary report produced a year later, three of the individual companies were funded whereas the others were “voluntary.” In his notes Hartman implied that all of the teams used their own money for what must have been expensive studies involving a lot of people. “The companies that undertake SR studies for the Air Force do so largely at their own expense,” he explained. But Hartman also had a rather blunt insight into what a “voluntary study” really meant: “As the income of most aircraft companies comes mainly from the government, it is obvious that the studies are paid for by the government with the cost appearing as overhead charges on military contracts,” he wrote. The fact that at least part of the work was not directly paid for by the government may explain why these SR studies have so far eluded historians—very little paper in the form of final reports may have actually made its way into the hands of government officials, and what did was probably stamped as industry proprietary.

“The objective of SR-183,” Hartman wrote, “is to determine a sound and economical approach for the establishment of a manned intelligence observatory on the Moon. The Moon is considered a favorite vantage point from which to observe enemy actions in space. Also, because of its low gravity, the Moon is believed (by some people) to be a good platform for launching defensive vehicles.”

Based upon Hartman’s description of the four industry briefings he attended, it is clear that these studies clearly started with each team suggesting multiple ideas about what the Air Force could do on the Moon, determining the technical aspects of them, and trying to flesh out the basics of how to start a lunar base project. Given the fact that the teams had only six months and virtually no experience at all in spaceflight—certainly not human spaceflight—it is not surprising that they often proposed some rather unrealistic, even fanciful ideas. Some of their ideas are still around even today, and may be no more possible now than they were half a century ago.

But a funny thing also happened on the way to the Moon: the thought experiment of a Moon base highlighted the superiority of other ways to do things in space. The contractors concluded that a number of missions really could be better accomplished from different locations, like geosynchronous orbit. Much like today, it appears as if government officials picked the location and then asked contractors to figure out what, if anything, they could do there, rather than figuring out what they wanted to do, and then deciding the best location for doing it.

Rockets on the Moon

“There is not much of a general nature to be said about the presentations except that they all seemed a little fantastic,” Hartman wrote in an introductory memo. “The Douglas presentation was the briefest, most pessimistic and most down to Earth—if a lunar venture may be so described.” He ranked the Boeing and Republic briefings the lowest and stated that “all of the presentations suffered greatly from a lack of basic knowledge about the subject discussed. In them the meager knowledge that exists was over-extrapolated. Fanciful concepts were described which, aside from the intellectual stimulation they produced, are probably of little value.” Nevertheless, he thought that the overall effort was worthwhile because the studies did lead the companies to start thinking about various space missions.

Although the study focused on using the Moon as an observation base, Boeing, like several other contractors, advocated basing nuclear missiles on the Moon in underground silos. In his memo to NASA Headquarters, Hartman drew a crude sketch of Boeing’s underground base, which included a spiral staircase down from the surface, two levels of crew quarters, and 50- and 200-inch (125- and 500-cm) telescopes that could be adapted for infrared surveillance and communications. The base would also have a radio telescope and surface vehicles. The base might actually be excavated through bombardment from space, which Hartman euphemistically called “hard landing.”

Boeing’s schedule was to “probe” the Moon from 1958 to 1961, explore the surface with humans from 1963 until 1973, and begin site preparation and construction in the middle of the 1960s, with the goal of beginning operations by the end of the decade. Ultimately, according to Boeing’s plan, 116 men would reach the Moon by 1973, and the effort would cost $8 billion by the end of 1965 and $30 billion by the end of 1967, with peak spending of about $10 billion that year.

None of this was remotely like what actually happened. The Apollo program ultimately cost approximately $24 billion through the early 1970s. For approximately the same amount that Boeing projected, Apollo landed a dozen men on the Moon, not ten times that many, and never seriously considered the establishment of a base under the lunar surface.

However, not all of Boeing’s speculation was outlandish. The company recommended that for astronomical observations the Air Force could install a 240 inch (610 cm) focal length telescope inside a large airplane such as a B-52. The plane would carry the telescope high above much of the Earth’s atmosphere. NASA flew an infrared telescope aboard an airplane in 1964 and then the dedicated Kuiper Airborne Observatory starting in 1974, and is now developing the SOFIA observatory utilizing a Boeing 747. Another Boeing suggestion was the possibility of using space tethers to boost satellites into higher orbits. Although NASA tested tether technology in the 1990s, the agency abandoned it.

North American concluded that surveillance of the Earth was the chief value of a lunar observatory and that possible missions for a lunar base included signals intelligence collection, television and photo surveillance of the Earth, and navigation aids and communications relay. But the company’s engineers admitted that observation of the Earth was challenging from such distances. For instance, detecting a Soviet ICBM silo with 90% certainty required a photographic system with one-meter resolution, demanding a truly massive telescope on the lunar surface. The company’s engineers figured that a human circumlunar flight could be mounted by 1962 with a manned landing by 1963 or 1964. Much of the team’s presentation consisted of identifying the steps required to achieve those goals, such as the liftoff thrust of the rocket vehicles and the radiation threat on the Moon. The team concluded that the proper approach to base design was “wide open,” which Hartman translated to mean “no one knows anything about it.”

The Douglas group, like Boeing, also concluded that military intelligence and reconnaissance from the Moon, including “aid in facilitating retaliatory strikes,” were the primary missions for a military lunar base. Douglas also noted that the Moon could be used as the site of a spinning liquid mercury mirror. Such a mirror, the company claimed, would be easy to carry to the Moon and would not be affected by meteorites, but it could not change its observation direction. According to Douglas, the advantages of the Moon over satellites were that it was a more stable platform, a harder target to attack, possessed exploitable natural resources, and had a gravitational field that would provide a more natural environment for humans.

Douglas’ engineers proposed that the basic element of their Moon base would be a telescoping series of pie-shaped wedges that folded into a wedge-shaped capsule for transportation. This would then open into a torus-shaped igloo with an inner bag to hold pressure. Douglas later proposed that basic design as an Earth-orbiting space station, but its greatest legacy was when a company scale model was acquired by the Star Trek television production team in the latter 1960s and turned into the famed K-7 space station for the episode “The Trouble With Tribbles.” (see “Boldly going: Star Trek and spaceflight”, The Space Review, November 28, 2005)

Unlike North American’s team, Douglas concluded that signals intelligence from the lunar surface seemed “far-fetched.” Similarly, observing ICBM launches on the Earth from the Moon was not possible, but a satellite in a 24-hour (i.e. geosynchronous) orbit could see them with an infrared telescope. As a matter of fact, it was precisely this approach that was developed by the Air Force a decade later, although it was TRW and not Douglas that built the first geosynchronous missile warning satellite, launched in the early 1970s.

Of all the contractor teams, Republic was the only one to declare that prestige was a primary reason for establishing a lunar base. The military missions included weather observation and monitoring of enemy movements, satellite attack, retaliatory bombardment, signals intelligence collection, space vehicle detection and tracking, scientific and experimental use, and a staging base for interplanetary missions. But Republic also noted that the Moon was so far from Earth that it was not an ideal observation platform. A 75- to 100-centimeter mirror on the lunar surface could observe features on the ground about 300 meters wide, whereas a similar mirror in geosynchronous orbit could resolve objects about ten times better. Like Douglas, Republic concluded that signals intelligence from the Moon was impractical. Republic concluded that of all the missions, the establishment of a retaliatory base appeared to be the most promising, echoing Boeing and Douglas.

Republic suggested that the best plants to grow on the Moon were corn, peanuts, soybeans, and lettuce. Water could possibly be extracted from rocks and volcanic ash. But Republic did not underplay the difficulties of a lunar base, noting that developing a closed ecological system would be a major engineering challenge. Communications would also be problematic because the line of sight was short due to the high surface curvature, and relay satellites would be required. Because communications bandwidth would be limited, most data should be processed on the Moon and only the results sent back to Earth.

The Moon is a harsh mistress

Although Hartman was only reporting on the midpoint of the study effort, the contractors’ work revealed several common themes. Many of them suggested that the Moon’s surface was a poor base for observations of the Earth and that Earth orbit was superior. Discounting all of the problems of working on the Moon, the simple fact was that the Moon was too far away. Put the same size telescope in geosynchronous orbit and it could see ten times better, provided that you could solve the problems of pointing and stabilization, which Lockheed achieved within a few years. Other military missions such as signals intelligence were not really viable from the Moon. And although Hartman’s notes don’t say it, one problem with the Moon is that it only viewed about half of the Earth at any one time. Even with a substantial base on the Moon, the United States would still need satellites to observe the rest of the Earth—and if observation satellites were already in Earth orbit, what use was a Moon base?

Another characteristic of these early studies was that the contractors knew very little about the problems of working on the Moon, even when some of those hazards should have been obvious. For instance, they were concerned about the threat from ultraviolet radiation from the Sun, but none of them appear to have mentioned galactic cosmic rays, which had been discovered early in the century. They suspected that lunar dust might be a problem due to static electricity and the possibility of deep “dust traps,” but did not know that lunar dust could be incredibly abrasive. And their proposals for digging underground bases were proven to be insanely optimistic once the Apollo astronauts reached the surface and had a very difficult time driving their flagpoles into the ground.

The Lunar Expedition

These various studies were finalized by September 1959. In April 1960 Ballistic Missile Division produced its “Lunar Observatory Study,” which also had the classified title of “Military Lunar Base Program.” To date only the nine-page summary has been declassified and several Air Force historians have searched for, and failed, to find the more extensive version. This summary was based upon reports provided by the contractor teams, noting that Boeing, North American, and United Aircraft had all been funded, whereas Douglas, Republic, and Minneapolis-Honeywell (originally teamed with United Aircraft) had been “voluntary contractors.”

The short summary focused on the initial steps needed to establish a lunar base, stating that the primary goal was to reach the Moon and build a base there, and the Air Force could take several more years before beginning work on the military aspects of the project—in other words, the goal was to build it and figure out what to do with it later.

By 1961 the Air Force produced another study, called Lunex, for “Lunar Expedition,” that further outlined plans for a 20-person lunar base. The Lunex study estimated that a base could be built for only $8 billion. But Lunex was the high-water mark of the military lunar base concept. By May 1961 President Kennedy announced the goal of sending civilian Americans to the Moon by the end of the decade, not to build a base, but simply to land there; all talk of a military Moon base evaporated.

But something else had happened in the meantime—by 1960 the US Navy had launched the first of its Polaris ballistic missile submarines, the USS George Washington. The George Washington was survivable, and its missiles, although relatively short-ranged compared to a missile launched from the Moon, which could theoretically reach any spot on the Earth, were accurate enough to nuke a city. The Navy spent $64 billion on 41 Polaris submarines and 5000 missiles by 1967. That was an expensive program, but it provided a huge amount of retaliatory power. The Air Force never could have based more than a few missiles on the Moon. Although the SR-192 study that focused on a lunar missile base has never been released, or apparently even found in Air Force archives, it undoubtedly concluded that the cost of even a limited retaliatory base on the Moon would be enormous.

Wernher von Braun’s Project Horizon study was a crash effort started after SR-183 and finished before it. Soon after Horizon was finished von Braun and his organization were transferred to NASA, and some of his ideas developed for the Horizon study were ultimately implemented as part of Apollo. But the Air Force studies involved far more companies and exposed many of them to the problems of spaceflight for the first time. What Edwin Hartman’s notes imply is that there may be a real legacy to these early studies. They may have prompted some of the first evaluations within various aerospace companies about what kinds of space missions they could do, not on the Moon, but closer to Earth.

Some of the Harman memos reporting on the lunar briefing can be downloaded here (warning: 2 MB PDF file).


(ed note: Rocket Ship Galileo was the first Heinlein Juvenile novel, written in 1947 {3 years after the end of World War II}. In it, a nuclear scientist enlists the aid of his teenage nephew and friends to build an atomic rocket and be the first people to land on Luna. Don't sneer, Heinlein got most of the scientific details correct, as usual. Other than a somewhat lighthearted attitude toward radiation.

But when our intrepid crew lands on the moon, they are attacked by space Nażis! Actually a holdout group that escaped the surrender of Germany at the end of WWII for somewhere in South America and who have been plotting ever since. And they too are of the opinion that you cannot repel an attack from outer space. Not surprising in a Heinlein novel.

Our heroes' ship is bombed and destroyed by a Nażi space taxi, but they manage to turn the tables and capture it. The pilot is a certain Friedrich Lenz, who is an underling who cracks under interrogation.)

      He and his comrades had been on the moon for nearly three months. They had an underground base about thirteen miles west of the crater in which the shattered Galileo lay. There was one rocket at the base, much larger than the Galileo, and it, too, was atom-powered. He regarded himself as a member of the army of the Nażi Reīch. He did not know why the order had been given to blast the Galileo, but he supposed that it was an act of military security to protect their plans.
     “What plans?”
     He became stubborn again. Cargraves actually opened the inner door of the lock, not knowing himself how far he was prepared to go to force information out of the man, when the Nażi cracked.

     The plans were simple — the conquest of the entire earth. The Nażis were few in number, but they represented some of the top military, scientific, and technical brains from Hītler’s crumbled empire. They had escaped from Germany, established a remote mountain base, and there had been working ever since for the redemption of the Reīch. The sergeant appeared not to know where the base was; Cargraves questioned him closely. Africa? South America? An island? But all that he could get out of him was that it was a long submarine trip from Germany.
     But it was the objective, der Tag, which left them too stunned to worry about their own danger. The Nażis had atom bombs, but, as long as they were still holed up in their secret base on earth, they dared not act, for the UN had them, too, and in much greater quantity.
     But when they achieved space flight, they had an answer. They would sit safely out of reach on the moon and destroy the cities of earth one after another by guided missiles launched from the moon, until the completely helpless nations of earth surrendered and pleaded for mercy.

(ed note: in the German lunar base)

     He found the storeroom for the guided missiles, more than two hundred of them, although the cradles were only half used up. The sight of them should have inspired terror, knowing as he did that each represented a potentially dead and blasted city, but he had no time for it. He rushed on.
     He could see in his mind’s eye the row upon row of A-bomb guided-missiles in a near-by cavern. He could see them striking the defenseless cities of earth.
     No time to rig a powerful transmitter. No time for anything but drastic measures.

From ROCKET SHIP GALILEO by Robert Heinlein (1947)

Luke Campbell

The case of attackers in orbit and defenders on the ground is not nearly so one-sided as one might think.

Remember — the attackers are in orbit, so their missiles and gun shells are also in orbit. the attacker needs to cancel most of their orbital velocity to put them on a highly elliptical orbit that will intersect the desired point on the planet. This can use up quite a bit of delta-V.

On the other side, the defender does not have to put munitions in orbit. He merely needs to loft them up on a sub-orbital hop that just happens to have the attacker's spacecraft smacking into it at orbital speeds. This does not always require much delta-V.

The closer the attacker is orbiting the planet, the harder it is for him and the easier it is for the defender to use kinetics. Distant orbits will be harder for the defender to reach and allow the attacker to de-orbit munitions easier — but it also gives the defender a lot of time to respond and makes the munitions hit the atmosphere faster (which tends to badly ablate away the munitions, making it more difficult for them to cause damage at the ground). Close orbits are likely to be death traps for the attacker — easy for the defender to launch munitions on sub-orbital intercept trajectories, not much time for the attacker to react to them, and expensive for the attacker to bring his own munitions to bear.

Isaac Kuo

Luke Campbell, there's no orbit from which it costs more delta-v to send munitions planet-ward than the delta-v required to send munitions on an intercept path. The situation is roughly symmetric, but the atmosphere reduces delta-v to go "downward" while increasing delta-v to go "upward".

Luke Campbell


In close orbit, if the orbiting spacecraft sends its munitions on a minimum energy trajectory to intercept the planet, it will take much longer to reach its target than a surface-launched missile will take to reach the spacecraft. In addition, this minimum energy missile can only hit things on the other side of the planet from where it is launched, so you will not have the bombarding spacecraft doing its own spotting. One might argue that this is not likely to be the case anyway, but it does detract from the usual trope of the orbiting spacecraft seeing its target and launching missiles at it.

Here are some details, assuming a 200 km altitude circular orbit around an airless Earth. A minimum energy orbit will have an apoapsis at the point of launch and a periapsis at the opposite side of the planet. It will take 43 minutes to reach its target, and will require about 1 km/s of delta-V. This gives plenty of time for the target to either move out of the way or shoot down the missile.

A surface launched missile will take 3.4 minutes to reach the spacecraft at a 200 km altitude, on a minimum energy boost of just under 2 km/s delta-V. Evasion or point defense may be possible within this time, but will be more difficult.

To match the performance of the surface missile, the orbiting spacecraft must cancel its orbital velocity of 7.8 km/s, and thus requires 7.8 km/s of delta-V. This is also roughly what it will take if the spacecraft is doing its own spotting and targeting.

Since ground launched missiles could reasonably be expected to have 4 to 5 km/s of delta-V even with chemfuel propellant, you are looking at the ability to track the target at something like 1 to 1.5 g of evasion acceleration, or reduce the time to intercept by launching faster.

Isaac Kuo

Luke Campbell, it's not necessary for the LEO spacecraft to launch with minimum energy. Like I said, the situation is roughly symmetrical. It can shoot a missile "directly" downward—that is, with the thruster pointed straight up.

In the rotating reference frame of the orbit, the spacecraft is shooting a missile straight downward fighting against 1 gee of centrifugal force. In this rotating reference frame, it's like shooting a suborbital missile downward.

Of course, the atmosphere in this case helps rather than hurts.

Luke Campbell


I will compute the orbital parameters later when I have a bit more time, but I will note that the situation you describe will not work on a world with a significant atmosphere. On Earth, for example, the projectile will slice through the exosphere and hit the mesosphere at a steep angle, rapidly getting to regions of air dense enough for the shock heating to incinerate the projectile while the ram pressure disintegrates it. Here, the atmosphere does not help. To get the atmosphere to help you need to enter at a shallow angle, where you can stay in the upper reaches of the mesosphere for long enough to let drag do its work without incinerating you. This would be something like the minimum energy solution I described earlier - or more likely an orbit with a periapsis at an altitude of 100 to 150 km or something similar.

Alternately, you can kill off much of your orbital velocity so the projectile enters the atmosphere at a much lower speed - similar to the method I described earlier, with the projectile dropping straight down.

For what it is worth, a projectile given 2 km/s delta-V straight down from a spacecraft in a circular 200 km altitude orbit above airless Earth will have a surface track distance of 781 km before impact, and will take 100.25 seconds for impact. It will hit with a speed of 8.275 km/s.

With an atmosphere, of course, it disintegrates long before reaching the ground.

Isaac Kuo

Luke Campbell, ICBM warheads reenter the atmosphere at steep angles at orbital speeds. This lets them reach their targets more quickly, which was considered important for trying to take out enemy launch sites before the enemy had time to react (by launching their nukes).


On March 1, Russian President Vladimir Putin provided details, mostly in the form of artist’s impressions, on a variety of provocative weapon systems under development. One of them, the RS-28 Sarmat, was depicted as placing a nuclear weapon into a presumably orbital trajectory that could strike targets by traveling the long way around the globe (in this case, with fictionalized land masses, but later depicted as descending on Florida).

The US State Department condemned the development of Russia's new weapon systems as violations of the Intermediate-Range Nuclear Forces (INF) Treaty but did not allege a violation of Article IV of the UN 1967 Outer Space Treaty (OST).1 Why?

The answer may be in part because, 50 years ago, the Johnson Administration set the precedent that testing such a weapon system would not be a violation when it stated publicly that the Soviet Union’s “Fractional Orbital Bombardment System (FOBS),” based on the predecessor to the RS-28, did not violate the treaty. Before and after the treaty’s signing, the administration internally debated the activities it would permit and their ability to verify compliance, ultimately concluding that the treaty was intended to prohibit a different type of weapon system.

A binding prohibition

Article IV requires signatories “not to place in orbit around the Earth any objects carrying nuclear weapons or any other kinds of weapons of mass destruction, install such weapons on celestial bodies, or station such weapons in outer space in any other manner,” among other prohibitions. The US and USSR had already publicly stated their intention not to station nuclear weapons in space, on the Moon, or on other celestial bodies in 1963 through UN Resolution 1884, but because the 1963 statement was not legally binding, the US was not obligated to verify that the USSR was honoring the agreement. By contrast, in preparation for the legally binding 1963 Partial Nuclear Test Ban Treaty, which prohibited exo-atmospheric nuclear testing, the US deployed the Vela surveillance satellites to detect the characteristic radiation from exo-atmospheric (and later, atmospheric) nuclear explosions.

In fact, the Soviets only agreed to the 1963 proposal on the condition that measures such as pre-launch inspection of payloads would not be required, and that the US would be satisfied by using its own national technical means for verification. However, elevating the 1963 statement to a legally binding instrument raised questions about the US ability to verify that other countries were in compliance, and events soon after the signing forced them to consider what would constitute a violation.

Establishing a threshold for violation

Two incidents in 1967 forced the Johnson Administration to establish a threshold for violation of the treaty that hinged on the interpretation of placing nuclear weapons in orbit around the Earth or stationing such weapons in outer space.

The first incident was in response to a June 1967 New York Times article reporting alleged Pentagon plans to develop a nuclear-tipped orbital ABM system. The State Department, who was generally tasked with interpretation of the treaty, stated internally that such a system would violate the treaty because it permanently stationed nuclear weapons in orbit, and it would be impossible to differentiate offensive from defensive orbiting nuclear weapons.2 The explicit inclusion of nuclear weapons in Article IV in addition to weapons of mass destruction prevented the introduction a loophole that the Joint Chiefs of Staff had sought in the 1963 statement in order to allow developing just such an ABM system.3

The second incident was in November 1967—a month after Congress ratified the treaty--when Secretary of Defense McNamara announced that the Soviets had tested a FOBS. The weapon consisted of a modified R-36 missile (the R-36ORB) that placed a two- to three-megaton warhead into an orbital trajectory over the southern hemisphere in order to evade US early warning radar (and possibly ABM) systems by flying lower and approaching from the south, using a retrorocket to de-orbit itself.4 When Secretary McNamara announced the tests, he argued that they did not violate the treaty because 1) they did not involve a warhead, so no nuclear weapon entered orbit; 2) the test vehicle was de-orbited before it achieved a full orbit; and 3) weapon development was not prohibited by the treaty.5

Yet Secretary McNamara’s interpretation angered some members of Congress, who argued that the FOBS represented a violation and questioned Soviet commitment to the treaty. US allies also privately raised concerns, and US the intelligence community suggested it could presage development of a multi-orbit bombardment system. State Department officials, who had not been notified in advance about Secretary McNamara’s announcement, argued internally that nothing in the treaty limited it to full orbits. This internal discord was picked up and reported by the famous Murrey Marder at the Washington Post in a pointed piece titled “Orbital Bomb Rationalizing Jolts Officials.”6

But the State Department was overruled and subsequently adopted the administration’s position, later noting that even if the tests had involved a nuclear weapon, they would not be considered a violation because a “true” orbital bombardment system was imagined to station nuclear weapons in orbit on a more permanent basis.7 Even the name, FOBS, was carefully employed to ensure that the weapon would not be considered a violation.

So it was that the Johnson administration set the bar in 1967: violation would need to entail space-based nuclear weapons, not ground-based systems that temporarily placed prohibited weapons into orbit. This interpretation owed more to the administration’s other needs—in particular, the need for Soviet cooperation to finalize the far more consequential Nuclear Non-proliferation Treaty—than to a close reading of the text or concern about space-based weapons. However unlikely it was that space-based nuclear weapons would be deployed, government officials nevertheless dutifully prepared for verifying compliance with this prohibition.

Inferring the right to inspect satellites

The treaty does not include an explicit permission for inspection of spacecraft to ensure compliance. During negotiations in 1966, the US delegation pushed for all facilities on celestial bodies to be open to all parties, akin to the 1958 Antarctic Treaty, but the Soviets resisted on the grounds that such access could be unsafe, and that access should only be permitted on a pre-arranged, reciprocal basis. The US delegation eventually accepted this limitation under the belief that any effort to evade inspection on these grounds would be obvious.8

Neither the US nor the USSR proposed requiring or even allowing access to spacecraft in orbit, and no such measure was included in the treaty—and in fact, US negotiators were instructed to abandon the talks if access to satellites became a requirement.

As a result of this omission, the US had to establish that the treaty did not prohibit inspection of spacecraft for the purpose of verifying treaty compliance. Consequently, Johnson administration officials argued that the treaty implicitly permitted the use of national technical means to verify compliance:

Thus, provided the close inspection does not involve “potentially harmful interference with activities of other States Parties in the peaceful exploration of outer space,” there is no prohibition against such action. In this context, visual inspection would not be considered as “potentially harmful.” Furthermore, a “bomb-in-orbit” would not be regarded as peaceful and therefore there would be no restraints against inspecting it.9

A more detailed interpretation reasoned that while the treaty did not generally permit physical access to satellites, it “does not contain any provision prohibiting steps to ascertain whether there has been a violation... If any presumption against a right of inspection is raised... this would be overcome if there were strong reason to believe that an orbiting space vehicle was carrying a prohibited weapon,” at which point other rights afforded to states under international law, such as self-defense, would take precedent. Any state would be entitled to challenge a state suspected of violating the treaty, and if doubts could not be addressed, “to take appropriate steps to protect itself against the effects of a Treaty violation.”10

Looking for “bombs-in-orbit”

The administration maintained publicly that the US possessed capabilities for verifying compliance with the treaty that were “sufficient for national security.”11 But the Joint Chiefs of Staff dissented in 1966, noting that while they accepted the treaty, “the United States does not now have the capability to verify the presence of weapons of mass destruction in orbit. The Joint Chiefs of Staff are seriously concerned about this lack of verification capability, and they believe that continued effort should be expended toward its attainment.”12 Although the Air Force did possess a system for the visual inspection of satellites known as Project 437 available by at least 1965, as Dwayne Day has pointed out it had limited capabilities and was cancelled soon after.13 Their dissent may have been due in part to a belief that a binding treaty presented opportunities to advocate for systems such as the Air Force’s planned Manned Orbiting Laboratory (MOL).

A February 1967 memo to prepare for questions from Congress noted that the US could detect all satellites, including a “bomb-in-orbit,” very easily at low orbits, and that higher orbits such satellites would have comparatively long time de-orbiting times. They also noted that they had “a very high confidence of being able to detect a satellite when it is launched” and that a number of ground-based radar and laser facilities under development would add to this capability.14

The memo added, however, that distinguishing nuclear weapon-carrying satellites still posed a significant technical challenge and a disguised weapon could be impossible to be identify. As a contingency, capabilities for physical inspection of spacecraft and facilities were evaluated. The Department of Defense reported that Gemini spacecraft had demonstrated the capability to rendezvous with satellites, and proposed that the MOL could be called on to conduct inspection missions within its limited delta-V. NASA did not volunteer any specific systems but noted many difficulties if it was called on to inspect satellites, including “the availability of ‘booby trap’ devices in the spacecraft to be inspected,” and concluded that “it appears that inspection capabilities in space could be limited.”15

Interestingly, NASA also considered their ability to inspect facilities on the lunar surface, since they were the only agency with the means to do so, even though they had not yet landed astronauts on the Moon. In the extremely unlikely scenario that they would be called on to inspect lunar facilities, NASA noted that: “for the present our manned inspection capabilities are essentially limited to the equatorial plane of the moon but with an accuracy to target area which is expected to be some hundreds of feet and an extravehicular range up to one-half mile. The basic capability through lunar orbiter photographic reconnaissance seems very good, with resolution of one foot and the ability to cover any spot on the moon.”16

Despite technical limitations, the administration concluded in 1966 that they maintained capabilities sufficient for national security because ultimately:

A single weapon in space would not upset the [strategic] balance. “Bombs in Orbit” are complex weapons systems which to be practicable involve large numbers of weapons and associated supporting activities. It would be extremely difficult to conceal such a program. When viewed in this light, it is clear that our national capabilities will provide us the necessary information for protecting our security interests. The real verification question hinges on our ability to know of an adversary’s space activities in sufficient depth to take the necessary actions prior to his attaining any strategic advantage through the weapons-in-space route. This is clearly within U.S. capabilities.17

A later memo to the Secretary of Defense asserted more directly that national capabilities would ensure that compliance with the treaty could be effectively monitored and admitted that while a small number of nuclear weapons could be orbited without detection, a large number could be easily detected.18

Does the Johnson Administration’s interpretation of 50 years ago still stand? No action taken so far after Putin’s address suggests that the current administration has adopted a more restrictive stance. But how this interpretation may have changed in the intervening half century, particularly in relation to some of the proposals of the Strategic Defense Initiative, and with the emergence of new actors and technologies (and artist’s impressions), awaits further research.


  1. State Department. Department Press Briefing - March 1, 2018.
  2. Leonard Meeker to Paul Warneke, ‘Outer Space Treaty and ABM Systems,’ 7 June 1967, Legislative Background Outer Space Treaty History Box 2, Folder “The Senate Considers the Treaty and Gives its Advice and Consent,” LBJ Library.
  3. Raymond Garthoff, A Journey through the Cold War: A Memoir of Containment and Coexistence, Brookings Institution Press: Washington, DC, 2001, p. 162.
  4. Asif Siddiqi, “Cold War in Space: A Look Back at the Soviet Union,” Spaceflight vol. 40, February 1998.
  5. ‘News Conference of Secretary of Defense Robert S. McNamara at Pentagon,’ 3 November 1967, National Security File, Files of Charles E. Johnson, Box 11, Folder 4 “Bombs in Orbit – General (Ballistic missiles in orbit, FOBS, MOBS, etc),” LBJ Library.
  6. Murrey Marder, “Orbital Bomb Rationalizing Jolts Officials,” Washington Post, November 5, 1967.
  7. Dean Rusk to US mission NATO, November 1967, National Security File, Files of Charles E. Johnson, Box 11, Folder 4 “Bombs in Orbit – General (Ballistic missiles in orbit, FOBS, MOBS, etc),” LBJ Library.
  8. Arthur Goldberg to State Department, 4-7 October 1966, LBJ Library.
  9. John S. Foster, “Memorandum for the Assistant Secretary, ISA,” February 2, 1967, Legislative Background Outer Space Treaty History Box 1, Folder 12, “The Treaty is Open for Signature and Goes to the Senate for Advice and Consent,” Folder #2, LBJ Library.
  10. “Memorandum of the Legal Adviser,” April 13, 1967, Box I:46, “The Papers of Arthur Goldberg,” Folder 3, Library of Congress.
  11. No title, January 16, 1967, Legislative Background Outer Space Treaty History Box 1, Folder 10, “The Treaty,” LBJ Library.
  12. “Talking Paper for the Chairman, JCS, fur [sic] use at a meeting of the National Security Council on 15 September 1966,” September 15, 1966, “Legislative Background Outer Space Treaty History Box 1, Folder 9, “The Second and Final Negotiations,” LBJ Library.
  13. Day, Dwayne. “Close encounters of the top secret kind.” The Space Review, October 20, 2014.
  14. Foster, “Memorandum for the Assistant Secretary, ISA,” LBJ Library.
  15. “Inspection,” undated, Folder, “Outer Space Treaty (1962) – NASA response and comments to Proposed Treaty, 17368,” NASA History Office archives.
  16. “Inspection,” NASA History Office archives.
  17. “Verification of the ‘No bombs in Orbit’ Portion of the Space Treaty,” December 28, 1966, Legislative Background Outer Space Treaty History Box 1, Folder 10, “The Treaty,” LBJ Library.
  18. “Memorandum for the Secretary of Defense,” February 9, 1967, Legislative Background outer Space Treaty History Box 2, Folder “The Senate Considers the Treaty and Gives its Advice and Consent,” LBJ Library.

Project Thor

Back before he was a science fiction author, Dr. Jerry Pournelle was working in operations research at Boeing. There he came up with the concept for Project Thor, aka "Rods from God". The USAF calls them "hypervelocity rod bundles.

(so it is not true that Project Thor was "invented by a science fiction writer", Dr. Pournelle had not yet started his writing career when he created it)

The weapons are rods of tungsten, ranging in size from that of a crowbar to that of a telephone pole (about 12 meters for all you young whipper snappers who have never seen a land-line phone). Each one has a small computer in the rear and control fins on the nose, i.e., they are dirt cheap and can be mass produced. Boost them into orbit, and each one can be deorbited to strike a specific target anywhere on Earth in a few minutes, striking it at about 3 to 9 kilometers per second. This is equal to 1 to 3 Ricks worth of damage, which means the unfortunate target will be on the receiving end of the equivalent of 3 kilograms of TNT for each kilogram of tungsten rod from god. Not bad for a crowbar. Especially since they are not covered under the SALT II treaty.

A 2003 USAF report describes rods that are 6.1 m × 0.3 m tungsten cylinder The report says that while orbital velocity is 9 kilometers pre second, the design under consideration would have slowed down to about 3 kilometers per second by the time it hit the target. The report estimates that the rod will impact with a force of 11.5 tons of TNT. The back of my envelope says that a cylinder that size composed of pure tungsten will have a mass of 8.3 metric tons, but the figures in the USAF report imply that the rod has a mass of 8.9 metric tons. Which is close enough for government work.

11.5 tons of TNT per rod is pretty pathetic, you might as well use a conventional bomb. This is because 3 kilometers per second is 1 Rick, which means each kilogram of rod is equal to one kilogram of TNT, so why not just drop TNT from a conventional bomber?

An article in Popular Science breathlessly suggests that the rods will strike the target at 11 kilometers per second. This is 13.4 Ricks, which will give the rod an impact of 120 metric tons of TNT. That's more like it, now we are getting into tactical nuclear weapons levels of damage. But the article does not explain how the rod is suppose to start at 9 km/s and strike at 11 km/s after being slowed by atmospheric friction. Popular Science left that as an exercise for the reader. Or as proof of questionable research.

The rod is admittedly quite difficult for the enemy to defend against. It is moving like a bat out of hell, er, ah, has a very high closing velocity, and it has a tiny radar cross section.

The trouble is, the "plasma sheath" created by atmospheric re-entry prevents remote control of the rod. Radio cannot pass through the plasma, so the bar has to be inertially guided. Or not. A Russian scientist thinks they have found the key to allowing radio signals to pass through the plasma sheath. A related problem is that anything on the rod that is not made of tungsten is going to want to burn up in re-entry. Things like the guidance computer, sensors, and hypothetical remote control radio.

The main drawback to Project Thor is the prohibitive cost of boosting the rods into their patrol orbits. Of course if you have a space-faring civilization, the rods can be manufactured already in orbit, thus eliminating the boost cost. Which means any planetary nation without a presence in space is going to be at a severe disadvantage, but that is always true.

Another problem is maintaining the rods in orbit. Things are going to break down, so you either have to have a budget to boost replacements or have assets in orbit that can do maintenance.

Finally, no, this is not the same as the Magnetic Accelerator Cannon from the Halo games. That is a coil gun, Project Thor is more like a weaponized version of dropping a penny from the top of the Empire State building.

Predictably, some maniac made a "Rods from God" mod for the game Kerbal Space Program.


The basic weapon system consists of an orbiting element some 20 to 40 feet long. It requires a GPS receiver to locate itself; a means of taking it out of orbit; an atmospheric guidance system, such as a means of changing its center of gravity (moving weights, small fins, etc.), and a communication system to give it a target and activate the system. No warhead is wanted or needed. Thor will impact a target area at about 12,000 feet per second (3.7 km/s); that is sufficient kinetic energy to destroy most hard targets, with minimum collateral damage and of course no fall-out. Achievable accuracy has been estimated at ten to twenty feet CEP.

ed note: CEP is Circular Error of Probablility. It is the radius of a circle inside of which 50% of the missiles will fall.


      One of the most difficult security missions which the United States must accomplish is the protection of our interests around the globe. Incidents like the North Korean seizure of the USS Pueblo have demonstrated our weakness in not being able to respond quickly and authoritatively in remote locations. Our only solution to this problem so far has been the naval carrier task force. Carrier-based aircraft can project military force to protect our citizens and allies in remote regions of the world. Unfortunately, the high cost and vulnerability of nuclear carriers and their required aircraft and support fleets make them an unattractive solution.
     We now have the technology to produce a space-based weapon system which can perform the same mission for less cost. The space system is also much less vulnerable and can respond faster to any location on the globe than a dozen carrier task forces spread throughout the oceans of the world. The proposed name for this weapon is THOR, for it would literally give the United States the power to call down lightning bolts from the heavens upon its enemies.

Brief Description of THOR

     The basis of the THOR weapon system is the fundamental nature of any object orbiting the Earth. To balance the force of gravity, a satellite two hundred miles above the surface must travel at a speed of seventeen thousand five hundred miles per hour. At this speed, the satellite travels around the Earth once every ninety minutes. With a hundred satellites in orbits near this altitude and traveling in random orbital inclinations, one of the satellites will pass over any given location on Earth every thirty minutes. With a thousand satellites, the timing between satellites overhead is less than ten minutes. The basic physics of orbital motion gives us our global coverage; it also gives us the weapon. The extremely high velocity of a satellite in orbit gives it a tremendous amount of kinetic energy. If a one pound object moving at orbital velocity ran into a stationary target, the energy released in the impact will be the equivalent of exploding almost ten pounds of TNT.
     The THOR system is composed of a thousand or more cheap satellites, each made up of a bundle of projectiles, guidance and communications electronics, and a simple rocket engine. When a crisis arises, a THOR command center (on Earth or in space) sends a signal to the appropriate THOR satellite. The satellite then orients itself. At the proper time, the rocket engine fires to deorbit the satellite. When the rocket engine burns out, the individual THOR projectiles are dispersed from the satellite in a prearranged pattern. Instead of blunt noses, the projectiles have sharp points which slice down-through the atmosphere, losing little velocity. Just seconds before impact, a (relatively dumb) terminal guidance sensor looks for a metallic or other preprogrammed target and steers toward it. The result is spectacular: a bundle of tens or hundreds of twenty pound projectiles streak down at four miles per second to strike targets with the explosive equivalent of two hundred pound bombs each. In five seconds the action is over, and the enemy doesn’t know what hit them. All that remains is dozens of luminous trails, each angling downward to a slowly dissipating explosion cloud.
     The major advantage of the THOR space weapon is its capability for quick response while remaining highly survivable. Even if an enemy were to detonate one or more nuclear devices in space in an attempt to destroy THOR, there are a thousand or more widely scattered satellites he must destroy. Because the satellites are at different altitudes and have different orbital inclinations, any holes produced in the global coverage by a nuclear explosion are filled in after several hours by the orbital motions of the satellites.
     An individual THOR satellite is not easy to detect or to destroy. The satellite can be cocooned in foam, which would be difficult to detect with radar anyway and could be shaped to make detection even more difficult (stealth satellites!). The foam would insulate the satellite against the heat and shock of nuclear explosions or laser beams. All the satellite has to do is float around in its orbit and wait for the command to strike a target.
     Each individual projectile is a slender, dense metal rod. No explosive or firing mechanism is necessary. The jet of metal particles produced when a shaped charge warhead detonates is traveling at about the same velocity as a THOR projectile when striking a target. The six-inch diameter warhead from a TOW anti-tank missile will punch through the armor of a heavy tank. The jet of metal from the TOW warhead weighs only a fraction of an ounce; a THOR projectile weighs over twenty pounds! Such a projectile can easily punch through the deck of a battleship and blow a hole through the bottom, blast a crater in a runway, or destroy a bunker. A rain of a hundred THOR projectiles over an area less than a mile across would stop an armored column, halt an amphibious landing, or destroy a supply depot.
     The capability of the THOR projectile is not limited to armored targets. Forming the projectile from dense uranium metal produces an incendiary blast when the white hot metal vapor produced on impact ignites in the air. Such a uranium missile could penetrate the reinforced concrete cover of a missile silo and explode inside as the cloud of uranium vapor detonates. If the projectile were composed of an outer shell with sand-sized particles inside, it could be designed to explode and disperse the particles just before impact. The metal particles would instantly vaporize, with the resulting shock wave flattening troops, aircraft, or other targets much like the fuel-air explosive bombs presently in service.

Advantages of the THOR Space Weapon

     The advantages of the THOR weapon system are its low cost, global coverage, quick reaction time, and survivability. Unlike an aircraft carrier task force, THOR does not need thousands of highly trained pilots, sailors, and technicians who must spend long months away from home. THOR does not require expensive foreign aid payments to secure overseas bases. THOR does not have a single capital ship as a vulnerable target. THOR is composed of many cheap, hardened satellite packages which act only on command. The system capabilities can be built up slowly but can act quickly in a crisis. All of the system’s capability is useful; none of the projectiles need to be stockpiled or stored and then shipped to the battlefront.
     No major (and vulnerable) ground facilities are necessary, unlike ballistic missiles with silos or other fixed launchers. Every time the Space Shuttle goes up with the payload bay partially full, we could toss in a THOR satellite or two and build up the system gradually and cheaply. The command stations and links for THOR could use multiple channels, existing relay satellites, and several orbital or ground control stations.
     THOR gives global coverage at a time when we are uncertain from one minute to the next where a crisis may erupt. THOR is non-nuclear and surgically precise. The velocity of the projectiles is so high that interception would be impossible before they strike their targets. Before our enemies can react, THOR has struck them down.

Further Study of THOR

     Several aspects of the THOR space weapon system must be studied before any commitment to development of the system can be made. Some are strategic, some are political, and some are technical.
     We should begin to consider the effects which the existence of the THOR system would produce on our own and our opponents’ defense planning. A firm commitment to the THOR system would involve billions of dollars of defense funds. It will be opposed by those with vested interests in the current weapons systems which THOR might replace and those who oppose any change, whatever the justification. As benefits, THOR may permit the United States to reduce conventional forces in Europe and decrease the number of large carriers built.
     We must consider the impact of THOR on world politics. We would not want to register the orbital parameters of each THOR satellite with the U.N. as is presently required by treaty. The Soviets might consider THOR a strategic weapon aimed at the destruction of their land and sea based ICBM’s. Many countries might object to our umbrella of military power covering the entire planet (others might welcome it).
     If THOR is to be survivable against present and future threats, the THOR satellites must be difficult to detect and to destroy. The shape and composition of the external covering of the satellites must be chosen for low electromagnetic detectability, resistance to orbital temperature extremes, and strength to withstand laser and nuclear attacks. A plastic foam mixed with a refractory material such as aluminum oxide might have the necessary properties.
     The angle at which the THOR projectiles strike determines the size of the de-orbit propulsion system for each THOR satellite. The maximum penetration of hardened targets such as missile silos and underground bunkers would be achieved with projectiles striking almost vertically. Ships and lightly armored targets could be destroyed with projectiles entering at more shallow angles. The steeper the angle of attack, the less time the projectiles spend in passing through the atmosphere and the greater the speed and accuracy of the projectiles will be. To de-orbit the projectiles and bring them down at an angle of thirty degrees from vertical requires almost as much energy as was required to orbit the projectiles initially, and requires a large quantity of propellant for each THOR satellite.
     The de-orbit propulsion system must be capable of long-term storage in orbit without deterioration, yet it must provide a precise change in velocity to strike the target area. The individual THOR satellites are most vulnerable while the de-orbit propulsion burn is taking place, when a rocket exhaust plume is a bright beacon marking the location of the satellite for possible destruction by enemy laser weapon satellites. Two solutions are a cold gas propulsion system (high weight of propellant required) or a very fast propulsion impulse which ends before the laser weapon could be brought to bear on the THOR satellite. Once the propulsion burn has occurred, the individual projectiles are dispersed and are then relatively invulnerable to attack or interception before impact (after all, they are rods of solid metal with a simple terminal guidance system).
     The individual guidance system of each THOR satellite must know its own position very accurately to orient itself to strike the target from orbit. If the command message carries only the target coordinate information, the THOR satellite must be able to compute from this data the proper trajectory to follow to hit the commanded target. Fortunately, computers capable of doing this are small and cheap enough to put in every THOR satellite. With the Global Positioning System navigation satellite network in operation, each satellite could passively receive its own location in space to a very high accuracy while doing nothing to reveal its own position.
     The navigation and command communication system must resist jamming, have secure codes to prohibit enemy takeover of the satellite, be hardened against extremely intense visible or radio-frequency pulses or beams, and permit almost instant reception of the targeting commands. This may be accomplished by multiple ground control stations, multiple space control stations, relay satellites operating on optical or radio frequencies which cannot penetrate the Earth’s atmosphere, and redundant channels of communication spread across the electromagnetic spectrum. Communication by laser beams, which are extremely narrow and almost impossible to intercept, may be possible if the position of each of the thousand or more THOR satellites can be calculated accurately enough to hit the desired satellite.
     The command and control stations must receive the signal from the military commanders containing the target location, calculate which THOR satellite is in the best location to strike the target, and transmit the command to the THOR satellite. The most difficult part of the task will probably be to devise a system to monitor the location of all the satellites in the THOR system without compromising their locations to the enemy. Each satellite may transmit its current position after random intervals to notify the control centers of its updated orbital characteristics (in coded form).
     The projectiles themselves must survive passage through the atmosphere without being damaged or slowed significantly and then home in on an individual target in the target zone. The projectile could be protected by an ablative nose tip which would vaporize and carry off the heat from atmospheric friction during the few seconds of atmospheric passage. At a mile or two above the surface, the nose cap would pop off to expose the sensor(s). Small bumps or tabs at the rear of the projectile would steer the projectile to the target. The projectile itself would be as small in diameter as possible for stability and minimum friction and slowing during high velocity travel through the atmosphere, and to produce a very high cross-sectional density for increased depth of penetration on impact. A twenty pound projectile made of tungsten or uranium would be less than an inch in diameter and three or four feet long. The sensors would only have to detect metal or color contrasts or some other relatively simple targeting strategy. Only ten per cent might hit their targets with such a simple guidance logic, but a bundle of a hundred or more would give enough hits to be effective.
     The high speed of the projectile through the atmosphere near the ground where the density of the air is highest would produce a luminous bow shock wave directly in front of the missile. Penetrating such a layer might be a problem, but high frequency radio waves, infrared light, visible light, or ultraviolet light might be effective for targeting. A visible light sensor might have a window covered with a filter which passes light of a wavelength which is not emitted by the ionized air in the shockwave. Many new solid-state sensors are now available which detect almost all portions of the spectrum and which can be encapsulated in a shock resistant module.
     The individual THOR projectiles may home in on targets according to preselected characteristics, or targets may be designated using lasers to pinpoint enemy ships surrounding a friendly ship as an example. Characteristics used to select targets in present military weapons include contrast and shape of the target against its background in visible light, long-wave infrared (heat) radiation, and ultraviolet light; reflection of millimeter radio waves from the sky by metal surfaces; and designation of targets with visible or infrared lasers. Coding of laser designator beams would be required to avoid enemy countermeasures. Target designation could be carried by nearby friendly forces, by aircraft, or from orbit by manned or unmanned platforms. Each THOR satellite might carry a mix of sensor tips on its projectiles to insure effectiveness in striking targets, or each satellite might have two de-orbit modules, one with passive sensors for broad targets such as invasion forces, and another with laser designator sensors for precise targeting near friendly forces.
     The THOR system should be studied. None of the technical problems appear to be insoluble. The strategic and cost benefits to our country may be enormous.


A kinetic bombardment or a kinetic orbital strike is the hypothetical act of attacking a planetary surface with an inert projectile, where the destructive force comes from the kinetic energy of the projectile impacting at very high velocities. The concept originated during the Cold War.

The typical depiction of the tactic is of a satellite containing a magazine of tungsten rods and a directional thrust system. When a strike is ordered, the satellite would brake one of the rods out of its orbit and into a suborbital trajectory that intersects the target. As the rod approaches periapsis and the target due to gravity, it picks up immense speed until it begins decelerating in the atmosphere and reaches terminal velocity shortly before impact. The rods would typically be shaped to minimize air resistance and maximize terminal velocity. In science fiction, the weapon is often depicted as being launched from a spaceship, instead of a satellite.

Kinetic bombardment has the advantage of being able to deliver projectiles from a very high angle at a very high speed, making them extremely difficult to defend against. In addition, projectiles would not require explosive warheads, and—in the simplest designs—would consist entirely of solid metal rods, giving rise to the common nickname "Rods from God". Disadvantages include the technical difficulties of ensuring accuracy and the prohibitively high costs of positioning ammunition in orbit.

The Outer Space Treaty is designed to prohibit weapons of mass destruction in orbit or outer space; however, its text does not formally define what constitutes a weapon of mass destruction. Since the most common form of kinetic ammunition is inert tungsten rods, it is uncertain if kinetic bombardment is not prohibited by treaty.

Real life concepts and theories

During the Vietnam War, there was limited use of the Lazy Dog bomb, a steel projectile shaped like a conventional bomb but only about 25.4 mm (1") long and 9.525 mm (3/8") diameter. A piece of sheet metal was folded to make the fins and welded to the rear of the projectile. These were dumped from aircraft onto enemy troops and had the same effect as a machine gun fired vertically. Observers visiting a battlefield after an attack said it looked like the ground had been 'tenderized' using a gigantic fork. Bodies had been penetrated longitudinally from shoulder to lower abdomen.

Project Thor is an idea for a weapons system that launches telephone pole-sized kinetic projectiles made from tungsten from Earth's orbit to damage targets on the ground. Jerry Pournelle originated the concept while working in operations research at Boeing in the 1950s before becoming a science-fiction writer.

The system most often described is "an orbiting tungsten telephone pole with small fins and a computer in the back for guidance". The system described in the 2003 United States Air Force report was that of 20-foot-long (6.1 m), 1-foot-diameter (0.30 m) tungsten rods, that are satellite controlled, and have global strike capability, with impact speeds of Mach 10.

The time between deorbit and impact would only be a few minutes, and depending on the orbits and positions in the orbits, the system would have a worldwide range. There would be no need to deploy missiles, aircraft or other vehicles. Although the SALT II (1979) prohibited the deployment of orbital weapons of mass destruction, it did not prohibit the deployment of conventional weapons. The system is not prohibited by either the Outer Space Treaty or the Anti-Ballistic Missile Treaty.

The idea is that the weapon would naturally contain a large kinetic energy, because it moves at orbital velocities, at least 8 kilometers per second. As the rod would approach Earth it would necessarily lose most of the velocity, but the remaining energy would cause considerable damage. Some systems are quoted as having the yield of a small tactical nuclear bomb. These designs are envisioned as a bunker buster. As the name suggests, the 'bunker buster' is powerful enough to destroy a nuclear bunker. With 6–8 satellites on a given orbit, a target could be hit within 12–15 minutes from any given time, less than half the time taken by an ICBM and without the launch warning. Such a system could also be equipped with sensors to detect incoming anti-ballistic missile-type threats and relatively light protective measures to use against them (e.g. Hit-To-Kill Missiles or megawatt-class chemical laser).

In the case of the system mentioned in the 2003 Air Force report above, a 6.1 m × 0.3 m tungsten cylinder impacting at Mach 10 has a kinetic energy equivalent to approximately 11.5 tons of TNT (or 7.2 tons of dynamite). The mass of such a cylinder is itself greater than 9 tons, so the practical applications of such a system are limited to those situations where its other characteristics provide a clear and decisive advantage—a conventional bomb/warhead of similar weight to the tungsten rod, delivered by conventional means, provides similar destructive capability and is far more practical and cost effective.

The highly elongated shape and high mass are to enhance sectional density and therefore minimize kinetic energy loss due to air friction and maximize penetration of hard or buried targets. The larger device is expected to be quite effective at penetrating deeply buried bunkers and other command and control targets.

The weapon would be very hard to defend against. It has a very high closing velocity and small radar cross-section. Launch is difficult to detect. Any infrared launch signature occurs in orbit, at no fixed position. The infrared launch signature also has a much smaller magnitude compared to a ballistic missile launch. One drawback of the system is that the weapon's sensors would almost certainly be blind during atmospheric reentry due to the plasma sheath that would develop ahead of it, so a mobile target could be difficult to hit if it performed an unexpected maneuver. The system would also have to cope with atmospheric heating from re-entry, which could melt non-tungsten components of the weapon.

The phrase "Rods from God" is also used to describe the same concept. An Air Force report called them "hypervelocity rod bundles".

In science fiction

In the mid-1960s, popular science interest in orbital mechanics led to a number of science fiction stories which explored their implications. Among these was The Moon Is a Harsh Mistress by Robert A. Heinlein in which the citizens of the Moon bombard the Earth with rocks wrapped in iron containers which are in turn fired from an electromagnetic launch system at Earth-based targets.

In the 1970s and 1980s this idea was refined in science fiction novels such as Footfall by Larry Niven and Jerry Pournelle (the same Pournelle that first proposed the idea for military use in a non-fiction context), in which aliens use a Thor-type system. During the 1980s and 1990s references to such weapons became a staple of science fiction roleplaying games such as Traveller, Shadowrun and Heavy Gear (the latter game naming these weapons ortillery, a portmanteau of orbital artillery), as well as visual media including Babylon 5's "mass drivers" and the film Starship Troopers, itself an adaptation of a Heinlein novel of the same name.

The re-purposing of space colonies for use in kinetic bombardment (referred as a "colony drop") is a frequent element of the Gundam franchise and is central to the plots of Mobile Suit Gundam: Char's Counterattack and Mobile Suit Gundam 0083: Stardust Memory.

A smaller "crowbar" variant is mentioned in David's Sling by Marc Stiegler (Baen, 1988). Set in the Cold War, the story is based on the use of (relatively inexpensive) information-based "intelligent" systems to overcome an enemy's numerical advantage. The orbital kinetic bombardment system is used first to destroy the Soviet tank armies that have invaded Europe and then to take out Soviet ICBM silos prior to a nuclear strike.

In Neal Stephenson's Anathem a kinetic bombardment weapon is deployed from orbit to trigger the eruption of a dormant volcano.

From the mid-1990s, kinetic weapons as science fiction plot devices appeared in video games. Appearing in Bullfrog Productions' 1996 Syndicate Wars as a player-usable weapon, it also featured prominently in the plot of Tom Clancy's Endwar, Mass Effect 2 and Call of Duty: Ghosts, to name some.

The Warren Ellis comic Global Frequency (issue #12, "Harpoon", August 2004) featured the threat of kinetic spears, weapons designed to be dropped from satellites, heat up on re-entry, and strike the ground with the force of a tactical nuke, and as hot as the edge of the sun. Rather than being a weapon of war they were depicted as part of a 'die-back' protocol designed to reduce Earth's human population to a sustainable level.

In Daniel Suarez's book Freedom, a suborbital version of Thor is used composed of many small arrows or spikes for anti-personnel use.

In James S. A. Corey's The Expanse series, a radical group from within the Belter movement bombards Earth with high-speed asteroids, killing billions.

In 2013 a kinetic weapon bombardment system consisting of tungsten rods in an orbiting platform, codenamed Project: Zeus, was featured in the movie G.I. Joe: Retaliation, where it destroys London. However, the movie misrepresented physics by claiming the rod would not be "launched" or "fired" but merely "dropped". If it were released without force it would orbit the Earth in the same manner as the platform itself. In order for a rod to fall straight toward the center of Earth it would need to be launched away from the station with a tangential velocity equal in magnitude and opposite in direction from the orbiting station. This velocity would be in the range of approximately 7–8 km/s for satellites in low earth orbit, however, the actual velocity change needed to merely deorbit within half an orbit would be much less. Likely a few hundred m/s For a low-orbiting satellite, if even that much.

In John Birmingham's Stalin's Hammer (a part of his Axis of Time series), Soviet scientists use 21st century technology obtained from a fleet thrown back to World War II to create a satellite capable of launching tungsten rods from orbit and launch it in early 50's.

In David Weber's Honorverse series, kinetic strike weapons are a standard armament of all space navies that conduct orbit-to-ground operations. The version used by the Royal Manticoran Navy is a six-hundred-kilogram iron slug equipped with a small gravitic drive, capable of variable yields ranging from that of a large artillery shell to an intermediate-yield nuclear device, and packaged in six-shot satellites that are deployed from starship counter-missile tubes.

An episode of Justice league featured a satellite based weapon that combines this with a rail gun which used magnetic coils to attract and then launch meteors toward the earth's surface.

In Peter F. Hamilton's The Night's Dawn trilogy, "kinetic harpoons" are being used to bombard the surface of a planet. The book in which the event occurs also specifies how the staggering of the harpoons impact caused the shockwaves from the impacts to resonate and result in an artificial earthquake.

From the Wikipedia entry for KINETIC BOMBARDMENT

antigravite: Chinese scientists also took an interest in this advanced technology and patented some sort of a similar device as CN106052482B filed on 20160602 but granted on 20171020. The single patent title I found by chance (spent not too much time on it) roughly translates as: "A return to orbit deployment method for space-based kinetic energy weapon strikes area" and is downloadable from here.

Scott Lowther: No doubt. But physics isn't any different for them than for American scientists. It is certainly possible to launch telephone poles of tungsten into orbit, but the same problems remain. Getting them back *down* is no trivial feat. Unlike how these systems are generally portrayed in the movies (like the second "GI Joe" movie), you don't simply "drop" them. You have to *propel* them down from orbit. And given their great mass, adding a few kilometers per second of delta V to them is no trivial feat.

Additionally, the claims that these things pack the punch of nukes is exaggerated to the point of being outright lies. They would hit the ground at less than orbital velocity (how much less is down to trajectory options... if you slow it down only a little bit to get it to de-orbit, it will hit the ground at a relatively shallow angle; if you drop it straight down, then you had to have dumped most of the orbital velocity). LEO circular orbit velocity is about 7,800 m/sec. The density of tungsten is 19.3 grams/cubic centimeter. So a rod 20 cm in diameter and ten meters long would have a volume of 3.14159*(10^2)*1000 = 314,159 cubic cm => 6,063 kg. Having six metric tons whack you upside the head at 7.8 km/sec would be harsh, but is it nuke-like? The kinetic energy is 1/2 M*V^2 = .5* 6063 * 7800^2 = 184,436,460,000 joules (184.4 gigajoules). One metric ton of TNT releases 4.184 gigajoules, so this six-ton rod has the equivalent yield of 44.1 metric tons of TNT, a multiple of 7.35.

Keep in mind: in order to drop that six ton rod of tungsten on the other guy, you had to expend a de-orbit stage of unknown mass, as well as a whole lot of tons of rocket propellant to boost the system into orbit in the first place. The Falcon 9 Full thrust can put 22.8 tons into orbit (equivalent to 3.75 rods, not counting de-orbit it three rods), burning through 410.9 tons of propellant in the first stage and 107.5 tons of propellant in the second => 518.4 tons of propellant expended to deliver the equivalent of 3X44.1 tons (132.3 tons) of TNT onto the enemy.

An entire Falcon 9 delivers a maximum of 0.13 kilotons of destructive potential upon the enemy using "Thor." Alternatively, you could load up that Falcon Nine with a couple hundred megatons of thermonuclear sunshine.

Avimimus: (i.e. it isn't that impressive an idea).

Scott Lowther: Actually it would be an impressive weapon. Someone on the ground would have very little time to react to it if they detected it at all (if it begins entry-heating to incandescence at 100 km altitude and it's coming in at a shallow angle so it has to cross 200 kilometers and it maintains, say, 7 km/sec, an observer could potentially see it as an incoming glowing spark for about 29 seconds), and even if it was detected there's not a lot that could be done to stop it: hit-to-kill smart rocks would likely just spang off the side of the thing. And when it hit it would make a hell of a mess. Claims of being able to penetrate deeply are generally overblown, but one of these things bullseying a battleship would like to cut it in half.

It's just a terribly impractical weapon. The cost is immense, and the tactical utility is poor: how many times in a day would the thing be anywhere near the target?

Avimimus: tungsten would allow a higher terminal velocity I suppose.

Scott Lowther: The high density and high temperature would allow a tungsten rod to punch deeper, faster. The drag would be the same as for a rod of the same size and geometry made out of concrete, but the density increase means increased mass but with the same cross-sectional area.

Avimimus: The main benefit compared to your 'couple hundred megatons' is, well... considerably reduce fallout? Right? That is a thing?

Scott Lowther: A tungsten rod would produce no fallout, since there are no radiologicals involved. Unless it's targeting a nuclear site of some kind.

Avimimus: Also, I suppose one could get more power from the tungsten stick if it was in a highly elliptical orbit, right?

Scott Lowther: Correct. As well as a more perpendicular strike on the surface, assuming that the de-orbit burn was carried out much further out.

If you manufactured it further out in space you wouldn't have to climb the gravity well either.

In all likelihood, well-developed asteroid mining processes will simply chew up space rocks and separate the resulting fine powders by the elemental compositions (rather than following veins of material through the asteroid, since those are unlikely to exist as such). So metallic asteroids might give you X tons of iron, Y tons of nickel, and Z kilograms of uranium and tungsten in separate bins.

The problem with Thor weapons in deep space is that Thors are meant to take out reasonably precise targets... ships, tanks, bunkers. The likelihood of targeting such systems from beyond the moon is low. Deep-space kinetic bombardment is more likely to take the form of big rocks. Instead of six tons of precisely aimed tungsten you'll get six million tons of meh-aimed metal-rich rock. Put a ten-mile crater in the ground and not only are you reasonably well assured of taking out the target, you also have deniability. "Gee whiz, me? Naw, musta just been one of them Tunguska sort of things. Sad, really..."

kcran567: The ultimate rock throw would be controlling (adding some type of propulsion and guidance) to space rocks/asteroids the bigger the better. Mountain sized. And then parking it over the enemy whoever that would be. Could destroy an entire continent if possible? But also start an ice age for the entire planet?

Scott Lowther: The point of dropping rocks on people is deniability. Rocks fall on their own, perfectly naturally, as Tunguska and Chelyabinsk showed. If you are going to park a rock in orbit and use it as a threat, you'd be better advised to simply invest in Really Powerful H-bombs in the gigaton range. Because de-orbiting a mountain to drop in within half a hemisphere of the target would be a monumental challenge, and you wouldn't be fooling anyone.

That said: parking a mountain in high orbit is good idea. But to chew it up for resources, rather than as a hammer. You could always mount mass drivers to it to chuck ten-ton bricks of asteroidal nickel/iron at anyone who ticks you off.

Charlesferdinand: Would these tungsten rods lose a lot of their mass through friction by the atmosphere?

Scott Lowther: Not if designed correctly. The nose would probably have an ablative cap.

Charlesferdinand: Also, why rods? Obviously it looks cooler, but wouldn't balls be more convenient and ballistically more effective?

Scott Lowther: Nope. The point is to retain as much velocity as possible, to lose as little of it as possible due to drag. And one simplistic way to look at the drag of ballistic objects is the mass per cross sectional area. So... look at a tungsten rod shaped like a pencil. Each square inch of frontal area might be backed up by ten, fifteen, twenty feet of tungsten. A sphere of the same mass would be considerably larger in diameter, with much less mass per cross sectional area. This is related to why bullets these days are relatively long compared to their diameter... and not musketballs.

From Secret Projects Forum TOPIC: RODS FROM GOD / "PROJECT THOR"

     "One more thing, Mr. President," Curtis said insistently.
     "Today's attack. I suppose you'll be sending in lots of armor."
     The President looked puzzled.
     "We'll do it right, Doctor," General Toland said. He turned to leave. "And I'd like to get at it."
     "Thor," Curtis said.
     Toland stopped. "What's that? It sounds like something I've heard of—"
     "Project Thor was recommended by a strategy analysis group back in the eighties," Curtis said. "flying crowbars." He sketched rapidly. "You take a big iron bar. Give it a rudimentary sensor, and a steerable vane for guidance. Put bundles of them in orbit. To use it, call it down from orbit, aimed at the area you're working on. It has a simple brain, just smart enough to recognize what a tank looks like from overhead. When it sees a tank silhouette, it steers toward it. Drop ten or twenty thousand of those over an armored division, and what happens?"
     "Holy sh*t," Toland said.
     "Are these feasible?" Admiral Carrell asked.
     "Yes, sir," Anson said. "They can seek out ships as well as tanks—"
     "But we never built them," Curtis said. "We were too cheap."
     "We would not have them now in any case," Carrell said. "General, perhaps you should give some thought to camouflage for your tanks—"
     "Or call off the attack until there's heavy cloud cover," Curtis said. "I'm not sure how well camouflage works. Another thing, look out for laser illumination. Thor could be built to home in that way."

ed note: "Anson" is Robert Anson Heinlein. "Curtis" is Jerry Pournelle.

From Footfall by Larry Niven and Jerry Pournelle (1985)

Strategic Nuclear Weapons

As mentioned in the Space War section, nuclear weapons behave quite differently in airless space (and airless planets) than they do in a planetary atmosphere.

On a planet with an atmosphere the x-rays are absorbed by the atmosphere and become thermal radiation and atmospheric blast. The duration of thermal pulse increases with yield from about 1 second for 10 kilotons to 10 seconds for 1 megaton.

In space it is just x-rays and neutrons.

Percentage of total energy
In Atmosphere
Blast40% to 50%
Thermal Radiation30% to 50%
Ionizing Radiation
(Prompt Radiation)
(unless this is a neutron bomb)
(Residual Radiation)
5% to 10%
In Space
Soft x-rays80%
Gamma rays10%

Thermal Radiation

In the tables below the range between the detonation point and the affected target is called the "slant range." If the weapon detonates on the ground this is just the ground distance between the target and the explosion. However, nuclear weapons are commonly detonated at some height above the ground to increase their effect. Given the ground range and the detonation height, the slant range can be calculated by using the Pythagorean theorem:

Thermal Radiation Graph

from Physics and Nuclear Arms Today edited by David Hafemeister (1991)
  • Explosion Yield is the yield of the nuclear weapon in kilotons. 1,000 kilotons = 1 megaton
  • Slant Range is the distance between the target and the detonation point of the weapon, in miles.
  • Curves are thermal flux in calories per square centimeters.

The vertical red line is for 1 megaton (1,000 kilotons). Remember these have a pulse duration of 10 seconds.

  • 5 to 6 cal/cm2 for 10 seconds will cause second degree burns. (green line)
  • 8 to 10 cal/cm2 for 10 seconds will cause third degree burns. (blue line)
  • 20 to 25 cal/cm2 for 10 seconds will ignite clothing. (violet line)

The equation is:

Q ≈ 3000 * ( ƒ * τ * Y / D2 )


Q = thermal flux (cal/cm2)
ƒ = thermal energy fraction ( from 0.35 to 0.40 for air bursts, 0.18 for ground bursts)
τ = atmospheric transmission factor (0.6 to 0.7 at 5 miles, 0.05 to 0.1 at 40 miles. Even lower if foggy)
Y = nuclear weapon yield (megatons). Please note the graph above uses kilotons, not megatons
D = slant range (miles)
EffectsExplosive yield / detonation height
1 kt / 200 m20 kt / 540 m1 Mt / 2.0 km20 Mt / 5.4 km
Thermal radiation—ground range (km)
Third degree burns0.62.51238
Second degree burns0.83.21544
First degree burns1.14.21953
from Wikipedia article Effects of nuclear explosions
Note the table is using ground range, not slant range.


A bit less than half the nuclear weapon's energy becomes atmospheric blast. This has two effects: a sharp increase in atmospheric pressure ("overpressure"), and incredibly strong winds. The overpressure crushes objects and collapses buildings. The wind turns lightweight objects into dangerous projectiles.

In the complicated equations for figuring the area that suffers from a given overpressure, the area is proportional to Y2/3 (where Y is the weapon's yield). This is called the "equivalent megatonnage" of a nuclear weapon. Why do we care? The point is that the combined equivalent megatonnage of several low-yield weapons is greater than that of a single weapon with the same total yield. In other words five warheads (2 megatons each) will do more damage to a city than a single warhead (10 megatons).

OverpressurePhysical Effects
20 psiHeavily built concrete buildings are severely damaged or demolished.
10 psiReinforced concrete buildings are severely damaged or demolished.
Small wood and brick residences destroyed.
Most people are killed.
5 psiUnreinforced brick and wood houses destroyed.
Heavier construction severely damaged.
Injuries are universal, fatalities are widespread.
3 psiResidential structures collapse.
Serious injuries are common, fatalities may occur.
1 psiLight damage to commercial structures
Moderate damage to residences.
Window glass shatters
Light injuries from fragments occur.

Note that the same source says you need 40 psi before lethal effects are noted on people, which contradicts the 10 psi entry above. I don't know which to believe.

Peak overpressureMaximum Wind Velocity
50 psi934 mph
20 psi502 mph
10 psi294 mph
5 psi163 mph
2 psi70 mph
Tables from Atomic Archives

The x-axis is the slant range in feet, divided by the weapon yield in megatons rasied to the 1/3 power. Trace upward to intersect the curve, then to the left to find the peak overpressure in PSI.

The curve can be traced approximately by the formula:

z = Y1/3 / D

p = (22.4 * z3) + (15.8 * z3/2)


z = scaled yield (megatons1/3/mile)
Y = weapon yield (megatons)
D = slant distance (miles)
p = overpressure (lb/in2 or PSI)

EffectsExplosive yield / detonation height
1 kt / 200 m20 kt / 540 m1 Mt / 2.0 km20 Mt / 5.4 km
Blast—ground range (km)
Urban areas completely levelled
(20 psi or 140 kPa)
Destruction of most civilian buildings
(5 psi or 34 kPa)
Moderate damage to civilian buildings
(1 psi or 6.9 kPa)
Railway cars thrown from tracks and crushed
(62 kPa)
(values for other than 20 kt are extrapolated
using the cube-root scaling)
from Wikipedia article Effects of nuclear explosions
Note the table is using ground range, not slant range.

Things are more complicated when the detonation point is some distance above ground level.

The primary shock wave expands outward as a sphere from the weapon detonation point. If this is not a ground-burst, at some point the sphere will expand until it hits the ground. The shock wave is reflected upward from the ground. Since the shocked region inside the sphere is hotter and denser than the rest of the atmosphere, the reflected shock wave travels faster than the primary shock wave. For certain geometries, the reflected shock wave catches up with the primary shock wave and the two shock fronts merge. This is called the Mach Stem. The overpressure at the stem is typically twice that of the primary shock wave.

The area the Mach stem passes over is called the Mach reflection region. The area from ground zero to the start of the Mach reflection region is called the Regular reflection region. It only suffers from the passage of two separate shock waves with the standard overpressure. The Mach reflection region suffers the double overpressure caused by the Mach stem.

The chart below plots the regular reflection region and Mach reflection region, given the detonation distance from the ground. To use, you divide the burst height and the distance from ground zero by weapon kilotons raised to the 1/3 power.

For instance, if the weapon had a yield of 1,000 kilotons (1 megaton) and the weapon burst 2,000 feet above ground level, 2000 / (10001/3)

Scaled Height of Burst = burstHeight / yield1/3
Scaled Height of Burst = 2000 / 10001/3
Scaled Height of Burst = 2000 / 10
Scaled Height of Burst = 200

so on the plot for the vertical scale you would use the tick-mark at 200. By the same token, for the horizontal scale, the tick mark for 800 corresponds to 800 * 10 = 8,000 feet (where 10 = 10001/3).

The dotted line shows where the regular reflection region stops and the Mach reflection region begins.

The bulges in the overpressure curves show where you can optimize the height of burst for a given overpressure. For instance, look at the 15 lb/in2 curve. Find the point on the curve that gets the farthest to the right. Trace a line horizontally to the vertical scale and you'll see this happens at a scaled height of burst of 650 feet. For a 1,000 kiloton weapon this is a burst height of 6,500 feet.

In other words, a weapon bursting at 650 scaled feet of altitude will throw 15 PSI of overpressure out to 1,200 scaled feet from ground zero. But a weapon doing a ground burst with 0 scaled feet of altitude will only throw 15 PSI out to 800 scaled feet from ground zero.

from Physics and Nuclear Arms Today edited by David Hafemeister (1991)

Prompt Radiation

EffectsExplosive yield / detonation height
1 kt / 200 m20 kt / 540 m1 Mt / 2.0 km20 Mt / 5.4 km
Effects of instant nuclear radiation—slant range (km)
Lethal total dose (neutrons and gamma rays)
Total dose for acute radiation syndrome1.
from Wikipedia article Effects of nuclear explosions
"Lethal" is defined as a dose of 10 grays. "Acute radiation syndrome" is defined as a dose of 1 gray.

Residual Radiation

This is the radioactive fallout, radioactive dust that falls from the sky in a long plume extending downwind.

As a general rule, the fallout is dangerous for about one to six months after the bomb blast.

Unless it was a salted bomb, then you are probabably looking at a hundred years or so. A salted bomb whose fallout emitted a dosage of 10 sieverts per hour would need about 25 half-lives to decay to safe levels (i.e., to a dosage below natural background radiation). For example, a salted bomb producing Cobalt-60 would have fallout with a half life of 5.2714 years. 25 half-lives would be 131.785 years. Tantalum-182 has a half-life of only 114.4 days, it would be safe in about 7.8 years.

Air bursts tend to produce lesser amounts of fallout, but which travel at high altitudes and can scatter itself all over the entire planet.

Ground bursts tend to produce more severe levels of fallout, but which only travel relatively short distances from the detonation site (several hundred kilometers). The Castle Bravo 15 megaton nuclear test made a plume about 500 kilometers downwind with a maximum width of 100 kilometers.

Water surface bursts are sort of in-between.

The Wikipedia article stated that the crater of a ground burst would have fallout emitting radiation at a dosage rate of 30 grays per hour, but failed to specify the yield of the weapon.


      The U.S. military thought it had cleared the decks when, on 9 July 1962, it heaved a 1.4-megaton nuclear bomb some 400 kilometers into space: Orbiting satellites were safely out of range of the blast. But in the months that followed the test, called Starfish Prime, satellites began to wink out one by one, including the world’s first communications satellite, Telstar. There was an unexpected aftereffect: High-energy electrons, shed by radioactive debris and trapped by Earth’s magnetic field, were fritzing out the satellites’ electronics and solar panels.

     Starfish Prime and similar Soviet tests might be dismissed as Cold War misadventures, never to be repeated. After all, what nuclear power would want to pollute space with particles that could take out its own satellites, critical for communication, navigation, and surveillance? But military planners fear North Korea might be an exception: It has nuclear weapons but not a single functioning satellite among the thousands now in orbit. They quietly refer to a surprise orbital blast as a potential “Pearl Harbor of space.”

     And so, without fanfare, defense scientists are trying to devise a cure. Three space experiments—one now in orbit and two being readied for launch in 2021—aim to gather data on how to drain high-energy electrons trapped by Earth’s magnetic field in radiation belts encircling the planet. The process, called radiation belt remediation (RBR), already happens naturally, when radio waves from deep space or from Earth—our own radio chatter, for example, or emissions from lightning—knock electrons trapped in Earth’s Van Allen radiation belts into the upper atmosphere, where they quickly shed energy, often triggering aurorae.

     “Natural precipitation happens all the time,” says Craig Rodger, a space physicist at the University of Otago. But it would not nearly be fast enough to drain nuclear-charged radiation belts, where electron fluxes can be millions of times higher than in Earth’s Van Allen belts.

     Scientists got a glimpse of a potential solution from NASA’s Van Allen Probes, which launched in 2012 and ducked in and out of Earth’s radiation belts until the mission ended last summer. It offered a deep dive into natural remediation processes, showing how radio waves resonate with high-energy electrons, scattering them down the magnetic field lines and sweeping them out of the belts. “Compared to 10 years ago, we just know so much more about how these wave-particle interactions work,” says Geoff Reeves, a space physicist at Los Alamos National Laboratory.

     Now, researchers are ready to try artificial remediation, by beaming radio waves into the belts. Physicists have tested using the U.S. Navy’s very low frequency (VLF) antenna towers, powerful facilities used to communicate with submarines, says Dan Baker, director of the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder, and a lead investigator on the Van Allen Probes. The antennae of the High-frequency Active Auroral Research Program in Alaska and the giant dish of the Arecibo Observatory in Puerto Rico might also be enlisted to generate cleansing radio beams.

     An orbiting RBR platform, closer to the target, could be more effective. In June 2019, the U.S. Air Force launched what it bills as the largest uncrewed structure ever flown in space: the DSX dipole antenna. Nearly as long as a U.S. football field, DSX’s primary mission is to transmit VLF waves into the Van Allen belts and measure precipitating particles with onboard detectors. “It’s a new way to prod the belts and explore basic questions in space physics,” says DSX’s principal investigator, James McCollough at the Air Force Research Laboratory.

     A team of scientists at Los Alamos and NASA’s Goddard Space Flight Center is spearheading a second experiment in VLF precipitation. In April 2021, the team plans to launch a sounding rocket carrying the Beam Plasma Interactions Experiment, a miniature accelerator that would create a beam of electrons, which in turn would generate VLF waves capable of sweeping up particles. Reeves, who leads the experiment, believes the compact electron accelerator could ultimately be a better broom than a gigantic VLF antenna. “If we validate it with this experiment, we have a lot more confidence we can scale it up to higher power,” he says.

     A third experiment would coax the atmosphere itself to kick up turbulent waves that would draw down electrons. In the summer of 2021, the Naval Research Laboratory plans to launch a mission called the Space Measurements of a Rocket-Released Turbulence. A sounding rocket will fly into the ionosphere—an atmospheric layer hundreds of kilometers up that’s awash in ions and electrons—and eject 1.5 kilograms of barium atoms. Ionized by sunlight, the barium would create a ring of moving plasma that emits radio waves: essentially a space version of a magnetron, the gadget used in microwave ovens.

     The missions should help show which RBR system is most feasible, although an operational system may be years off. Whatever the technology, it could bring risks. A full-scale space cleanup might dump as much energy into the upper atmosphere as the geomagnetic storms caused by the Sun’s occasional eruptions. Like them, it could disrupt airplane navigation and communication. And it would spawn heaps of nitrogen oxides and hydrogen oxides, which could eat away at the stratospheric ozone layer. “We don’t know how great the effect would be,” says Allison Jaynes, a space physicist at the University of Iowa.

     Besides safeguarding against a nuclear burst, RBR technology could have a civilian dividend, Jaynes notes. NASA and other space agencies have long wrestled with shielding astronauts from the Van Allen belts and other sources of radiation on their way to and from deep space. VLF transmitters might be used to clear out high-energy electrons just before a spacecraft enters a danger zone. “When we become more active space travelers,” she says, “it could provide a safe passage through the radiation belts.” 

Specialized Nuclear Weapons

Enhanced Radiation Weapon
Also known as a "neutron bomb." This is a bomb optimized so most of the energy comes out as neutrons. In conventional nuclear weapons most of the energy comes out as x-rays. The idea is for the weapon to kill enemy troops and civilians while doing minimal damage to buildings and equipment.
Details are classified but the best I've found is the theoretical maximum for a neutron bomb is 80% of the energy is neutrons and 20% x-rays. For conventional nuclear weapons it is 80% soft X-rays, 10% gamma rays, 10% neutrons.
Salted Bomb
Also known as a "cobalt bomb." This is a bomb optimized to produce huge amounts of radioactive fallout in order to render large areas uninhabitable.
This is done by encasing the weapon in a jacket composed of some element that will easily be transmuted into a radioactive isotope by the weapon's neutron flux. Proposed elements for the jacket include cobalt-59, gold-198, tantalum-182, zinc-65, and sodium-24.
A conventional nuclear weapon typically generates fallout that will decay to safe levels in one to six months. A cobalt bomb whose fallout caused a dose rate of 10 sieverts per hour would take about 130 years (25 half-lives) to decay to safe levels (safe levels being defined as "less than natural background radiation").
The name "salted" comes from the expression "sowing the earth with salt".
Dirty Bomb
This is not a military weapon, it is an ineffectual terrorism device. It is a stick of dynamite or other small chemical explosive inside a container of powdered radioactive material. The only reason it is mentioned here is because it is sometimes confused with a salted bomb.
A dirty bomb might spread a bit of mildly radioactive dust over a building or two.
A salted bomb will spread highly radioactive fallout across half a continent.
The dreaded Nuclear Electromagnetic Pulse. A conventional nuclear weapon of several megatons yield is detonated at a high altitude (commonly mentioned as 400 kilometers). The resuling EMP does damage to every device using electricity within a huge range. The details are sketchy because they are still classified. For best results a planetary atmosphere is required.
The linked Wikipedia article has an overview of the convoluted details, including a useful quote from a 2010 Oak Ridge National Laboratory report on common EMP misconceptions.

Project Pluto

This is mostly from THE PLUTO PROGRAM and Aerospace Projects Review Volume 2, Number 1. Some additional material from Spaceship Handbook.

This is an old favorite among fans of nuclear weapons, the one everybody shakes their head over and says WHAT THE FLAMING FRACK WERE THEY THINKING??!? You often see it under such names as Project Pluto, Flying Chernobyl, S.L.A.M., The Flying Crowbar, Nightmare Missile, Flying Death Factory, and Armageddon Cruise Missile From Hell.

Technically the entire weapon was called Supersonic Low Altitude Missile or SLAM. Project Pluto was just the engine.

The original idea was a 1955 version of what we now call a cruise missile. Seeing that this was going to be a part of mutually assured destruction, perhaps even a possible replacement for the Strategic Air Command, the designers wanted SLAM to be long ranged. Very long ranged. Circle-The-Globe-Four-And-A-Half-Times long ranged.

Chemical fuel couldn't possibly fill the bill, the only thing with enough power was nuclear energy. Alas, cruise missiles share the same problem that aircraft and spacecraft have with atomic drives. The three vehicles all suffer from the Every Gram Counts limit so they want to be as light as possible. But anti-radiation shields are the opposite: the heavier the better. If the crew cabin was located far enough away from the reactor, you might be able to get away with using an anti-radiation shadow shield light enough so that the aircraft could actually get off the ground. It is a pity that anybody on the ground the aircraft flew over would be bathed in deadly radiation.

Then some cold-hearted genius in the research department saw how to turn the liability into an asset.

Understand that the SLAM reactor, like all reactors, are not very radioactive. Until the first time they are powered up, then they will emit torrents of radioactive death for centuries.

If the nation goes to DEFCON 1 you launch the SLAM using non-radioactive chemical rockets. These get the nightmare missile out to sea far enough so that no (United States) person was endangered. Then the totally unshielded reactor was powered up. Since the monster had a range of 182,000 km (x4.5 the circumference of Terra) it wasn't going to run out of fuel anytime soon. Especially since it didn't have to lug around a heavy radiation shield. It could fly in a circular holding pattern until nuclear war was initiated or called off, killing nobody with radiation except sea life and any unfortunate fishermen it flies over.

Somebody figured that "radiation in the defense of liberty is no vice". Somebody on Twitter remarked: "So it does fly without core containment, that is some serious Reaver sh*t."

If the war was called off, the SLAM(s) would abort by quenching their reactors and ditching into the (hopefully) deep ocean. Anybody with bright ideas about salvaging US weapons from the sunken SLAMs will have to deal with the radiation from its neutron-activated structure. The SLAM designers might deliberately incorporate cobalt or something similar into the structure as a rude surprise.

5,500 pound thermonuclear weapons payload
Can be divided as:
x126 megatons
x51.3 megatons
x91.1 megatons
x14750 kilotons
x16200 kilotons
x3650 kilotons
x425 kilotons

But if war is declared, the SLAMs will drop to a stealth wave-hugging altitude and proceed at supersonic velocity toward their designated Soviet targets, with a weapons loadout of 1 to 42 thermonuclear bombs (1@26 megatons, 42@5 kilotons each). 25 megatons is considered to be a "city-killer", though a single bomb that big tends to be a waste of nuclear energy. Since there are no skyscrapers a mile in the air or a mile underground, the most of the spherical nuclear fireball is wasted. It is more efficient to use a pattern of kiloton devices with a fireball about one skyscraper-height in radius.

The SLAM will cross the ocean at an altitude of 35,000 feet, but when it approached the Soviet air detection system it would drop below "radar detection altitude". One source said that was 500 to 1,000 feet, another said 50 feet.

Traveling at Mach 3 at treetop level (15 meters or 50 feet) means that any person standing underneath will be instantly killed by the sonic shockwave alone (they will also be made deaf by the 150 dB sound and given cancer, but these things matter not to a dead person). The thing is also white-hot so there will be a bit of thermal pulse as well, to add insult to injury.

The same cold-hearted genius also figured that after a given SLAM had dropped all its H-bombs it could still do damage by leisurely flying a criss-cross pattern over Soviet territory, irradiating the croplands and people with deadly radiation from the totally unshielded reactor (sowing the ground with salt, radioactive-style). This also meant that the SLAM designers didn't have to worry about preventing radioactive fission fragments from escaping out the exhaust, since it would give you bonus enemy fatalities out of each gram of fission fuel. Which means they didn't bother putting any cladding on the nuclear fuel elements, they are in direct contact with the air.

And if the Soviets managed to shoot down a SLAM, it would auger into the ground at Mach 3, pulverizing the entire reactor and spreading a plume of radioactive fallout rendering the impact region uninhabitable for about the next ten-thousand years. If they fail to shoot it down, it is programmed to crash anyway. Only after it has finished its sterilization criss-cross. The hot reactor elements will mix with the white hot vaporized forward vehicle structure to create a very fine smoke of radioactive uranium oxides. That is, of a fineness to extend the length of the fallout plume. As Scott Lowther puts it: "It'd make Chernobyl look like Three Mile Island."

The mechanical designer faces a challenge. The pressure drop in the direction of the air stream creates a force of several hundreds of thousands of kilograms trying to suck the reactor out the nozzle, which is a bad thing. The materials available to make supporting structures are limited in volume and nature because of neutronic requirements (too much structural metal and the reactor can go critical while it is being assembled) and high temperatures (standard metals will melt).

SLAM Missile
ParameterEarly Tech
(Tory II-C)
Advanced Tech
(Tory III)
Payload compartment dia (in)5558
Payload compartment len (in)213300
Total Vehicle Length (ft)8488
Hot reactor dia (in)5746
Hot day design Mach
1,000 ft above sea level
Hot day design Mach
30,000 ft above sea level
Reactor wall temp (°F)25,0003,000
Max number of warheads18-2426
Payload weight (lb)14,00015,000
Missile weight (lb)55,80060,779
Booster weight (lb)61,38067,465
Expected missile range (nm)
1,000 ft above sea level
Expected missile range (nm)
30,000 ft above sea level

It is unclear if the expected range is limited by the nuclear fuel elements becoming clogged with neutron poisons, or because the ceramic reactor core crumbled. If the former, there are modern ways around that problem.


I was curious about the radiation dose the SLAM would inflict upon a person on the ground. It was traveling at 50 feet (15 meters) above the ground, near where the lethal dose was absorbed in about 5.76 seconds. But on the other hand the SLAM is traveling at about 1,000 meters per second (Mach 3) so exposure time is very short. I could not intuit whether the person would get a lethal dose or not. This calls for higher math, probably calculus. Unfortunately I failed to learn calculus (Bad Winchell! No rocket for you!). Therefore I used the old Tom Sawyer Whitewash technique.

On Google Plus I poised the question (please pardon the Imperial units):


For lack of a better source, the word problem below was created by me, unqualified though I am. Be told that it may contain unwarrented assumptions and misunderstood numerical values for which I take sole responsibility. Particularly I am assuming that the diagram above is accurate. Use the analysis below at your own risk.

     Say there is a Project Pluto nuclear ramjet cruise missile in the area.
     Say that forty feet away from it's center the radiation dose is 5×108 Röntgen/hour of gamma rays. Say that 35 feet away from the center the radiation dose is 5×106 Röntgen equivalent physical/hour of neutrons. The radiation falls off as per the inverse square law. Figure that the maximum range that the radiation has effect is about 15,300 feet, or the distance to the horizon.
     It is traveling along line A-B where the line is at a constant altitude of 50 feet (tree-top level), at a speed of Mach 3 (which I think is about 3,350 feet per second since that altitude is practically sea level).
     Somewhere near that line is point X, on the ground directly underneath line A-B. A poor hapless person is standing there.
     At some point the Project Pluto nightmare missile will appear on the horizon, flash overhead at 3,350 ft/s, and vanish on the far horizon. Emitting deadly gamma-rays and neutrons all the while.

     Question: What radiation dosage will the poor person at point X suffer?

Remember neutrons Röntgens equivalent physical have an average quality factor of 10.0 so equals an average of 0.096 Sievert. Gamma rays Röntgens have a quality factor of 1.0 so each equals 0.0096 Sievert (one-tenth that of neutrons).

Two kindly educated people came to my rescue, Peter Schmidt and Simon Smith.


I believe you need to integrate 1/(x-35)^2 * 5*10^6 from x=50 to x=15300, then multiply by 2 (to cover its approach and departure). Wolfram Alpha says ~6.7*10^5 REP/hr neutrons (6,400 Gray/hr and 64,000 Sievert/hr) .

(see WolframAlpha results here).

To sanity check, it will travel 15,300*2 feet in 9.13 s. (15,300*2 / 3,350 = 9.13)

At t = 1/2 * 9.13, using the inverse square law, the dose from 50 ft away is 2.45*10^6 Röntgen/hour, while at the horizon, it is a mere 26 Röntgen/hour.

Halfway from the horizon, it is 100 Röntgen/hour. If you average those three points (which is a linear, not inverse squared relation, so will be high), you get 1.6*10^6 REP/hr, which is 10x high, so I'm buying the Wolfram result.

If that's the dose rate, in 9.13s, dose will be about 1,700 Röntgen (6.7 * 10^5 Röntgen/hr / 3600 s/hr * 9.13 s) (16 Grays and 163 Sieverts of neutron radiation)

This website says "A short-term dose of 600 Röntgen (5.8 Grays) would probably be fatal" so RIP bystander…


I got the same ballpark as Peter. The neutron dose is about 1,700 R (16 Gy and 163 Sv) but the gamma dose is 254,000 R (2,440 Gy and 2,440 Sv). This is a death rocket that kills pretty much everybody within a 3/4 of a mile (1,200 meter) radius of its flight path.

Winchell Chung, your gamma dose is given as 5x10^8 R/hr at 40 feet whereas the neutron dose is only a measly 5x10^6 R/hr at 35, so the gamma dose will be more than 100x greater.

3/4 mile is the radius where the gamma Röntgen dose is the 600 Röntgen figure Peter used. You get that if the range varies from 15,000 ft ⇒ 4,000 ft ⇒ 15,000 ft (4,000 ft = 3/4 mile)

That Wolfram formula's very handy.

Thank you very much, Peter Schmidt and Simon Smith! Even if the figures and assumptions I supplied you with were incorrect, the technique revealed will be useful elsewhere. I really have to buckle down and learn calculus, and master Wolfram Alpha.

The Acute Radiation Chart says that 5.8 Grays is at the "Death probable within 3 weeks" level, 16 Gy is "Certain death in one week or less" along with the cruel Walking Ghost period, and 2,440 Gy is about thirty times the 80 Gy "Instant coma and certain death in 24 hours".

Peter Schmidt's formula is:

integrate 1/(x-35)^2 * 5*10^6 from x=50 to x=15300, then multiply by 2


35 = distance from SLAM of the reference dosage rate
5*10^6 = Röntgen/hour reference dosage rate value
x=50 = closest distance SLAM comes to person (altitude from ground)
x=15300 = farthest distance SLAM recedes from person (vanishes over horizon)
1/(x-35)^2 = inverse-square law, how radiation intensity varies with distance

which was derived from the word problem stating: Say that 35 feet away from the center the radiation dose is 5×106 Röntgen equivalent physical/hour of neutrons and Figure that the maximum range that the radiation has effect is about 15,300 feet, or the distance to the horizon and at a constant altitude of 50 feet. The units used for distance do not matter, as long as you use the same units for all three variables. The units used for absorbed dose do not matter, the answer will be in the same units.

This is fed into WolframAlpha as value of integral of 1/(x-35)^2 * 5 * 10^6 from x=50 to x=15300, times 2

Let's try it out. For gamma-rays it was 40 feet away from the center of radiation had a dose of 5×108 Röntgen/hour. So we feed into WolframAlpha value of integral of 1/(x-40)^2 * 5 * 10^8 from x=50 to x=15300, times 2 and it returns 1.0 * 10^8 Röntgen/hr.

1.0 * 10^8 Röntgen/hr / 3600 sec/hr * 9.13 sec = dose of 254,000 Röntgen. Which is the figure Simon Smith calculated, so we are golden.

Higher Altitude

The above figures are for a SLAM flying at 50 foot tree-top level altitude. Other sources suggest it may fly at up to 1,000 foot altitude. This will drastically reduce the radiation dosage on the ground, but how much?

I used Mr. Schmidt's handy formula, substituting "1000" for "50".

It reduces the neutron dose from a death-in-minutes 163 Gy (1,700 R) to a fighting-chance 50%-fatality 2.5 Gy (26 R).

Sadly for the person on the ground the gamma dose went from an instant-death 2,440 Gy (2.54×105 R) only to a death-in-two-days 25 Gy (2,642 R). Immediate disorientation, coma in seconds to minutes, convulsions, and certain death within 48 hours.

Using Ms. Smith's technique if you adopt a certain death dosage of 10 Gy (394,300 R/hr for 9.13 seconds) as your trigger level, this means the SLAM kills pretty much everybody within a half mile (790 meters) radius of the flight path (15,300 ft ⇒ 2,600 ft ⇒ 15,300 ft). And doesn't do the topsoil any good either. Yes, this is narrower than 3/4 of a mile, but it is only a 30% reduction. After all a half mile radius means the SLAM is laying down a path of scorched dead earth one mile wide and thousands of miles long.

The SLAM may fly at a 500 foot altitude instead of 1,000 feet, which will just increase the dosage. I leave the math as an exercise for the reader.

Hold everything. A gentleman named Giorgio Tiburzi contacted me, and has noted some flaws in the above analysis. Please note that the error appears to be me mis-reading the diagrams, it is not the fault of Mr. Schmidt and Ms. Smith. Apparently I gave them incorrect data and incorrect assumptions. Mr. Tiburzi's analysis is below:


First, I have noted a discrepancy between the values you quote for the gamma dose rate. The first graph on your webpage has units of rads per hour, and indicates a gamma flux of slightly less than 107 R/h at 30 feet. The second one quotes 109 erg/g per hour at the same range, which you have equated to rads — but in fact, the rad "was originally defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by one gram of matter" [source]

The second graph, then should also be read as 107 R/hr at 30 feet, resolving this incoherence — unfortunately, in your question on Google Plus you used 5×108 R/hr at 40' for the γ dose rate (my bad).

The second problem I noticed is that the dose integral suggested by Peter Schmidt is not dimensionally correct. The dose rate we have from the graphs has units of [rads/time], and so we need to integrate it over a time interval to get a radiation dose. The inverse square law factor has to be non-dimensional, since we don't want units of meters squared at the denominator.

The correct way to approach this calculation is writing the instantaneous dose rate as a function of time, then integrating it over the time period when the missile is over the horizon.

If we define R as the dose rate at distance x0, v as the missile speed, h as the flight altitude i.e. the minimum distance to the missile, tf as the time of flight above the horizon, and t=0 at overflight,

is the slant range to the missile at each time t

the inverse-square-law scaling factor is

and the total dose for each point on the ground overflown by the missile is

The dimensions of the above equation, then are

and we get the correct unit on the left-hand side after the other factors simplify with each other. This formula is valid in a vacuum, and substituting the values R=2777 rad/sec, x0=30 ft, tf=5s or above, and v=3350 ft/sec, for a range of altitudes we obtain the following results:

Actually though, for flight altitudes just a bit above the "frying chicken in the barnyard" level, absorption of γ-rays by the intervening air becomes quite significant; there is then a second attenuation term we should be considering, besides the inverse square law.

Most prompt gamma rays from a reactor (those emitted immediately after fission, by relaxation of the daughter nuclei) have energies lower than 1 MeV. My source for this is "Prompt fission γ-ray spectra characteristics - a first summary" - Oberstedt, Wilson et al, Physics Procedia 64

I don't have a similarly clean picture for the spectrum of secondary gammas (those from fission fragment decay), but Table II of "Fission Product Gamma Spectra" by E.T. Jurney et al. seems to report an average energy of, again, 1 MeV.

Figure 8.106 of Glasstone-Dolan, The Effects of Nuclear Weapons reports a γ spectrum for a 20 kT nuclear explosion (fission) at 2 kilometers, with 70% of the energy below 750 keV. There is no data for very short distances, but since lower energy photons are absorbed quicker, hard gammas should be overrepresented in that figure compared to shorter range exposures.

I will then use 1 MeV as the average energy of gamma rays: Glasstone and Dolan, again, give an absorption coefficient μ=0.8×10-4 cm-1 for air at sea level in Table 8.96, equivalent to a halving distance of 90 meters (300 feet).

The complete dose formula for gamma rays then becomes

where the exponent is again a non-dimensional, scaled distance: the slant range multiplied the attenuation factor (i.e. the inverse of the air thickness that reduces the dose by a factor 1/e).

The new results including atmospheric shielding are then

I must admit that it's surprising to find a completely negligible value at the relatively short distance of 1 km: but after all, a dose rate of 107 R/hr at 10 meters is reduced 10,000-fold by the inverse square law and about 1,000-fold by the absorption, down to just 1 R/hr.

This is certainly an underestimate for the longer ranges, since e.g. secondary photons will be generated in the air and accounting for those would substantially change the result (source) but the general picture should hold.

I don't know how to make a similarly clean estimate for the neutron dose: I could not find any data on attenuation of neutrons through air, and neutron transport is a notoriously complex topic. If we just take the total dose rate to be 6×107 REM/hr at 30 feet (multiplying 5×106 by a quality factor of 10 for the neutrons) and use the vacuum equation, the new upper bound for exposure at 50 feet minimum distance is 280 REM, down to 10 REM when h=1400 ft. We do recover a lifethreatening exposure, then, but only for the lowest possible altitude.

Looking for some sort of external confirmation of these calculations, I turned to Alex Wellerstein's NUKEMAP, a web tool that simulates the effects of nuclear explosions with open-source models, mostly based as usual on the Glasstone-Dolan.

A 10 kiloton explosion at 1000 meters altitude, according to the model, inflicts a prompt dose of 2000 REM at ground zero (from all types of radiation). A yield of 10 kilotons corresponds to 40 TJ, and the Tory-IIc reactor — with a power of 560 MW — takes about 20 hours to generate the same amount of energy from fission.

I think that it's reasonable, then, to take 100 REM/h as a ballpark estimate for the dose rate from a Tory-IIc at 1 km.

Another similar back-of-the envelope estimate has been proposed by Scott Manley, who I suppose you are familiar with, in his recent Youtube video about Project Pluto. He quotes the lethal radius for radiation effects of the Davy Crockett mini-nuke at a quarter of a mile, and states that the Tory-IIc takes 100 seconds to yield the same amount of fission energy as the blast of that device. Source [time: 3m10s]

From this data, he also concludes that a lethal dose from a fly-by of a SLAM would not be possible. (He assumes h = 1000 ft)

by Giorgio Tiburzi (2018)



(ed note: the radiation exposure is reported in the obsolete unit Roentgens (R). The SI unit is coulomb per kilogram (C/kg). One roentgen equals 0.000258 C/kg )

      An important aspect of test flight of a PLUTO vehicle is the hazard that would arise if the vehicle were to crash in an inhabited region. This hazard will be discussed on the assumptions that the reactor operated for 10 hrs at 600 MW immediately prior to the crash, and that essentially all fission products generated were retained.

     The crash is assumed to render the reactor highly supercritical such that it disassembles violently and 10% of its fission product inventory escapes to the atmosphere. The fission products generated at impact are due to the fission of less than one gram of U235 whereas 250 grams of U235 were consumed in the previous ten hour period. Therefore the nuclear disassembly is significant only as a dispersal mechanism.

     The dose rates arising from direct radiation at various distances and times after collision are given in Table I.

Time After Collision1000 Ft2000 Ft3000 Ft4000 Ft5000Ft 6000 Ft
1 hour10,000 R/hr530 R/hr50 R/hr5.7 R/hr770 mr/hr110 mr/hr
1 day900 R/hr47 R/hr4 R/hr510 mr/hr70 mr/hr10 mr/hr
1 Week90 R/hr5 R/hr0.4 R/hr50 mr/hr7 mr/hr1 mr/hr

     Attenuation of the gamma rays by air accounts for over a three order reduction in intensity at a distance of one mile from the reactor.

     Upon collision, some portions of the reactor will ay off with an initial velocity of 3000 ft/sec. These will have a maximum range not in, excess of 2000 ft. The latter value has been confirmed experimentally in ballistic studies of non-aerodynamically shaped bodies of aluminum, steel, and uranium. Initial velocities of 10,000 ft/sec. were attained. Calculations also corroborate the value of maximum range, for frontal drag acts to reduce the initial velocity rapidly and so limit the range.

     Other possible mechanisms for exposure to people in the neighborhood of the crash include fallout and immersion in the cloud. To achieve a realistic and yet conservative value for exposure from fallout, micro-meteorological constants which were determined from the KIWI-A (NTS) test run were employed. Also, a particle size was chosen to maximize the deposition rate at different distances; it varied slightly from a diameter of 30 microns. The maximum fallout dose rate, assuming the escape of 10% of the fission products, was 100 mr/hr at 5500 meters from the crash point and 15 minutes after the crash.

     Exposure from direct immersion in the cloud is found to be small with respect to the fallout dose. To compare the two, the integrated dose was determined, for the immersion exposure occurs only during transit of the cloud past the downwind point in question while the fallout hazard is very prolonged. Figure 1 shows that the peak dose from cloud immersion is 35 mr at 5500 meters from the crash point. The fallout dose is also maximized here and is 1.7 r.

     The direct dose is also shown for a point source. Since there may be dispersal of reactor contents, the curve may shift left or right 2000 ft., or ~600 meters.

     It is seen, therefore, that at distances within 3000 meters from the crash point, direct radiation is the most important cause of exposure, while at greater distances fallout is the most important.

     If the crash occured in a populated area, an exclusion radius of 3000 meters, or ~two miles is recommended. Great care would be required for closer approach to the vehicle. Aerial surveillance should be conducted with caution.

Project Pluto Reactor
Diameter57.25 in.
Fissionable Core47.24 in.
Length64.24 in.
Core Length50.70 in.
Critical Mass of Uranium59.90 kg.
Avg. Power Density10 MW/cubic foot
Total Power600 MW
Avg. Element Temperature2,330° F

Orion Bomber

This is from material from the Fourth Symposium on Advanced Propulsion Concepts parts i, iii, iii and from Aerospace Project Review Issue Volume 1, Number 5. As always, in the datablocks you see in on the edges of this page the values in black are from the source documents but the values in yellow are not. Yellow values are ones that I have personally calculated, sometimes using questionable assumptions. Yellow values are not guaranteed to be accurate, use at your own risk.

In March of 1965 the Orion program was pretty much over. Nobody was interested in a spacecraft powered by hundreds of atom bombs. In a frantic attempt to keep it alive, General Atomic released a report describing several potential military applications. Hey, Pentagon, here are some great serving suggestions for an Orion! Please don't let the program die.

It didn't work but you can't blame them for trying.

Reference Orion Configurations
Pusher Diameter (m)81012
Length (m)22.125.729.7
Thrust (N)2,360,0003,470,0004,320,000
Isp (sec)2,7203,3003,670
Exhaust Velocity (m/s)26,70032,40036,000
Weight (kg)81,700109,000172,000

The applications used all three of the standard Orion engines: eight, ten, and twelve meter pusher plate sizes. Since a nuclear launch was pretty much out of the question, each proposal used a stage of quick-and-dirty solid rocket clusters to loft the Orion to an altitude of 76,200 meters before the nukes started. The liftoff thrust-to-weight (T/W) ratio was 1.8 for all three Orion sizes. The solid rockets got the spacecraft up to 76,200 meters and 2,900 m/sec, the Orion drive kicked it the rest of the way into a 370 km orbit. The back of my envelope says the Orion has to expend 8,300 m/s of delta-V, some of that is aerodynamic drag and gravity drag.

8-meter Orion spacecraft would be lofted by a cluster of seven 120-inch solid rocket boosters, developed from the strap-on solid rockets used on the Titan III launch vehicle. They would have been more powerful than the Space Shuttle solid rocket boosters.

10-meter Orion spacecraft would be lofted by a cluster of four 156-inch solid rocket boosters. These were studied in the 1960s as possible strap-ons for the Saturn V, and as a cluster to replace the first stage of the Saturn Ib.

12-meter Orion spacecraft would be lofted by a cluster of seven 156-inch solid rocket boosters.

When the Orion drive started up at 76,000 m, its T/W was only 0.55. This meant a very ugly gravity tax, but the total payload delivered to orbit was maximized. Who cares about gravity tax, the Orion has delta-V to spare.

From a military standpoint, the Orion drive is attractive not only because of its high thrust and specific impulse. The drive is also resistant to damage. Fussy delicate chemical engines can be disabled with a handgun. Orion drives are built to be tough enough to withstand hundreds of impacts by nuclear explosions at close proximity. A handgun bullet will just bounce off. The enemy will have to use massive weapons in order to dent one of those babies. This is not as big a selling point for NASA, who generally does not have to worry about enemy spacecraft taking pot-shots at them.

For the same reason such drives are very easy to maintain and repair. You don't need needle-nosed pliers and micro-screwdrivers. A sledge hammer and a cold chisel will do. It helps that the engine is made of good ol' simple to fix steel, instead of cantankerous titanium or aluminum.

And unlike nuclear thermal rockets, Orions have very low residual radioactivity. It is safe to go out and work on an Orion drive only a few minutes after the last nuke exploded. Nuclear thermal rockets on the other hand will be unsafe to go near for a few thousand years.

Some of the applications had the Orion spacecraft stationed in space, others had them based on the ground. The former was basically using the Orion drive to loft an outrageously huge military space station into permanent orbit, in one piece. Applications stationed in space could be launched at leisure. Applications stationed on the ground on the other hand were a reaction force. The Orions would sit in their silos "on alert", ready to launch at a moment's notice. For space based system the primary concern is maneuverability and survivability. For ground based systems the primary concern is readiness.

The minor drawback of the Orion spacecraft's titanic mass is there was no practical way to land them back on Terra (short of lithobraking). Once they were launched into space, they stayed there. The crew was rotated by space shuttles or small reentry vehicles. Trying to land under Orion drive power is a very bad idea, especially on a planet with an atmosphere. The ship will be entering the center of each raging nuclear fireball with lamentable results.


  • Command/Control
  • Strategic Weapon Delivery ("Bomber")
  • Surveillance-reconnaissance
  • Space Defense
  • Orbit Logistics
  • Lunar Base Support
  • Space Rescue and Recovery
  • Satellite Support
  • R&D Laboratory


  • Emergency Command/Control
  • Space Interceptor
  • Damage Assessment
  • Space Rescue and Recovery
  • Satellite Support


ECCS Orion
Stage 2 Orion Engine
Pusher dia8 m
Isp2,720 sec
Exhaust Vel26,700 m/s
Thrust2,400,000 N
Stage 2
Payload Mass91,000 kg
Orion Engine Mass82,000 kg
Dry Mass172,700 kg
Pulse Units Mass290,300 kg
Wet Mass463,000 kg
Mass Ratio2.678
Total ΔV26,300 m/s
Reserve ΔV in LEO18,000 m/s
Stage 1 Chemical Engine
Exhaust Vel?
Stage 1
Payload Mass463,000 kg
Engine Mass?
Dry Mass?
Propellant Mass?
Wet Mass2,540,000 kg
Total ΔV3,100 m/s
Stack Height64 m
Stack Max Dia9.1 m

In case NORAD gets taken out by a dastardly nuclear first strike on the United States, the ECCS Orion was designed to survive in its secret armored launch silo. It would boost into orbit and take over NORAD's functions, coordinating the nuclear retaliation.

Actually the plan was to launch before the enemy bombs actually hit the ground. NORAD can probably predict it will be unlikely to survive an incoming nuclear strike long before the bombs actually arrive.

The ECCS was housed in an 8-meter Orion. The surface geometry was smooth to avoid creating shot-traps, since an enemy would target an ECCS with lots of hostile weapons fire. After expending all those extra nukes to obliterate NORAD the enemy will be obligated to destroy all the ECCS NORAD-back-ups, otherwise they will have wasted all those warheads and have nothing to show for it.

Since the ECCS would operate beyond Terra's magnetosphere, the crew would need radiation shielding from galactic cosmic rays. Not to mention enemy nuclear warheads, possibly including enhanced radiation weapons.

The wet mass was 2,540,000 kg (5,600,000 lbs), of which 91,000 kg (200,000 lbs) was payload (apparently "payload" is the dry mass of the Orion spacecraft, without any nuclear pulse units. At least that's what my calculation suggest). Stack height with solid rocket boosters was 64 m (210 ft) (cluster of seven 120-inch solid rockets) and a maximum diameter of 9.1 m (30 ft). The boosters loft the Orion to an altitude of 76.2 km (250,000 ft). Then the 8-meter Orion engine uses its 2,400,000 N (530,000 lbf) of thrust and 2,750 seconds of Isp to get the rest of the way to a 370 km (200 nautical mile) circular orbit. At this point it would still have a delta-V reserve of 18,000 m/sec (60,000 ft/sec) for further maneuvers. The reserve can be used to provide orbit altitude and plane changes to provide the most effective surveillance coverage and to evade hostile weapon interceptions.

The ECCS will require a silo only slightly larger than a standard ATLAS or TITAN ICBM silo.

The ECCS would carry a crew of from ten to twenty, with lots of advanced surveillance and communication equipment. Average mission was 30 days, with provisions for up to 60 days. Radiation shielding on the order of 244 kg/m2 (50 lb/ft2) would be around all command/control and crew operating station, to protect against galactic cosmic rays and possible hostile enhanced radiation weapons. The structure, life support systems, and attitude jet fuel will provide an additional 244 kg/m2 for a total of 488 kg/m2 (100 lb/ft2). By way of comparison, a storm cellar protecting the crew from a significant solar storm should have at least 5,000 kg/m2.

Several ECCS would be on constant standby in their silos. If nuclear war was immanent one would be launched as a show of force, demonstrating that the US was "not unprepared to defend itself." Along with a diplomatic reminder that there are more ECCS where that came from.

One would NOT be launched if it was only a time of crisis instead of immanent war. That would be provocative, and could precipitate matters. It is difficult to convince the enemy to stand down from DEFCON 2 when you are massing troops on their boarder, so to speak.

Deployed in low orbit allows immediate surveillance coverage of enemy territory and maximum image resolution. Deployed in remote orbits provides broader coverage of the planet's surface and also allows early warning of incoming hostile weapons fire aimed at the ECCS.


Stage 2 Orion Engine
Pusher dia10 m
Isp3,300 sec
Exhaust Vel32,900 m/s
Thrust3,500,000 N
Stage 2
Payload Mass136,000 kg
Orion Engine Mass110,000 kg
Dry Mass246,000 kg
Pulse Units Mass354,000 kg
Wet Mass600,000 kg
Mass Ratio2.439
Total ΔV29,300 m/s
Reserve ΔV in LEO21,000 m/s
Stage 1 Chemical Engine
Isp294 sec
Exhaust Vel2,880 m/s
Stage 1
Payload Mass600,000 kg
Engine Mass936,000 kg
Dry Mass1,536,000 kg
Propellant Mass2,964,000 kg
Wet Mass4,500,000 kg
Mass Ratio2.930
Total ΔV3,100 m/s
Stack Height96 m
Stack Max Dia10 m

This is similar to the ECCS but with important differences. It is stationed in space. It is intended for permanent operations, not just for 30 days. It is larger, requiring a 10-meter Orion engine.

Three of these would be placed in geosynchronous orbit to provide constant global surveillance. They would augment their coverage via inter-ship relay. This will allow the ships to randomly change their positions and frustrate enemy weapons interceptions, yet still maintain coverage. One ship will be the "flagship" but others could take over if the flagship is disabled.

The wet mass was 4,500,000 kg (10,000,000 lbs), of which 136,000 kg (300,000 lb) was payload. Stack height with the stage 1 solid rocket boosters was 320 feet (cluster of four 156-inch solid rockets) and a maximum diameter of 96 m (33 ft). The solid rocket booster has a mass of 3,900,000 kg (8,500,000 lbs). At an altitude of 76.2 km (250,000 ft) the 10-meter Orion engine uses its 3,500,000 N (780,000 lbf) of thrust and 3,300 seconds of Isp to get the rest of the way to a 42,162 km (22,766 nautical mile) geosynchronous orbit. At this point it would still have a delta-V reserve of 21,000 m/s (70,000 ft/sec) for further maneuvers, though in theory it is in its forever home.

Actually, since the SSCCS will be launched in leisurely times of peace instead of under the urgent pressures of impending nuclear armageddon, solid rocket boosters are not needed. Instead the more sophisticated (but more time consuming) liquid-fueled Saturn V's S-IC stage could be used. Especially if NASA ever manged to make the S-IC recoverable, which as SpaceX has demonstrated drastically lowers the launch cost. Such a stack would have a wet mass of 3,300,000 kg (7,200,000 lbs).

The SSCCS will require about 3 megawatts with a peak of 9 MW or so for the surveillance and communication systems. This can be provided with RTG or other advanced power source. The crew will number from 20 to 30, with six-month tours of duty. The SSCCS will stay on location for their operational lifetimes, 15 to 20 years. The long lifetimes are due to the fact that upgrading obsolete surveillance and comm systems is a snap when you are using Orion drive cargo ships. No matter how much the replacements weigh. The communication/surveillance section is basically a chassis accepting plug-in replaceable modules.


Stage 2 Orion Engine
Pusher dia12 m
Isp3,670 sec
Exhaust Vel36,000 m/s
Thrust4,300,000 N
Stage 2
Payload Mass136,000 kg
Orion Engine Mass170,000 kg
Dry Mass306,000 kg
Pulse Units Mass424,000 kg
Wet Mass730,000 kg
Mass Ratio2.386
Total ΔV31,300 m/s
Reserve ΔV in LEO23,000 m/s
Stage 1 Chemical Engine
Exhaust Vel?
Stage 1
Payload Mass730,000 kg
Engine Mass?
Dry Mass?
Propellant Mass?
Wet Mass6,800,000 kg
Mass Ratio?
Total ΔV3,100 m/s
Stack Height88 m
Stack Max Dia12 m

Strategic Weapon Delivery AKA raining nuclear warheads onto the nation that attacks us.

This would require a full blown 12-meter Orion engine, because nuclear missiles are very heavy. And because you want to carry as many as you possibly can.

The wet mass was 6,800,000 kg (15,000,000 lbs), of which 136,000 kg (300,000 lbs) was payload. Stack height with the solid rocket boosters was 88 m (290 ft) (cluster of seven 156-inch solid rockets). At an altitude of 76.2 km (250,000 ft) and a speed of 3,100 m/s (10,000 ft/sec) the 12-meter Orion engine uses its 4,300,000 N (970,000 lbf) of thrust and 3,670 seconds of Isp to get the rest of the way to its patrol orbit. At this point it would still have a delta-V reserve of 23,000 m/s (75,000 ft/sec) for further maneuvers.

  • At A the SSSWD boosts into LEO (370 km) with solid rockets and Orion drive. The crew does a systems checkout.
  • At B burns into a Hohmann transfer (blue arc)
  • At transfer apogee C it burns to circularize the orbit. SSSWD is now in a 190,000 km circular orbit (green circle)
  • At D burns to enter Patrol orbit (red ellipse). Orbit has a perigee of 190,000 km and apogee of 410,000 km (a 190,000-410,000 km Terran orbit). The orbital period is 18.9 days

The crew will number 20 or more. A semi-closed ecological system will be used to permit a six-month tour of duty, with an emergency capacity of one year. It would require about 1 megawatt of onboard power for ship systems.

The interesting details about the weapons loadout are either not defined or classified. They are not in the report at any rate. Drat!

Defensive weapons include decoys and antimissile weapons. Defensive weapons are carried because bombers are the enemy's prime targets. The enemy knows that every single strategic weapon a SSSWD carries is a mushroom cloud with their name on it.

The strategic nuclear weapons were to be carried internally to allow easy access for maintenance. That way the technician wouldn't have to wear a space suit. The weapons are probably either megaton-range "city-killer" nukes, or MIRVs of deci-megaton-range. For reference, the original Minuteman-II ICBM carried a 1.2 megaton W56 thermonuclear warhead. The Minuteman-III had a MIRV bus carrying three 0.17 megaton W62 thermonuclear warheads (170 kilotons). Scott Lowther's recreation of the SSSWD carries 25 MIRVs, each with three warheads.

The nukes could be launched in either of two ways. [1] warheads could be mounted on missiles, launched from deep space, and guided to their targets. [2] the Orion bomber could use its 23,000 m/s of delta-V to enter a close hyperbolic flyby of Terra and release the warheads when near Terra.

On the one hand, the first option means the Orion does not have to get close to the target and be exposed to hostile weapons fire. On the other hand the missiles will have very limited delta-V because you cannot cram a full sized ICBM into the Orion bomber. True, the missiles will start with the Orion's orbital velocity but still. Since the paper cites enemy interceptor missiles requiring a day or two to reach the Orion bomber, presumably any missile the SSSWD launched will require a similar amount of time to reach the enemy cities.

The second option means the Orion bomber has to go into harms way. The up side is it can use its awesome amount of delta-V to deliver the MIRVs ballistically. And it probably can deliver the warheads to the target much quicker than any missile. One can just imagine the enemy generals freaking out at the sight of a three-hundred-ton spacegoing ICBM-farm dive-bombing you at hyperbolic speeds on a trail of freaking nuclear explosions while machine-gunning your continent with city-killer nukes.

According to the paper, a fleet of about 20 spacecraft would be deployed. Presumably this will ensure that there will always be several bombers close enough so that the MIRVs travel time will be short enough to give the enemy a major strategic problem. If my slide-rule is not lying to me, a 190,000 km-410,000 km orbit has an orbital period of 1,635,282 seconds or 18.9 days. With 20 SSSWD evenly spaced, that would have a bomber passing through perigee every 81,764 seconds or every 22.7 hours. I picked 410,000 km as a nice round value "beyond Luna" since the report did not give a precise figure. They might have selected an apogree figure to make a bomber pass through perigee once a day.

Siteing strategic nuclear weapons in deep space would be a major escalation of the nuclear arms race. Such Orion bombers are much more difficult to attack, compared to ICBMs in silos or nuclear submarines. It would require entirely new strategic planning and weapons systems. The high orbits mean that enemy weapons would require a day or more to reach the orbiting Orion bombers. If the enemy wishes to take out the Orion bombers simultaneously with the US ICBM silos and nuclear missle submarines, they will be forced to give the US a day or more of warning time. This sort of spoils the surprise of a first strike. In addition the long warning gives the Orion bombers ample time to take evasive action and/or deploy decoys and antimissile weapons.

On the minus side, such a drastic escalation may panic the enemy into starting a nuclear war before the Orion Bomber network was fully established. If the enemy is only half-panicked, they will probably start a crash-priority project to make their own Orion bomber network.

Asteroid Bombardment

If the attacker wants to just destroy the defender's civilization but does not want to necessarily make the defenders extinct or render the planet uninhabitable, asteroid bombardment might be just the thing. Now there is the chance of disrupting the ecosystem and rendering the planet temporarily uninhabitable, but at least it won't be radioactive.

Most solar systems have enough asteroids so the ammo is mostly free. All you have to supply is the delta-V to send them at the besieged planet at high velocity.

In a balkanized solar system, this is the reason for each space-faring nation to have their own Spaceguard. The idea is to prevent unauthorized changes in asteroid orbits. The idea for several independant national spaceguards is to keep all the spaceguards honest. Quis custodiet ipsos custodes? and all that.


(ed note: Terra had a pacifist society for about a century. Then they were invaded by the warrior Kzinti aliens. The Kzinti captured the colony on Alpha Centauri about fifty years ago, and make periodic attack on the solar system)

      (General Early said) "Right. Everyone knows that. Now think about it. We're facing a race of carnivores with a unified interstellar government of completely unknown size, organized for war. They started ahead of us, and now they've had Wunderland (Alpha Centauri III) and its belt for better than a generation. If nothing else, at this rate they can eventually swamp us with numbers. Just one set of multimegatonners getting through to Earth…"

     He puffed on the cigar with short, vicious breaths. (Captain) Jonah shivered inside himself at the thought: all those people (i.e., the population of Terra), dependent on a single life-support system… (i.e., the ecosphere of Terra) He wondered how flatlanders (people living on Terra) had ever stood it. Why, a single asteroid impact… (and pretty much everybody living on Terra would die)  The Belt was less vulnerable (the belters living in thousands of asteroid habitats). Too much delta vee required to match the wildly varying vectors of its scores of thousands of rocks, its targets weaker individually but vastly more numerous and scattered.

From THE CHILDREN'S HOUR by Jerry Pournelle and S. M. Stirling (1991)

      "What we're afraid of is a massive meteorite impact, something of asteroid size."
     The alien was silent for a time. Reynolds busied himself at the bar. Suddenly the alien said, "Thuktun Flishithy—Message Bearer—was docked to a moonlet of the ringed planet for many years. This many." The alien's trunk emerged from the mud, and he flexed a clump of four digits, three times. "Pushing. We were not told why. I once heard officers call the mass chaytnf."
     "What does it mean?"
     "It means this part of a fi." The alien rolled (and Sherry shied from a wave of mud). One broad clawed foot emerged.
     The sci-fi types all seemed to freeze in place; but Jenny didn't need their interpretation. Her hand closed painfully on Jack's arm. "My God. It's real. Of course, the Foot, they're planning to stomp us—"
     "They're talking too damn much."
     "Huh? The alien's talking a lot more than they are."
     The blurry voice from the TV set was saying, "It was not so large as many of the—asteroids—at the ringed planet. I think 8 to the 12th standard masses—"
     "Standard mass is your mass? About eight hundred pounds . . . Curtis took a pocket calculator out of his bush jacket. "Jesus! Twenty-seven billion tons!"
     Nat Reynolds said, "At . . . ten to twenty miles per second, that could—Harpanet, where are they going to drop it?"

(ed note: if I have not made a mistake in math, this will strike with force of about 1.25 x 1022 joules or 3,000,000 megatons. See boom table. Final crater diameter: 40.4 km, final crater depth: 901 meters, The volume of the target melted or vaporized is 78.2 km3. Roughly half the melt remains in the crater, where its average thickness is 144 meters. The novel says 4,000 megatons, so I'm only off by three orders of magnitude.)

     Commander Anton Villars stared through the periscope and tried to look calm. It wasn't easy. An hour before the message had come to USS Ethan Allen. The long-wave transmitters were reliable but slow. The message came in dots and dashes, code tapped out and taken down to be put through the code machines. It couldn't be orders to attack the Soviet Union. There was no Soviet Union. Villars had been prepared to launch his Poseidon missiles against an unseen enemy in space. Instead:
     Safe? From four thousand megatons? There wasn't any safety. Villars' urge was to submerge and flee at flank speed.
     Off to starboard, the island of Rodriguez blazed with the colors of life. Jungle had long since given way to croplands. In the center bare rock reared sharply, a peak a third of a mile high. Waves broke over a surrounding coral reef. That reef would provide more cover when the tsunami came, but it was a danger too.
     Fishing boats were straggling in through the reef. Probably doomed. There was nothing Villars could do for them.
     It was just dusk. Clouds covered the sky. It would be difficult to see anything coming. Four thousand megatons. Bigger than any bomb we ever dreamed of, much less built.
     The crew waited tensely. John Antony, the Exec, stood close by.
     "About time," Antony said.
     "If their estimate was on."
     "If their time was off, so were their coordinates."
     I know that. I had the same instructor at Annapolis as you did.
     Somebody laughed and choked it off. The news had filtered through the ship, as news like that always did.
     The cameras were working. Villars wondered how many would survive. He peered through the darkest filter available. Four thousand megatons . . .
     Suddenly the clouds were blazing like the sun. "First flash at 1854 hours 20 seconds," he called. "Log that." Where? Where would it fall?
     All in an instant, a hole formed in the clouds to the northeast, the glare became God's own flashbulb, and the cameras were gone. "Get those other cameras up," Villars bellowed at men who were already doing that. His right eye saw nothing but afterimage. He put his left to the periscope.
     He saw light. He squinted and saw light glaring out of a hole in the ocean. A widening hole in the ocean, with smoothly curved edges; wisps of mist streaming outward, and a conical floodlight beam pointing straight up. The beam grew wider: the pit was expanding. Clouds formed and vanished around a smoothly curved wall of water sweeping smoothly toward the sub.
     The rim of a sun peeped over the edge.
     "I make it about forty miles east northeast of present position. Okay, that's it." Villars straightened. "Bring in the cameras. Down periscope. Take us to ninety feet." How deep? The further down, the less likely we'll get munched by surface phenomena, but if those tsunamis are really big they might pile enough water on top of Ethan Allen to crush us. "Flank speed. Your course is 135 degrees." That leaves us in deep water and puts Rodriguez between us and that thing, for whatever good it'll do.
     So we've seen it. A sight nobody ever saw—well, nobody who wrote it down, anyway. Now all I have to do is save the ship.
     Ethan Allen was about to fight the biggest tsunami in human history—and just now he was broad on to it. He glanced at his watch. Tsunamis traveled at speeds from two hundred to four hundred miles an hour. Call this one four. Six minutes . . .
     "Left standard rudder. Bring her to 85 degrees."
     "Bring her to 85, aye, aye," the quartermaster answered.
     "Warn 'em," Villars said.
     "Now hear this. Now hear this. Damage control stations. Stand by for depth charges."
     Might as well be depth charges . . .
     The ship turned.
     It surged backward. Villars felt the blood rushing into his face. Somewhere aft, a shrill scream was instantly cut off, and the Captain heard a thud.
     Minutes later: "There's a current. Captain, we're being pulled northeast."
     "Steady as she goes." Goddam. We lived through it!

     The contorted moonlet dropped away, dwindled, vanished. Earth grew huge. A flashbulb popped above the Indian Ocean, and was replaced at once by a swelling, darkening fireball. Ring-shaped shadows formed and faded in and around it. Far from the central explosion, new lights blinked confusingly in points and radial streaks.
     The Earth's face streamed past, terrifyingly close but receding now. A wave in the cloud cover above the Indian Ocean raced outward, losing its circular shape as it traveled. Northward, it took on a triangular indentation, as if the edge of a blanket had snagged on a nail.
     "India," Dawson said. "How fast are you running this tape?"
     "Thirty-two times normal," Tashayamp answered.
     "What is . . . that?" Alice asked.
     "Land masses. The tsunami distorts the clouds," Arvid said.
     "So does the ocean floor," Dawson amplified, "but not as much. That's India going under. Those flashes would have been secondary meteors, debris, even water from the explosion thrown out to space and reentering the atmosphere."
     That's India going under. Good-bye, Krishna, and Vishnu the elephant god. Jeri shuddered. "Dave took me to India once. So many people. Half a billion."
     Arvid stood near. She felt his warmth and wanted to be closer to him.
     Tashayamp said, "Number?"
     Arvid said, "Eight to the eighth times eight times three."

(ed note: 402,653,184)

     "Human fithp in India? Where the wave goes now?"
     "Yes." ...
     ...The distortion in the clouds swept against Africa, then south. Here was clear air, and a ripple barely visible in the ocean . . . but the outline of the continent was changing, bowing inward.
     "Cape of Good Hope," Jeri muttered. She watched the waves spread into the Atlantic. Recorded hours must be passing. She found herself gasping and suspected she had been holding her breath. The waves were marching across the Atlantic, moving on Argentina and Brazil with deceptive slowness and a terrible inevitability.
     Cloud cover followed, boiling across the oceans, reaching toward the land masses. "My God," Jeri said. "How could you do this?"
     "It is not our choice," Raztupisp-minz said. "We would gladly have sent the Foot safely beyond your atmosphere, but your fithp would not have it so."
     "Look what you made me do," Alice said in a thick, self-pitying whine. Her voice became a lash. "All the sickies say that—the rogues say that when they've done something they're ashamed of. It was somebody else's fault."
     "They can say all they like," Carrie Woodward said. "We know. They came all the way from the stars to ruin the land."
     "You should not say such things," said Takpusseh. "You do not want this to happen again. You will help us."
     "Help? How?" Dawson demanded.
     "You, Wes Dawson, you tell them. More come."
     Dmitri spoke again in Russian. Arvid shuddered.
     The screen changed again. Clouds moved so unnaturally fast that Jeri thought they were still watching a tape until Takpusseh said. "That is now. Winterhome."
     Earth was white. The cloud cover was unbroken.
     "Rain. Everywhere," Nikolai said. "The dams are gone. There will be floods."

From FOOTFALL by Larry Niven and Jerry Pournelle (1985)

Laser Bombardment

First off, laser weapons used for ship-to-ship combat in the vacuum of space can use whatever laser wavelength they feel like. But things change if you are using laser cannons on ground targets of a planet with an atmosphere.

Wavelengths shorter than 200 nanometers (ultraviolet, x-rays, and gamma rays) are absorbed by Terra's atmospheric gases (so they are sometimes called "Vacuum frequencies"). Note that once a section of atmosphere has been heated into a plasma by the laser (or whatever) things change. Plasma is transparent to vacuum frequencies while non-vacuum frequences are absorbed.

Understand that a tunnel of plasma is only going to last for a fraction of a section so if you want to put a second laser bolt down it you'd better hurry.

And some wavelengths of infrared are absorbed by water vapor in the air. On Terran type habitable planets, moist air is everywhere. Naturally once the water vapor has been heated into plasma, it isn't water vapor any more. Just oxygen and hydrogen ions. Sadly plasma also absorbs infrared.


In the past, I have advocated for using "cyan" (bluish-green) lasers for orbital bombardment of Earth, mainly because of graphs like this:

This image basically plots how much light of a given frequency reaches the ground. E.g. 1m-wavelength radio waves aren't absorbed at all, visible light is absorbed a little bit, and 10nm UV is completely absorbed. We want a frequency that is not absorbed very much, and as high as possible so that we don't suffer diffraction losses.

Cyan is a sweet spot in this image: it's the furthest-left trough (i.e., highest-frequency, and therefore lowest-diffraction, band that doesn't get outright absorbed), and it's the bottom of that trough (i.e., the least-absorbed within that band).

Well, lately I got flustered with this graph for being too coarse. This graph looks like a cartoon sketch! I went looking for a better source and, well, it turns out not to exist. I mean, I can find tons of graphs that look like this, but none that have reasonable resolution (and preferably, data, so that I could reproduce it myself).

In-fact, the only detailed data that people seem to have even collected is in certain frequency ranges, notably the IR bands (ref. HITRAN, GEISA, etc. datasets, and the many projects that use them). In-particular, I played with HITRAN's buggy API for a while until I figured out they don't actually have data on the whole spectrum. However, I did find a graph:

It's basically the interesting section of the previous graph (inverted since it is transmittance rather than absorbance). It goes to 150nm, shorter than which we can be fairly confident will be absorbed by the atmosphere (such are called "vacuum frequencies" for a reason. You can still get sunburned by UV, so I assume that's basically the 300nm-400nm section of the last image that's still UV, but also nonzero transmission).

Now let's consider diffraction. To first order:

(divergence half angle) = (wavelength) / (π (aperture radius))
(spot radius) = (distance) (divergence half angle)
(irradiance) = (transmittance) (laser power) / (π (spot radius)²)
(damage rate) ∝ (irradiance)
(damage rate) ∝ π (transmittance) (laser power) ( (aperture radius) / ( (distance) (wavelength) ) )²

Considering distance, aperture radius, and available power to be constants with respect to the wavelength we choose, we can see that:

(damage rate) ∝ (transmittance) / (wavelength)²

To maximize damage rate, we simply have to take that graph and divide it by the x-axis-squared. Since the data was not available, I digitized the chart using WebPlotDigitizer, copied the approximate data out, and plotted it myself. In the graph below, you can see the original data in blue, and the effect of the division in orange.

The graph's peak says that a wavelength of about 400nm is optimal for orbital bombardment!

We can see that cyan (about 480nm) is close, at about 92% relative effectiveness. At least it's a better recommendation than green (which I also see bandied about: 532nm, 83% effectiveness).

400nm is pretty much the border between violet and ultraviolet, but in human perceptual terms it's not a binary cutoff. Under well-lit viewing conditions, the human eye sees best at about 555nm. At 400nm, a light source appears about 0.04% as bright—which might sound small, but the human visual system is logarithmic, and anyway a typical orbital-bombardment laser would use extremely high powers. As another reference: I've myself have 405nm lasers (expected 0.065% as bright) and they're plenty visible.

How general is this? Technically, it applies to surface-to-orbit/orbit-to-surface bombardment at a 70° surface-to-horizon angle. The main optical variation in the atmosphere is moisture content, but it turns out that water's transmission (for liquid or vapor) is actually coincidentally near-maximum at 400nm, so if anything more moisture will make every other wavelength even worse.

One thing that doesn't generalize is firing lasers from points on the surface to other points on the surface. In the first case, the exact height of the orbit didn't matter (it's orbital bombardment; one assumes you're above nearly all the atmosphere), but here, the path length within the atmosphere varies, meaning that the amount of absorption that you suffer at a given wavelength does too.

Given a particular range, one could measure/compute a graph like the above and get the optimal wavelength. Longer ranges will absorb more, making having a higher transmission coefficient (lower absorption coefficient) more important. But, because the Beer-Lambert law is nonlinear, there's little we can say else generally about such a graph.

Note: after the fact, I noticed that "MODTRAN", named on the source graph, is the name of a software package that computes such spectra. If it didn't cost $1800+, it'd be perfect. Of course, I could also wonder why no one hasn't just uploaded a reasonable-quality graph ever.

From a Google+ post by Ian Mallett (2018)


The US Navy is exploring the feasibility of using a high energy laser weapon as a ship-borne self-defense system against sea-skimming cruise missile attacks. Since the attenuation of laser energy by the atmosphere is the highest at low altitudes and varies with frequency, the selection of appropriate wavelengths becomes critical for a laser weapon to be effective. A high energy free electron laser (FEL) is suitable for employment in the envisaged role because it can be designed to operate at any desired frequency and, to a degree, is tunable in operation. This study aims to determine the optimal atmospheric windows for high energy, pico second, short pulse lasers.

Suitable wavelength windows were selected from either the Jan 1 or July 1, 2004 spectra for the date with a narrower transmittance window by meeting the following two criteria:

  1. Transmittance value of at least 90%, 95% and 99% respectively over a 10 km long, 10 m high horizontal path.
  2. Absorption coefficient value of less than 0.02 per km.

Table 5 summarizes the suitable wavelengths. The first four bands from 0.95 μm to 2.5 μm were able to meet the criteria of at least 90% transmittance and absorption coefficient of not more than 0.02 per km. However, there are no wavelengths in the 3.45 to 4.16 μm band that can meet the two specified criteria. The best wavelength window for this band is chosen for 70% transmission and absorption coefficient less than 0.04 per km.

From Table 5, the optimal wavelength windows for molecular atmospheric absorption are between 1.03 μm and 1.06 μm, and around 1.241 and 1.624 μm. This band provides a transmittance of more than 99%. However, as noted earlier, the main drawback of operating in a lower wavelength band is the strong extinction of energy from aerosol scattering.

Table 5.
Suitable wavelength windows for various values of T(z) in μm
T(z) > 90%
αabs < 0.01/km
T(z) > 95%
αabs < 0.005/km
T(z) > 99%
αabs < 0.001/km
T(z) > 70%
0.95 to 1.11 μm0.990 - 1.0750.992 - 0.998
1.002 - 1.006
1.01 - 1.067
1.030 - 1.060N/A
1.11 to 1.33 μm1.230 - 1.260
1.271 - 1.283
1.235 - 1.2561.241N/A
1.47 to 1.82 μm1.530 - 1.6801.535 - 1.565
1.58 - 1.595
1.610 - 1.660
2 to 2.5 μm2.125 - 2.140
2.220 - 2.245
3.45 to 4.16 μmN/AN/AN/A3.91 - 3.94

Summary of suitable wavelength bands for FEL operation for a 10 km horizontal path, 10 m above the ocean with no aerosol extinction.

(ed note: 400 nm equals 0.4 μm)


The possibility of using a laser beam as a ship-borne self-defense weapon has become more feasible with recent advancements in laser technology. The advantages of a high energy laser as a weapon are its key attributes of speed-of-light response, ability to handle fast maneuvering and crossing targets, deep magazine capacity, minimal collateral damage, target identification and adaptability for lethal to non-lethal employment. The attenuation of laser energy by the atmosphere is a result of molecular attenuation and scattering. Atmospheric scattering mainly disperses the energy of the laser beam but molecular absorption heats the atmosphere, reducing the index of refraction and thereby creating thermal blooming. The FEL has potential as a shipborne weapon system because it can be designed to operate at any desired frequency and, to a degree, is tunable in operation. The ability to select an operating frequency greatly enhances the successful propagation of the laser beam through the relatively dense air at low altitudes.

The objective of this thesis was to determine optimal operating wavelength bands for a high energy FEL weapon between 0.6 μm and 4.2 μm using the US Air Force PLEXUS Release 3 Version 2 program to set up MODTRAN 4 Version 2 and FASCODE 3 atmospheric transmission programs. Since PLEXUS and its user interface are export limited, this thesis was restricted to processing the MODTRAN and FASCODE output files. These codes allow for complex atmospheric transmittance and radiance calculations based on absorption and scattering phenomena for a variety of path geometries. The input parameters chosen for the simulation runs are meant to represent likely operational scenarios for ship self defense against a cruise missile attack. The main consideration was a 10 m altitude horizontal transmission path. Korea, Taiwan and the Persian Gulf were the three geographical areas chosen for the study. The effect of a short FEL laser pulse was modeled by convolving a normalized Gaussian frequency spectrum with the MODTRAN and FASCODE transmission and absorption coefficient spectra. The result of the convolution operation averages the transmittance values over a number of wavenumbers. The amount of averaging increases as the length of the FEL pulse decrease.

2. FASCODE Results

The higher resolution 0.1 cm-1 FASCODE was used to conduct further analysis on five selected bands or “windows” found from the MODTRAN results. Using the FASCODE aerosol extinction output file results, absorption coefficients for each wavenumber (or spectral frequency) were calculated. The molecular absorption coefficient is a key parameter for thermal blooming calculations. Data for the absorption coefficient were also used to compute the transmission spectrum for molecular absorption only. Using the transmission spectrum and absorption coefficient graphs, the optimal wavelength bands for employment of FEL at low altitudes were identified and summarized in Table 5. The four main bands of 0.95 to 1.11 μm, 1.11 to 1.33 μm, 1.47 to 1.82 μm, and 2 to 2.5 μm contain quite a number of suitable wavelengths that allow transmittance of at least 90% for a 10 km path and have absorption coefficient values of 0.02 per km or less. For a more stringent requirement of at least 99% transmittance, the suitable wavelength windows are between 1.03 to 1.06 μm and around 1.241 and 1.624 μm. However, the main concern for laser transmission through the atmosphere in the 1 μm region is the strong aerosol extinction.

Martin Marietta Zenith Star


      The Strategic Defense Initiative of the 1980's and early 1990's produced a large number of designs for launch vehicles and spacecraft. However, due to the security classification clamped down on much of the work done, relatively little of these designs has come to light. We are generally left with a smattering of artists impressions and sketches, with some often contradictory and usually not very informative descriptions.

     SDI was aimed at producing a "missile shield" able to defend the United States from a Soviet nuclear attack. Neutral particle beams, nuclear-pumped X-ray lasers, railguns, space-based missiles, ground based missiles and other science-fictiony technologies were all studied in some depth, with various levels of development. One of the more popular technologies, at least one of the more publicly visible and discussed, was the space based laser.

     Several types of laser are possible, with chemical lasers — deriving their vast power from the reaction of chemicals such as chlorine, fluorine and hydrogen — being among the most powerful, reliable and well understood. But even though such lasers had been built and demonstrated on the ground, actually reliably operating one in space, targeting warheads thousands of kilometers away, would require a great deal of development. And thus in 1987 the DoD began the Zenith Star program, aimed at orbiting a space based laser test system.

     Zenith Star, as designed by Martin Marietta circa 1988, was a two-component vehicle. The aft spacecraft was the Alpha laser, which combusted fluorine with hydrogen to generate around 2 megawatts of laser light; the forward spacecraft would contain the optics (including a 4-meter diameter main mirror) and aiming system, turning the beam of light from the Alpha laser into a tightly focused "ray" aimed at the target 60 to 300 kilometers away.

     Zenith Star was expected to fly in the mid 1990's, and, if successful, could have led to an operational space based laser around 2000. The collapse of the Soviet Union ended the threat of global thermonuclear war and ended support for the program.

     Each of the two Zenith Star components was to be launched atop a Titan IV booster. Alternative concepts called for launching the spacecraft as a single unit; in order to do this, a heavy lift booster would be needed. The Zenith Star Launch System was thus proposed, a new vehicle built from existing components such as the five seven-segment boosters from the Titan IV and a larger diameter Titan core with 5 LR-87 engines. Additionally the complete Zenith Star could be launched by a Shuttle C; the Zenith Star diagrams here were created in large part from a Shuttle C/Zenith Star configuration. Details of the Zenith Star are, perhaps unsurprisingly, hard to come by. The spacecraft is 15 feet in diameter and 81.25 feet long. Weight for the single-launch vehicle is given as about 86,800 pounds.



     The Zenith Star experiment (Figure i) is designed to demonstrate and evaluate the performance of a laser in space to answer critical issues relevant to SDI. This experiment is fully compliant with the restrictive interpretation of the 1972 Antiballistic Missile (ABM) Treaty. As such it does not directly perform all of the functions of a defensive system nor to the level required by an operational system. Its results however, do provide a measure of the potential of the operational systems by applying the appropriate appropriate scaling from the benchmarks achieved by it in space.

     The experiment (Figure 2) consists of a series of high power evaluations of beam control and a series of low power evaluations of the tracking and pointing functions of the system.

     The high power experiments evaluate the beam control by direct measurement of the far field beam performance with a high power target board. Both space propagation and upper atmospheric effects are measured.

     The low power experiments evaluate the tracking and pointing function performance while tracking a booster throughout its boost phase flight. The Agile Control Performance is evaluatd by performing structured characterization and large and small angle repointing of the system against a star field, small test objects (carried on board), and multiple boosters to exercise the system under multiple conditions.


     The basic hardward for the Zenith Star experiment is shown in Figure 3. It consists of a chemical laser of the class of the alpha program, a beam expander that utilizes the Large Advanced Mirror Program (LAMP) segmented mirror for the primary optical element, an actuator for pointing the beam expander, and an isolator for attenuating the laser noise from the beam expander. The latter two are combined into one subsystem called the actuator/isolator. The laser energy is directed through the aft body to the beam expander by a series of transfer optics and steering mirrors (beam control transfer assembly) on the aft body. A capture track system (consisting of a suite of sensors) is utilized to point the beam expander and optical train for tracking a series of test objects. The remainder of the equipment is a set of standard spacecraft subsystems that allow it to be in orbit as a free flyer that is commanded by ground operations personnel.

     The system is delivered into orbit by two Titan IV launch vehicles. The forward spacecraft is launched first and checked out completely. Then the aft spacecraft consisting of the Alpha laser and spacecraft support subsystems is launched into the same orbit as the first, orbit phased, and remotely operated from the ground for rendezvous and docking.


     The control architecture for the space based laser is derived from a series of stringent tracking and pointing requirements depicted in Figure 4 and the resulting interactive implications lead to a complex hierarchical control architecture. Tight accuracy and jitter requirements combined with the need for rapid repointing of the line-of-sight from one object to another necessitates isolation and suppression of disturbances to the large beam expander. The Zenith Star control system is designed to duplicate this architecture so that the experiment results can be directly related to the SBL performance.

     The precision and jitter are analogous to hitting a basketball on the Empire State Building in New York from Pike's Peak in Colorado. It must accomplish this while tracking objects at angular rates more than an order of magnitude higher than the capability of the Hubble Space Telescope. To accomplish this, the line-of-sight must be isolated from disturbances by as much as 100 million to one and yet be able to repoint from one object to another in less than one second so that the system effectiveness can be high.

     While the structure is made as stiff as possible, there is sufficient deformation (Figure 5) of the beam expander structure and optical geometry resulting in line-of-sight disturbances to require isolation of aft body noise from the beam expander. There are other self-induced beam expander disturbances such as fluid flow and rapid repointing that require structural disturbance suppression on the beam expander itself.

     Either technique can be readily handled without two body interaction, but when combined an actuator/isolator is required between the bodies. This actuator/isolator must provide six degrees of freedom operation which introduces other control issues, such as translation and beam walk control, that further complicate the controls problem.

     In order to ease the burden of pointing the line-of-sight of the system, a precision pointing set of controllers is introduced to provide beam expander off-axis pointing and stabilization so that the structure control can be relaxed within a small field of view and as shown in Figure 6. So long as the line-of-sight disturbance is within the range of the precision pointing controller authority the beam expander controller requirements are eased. In other words, the settling time is satisfied when the beam expander line-of-sight is within this band.


     The formulation of the control architecture for the beam expander can be described as follows in the next series of figures in Figure 7.

     An easy method of isolation (Figure 7a) of the aft body disturbances from the beam expander is to provide a gap between the forward and aft bodies, control the beam expander to point to the test object from on-board sensor data by external torques (such as control moment gyros), and control the aft body to follow this motion by external forces and torques to maintain the desired gap within some tolerance. This is ideal isolation since there is no actuation between the bodies to force alignment of the two bodies, hence there is no transfer of disturbances from one body to the other.

     Since each body tends to rotate about its own center of mass there will be large translational displacements (Figure 7b) at the optical interface between the beam expander and aft body. Also since the beam expander disturbances are to be minimized the aft body must be translated as well as rotated by external forces and torques to maintain the proper separation.- @h_s is not practical for a highly agile control system because of the large heavy aft body and the fact that the gap must be small, on the order of centimeters. Consequently an actuator between these bodies is required.

     This actuator introduces a coupling path from the aft body to the beam expander which then requires an isolator between the bodies (Figure 7c). This actuation and isolation must be combined into one subsystem because of this interaction This subsystem is called the actuator/isolator and it must minimize this coupling while producing the desired pointing forces and torques. This function is nontrivial even for the baseline magnetic isolator because of nonlinear magnetic forces and eddy currents which must be cancelled.

     Self-induced disturbances on the beam expander arising from fluid flow and rapid pointing must be dissipated through damping in the structure, transferred to noncritical structural motion (noncritical modes of transferred off the beam expander to the aft body (Figure 7d). The incorporation of the actuator/isolator allows this energy to be transferred to the aft body which can then remain isolated. Hence the beam expander line of sight can be stabilized while still tracking objects.

     The pointing of the beam expander causes severe disturbances. In order to move the line-of-sight from one object to another (rapid repointing) it is desirable to make maximum use of the available torque from the actuator/isolator. In fact, the optimal repointing for a rigid body is a bang-bang command. This, however, causes severe disturbances to the line-of-sight.

     The severity is dependent on the relationship of the angle to be repointed (frequency of the bang-bang torques) and the structural frequencies. Figure 8 shows the effects of a single structural frequency of 4 Hz and 8 Hz separately as a function of repointing angle. The time to hand over is the time that the line-of-sight error takes to settle to within the field of reguard of the beam expander where the fine off-axis steering takes over. The rigid body response is included since it represents the lower bound of maneuver time for the system.

     When all structural modes are considered the picture is not quite so easily displayed because the relative effects on the lineof- sight are intermixed. An envelope of these effects is indicated in Figure 9 where the lower bound is limited by the rigid body response and the upper bound depends on advanced structural controllability.

     The regions of interest for structural control are the torquelimited and rate-limited regions. The algorithm-limited region is the area of responsiveness of the precision off-axis control system for scene interpretation and control

     Figure 10 shows the improvement in repointing time that can be made by a simple modulation. The technique is based on the relationship of the repointingangle and the knowledge of the structural frequencies of the beam expander. By properly commanding or modulating the torque commands, disturbances can be minimized as shown in the figure for one technique called modulated bang-bang control.

     This technique concentrates on modal avoidance and cancellation and its effectiveness. There are other techniques that have been investigated by several members of the community that should also be evaluated in space. These include both other modal avoidance, modal suppression, and modal displacement.


     The space based laser control tasks are indeed challenging because of the variety of requirements that demand different types of controllers, all competing simultaneously. The architecture derived for the SBL resulted in a hierachical control formulation that demands advanced control techniques. Each portion of the architecture has interaction with the others which demands careful orchestration of the control commands to fulfill the control requirements.

     The Zenith Star duplicates the SBL functions and provides performance levels close enough to the SBL performance to provide valid scaling for evaluation of the SBL expectations.

     One dominant crucial control function is the beam expander controller. It must place and stabilize the beam expander lineof- sight within a few hundred microradians of the object tracked in a very short time. The accuracies involved require careful control of the structural deformations even with structural resonances on the order of 20 Hz.

     There is no precedence for this type of structure control since this is the first opportunity to control a structure of this nature in space. Experiments such as structural identification and modal surveys are also planned for in the experiment objectives. Utilization of other techniques for controlling the structure, such as distributed actuator structural control, are not currently available on Zenith Star but may be available in the future depending in the interest within the community and the risk to the other Zenith Star objectives.

     In either case there is ample opportunity for industry participation during the Zenith Star mission operations. This can be accomplished by submitting ideas for structural control techniques to SDIO for consideration. If approved, these experiment ideas will be integrated into the experiment objectives and the implementation incorporated into the mission planning.

Space Based Laser Control Complex & Challenging

  • Stressing Pointing & Tracking
  • Repointing in Short Time Requires New Control Thinking
  • Control Large Optical Structures Requires Interactive Control Strategies

Zenith Star Challenges Rival the SBL Control Difficulties

  • Pointing & Tracking is Severe
  • Repointing & Structural Control is Scaleable to SBL
  • Results from Beam Expander Control is First Attempt in Space

Zenith Star Offer Opportunity

  • Demonstrate & Validate Wide Variety of Structural Control Issues
  • Industry Wide Participation in Large Structure Experiments in Space

      On Nov. 24, 1987 during a visit to the Denver-based Martin Marietta Astronautics factory, President Reagan revealed for the first time the full dimensions and advanced status of the Zenith Star space-based laser demonstration project, a model of which is pictured on this page. Zenith Star is the Strategic Defense Initiative (SDI) continuation of the Defense Advanced Research Projects Agency space-based chemical laser program. The two major elements of Zenith Star are the LAMP mirror and the Alpha chemical laser, both of which elements have been demonstrated in laboratory experiments shown in the photographs.

     The SDIO has already awarded Martin Marietta, together with its primary subcontractors, Lockheed Missiles and Space Company and TRW, a Phase II contract for demonstrating the feasibility of a space-based laser experiment. The Alpha laser program is the most mature of the SDI's directed energy technologies. It is developing and validating key critical technologies neede to establish the feasibility of space-based ballistic missile defense.

     The simplicity of Alpha's construction and operation makes it a strong candidate for strategic defense. The Alpha laser system is constructed primarily of extruded aluminum, and derives its beam from a purely chemical reaction, which is also the primary source of energy for the laser. Tests have established that Alpha can prov'de the technology to realize sufficiently high power chemical lasers for strategic defense.

     The Alpha is the follow-on to the MIRACL (Mid-Infrared Advanced Chemical Laser). On Sept. 6, 1985 the MIRACL laser destroyed the second stage of a Titan I booster in tests conducted at the High Energy Laser System Test Facility at the White Sands Missile Range in New Mexico.

     The Alpha program is managed for the SDIO by the Air Force Weapons Laboratory. The prime contractor is TRW, Redondo Beach, California.

     The second major element of Zenith Star is LAMP (Large Advanced Mirror Program), shown in the third photograph. This program has demonstrated mirrors which are light enough to deploy in space. LAMP is the culmination of a decade and a half of R&D effort.

     The LAMP mirror is being used to study technology issues involved in utilizing large optics for strategic defense applications. Performance tests of the LAMP mirror will be completed in early 1988. The successful demonstration of this segmented LAMP mirror removes one of the major technology barriers to developing directed energy weapons.

     The LAMP program element is managed by the Rome Air Development Center. The rime contractor for the project is ITEK Corporation. Eastman Kodak fabricated the LAMP mirror's center segment.

Background and prospects

     As originally conceived, the Zenith Star project was to have demonstrated the essential elements of space-based laser missile defense before the end of 1988. But congressional budget cuts in the SDI progra , and the space shuttle Challenger disaster, have delayed the program up to several years.

     While the Zenith Star space flight test will demonstrate all of the combined technology elements for space-based laser missile defense, the system itself is not capable of effectively taking action against allistic missiles. But studies carried out over the past several years at TRW, and laboratory experiments on phase arrayed lasers at the Air Force Weapons Laboratory, show one interesting way in which Zenith Star could be directly scaled to achieve such a goal.

     Before going into this, though, it must be understood that the Zenith Star laser would carry out two distinct missions as part of a missile defense system. The first, which could be attained with a single module system, would utilize the Zenith Star to aid other types of missile interception systems through actively locating warheads in space and discriminating between decoys and real re-entry vehicles.

     The second mission is that of intercepting ballistic missions in their vulnerable boost phase. This would require much higher laser power levels and larger mirrors than are represented by a single Zenith Star module. But the work at TRW and the Air Force Weapons Lab shows how this deficiency could readily be overcome.

     TRW demonstrated that the technology already exists for constructing and operating extremely large mirror arrays in space. The idea is that many small mirrors can be ganged together in a phased array to act like a single large mirror. The small elements of the phased array can be mass produced and are therefore quite cheap. Systems acting like 100-meter-diameter mirrors are quite feasible. As TRW studies note, this virtually removes all limits on the power and brightness achievable with lasers.

     A complementary development at the Air Force Weapons Laboratory is that of phase arraye lasers. Experiments at this laboratory showed that many individual laser systems could be made to operate as a phased array. The result is that the combined output laser beam has an effective power density equal to that of the square of the number individual laser utilized. In other words 10 small lasers, when ganged in a phased array, would have the effective firepower of a single laser 100 times more powerful than the single small laser.

     Potentially, the net effect is quite dramatic. Many small laser modules, such as Zenith Star, could be operated as a phased array. By utilizing large phased array mirrors in geosynchronous orbit, orbiting lasers throughout the world could combine their firepower to achieve drfective output levels for intercepting missiles anywhere.

From ZENITH STAR: AN SDI DEMONSTRATION by Charles B. Stevens (1987)

Just because it never left the ground doesn't mean it didn't work.

From the moment he announced it on national television in March 1983, President Ronald Reagan's signature vision of a space-based ballistic-missile shield provoked excitement and incredulity. The Strategic Defense Initiative (SDI) spent nearly a decade pursuing cosmic lightsabers before the end of the Cold War seemingly ended its purpose.

Costs, technical challenges and treaty compliance concerns prevented a test of President Reagan's vision during his term. The closest he ever got to Star Wars was an elaborate stage set, a bit of theater just plausible enough to engage his imagination and the Soviets' fears.

Columnist Jack Anderson claimed that President-elect Reagan discussed his missile-defense ideas with Republican senators shortly after the 1980 election. At that time, the most promising directed-energy weapon looked like the high-power chemical laser. A chemical laser creates coherent (laser) light from intense chemical reactions, rather than by stimulating crystals or gases.

Shortly after its founding in 1984, SDI took over DARPA's directed-energy work. SDI's development plan led to a 1990 decision whether to proceed with a 1994 space test.

Chemical lasers lost their appeal in the face of potentially more powerful nuclear X-ray lasers, free-electron lasers and particle beams. But by 1986 it was clear that these exotic technologies were at least a decade away, and the White House wasn't willing to wait that long. The President cherished the hope of personally seeing his vision through.

There was also another reason: SDI chief Lt. Gen. James Abrahamson, a veteran of the Pentagon's early manned space program, believed the reality of a U.S. space-based laser—even just a testbed—would deter the Soviets from deploying countermeasures. Indeed, he hoped that the U.S. intention to test a Death Star would be sufficiently daunting to obviate the need to deploy the weapon at all!

In December of that year, Reagan made a secret decision to go ahead with an all-up Star Wars experiment as soon as possible. A crash program would deliver the first space-based test in 1990: four years earlier than originally planned. The program's classified code name was Zenith Star.

Zenith Star's components—its laser, focusing mirror, targeting and tracking systems—were already in various stages of development. It was to be a massive spacecraft, the size of a semi: eighty feet long, over forty feet in diameter, over forty-three tons’ mass. The weapon would have made up just one part of a multi-layered defense system. Its terrible heat ray could separate decoys from hardened warheads and blow up boosters, while other weapons attacked different targets.

Integration contractor Martin Marietta (now Lockheed Martin) proposed lofting this monster atop a super-sized version of its Titan missile, a four-engine beast appropriately named the Barbarian. Later iterations of the design split Zenith Star into two spacecraft, a laser module and a mirror-targeting module, for launching aboard less brawny boosters.

To instantly generate a megawatt of power, TRW's Alpha chemical laser would mix hydrogen and fluorine gas together much like a liquid-fueled rocket engine does. Light and heat from the the resulting reaction would then be converted into laser light and sent to a primary mirror wider than the one aboard the Hubble Space Telescope. Complex sensors and computers would track targets and aim the weapon's laser beam.

When fired, the Zenith Star weapon would have made a spectacular sight. As incandescent hydrogen fluoride from the turbo-reactor roared out the exhaust ports to form a gigantic gaseous cross, a seven-foot-wide lightsaber blade hotter than the Space Shuttle's engines would spear into the darkness to vaporize metal and detonate rocket fuel thousands of miles away.

Sometime in 1987, President Reagan got his wish to see his vision. At a speech he gave to the workers at Martin Marrieta's Denver plant he stood in front of life-size mock-ups of Zenith Star and its Barbarian booster.

Aerospace historian Scott Lowther has posted some frames from a video taken of the event. Wrapped in gold foil, its exhaust port hatches open and its huge mirror bright, the giant prop emblazoned with the Stars and Stripes suggested how serious Reagan's vision was becoming.

The Zenith Star mockup itself had an interesting history. According to the Encyclopedia Astronautica,

"That model was a refurbished version of a Manned Orbiting Laboratory (MOL) metal mock-up made in the 1960s. When the MOL program was cancelled, the useless bit of tankage had been sold as scrap to a Colorado farmer. It had to be purchased back for the Zenith Star demonstration. It required quite a bit of cleaning and repainting since it had been lived-in for a while by itinerant travellers."

But the impressive mock-up was a long way from the real thing, and not just because it was a prop. By 1989, when the General Accounting Office examined the program, every component was a year or more behind schedule. A skeptical Democratic Congress refused to fully fund a program they thought both impractical and dangerous—dangerous especially to arms-control treaties.

The collapse of the Soviet Union and the end of the Cold War doomed Zenith Star. By 1991, when the Alpha laser was publicly revealed, President Reagan's grand vision had morphed into a smaller enterprise focused on conventional anti-missile missiles. The same challenges bedeviling Zenith Star's development still plague the U.S. missile defense program. America's battlestar sank into obscurity.

But all that money and effort produced more than a movie set. A very great deal about directed-energy weapons was learned; most of it's still classified. In the generation since Zenith Star, advances in computers, optics and power have solved many of the problems daunting the weaponeers of the 1980s.

President George W. Bush's withdrawal from the Anti-Ballistic Missile treaty in 2001 dropped the legal constraints on space weapons tests that challenged Zenith Star. Megawatt-class non-chemical lasers are on the horizon. A lot of real magic can go on behind all the smoke and mirrors.

Burning Glass

This is a ludicrous orbital bombardment weapon popular in science fiction in the early previous century. Presumably some cruel little boy incinerated some ants on a sunny day using their magnifying glass, and when they grew up to write science fiction they figured scaling it up would be a good idea. Upscale the ants into enemy cities, and upscale the magnifying glass into a titanic parabolic mirror. In space.

TV Tropes calls it the Solar-Powered Magnifying Glass

The main drawback is the mirror would be a hard-to-miss kilometer wide target possessing all the tensile strength of aluminium foil. One nuclear missile and months of work instantly frizzles up like, well, ants under a magnifying glass.

This material is presented here mostly for its entertainment value.


Heat ray

Archimedes may have used mirrors acting collectively as a parabolic reflector to burn ships attacking Syracuse. The 2nd century AD author Lucian wrote that during the Siege of Syracuse (c. 214–212 BC), Archimedes destroyed enemy ships with fire. Centuries later, Anthemius of Tralles mentions burning-glasses as Archimedes' weapon. The device, sometimes called the "Archimedes heat ray", was used to focus sunlight onto approaching ships, causing them to catch fire. In the modern era, similar devices have been constructed and may be referred to as a heliostat or solar furnace.

This purported weapon has been the subject of ongoing debate about its credibility since the Renaissance. René Descartes rejected it as false, while modern researchers have attempted to recreate the effect using only the means that would have been available to Archimedes. It has been suggested that a large array of highly polished bronze or copper shields acting as mirrors could have been employed to focus sunlight onto a ship.

A test of the Archimedes heat ray was carried out in 1973 by the Greek scientist Ioannis Sakkas. The experiment took place at the Skaramagas naval base outside Athens. On this occasion 70 mirrors were used, each with a copper coating and a size of around five by three feet (1.5 by 1 m). The mirrors were pointed at a plywood mock-up of a Roman warship at a distance of around 160 feet (50 m). When the mirrors were focused accurately, the ship burst into flames within a few seconds. The plywood ship had a coating of tar paint, which may have aided combustion. A coating of tar would have been commonplace on ships in the classical era.

In October 2005 a group of students from the Massachusetts Institute of Technology carried out an experiment with 127 one-foot (30 cm) square mirror tiles, focused on a mock-up wooden ship at a range of around 100 feet (30 m). Flames broke out on a patch of the ship, but only after the sky had been cloudless and the ship had remained stationary for around ten minutes. It was concluded that the device was a feasible weapon under these conditions. The MIT group repeated the experiment for the television show MythBusters, using a wooden fishing boat in San Francisco as the target. Again some charring occurred, along with a small amount of flame. In order to catch fire, wood needs to reach its autoignition temperature, which is around 300 °C (570 °F).

When MythBusters broadcast the result of the San Francisco experiment in January 2006, the claim was placed in the category of "busted" (or failed) because of the length of time and the ideal weather conditions required for combustion to occur. It was also pointed out that since Syracuse faces the sea towards the east, the Roman fleet would have had to attack during the morning for optimal gathering of light by the mirrors. MythBusters also pointed out that conventional weaponry, such as flaming arrows or bolts from a catapult, would have been a far easier way of setting a ship on fire at short distances.

In December 2010, MythBusters again looked at the heat ray story in a special edition entitled "President's Challenge". Several experiments were carried out, including a large scale test with 500 schoolchildren aiming mirrors at a mock-up of a Roman sailing ship 400 feet (120 m) away. In all of the experiments, the sail failed to reach the 210 °C (410 °F) required to catch fire, and the verdict was again "busted". The show concluded that a more likely effect of the mirrors would have been blinding, dazzling, or distracting the crew of the ship.

From the Wikipedia entry for ARCHIMEDES

I have for many years been a fan of the webcomic Schlock Mercenary. Hardish, humorous military sf with some nice, long-term plotting.

In the current plotline (some spoilers ahead) there is an enormous Chekov’s gun: Earth is surrounded by an equatorial ring of microsatellites that can reflect sunlight. It was intended for climate control, but as the main character immediately points out, it also makes an awesome weapon. You can guess what happens. That leds to an interesting question: just how effective would such a weapon actually be?

From any point on Earth’s surface only part of the ring is visible above the horizon. In fact, at sufficiently high latitudes it is entirely invisible – there you would be safe no matter what. Also, Earth likely casts a shadow across the ring that lowers the efficiency on the nightside.

I guessed, based on the appearance in some strips, that the radius is about two Earth radii (12,000 km), and the thickness about 2000 km. I did a Monte Carlo integration where I generated random ring microsatellites, checking whether they were visible above the horizon for different Earth locations (by looking at the dot product of the local normal and the satellite-location vector; for anything above the horizon this product must be possible) and were in sunlight (by checking that the distance to the Earth-Sun axis was more than 6000 km). The result is the following diagram of how much of the ring can be seen from any given location:

At most, 35% of the ring is visible. Even on the nightside where the shadow cuts through the ring about 25% is visible. In practice, there would be a notch cut along the equator where the ring cannot fire through itself; just how wide it would be depends on the microsatellite size and properties.

Overlaying the data on a world map gives the following footprint:

The ring is strongly visible up to 40 degrees of latitude, where it starts to disappear below the southern or northern horizon. Antarctica, northern Canada, Scandinavia and Siberia are totally safe.

This corresponds to the summer solstice, where the ring is maximally tilted relative to the Earth-Sun axis. This is when it has maximal power: at the equinoxes it is largely parallel to the sunlight and cannot reflect much at all.

The total amount of energy the ring receives is E0 = π(ro2 - ri2)|sin(θ)|S where ro is the outer radius, ri the inner radius, θ the tilt (between 23 degrees for the summer/winter solstice and 0 for equinoxes) and S is the solar constant, 1.361 kW/square meter. This ignores the Earth shadow. So putting in θ = 20° for a New Years Eve firing, I get E0 ≈ 7.6×1016 Watt.

If we then multiply by 0.3 for visibility, we get 23 petawatts – is nothing to sneeze at! Of course, there will be losses, both in reflection (likely a few percent at most) and more importantly through light scattering (about 25%, assuming it behaves like normal sunlight). Now, a 17 PW beam is still pretty decent. And if you are on the nightside the shadowed ring surface can still give about 8 PW. That is about six times the energy flow in the Gulf Stream.

How destructive would such a beam be? A megaton of TNT is 4.18 PJ. So in about a second the beam could produce a comparable amount of heat. It would be far redder than a nuclear fireball (since it is essentially 6000K blackbody radiation) and the IR energy would presumably bounce around and be re-radiated, spreading far in the transparent IR bands. I suspect the fireball would quickly affect the absorption in a complicated manner and there would be defocusing effects due to thermal blooming: keeping it on target might be very hard, since energy would both scatter and reflect. Unlike a nuclear weapon there would not be much of a shockwave (I suspect there would still be one, but less of the energy would go into it).

The awesome thing about the ring is that it can just keep on firing. It is a sustainable weapon powered by renewable energy. The only drawback is that it would not have an ommminous hummmm….

Addendum 14 December: I just realized an important limitation. Sunlight comes from an extended source, so if you reflect it using plane mirrors you will get a divergent beam – which means that the spot it hits on the ground will be broad. The sun has diameter 1,391,684 km and is 149,597,871 km away, so the light spot 8000 km below the reflector will be 74 km across. This is independent of the reflector size (down to the diffraction limit and up to a mirror that is as large as the sun in the sky).

At first this sounds like it kills the ring beam. But one can achieve a better focus by clever alignment. Consider three circular footprints arranged like a standard Venn diagram. The center area gets three times the solar input as the large circles. By using more mirrors one can make a peak intensity that is much higher than the side intensity. The vicinity will still be lit up very brightly, but you can focus your devastation better than with individual mirrors – and you can afford to waste sunlight anyway. Still, it looks like this is more of a wide footprint weapon of devastation rather than a surgical knife.

From A SUSTAINABLE ORBITAL DEATH RAY by Anders Sandberg (2020)


But like any other technical achievement the space mirror could also be employed for military purposes and, furthermore, it would be a most horrible weapon, far surpassing all previous weapons. It is well known that fairly significant temperatures can be generated by concentrating the sun's rays using a concave mirror (in a manner similar to using a so-called "burning glass"). Even when a mirror has only the size of the human hand, it is possible to ignite a handheld piece of paper or even wood shavings very simply in its focus (Figure 95).

Imagine that the diameter of a mirror of this type is not just 10 cm, but rather several hundreds or even thousands of meters, as would be the case for a space mirror. Then, even steel would have to melt and refractory materials would hardly be able to withstand the heat over longer periods of time, if they were exposed to solar radiation of such an enormous concentration.

Now, if we visualize that the observer in the space station using his powerful telescope can see the entire combat area spread out before him like a giant plan showing even the smallest details, including the staging areas and the enemy's hinterland with all his access routes by land and sea, then we can envision what a tremendous weapon a space mirror of this type, controlled by the observer in orbit, would be!

It would be easy to detonate the enemy's munitions dumps, to ignite his war material storage area, to melt cannons, tank turrets, iron bridges, the tracks of important train stations, and similar metal objects. Moving trains, important war factories, entire industrial areas and large cities could be set ablaze. Marching troops or ones in camp would simply be charred when the beams of this concentrated solar light were passed over them. And nothing would be able to protect the enemy's ships from being destroyed or burned out, like bugs are exterminated in their hiding place with a torch, regardless of how powerful the ships may be, even if they sought refuge in the strongest sea fortifications.

They would really be death rays! And yet they are no different from this lifegiving radiation that we welcome everyday from the sun; only a little "too much of a good thing." However, all of these horrible things may never happen, because a power would hardly dare to start a war with a country that controls weapons of this dreadful nature.

(ed note: The above section, translated into English appeared in Science Wonder Stories September 1929)

(The Problem of Space Travel: The Rocket Motor) by Hermann Noordung (1929)

In the question of the material of this reflector, it is clear that 1) no oxygen mst be present, and 2) it must heat up but little itself. It will remain colder if we leave the back side rough or even paint it black. As material, I would suggest sodium which, under the respective conditions, has a specific weight of 1, considerable tensile strength, and a silvery lustre. It can be taken along in large pieces by the shigle rockets and, since it still has the usual temperature up above, can there be rolled out to sheeting or pressed out as wire or strap from the rocket. Joining of the single pieces as well as polishing can be done by men in divers' suits. If the reflecting plate is 0.005 mm thick and the wires, etc., have the sane mss as the plate, the whole weighs 10 g per square metre or 100 kg per hectare. With regular rocket traffic to the observer station, the ascent of one rocket, which, beside all else, can carry up 2,000 kg of sodium, costs 8,000 to 60,000 Mark all told. Thus, one hectare of reflector costs at the most 3,500 Mark altogether. If we figure that 1 hectare of reflector surface could make 3 hectares of polar land arable, we see that a time my come when this reflector and the whole invention becomes a paying proposition.

In this way, a reflector 100 km in diameter would, at the most, cost 3 billion Mark and, if 100,000 kg of sodium were taken a loft every week, it would require ca 15 years to build it. Since such a reflector could, unfortunately, also have high strategic value (munitions factories can be exploded with it, tornadoes and thunderstorms produced, marching troops and their reserves destroyed, whole cities burned, and generally the greatest of damage done) the possibility is not excluded that one of the civilized states will make use of this invention in the foreseeable future, the more so since a large part of the invested capital could also bear interest in peace time.

(Ways to Spaceflight) by Hermann Oberth (1929)

On our back cover this month artist Julian S. Krupa has painted his conception of the most powerful weapon that could ever be devised. He has envisioned an artificial satellite that could be built in space and set to circling the earth just as the moon does, on an orbit perhaps 10,000 miles above the surface, well out of the atmosphere, and at a height best calculated to make it effective over a wide radius. Its potency is manyfold.

First, and primarily, it is a sun power machine. It utilizes the rays of the sun in a very simple manner, yet an extremely powerful one. We all have used a small magnifying glass, or a concave mirror to concentrate the rays of the sun. We all know how easy it is to burn a piece of paper, or wood with a mirror only an inch or two in diameter. Therefore, all these giant mirrors, concentrating sunlight on a single spot, would create a heat ray far beyond the imaginings of any science fiction writer in its deadly effectiveness.

In the accompanying illustration, Krupa has shown the space devastator in operation, sending a ravaging beam of terrible heat down upon a defenseless city 10,000 miles below. With such a threat hanging over it, what nation could afford to become a belligerent? It would be forced to settle its differences in a peaceful manner, according to the dictates of the committee, country, or police force placed in control of the space devastator. War would be impossible with such a potent "big stick" to hold over ambitious warlords and dictators. (note the blind assumption that ambitious warlords and dictator would never be in control of the space devastator. Or that the committee, country, or police force would never be controlled by some evil corporation that purchases politicians.)

Second, and perhaps more important, is the use of this artificial satellite in peaceful pursuits. There are numberless tasks it could perform. It could provide daylight in a normal manner, impossible to differentiate from the real thing. It could provide daylight illumination on any area, during times of flood, disaster, storm, or tragedy where daylight would be a vast help in rescue work.

It could control weather to a great degree, breaking up storm formations, cloud areas, or stopping blizzards. Conversely, it could create cloud formations by drawing up ocean moisture. It could provide aid to crops needing sunlight. It could melt snow from storm-bound cities. (yes indeed it could warm the globe…)

Imagine a destructive hurricane, sweeping in from the sea, toward the large cities of Florida. It could be driven like a herd of helpless cattle before the intense heat of the rays from the space devastator. It could even be destroyed, dissipated, halted in its progress.

Even the tremendous cost of this artificial satellite would be a mere trifle beside the savings it could effect, and the wealth it could create. As a guardian angel in the prevention and lessening of disaster, its value would be inestimable.

The savings in electrical power in lighting a great city would be enormous. Also, power could be generated in enormous amounts through the building of giant steam generators in isolated areas. Heat from a concentrated sunbeam would provide steam to operate giant turbines. Sun power stations would supplant water power stations, at a much cheaper original cost and upkeep.

Other strange uses, of great practicality, would be numerous. Icebergs could be melted and destroyed as a menace to shipping. A northern shipping route could be kept open the year around. Arctic ship travel could be made possible. Jungle lands could be cleared by the simple expedient of burning away the jungle, leaving a rich ashy loam of great agricultural value (actually cleared jungle land is almost totally agriculturally worthless. And it is too bad if you render extinct some rare herb that contains a cancer cure or something).

Areas of disease and plague could be cleared of germs by constant sunlight. Malaria zones could be freed of mosquitoes. Health centers of constant sunshine could be operated.

The livable areas of the earth could be increased by thirty percent, by moderation of climate, control of ice and snow, and of rain. Deserts could be made livable through artificially induced rainfall. The Sahara, the Gobi, the American deserts could be made fruitful. Tobacco, cotton, corn crops could be controlled (very telling the relative ranking of crops there). Disastrous droughts, excess and ruinous rainfall could be prevented.

Third, assuming the foregoing to apply directly to the present, the future value of such a space machine can easily be imagined. Interplanetary travel would be vastly benefited by the facility of such stations as a means of communication between planets and space ships in the void. Signals would be sent by code light flashes, and range would be unlimited. Weather or static conditions would have no effect on communication by light rays between worlds.

Also, this machine would act as a spacial lighthouse, guiding incoming space ships to the proper landing areas. Ships not actually landing on the planet could also use the space devastator as a way station, discharging passengers or freight, to be relayed to earth in small rocket ships (oh yes, let's make the ultimate weapon into grand central station with zillions of people of all nations passing through. What could possibly go wrong? The only thing saving the situation is the zillions of spies and secret agents from various nations would be constantly tripping over each other.).

The problem of building such a space machine as this is not as complicated as it would seem. Once space travel is an actuality, materials could be transported to the orbit selected for the space devastator, and once placed in this position, would remain there. Workmen could assemble them in space, and the machine would be built on the "site." Once completed, it would be firmly anchored in its place, its course mathematically computed by astronomers, and its every function thereafter subject only to mathematical calculation. Not one, but many, serving humanity.

From SPACE DEVASTATOR by Julian Krupa (1939)

Here is the story of a future war; a war between Mars and Earth. Artist Paul has shown a possible weapon.

MODERN aviation, and the great success of aerial blitzkrieg warfare, has shown us that in the future, the rocket ship, and the space ship, will play a very important part in the wars of the future. We all hope that there will be no such wars, but judging from past experience, it seems as inevitable as the present war.

Let us try to imagine what a raid from space, say from Mars, would be like. First, let us picture the New York of the year 2000. It is a vast city, with tremendous skyscrapers, and it is Earth’s largest city. It is logical to assume that a smashing blow against such a gigantic metropolis as the city of that era will be, would play a great part in determining the outcome of such a future war. So, let us say that at high noon, we are flying over New York in our sport model racing plane. We have no thought of war in our mind, and all seems peaceful below.

But suddenly, above us, we hear a growing roar, and down from space dart three huge space ships. Space ships are not unusual, because in this world of the year 2000, space travel is an accomplished fact, and space liners ply the void just as airliners cross the oceans today. Therefore, we aren’t surprised.

But we are puzzled when the three ships take up position above the city, rather than landing at the space port. They form a ring, and begin to speed about in a huge circle.

From each ship a tiny beam breaks out, to meet in the middle. We see that some change is taking place in the atmosphere. By some electrical magic, a gigantic whirlpool, in disc-shape, is being formed out of the air. This disc is heated by electrical discharges, and to our amazement it grows until it becomes, in effect, a giant atmospheric lens, just as capable of concentrating the sunlight as a lens of glass would be.

As the atmospheric lens suddenly begins to send its ray of fiery sunlight down in concentrated fury, we realize the truth. New York is being raided by the Martians. And they are using the most horrible weapon ever devised.

Whole blocks of New York burst into flame, turn black as charcoal under the terrific heat. The city rapidly becomes overhung with a pall of smoke, and we realize that immense destruction is going on. This is terrible. New York is helpless beneath such a weapon.

Now, up from the city’s airports come the battle planes of our air force. But they are flying against the most powerful creations of the aviation industry. They are flying against atomic powered space ships.

Like deadly lances, the electrical rays leap out, catching our fighting planes, and explode their gasoline tanks. Down they go, flaming funeral pyres for the men in them.

What can we do?

But, as we hover in helpless horror, our own space-fighting craft arrive, speedy ships armed with powerful atomic cannons. But strangely, they do not attack the heavier armed battleships of space, with their deadly rays. Instead, as we wonder what is happening, they dart higher, up above the deadly lens, and from their bellies they loose a cloud of smoke. Back and forth they weave, forming a cloud blanket that cuts off the source of the great atmospheric lens’ potency, the ordinary noon-day sunlight.

Here we have the Martians at a disadvantage. Due to their circular formation, and the necessity of maintaining it, they cannot move swiftly in a horizontal direction. They have one recourse, and that is to break formation, and dart away.

But now, like deadly hawks, the Earth ships dart down through the smoke screen, dive-bombing as no modem bomber could, and firing streams of atomic shells.

Down go the Martian ships, blasted to bits. But the war has begun. Mars has lost three battleships. Earth has had its greatest city devastated. Where will it all end? War grows constantly more horrible. What will the next attack be? Only the future, and the science of aviation can tell.

(For the purposes of illustration, artist Paul has shown the sunlight beam above as well as below the atmospheric lens. Actually, there would be no beam visible above it, and it would not be visible directly below the lens, but would become brighter as it concentrated, until at the ground, it would be hot enough to melt steel instantly —Ed.)

From NEW YORK INVADED by Henry Gade (1941)

The sun gun or heliobeam is a theoretical orbital weapon, which makes use of a concave mirror mounted on a satellite, to concentrate rays from the sun on to a small area of the Earth's surface, destroying targets or killing through heat.


The Scottish mathematician John Napier proposed such a device. In his book Secrete Inventionis (1596), he published details of a giant mirror to burn enemy ships by focusing the sun's rays on them.

In 1929, the German physicist Hermann Oberth developed plans for a space station from which a 100-metre-wide concave mirror could be used to reflect sunlight onto a concentrated point on the earth.

Later during World War II, a group of German scientists at the German Army Artillery proving grounds at Hillersleben began to expand on Oberth's idea of creating a superweapon that could utilize the sun's energy. This so-called "sun gun" (Sonnengewehr) would be part of a space station 8,200 kilometres (5,100 mi) above Earth. The scientists calculated that a huge reflector, made of metallic sodium and with an area of 9 square kilometres (900 ha; 3.5 sq mi), could produce enough focused heat to make an ocean boil or burn a city. After being questioned by officers of the United States, the Germans claimed that the sun gun could be completed within 50 or 100 years.

Uses in popular culture

In the film Die Another Day, the twentieth installment in the James Bond series of films, the primary antagonist of the film, fictional British billionaire Gustav Graves (in reality the alias of the assumed-to-be-dead North Korean Colonel Tan Sun-Moon), constructs an orbital sun gun code-named "Icarus" for the use of cutting a path through the Korean Demilitarized Zone and allowing North Korean troops to invade South Korea. The device was disabled after its control console is destroyed.

A similar concept is used in the Resident Evil: Revelations video game. In the game, a special satellite code-named Regia Solis is used to provide a city with clean energy but at full capacity it is powerful enough to destroy said city or other targets.

In the TV series Scorpion episode "Sun of a Gun", Walter O'Brien's fictional alter ego and his team are sent alongside their friend Sylvester Dodd's estranged father to an African dictator's country to investigate his discovery of a Nazi World War II sun gun project.

In the Star Wars Legends book Wedge's Gamble, Rogue Squadron commandeers an orbital solar reflector (used for power generation) is used to boil ocean water in an effort to generate a large enough storm to knock out power on the planet (Coruscant) below.

From the Wikipedia entry for SUN GUN


Nazi men of science seriously planned to use a man-made satellite as a weapon for conquest.

In Germany last month U.S. Army technical experts came up with the astonishing fact that German scientists had seriously planned to build a “sun gun,” a big mirror in space which would focus the sun's rays to a scorching point at the earth's surface. The Germans, the Army reported, hoped to use such a mirror to burn an enemy city to ashes or to boil part of an ocean. Many U. S. newspaper readers, remembering the eerie success of V-1 and V-2. swallowed nervously.

Plausible schemes to build a station in space were engineered on paper long before the war. European rocket enthusiasts, including Dr. Hermann Oberth, who may have been the designer of V-2 (no, it wasn't him), had planned to use the space station not as a weapon but as a refueling point for rockets starting off on journeys into space. The station would revolve around the earth like a tiny man-made moon, obeying the gravitational laws of all heavenly bodies. The centrifugal force of its motion would exactly balance the earth's gravitational pull. Men would live inside the station, breathing an artificial atmosphere. The only major obstacle: constructing a rocket powerful enough to reach a point where a space station could be built. If the modern German scientists had been able to make such a rocket, they might have been able to set up their sun gun. Whether the sun gun would have accomplished what they expected, however. is another matter.


The German idea of using the sun as a military weapon is not new. There is an ancient legend that Archimedes designed great burning mirrors which set the Roman fleet afire during the siege of Syracuse, in which Archimedes later died. This legend. and the German plan for huilding a sun gun, may be proved physically impossible by a simple axiom of optics. This is that light cannot he brought to a sharp, pointed focus with lenses or mirrors unless it comes from a sharp, pointed light source. Since the sun appears in the sky as a disk and not as a point, the best any optical system can produce is an image of this disk. At very short focal lengths the image is small and hot but as the focal length is increased the image becomes progressively bigger and cooler. At the distance the Germans proposed to set up their mirror (5,100 miles) the image of the sun cast on the earth would he about 40 miles in diameter and not hot enough to do any damage.

From THE GERMAN SPACE MIRROR Life Magazine July 23, 1945

(ed note: this is a bit of over-the-top space opera for entertainment purposes. No, it doesn't work that way in the real world. But it makes just enough sense for space opera.

E. E. "Doc" Smith's LENSMAN series pioneered the problem of the Lensman Arms Race. The readers were thrilled at the super-colossal gee-whiz super-weapon that was invented in the last book. But the author is stuck with the "how do you top that?" conundrum. Can't disappoint the readers or they will stop buying your books.

In the last novel the valiant members of the Galactic Patrol found that the overwhelming battle fleets of the evil Boskonians were too much to handle. So they mounted huge faster-than-light drives on planets, and used two such planets to crush the enemy planet like a cosmic-scale hammer and anvil. They gave it the picturesque name of "Nutcracker." The novel ends with the hero thinking that it is Miller Time.

At the start of the next novel (taking place about ten seconds after the end of the prior novel), the hero's Mentor slaps him alongside his head and tells him to use his brain. The hero thinks a few seconds, and comes to the horrible realization that the evil Boskone empire will reproduce the mobile planet weapon in a few months. Terra will die under the nutcracker treatment unless our hero can come up with an even more super-colossal weapon.)

Kinnison went. And, wonder of wonders, he took Sir Austin Cardynge with him.

From solar system to solar system, from planet to planet, the mighty Dauntless hurtled at the incomprehensible velocity of her full maximum blast; and every planet so visited was the home world of one of the most cooperative—or, more accurately, one of the least non-cooperative—members of the Conference of Scientists. For days brilliant but more or less unstable minds struggled with new and obdurate problems; struggled heatedly and with friction, as was their wont. Few if any of those mighty intellects would have really enjoyed a quietly studious session, even had such a thing been possible.

Then Kinnison returned his guests to their respective homes and shot his flying warship-laboratory back to Prime Base. And, even before the Dauntless landed, the first few hundreds of a fleet which was soon to be numbered in the millions of meteor-miners' boats began working like beavers to build a new and exactly-designed system of asteroid belts of iron meteors.

And soon, as such things go, new structures began to appear here and there in the void.

Comparatively small, these things were; tiny, in fact, compared to the Patrol's maulers. Unarmed, too; carrying nothing except defensive screen. Each was, apparently, simply a power-house; stuffed skin full of atomic motors, exciters, intakes, and generators of highly peculiar design and pattern. Unnoticed except by gauntly haggard Thorndyke and his experts, who kept dashing from one of the strange craft to another, each took its place in a succession of precisely-determined relationships to the sun.

Between the orbits of Mars and of Jupiter, the new, sharply-defined rings of asteroids moved smoothly. Most of Grand Fleet formed an enormous hollow hemisphere. Throughout all nearby space the surveying speedsters and flitters rushed madly hither and yon. Uselessly, apparently, for not one needle of the vortex- detectors stirred from its zero-pin.

Kinnison was even less easy in his mind. He was not afraid of negaspheres (giant spheres of antimatter), even if Boskonia should have them; but he was afraid of fortified, mobile planets. The super-maulers were big and powerful, of course, but they very definitely were not planets; and the big, new idea was mighty hard to jell. He didn't like to bother Thorndyke by calling him—the master technician had troubles of his own—but the reports that were coming in were none too cheery. The excitation was wrong or the grid action was too unstable or the screen potentials were too high or too low or too something.

Sometimes they got a concentration, but it was just as apt as not to be a spread flood instead of a tight beam. To Kinnison, therefore, the minutes fled like seconds—but every minute that space remained clear was one more precious minute gained.

Then, suddenly, it happened. A needle leaped into significant figures.

Relays clicked, a bright red light flared into being, a gong clanged out its raucous warning. A fractional instant later ten thousand other gongs in ten thousand other ships came brazenly to life as the discovering speedster automatically sent out its number and position; and those other ships—surveyors all—flashed toward that position and dashed frantically about. Theirs the task to determine, in the least number of seconds possible, the approximate location of the center of emergence (of the enemy fleet).

Flotillas, squadrons, sub-fleets flashed smoothly toward their newly-assigned positions. Super-maulers moved ponderously toward theirs. The survey ships, their work done, vanished. They had no business anywhere near what was coming next. Small they were, and defenseless; a speedster's screens were as efficacious as so much vacuum against the forces about to be unleashed. The power houses also moved.

Maintaining rigidly their cryptic mathematical relationships to each other and the sun, they went as a whole into a new one with respect to the circling rings of tightly-packed meteors and the invisible, non-existent mouth of the Boskonian vortex (the opening of the Boskonian stargate where their fleet and nutcracker planets will emerge).

Planets. Seven of them. Armed and powered as only a planet can be armed and powered; with fixed-mount weapons impossible of mounting upon a lesser mobile base, with fixed-mount intakes and generators which only planetary resources could excite or feed. Galactic Civilization's war-vessels fell back. Attacking a full-armed planet was no part of their job. And as they fell back the super-maulers moved ponderously up and went to work. This was their dish; for this they had been designed. Tubes, lances, stillettoes of unthinkable energies raved against their mighty screens; bouncing off, glancing away, dissipating themselves in space-torturing discharges as they hurled themselves upon the nearest ground. In and in the monsters bored, inexorably taking up their positions directly over the ultra-protected domes which, their commanders knew, sheltered the vitally important Bergenholms (FTL drives) and controls. They then loosed forces of their own. Forces of such appalling magnitude as to burn out in a twinkling of an eye projector-shells of a refractoriness to withstand for ten full seconds the maximum output of a first-class battleship's primary batteries!

The resultant beam was of very short duration, but of utterly intolerable poignancy. No material substance could endure it even momentarily. It pierced instantly the hardest, tightest wall-shield known to the scientists of the Patrol. It was the only known thing which could cut or rupture the ultimately stubborn fabric of a Q-type helix.

Hence it is not to be wondered at that as those incredible needles of ravening energy stabbed and stabbed and stabbed again at Boskonian domes every man of the Patrol, even Kimball Kinnison, fully expected those domes to go down.

But those domes held. And those fixed-mount projectors hurled back against the super-maulers forces at the impact of which course after course of fierce-driven defensive screen flamed through the spectrum and went down.

     "Back! Get them back!" Kinnison whispered, white-lipped, and the attacking structures sullenly, stubbornly gave way.
     "Why?" gritted Haynes. "They're all we've got."
     "You forget the new one, chief—give us a chance."
     "What makes you think it'll work?" the old admiral flashed the searing thought. "It probably won't—and if it doesn't…"
     "If it doesn't," the younger man shot back, "we're no worse off than now to use the maulers. But we've got to use the sunbeam now while those planets are together and before they start toward Tellus (Terra)."
     "QX, ("OK")" the admiral assented; and, as soon as the Patrol's maulers were out of the way:
     "Verne?" Kinnison flashed a thought. "We can't crack 'em. Looks like it's up to you—what do you say?"
     "Jury-rigged—don't know whether she'll light a cigarette or not—but here she comes!"

     The sun, shining so brightly, darkened almost to the point of invisibility.
     War-vessels of the enemy disappeared, each puffing out into a tiny but brilliant sparkle of light.
     Then, before the beam could effect the enormous masses of the planets, the engineers lost it. The sun flashed up—dulled—brightened—darkened—wavered. The beam waxed and waned irregularly; the planets began to move away under the urgings of their now thoroughly scared commanders.
     Again, while millions upon millions of tensely straining Patrol officers stared into their plates, haggard Thorndyke and his sweating crews got the sunbeam under control—and, in a heart-stopping wavering fashion, held it together. It flared—sputtered—ballooned out—but very shortly, before they could get out of its way, the planets began to glow. Ice-caps melted, then boiled. Oceans boiled, their surfaces almost exploding into steam. Mountain ranges melted and flowed sluggishly down into valleys. The Boskonian domes of force went down and stayed down.

     "QX, Kim—let be," Haynes ordered. "No use overdoing it. Not bad-looking planets; maybe we can use them for something."
     The sun brightened to its wonted splendor, the planets began visibly to cool—even the Titanic forces then at work had heated those planetary masses only superficially.

The battle was over.

     "What in all the purple hells of Palain did you do, Haynes, and how?" demanded the Z9M9Z's captain.
     "He used the whole damned solar system as a vacuum tube!" Haynes explained, gleefully.
     "Those power stations out there, with all their motors and intake screens, are simply the power leads. The asteroid belts, and maybe some of the planets, are the grids and plates. The sun is—"
     "Hold on, chief!" Kinnison broke in. "That isn't quite it. You see, the directive field set up by the…"
     "Hold on yourself!" Haynes ordered, briskly. "You're too damned scientific, just like Sawbones Lacy. What do Rex and I care about technical details that we can't understand anyway? The net result is what counts—and that was to concentrate upon those planets practically the whole energy output of the sun. Wasn't it?"
     "Well, that's the main idea," Kinnison conceded. "The energy equivalent, roughly, of four million one hundred and fifty thousand tons per second of disintegrating matter."
     "Whew!" the captain whistled. "No wonder it frizzled 'em up."

From SECOND STAGE LENSMAN by E. E. "Doc" Smith (1941)

Relativistic attack

If the invaders are attacking the planet using relativistic weapons, it is more or less game over. There really is no realistic defense, unless the defenders are a Kardashev type II civilization. The problem is light-speed lag. Since the r-bombs are traveling so near the speed of light, they are only a little bit behind the wave of photons announcing their presence. In other words, you only see where they were, not where they are now. From the target's point of view, they would suffer from the optical illusion of the r-bomb apparently moving faster than light. Before you had time to react, the r-bombs would hit with all their devastating effects.

The thing to keep in mind is that all the energy the r-bomb releases has to be put into it in the first place. It takes an astronomical amount of energy to accelerate an object up to 92% lightspeed. If your civilization has managed to anger another civilization who has access to that much energy, you already know you are in deep trouble.

Bombardment in Fiction


      In parks and open spaces, overcrowding problems had forced the erection of hideous, ten-storey tenements. They filled every square and open space like brown, untidy bricks.
     “You think that bad?” Hengist seemed to be reading Duncan’s thoughts, or perhaps his expression. “You didn’t see it as it was, when I was a kid …” He stopped and flicked the spent cigarette into the disposal slot “That was a long time ago. Maybe it was a dream, but you should see the DA.”
     “Devastated areas. The Vrenka got into the system twice. Know what pin-wheels are?”
     “They’re a type of revolving firework, aren’t they ?”
     “Correct. The Vrenka had a weapon like that. Imagine a pin-wheel a mile in diameter spinning and slithering around a bare two feet above ground. It left a trail of grassy slag behind, a glowing pathway a mile on either side—pouf! Heat rushed out at head level, doors crashed in and upper windows blew out. The roofs and upper stories of even the highest buildings suddenly went bam, geysered upwards as if a tornado had started on the ground floor and howled its way out at the top …” He let the sentence trail away and shook himself as if suddenly awakening. “There are worse things than Vrenka spinners, however.”

     “Not cheerful. I have never been there but I’ve seen pictures. Thousands of miles of graveyard is not an inspiring subject for study, and there is an unpleasant story about it, too.”
     “Hengist told me they got through with what he called spinners.”
     “Spinners and other things, mostly heat-generating weapons. The worst part is, although it is not generally known, the Vrenka had never tried for the home planet until one of the suicide vessels got through and clobbered theirs. As you will see, there were no half measures. I don’t know what the solar bombs did to Vrenka but they certainly hit back fast and hard.”
     Duncan looked down and suppressed a gasp. It was far worse than Gaynor had suggested.
     Below, the torn and blackened land was pitted, cratered and twined with unnatural canals. They were still too high for details but here and there were piles of jagged ruins which might once have been cities. White strips, terminating abruptly on the lips of craters, marked the beginnings and ends of what might once have been major highways.
     The vessels were still descending slowly and the two men began to distinguish details.
     Craters, which in the course of years had filled with water had become lakes, and the whole area twisted and twined with unnatural canals.
     Cities appeared to have fallen in on themselves and flown together liquidly like wax models exposed to a hot sun.
     Duncan saw one immense building, bent or melted into a huge arch, its upper storey resting in the glazed ruins on the opposite side of what had once been a main street. It had been golden once but it was now a muddy, discoloured brown. It looked like a huge and dirty half-melted candle into which someone had cut the shapes of windows.
     Across the channel the destruction was even worse. Canals and winding areas of glassy slag crossed and re-crossed like the silvery trails of giant snails. The few buildings which had not melted to shapelessness were jagged and hooked like black fingers reaching from the earth and clutching desperately at nothing.

From THE PRODIGAL SUN by Philip E. High (1964)

There was no sign of the wolverines. Thorvald moved along the pocket southward, and Shann followed him. Once more they faced a dead end. For the crevice, with the sheer descent to the river on the right, the cliff wall at its back, came to an abrupt halt in a drop which caught at Shann's stomach when he ventured to look down.

If some battleship of the interstellar fleet had aimed a force beam across the mountains of Warlock, cutting down to what lay under the first layer of planet-skin, perhaps the resulting wound might have resembled that slash. What had caused such a break between the height on which they stood and the much taller peak beyond, Shann could not guess. But it must have been a cataclysm of spectacular dimensions. There was certainly no descending to the bottom of that cut and reclimbing the rock face on the other side. The fugitives would either have to return to the river with all its ominous warnings of trouble to come, or find some other path across that gap which now provided such an effective barrier to the west.

From STORM OVER WARLOCK by Andre Norton (1960)

Canyon (p Eridani A II) does not quite follow the usual rules for planets.

The planet is not much bigger than Mars. Until a few hundred years ago its atmosphere was just dense enough to support photosynthesis-using plants. The air held oxygen, but was too thin for human or kzinti life. The native life was as primitive and hardy as lichen. Animal had never developed at all.

But there were magnetic monopoles in the cometary halo around Canyon's orange-yellow. sun, and radioactives on the planet itself. The Kzinti Empire swallowed the planet and staffed it with the aid of domes and compressors. They called it Warhead, for its proximity to the unconquered Pierin worlds.

A thousand years later the expanding Kzinti Empire met human space.

The Man-Kzin wars were long over when Louis Wu was born. Men won them all. The kzinti have always had a tendency to attack before they are quite ready. Civilization on Canyon is a legacy of the Third Man-Kzin War, when the human world Wunderland developed a taste for esoteric weapons.

The Wunderland Treatymaker was used only once. It was a gigantic version of what is commonly a mining tool: a disintegrator that fires a beam to suppress the charge on the electron. Where a disintegrator beam falls, solid matter is rendered suddenly and violently positive. It tears itself into a fog of monatomic particles.

Wunderland built, and transported into the Warhead system, an enormous disintegrator firing in parallel with a similar beam to suppress the charge on the proton.

The two beams touched down thirty miles apart on Canyon's surface. Rock and kzinti factories and housing spewed away as dust, and a solid bar of lightning flowed between the two points. The weapon chewed twelve miles deep into the planet, exposing magma throughout a region the size and shape of Baja California on Earth, and running roughly east and west. The kzinti industrial complex vanished. The few domes protected by stasis fields were swallowed by magma, magma that welled higher in the center of the great gash before the rock congealed.

The eventual result was a sea surrounded by sheer cliffs many miles high, surrounding in turn a long, narrow island.

Other human worlds may doubt that the Wunderland Treatymaker ended the war. The Kzinti Patriarchy is not normally terrified by sheer magnitude. Wunderlanders have no such doubts.

Warhead was annexed after the Third Man-Kzin War, and became Canyon. Canyon's native life suffered, of course, from the gigatons of dust that dropped on its surface, and from the loss of water that precipitated within the canyon itself to form the sea. In the canyon there is comfortable air pressure and a thriving pocket-sized civilization.

From RINGWORLD ENGINEERS by Larry Niven (1979 )

(ed note: The Ulant aliens are attacking Terra. The Terran planet of Canaan was bracing for the attack, when the alien fleet contemptuously by-passed the planet as beneath its notice. This injured the pride of the president of Canaan.

The president ordered the entire planet onto a war footing, devoting their entire industrial output to producing arms and supplies for the Terran war fleet. Canaan also became the staging base for Terra's fleet of raider starships, who prey upon the Ulant's logistics chain.

The Ulants are in a bind. If they ignore Canaan, their logistics convoys are decimated and the Terran fleet becomes well supplied. But if they attack Canaan, this will stall the attack on Terra and could end the entire war. So they try to split the difference and only do limited planetary attacks on Canaan.

The protagonist is a soldier turned war correspondant who wants to witness the action first hand. He has the misfortune of being sent to his warship right at the same time the Ulants schedule a major planetary attack.)

      The personnel carrier lurches through the ruins under a wounded sky. The night hangs overhead like a sadist’s boot, stretching out the moment of terror before it falls. It’s an indifferent brute full of violent color and spasms of light. It’s an eternal moment on a long, frightening, infinite trail that loops back upon itself. I swear we’ve been around the track a couple of times before.
     I decide that a planetary siege is like a woman undressing. Both present the most amazing wonders and astonishments the first time. Both are beautiful and deadly. Both baffle and mesmerize me, and leave me wondering, What did I do to deserve this?
     A twist of a lip or a quick chance fragment can shatter the enchantment in one lethal second.
     I look at that sky and wonder at myself. Can I really see beauty in that?

     Tonight’s raids are really showy.
     Moments ago the defensive satellites and enemy ships were stars in barely perceptible motion. You could play guessing games as to which were which. You could pretend you were an old-time sailor trying to get a fix and not being able because your damned stars wouldn’t hold still.
     Now those diamond tips are loci for burning spiders’ silk. The stars were lying to us all along. They were really hot-bottomed arachnids with their legs tucked in, waiting to spin their deadly nets. Gigawatt filaments of home-brew lightning come and go so swiftly that what I really see is afterimages scarred on my rods and cones.
     Balls of light flare suddenly, fade more slowly. There is no way of knowing what they mean. You presume they are missiles being intercepted because neither side often penetrates the other’s automated defenses. Occasional shooting stars claw the stratosphere as fragments of missile or satellite die a second death. Everything consumed in this holocaust will be replaced the moment the shooters disappear.
     I hear the Commander’s chuckle and look his way. He’s a dim, golden-haired silhouette against the moonlight. He’s watching me. “They’re only playing tonight,” he says. “Drills, that’s all. Just training drills.” His laugh explodes like a thunderous fart. (demonstrating his low opinion of the morons who told him the Ulants were just going do small training drills, instead of a major offensive push)
     There is a big explosion up top. For an instant the ruins become an ink-line drawing of the bottommost floor of hell. Forests of broken brick pillars and rusty iron that present little resistance to the shock waves of the attackers’ weapons. Every single one will tumble someday. Some just demand more attention.
     “We looked Turbeyville over on our way here,” I say, and Yanevich nods. “I saw enough.”
     The Fleet’s big on-planet headquarters is buried beneath Turbeyville. It gets the best of the more serious drops.
     The Commander and I had looked around while the dust was settling from the latest. The moons had been in conjunction nadir the previous night. That weakens the defense matrix, so the boys upstairs jumped through the hole with a heavy boomer drop. They replowed several square kilometers of often-turned rubble. They do it for the same reason a farmer plows a fallow field. It keeps the weeds from getting too tall.
     The Commander says it was a tease strike. Just something to keep the edge on their boys and let us know our upstairs neighbors may come to stay someday.
     The abandoned surface city lay immobilized in winter’s tight grasp when we arrived. The iron skeletons of buildings creaked in bitter winds. All those mountains of broken brick lay beneath a rime of ice. In the moonlight they looked as though herds of migrating slugs had left their silvery trails upon them.
     A handful of civilians prowled the wastes, hunting dreams of yesterday. The Old Man says the same ones come out after every raid, hoping something from the past will have worked to the surface. Poor Flying Dutchmen, trying to recapture annihilated dreams.
     A billion dreams have already perished. This conflict, this furnace of doom, will consume a billion more. Maybe it feeds on them.
     The Pits are another popular target. The boys upstairs can’t resist. They’re the taproot of Climber Command’s logistics tree, the point where the strength of Canaan coalesces for transfer to the Fleet. The Pits spew men, stores, and materiel like a full-time geyser.
     All they ever reclaim is leave-bound Climber people (crews of raider starships) wearing the faces of concentration camp escapees.
     Now I can feel the earth tremors generated by departing lifters. They leave at ten-second intervals, ‘round Canaan’s! twenty-two-hour and fifty-seven-minute clock. They come in varying sizes. Even the little ones are bigger than barns. They are simply gift boxes packed with goodies for the Fleet.
     The Commander wants me. He’s leaning toward me, wearing his mocking grin. “Three klicks to go. Think we’ll make it?”
     I ask if he’s giving odds.
     His blue eyes roll skyward. His colorless lips form a thin smile. The gentlemen of the other firm are playing with bigger firecrackers now. The flashes splatter his face, tattooing it with light and shadow.
     Something is going on upstairs. It makes me nervous. The aerial show is picking up. This isn’t any drill. The interceptions are taking place in the troposphere now. Choirs of ground-based weapons are testing their voices. They sing in dull crackles and booms. The carrier’s roar and rumble only partially drown them.
     Halos of fire brand the night.
     A violin-string tautness edges Yanevich’s words as he observes, “Drop coming down.”
     I want to see, too. “How long before the dropships arrive?”
     I’ve seen the tapes. My seat harness feels like a straitjacket. Caught on the ground, in the open. The enemy coming. A Navy man’s nightmare.
     They don’t bother with my question. Only the enemy knows what he’s doing. That adds to my unease.
     Marines, Planetary Defense soldiers, Guardsmen, they can handle the exposure. They’re trained for it. They know what to do when a raider bottoms her drop run. I don’t. We don’t. Navy people need windowless walls, control panels, display tanks, in order to face their perils calmly.
     Even Westhause has run out of things to say. We watch the sky and wait for that first hint of ablation glow.
     Turbeyville boasted a downed dropship. It was a hundred meters of Stygian lifting body half-buried in rubble. There is a stop frame I’ll carry a long time. A tableau. Steam escaping the cracked hull, colored by a vermilion dawn. Very picturesque.
     That boat was pushing mach 2 when her crew lost her, yet she went in virtually intact. The real damage happened inside.
     I decided to shoot some interiors. One look changed my mind. The shields and inertial fields that preserved the hull juiced its occupants. Couldn’t tell they had been guys pretty much like us, only a little taller and blue, with mothlike antennae instead of ears and noses. Ulantonids, from Ulant, their name for their homeworld. “Those chaps got an early out,” the Commander told me. He sounded as if he envied them.
     “Looks like we’ll get in ahead of them,” Yanevich says.
     I check the sky. I can’t fathom the omens he’s reading.
     The surface batteries stop clearing their throats and begin singing in earnest. The Commander gives Yanevich a derisive glance. “Seems to be sh*t flying everywhere, First Officer.”
     “Make a liar out of me,” the Lieutenant growls. He flings a ferocious scowl at the sky.
     Eye-searing graser flashes illuminate the rusting bones of once-mighty buildings.
     The first dropship whips in along the carrier’s backtrail, taking us by surprise. Her sonic wake seizes the vehicle, gives it one tremendous shake, and deafens me momentarily. Somehow the others get their hands to their ears in time. The dropper becomes a glowing deltoid moth depositing her eggs in the sea.
     “There’s some new lifters that’ll need to be built,” Westhause says. “Let’s hope what we lost were Citron Fours.”
     My harness is suddenly a trap. Panic hits me. How can I get away if I’m strapped down?
     The Commander touches me gently. His touch has a surprisingly calming effect. “Almost there. A few hundred meters.”
     The carrier stops almost immediately. “You’re a prophet.” It’s a strain, trying to sound settled. That damned open sky mocks our human vulnerability, throwing down great bolts of laughter at our puniness.
     A second dropper cracks overhead and leaves her greetings. A lucky ground weapon has bitten a neat round hole from her flank. She trails smoke and glowing fragments. She wobbles. I missed covering my ears again. Yanevich and Bradley help me out of the carrier.
     Bradley says, “Bad shields on that one.” He sounds about two kilometers away. Yanevich nods.
     “Wonder if they’ll ever get her back up.” The First Watch! Officer commiserates with fellow professionals.

     Half a hundred production and packaging lines chug along below us. Their operators work on a dozen tiers of steel grate. The cavern is one vast, insanely huge jungle gym, or perhaps the nest of a species of technological ant. The rattle, clatter, and clang are as dense as the ringing round the anvils of hell. Maybe it was in a place like this that the dwarfs of Norse mythology hammered out their magical weapons and armor.
     Jury-rigged from salvaged machinery, ages obsolete, the plant is the least sophisticated one I’ve ever seen. Canaan became a fortress world by circumstance, not design. It suffered from a malady known as strategic location. It still hasn’t gotten the hang of the stronghold business.
     “They make small metal and plastic parts here,” Westhause explains. “Machinedparts, extrusion moldings, castings. Some microchip assemblies. Stuff that can’t be manufactured on TerVeen.”
     The boomer drop was rough for me. I could see and hear Death on my backtrail. It was personal. Those droppers were after me.
     Navy people seldom see the whites of enemy eyes. Line ships are toe to toe at 100,000 klicks. These men are extending the psychology of distancing.
     The Commander says the TerVeen go was a holiday junket. Like taking a ferry across a river. The gentlemen of the other firm were busy covering their dropships.
     TerVeen isn’t a genuine moon. It’s a captive asteroid that has been pushed into a more circular orbit. It’s 283 kilometers long and an average 100 in diameter. Its shape is roughly that of a fat sausage. It isn’t that huge as asteroids go.
     The support system wakened us when the lifter entered TerVeen’s defensive umbrella. There’re no viewscreens in our compartment, but I’ve seen tapes. The lifter will enter one of the access ports which give the little moon’s surface a Swiss cheese look. The planetoid serves not only as a Climber fleet base, but also as a factory and mine. The human worms inside are devouring its substance. One great big space apple, infested at the heart.
     The process began before the war. Someone had the bright idea of hollowing TerVeen and using it as an industrial habitat. When completed, it was supposed to cruise the Canaan system preying on other asteroids. One more dream down the tubes.
     I ask one of my questions. “Why doesn’t the other firm bring in a Main Battle Fleet? It shouldn’t be that hard to scrub Canaan and a couple of moons.”
     “They’re stretched too thin trying to blitz the Inner Worlds. The guys bothering us are trainees. They hang out here a couple of months, getting blooded, before they take on the big time. When we get out there it’ll be a different story. The reps on those routes are pros. There’s one Squadron Leader they call the Executioner. He’s the worst news since the Black Death.”
     I’m getting tired of Westhause’s voice. It takes on a pedantic note when he knows you’re listening.
     “Suppose they committed that MBF? It would have to come from inside. That would stall their offensive. If we carved it up, they’d lose the initiative. And we might cut them good.
     “Climbers get mean when they’re cornered.” A hint of pride has crept in here.
     “Meaning they can’t afford to take time out to knock us off, but they can’t afford to leave us alone, either?”
     “Yeah. Containment. That’s the name of their game.”
     “The holonets say we’re hurting them.”
     “Damned right we are. We’re the only reason the Inner Worlds are holding out. They’re going to do something…”
     Westhause continues to explain. “What they did was drill the tunnels parallel to TerVeen’s long axis. They were cutting the third one when the war started. They were supposed to mine outward from the middle when that was finished. The living quarters were tapped in back then, too. For the miners. It was all big news when I was a kid. Eventually they would’ve mined the thing hollow and put some spin on for gravity. They didn’t make it. This tunnel became a wetdock. A Climber returns from patrol, they bring her inside for inspections and repairs. They build the new ones in the other tunnel. Some regular ships too. It has a bigger diameter.”
     In Navy parlance a wetdock is any place where a ship can be taken out of vacuum and surrounded by atmosphere so repair people don’t have to work in suits. A wetdock allows faster, more efficient, and more reliable repairwork.
     “Uhm.” I’m more interested in looking than listening.
     “Takes a month to run a Climber through the inspections and preventive maintenance. These guys do a right job.”
     I try to watch the work going on out in the big tunnel. So many ships! Most of them are not Climbers at all. Half the defense force seems to be in for repairs. A hundred workers on tethers float around every vessel. No lie-in-the-comer refugees up here. Everybody works. And the Pits keep firing away, sending up the supplies.
     Sparks fly in mayfly swarms as people cut and weld and rivet. Machines pound out a thunderous industrial symphony. Several vessels are so far dismantled that they scarcely resemble ships. One has its belly laid open and half its skin gone. A carcass about ready for the retail butcher. What sort of creature feeds on roasts off the flanks of attack destroyers?
     Gnatlike clouds of little gas-jet tugs nudge machinery and hull sections here and there. How the devil do they keep track of what they’re doing? Why don’t they get mixed up and start shoving destroyer parts into Climbers?
     A Climber appears. It looks clean. Very little micrometeorite scoring, even. “Doesn’t look like there’s anything wrong with that one.”
     “The critical heat-sensitive stuff gets replaced after every patrol. The laser weaponry, too. Takes too long to break it down and scan each part. Somebody back down the tube will get ours. We’ll get something that belonged to somebody who’s on patrol already.”
     A whole, combat-ready Climber looks like an antique spoked automobile wheel and tire with a ten-liter cylindrical canister where the hub belongs. Its exterior is fletched with antennae, humps, bumps, tubes, turrets, and one huge globe riding high on a tall, leaning vane reminiscent of the vertical stabilizer on supersonic atmosphere craft. Every surface is anodized a Stygian black.
     There are twelve Climbers in the squadron. They cling to a larger vessel like a bunch of ticks. The larger vessel looks like the frame and plumbing of a skyscraper after the walls and floors are removed. This is the mother, the command and control ship. She’ll carry her chicks into the patrol sector and scatter them, then pick up any patrolling vessels that have expended their missiles and need rides home.
     Though a Climber can space for half a year and few patrols last longer than a month, Command wants no range sacrificed getting to the zone, nor any stores expended. Stores are a Climber’s biggest headache, her Achilles’ heel. By their nature the vessels pack a lot of hardware into tightly limited space. There’s little room left for crew or consumables.
     Our mother ship is one of several floating in a vast bay. The others have only a few Climbers suckered on. Each is kept stationary by a spiderweb of common rope. The ropes are the only access to the vessel. “They don’t waste much on fancy hardware.” Tractors and pressors would stabilize a vessel in wetdock anywhere else in the Fleet. Vast mechanical brows would provide access.
     “Don’t have the resources,” Westhause says. “‘Task-effective technological focus,’” he says, and I can hear the quotes. “They’d put oars on these damned hulks if they could figure out how to make them work. Make the scows more fuel-effective.”
     A mother-locked Climber can be entered only through a hatch in the “top” of its central cylinder. The hatch isn’t an airlock. It’ll remain sealed through the vessel’s stay in vacuum. The ship’s only true airlock is at its bottom. That’s connected to the mother now. Surrounding it is a sucker ring through which the Climber draws its sustenance till it’s released for patrol. Power and water. And oxygen. Through the hatch itself will come our meals, though not prepared. Through that hatch, too, will come our orders, moments before we’re weaned.
     Westhause is explaining the airlock system. “The only reverse flow consists of wastes,” he concludes.
     “And you give that any significance you want,” the Commander mutters. “Sh*t for sh*t, I say. Down the hatch, men.”

From PASSAGE AT ARMS by Glen Cook (1985)

Londo Mollari: Refa, any force attempting to invade Narn would be up to its neck in blood—its own!

Lord Refa: We have no intention of invading Narn. Flattening it, yes—but invading it? We will be using mass drivers. By the time we are done their cities will be in ruins, we can move in at our leisure!

Londo Mollari: Mass drivers? They have been outlawed by every civilized planet!

Lord Refa: These are uncivilized times.

Londo Mollari: We have treaties!

Lord Refa: Ink on a page!

Capt. John Sheridan: Any news?

Cmdr. Susan Ivanova: Just rumors. They say the Centauri are using mass drivers. I can't believe they'd resort to planetary bombardment!

Capt. John Sheridan: Right now I'd believe just about anything.

From Babylon 5: The Long, Twilight Struggle by J. Michael Straczynski (1995)

The Moon Is A Harsh Mistress

In the novel, the lunar colony is fed up with the yoke of Terran oppression and stages their very own war of independence. Among their assets is a large external mass driver (called a "catapult") ordinarily used to send shipments of grain back to Terra. The colonists weaponize it, firing cannisters of steel-belted solid rock as orbital bombardment weapons.

(ed note: "Mike" is the supercomputer that controls and maneuvers the cannisters from the catapult. The text is the internal dialog of the main character, who is a native Russian speaker. This explains his broken English. "F.N." is the Federated Nations, the world government and "owner" of the lunar colony and all the inhabitants. TANSTAAFL is an acronym for There Ain't No Such Thing As A Free Lunch)

     LuNoHoCo was an engineering and exploitation firm, engaged in many ventures, mostly legitimate. But prime purpose was to build a second catapult, secretly.

(ed note: colonists know that once they start lobbing cannisters as weapons, their catapult will become the priority military target)

     Operation could not be secret. You can’t buy or build a hydrogen-fusion power plant for such and not have it noticed. (Sunpower was rejected for obvious reasons.) Parts were ordered from Pittsburgh, standard UnivCalif equipment, and we happily paid their royalties to get top quality. Can’t build a stator for a kilometers-long induction field without having it noticed, either. But most important you cannot do major construction hiring many people and not have it show. Sure, catapults are mostly vacuum; stator rings aren’t even close together at ejection end. But Authority’s 3-g catapult was almost one hundred kilometers long. It was not only an astrogation landmark, on every Luna-jump chart, but was so big it could be photographed or seen by eye from Terra with not-large telescope. It showed up beautifully on a radar screen.
     We were building a shorter catapult, a 10-g job, but even that was thirty kilometers long, too big to hide.

(ed note: the shorter the catapult, the higher the gravities of acceleration required)

     So we hid it by Purloined Letter method.

(ed note: workers know catapult is at the end of the subway line, but have no idea where exactly that is.)

     What we needed was something else. Needed steel at new catapult and plenty—Prof asked, if really necessary to put steel around rock missiles; I had to point out that an induction field won’t grab bare rock. We needed to relocate Mike’s ballistic radars at old site and install doppler radar at new site—both jobs because we could expect attacks from space at old site.

     “A maximum of instructive shrecklichkeit with minimum loss of life. None, if possible”—was how Prof summed up doctrine for Operation Hard Rock and was way Mike and I carried it out. Idea was to hit earthworms so hard would convince them —while hitting so gently as not to hurt. Sounds impossible, but wait.
     Would necessarily be a delay while rocks fell from Luna to Terra; could be as little as around ten hours to as long as we dared to make it. Departure speed from a catapult is highly critical and a variation on order of one percent could double or halve trajectory time, Luna to Terra. This Mike could do with extreme accuracy—was equally at home with a slow ball, many sorts of curves, or burn it right over plate—and I wish he had pitched for Yankees. But no matter how he threw them, final velocity at Terra would be close to Terra’s escape speed, near enough eleven kilometers per second as to make no difference. That terrible speed results from gravity well shaped by Terra’s mass, eighty times that of Luna, and made no real difference whether Mike pushed a missile gently over well curb or flipped it briskly. Was not muscle that counted but great depth of that (gravity) well.
     So Mike could program rock-throwing to suit time needed for propaganda. He and Prof had settled on three days plus not more than one apparent rotation of Terra—24hrs-50min-28.32sec—to allow our first target to reach initial point of program. You see, while Mike was capable of hooking a missile around Terra and hitting a target on its far side, he could be much more accurate if he could see his target, follow it down by radar during last minutes and nudge it a little for pinpoint accuracy.
     We needed this extreme accuracy to achieve maximum frightfulness with minimum-to-zero killing. Call our shots, tell them exactly where they would be hit and at what second—and give them three days to get off that spot.
     North America had struck me as horribly crowded, but her billion people are clumped—is still wasteland, mountain and desert. We laid down a grid on North America to show how precisely we could hit—Mike felt that fifty meters would be a large error. We had examined maps and Mike had checked by radar all even intersections, say 105° W by 50° N—if no town there, might wind up on target grid … especially if a town was close enough to provide spectators to be shocked and frightened.
     We warned that our bombs would be as destructive as H-bombs but emphasized that there would be no radioactive fallout, no killing radiation—just a terrible explosion, shock wave in air, ground wave of concussion. We warned that these might knock down buildings far outside of explosion and then left it to their judgments how far to run. If they clogged their roads, fleeing from panic rather than real danger—well, that was fine, just fine!
     But we emphasized that nobody would get hurt who heeded our warnings, that every target first time around would be uninhabited—we even offered to skip any target if a nation would inform us that our data were out-of-date. (Empty offer; Mike’s radar vision was a cosmic 20/20.)
     But by not saying what would happen second time around, we hinted that our patience could be exhausted.
     In North America, grid was parallels 35, 40, 45, 50 degrees north crossed by meridians 110, 115, 120 west, twelve targets. For each we added a folksy message to natives, such as:
     “Target 115 west by 35 north—impact will be displaced forty-five kilometers northwest to exact top of New York Peak. Citizens of Goffs, Cima, Kelso, and Nipton please note.
     “Target 100 west by 40 north is north 30° west of Norton, Kansas, at twenty kilometers or thirteen English miles. Residents of Norton, Kansas, and of Beaver City and Wilsonville, Nebraska, are cautioned. Stay away from glass windows. It is best to wait indoors at least thirty minutes after impact because of possibility of long, high splashes of rock. Flash should not be looked at with bare eyes. Impact will be exactly 0300 your local zone time Friday 16 October, or 0900 Greenwich time—good luck!

     But our attitude was conciliatory—“Look, people of Terra, we don’t want to kill you. In this necessary retaliation we are making every effort to avoid killing you… but if you can’t or won’t get your governments to leave us in peace, then we shall be forced to kill you. We’re up here, you’re down there; you can’t stop us. So please be sensible!”
     We explained over and over how easy it was for us to hit them, how hard for them to reach us. Nor was this exaggeration. It’s barely possible to launch missiles from Terra to Luna; it’s easier to launch from Earth parking orbit—but very expensive. Their practical way to bomb us was from ships.

     Came Friday with no answer from F.N. News up from Earthside seemed equal parts unwillingness to believe we had destroyed seven ships and two regiments (F.N. had not even confirmed that a battle had taken place) and complete disbelief that we could bomb Terra, or could matter if we did—they still called it “throwing rice.” More time was given to World Series.

     My worries had to do with Mike. Sure, Mike was used to having many loads in trajectory at once—but had never had to astrogate more than one at a time. Now he had hundreds and had promised to deliver twenty-nine of them simultaneously to the exact second at twenty-nine pinpointed targets.
     More than that— For many targets he had backup missiles, to smear that target a second time, a third, or even a sixth, from a few minutes up to three hours after first strike.
     Four great Peace Powers, and some smaller ones, had antimissile defenses; those of North America were supposed to be best. But was subject where even F.N. might not know. All attack weapons were held by Peace Forces but defense weapons were each nation’s own pidgin and could be secret. Guesses ranged from India, believed to have no missile interceptors, to North America, believed to be able to do a good job. She had done fairly well in stopping intercontinental H-missiles in Wet Firecracker War past century.
     Probably most of our rocks to North America would reach target simply because aimed where was nothing to protect. But they couldn’t afford to ignore missile for Long Island Sound, or rock for 87° W x 42° 30’ N—Lake Michigan, center of triangle formed by Chicago, Grand Rapids, Milwaukee. But that heavy gravity makes interception a tough job and very costly; they would try to stop us only where worth it.
     But we couldn’t afford to let them stop us. So some rocks were backed up with more rocks. What H-tipped interceptors would do to them even Mike did not know—not enough data. Mike assumed that interceptors would be triggered by radar —but at what distance? Sure, close enough and a steelcased rock is incandescent gas a microsecond later. But is world of difference between a multi-tonne rock and touchy circuitry of an H-missile; what would “kill” latter would simply shove one of our brutes violently aside, cause to miss.
     We needed to prove to them that we could go on throwing cheap rocks long after they ran out of expensive (milliondollar? hundred-thousand-dollar?) H-tipped interceptor rockets. If not proved first time, then next time Terra turned North America toward us, we would go after targets we had been unable to hit first time—backup rocks for second pass, and for third, were already in space, to be nudged where needed.
     If three bombings on three rotations of Terra did not do it, we might still be throwing rocks in ‘77—till they ran out of interceptors… or till they destroyed us (far more likely).
     For a century North American Space Defense Command had been buried in a mountain south of Colorado Springs, Colorado, a city of no other importance. During Wet Firecracker War the Cheyenne Mountain took a direct hit; space defense command post survived—but not sundry deer, trees, most of city and some of top of mountain. What we were about to do should not kill anybody unless they stayed outside on that mountain despite three days’ steady warnings. But North American Space Defense Command was to receive full Lunar treatment: twelve rock missiles on first pass, then all we could spare on second rotation, and on third—and so on, until we ran out of steel casings, or were put out of action… or North American Directorate hollered quits.
     This was one target where we would not be satisfied to get just one missile to target. We meant to smash that mountain and keep on smashing. To hurt their morale. To let them know we were still around. Disrupt their communications and bash in ommand post if pounding could do it. Or at least give them splitting headaches and no rest. If we could prove to all Terra that we could drive home a sustained attack on strongest Gibraltar of their space defense, it would save having to prove it by smashing Manhattan or San Francisco.
     Which we would not do even if losing. Why? Hard sense. If we used our last strength to destroy a major city, they would not punish us; they would destroy us. As Prof put it, “If possible, leave room for your enemy to become your friend.”
     But any military target is fair game.

     Got into shade of shed and peeked around edge at Terra.
     She was hanging as usual halfway up western sky, in crescent big and gaudy, three-plus days past new. Sun had dropped toward western horizon but its glare kept me from seeing Terra clearly. Chin visor wasn’t enough so moved back behind shed and away from it till could see Terra over shed while still shielded from Sun—was better. Sunrise chopped through bulge of Africa so dazzle point was on land, not too bad—but south pole cap was so blinding white could not see North America too well, lighted only by moonlight.
     Twisted neck and got helmet binoculars on it—good ones, Zeiss 7 x 50s that had once belonged to Warden.
     North America spread like a ghostly map before me. Was unusually free of cloud; could see cities, glowing spots with no edges. 0837—
     At 0850 Mike gave me a voice countdown—didn’t need his attention; he could have programmed it full automatic any time earlier.
     0851—0852—0853… . one minute—59—58—57 … . half minute—29–28—27 … . ten seconds—nine—eight— seven— six—five—four—three—two—one—
     And suddenly that grid burst out in diamond pinpoints!

     Prof looked puzzled. “I am confused by that, too. This dispatch so alleged. But the thing that puzzled me is that we could actually see, by video, what certainly seemed to be atomic explosions.”
     “Oh.” I turned to Wright. “Did your brainy friends tell you what happens when you release a few billion calories in a split second all at one spot? What temperature? How much radiance?”
     “Then you admit that you did use atomic weapons!”
     “Oh, Bog!” Head was aching. “Said nothing of sort. Hit anything hard enough, strike sparks. Elementary physics, known to everybody but intelligentsia. We just struck damnedest big sparks ever made by human agency, is all. Big flash. Heat, light, ultraviolet. Might even produce X-rays, couldn’t say. Gamma radiation I strongly doubt. Alpha and beta, impossible. Was sudden release of mechanical energy. But nuclear? Nonsense!”

From THE MOON IS A HARSH MISTRESS by Robert Heinlein (1965)

Destructive Potential of Lunar Rocks

If the catapults were able to fire stuff at velocities comparable to Earth's escape velocity, the lag time issues would favour Terrestrial catapults (mounted on moving vehicles, these might be called 'MBT cannons'). This means the energy content of the incoming rocks is something like 6x10^7 J/kg. For comparison, fission peace enhancement devices are good for about 9x10^12 J/kg, ims, and fusion PED for 8x10^14 J/kg. It still compares well to TNT's 4.6x10^6 J/kg but note we are not talking the five to seven orders of magnitude between atomic and chemical but one order of magnitude.

If some arcane method could be found to focus the energy in a chemical explosive into a smaller massed projectile, it seems possible terrestrial chemically driven projectiles could compete with Lunar> ones in terms of EK/kg or alternatively one might use 15x as many shots.


Crater diameter scales roughly according to the cube root of the delta energy. Barringer is ~1 km across and was formed by a 15 MT (~6x10^16J) event. Diamter/depth ~6 is not a bad general rule.

Say our lunar impactor is a 2 kt event. The crater would be 1 km x [8.4x10^12 J/6x10^16 J]^1/3 or ~50 m diamter x 8 m deep.

Cheyenne is destroyed in TMISHM by the impact of many rocks from the Moon. Call it a cone of r = 1000 m and h = 1000 m, for a Volume of about 10^9 m^3. Given the crater volumes (rouhly) 5300 m^3 it would take very roughly 200,000 shots or at least 67+ days if they can fire one shot every 30 seconds or so.

Note: a 2 kt device in this case is also a 140 tonne ingot, because you are getting atomic weapon yields out of something with an energy density only an order of magnitude better than chemical. An iron package would be about 18 m^3 (a 3.2 m diameter sphere). An osmium one would be but 6.2 m^3 (a 2.3 m diameter sphere).

NASA tracks orbital debris as small as 10 cm, and current radar technology (which is to say, of an era earlier than the Lunar Catapult) can track items as small as 3 mm, albeit below 600 km altitude at present.

Incoming ingots are therefore likely to be noticed fairly early.

Wave formation:

Stolen without attribution from _Hazards Due to Comets & Asteroids_

Wave height, impact in shallow water:

h = 1450 m [d/r] [y/gigatons]^1/4

h = wave height
d = water depth
r = range to impact
y = yield

ditto, impact in deep water:

h = 6.5 m [y/gigaton]^0.54 [1000km/r]

Wave run in:

Xmax ~ 1.0 km [h/10 meters]^4/3

And this really is a very rough general rule. Consider what happens to a 10 meter wave hitting the cliffs of Dover vs Bangladesh (with 17 million people roughly 1 meter above high tide, IIRC).

RAH is unfortunately specific about the UK offshore impacts, which is what led to the conclusion that the wave height at Margate was 7 cm. Even more unfortunately, _The Effects of Nuclear Weapons_ would led one estimate this and it was available when TMIAHM was written.

Small ingots make tiny waves. Large ingots are, well, large and attract early detection and countermeasures.


One of the attractive things about Lunar catapults is that they led you leverage your input: most of the Ek comes from falling 380,000 km rather than directly from the capapult [After all, if the catapult could fire things at 11/km, you could just put it on the Earth and lob objects at semiorbital velocities around the planet]. You do have to get the objects off the Moon, though.

Say this is an investment of 2.5 km/s. Each ingot masses 140,000 kg, so the Ek is 4x10^11 Joules. At ten gees, that's 25 seconds, or a power output of 16 gigawatts. This catapult needs Pickering sized nuclear reactor or its equivelent to power it.

This raises more stealth issues. If 90% of the power goes into Ek and 10% into heat, this is generating about 1.8 GW of heat for half a minute. This is a serious problem because the heat flare lets the targets know a shot has been fired. It also lets them know where the radiators are, inviting attacks on them.

This is another reason why stealthy attacks are hard with the catapult. The reason I mention stealth is because of

Time to Target:

A low energy orbit to Earth takes 3 - 5 days (Or even longer, for other solutions). A Lunar Bombard begins by announcing each launch with a flare of heat, then a large trackable object slowly orbits to Earth, where it experiences a lithobraking phase at least 72 hours later.

By comparison, a 1 km/s projectile fired from 100 km away arrives in about 2 minutes (Hastily checks to make sure 100 km is within the range of a 1 km/s ballistic object).

A Standard Wheelchair Bound Grandmother [SWBG] is assumed to be able to procede over paved road at 2 km/hr and 100 m/hr on broken ground. In 72 hours, assuming 8 hours of rest in every 24, a SWBG can procede 96 km on paved road and 4.8 km in rough terrain. A SWBG could therefore evade most of the effects of a 2 kt groundburst.

By comparison, a SWBG could only move 70 meters on paved ground (the best case scenario), if the 2 kt event package was sent at 1 km/s from a source 100 km away. 70 m is within the fireball of a 2 kt event. Most SWBGs will not survive being in a fireball.

Lunar bombards are therefore only good against static targets. And we already have weapons just as effective on static targets that don't take half a week to arrive. Therefore Lunar bombards are not competitive for targets on Earth with weapons we already have.

Burnt Off

If the interstellar conflict in question is all about extermination, with none of that realpolitik nonsense, there is no point in a limited orbital bombardment. Assuming you do not want the planet as a possible colony site, then you might as well nuke the place until it is a black glassy sphere that will glow radioactive blue for the next million years or so. The result will be a cemetery planet object lesson for future alien civilizations to come that the inhabitants really pissed you off (or were some hideous species that was far too dangerous to live).

Have your interstellar bomber dump a hellburner, a planet-wrecker nuclear bomb, a planet-sterilizing torch warhead, a planet-cracker antimatter warhead, or a planet-buster neutronium-antimatter warhead. Or take a bit more time to simply carpet-bomb the planet with old-school nuclear warheads.


SLAG. To effectively destroy a PLANET, rendering it totally non-HABITABLE by melting the surface into slag. This need not require a particularly high TECHLEVEL; bumping a handy asteroid into a collision orbit will do it nicely. The ease with which Planets can be Slagged introduces a fundamental problem in WARFARE, equivalent to the nuclear balance of terror that prevailed on Earth during the second half of the 20th century CE.

     If Warfare is to be an effective means of settling political differences, some way has to be found to keep everyone from just Slagging each other, and most of the KNOWN GALAXY, into oblivion. Judging from historical experience, the natural solution is to refrain from large-scale regular Warfare, resorting instead to terrorism or fomenting guerilla wars on third-galaxy Planets. Neither of these solutions seems to be widespread, though. They lack the glamour of real stand-up Warfare, and at least for Americans the idea of guerilla wars still evokes the dismal Spectre of Vietnam.

     Universal peace is no solution — that would be as boring as vegetarianism, and everyone would wander off to read fantasy trilogies or Tom Clancy knockoffs instead. So instead an unwritten agreement seems to prevail, in all eras and throughout the Known Galaxy. Warfare can and will be fought a l'outrance, with frequent stand-up clashes of battlefleets in Space and armored divisions on Planets, but everyone will almost always refrain from Slagging Planets.

     Violators, one must presume, get Slagged.


For myself and my setting, I concluded that at least some aspects of the “kill it with nuclear fire” school are going to be more or less inescapable because of, as you point out, how good the planetary defenders have it.

What the Ley Accordsthe Eldraeverse equivalent of the Geneva Convention, essentially – actually says is that you can’t use planetary bombardment indiscriminately on civilian populations or to make terror strikes, and once you’ve disabled the orbital defenses and “own the high orbitals”, you’re supposed to ask for their surrender before you start firing on the legitimate military targets…

…because once you’ve started dropping heavy enough hellflowers (air-burst antimatter sterilization/EMP weapons), stoneburners (sub-ground-burst anti-bunker burrowing antimatter shaped-charges), and plain old k-rods (Rods From God) to take out deep-running submarines, crust-embedded fortresses, giant planetary lasers, etc., etc., there’s no way not to do major damage to the planet even if you’re not trying to, or indeed if you’re trying not to. If you’re lucky, you’ll get away with a few dozen simultaneous earthquakes/tsunamis/wildfires/hurricanes/massive radiation events/etc. worth of damage. If you’re unlucky, you throw enough debris into the air to give you a particle winter and a major extinction event. And either way, depending on how careful the planetary government is to keep its military facilities in the middle of nowhere, you’ve got megadeaths to gigadeaths.

The polities that are both (a) established galactic citizens, and (b) halfway civilized, all understand this, and that you’re supposed to surrender the planet when you lose the orbital defenses, because while you might not be able to take it back, you definitely can’t un-wreck it.

(Even if you intend to fight a guerilla war groundside afterwards and are willing to absorb the damage from that, you may still find it worthwhile to surrender any formal planetary defenses you invested in. At least that way they’re only going to be dropping tactical k-rods on you…

…but there’s no upside to engaging in a pissing contest with starship-class weapons and their planet-mounted equivalents when the planet is going to take all the collateral damage, and the fleet in orbit doesn’t have to worry about that.)

Thus, Imperial admirals hate having to fight galactic newbies (who might be under the impression that you can fight and win an orbit/ground battle without taking horrific collateral damage), or worse, the kind of fanatics who don’t mind taking their population and ecology along with them when they go. (Although, in practice, there’s usually someone in the latter’s command structure willing to introduce their leader to a bullet rather than let him initiate Ragnarok.) Even Caliéne “the Worldburner” Sargas-ith-Sargas, the IN’s mostly-tame sociopath, thinks it’s a little messy and inelegant.

From SLAG THEM! by Alistair Young (2015)

      "One spot of luck in the whole knock out." That was Rolth, his voice as usual unemotional. "This is an Arth type planet. Since we aren't going to lift off it again in a hurry we'd better thank the Spirit of Space for that!"

     An Arth type planet—one on which the crew of this particular ship could breathe without helmets, walk without discomfort of alien gravity, probably eat and drink natural products without fear of sudden death. Kartr eased his wrist across his knee. That was pure luck. The Starfire might have blown anywhere within the past three months—she had been held together only with wire and hope. But to blow on an Arth type world was better fortune for her survivors than they would have dared pray for after the black disappointments of the past few years, years of too many missions and no refittings.

     "It hasn't been burnt off either," he observed almost absently.

     "Why should it have been?" inquired Fylh, his voice tinged with almost cheerful mockery—but mockery which also had a bite in it.“This system is far off our maps—very far removed from all the benefits of our civilization!”

     The benefits of Central Control civilization, yes. Kartr blinked as that struck home. His own planet, Ylene, had been burned off five years ago—during the Two-Sector Rebellion. And yet he sometimes still dreamed of taking the mail packet back, of wearing his ranger uniform, proud with the Five Sector Bars and the Far Roving Star, of going up into the forest country—to a little village by the north sea. Burned off—! He had never been able to visualize boiled rock where that village had stood—or the dead cinder which was the present Ylene—a horrible monument to planetary war.

From STAR RANGERS by Andre Norton, 1953.
Collected in STAR SOLDIERS (2001), currently a free eBook in the Baen free library.

(ed note: the Grand Alliance of Terrans, Orions, Gorm and Ophiuchi have their backs against the wall. They are sore beset by the Arachnid Omnivoracity. These are aliens who resemble huge spiders, are too alien to communicate with, and who consider all other intelligent races to be food sources. They are fond of eating alive human beings, especially children. As more and more Alliance planets are captured and eaten by the bugs, the Terrans implement General Directive 18. Genocide has been ordered on any planet in the Arachnid Omnivoracity.)

      "It worked, Admiral! We're in, and there's no indication that they've detected our emergence!"

     "Thank you, Commander," Prescott acknowledged quietly. He didn't really want to deflate the spook's enthusiasm, but at times like this the most useful thing an admiral could do was project an air of imperturbable calm and confidence.

     And, after all, it wasn't so surprising that Sixth Fleet had succeeded in entering the Bug system undetected. This was a closed warp point of which the Bugs knew nothing, little more than a light-hour out from the primary. The "vastness of space" was a hideously overused cliche, and like most cliches it tended to be acknowledged and then promptly forgotten.

     Prescott stood up from his command chair and stepped to the system-scale holo display, already alight with downloaded sensor data. As per convention, the system primary was a yellow dot at the center of the plot. Just as conventionally, Prescott's mind superimposed the traditional clock face on the display. Warp points generally, though not always, occurred in the same plane as a system's planetary orbits, which was convenient from any number of standpoints. The closed warp point through which they'd emerged was on a bearing of about five o'clock from the primary. No other warp points were shown—they hadn't exactly been able to do any surveying here—but planets were. The innermost orbited at a six-light-minute radius, but at a current bearing of two o'clock. The second planet's ten-light-minute-radius orbit had brought it to four o'clock. An asteroid belt ringed the primary at fourteen light-minutes, and other planets orbited still further out, but Prescott ignored them. Planets I and II were the ones Sixth Fleet had come to kill.

     A display on this scale wasn't set up to show individual ships or other astronomical minutiae. In a detailed display, those two planets would have glowed white hot from the neutrino emissions of high-energy technology and nestled in cocoons of encircling drive fields. This system was almost certainly one of the nodes of Bug population and industry that Marcus LeBlanc's smartass protégé Sanders had dubbed "home hives." It would have been a primary target even in a normal war—and this war had ceased to be normal when the nature of the enemy had become apparent. The Alliance had reissued General Directive Eighteen, which had lain dormant since the war with the Rigelians. For the second time in history, the Federation and its allies had sentenced an intelligent species to death.

     Sixth Fleet comprised two task forces. Prescott commanded TF 61, which held the bulk of the Fleet's heavy battle-line muscle: forty-two superdreadnoughts, including both Dnepr and Celmithyr'theaarnouw, from which Zhaarnak was flying his lights, accompanied by six battleships, ten fleet carriers, and twenty-four battlecruisers. Force Leader Shaaldaar led TF 62, and the stolidly competent Gorm's command was further divided into two task groups. TG 62.1, under 106th Least Fang of the Khan Meearnow'raaalphaa, had twelve fast superdreadnoughts and three battlecruisers, but those were mainly to escort its formidable array of fighter platforms: twenty-seven attack carriers and twelve fleet carriers. In support was Vice Admiral Janet Parkway, with the forty-eight battlecruisers that made up TG 62.2.

     It was strictly a fighting fleet. There was no fleet train of supply ships, no repair or hospital ships, no assault transports full of Marines. None were needed, for the objective was not conquest and occupation, but pure destruction.

     All expanses of deep space are essentially alike, even when they possess a sun for a reference point. It takes the curved solidity of a nearby planet to create a sensation of place. Depending on the planet, it can also create a psychological atmosphere.

     The planet ahead did that, in spades.

     Prescott told himself that there were perfectly good practical reasons to view that waxing sphere with apprehension. Planet I was the primary population center of this system, and its defenses were commensurate with its importance: twenty-six orbital fortresses, each a quarter again as massive as a monitor and able to fill all the hull capacity a monitor had to devote to its engines with weaponry and defenses. But the space station that was the centerpiece of the orbital installations dwarfed even those fortresses to insignificance. They were like nondescript items of scrap metal left over when that titanic junk sculpture had been welded together.

(ed note: the Bug orbital fortresses are caught by surprise with their defensive force fields down. After a furious battle, all the fortresses are destroyed. But the Bug surface defenses are now fully active)

     But as the last of those gunboats died, Prescott met Zhaarnak's eyes in the com screen, and neither needed to voice what they both knew. Planet I had no defenders left in space.
     "And now," Zhaarnak said quietly, "we will carry out our orders and implement General Directive Eighteen."
     The Bugs, it seemed, didn't favor massively hardened one-to-a-continent dirtside installations like the TFN's Planetary Defense Centers. Instead, the planet's whole land surface was dotted with open-air point defense installations. But even though they might be unarmored, there were scores of them, and each of them was capable of putting up a massive umbrella of defensive fire against incoming missiles or fighters.
     And they'd gotten that point defense on-line. That became clear when the first missile salvos went in.
     Zhaarnak and Prescott looked at the readouts showing the tiny percentage of the initial salvo which had gotten through. Then they looked at each other in their respective com screens.
     "The task force doesn't have enough expendable munitions to wear down anti-missile defenses of that density," Prescott said flatly.
     "No," Zhaarnak agreed. "We would run out of missiles before making any impression. But … our fighter strength is almost intact."
     At first, Prescott said nothing. He hated the thought of sending fighter pilots against that kind of point-defense fire. And, given the fact that TF 61's fighter pilots were Orions, it was possible that Zhaarnak hated it even more.
     "I did not want to be the one to broach the suggestion," the human finally said in the Tongue of Tongues.
     "I know. And I know why. But it has to be done." Steel entered Zhaarnak's voice, and it was the Commander of Sixth Fleet who spoke. "Rearm all the fighters with FRAMs—and with ECM pods, to maximize their survivability. And launch all of them. This is not the time to hold back reserves."

     "Aye, aye, Sir," Prescott responded formally, and nodded to Commander Bichet. The ops officer had recognized what would be needed sooner than his admiral had made himself accept the necessity, and he'd worked up the required orders on his own initiative. Now they were transmitted, and more than four hundred fighters shot away toward the doomed planet's nightside.

     It helped that the Bugs initially made the miscalculation of reserving their point defense fire for missiles. Perhaps they expected the fighters to be armed with standard, longer-ranged fighter missiles. Or perhaps they even believed that the fighter pilots were acting as decoys, trailing their coats to deceive the defenders into configuring their point defense to engage them instead of the battle-line's shipboard missiles in hopes of helping those missiles to sneak through. But then the defenders realized they were up against FRAMs, against which no tracking system could produce a targeting solution during their brief flight, and they began concentrating on the fighters that were launching those FRAMs.

     A wave of flame washed through the Orion formation, pounding down upon it in a fiery surf of point defense lasers and AFHAWK missiles. It glared like a solar corona, high above the night-struck planetary surface, and forty-one fighters died in the first pass.

     But despite that ten percent loss ratio, the remaining fighters put over two thousand antimatter warheads into the quadrant of Planet I which was their target on that pass.

     The darkened surface erupted in a myriad pinpricks of dazzling brightness. From those that were ocean strikes, complex overlapping patterns of tsunami began to radiate, blasting across the planetary oceans at hundreds of kilometers per hour like the outriders of Armageddon. More explosions flashed and glared, leaping up in waves and clusters of brilliant devastation, and as he watched, a quotation rose to the surface of Raymond Prescott's mind. Not in its original form—classical Indian literature wasn't exactly his subject. No, he recalled it at second hand. Four centuries earlier, one of the fathers of the first primitive fission bomb, on seeing his brain child awake to apocalyptic life in the deserts of southwestern North America, had whispered it aghast.

     And now Raymond Prescott whispered it, as well.
     "I am become Death, the destroyer of worlds."
     Amos Chung was close enough to hear.
     "Uh … Sir?"
     "Oh, nothing, Amos," Prescott said, without looking up from the display on which he was watching a quarter of a planet die. "Just a literary quote—a reference to Shiva, the Hindu god of death."

     Zhaarnak and Prescott didn't know that at first, of course, given the communications lag. What they did know, as they drew away from Planet I an hour and ten minutes after launching their first missile at it, was that they had killed at least ninety-five percent of its population outright, and that the few survivors were too irradiated to live long enough to experience nuclear winter on that dust-darkened surface.

From THE SHIVA OPTION by David Weber and Steve White (202)

     Shus and his staff watched the screens and instruments, but nothing happened. Finally the moment came and the tension ebbed away. The fleets were in position—it was time to begin the last battle of the Terra-Sparta War.
     "So be it," said Shus, staring at the screens devoid of the enemy. He no longer felt any sympathy for these people; they had had their chance to come out and die fighting. Now they would be slaughtered like cowering animals. "Commence bombardment!"
     The order flashed nearly instantaneously through the fleets in close orbits around the planet. Knobs were spun and buttons pushed. Smoothly, on near-frictionless hinges, the bomb-bay doors of the battle wagons opened out like the petals of a flower seeking the sun—or in this case, the planet Earth. Then, as naturally as plants releasing millions of spores, the cargoes of bombs were carried away as if by an unseen wind.
     The number of bombs grew, increased incredibly. It seemed that they would never cease spewing forth from the bomb-bays. Swarm upon swarm fell toward Earth in the grip of gravity.

Shus shook his head as he watched the bombs fall away from his ships. He had conducted many a siege against hostile planets, but he had never undertaken anything like this before. Short of using outlawed megatons, this was the ultimate. It was against the rules of space warfare to reduce a planet to ashes with one bomb. He was circumventing those rules by using a million bombs. Never before had it been tried, and he guessed it would never be again, for there was no other race quite like Man. Never had a race been so dreaded.
     The bombs touched the Earth's atmosphere like drops of rain on a roof. The whole sky was darkened with their sinister forms. And even as those in the vanguard struck the atmosphere, still more issued forth from the bellies of the battleships.
     The bombs hurtled down like a thundering deluge, their heat shields glowing red from the friction of the air. Here and there flaws in the heatshields of the hastily mass-produced weapons caused them to burn up. These appeared as colorfully spectacular shooting stars to awed viewers on the Earth.
     The defenders had long ago picked up the falling bombs. Instruments and computers had tracked them diligently. Suddenly the Earth erupted with scintillating light. It was the flickering of the energy beams of Earth filling the heavens.
     Shus smiled grimly. They were trying to shield the planet. The attempt was doomed to failure. There were too many bombs. The Terran defensive fire was unbelievable, incredible. An ordinary bombardment would have been nearly neutralized. Dane Barclay had prepared well, but not even he could defend against a bombardment on this scale.
     Thousands of bombs were hit and exploded high in the atmosphere, turning night into day and day into eye-searing brightness. But for every bomb hit, ten others fell unmolested. And still more were coming from the bomb-bays of the ships above. The laser batteries stabbed desperately and with clever efficiency, but they could not stop all the bombs or even a tenth of them.
     The bombs struck.
     They smashed down everywhere, wiping out laser batteries and cities, homes and roads. Mushrooms sprouted on the Earth as if the planet were one huge mushroom farm. The atmosphere and the surface of the planet became a virtual hell. All the things Man had worked for and built were vaporized, smashed flat, obliterated within seconds.
     The tall buildings were flattened, shattered or blown apart. Like falling dominoes they toppled to lie in ruin. Flames leapt up and the once proud structures, despite their supposed fireproofness, burned like logs casually thrown upon a fire.
     Blinding flashes, coming almost continuously, seared earth and rock. Metals melted and stone bubbled. Lava flowed where no volcanos existed. Land quaked and trembled. Forests burned everywhere, huge seas of flame. Small lakes and rivers dried up instantly, leaving only barren beds to mark their former presence.
     Mountains gained dazzling halos as the bombs sought to reduce them.
     Even underground, no one was safe, for the bombs fell and blasted their way through with terrible violence. Hastily constructed bunkers caved in, burying the occupants dead and alive.
     The bombs spared nothing. They fell everywhere.
     The seas boiled. Fish died by the billions. Mighty tidal waves raced across the land, battling each other and attempting blindly to batter whatever got in the way. Shus had been right; never in galactic history, since the rules of civilized warfare had been set down, had such destruction been visited upon a planet. One bomb was against the rules—a million were not.
     Doomsday was upon the Earth.

     As the scout ships moved through the death-shroud atmosphere of Earth, their instruments and equipment sent data and pictures back to the command ship. In the control room Shus and his staff studied the data and viewscreens intently.
     There was no doubt that Earth had been ravaged as no other planet in the annals of space war. The cities were gone. They had been leveled, pulverized, vaporized. In some places mounds of rubble were visible. In others, where the bomb concentration had been greater, only deep craters remained. The entire planet bore the pock marks of the bombardment. The atmosphere was a nightmare of storm and hurricane, of thunder and lightning, of typhoons and tornados, of monsoons and gigantic fires that turned rain to steam. Upon the heels of the cataclysmic bombs had come condensation of moisture and the creation of huge rainfalls. Drops of rain large as fists drenched the land. The tormented atmosphere reacted by sending killer winds hundreds of miles per hour over the leveled land, uprooting, sweeping all with it.
     While the wind blew and the rain pelted heavily, the world burned. Forests, buildings, parks, vehicles, all burned. Anything that could burn, did. Smoke filled the air. Never had there been anything like it before. Even where the noon-day sun shone fiercely upon the Earth, all was in darkest gloom.
     Shus watched the angered sea batter and beat the land, watched it send towering waves to submerge the land. Tens of thousands of miles of seacoast were overrun and claimed by the water.
     The huge planetary lasers that might have cost him dearly in ships and Spartans were gone—blasted out of existence by the saturation bombardment. Of the battle fleets of Terra there was no sign.
     As he looked at the overwhelming devastation visited upon the planet below, he wanted to believe that those fleets had perished in the bombardment, that the planet was defenseless, that the battle had already been won, but he could not. He knew otherwise. Bitter experience told him that beneath that ravaged outer crust there were fleets, laser batteries, soldiers and cities. But the bombardment, beyond anything they could possibly have expected, must surely have dealt their remaining forces and plan of defense a staggering—if not fatal—blow.
     "There is little point in continuing the bombardment," he said to his officers. It would be a case of diminishing returns, and the remaining bombs would best be of service against specific targets as they were uncovered.
     "Phase One, I would say, is an overwhelming success. We have destroyed the static defenses, leveled the cities and no doubt killed most of the population.
     "We will move to Phase Two now: the removal of surviving defensive forces. Let's go down and get this over with."
     The Spartan fleets descended into the dark gloom, seeking the surviving forces of once proud Earth.

From SIEGE OF EARTH by John Faucett (1971)

All the energy put into achieving that velocity had transformed the Intruder into a kinetic storage device of nightmarish design. If it struck a world, every gram of the vessel's substance would be received by that world as the target in a linear accelerator receives a spray of relativistic buckshot. Someone, somewhere, had built and was putting to use a relativistic bomb — a giant, roving atom smasher aimed at worlds...

The gamma-ray shine of the decelerating half was also detectable, but it made no difference. One of the iron rules of relativistic bombardment was that if you could see something approaching at 92 percent of light speed, it was never where you saw it when you saw it, but was practically upon you...

In the forests below, lakes caught the first rays of the rising Sun and threw them back into space. Abandoning the two-dimensional sprawl of twentieth-century cities, Sri Lanka Tower, and others like it, had been erected in the world's rain forests and farmlands, leaving the countryside virtually uninhabited. Even in Africa, where more than a hundred city arcologies had risen, nature was beginning to renew itself. It was a good day to be alive, she told herself, taking in the peace of the garden. Then, looking east, she saw it coming — at least her eyes began to register it — but her optic nerves did not last long enough to transmit what the eyes had seen.

It was quite small for what it could do — small enough to fit into an average-sized living room — but it was moving at 92 percent of light speed when it touched Earth's atmosphere. A spear point of light appeared, so intense that the air below snapped away from it, creating a low-density tunnel through which the object descended. The walls of the tunnel were a plasma boundary layer, six and a half kilometers wide and more than 160 deep — the flaming spear that Virginia's eyes began to register — with every square foot of its surface radiating a trillion watts, and still its destructive potential was but fractionally spent.

Thirty-three kilometers above the Indian Ocean, the point began to encounter too much air. It tunneled down only eight kilometers more, then stalled and detonated, less than two-thousandths of a second after crossing the orbits of Earth's nearest artificial satellites.

Virginia was more than three hundred kilometers away when the light burst toward her. Every nerve ending in her body began to record a strange, prickling sensation — the sheer pressure of photons trying to push her backward. No shadows were cast anywhere in the tower, so bright was the glare. It pierced walls, ceramic beams, notepads, and people — four hundred thousand people. The maglev terminal connecting Sri Lanka Tower to London and Sydney, the waste treatment centers that sustained the lakes and farms, all the shops, theaters, and apartments liquefied instantly. The structure began to slip and crash like a giant waterfall, but gravity could not yank it down fast enough. The Tower became vapor before it could fall half a meter. At the vanished city's feet, the trees of the forest were no longer able to cast shadows; they had themselves become long shadows of carbonized dust on the ground.

In Kandy and Columbo, where sidewalks steamed, the relativistic onslaught was unfinished. The electromagnetic pulse alone killed every living thing as far away as Bombay and the Maldives. All of India south of the Godavari River became an instant microwave oven. Nearer the epicenter, Demon Rock glowed with a fierce red heat, then fractured down its center, as if to herald the second coming of the tyrant it memorialized. The air blast followed, surging out of the Indian Ocean -- faster than sound — flattening whatever still stood. As it slashed north through Jaffna and Madurai, the wave front was met and overpowered by shocks rushing out from strikes in central and southern India.

Across the face of the planet, without warning, thousands of flaming swords pierced the sky...

Then out of no where — out of the deep impersonal nowhere — came a bombardment that even the science fiction writers had failed to entertain.

Just nine days short of America's tricentennial celebrations, every inhabited planetary surface in the solar system had been wiped clean by relativistic bombs. Research centers on Mars, Europa, and Ganymede were silent; even tiny Phobos and Moo-kau were silent. Port Chaffee was silent. New York, Colombo, Wellington, the Mercury Power Project and the Asimov Array. Silent. Silent. Silent.

A Valkyrie rocket's transmission of Mercury's surface had revealed thousands of saucer-shaped depressions where only hours before had existed a planet-spanning carpet of solar panels. The transmission had lasted only a few seconds — just long enough for Isak to realize there would be no more of the self-replicating robots that had built the array of panels and accelerators, just long enough for him to understand that humanity no longer possessed a fuel source for its antimatter rockets — and then the transmission had ceased abruptly as the Valkyrie disappeared in a silent white glare.

Presently, most of the station's scopes and spectrographs were turning Earthward, and Isak found it impossible to believe what they revealed. The Moon rising over Africa from behind Earth was peppered with new fields of craters. The planet below looked like a ball of cotton stained grayish yellow. The top five meters of ocean had boiled off under the assault, and sea level air was three times denser than the day before — and twice as hot...

The sobering truth is that relativistic civilizations are a potential nightmare to anyone living within range of them. The problem is that objects traveling at an appreciable fraction of light speed are never where you see them when you see them (i.e., light-speed lag). Relativistic rockets, if their owners turn out to be less than benevolent, are both totally unstoppable and totally destructive. A starship weighing in at 1,500 tons (approximately the weight of a fully fueled space shuttle sitting on the launchpad) impacting an earthlike planet at "only" 30 percent of lightspeed will release 1.5 million megatons of energy -- an explosive force equivalent to 150 times today's global nuclear arsenal... (ed note: this means the freaking thing has about nine hundred mega-Ricks of damage!)

The most humbling feature of the relativistic bomb is that even if you happen to see it coming, its exact motion and position can never be determined; and given a technology even a hundred orders of magnitude above our own, you cannot hope to intercept one of these weapons. It often happens, in these discussions, that an expression from the old west arises: "God made some men bigger and stronger than others, but Mr. Colt made all men equal." Variations on Mr. Colt's weapon are still popular today, even in a society that possesses hydrogen bombs. Similarly, no matter how advanced civilizations grow, the relativistic bomb is not likely to go away...

From THE KILLING STAR by Charles Pelligrino and George Zebrowski

Planetary Nut-Cracker

If the enemy planet has gotta go, but the rest of the enemy solar system might be of some use, and you the capability of moving planets, it may be time for a Nut-Cracker.

You take a sizeable planet which you can spare, somehow transport it into the enemy's solar system, then fly the planet on a collision course with the enemy world. If you really want to splatter the enemy homeworld, you fly in two planets on diametrically opposed courses with the enemy in the middle. Sort of like a hammer and anvil. A cosmic-scale sledge-o-matic.

This is a strictly handwavium space-opera style weapon. Very cinematic but nohow nowhere scientifically possible.


      "Let us all sit down and be comfortable," he continued, changing into the Kondalian tongue without a break, "and I will explain why we have come. We are in most desperate need of two things which you alone can supply—salt, and that strange metal, 'X'. Salt I know you have in great abundance, but I know that you have very little of the metal. You have only the one compass upon that planet?"
     "That's all—one is all we set on it. However, we've got close to half a ton of the metal on hand—you can have all you want."
     "Even if I took it all, which I would not like to do, that would be less than half enough. We must have at least one of your tons, and two tons would be better."
     "Two tons! Holy cat! Are you going to plate a fleet of battle cruisers?"
     "More than that. We must plate an area of copper of some ten thousand square miles—in fact, the very life of our entire race depends upon it."

     "It's this way," he continued, as the four earth-beings stared at him in wonder. "Shortly after you left Osnome we were invaded by the inhabitants of the third planet of our fourteenth sun. Luckily for us they landed upon Mardonale, and in less than two days there was not a single Osnomian left alive upon that half of the planet. They wiped out our grand fleet in one brief engagement, and it was only the Kondal and a few more like her that enabled us to keep them from crossing the ocean. Even with our full force of these vessels, we cannot defeat them. Our regular Kondalian weapons were useless. We shot explosive copper charges against them of such size as to cause earthquakes all over Osnome, without seriously crippling their defenses. Their offensive weapons are almost irresistible—they have generators that burn arenak as though it were so much paper, and a series of deadly frequencies against which only a copper-driven ray screen is effective, and even that does not stand up long."
     "How come you lasted till now, then?" asked Seaton.
     "They have nothing like the Skylark, and no knowledge of intra-atomic energy. Therefore their space-ships are of the rocket type, and for that reason they can cross only at the exact time of conjunction, or whatever you call it—no, not conjunction, exactly, either, since the two planets do not revolve around the same sun: but when they are closest together. Our solar system is so complex, you know, that unless the trips are timed exactly, to the hour, the vessels will not be able to land upon Osnome, but will be drawn aside and be lost, if not actually drawn into the vast central sun. Although it may not have occurred to you, a little reflection will show that the inhabitants of all the central planets, such as Osnome, must perforce be absolutely ignorant of astronomy, and of all the wonders of outer space. Before your coming we knew nothing beyond our own solar system, and very little of that. We knew of the existence of only such of the closest planets as were brilliant enough to be seen in our continuous sunlight, and they were few. Immediately after your coming I gave your knowledge of astronomy to a group of our foremost physicists and mathematicians, and they have been working ceaselessly from space-ships—close enough so that observations could be recalculated to Osnome, and yet far enough away to afford perfect 'seeing,' as you call it."

     "But I don't know any more about astronomy than a pig does about Sunday," protested Seaton.
     "Your knowledge of details is, of course, incomplete," conceded Dunark, "but the detailed knowledge of the best of your Earthly astronomers would not help us a great deal, since we are so far removed from you in space. You, however, have a very clear and solid knowledge of the fundamentals of the science, and that is what we need, above all things."
     "Well, maybe you're right, at that. I do know the general theory of the motions, and I studied some Celestial Mechanics. I'm awfully weak on advanced theory, though, as you'll find out when you get that far."
     "Perhaps—but since our enemies have no knowledge of astronomy whatever, it is not surprising that their rocket-ships can be launched only at one particularly favorable time; for there are many planets and satellites, of which they can know nothing, to throw their vessels off the course.

     "Some material essential to the operation of their war machinery apparently must come from their own planet, for they have ceased attacking, have dug in, and are simply holding their ground. It may be that they had not anticipated as much resistance as we could offer with space-ships and intra-atomic energy. At any rate, they have apparently saved enough of that material to enable them to hold out until the next conjunction—I cannot think of a better word for it—shall occur. Our forces are attacking constantly, with all the armament at our command, but it is certain that if the next conjunction is allowed to occur, it means the end of the entire Kondalian nation."'
     "What d'you mean 'if the next conjunction is allowed to occur?'" interjected Seaton. "Nobody can stop it."
     "I am stopping it," Dunark stated quietly, grim purpose in every lineament. "That conjunction shall never occur. That is why I must have the vast quantities of salt and 'X'. We are building abutments of arenak upon the first satellite of our seventh planet, and upon our sixth planet itself. We shall cover them with plated active copper, and install chronometers to throw the switches at precisely the right moment. We have calculated the exact times, places, and magnitudes of the forces to be used. We shall throw the sixth planet some distance out of its orbit, and force the first satellite of the seventh planet clear out of that planet's influence. The two bodies whose motions we have thus changed will collide in such a way that the resultant body will meet the planet of our enemies in head-on collision, long before the next conjunction. The two bodies will be of almost equal masses, and will have opposite and approximately equal velocities; hence the resultant fused or gaseous mass will be practically without velocity and will fall directly into the fourteenth sun."

     "Wouldn't it be easier to destroy it with an explosive copper bomb?"
     "Easier, yes, but much more dangerous to the rest of our solar system. We cannot calculate exactly the effect of the collisions we are planning—but it is almost certain that an explosion of sufficient violence to destroy all life upon the planet would disturb its motion sufficiently to endanger the entire system. The way we have in mind will simply allow the planet and one satellite to drop out quietly—the other planets of the same sun will soon adjust themselves to the new conditions, and the system at large will be practically unaffected—at least, so we believe."

     Seaton's eyes narrowed as his thoughts turned to the quantities of copper and "X" required and to the engineering features of the project; Crane's first thought was of the mathematics involved in a computation of that magnitude and character; Dorothy's quick reaction was one of pure horror.
     "He can't, Dick! He mustn't! It would be too ghastly! It's outrageous—it's unthinkable—it's—it's—it's simply too horrible!" Her violet eyes flamed, and Margaret joined in:
     "That would be awful, Martin. Think of the destruction of a whole planet—of an entire world—with all its inhabitants! It makes me shudder, even to think of it."
     Dunark leaped to his feet, ablaze. But before he could say a word, Seaton silenced him.
     "Shut up, Dunark! Pipe down! Don't say anything you'll be sorry for—let me tell 'em! Close your mouth, I tell you!" as Dunark still tried to get a word in, "I tell you I'll tell 'em, and when I tell 'em they stay told! Now listen, you two girls—you're going off half-cocked and you're both full of little red ants. What do you think Dunark is up against? Sherman chirped it when he described war—and this is a real he-war; a brand totally unknown on our Earth. It isn't a question of whether or not to destroy a population—the only question is which population is to be destroyed. One of them's got to go. Remember those folks go into a war thoroughly, and there isn't a thought, even remotely resembling our conception of mercy in any of their minds on either side. If Dunark's plans go through the enemy nation will be wiped out. That is horrible, of course. But on the other hand, if we block him off from salt and 'X,' the entire Kondalian nation will be destroyed just as thoroughly and efficiently, and even more horribly—not one man, woman, or child would be spared. Which nation do you want saved? Play that over a couple of times on your adding machine, Dot, and let me know what you get."
     Dorothy, taken aback, opened and closed her mouth twice before she found her voice.
     "But, Dick, they couldn't possibly. Would they kill them all, Dick? Surely they wouldn't—they couldn't."
     "Surely they would—and could. They do—it's good technique in those parts of the Galaxy. Dunark has just told us of how they killed every member of the entire race of Mardonalians, in forty hours. Kondal would go the same way. Don't kid yourself, Dimples—don't be a child. War up there is no species of pink tea, believe me—half of my brain has been through thirty years of Osnomian warfare, and I know precisely what I'm talking about. Let's take a vote. Personally, I'm in favor of Osnome. Mart?"

From SKYLARK THREE by E. E. "Doc" Smith (1930)

(ed note: in the far future of space opera, all nine worlds of the solar system have been colonized. But one fine day the sun starts to cool off. To avoid a frozen death, the planets resolve to place gigantic atom-blasts on each world, fly the planets out of the solar system, and find a warm young star.

They pass several unsuitable stars, but disaster strikes at the star Antolia. The star is going to go nova. And the natives are rather upset at that. The Antolians attempt to capture the passing Solar planets but are beaten off. However, the copy-cat Antolians put atom-blasts on their planets and set off in hot pursuit. The Solar planets finally find a new home star, but the Antolian planets are coming to invade. What to do?)

      WE STARED, our triumph frozen. In the telescopes the four Antolian planets were plainly visible, passing Walaz and moving on with mounting speed toward us.
     "We must do something!” Hurg cried. "If those Antolian worlds reach this sun and take up orbits around it, it means endless war with them, war that may result in our destruction!”
     "We can not stop them from coming on,” Julud said sadly. "I had hoped they would stop their worlds at Walaz, but they are coming on.”
     "If there were only some way to stop them before they get here!” Runnal exclaimed.
     An idea seared across my brain. "There is a way of stopping them!” I cried. "I can stop them with my world, with Mercury!

     "Don’t you understand?” I said. "All of Mercury’s inhabitants can be transferred to other of our worlds and then I’ll take Mercury out and crash it head-on into those four oncoming worlds!”
     "Good, and I’ll go with you, Lonnat!” cried Hurg.
     "And I too!” said Tolarg, eyes gleaming.
     Immediately Julud ordered the transfer of Mercury’s people to other worlds as I requested. All our worlds’ ships swarmed to Mercury and engaged in transporting Mercury’s people to the other planets. It was so tremendous a task that by the time Tolarg and Hurg and I with my assistants in the control-tower were the only people left on Mercury, the four oncoming worlds of the Antolians had almost reached Vira.

     Quickly I opened up Mercury’s propulsion-blasts and sent the little planet hurtling out from Vira, back along the way we had come toward the four nearing worlds. Tensely I and Tolarg and Hurg held it toward them. Outside the control-tower were our waiting ships.
     Toward each other, booming through space with immense speed, thundered Mercury and the four oncoming worlds. The Antolian worlds loomed larger and larger before us. Then they veered to one side.
     "They’re veering! 'They’re trying to escape the collision!” cried Hurg. "It’ll do them no good!” I exclaimed. I swung Mercury aside in the same direction to meet them.
     Again the column of four planets veered as they rushed closer, seeking desperately to escape the oncoming doom. Again I swung Mercury to meet them. Then the foremost of the oncoming Antolian worlds loomed immense in the heavens before our rushing planet.
     "They’re going to crash!" I cried. "Up and away before they meet!”
     "Up and away!” yelled Tolarg and Hurg as we threw ourselves from the control-tower into the ships.
     Our ships darted up like lightning. The rushing globe of Mercury was almost to the oncoming sphere of the first Antolian world. And then as we shot away from them into space, they met!

     There was no sound in the soundless void, but there was a blinding, dazing glare of light that darkened even the great sun behind us for the moment, and then the two worlds became glowing red, molten, blazing with doom! A wave of force struck through space that rocked our fleeing ships.
     And behind the first Antolian world the other three of the column came on and crashed into that glowing mass! One by one they crashed and were destroyed; and then the four worlds were one white hot mass that veered oflF into space at right-angles to Vira and away from it. The four colliding worlds had become a new small sun!
     I stared after that receding, dazzling mass. There were tears in my eyes as I watched it move away, with the remains of Mercury in it. Mercury, my world, that I had piloted across the great void through the suns only to hurl it at the last into doom.
     Hurg was grasping my arm excitedly. "We’ve won, Lonnat!” he cried. "The Antolians and their worlds destroyed, and Vira ours now for our eight remaining worlds!”
     Tolarg held out his hand to me, all mockery gone from his face now. "What you said was right, Lonnat,” he said. "It’s not the size of a planet that measures its importance. Yours has saved us all.”

From THUNDERING WORLDS by Edmond Hamiltion (1934)

      "Be seated, friends," said Andar Minot, rising, the ceremonial greeting over. "We have called on you again. Our plans are more exact, and an exact plan requires an exact answer.
     "First: By careful measurement of effects of known forces, we have been able to determine with accuracy the mass of each of our moons. We now know with exactitude the load that the driving engines must move.
     "Second: astronomers have been observing and calculating, and the plan is made exactly according to their results. The smaller of our missiles, Ma-ran, will be used first. This will be torn from its orbit at a time when it is advantageously situated, and the acceleration of its orbital velocity will tear it loose in the exact direction we wish. It will then be projected—"
     Carefully the plan was discussed, and the movements of each of the moons considered. Ma-ran would be equipped with a huge driving engine that would tear it loose from its orbit, to hurl down on Teff-el and Teff-ran, and the orbital forts. Ma-ran, though far lighter than Ma-kanee, would have a driving engine of equal power, because it would be expected to be mobile and capable of real motion, and be forced to pursue and catch the not entirely helpless orbital forts.
     Ma-kanee, on the other hand, would merely hurl its quintillions of tons of mass on the planet— The plan was made, and the work well under way. That same day Aarn and Spencer went out to Ma-kanee where the work was being done.

     The cavern was being expanded in two dimensions, the floor and the ceiling already determined. Artificial gravity plates had been installed in the place to make work easier, but the gravity had been reduced to only one-half normal for Magyans. The men, trained, soldier-mechanicians every one of them, were working under the commands of their officers, and rapidly setting up new racks of power machinery. Huge converters for the strange momentum oscillators were going in now. Bank after bank of oscillators.
     "We have to drive conductors for miles through the rock in every direction to make certain we'd get perfect distribution of the momentum waves. That's the only reason we can move these moons, of course. If we'd had to depend on the space-drive disks, it would have been impossible. Just torn the thing to pieces."
     Here and there they could see dark tunnels still unfilled, borings where Shal torpedo after Shal torpedo had burrowed its way on and on. The borings were less than six inches in diameter and hollow rods of aluminum had been thrust deep into them, to spread the momentum waves through the planetoid.

     A sudden, dull, humming note sounded twice. Carlisle started, and the other two stiffened. "First warning," said Aarn softly, relaxing. "That's the warning from the astronomers on Ma-kanee. They sent the first warning and they'll begin accelerating now, in about thirty-two and a half minutes. They're starting the oscifiator tubes, warming them up."
     Unconsciously, Aarn looked down. Two enormous glass tanks loomed thirty feet high, two tanks filled with metal plates, and huge heaters, grids and screens—the oscillator control tubes. Beside them loomed two cold tubes with a sprinkling of mercury over them, about ten feet high, and some five in diameter. They were the "chopper" tubes which were designated to chop the current off abruptly at an enormous frequency—
     Again the two dull humming notes. "The choppers!" said Aarn softly. His eyes shifted to the great hulking lumps of the momentum drive itself. "That comes next—run direct current through them for a while to warm them. Then when they break that current the oscillation is started—"
     Three notes. "Let's go below." Aarn led the way down. In the control room there was quiet confusion. Men were rapidly walking back and forth. Seven different radio positions were occupied. Three more television control positions, and, finally, the great panel where the main controls were, with the three television screens and the selector dials which would throw any part of space on the screen, or into any one of the telescopes.

     A low, powerful throbbing hum sounded. As Aarn threw a switch, the television disk before him lighted up suddenly, as the beating note ceased, and the face of the controller on Ma-kanee appeared. His face was drawn and intent as he threw a switch. Suddenly an enormous cat began to whine, its whine mounted, and steadied to a great, gentle purr. Another—another—another—
     "Gyroscopes," said Aarn. "They have to stop the spin of the moon first. They have small momentum controls that are controlled by the big gyroscopes. They'll hold it firm."
     There was a steady, grumbling roar sounding now from the speaker. Ma-kanee was being stopped in her age-long rotation. Only slight disturbance was caused, because every particle was being decelerated, but there was a certain amount of oblateness, and this was flattening out, or rounding out, with groaning protest.
     The controller started, and turned to someone behind and to one side of him. "All proceeding as directed. The main tubes and apparatus are warm now, ready for operation if necessary."
     The man behind him made some inaudible answer, and the controller, Hirun Theralt, checked all the dials before him.

     Quickly the time passed. All the men on Ma-kanee were busy, working frantically as the moment of the start approached. Finally the controller spoke directly into his microphone.
     "To the Council of Astronomy: My rotation shows zero. Is this correct?"
     A voice answered metallically from a concealed speaker. "That is correct. Read off your coordinates, and we will give you the correct axes."
     "X-543-27. Y-732-45. Z-982.38."
     "Set the controllers at: X-234-31, Y-135-52, Z-64-32. Let the master controls rest at this, and watch only your deviation axes readings. Keep these as directed in further messages. Are they now reading zero?"
     "They are zero, and are holding. The automatic antirotation apparatus has been attached, and standardized."
     "Continue as instructed, with acceleration along X at the rate of 752,000 units. At the second signal, increase to 1,435,000 units, and continue except as directed."
     The controller repeated the instructions, his voice trembling a trifle.
     Minutes dragged. Then finally came a soft buzz. Another, another— "At the tenth," said Aarn softly, "he will start—"
     Eight-nine-ten- A groan echoed softly from the loudspeaker, and a great snarling vibration echoed instantly, and died in a shrillness. A blue light glowed down from above, where the great mercury tube boiled in sudden activity.
     "Acceleration at seven-five-two," said the controller.
     "That means," explained Aarn, "seven hundred and fifty thousand millions tons of force. The plan to increase it by steps—"

     On the screen, a sudden blankness came, a shift, then the image of an elderly, gray-haired man. "The view we will send now, is a model map of the actual, and the correct theoretical position of Ma-kanee. This will show the deviation from her normal orbit"
     The screen was black, save for a green circle, Magya, two red and blue dots. The dots were points on great ellipses. Slowly, slowly, they could see the red dot near Magya creeping along. The others seemed almost motionless.
     Hours later, the inner red dot had made a complete circuit, and now there were three red dots, and two blue. Ma-kanee's dot had split in two. One of the Ma-kanee dots was slowly circling on a greater, and ever-growing orbit More and more power was being applied. The slow acceleration was increasing gradually.
     Again Ma-ran swung about in her orbit—and now Makanee was hundreds and thousands of miles from her assigned orbit. She was struggling mightily now, with increasing momentum and centrifugal force to pull herself free of the bonds of Magya. Her orbit was lengthening more and more toward a straight line. She was on the night side of Magya now, soon she would fly off on the day side—and escape toward Anrel. Then the acceleration that was being applied would change in direction, change to bend the normal orbital speed about Anrel toward the sun, instead of at right angles. The centrifugal force no longer acting against it, Anrel's pull might drag the moon even faster toward Teffel.

     The screen was showing many different scenes now. At length it showed a scene that was relayed from a ship far away—a ship hanging off Teff-el! An investigator, one of those that still had not been found, was showing the streets of Cantak.
     Teff-el had seen and understood, when Ma-kanee started her movement. Not fully understood, for they believed it only a great weapon—a great battleship that no battleship could fight. A battleship that would come down and ray them out of existence—destroy every ship, every orbital fort—and finally the forts on Teff-ran. Then Ma-kanee, they feared, would set up in an orbit about Teff-el, and never again would a Tefilan ship be able to reach the surface! Every city isolated—till tunnels could be dug to connect them!
     There was panic, and excitement. Tremendous loads of supplies were being rushed out to Teff-ran, that she might defend the planet, perhaps conquer even the mobile moon!
     Aarn smiled grimly. "Futile," he said. "Nothing could help. They might carry some of their people away—but the Magyan fleet is already waiting just off Teff-el. They can't get away. There are almost no ships near here."
     "What if the Tefilans attack?" asked Carlisle.
     Aarn lighted a cigarette carefully. There were few left now. "If they did, what would they attack? The moon? Much good that would do them. Magya? Where? How? There's nothing on the surface, and they couldn't reach the cities before our fleet could start in on one of their orbital forts, and start cleaning up thoroughly. They'd have to be called home."

     It took days, and long before the process was finished, Tefflan ships of war were circling viciously off Ma-kanee- and occasionally there was a flash of instantaneous blue incandescence as the inconceivable coils of the moon ship were shorted by a mere cruiser.
     But finally Ma-kanee sailed proudly free, and bent her orbit more and more toward Teff-el.
     And then, one day, there was further stirring among Magya's children, and Teff-el was stricken by horrible panic.
     Aarn, his iron nerves alone subduing the trembling that crept into them, pressed a series of controls. And huge oscillator tubes glowed dull-red. The power board sprang into life across the way, and Aarn read its warnings and its story, and returned to his own control board.
     The tremendous transformers hummed suddenly and the great chopper tubes glowed green-blue, great arcs roared as tumbler switches snapped across. Then the shrill snarl of speeding gyroscopes. The enormous power plant that was Ma-ran, was waking to life. Huge cables that spread out like the threads of a three-dimensional spider web began to glow softly as a low power oscillated through them, and gently, but swiftly, the spin of Ma-ran was slowed. There were no observatories outside here. Ma-ran was to be far more active and far more destructive than her larger sister as she ran amuck.
     On Ma-kanee, observatories had been dismounted. There were no more machines, no lenses—only the transpon-projectors that bit into the feeble attacking moths of the cruisers. The apparatus had been carried away, and already, as the great coils were exhausted in accelerating the ship that was a world, they were being recharged again. Then, when these were again discharged, the great supply ships would take them on. Before Ma-kanee finally struck Teff-el, it would be little more than a hollow moon. The machinery would be salvaged. But Ma-ran was to be an active deadly thing all her short life as a ship; there would be no salvaging of machinery here. Every coil was to be emptied not once, not twice, but four times.
     And as the final signal came, Aarn was on his own. He had only a ship. Carefully he had worked out the course he wanted to follow, and now, with his enormous craft, he turned in the tremendous power. A shrill whine built up, the moon trembled and chattered with the fall of rocks outside, loose material suddenly sliding as the planetoid trembled, started—and moved!

     "I THINK OUR course will be X-235-89," Aarn said. His voice was low, and tense. Ma-kanee was thousands of miles behind now—but in the forward televisor disk, Teff-el showed a huge, round disk. And about the little moon, traveling now with a velocity of thousands of miles an hour, but slower now than Ma-kanee, a fleet of great battleships wove a constant pattern. An angry, threatening halo of destruction, strengthened and widened by the heavy cruisers, and light cruisers, and destroyers. Almost the entire navy was here, for Ma-kanee needed no protection now. Ma-kanee was deserted. There was no apparatus, save for two or three televisors, and a small crew of men to observe. Ma-kanee was a hollow hulk, seven hundred miles in diameter, driving down on a doomed world.
     Teff-el was under no delusions now. They knew that Ma-kanee was not intended to capture forts, and their moon— they knew what it meant. And that was the reason for the heavy protection that was offered Ma-ran. The Tefflans knew that Ma-kanee had no driving engine, that they had no possible weapon capable of turning it. Their only hope lay in capturing Ma-ran, and using it to batter Ma-kanee aside.
     The buzz saw of circling, deadly ships was not revolving unhindered. Scout ships of the Tefflan fleet kept darting in, hoping to launch an unsuspected torpedo, or some weapon which might pierce the magnetic and antigravity shields.

     “Orbital fort,” said Spencer, pointing to a sudden, unfocused, black shadow that swam leisurely across the view. “Will they be dangerous?”
     Aarn shrugged his shoulders. “Probably. They may be able to reach us with the new death-ray projectors. We will know sooner or later.”
     “Two hours and thirty-one minutes,” said Spencer.
     The planet was growing rapidly now. Far off to the left loomed Teff-ran, sweeping rapidly nearer. Teff-ran would not cross their path in this first circuit. “I hope they calculated the mass of those orbital forts right,” sighed Aarn. “It will ruin our plans, if they don’t give the right reaction.”
     “We’re supposed to hit three of them in this first swing, five in the next—if the thing works. We’re going above orbital speed. Those collisions, with loss of momentum, or better, increase of mass, are counted on to slow us for an exceedingly elliptical orbit. The five, next time, will round out our orbit again, act as a resisting medium—molecules in a supergas to slow us down."

     "I've been wondering—won't the shock of the tremendous mass of those forts be enough to split this moon wide open, split it, anyway, so that the momentum drive won't operate? Or so the apparatus here is smashed?"
     Aarn shook his head slowly. "They'll mainly bury them selves in this. We have fifty miles of solid rock above us. A fort—even one as huge as they are—will be of no great consequence. Remember, the rate of collision, the additive velocities, will make the relative velocities practically thirty-five miles a second. The result will be volatilization for the first fort, and for some of our rocky layer, the lower rate of collision of the second, will make it slightly less severe. The main thing, though, is that the rock won't transmit the shock at all!"
     "Why not, it certainly isn't dough?"
     "No, but—it can't transmit any shock, any push, at speed greater than the speed of sound through it. That speed of collision is greater than the speed of sound. Ergo, it won't be transmitted as a push. It will simply reduce the rock it hits to powder, expend its energy smashing the rock, breaking it, demolishing it—and not on moving."
     "Also—why don't those orbital forts get out of the way?" asked Spencer
.      "Combination of reasons. They could get part way out of the way at our present speed. That is, they could escape us once, but actually, this moon has greater mobility than they have. They were carried out by supply ships in pieces, and built up. They have motive power enough to turn around, and to straighten out their orbits so they won't tangle, but they can't flee. The main thing is that those Tefflans have courage. They will hope that the greater power of the forts may be able to do something against this moon, in the way of stopping it."

     As the Sunbeam swept up, the view Aarn had was, for the first time, as an outsider. The majesty of the scene came to him suddenly—the great dark sphere, rugged and cold in the sunlight, the dust motes of the Tefflan freighters daring to oppose it, and, further away, the great mass of Teff-ran.
     And now, away from the moon, he saw at last Ma-kanee. Deserted, uncontrolled, and uncontrollable, she was plunging straight for Teff-el. And Teff-el was already drawing her. Seas on Teff-el were rising, tides appearing, for already the swift-moving moon was within 1,000,000 miles of the planet There had been no attempts to divert it. That was frankly impossible. Further attempts to escape from Teff-el had been made, but there was a great ring now, of far-flung spy ships, each with a tremendous magnetic atmosphere thrown out, and the first touch of a ship attempting to escape made itself very evident And the fields overlapped.
     Minutes passed swiftly. And now the mass of Tefflan ships ahead, deserted, had separated to individuals. Minutes more passed, and at last the terrific process that had been going on within Ma-ran became evident A dull glow began to appear in the rocks below. It was growing swiftly— The first great Tefflan freighter plowed into Ma-ran. It was swallowed up like a pebble sinking into water—and with the same splashing of liquid. Almost instantly, a tremendous fountain of white-hot lava snapped out—and impaled a second freighter that was almost in line with the first. Both tumbled to the mad moon. A dozen were falling—a hundred— In seconds Ma-ran was sweeping on though a clear space.
     Every one of the great Tefflan ships had been absorbed. One of them had barely grazed the world, but been caught, and lay a pool of lighter, molten stuff on the rock pool. Great hot bubbles of air were oozing slowly up from the ships.
     "Velocity fell only one point. That was good enough. We reach Teff-ran now in thee quarters of an hour," said Aarn at last.

     The minutes dragged. The two great bodies seemed to move with infinite weary slowness. They seemed to know doom was upon them, and were going to it with the slow steadiness of men who welcomed doom, but accepted it philosophically and without hurry.
     Further and further the Sunbeam and her escort drew away, now. She raced ahead to a position in line with the final meeting, and watched as the two great balls of matter moved leisurely toward each other.
     Ma-ran looked like an orange drifting gently toward a grapefruit. Ma-ran was at last the smaller as she approached the end of her mad career. And beyond the great crescent of Teff-el, and the approaching disk of Ma-kanee, Tefflan ships swarmed up from Teff-ran—-and a swarm of heavy Magyan cruisers fell on them instantly, and cut them to pieces.
     Ma-ran bulged slowly, seemed to lengthen, and hastened her wild pace as she neared Teff-ran. Glowing red with the liberated energy of her coils, she stretched, became a blunt ended cylinder—and slowly became two great balls of red-hot matter as she began to turn visibly.
     "Gyroscopes went—the impact of the ships—" muttered
     Aarn uneasily. "That may have some unlooked-for effect—" Soundlessly, softly, with a sudden increased blaze of light, the two masses met, and spattered. Ma-ran coalesced with Teff-ran, and stopped. Tell-ran split. Slowly, majestically, they saw chasms open and run about the world. The sides fell away, and kept on going. The second half of Maran struck, and spread like a drop of melted lead on a hard surface—and the slipping sides of Teff-ran were snared, and melted in the flaming blue-white heat of the collision. In a quarter of an hour both bodies were one, and the mass was white-hot, flames spurting out angrily.

     Hours passed, as Aarn hung grimly beside the glowing mass. Finally he was satisfied with his observations, and made his calculations. "Six hours. Ma-kanee will get there in about six hours, two minutes and thirty seconds. This will get there at almost the same time. My calculations aren't quite accurate. I can't allow for the displacement of Tell-el for one thing."
     The new mass was dropping. Slowly—steadily. Wildly, small ships were shooting up from Teff-el, vindictively heading toward a cruiser or battleship with all its power, hoping to smash through the great wall even as a pilot died. They flamed briefly in a great transpon beam, and died— unsuccessful.
     Ma-kanee moved steadily downward. Tefflans were out on the surface of the planet, black masses of them, moving and surging, as they watched the two great bodies falling out of the skies on two exactly opposite sides.

     Three hours. Four hours. Five hours. The heat of the new mass, glowing red, had driven the black masses to other parts of the world. Cracks were appearing in Tell-el now. The new mass was only slightly distorted.
     "Tell-el's gravitational field declines slowly in strength— mass is so great—doesn't pull the near side much harder than the far side, so they don't fall apart, as Ma-ran did." But Tell-el began to fall apart. Great cracks appeared, smoke began to curl up, and over the great cavern system of Cantak, the ground sank suddenly, and an abrupt fault line appeared that sectioned the city with the precision of a knife. And slowly Tell-el turned under the baleful glare of the new, red-hot menace.
     Five hours and a half. The red-hot mass was nearing the outer fringes of the atmosphere. It was falling swiftly, now, still circling the planet a bit, so that its contact would not be a center blow, but a gouging scrape. An entire fleet of battleships was pulling at it now with traction beams, but there was practically no effect. The mass was too great, the beams almost totally useless.
     At the end of six hours, Ma-kanee entered the atmosphere. The atmosphere instantly compressed under it, a great bubble of air, and simultaneously, for the thee seconds it took the planet to traverse the atmosphere, everything beneath that place was compressed under a stupendous air pressure. It mounted like a solid wave; the air could not move away in time— Ma-ran-Tell-ran struck the other side. The atmosphere flamed below, and the planet caught fire from the terrible, glowing coal. Almost simultaneously, with a precision that was astounding, two bodies struck Tell-el.

     And the planet burst like a rotten tomato. Spurts of liquid stuff shot suddenly out of mighty chasms. Bursts that were cold, and solidified instantaneously into weird shafts of solid, grainless, incredible rock. Jets of rock, then great sections of rock, then a great jet of flying, gleaming metal, that squirted out like water from a hose, and solidified as the rock had, and in a bar ten miles through and a hundred and fifty long.
     And then only parts, and broken splinters that began to stop flying apart, remained. They were glowing, and some of them struck, and stuck together, and the force of their striking made them glow more, and cemented them. All three bodies were utterly destroyed, but the heat of Ma-ran-Tell-ran remained, and seemed to act as a binding agent.

     "Well—the ancient enemy is gone. Destroyed after some forty thousand years of trying."
     "And Tell-el is destroyed."
     "But while Tefflans can never reform, Teff-el is already reforming. See how the parts are falling together. It will be centuries, milleniums, before it is a planet again. But Tell-el is not destroyed. An incident in its life has taken place." Aarn gazed at the planet's distintegrating parts.

From THE MIGHTIEST MACHINE by John W. Campbell jr. (1934)

(ed note: in the LENSMAN universe, they have gadgets called "Bergenholms." These allow faster-than-light travel by removing a object's inertia. Small units can make a space-suited person inertialess. Medium units are for starships. And arrays of titanic units can make entire planets move faster than light.

All real-world object have a velocity, called a "intrinsic velocity" in the LENSMAN novels. Once the Bergenholm is turned on, the intrinsic velocity temporarily vanishes. The object can be moved FTL or remain motionless. The important point is, when the Bergenholm is turned off, the intrinsic velocity suddenly reappears.

As the scene opens, protagoinist Gray Lensman Kimball Kinnision is walking with Port Admiral Haynes.)

      "QX, Kim?" the Port Admiral asked. He was accompanying the Gray Lensman on a last tour of inspection.
     "Fine, chief. Couldn't be better—thanks a lot."
     "Sure you're non-ferrous yourself?"
     "Absolutely. Not even an iron nail in my shoes."
     "What is it, then? You look worried. Want something expensive?"
     "You hit the thumb, Admiral, right on the nail. But it's not only expensive—we may never have any use for it."
     "Better build it, anyway. Then if you want it you'll have it, and if you don't want it we can always use it for something. What is it?"
     "A nut-cracker. There are a lot of cold planets around, aren't there, that aren't good for anything?"
     "Thousands of them—millions."
     "The Medonians put Bergenholms on their planet and flew it from Lundmark's Nebula to here in a few weeks. Why wouldn't it be a sound idea to have the planetographers pick out a couple of useless worlds which, at some points in their orbits, have diametrically opposite velocities, to within a degree or two?"
     "You've got something there, my boy. Will do. Very much worth having, just for its own sake, even if we never have any use for it. Anything else?"
     "Not a thing in the universe. Clear ether, chief!"

(ed note: the valiant Lensmen and the starship armada of the Galactic Patrol have discovered the location of the dread planet Jarnevon, the capital planet of the evil Boskone empire {or so they think, but I digress} There the sinister alien Eich lead by Eichmil have been busy fortifying it strong enough to repel any attack)

     Into the Second Galaxy the scarcely diminished armada of the Patrol hurtled—to Jarnevon's solar system—around it. Once again the crimson sheathing of Civilization's messengers almost disappeared in blinding coruscance as the outlying fortresses unleashed their mighty weapons; once again a few ships, subjected to such concentrations of force as to overload their equipment, were lost; but this conflict, though savage in its intensity, was brief. Nothing mobile could withstand for long the utterly hellish energies of the primaries, and soon the armored planetoids, too, ceased to be.

     "Maneuver fifty-nine—hipe!" and Grand Fleet closed in upon dark Jarnevon.
     "Sixty!" It rolled in space, forming an immense cylinder; the doomed planet the mid-point of its axis.
     "Sixty-one!" Tractors and pressors leaped out from ship to ship and from ship to shore.
     The Patrolmen did not know whether or not the scientists of the Eich could render their planet inertialess, and now it made no difference. Planet and fleet were for the time being one rigid system.
     "Sixty-two—Blast!" And against the world-girdling battlements of Jarnevon there flamed out in all their appalling might the dreadful beams against which the defensive screens of battleships and of mobile citadels alike had been so pitifully inadequate.
     But these which they were attacking now were not the limited installations of a mobile structure.

     The Eich had at their command all the resources of a galaxy. Their generators and conductors could be of any desired number and size. Hence Eichmil, in view of prior happenings, had strengthened Jarnevon's defenses to a point which certain of his fellows derided as being beyond the bounds of sanity or reason.
     Now those unthinkably powerful screens were being tested to the utmost.
     Bolt after bolt of quasi-solid lightning struck against them, spitting mile-long sparks in baffled fury as they raged to ground. Plain and encased in Q-type helices they came: biting, tearing, gouging. Often and often, under the thrust of half a dozen at once, local failures appeared; but these were only momentary and even the newly devised shells of the Patrol's projectors could not stand the load long enough to penetrate effectively Boskone's indescribably capable defenses.
     Nor were Jarnevon's offensive weapons less capable.
     Rods, cones, planes, and shears of pure force bored, cut, stabbed, and slashed. Bombs and dirigible torpedoes charged to the skin with duodec sought out the red-cloaked ships. Beams, sheathed against atmosphere in Q-type helices, crashed against and through their armoring screens; beams of an intensity almost to rival that of the Patrol's primary weapons and of a hundred times their effective aperture. And not singly did those beams come. Eight, ten, twelve at once they clung to and demolished dreadnought after dreadnought of the Expeditionary Force.
     Eichmil was well content. "We can hold them and we are burning them down," he gloated. "Let them loose their negative-matter bombs! Since they are burning out projectors they cannot keep this up indefinitely. We will blast them out of space!"

     He was wrong. Grand Fleet did not stay there long enough to suffer serious losses. For even while the cylinder was forming Kinnison was in rapid but careful consultation with Thorndyke, checking intrinsic velocities, directons, and speeds. "QX, Verne, cut!" be yelled.
     Two planets, one well within each end of the combat cylinder, went inert at the word; resuming instantaneously their diametrically opposed intrinsic velocities of some thirty miles per second. And it was these two very ordinary, but utterly irresistible planets, instead of the negative-matter bombs with which the Eich were prepared to cope, which hurtled then along the axis of the immense tube of warships toward Jarnevon. (the nut-cracker) Whether or not the Eich could make their planet inertialess has never been found out. Free (inertialess) or inert, the end would have been the same. (The tube of galactic patrol warships are using tractor beams on the planet Jarnevon to prevent it from becoming inertialess and running away)
     "Every Y14M officer of every ship of the Patrol, attention!" Haynes ordered. "Don't get all tensed up. Take it easy, there's lots of time. Any time within a second after I give the word will be p-l-e-n-t-y o-f t-i-m-e... CUT!"
     The two worlds rushed together, doomed Jarnevon squarely between them. (an inertialess object cannot be harmed unless it is either anchored by a tractor beam, or if the damage is applied equally on opposite sides. That's why the nut cracker needs two planets)

     Haynes snapped out his order as the three were within two seconds of contact; and as he spoke all the pressors and all the tractors were released. The ships of the Patrol were already free (interialess)—none had been inert since leaving Jalte's ex-planet—and thus could not be harmed by flying debris.
     The planets touched. They coalesced, squishingly at first, the encircling warships drifting lightly away before a cosmically violent blast of superheated atmosphere.
     Jarnevon burst open, all the way around, and spattered; billions upon billions of tons of hot core-magma being hurled afar in gouts and streamers. The two planets, crashing through what had been a world, met, crunched, crushed together in all the unimaginable momentum of their masses and velocities.
     They subsided, crashingly. Not merely mountains, but entire halves of worlds disrupted and fell, in such Gargantuan paroxysms as the eye of man had never elsewhere beheld. And every motion generated heat. The kinetic energy of translation of two worlds became heat.
     Heat added to heat, piling up ragingly, frantically, unable to escape!
     The masses, still falling upon and through and past themselves and each other melted—boiled—vaporized incandescently. The entire mass, the mass of three fused worlds, began to equilibrate; growing hotter and hotter as more and more of its terrific motion was converted into pure heat. Hotter! Hotter! HOTTER!
     And as the Grand Fleet of the Galactic Patrol blasted through intergalactic space toward the First Galaxy and home, there glowed behind it a new, small, comparatively cool, and probably short-lived companion to an old and long-established star.

From GRAY LENSMAN by E. E. "Doc" Smith (1939)

Nicoll-Dyson Laser

if your budding "Weakly Godlike civilization" wants to graduate to Kardashev Type II, they have to harness all of the power available from a single star. Presumably the primary around which their homeworld orbits. The obvious technique is to surround the entire blasted star with solar power collectors so not a single solar photon wastefully escapes into deep space. The concept was invented by Olaf Stapledon in Star Maker (1937) and later popularized by Freeman Dyson in his 1960 paper "Search for Artificial Stellar Sources of Infrared Radiation" (abstract). Due to the second law of thermodynamics some of the power is going to show up as waste heat, making the "Dyson Sphere" resemble a red giant star. If astronomers do not look closely they may dismiss an observation of an alien megastructure as "just another boring red giant." Naturally science fiction authors fell in love with the concept so there is no shortage of examples in the literature.

But now that your ultra-civilization has access to around 400 yottawatts of power, what are you going to do with it?

Noted science fiction personage James Davis Nicoll had the answer. He brainstormed the concept of the dreaded Nicoll-Dyson Laser. Take the most practical variant, the so-called Dyson Swarm. Equip each of the swarm satellites with a phased array laser. Now you can emit a planet-frying death ray capable of ending all life on any world within a range of anywhere in the Local Group of Galaxies. Timelag is going to be a huge issue, but anyone who can build a Dyson swarm ought to be able to deal with it.

Naturally, as is always the case with any arms race, things get complicated if a second civilization builds one of these planet-pasteurizers. Or several thousand for that matter. Here on Terra we reacted to a similar situation with the doctrine of Mutual Assured Destruction. I'm sure the ultra-civilizations will cosmically sophisticated interlocking strategies far beyond our mental keen.

Such a beam does have non-military applications. For instance it can turn a humble laser-sail spacecraft into a relativistic starship.



Large time-domain surveys, when of sufficient scale, provide a greatly increased probability of detecting rare and, in many cases, unexpected events. Indeed, it is these unpredicted and previously unobserved objects that can lead to some of the greatest leaps in our understanding of the cosmos. The events that may be monitored include not only those that help contribute to our understanding of sources astrophysical variability, but may also extend to the discovery and characterization of civilizations comprised of other sentient lifeforms in the universe. In this paper we examine if the Large Synoptic Survey Telescope (LSST) will have the ability to detect the immediate and short-term effects of a concave dish composite beam superlaser being fired at an Earth analog from an alien megastructure.

III. Blast Modeling

     We investigate the activity and immediate aftermath of a planet-destroying laser blast with a series of approximations. We consider our target to be an Earth-analog, and so we use the properties in Table 1 for this planet, with values from Kite et al. (2009). We additionally use approximations of the average temperature of the core and mantle as 6000K and 1270K, respectively. Previous work has already examined the question of the energy needed to destroy a planet in this way, and we use their value of 2 × 1032 J in order to destroy an Earth-like planet (Boulderstone et al., 2011). However, it would not be realistic to treat the superweapon as fully efficient, and so we use values based off of nuclear explosions, where 50% of the energy goes into the kinetic energy of the planet, 35% into thermal radiation that raises the temperature of the planetary material, and 15% into an immediate, short-duration flash of electromagnetic radiation2. The observable energy from the explosion then comes from two components, the immediate release of energy during the explosion (what we refer to as the ’flash’) and the long-term thermal radiation from the debris of the planet (what we refer to as the ’remnant’). For the flash, we treat this as a blackbody with a surface of the Earth that will release all of the energy of this component in 2 seconds, or the equivalent of blackbody radiation for a surface at 106 K. We consider the debris of the planet to be well-mixed and be of a single temperature, and when this is calculated for the total energy, we find it to be a blackbody with a temperature of 29,000K. As this is occurring while the planet is being destroyed, the radius will be increasing, however as the escape velocity is 11 km/s we treat this object as consistent with earth-sized for the immediate aftermath. A more time-dependent examination would require accounting for the debris cloud growing in size, as well as the cooling of the debris (a time scale on order of 100 days if approximated as linear cooling) and changes to the optical depth of the debris cloud.

Table 1: Earth Properties
Earth mass5.97 × 1024kg
Earth radius6.37 × 106m
Core mass fraction0.325
Specific heat capacity, mantle914J K-1 kg-1
Specific heat capacity, core800J K-1 kg-1

     We show the blackbody curves for the flash and the remnant in Figure 2. We also include a blackbody curve for a Sun-like star at 5800K for comparison. We then convolve each of these blackbody curves with the filter throughputs for LSST. Unsurprisingly considering the high temperatures involved, we see that the most significant contributions from both the flash and the remnant will occur in the bluer bands. We treat the solar-mass star as our reference for calibrating the absolute magnitudes by using the method for determining the absolute magnitude in each band using the method that was outlined in Lund et al. (2015). We then compare the total flux in each bandpass for the Sun and for the flash and remnant in order to get relative magnitudes, followed by absolute magnitudes. An important consideration here is that the radius of the planet must be included in these calculations, and so the remnant is a close analogue of a white dwarf in radius and temperature. The absolute magnitudes that we determine are listed in Table 2. It becomes readily apparent that the remnant is generally no more than 1% of the brightness of a solar-mass star, and the flash is only brighter than a solar-mass star in the u band.

Table 2: Absolute Magnitudes

     These results are even more constraining than they may appear at first glance. The simulated flash duration is 2 seconds, however LSST will have exposures that are 15 seconds in duration. To correctly get the measured apparent magnitude, this difference in duration has to be accounted for, and the flash will look on order of 2 magnitudes fainter in the 15-second exposures of LSST, meaning that it will be slightly fainter than the star. As an inhabited Earth-analog planet (and, therefore, any planet likely worth destroying) would be expected to be around a solar-mass star, the light from the flash and remnant would have to be of considerable brightness with respect to the host star to be observed, and it does not appear that this is the case.

     There are, however, three scenarios that may result in the destruction event still being detectable. The first is if the star and planet are close enough to our Solar System that the planet’s destruction can be angularly resolved. Given that LSST will saturate at 16th magnitude, however, it seems extremely unlikely that any geometry exists where this would be possible. The second is if the planet is orbiting a smaller star. A red dwarf, for example, will be several magnitudes fainter, particularly on the bluer end of the LSST filter set. In this case, the flash, and possibly the remnant, will be brighter than the host star. While red dwarfs have not been the typical stars searched for planets in the past, there is no reason to think that an inhabited planet could not orbit around a red dwarf. Finally, the flash in the u band is still brighter than a solar mass star if it is observed instantaneously. In the case of LSST or other survey, this could also be accomplished by having a shorter exposure time, and so an exposure of 2-3 seconds would mean that any flash from a planetary explosion will be significantly brighter than the host star. In the case of LSST, however, the costs of this change to the observing schedule greatly outweigh this benefit as it would significantly curtail the observations that LSST will be able to make of fainter objects.


      The power of a collimated beam is limited by the focus of the beam when it reaches a distant target. One way to improve this focus is to increase the effective aperture of the emitter; a very large object, such as a Dyson Swarm, represents a very large effective aperture if it is used to emit such a beam.
     Dyson Swarms collect considerable amounts of energy from the stars they contain; if some of that energy can be stored, then directed towards a target in a different planetary system, considerable damage can result. In practice the outermost elements of the swarm, or the outer surface of a dynamically supported Dyson Shell (if present) become a phased array emitter. This allows a powerful beam to be focused on a distant target in another planetary system. This concept was first suggested by James Nicoll in the Information Age, and is known as a Nicoll-Dyson Beam for this reason.
     Nicoll-Dyson beams are routinely used to propel laser-sail craft at interstellar distances, and have been used to send messages to distant locations. Several messages have been sent by Nicoll-Dyson arrays to locations outside the Terragen Sphere, particularly to the closest High-energy emitting civilisations which have been detected in the Milky Way galaxy.
     Nicoll-Dyson arrays can also be used as weapons; severe damage can be inflicted on a planet's surface or on a megastructure at great distances. They have, however, rarely been used destructively; a number of beams were fired during the Oracle War, for instance, but they are regarded as weapons of last resort. If a beam is fired, this results in significant destruction in a distant system many years later — during the intervening period wars may have ended, treaties may have been signed, and the political landscape may have changed- but still the beam is on its way and cannot be recalled.
     Using powerful telescopes including the Argus Array, evidence of high-energy conflict has been observed in several distant galaxies; the use of Nicoll-Dyson beams has been confirmed in a number of cases, and is suspected in others.
     There are today many Dyson swarms and similar constructs in the Terragen Sphere, many of which are not part of the Sephirotic Empires such as those built by the Panvirtuality and the Efficiency Maximisation Paradigm. If interstellar relations ever decay to the point where Nicoll-Dyson beams are used en masse, the Orion's Arm Civilisation could be damaged or even destroyed in a very short time.
     Some commentators relate this to the mystery of the Great Toposophic Filter and the disappearance of so many xenosophont empires in the past.

From NICOLL-DYSON BEAMS by Steve Bowers (2009)


In the novel Ringworld, our heroes are exploring the eponymous megastructure. At one point their ship is moving on a vector close to a collision course with the Ring. That's when they find out the hard way that the Ringworld has a meteor defense system. A large X-ray laser fires upon their ship. They only survive because the ship is equipped with a stasis field for defense. Later, Louis Wu figures that the x-ray laser is mounted on the shadow squares.

He's wrong.)

      From a thousand miles up, one could see a long way before the blanket of air blocked the view. And for most of that distance, there wasn't a single island! The contours of sea bottom showed, and some of that was shallow enough. But the only islands were far behind, and those had probably been underwater peaks before Fist-of-God distorted the land.
     There were storms. One looked in vain for the spiral patterns that meant hurricane and typhoon. But there were cloud patterns that looked like rivers in the air. As you watched them, they moved: even from this height, they moved.
     The kzinti who dared that vastness had not been cowards, and those who returned had not been fools. That pattern of islands on the starboard horizon — you had to squint to be sure it was really there — must be the Map of Earth. And it was lost in all that blue.

     A cool, precise contralto voice eased into his thoughts. (an alien Puppeteer named Hindmost said) “Louis? I have reduced our maximum velocity to four miles per second.”
     “Okay.” Four, five — who cared?
     “Louis, where did you say the meteor defense was located?”
     Something in the puppeteer's tone ... “I didn't say. I don't know.”
     “The shadow squares, you said. You're on record. It must be the shadow squares if the meteor defense can't guard the Ringworld's underside.” No overtones, no emotion showing in that voice.
     “Do I gather I was wrong?”

     “Now, pay attention, Louis. As we passed four point four miles per second, the sun flared. I have it on visual record. We didn't see it because of the flare shielding. The sun extruded a jet of plasma some millions of miles long. It is difficult to observe because it came straight at us. It did not arch over in the sun's magnetic field, as flares commonly do.”
     “That was no solar flare that hit us.”
     “The flare stretched out several million miles over a period of twenty minutes. Then it lased in violet.”
     “Oh my God.”
     “A gas laser on a very large scale. The earth still glows where the beam fell. I estimate that it covered a region ten kilometers across: not an especially tight beam, but it would not normally need to be. With even moderate efficiency, a flare that large would power a gas laser beam at three times ten to the twenty-seventh power ergs per second (3×1020 joules/sec), for on the order of an hour (total 1.08×1024 joules or about 3 dinosaur-killer asteroids).”

     “Give me a minute. Hindmost, that is one impressive weapon.” It hit him, then: the secret of the Ringworld engineers. “That's why they felt safe. That's why they could build a Ringworld. They could hold off any kind of invasion. They had a laser weapon bigger than worlds, bigger than the Earth-Moon system, bigger than ... Hindmost? I think I'm going to faint.”
     “Louis, we don't have time for that.”
     “What caused it? Something caused the sun to jet plasma. Magnetic, it has to be magnetic. Could it be one function of the shadow squares?”
     “I wouldn't think so. Cameras record that the shadow square ring moved aside to allow the beam to pass, and constricted elsewhere, presumably to protect the land from increased insolation. We cannot assume that this same shadow-square ring was manipulating the photosphere magnetically. An intelligent engineer would design two separate systems.”

(ed note:the magnetic system is a series of titanic superconducting magnets embedded in the Ringworld floor)

From THE RINGWORLD ENGINEERS by Larry Niven (1979)

Cirys superzorcher (n.): A hypothetical weapons system in which the various elements of a Cirys swarm (q.v.) are equipped to function as the radiative elements of a phased-array laser. Such an array, with an effective aperture equal to the diameter of the swarm, would theoretically be able to deliver a substantial portion of the total solar output of the contained star in a single beam against targets located at interstellar distances.

Occasional peaceful uses for such beams have been mooted, including laser sail propulsion (although it should be noted that there is little call for such craft on a larger scale than existing propulsion arrays – which have the advantage of being mobile – can handle, and the ability to build a laser-sail craft capable of surviving such propulsion is questionable), long-distance, including extragalactic, communications (a matter of great interest to the Elsewhere Society), and even remote power generation and delivery.

However, while condemned by Cirys Aendyr himself – who is said to have wept when this application of his concept was brought to his attention – the most common proposal is to use the Cirys superzorcher as the weapons system implied by its name. The ability to place so much power on target (a figure of the order of 108 exawatts for a Hearth-class star) across interstellar distances, capable of vaporizing lithic worlds and severely damaging gas giants and stars, is peculiarly attractive to certain types of mentality, especially when it is considered that the purely photonic beam of a superzorcher is substantially more difficult to detect than a typical RKV, and cannot be practically intercepted or recalled.

As such, while the Cirys superzorcher requires a high degree of technological advancement and autoindustrialism to produce (a potential currently limited to the Empire and certain other Core Markets) and is in any case a prohibited weapons system (classified as a Tier I star-killer under the Ley Accords), an informal consensus exists among the Presidium powers that the construction of such a device by any polity, within or without the Worlds, may be reasonably interpreted as notice of intent to commit gigacide, and as such is a legitimate cause for preemptive defense of the highest order.

– A Star Traveler’s Dictionary

Nova Bomb

When merely burning off a planet is not violent enough, pulp science fiction loves to turn the volume up to 11 with the Nova Bomb. None of this fooling around carpet bombing with nuclear weapons, just induce the primary star to explode and incinerate the entire enemy solar system. Use this when the alien species is so horribly dangerous that it absolutely, positively has to be exterminated 100% overnight. You will be sure none of the enemy species escapes (unless they have one of those pesky "jump-type" faster-than-light starships that are immune to your military blocade).

There are no known scientific ways to cause an instant nova, with the possible exception of a strangelet bomb. And even that may be more handwavium than unobtainium.


      Just outside the expanding light cone of the present a star died, iron-bombed.

     Something—some exotic force of unnatural origin—twisted a knot in space, enclosing the heart of a stellar furnace. A huge loop of superstrings twisted askew, expanding and contracting until the core of the star floated adrift in a pocket universe where the timelike dimension was rolled shut on the scale of the Planck length, and another dimension—one of the closed ones, folded shut on themselves, implied by the standard model of physics—replaced it. An enormous span of time reeled past within the pocket universe, while outside a handful of seconds ticked by.

     From the perspective of the drifting core, the rest of the universe appeared to recede to infinity, vanishing past an event horizon beyond which it was destined to stay until the zone of expansion collapsed. The blazing ball of gas lit up its own private cosmos, then slowly faded. Time passed, uncountable amounts of time wrapped up in an eyeblink from the perspective of the external universe. The stellar core cooled and contracted, dimming. Eventually a black dwarf hung alone, cooling toward absolute zero. Fusion didn’t stop but ran incredibly slowly, mediated by quantum tunneling under conditions of extreme cold. Over a span billions of times greater than that which had elapsed since the big bang in the universe outside, light nuclei merged, tunneling across the high quantum wall of their electron orbitals. Heavier elements disintegrated slowly, fissioning and then decaying down to iron. Mass migrated until, by the end of the process, a billion trillion years down the line, the star was a single crystal of iron crushed down into a sphere a few thousand kilometers in diameter, spinning slowly in a cold vacuum only trillionths of a degree above absolute zero.

     Then the external force that had created the pocket universe went into reverse, snapping shut the pocket and dropping the dense spherical crystal into the hole at the core of the star, less than thirty seconds after the bomb had gone off. And the gates of hell opened.

     Iron doesn’t fuse easily: the process is endothermic, absorbing energy. When the guts were scooped out of the star and replaced with a tiny cannonball of cold degenerate matter, the outer layers of the star, held away from the core by radiation pressure, began to collapse inward across a gap of roughly a quarter million kilometers of cold vacuum. The outer shell rushed in fast, accelerating in the grip of a stellar gravity well. Minutes passed, and from the outside the photosphere of the star appeared to contract slightly as huge vortices of hot turbulent gas swirled and fulminated across it. Then the hammerblow of the implosion front reached the core . . .

     There was scant warning for the inhabitants of the planet that had been targeted for murder. For a few minutes, star-watching satellites reported an imminent solar flare, irregularities leading to atmospheric effects, aurorae, and storm warnings for orbital workers and miners in the asteroid belt. Maybe one or two of the satellites had causal channels, limited bandwidth instantaneous communicators, unjammable but expensive and touchy. But there wasn’t enough warning to help anyone escape: the satellites simply went off-line one by one as a wave of failure crept outward from the star at the speed of light. In one research institute a meteorologist frowned at her workstation in bemusement, and tried to drill down a diagnostic—she was the only person on the planet who had time to realize something strange was happening. But the satellites she was tracking orbited only three light minutes closer to the star than the planet she lived on, and already she had lost two minutes chatting to a colleague about to go on her lunch break about the price of a house she would never buy now, out on the shore of a bay of lost dreams.

     The hammerfall was a spherical shock wave of hydrogen plasma, blazing at a temperature of millions of degrees and compressed until it had many of the properties of metal. A hundred times as massive as the largest gas giant in the star system, by the time it slammed into the crystal of iron at the heart of the murdered star it was traveling at almost 2 percent of lightspeed. When it struck, a tenth of the gravitational potential energy of the star was converted into radiation in a matter of seconds. Fusion restarted, exotic reactions taking place as even the iron core began to soak up nuclei, building heavier and hotter and less stable intermediaries. In less than ten seconds, the star burned through a visible percentage of its fuel, enough to keep the fires banked for a billion years. There wasn’t enough mass in the G-type dwarf to exceed the electron degeneracy pressure in its core, collapsing it into a neutron star, but nevertheless a respectable shock front, almost a hundredth as potent as a supernova (about 1×1042 Joules), rebounded from the core.

     A huge pulse of neutrinos erupted outward, carrying away much of the energy from the prompt fusion burn. The neutral particles didn’t usually react with matter; the average neutrino could zip through a light year of lead without noticing. But there were so many of them that, as they sluiced through the outer layers of the star, they deposited a good chunk of their energy in the roiling bubble of foggy plasma that had replaced the photosphere. Not far behind them, a tidal wave of hard gamma radiation and neutrons a billion times brighter than the star ripped through the lower layers, blasting them apart. The dying star flashed a brilliant X-ray pulse like a trillion hydrogen bombs detonating in concert: and the neutrino pulse rolled out at the speed of light. Eight minutes later—about a minute after she noticed the problem with the flare monitors—the meteorologist frowned. A hot, prickling flush seemed to crawl across her skin, itching: her vision was inexplicably streaked by crawling purple meteors. The desk in front of her flickered and died. She inhaled, smelling the sharp stink of ozone, looked round shaking her head to clear the sudden fog, and saw her colleague staring at her and blinking. “Hey, I feel like somebody just walked on my grave—” The lights flickered and died, but she had no trouble seeing because the air was alive with an eerie glow, and the small skylight window cast razor-sharp shadows on the floor. Then the patch of floor directly illuminated by the window began to smoke, and the meteorologist realized, fuzzily, that she wasn’t going to buy that house after all, wasn’t going to tell her partner about it, wasn’t ever going to see him again, or her parents, or her sister, or anything but that smoking square of brilliance that was slowly growing as the window frame burned away.

     She received a small mercy: mere seconds later the upper atmosphere—turned into an anvil of plasma by the passing radiation pulse—reached the tropopause. Half a minute later the first shock wave leveled her building. She didn’t die alone; despite the lethal dose they all received from the neutrino pulse, nobody on the planet lived past the iron sunrise for long enough to feel the pangs of radiation sickness.

From IRON SUNRISE by Charles Stross (2004)

      “To start with, have you ever heard of Earth?”
     “Which one? There are a couple of planets in this sector by that name, and another one in near the Hub somewhere. I can’t say I know much about any of them.”
     “The Earth I'm talking about is the original one. Over in the Sirius sector. The birthplace of the human race, millions of years ago.”
     “You mean such a place actually exists? I thought it was nothing more than a legend, a myth for children." Zim shook his head in puzzlement, then took another long drink from the glass in front of him.
     “No, I assure you it isn’t a myth. Earth, old Earth, actually exists, and it is really the original home of mankind. Let me fill you in a little on the background.
     “As near as we can determine from the records, something like seventeen hundred years ago man was confined to that one system, Sol. Space travel had developed slowly, until the invention of the inertialess drive, which opened up the stars. Over the next several hundred years, the men of Earth went out, colonizing uninhabited planets and contacting other species.
     “That outward surge of explorers and colonists almost killed the home planet. The best of their young men left for the stars, never to return. The resources of the entire system were looted to build the many ships required, all in the hope that eventually the colonies would begin to ship back to the home system raw materials that Earth vitally needed. Earth wished to evolve into a governmental center of an interstellar empire. The member planets would provide the material goods while Earth provided the direction.
     “Unfortunately, it didn’t work out quite that way. A pattern emerged. A colony would be founded and it would take several generations to become self-sufficient. Once the colony developed to the point where it had sufficient materials to send the surplus off-planet, it began an expansion policy of its own, establishing daughter colonies rather than sending the surplus back to Earth.
     “The situation soon became intolerable for Earth, and the central government attempted to enforce its policy. The reaction was predictable: the colonies revolted. At first Earth countered with blockades and confiscation of shipping; but eventually she resorted to weapons, and the war was on.
     “Several of the older colonies formed a loose confederation and attacked Earth. They assumed that they were getting involved in nothing more than a police action, considering the state of Earth’s resources, but they forgot one very important fact. At that time, poor as she may have been in military-minded young men and the raw materials needed to support an interstellar war machine, Earth still had the greatest concentration of technical know-how and scientific development potential in the known universe.
     “The confederation of rebel planets ringed the Earth system—the Solar System—with warships, then bombed the colonies on the fourth planet to rubble as a demonstration of its powers. Then it sat back and waited, two years, for Earth’s surrender. When the reaction finally came it was nothing they could have expected. In those two years Earth developed weapons of such fantastic power that no colonial fleet, no matter how large, could stand against her ships. Unfortunately, Earth could not possibly maintain exclusive use of those new weapons. Ships were occasionally captured and their weapons copied. Scientists of the colonies also came up with some new weapons of their own, but Earth had a commanding lead. In no way could the Earth fleets be stopped—only slowed, dragging out the war. Then Earth came up with a weapon that has never been copied since.
     “Out of the laboratories of the home world came a bomb capable of exploding a sun! A nova bomb, that could erase every trace of life from a system and leave it completely uninhabitable. With that weapon the Earth government completely destroyed every one of the colonies that had made up the confederation, ringing the section of space around the Solar System with a swath of burned-out suns.
     “Over one hundred billion people died in that war. There’s no telling what eventually might have happened if the people of Earth, common citizens and government officials alike, hadn’t recoiled in horror at what was being done. The reaction destroyed the government that had planned to rule the stars; Earth, with the threat of the nova bomb to back her words, closed the space around her system, renouncing the stars forever. For twelve hundred years Earth has been all but completely cut off from that part of human civilization that eventually evolved into the Hub Federation. Not more than one ship a century has visited Earth, and as far as we know, in all that time only two Earth ships have ventured into the galaxy beyond the ring of dead stars.”
     “With the end of the war a tremendous religion revival swept over Earth. Science and technology weren’t eliminated, but they stagnated, and science was eventually replaced by mechanics. All the benefits of a highly technological society were kept, but advancement ended. Over the centuries, the religion was replaced by a philosophical orientation, that continued to develop until last year.
     “By Federation standards, the population Earth chooses to maintain is small; but even within a population measured in the hundreds of millions, a fairly large number are bound to be dissatisfied with the calm and unhurried pace of a contemplative society. Most of them found outlets for their energy in the mechanical trades, which allowed the society of thinkers to exist without material effort, and it was assumed that the social situation was stable.
     “Then, last year, one of the mechanics, actually a botanist, made a revolutionary discovery after he accidentally irradiated a culture of mutant bacteria he had discovered growing on some yeast cakes. He found a way to synthesize antiagathics.
     “Even after twelve hundred years, the memory of what they had done to those billions of colonists burned in the consciences of the men of Earth. With this discovery, the Earth government, sort of an ethical technocracy, saw a way to wipe out at least a part of their guilt and shame, Their leader—his title is President—and a few aides took one of their carefully preserved starships and came to the Hub to make arrangements for a scientific team to be sent to Earth. While the President was establishing relations with the Hub Federation, a major political change took place on Earth. In effect, the mechanics revolted and took over the government. This faction is led by a former computer design engineer who our psychology service has tentatively identified as a Messiah-type. He apparently plans to make Earth central ruling planet of the empire of man.”
     “And I suppose he has the nova bomb,” Zim commented quietly.
     “He has. When the original Earth government fell, every bomb in existence was dismantled and the components put into solar-impact orbit. Every set of plans, every textbook description, every thesis on the subject was confiscated and destroyed. And everyone who knew anything about the construction of the bomb was sworn to secrecy.”
     “After the fact, suppression of scientific advances seldom seems to work, though,” Zim commented.
     “It worked for twelve hundred years. And probably would have worked even longer, except that the University of Earth maintains a history data bank in which a complete description of the nova bomb lay forgotten. The leader of the revolt came across those plans, and researching the history of the use of the bomb probably triggered the Messiah complex in him. He started with the conviction that he was right, gained political support, and now he has revived the nova bomb as the weapon needed to achieve his ultimate goal. All that stands in his way is a technicality—his election to the presidency of Earth, an event he is sure to engineer before long.

From VOYAGE TO A FORGOTTEN SUN by Donald Pfeil (1975)

      Rolf came out of the ship, with Jommor and Tharanya. They began to walk across the plain, the fresh breeze lifting their hair and tugging at their garments.
     Banning's face contracted as though with some deep agony. He went on again, toward the Hammer. It towered up, reared high on a platform as big as Manhattan Island—or at least it seemed so, to Banning's dazed eyes. It was shaped in some ways like a cannon, and in others like—no, not like anything else. Like itself alone. There had only been one Hammer. And it was the first, the beginning, the experiment carried out in the lost and secret place where there was ample material for the Hammer to crush, from whence it could reach out to—
     A ladder led him up onto the platform, a ladder made of some wizard joining of ceramic and metal that would outlast the land it stood on. The platform, too, was built of a substance that had not weathered or corroded. A door of cerametal led inside, to a chamber underneath, and there were controls there, and mighty dynamos that drew power from the magnetic field of the planet itself. Banning said harshly to Sohmsei, “Keep them out."
     The Arraki looked at him—was it love and trust, or a loathing terror that showed in his eyes? Banning's own gaze was uncertain, his breath painful in his throat, his hands shaking like those of an old man with the palsy.
     Now, now! Which was it to be, the Old Empire and the throne of the Valkars, the banner blazened with the sunburst? Or surrender to the mercy of Tharanya and Jommor, not only himself but Rolf and Behrent and all the others?
     Banning put his hand on the breast of his tunic, and felt the symbol there, the sunburst bright with jewels. And suddenly he sprang forward in the silent room, toward the levers, the sealed imperishable mechanisms that held within them the coiled might of the Hammer.
     He remembered. He remembered the tradition handed down from father to son, and the things that were written in the ancient books among the archives. Ambition had burned them into his mind, and greed had fixed them there with an etching of its own strong acid. He remembered, and his hands worked fast. Presently he went out of the chamber and down the ladder, to where Jommor and Tharanya and Rolf were waiting with the two Arraki, five grim shapes at the end of the world. Rolf started to ask a question, and Banning said, “Wait."
     He looked up.
     From the colossal pointing finger of the Hammer, there leapt up a long lightning-stroke of sullen crimson light. A giant stroke that darted toward the yellow sun in the heavens, that flared and glared—and then was gone.
     There was nothing more.
     Banning felt his bones turn to water. He felt the horror of a supremely impious action. He had done a thing no man had done before—and be was afraid.
     Rolf turned toward him, his face wild and wondering. The others were staring puzzledly, disappointedly.
     "Then—it doesn't work?” said Rolf. “The Hammer—it does nothing—" Banning forced himself to speak. He did not look at Rolf, he was looking at the growing sunspot that had appeared on the yellow star, a blaze of greater brightness against the solar fires. His horror at himself was mounting.
     "It works, Rolf. Oh, God, it works—"
     "But what? What—"
     "The Hammer,” said Banning thickly, “is a hammer to shatter stars." They could not take that knowledge into their minds at once, it was too vast and awful. How could they, when his own mind had recoiled from it for all these terrible hours?
     He had to make them believe. Life or death hung upon that now.
     "A star,” he said painfully, “nearly any star—is potentially unstable. Its core a furnace of nuclear reactions, from which hydrogen has been mostly burned away. Around that core a massive shell of much cooler matter, high in hydrogen content. The trapped, outward-pushing energy of the central furnace keeps the cooler shell from collapsing in upon it."
     They listened, but their faces were blank, they could not understand and he must make them understand, or perish.
     Banning cried, “The Hammer projects a tap-beam—a mere thread compared to stellar mass, but enough to let that pushing energy of the nuclear core drain out to the surface. And without that push of radiation to hold out the shell—"
     Understanding, an awful understanding, was coming into Jommor's face. “The shell would collapse in upon the core,” he whispered.
     "Yes. Yes—and you know what the result is when that happens." Jommor's lips moved stiffly. “The cooler shell collapsing into the super-hot core—it's the cause of a nova—"
     "Nova?” That, at least Rolf could comprehend, and the knowledge struck a stunned look into his eyes.
     “The Hammer could make any star a nova?"

From STARMAN COME HOME by Edmond Hamilton (1954)

      The captain watched him speculatively. It struck York that were Hull Earth-born, he undoubtedly would be commanding an N-ship instead of a destroyer at the ragged fringes of space. True, the Draco carried long-range lasers, cobalt warheads, nucleonic bolts—all the conventional weapons—but not the dread N-bomb. By unwritten Empire law, only a born Earthling could command an N-ship. In short, the Draco couldn’t nova a sun.
     “Empire Intelligence.” Hull murmured the words quietly, yet somehow his voice betrayed doubt and wonder.
     “That is in confidence.” York contemplated the captain calmly. If the Empire’s galactic Navy were the instrument that kept over two thousand inhabited planets living in controlled harmony, it was the shadowy Empire Intelligence that nipped discord in the bud, kept the Empire intact. Without E.I., as it was called, the restless worlds of the Alphan suns would long since have challenged the Empire’s yoke, N-bomb or no N-bomb. Prince Li-Hu of the Alphan world Shan-Hai, who traced his ancestry back in an unbroken line to the emperors of the ancient Earth nation of China, had both feet planted squarely in the middle of the captain’s present emergency, even though Hull didn’t know that.
     “Authority that’s residual in a card?” snapped Hull. “How do I know that you’re Daniel York?”
     “By my knowledge.”
     “What knowledge?”
     “Your rush to push the Draco into space,” replied York. “You were slated to remain on Upi for another week. Now you’re rushing under secret orders.”
     “Keep talking, Mr. York, and you might wind up on a detention world.”
     “No, thanks.” York leaned forward and said deliberately, “The N-bomb cruiser Rigel is missing. First Level picked up a distress call from the region of Ophiucus. That was two days ago. Since then there hasn’t been a word. Lost—one N-cruiser. That’s your emergency.”
     “That knowledge is restricted to First Level—”
     “And to the captain of the Draco because you happen to be nearest the scene,” cut in York.
     “You know too much. Tell me, Mr. York, just who are you?”
     York grinned and said, “E.I.”
     “I don’t know that.”
     “You also don’t know that the Rigel was sabotaged,” York boldly challenged.
     “No …” Hull breathed the word slowly, a startled look crossing his face. Abruptly he straightened. “There hasn’t been a case of sabotage in over three centuries.”
     “The record just fell,” declared York.
     “I can’t believe that!”
     “The Rigel was sabotaged—captured, if you will—and forced to land somewhere in the Ophiucus region for the purpose of stealing the N-bomb. And Prince Li-Hu is in back of it, Captain. Make no mistake about that.”
     “I would have agreed with you last week,” York said calmly, “but that’s last week.” He spread his hands. “The Empire is maintained only through sole possession of the N-bomb. Its existence—monopoly, if you will—is the Empire’s guarantee of solidarity. No world is apt to rebel against a power which could nova its sun, Captain.”
     “You don’t sound particularly sympathetic.”
     “Practical,” answered York. “We live by the sword, but we don’t want to perish by it.”
     “What you say amounts to an accusation, York.”
     “It does,” he answered.
     “No planetary government would dare use the bomb. That’s if they could steal it, which they couldn’t.”
     “Correct, but neither would the Empire use it—not if the ability to retaliate existed.” York heard the sound of closing hatches and restrained his impatience. “Once the bomb is out of Empire hands, its power is negated. You can see what that means, Captain. With that fear removed, you’d see a dozen revolts overnight.”
     “I fail to see that, Mr. York.”
     “You are a military man, Captain. To you war means laser beams, nucleonic bolts, the burst of cobalt bombs.”
     Hull asked coldly, “What does it mean to you?”
     “Plotting, espionage, murder—men in high places conniving for power.” He held the captain’s gaze. “A knife in the back can win or topple an empire as quickly as a cobalt bomb, and with far less mess. History’s filled with such fallen empires,” he finished.
     “You make a dramatic case of it,” the captain observed.
     “Dramatic? Presto”—York snapped his fingers—“and one N-cruiser is gone. Yes, I believe you might call it dramatic.”

From THE PROGRAMMED MAN by Jean Sutton and Jeff Sutton (1968)

It might also be just as well to restrict sharply the technical information the city passed out in this star system. If the Hamiltonians—or the Hruntans—suddenly blossomed out with Bethe blasters, field bombs, and the rest of the modern arsenal (or what had been modern the last time the city had been able to update its files, not quite a century ago), the police would be unhappy. They would also know whom to blame. It was comforting to know that nobody in the city knew how to build a Canceller, at least. Amalfi had a sudden disquieting mental picture of a mob of Hruntan barbarians swarming out of this system in spindizzy-powered ships, hijacking their way back to an anachronistic triumph, snuffing out stars like candle flames as they went.

From EARTHMAN, COME HOME by James Blish (1955)

The only exception to the general picture of Telesthetic star faring races as relatively temperate, pragmatic, and ultimately cooperative peoples is the Xenophobe Experience. In their manic incursions into Pan Sentient space, planting conversion triggers in stars to murder whole planetary populations, the Xenophobes severely strained the image of the Telesthetic as the pacific influence upon the wilder elements of any race. Seven billion sentients on Triplet were incinerated by induced nova because the crew of their Gate couldn't believe that the unidentifiable Star Force Tac-Shifting towards their sun was capable of such a hideous act.

It was, as they say "a pearl harbor" that mobilized the wrath of 280 billion sentients and sent the Combined Pan Sentient Star Wing to smash the Xenophobes back into their own Volume after the First Incursion. After the Second Incursion, the PSL forsook all temporizing and launched the Expedition of Punishment and Retribution into Xenophobe space. Thirty-seven Xeno systems were "purified" of that hateful life-form, using Conversion bombs, focused Heissen fields at lethal intensities, Rame killer swarms, and finally kilometer-by-kilometer extermination sweeps by Human / LChal-Dah Star Soldiers. The Xenophobe home system was reduced to a population of one billion, all of whom were Blanked and gene-washed. The planet was sealed with a standing discontinuity net tied to a conversion trigger orbiting the star.

The Star Gate called "The Lid" was placed in trans-system orbit to monitor the net, maintain the trigger, and to "pull the plug" should the Xenos ever so much as attempt to lift out of the atmosphere again. The Expedition took 1.7 Standard Years to complete at a cost in PSL life of 3.7 million battle deaths, 21 Teleships destroyed, 803 Telesthetics were permanently dysfunctional (Blanked). The Xenophobes lost 127 billion sentients, 98 Teleships destroyed via Telesthetically implanted conversion warheads, 34 Teleships destroyed by Rame Sacrifice Teams, 28 Gates destroyed by Rame Sacrifice Teams, 9 by Human/ LChal-Dah Star Soldier assault groups using low-energy approach. Eleven Xenophobe Teleships remain unaccounted for (assumed lost in fragmented randomization).

Total PSL civilian deaths in the First and Second lncursions:41.315 billion sentients.



After two and one-half centuries of generally pacific conduct and gradual terraforming of all the depicted star systems, the PSL (Pan-Sentient League) sphere was invaded by a rabid species known only as the "Xenophobes". They began inducing novas in PSL stars (causing them to explode) incinerating the inhabitants. Not knowing where they were coming from, and the thought pattern being so alien as to be largely undetectable, the PSL StarForces were forced to search the periphery of its Known Volume for the Xenophobe "base camp" StarGates. The Xenophobes were inhibited by smaller shifts due to unfamiliarity with the PSL Volume.


Scenario continues until all Xeno StarGates have been destroyed or all PSL Home Systems stars (Sol, Sigma Draconis, and 70 Ophiuchi) have gone nova. At that time, Victory is determined according to the number of Victory Points, the Player with the higher total winning.



After the First Incursion of the Xenophobes had been driven off by the PSL, a watchful peace ensued. Approximately 30 billion PSL sentients died in the First Incursion, creating a shortage of telesthetics and forcing a reduction in the number of PSL StarForces. 10 years after the First Incursion, the Xenophobes returned.


The Xenophobe murderers use the star of the system as a weapon. By planting a Conversion Trigger in the heart of the sun they cause it to nova (greatly accelerate its energy output) in order to scorch the orbiting planets and destroy all life. In order to perform this triggering successfully, the StarGate defending the system must be dealt with first. The following cases simulate this:

[31.51] Nova Inducement: In the Basic Game, if the Xenophobe Player has one or more StarForces present in the PSL LiteZulu (hexagon at a given altitude above the surface of the 3D strategic game map, each hex is 1 light-year in diameter) in which the StarGate has been eliminated (neutralized) he may cause the star to go nova in any Combat Segment following the elimination of the StarGate. One Xeno StarForce must be assigned to task of triggering the star, and it must be plotted to break-off in the Combat Segment in which the star is triggered. If it is randomized (by enemy weapons fire) before it can break-off, the star is not triggered. If it successfully breaks-off, the star is triggered and the StarGate is destroyed permanently. Remaining opposing StarForces may remain behind to fight (but the outcome is academic, since the system has been destroyed).

[31.52] Nova Inducement in the Advanced Game: In order to plant the Conversion Trigger in the star, at least one Xeno StarForce must spend an entire Tac- Turn in the star's MiniLiteZulu (3D hexagon on the tactical map. Each minihex is 1/3rd of a light-day in diameter or 0.0009 light-years). It must be in Stellar Mode (as opposed to Battle Mode) and assign half its TelePoints to the task of planting the trigger (which actually is completed in the Position Revelation Phase of that Tac-Turn).

If the Xeno StarForce is disrupted (or randomized) before that time (by hostile weapons fire), the trigger is not considered planted and the star will not go nova. The PSL StarGate must be in a disrupted (or neutralized) state during the planting of the trigger. In the Tac-Turn following the successful planting of the trigger, the Xeno StarForce must Tac-shift out of the MiniLiteZulu containing the star and attempt to execute a break-off maneuver in the Second Execution Phase. The star goes nova during the Combat Cast Segment of the First Execution Phase (After successful planting of the trigger) and any StarForces in the MiniLiteZulu with the star are destroyed in the Results Application Phase. Any remaining StarForces may still contest the LiteZulu but they may not enter the MiniLiteZulu containing the star. The StarGate is not permanently destroyed until the resolution of the Tactical Sequence.


For several thousand years, Green Companion of Antares had been known as a tempestuous stellar bastard, constantly filling all space around it with radiation clouds and fouling up communications. It had several dozen planets which could be very pleasant in the sun were calmed down somewhat, so the Hubley University extension at Antares Vert had been established in 6200 to seek ways of controlling the star. Shortly before the war, they found the first major advance of macro-mechanics, how to blow a star into a nova. It worked as well on stable, main-sequence stars as on the huge, wasteful monsters like Rigel, upon which it was demonstrated. The TOSS now realized that the League could seed their stars through Critter's Universe and blow them all to perdition before anything could be done. Hastily withdrawing their forces from the Gateway, the TOSS began cultivating good feelings with forced urgency.

From THE WARBOTS by Larry Todd (1968)

Orbital Fortress

This section has been moved here

Space Superiority Platform

This section has been moved here

Interdiction Platform

This section has been moved here

Planetary Fortress

This section has been moved here

Deep Down Defenses

This section has been moved here

Surface Defenses

This section has been moved here

Boots On The Ground

This section has been moved here.

Deploying To Planet

This section has been moved here.


This section has been moved here.

Exotic Attacks

This section has been moved here.

Divide and Conquer

This section has been moved here.

Internal schism

This section has been moved here.

Biological Warfare

This section has been moved here.


This section has been moved here.

Von Neumann Machine

This section has been moved here.


This section has been moved here.

Killer SETI

This section has been moved here.


This section has been moved here.

The Web of Hercules

This section has been moved here.

Atomic Rockets notices

This week's featured addition is SPIN POLARIZATION FOR FUSION PROPULSION

This week's featured addition is INsTAR

This week's featured addition is NTR ALTERNATIVES TO LIQUID HYDROGEN

Atomic Rockets

Support Atomic Rockets

Support Atomic Rockets on Patreon