When it comes to weapons, it looks like three main types: beam weapons, kinetic weapons, and missiles. Beam weapons are lasers and particle beams. Kinetic weapons are coilguns, railguns, and shrapnel weapons. Missiles are, well, missiles. Ken Burnside compared it to a policeperson armed with a service revolver, a shotgun, and a police dog. The revolver (beam weapon) cannot be dodged or outrun, but can miss. The shotgun (kinetic weapon) is more likely to hit, but with reduced lethality. The dog (missile) can be dodged or outrun (or shot, that would correspond to point defense), but the blasted thing will chase you, and will always hit unless you actively prevent it.

(Holger Bjerre begs to differ. He points out that kinetic weapons are less likely to hit since it can be dodged, beam weapons lose lethality with range just like shotguns, and kinetic weapons do not lose lethality with range just like revolvers. Well, no analogy is perfect...)

Dave Bryant has his own analysis of spacecraft weaponry here. I'm not sure I agree with all of it, so do your own research.

One of the problems with figuring out how ships are going to fight in space (assuming that we have ships in space, which isn't as likely as I wish; and, that we're still fighting when we get there, which is unfortunately more probable) is that there are a lot of maritime models to choose from.

It's also true that some of the maritime models came from very specialized sets of circumstances; and a few of them weren't particularly good ideas even in their own time.

And it's also true that some of the writers applying the models have a better grasp of the essentials than others. For example, I recall two essays which were originally published about fifty years ago in Astounding.

In the first of the essays ("Space War", Astounding Science-Fiction, Aug 1939), Willy Ley, a very knowledgeable man who had been involved with the German rocket program, proved to my satisfaction that warships in space would carry guns, not missiles, because, over a certain small number of rounds, the weight of a gun and its ammunition was less than the weight of the same number of complete missiles. The essay was illustrated with graphs of pressure curves, and was based on the actual performance of nineteenth-century British rocket artillery ("the rockets' red glare" of Francis Scott Key).

As I say, the essay was perfectly convincing … until I read the paired piece by Malcolm Jameson ("Space War Tactics", Astounding Science-Fiction, Nov 1939).

Jameson's qualifications were relatively meager. Before throat cancer force him to retire, he'd been a United States naval officer -- but he was a mustang, risen from the rank, rather than an officer with the benefit of an Annapolis education. For that matter, Jameson had been a submariner rather than a surface-ship sailor during much of his career. That was a dangerous specialty — certainly as dangerous a career track as any in the peacetime navy -- but it had limited obvious bearing on war in vacuum.

Jameson's advantage was common sense. He pointed out (very gently) that at interplanetary velocities, a target would move something on the order of three miles between the time a gun was fired and the time the projectile reached the end of the barrel.

The rest of Jameson's essay discussed tactics for missile-launching spaceships — which were possible, as the laws of physics proved gun-laying spaceships were not. Ley could have done that math just as easily. It simply hadn't occurred to him to ask the necessary questions.

From Space Dreadnoughts edited by David Drake

"This is a training flight to trans-lunar space with landing at Dianaport. Request permission to pass within five kilometers of you."

"Training flight? Hah!" Omer exclaimed. "Chung has give us an escort!"

"Yes, but why?" I wanted to know. "What's going on dirtside that we should know about?"

Omer shrugged. "Let Chinese escort us. It will discourage more hassle."

If the Chinese cosmolorcha wanted to escort us, there was nothing we could do about it. It was armed. Cis-lunar space is no place to get whanged; it's a long time to anywhere.

"Permission granted, Heavenly Lighting," I replied. "Be advised you are within our zone of damage if we should have a catastrophic failure." The last was pure bluff, but nobody wanted to be near a space vehicle if it catoed, regardless whether it was due to an internal or external cause.

From Manna by Lee Correy (G. Harry Stine) 1983



(ed note: this is a commentary about the computer game Children of a Dead Earth)

I see a lot of misconceptions about space in general, and space warfare in specific, so today I’ll go ahead and debunk some. In the process, we’ll go through the moment to moment of space warfare itself.

Zeroth misconception, no, there won’t be stealth in space, let alone in combat. It is possible through a series of hypothetical technologies or techniques, but it won’t be possible for any reasonable spacecraft under reasonable mass and cost restraints.

Now then, on to the first real misconception. Wouldn’t missiles dominate the battle space, being fired from hundreds of thousands of kilometers away? Wouldn’t actual exchange of projectile weapons never happen in reality?

The answer is no, actually. There is a prevailing hypothesis that missiles will soon be the only relevant weapon on the battle space, and it is likely borne out of current trends in modern warfare. ATGWs are already starting to upend tank warfare, and Anti-ship missiles are doing something similar to naval warfare. Indefinitely extrapolating this trend would lead one to conclude warfare will soon be nothing but people sitting in their spacecrafts launching missiles at one another.

But this is not true. CIWS point defense systems are already starting to shift the balance away from missile strikes. As suggested in an earlier blog post, military strategists are even beginning to suggest the development of CIWS systems may bring naval warfare full circle, all the way back to World War I battleship warfare. This isn’t to suggest that missiles are useless. Indeed, enormous salvos of missiles are effective at overwhelming CIWS systems, and they are in game as well.

Yet we begin to see the limitations of each system. Point defense systems, railguns, coilguns, conventional guns, or even lasers, are power limited in this exchange. There is a finite amount of power to use when firing, except for conventional guns. Conventional guns suffer from low muzzle velocities, and high muzzle velocities are crucial to intercepting missiles coming at you at greater than 1 km/s. This power limitation is what prevents these point defense systems from being impervious to missile salvos. Power consumption is limited by radiator mass actually, as simply slapping down more nuclear reactors is easy, but trying to deal with the added mass of all the radiators needed to cool those reactors is much more difficult.

Missiles, on the other hand, are also limited by mass. A hundred-missile salvo is sure to overwhelm any point defense system, but the amount of mass this requires the launching ship to take on is enormous, and will kill its mass ratio. In the end, it turns out the Rocket Equation governs just how effective missiles and point defense systems are. In game, the systems ended up surprisingly balanced, with neither being a dominant strategy, with either being more effective in certain situations, and weaker in others.

Next misconception, wouldn’t lasers dominate the battle space? Lasers do not suffer from many of the inaccuracy problems that projectile weapons do, and move at the speed of light, so they are literally impossible to dodge. So lasers are the king of the battle space, right?

Wrong. Lasers suffer from diffraction. Badly. The power of lasers in space drops painfully fast with distance, and frequency doubling only ameliorates the issue slightly. Lasers are notoriously low efficiency compared to projectile weapons. But that’s not the main issue. When comparing hypervelocity projectile impact research with laser ablation research, one discovers a stark contrast in their efficacy. Laser ablation is simply less effective at causing damage than projectile impacts. Whereas hypervelocity projectiles cause spallations and cave in armor effectively, laser ablation is poor, with energy wasted to vaporization, radiation, and heat conduction to surrounding armor. On the other hand, at very close ranges, where diffraction is not an issue, lasers outperform projectiles easily. Unfortunately, nothing aside from missiles will likely ever get that close, and even then, they will likely be within close focus ranges for milliseconds at most.

Lasers still useful at long ranges, though. Lasers fill a very specific niche in space warfare, and that is of precision destruction of weakly armored systems at long distances. Lasers are very good at melting down exposed enemy weapons, knocking out their rocket exhaust nozzles, and most importantly, killing drones. While missiles have very few weak points, and can shrug off laser damage with thick plating, drones have exposed weapons and radiators, which makes them very vulnerable to lasers.

In terms of actually destroying enemy capital ships, however, lasers can cut into the enemy bulkhead all day with basically zero effect (I measured the ablation of a monolithic armor plate at one point, and found that the ablation was happening at micrometers per second).

Final, misconception, wouldn’t computers just control everything in combat?

Yes and no, but mostly no. CIWS systems are already computer controlled, and all weapon aiming is similarly already controlled by the computer in game. Anything that has easily computable maxima are solved by computers in game. But there are numerous choices in combat which have no obvious local maxima, and these require human decisions. In other words, you the player and commander need to make these choices. As it turns out, the right or wrong decision can mean the difference between victory and failure.

In game, you won’t be aiming any weapons and firing them, nor will you be flying drones around. The computer can do both better than you, and so the computer will be in control of these things (besides, do you really think you could effectively aim at a speck of light 50 km away moving at 1 km/s at you?).

What you will have control of are the higher level strategic decisions. The orders you give your missiles, drones, and capital ships are crucial decisions you must make in combat. Will you send your missiles in a beeline at your enemy, or perhaps order them to spend valuable delta-v dodging enemy point defense fire? Should you retract your radiators to reduce your heat signature to avoid enemy missiles, and risk the loss of your firepower for the precious few seconds? Should you hold your drones in reserve, close to your carrier, or send them guns blazing as the enemy capital ships approach?

Also as well, one of the critical choices you can make is what to target of the enemy. Each subsystem of every enemy spacecraft is simulated in real time. The reactors draw power, the radiators expel heat, the turrets and guns drain power, all in real time. If you want to disable the enemy’s ability to harm you, the obvious choice is to go for the weapons. But weapons are small, hard to hit unless you have a laser. Going for the enemy’s radiators might be an alternative strategy, with radiators being large, easy targets, although radiators, once armored, are surprisingly sturdy. Not remotely as strong as monolithic armor, but still able to take a reasonable beating of projectile and laser hits. Of course, maybe taking out of the enemy’s engines is more your style, the rocket nozzles being flimsy and poorly armored to allow them to gimbal easier. Plus, a ship that can’t move or dodge is a much easier target.

But most importantly, orbital mechanics are king in Children of a Dead Earth. Indeed, orbital mechanics are the core mechanic of the game, even, counterintuitively, in combat. Once you reach weapon range, orbital mechanics lose most of their relevance, but everything up to that point hinges on orbital mechanics.

Your incoming speed and angle of attack entering combat, two critical attributes which govern how the combat unfolds, are determined entirely by your ability to use orbital mechanics to your advantage. How near or far you are from the nearest gravity well (planet, moon, or asteroid) has a huge effect on combat speeds. Additionally, evading the enemy before even entering combat is a big part of the game. If you can drain the enemy’s delta-v through effective orbital mechanics, they may fight at reduced effectiveness in combat. If you’re good enough, you might be able to run them out of delta-v entirely, and never even have to enter combat at all!


(ed note: again this analysis is centered around the game Children of a Dead Earth. Which, like all simulations, does have some underlying assumptions that may or may not obtain in the real world. It is however internally consistent.)

      Engagement ranges are on the order of tens/hundreds of kilometers, not more, and they are mostly linear
     Weapons are largely ineffective farther away (we'll talk about this in a bit), but since range is a tremendous advantage, no one will survive a prolonged closer encounter. Unless your intercept is retrograde, one side will die before anyone can maneuver appreciably closer or farther.
     The battle space is also mostly linear (two sides facing off across a no-one's-land). A battle "line" is really a 2D plane in space, but aside from this, it's not much different. 2D-thinking (or even 1D thinking!) is quite sufficient.
     Why should this be? While ostensibly space is 3D, when you're flying a real ship, you have delta-v constraints. The space of engagement is large relative to that, and your acceleration is slow to boot (you do have a low-thrust, high-ISP engine, right?). Additionally, since you're probably rendezvousing from a different orbit, you'll have a single dominant direction of approach. You spread out when you attack, sure, but if you're at the distance where you can completely outflank your opponent, you're at a distance where both sides have long since torn gaping holes through each other with k-slugs.

     Maneuvering is almost worthless
     As a direct result of the above, the only purpose for thrusting at all is to dodge k-slugs. You can't do it very well, though, since unpredictably dodging requires rotation—but rotation is slow, and costs lots of delta-v.
     Moreover, to move laterally probably means turning, which means exposing your flank to the enemy. That makes it a bigger target. In CoaDE, this is balanced by the fact that weapons shoot sideways, so to attack, you must make yourself vulnerable. In reality, all weapons just shoot forward.

     On that note, K-slugs are actually great
     A k-slug is essentially a high-velocity bullet. The conventional wisdom on k-slugs is that they don't work in space because your target moves literal kilometers just in the time it takes your bullet to move down the barrel. This is a bit of an exaggeration. If you're rendezvousing with the enemy anyway, the relative velocity is low—probably less than several hundreds of m/s. An ordinary bullet moves a bit faster than this, and a k-slug probably 3-10x as fast again. However, the problem is real.
     The solution is to lead your target. As above, an opponent can't really dodge effectively. But, the inaccuracy of projectile weapons means you're pelting an entire volume with k-slugs anyway, so a bit of jitter from enemy maneuvering is essentially meaningless.
     Note: CoaDE models k-slugs with railguns and coilguns, which I think are probably optimistic/unrealistic (some versions fire >100 / sec, including cooldown). They also make an argument for tracer rounds on every shot, since stealth is meaningless in space. I disagree; tracer pyros are extra mass you need to accelerate, and ballistics computers have essentially no use for visual confirmation of a hit.
     K-slugs are effective at any range, though obviously accuracy decreases as range increases. It's mainly a question of how much mass, in the form of k-slugs, you can afford to have miss.
     Example: a base in a hollowed-out asteroid will be willing to fire k-slugs at any distance. This opens the door to interplanetary-scale bombardment.

     Lasers are basically worthless
     Because of divergence, effective laser power decreases brutally with distance (constant divergence angle ⇒ inverse square falloff). With higher frequencies, you get lower divergence, but unfortunately, higher frequencies are hard to generate and in many ways are less damaging (though that's way beyond scope). Since the engagement envelope is measured in tens/hundreds kilometers, your laser basically needs to be a thousand, a million, or a billion times as powerful, just to do the same amount of damage at range.
     Example: A diffraction-limited 532nm green laser with a 2mm aperture has a minimum beam divergence of 0.085 milliradians. This corresponds to a factor of 23 million billion reduction in flux density over the mere 1.3 light-second distance from Earth to the Moon. So the whole thing about light-speed lag playing a role in laser targeting is garbage, because your city-sized 22-terawatt death-star-laser literally looks like a laser pointer at a distance of 1 light-minute.
     Oh sure, you can do a lot better by increasing the aperture (at inverse square again, but thankfully not scaling with distance). And, in fact, any even remotely practical laser weapons system operates with huge apertures and a lens or mirror to move the beam waist towards the target (all of which are vulnerable themselves)—but you're still going to play a losing battle with diffraction, and CoaDE correctly shows a depressingly abrupt asymptotic drop to zero with distance.
     But the even larger problem is the heat generated. A laser outputs only a tiny portion of its power as coherent light. The rest is dumped as heat, which goes into radiators. To radiate a literal power-plant's worth of thermal energy into space requires several square kilometers of radiator. That makes you a huge, immobile, sitting duck that still can't defend itself because lasers are worthless.
     Example: A space station with an enormous 1 GW ultraviolet laser was disarmed easily, at range, by a lone gun skiff with a 3mm railgun, firing in the general direction of the radiators.
     The point is it's not worth it. Enemies can't dodge anyway, so you might as well use something that actually retains all its destructive power at range and doesn't produce an obscene amount of waste-heat. The only case I've found for lasers is blinding (but again, not really damaging) drones and missiles.

     Whipple shields are stupid; slanted armor is OP
     Slanted armor vastly increases your survivability; this has been known since antiquity. And, when you're going against hypervelocity k-slugs, it's basically your only option. Make it thick enough and slanted enough, and you can shrug off a continuous hailstorm more-or-less indefinitely (at least, if CoaDE is any guide). If the opponent is, stupidly, using lasers, their beam spreads out with the secant of the armor slant angle, to say nothing of the greater Fresnel reflection at angles. Every piece of armor on your ship should be slanted.
     Example: Against an incoming 532nm laser, Aluminum armor has a refractive index of 0.90175. This means that you can actually get total internal reflection. Armor slanted at more than ~64.389 degrees will experience no effect whatsoever from the laser, no matter how powerful!
     (EDIT: this was a miscalculation; I am not aware of a material where TIR losses are practical from vacuum. Secant and Fresnel losses still apply, and so slanting armor is still effective versus lasers.)
     Conversely, whipple shields are useless (a whipple shield is a sacrificial layer of thin armor that shocks k-slugs into plasma, which can then diffuse). One problem, however, is that this theory only works if the projectile is orthogonal to the armor (which would mean your armor isn't slanted). In fact, if your whipple shield is slanted, k-slugs tear huge gashes that quickly render it worthless.
     This is a special case of whipple shields being helpful only once. A whipple shield will block one bullet, but not two. If you have a battle where millions of k-slugs being fired, that's basically no protection at all.

     Missiles ruin everything
     In CoaDE, missiles lock onto the greatest heat source. This makes radiators a vulnerability (although I don't know if occlusion is considered by the game). In CoaDE, this is basically completely countered with flares.
     In real life, missiles won't be anywhere near so dumb. First, countermeasures are not 100% effective. Vietnam-era "Sidewinder" missiles had a kill probability of 18%, which is already terrifying. Modern missiles are around 90%. Pure-infrared systems are imager-based these days, making them basically immune to countermeasures. But these are being phased out—today, we have multispectral guidance systems that are essentially unstoppable, operating on radio, visual, and thermal frequencies. And that's not factoring in literal centuries of technological development before the first space battle of the future. Ships are also much bigger and (as before) less-agile targets than fighter jets.
     But the real difference between a k-slug and a missile isn't payload, but maneuverability. Unlike a ship, missiles have an enormous delta-v budget, and they are cheap and small enough to be nigh-vulnerable to weapons fire. This means they can outflank enemies, shooting them from essentially any direction. In addition to striking the more vulnerable sides of a ship, it makes slewing a point-defense cannon around more difficult. And even if you can disable a missile at distance, its debris is still going to slam into you at several km/s relative velocity. Missiles are massive enough that this is probably a mission-kill anyway.
     Indeed, the ideal tactic is to shoot many small missiles and have them converge from different directions. There is no realistic defense against this. Missiles are even less dodge-able than k-slugs and they're much heavier. Shoot it down with point defense or blind it with lasers, and you still have a gaping hole through your hull. Fail to disable even a single one, and you have a nuclear warhead going off point blank.
     In case you don't believe me, think about reality. Fact: a modern warship (the boat kind) has trouble shooting down a single missile with point defense. If you have dozens of missiles with sci-fi armor, all traveling at quadruple the speed (no air resistance), approaching in three dimensions, and you have maybe 1/10th the armor (mass, delta-v limits) … well, it's just not going to work out very well for you.

     So how should one design a battleship?
     You don't. It's an obvious consequence of missiles: if your battleship can be obliterated by a tiny missile, and there's no real defense against such a thing, you don't build battleships—you build missiles and send them against enemy infrastructure. Obvious secondary effect: War between such factions is attritional, and at most only one major space-based faction survives.
     [Oh, fine. Let's handwave the missile-defense problem for now.]
     The uselessness of maneuverability suggests exposing the smallest possible cross-section to your enemy. For a given mass, this means making your craft long. The slanted armor means making a sharply pointed nosecone, which will also contain all of your armor budget. This will ameliorate the unreasonable effectiveness of k-slugs. Maybe, your entire ship can just be a highly tapered cone.
     All your heat is dumped via a single retractable radiator extending out the ship's rear, and therefore hopefully hidden from enemy weapons' fire.
     Weapon systems have narrow gimbaling, if any, and poke through tiny holes in the forward cone. These are almost-entirely rapid-fire k-slug launchers, of whichever SF-inal technology you please. IIRC IRL railguns have trouble with repeatability, but a few spinal-mount linear accelerators seems plausible. You probably want a few kilowatt-scale lasers to engage incoming drones and missiles, but nothing too fancy. You can place these on the sides, behind your cone-shield, shooting sideways.
     Since missiles can turn, put your missile launchers behind your ship. Each missile splits into hundreds of individually targeted warheads that spread out and then converge on the target at an angle, as described before. Missiles are optimized for delta-v, and consume all of it before impacting. Rocket-powered guided (non-explosive) k-slugs are also an interesting possibility.
     All weapons are optimized for range, since the aggressor who strikes first and longest is the victor.

Engagement Envelopes

Weapon Engagement Zone

Weapon Engagement Zone

In air defense, airspace of defined dimensions within which the responsibility for engagement of air threats normally rests with a particular weapon system. Also called WEZ.

A. Fighter Engagement Zone
In air defense, that airspace of defined dimensions within which the responsibility for engagement of air threats normally rests with fighter aircraft. Also called FEZ.
B. High-Altitude Missile Engagement Zone
In air defense, that airspace of defined dimensions within which the responsibility for engagement of air threats normally rests with high-altitude surface-to-air missiles. Also called HIMEZ.
C. Low-Altitude Missile Engagement Zone
In air defense, that airspace of defined dimensions within which the responsibility for engagement of air threats normally rests with low- to medium-altitude surface-to-air missiles. Also called LOMEZ.
D. Short-Range Air Defense Engagement Zone
In air defense, that airspace of defined dimensions within which the responsibility for engagement of air threats normally rests with short-range air defense weapons. It may be established within a low- or high-altitude missile engagement zone. Also called SHORADEZ.
E. Joint Engagement Zone
In air defense, that airspace of defined dimensions within which multiple air defense systems (surface-to-air missiles and aircraft) are simultaneously employed to engage air threats. Also called JEZ.
Definition of the US Department of Defense military term "weapon engagement zone"
Non-Standard Starship Scuffles

Engagement Envelopes

All battles in space take place at what are, by groundside standards, extremely long ranges, measured in ten-thousands, hundred-thousands, or millions of miles. Not only do these battles take place outside visual “eyeball” range, but even starships in the same formation are outside visual range of each other, being hundreds or thousands of miles apart. (Closer formations would pose both an unacceptably high risk of collision under battle conditions, when ships in the formation are drunkwalking independently, and would be likely to cause point-defense fratricide.)

The only exception to this rule are autonomous kill vehicles (AKVs) themselves (even when not acting as auxiliary kinetic energy weapons (KEWs)), which often come within single-digit mile distances of their targets; i.e., operating effectively inside the innermost point-defense zone.

Outer Envelope: The Wolves at Hunt

The outer engagement envelope begins, depending on various environmental factors, at between one to one-half light-minutes range.

Battles taking place in the outer engagement envelope are essentially always inconclusive. While historical examples of lucky hits from these ranges do exist, the probabilities of such are sufficiently low that no-one would count on them; and at such ranges, it is virtually always possible for the weaker opponent to disengage at will.

(The exception being, of course, when someone has managed to sneak an observation platform in close to the opposing force without them noticing it, which gives them a great – albeit temporary – advantage in generating long-range firing solutions.)

Rather, the purpose of engagements in the outer envelope is to wear down an opponent closing upon one’s inner envelope, forcing them to generate heat and expend point-defense resources; and to herd opponents away from the danger zones generated by one’s fire.

While it is impossible, without both fortunate geometry and superior acceleration, for a single force to bring an opposing force to battle if it is actively trying to refuse such, it is sometimes possible through strategic outer-envelope engagement and misdirection to force them to pass through the inner engagement envelope of one of a set of multiple forces (including, for this purpose, fixed system defenses). This is the end to which tactics are directed in the outer engagement envelope.

At these ranges, the primary weapons are the spinally-mounted mass drivers of larger ship classes. Carriers may attempt to use “missiles” – actually strap-on, discardable thruster packs – to deliver AKVs close in to the opposing force, but many captains prefer to reserve their AKVs for inner-envelope battles where they can be better supported.

Inner Envelope: Let’s Dance

The inner, close-range engagement envelope – in which actual battles are fought – begins at roughly a light-second of separation. This reflects the difficulties of accurately targeting an opponent engaged in active evasion (drunkwalking, ECM, etc.) when the light-lag is greater than that; essentially, you have to close to within a light-second to get a firing solution whose hit probability is significant.

Reaching the inner engagement envelope implies either that one party is attacking or defending a specific fixed installation (such as a planetary orbit, drift-habitat, or stargate), or that both parties have chosen engagement. It is relatively rare for such battles to take place in open space otherwise, since in the absence of clear acceleration superiority, it is usually easy for the weaker party to disengage before entering their opponent’s inner engagement envelope. The only way to guarantee that an opponent will stand and fight is to attack a strategic nexus that they must retain control over.

Within the inner engagement envelope, all weapons come into play. Light lag becomes low enough that information warfare can come into play in full force, firing solutions are usually possible on all craft, and AKVs have the range and maneuverability to be committed.

As the opposing forces enter the inner engagement envelope, larger ship classes typically keep their distance, maintaining formation and lateral drunkwalk evasion, as they engage in mass driver artillery duels.

Cautious admirals also hold their screening forces back at this point, preferring to weaken the enemy force before pressing further. More aggressive admirals press in immediately, moving their lighter squadrons into the center of the battlespace and deploying AKVs likewise.

Unlike the larger ships, cruisers maneuver aggressively for advantage, forming the characteristic “furball” as fleets intermingle; once this stage is reached, it becomes very difficult to retreat in good order. Cruisers attack each other with close-in, off-bore mass driver projectiles and heat-pumping lasers; the highly maneuverable destroyers and frigates engage in “wolf-pack” tactics throughout the battlespace, both targeting each other, and swarming damaged larger ships at relatively close range.

Knife-fight Range

Any battle in which the battlespace is smaller than a tenth of a light-second in diameter is referred to as taking place at “knife-fight” range. Such engagements usually occur around fixed points when the attack is pressed hard, are short and vicious, and typically result in extraordinarily high casualties – usually for both sides.


Unlike starship armor, neither the point-defense laser grid nor the kinetic barriers are subject to direct attrition; if subjected to low-volume or low-power incoming fire, either or both could continue to destroy or repel it essentially forever.

In order to defeat these defensive systems, it is necessary to swamp them; to concentrate incoming fire to the point at which the defensive systems are unable to handle it all simultaneously. At this point, attrition may take effect as kinetic effectors and laser emitters are destroyed, but more importantly, it generates heat.

Heat is the primary limitation on combat endurance. Maneuvering burns, the use of high-energy equipment such as the point-defense grid, the kinetic barriers, and so forth, as well as the ship’s normal operation, all produce heat. In combat – when the ability to radiate heat is limited, usually to radiative striping and small (and exhaustable, if the starship is forced to maneuver) droplet radiators alone – military starships generate heat more rapidly than they can radiate it to space. As heat increases beyond the critical point, the efficiency of onboard equipment begins to fall (processor error rates rise, for example, and tactical officers must conserve their remaining heat capacity), some equipment goes into thermal shutdown, and the crew spaces become increasingly uninhabitable.

While some starships in any major space battle are destroyed physically, reduced to hulks, the majority of starships are defeated by either heat-induced equipment failure, or by being forced to surrender and deploy radiators lest their crew literally cook.

Starship Scuffles: Location, Location, Location…

So, while it now seems to have disappeared from the Internet, my article on Non-Standard Starship Scuffles appears to have come in for some little criticism:

First, for having FTL in it; and

Second, for assuming that space battles will take place in open space, the commenter apparently not seeing any reason why they would ever take place except right next to whatever strategic nexus point they’re fighting over.

To a degree, on both points, I’m inclined to question the reading that gave rise to those comments because on the first, well, while there is mention of FTL communications with observation platforms to improve one’s longscan for tactical advantage, the ships themselves don’t – can’t – move at FTL speeds, and indeed, the entire rest of the article would be exactly the same if there were no such thing as a tangle channel.

On the latter, though, I first note this:

Reaching the inner engagement envelope implies either that one party is attacking or defending a specific fixed installation (such as a planetary orbit, drift-habitat, or stargate), or that both parties have chosen engagement. It is relatively rare for such battles to take place in open space otherwise, since in the absence of clear acceleration superiority, it is usually easy for the weaker party to disengage before entering their opponent’s inner engagement envelope. The only way to guarantee that an opponent will stand and fight is to attack a strategic nexus that they must retain control over.

…but let’s ignore that for a moment. Here’s why starship battles, whenever possible, are conducted in open space despite this, and why the inconclusive engagement-avoidance-and-retreat is also more common than the aforementioned at-nexus-point battle.

Because in space, a weapon once fired continues on until it hits something. Hopefully that’s its target. If it isn’t its target. hopefully it’s a clean-up fluffship, or something big and ugly enough not to care (like the star), or some Oort cloud object no-one cares about.

But the bigger the solid angle subtended by an object from the point of view of the fighting starships, obviously, the greater the chance that it’s going to be shot right in the face by misses, not to mention ricochets and debris. And the closer you are to an object, the greater the solid angle it subtends, by the inexorable laws of geometry.

This is why the defender has a strong preference for going out to meet the attacker, because letting what you are trying to defend get all shot up as a side effect of the process of defending it generally makes defending it in the first place somewhat moot.

This is also why many attackers have a preference for luring the defender out to meet them: because firstly, Omnicidal Maniacs aside, you may want to capture some of those defensible assets reasonably intact and avoid any unnecessary effusion of blood; and secondly, because being casual about smacking relatively fragile civilian habitats and inhabited planets in the backdrop with starship-class weapons is the sort of thing that leads to bad press, unwanted reputations, and awkward interviews in front of war crimes tribunals.

All of which is to say: naval strategists have a term for admirals who plan their defensive engagements at point-blank range rather than maintaining a healthy strategic depth. That term is idiot.

Weapon Mounts

As a general rule, a space warship is basically a "weapons platform." It is just a way to move some weapons that you control into a strategic position in order to rain death and destruction upon enemy military assets. On a warship, the group of weapon mounts that the warship is designed around is called the main battery. In other words, the main battery is the weapons that the warship is the platform for.

Weapons are mounted on what they call "hardpoints", "weapon stations", or "static mounts." These are positions on the spacecraft's hull that are designed to carry the mass of the weapon. Analogy: if you are pounding a nail into the wall in order to hang a heavy picture, you pound it into a wall stud, not just the fragile drywall. For the same reason only mount a heavy turret on a hardpoint embedded in the ship's skeleton, not on a flimsy stretch of hull. Otherwise the hull will tear and the weapon will fall off, some hulls are about as strong as a beer can.

Some weapons cannot be mounted on the hull of the spacecraft, for whatever reason they have to be on a small tower called a Pylon. These are generally only found on aircraft, where mounting a missile or bomb directly on the wings will screw up the aerodynamics. But they may be found on weird spacecraft: such as ships streamlined for the interstellar medium (bussard ramjets) or technobabble faster-than-light starships with technobabble fins or something to create FTL or fin-shapes that generate a force field or have wing-shaped reactionless thrusters or whatever the science fiction author thinks is classy sci-fi baffle-gab.

Sea-going warships had a numbering system for turrets. This was simplistic since it was designed for vessel with a basic two-dimensional layout. Adapting this to a three-dimensional spacegoing warship is a bit of a challenge.

Mount Types


Racks are simplistic hardpoints for weapons you do not have to aim much, typically expendable weapons. Meaning homing missiles and bombs. Technically racks are fixed mounts. They will need some sort of data channel to the ship, so the crew can control the weapons.

Homing missiles are often mounted in "vertical launch systems" or "missile cells", because they do not have to be aimed. Fire and forget, they'll automatically find the target. The missile will jet up in the air a few meters, rotate until it is aimed at the target, then streak to the target on a plume of fire.

Bombs do not have to be aimed much because typically your target is something huge, e.g., a planet or a city. Except for precision bombing.

In addition to missiles and bombs, you can attach to a rack something called a Gun Pod. This is a self-contained detachable modular pod containing one or more weapons, ammunition, and if necessary, a power source. Everything it needs to spit death at hostile ships. Some pods use power from the spacecraft, these require racks with power connection to the ship.

Gun pods are used when mass is an issue, because if the mission does not require weapons the pod can be omitted to increase the spacecraft's payload allowance. They also increase the armaments without consuming internal volume (though this is more of an issue with aircraft than it is with spacecraft). Different types of gun pods also allow a spacecraft to customize its weapons loadout to match a given mission. Snap off the old pod and snap on a ship-killer pod for a knife-fighting range ship duel. Snap off the old pod and snap on a point-defense pod if the mission involves running the gauntlet of hostile missile-fire.

Obviously since a rack is a fixed mount, the spacecraft will have to aim the gun pod by aiming the entire spacecraft. In the real world, gun pods that fire shells or bullets suffer from reduced accuracy. The recoil from the bullets tends to twist the gun pod away from the centerline, unlike bullets fired from a weapon that is integral to the aircraft's skeleton.

If you combine a gun pod with a missile cell you get a rocket pod.

Rotating Mounts

With this type of mount, weapons are contained in rotating platforms which pivot to allow aiming. Unlike broadsides and spinal mounts, rotating mounts have a very wide traverse and elevation.

If the rotating mount is attached to the outside of the ship's armor, it is an Installation.

If the rotating mount penetrates the armor it is called a Barbette. In science fiction, sometimes you see a rotating mount that is concealed under the armor but the armor can open up and allow the barbette to deploy. These are called jack-in-the-box barbettes, because of the resemblance to the child's toy.

Do not confuse this with the Jack-in-the-box effect. That is when hostile weapons fire penetrates a ship's armor and explodes inside a weapons magazine or other large concentration of ammunition. The ammo is detonated, the ship's armor catastrophically inflates like a balloon, and all the turrets jump off the hull like a jack-in-the-boxes from hell.

If the rotating mount penetrates the armor and has protective armor encasing the weapon, it is called a Turret. Historically they were first called "hooded barbettes" but the name never caught on.

Apparently there is no term for a turret where the mount does not penetrate the armor, because that is a stupid thing to do. Offhand I think that would be the equivalent of a gun pod with a rotating mount, which would waste a lot of internal pod space on rotating motors.

Some rotating mounts contain two or more weapons arranged parallel. These are called coaxial mounts (although that is a misnomer, used because "paraxial mount" does not go trippingly off the tongue). Obviously all the weapons in the mount fire in the same direction. In the real world you find this often with armored fighting vehicles, with a machine gun mounted coaxial to the main gun. The gunner aims both with the rotating mount, firing the main gun at hard target and the machine gun at soft target.

Sometimes rotating mounts that may have to fire in the same direction are set at different altitudes from the hull, this is called Superfiring. In the real world this is generally found in battleships.

A small turret mounted on top of a turret is called a cupola. A tiny turret mounted on top of a cupola is called a finial.

Conventional turrets rotate to traverse as all turrents do, but elevate by having the gun protrude through a vertical slot and rotate on the gun's trunnion. The gun elevates and depresses but the turret body does not. Since the gun's barrel only covers part of the turret slot, the rest of the slot is wide open for hostile weapons fire. The slot is protected by a mantlet attached to barrel where the gun emerges from the turret. Otherwise enemy fire could enter the open slot, bounce around inside the turret while killing the crew, and maybe even detonating the shell currently loaded in the main gun.

More advanced turrets are Oscillating turrets where the turret is in two parts. The lower turret part rotates, and the upper turret part (and the gun) elevates and depresses. In this case the trunnion is on the upper turret half, not on the gun. The gun protrudes out a circular hole instead of a vertical slot, since unlike the conventional turret the gun does not move relative to the upper turret body.

The three advantages of oscillating turrets are high gun placement, smaller turret size and simpler fitment of an autoloader. All three advantages are because the gun is fixed inside the turret, instead of rotating on a trunnion. I note a fourth advantage: a mantlet is not required.

Having said that, oscillating turrets have rarely been used in historical main battle tank designs.


The Turret

Definition:  A weapon or weapons mounted on or in an articulation that provides extreme ranges of traverse and elevation, as well as commonly housing the firing/loading mechanism and gun crew.

   The turret is one of the most common styles of weapon mounting in SF, and for good reason.  Nearly all wet navy guns are mounted in turrets, as are point defence weapons, and the main gun of tanks.  It was the invention and adoption of turreted main guns, along with the invention of the steam engine, that changed the face of ocean warfare forever.  A spacecraft armed with turrets can bring more of its weapons to bare on any enemy craft, and can do so regardless of its heading.  This is obviously important in a battle involving many spacecraft in close proximity, especially those capable of fairly pronounced manoeuvres and high acceleration.  Point defence weapons are far far more effective will a turret mount than without, allowing them to track incoming.

   There are two common mistakes with the representation of turrets in SF.  The first is the idea of a turret as a bolt on unit.  While this may be the case for smaller point defence units, it is almost never true of larger weapons.  Even the small gun turrets wet navy ships still use extend below the deck level, and old battleship turrets had more concealed than exposed.  The second issue is when turrets are placed in a position where the firing arc is limited by other turrets or by the hull of the spacecraft.  While the latter is to an extent unavoidable the former defeats the purpose of having a turret to begin with.  Yes, I'm looking at you Star Wars.

   Disadvantages of the turret are simple.  For any given weapon a turret to carry it will add complexity, mass, and power requirements to the design of the combat spacecraft, reducing the overall number that can be carried and increasing the cost.  Reduced accuracy can also be a problem due to vibration from the traverse motors, increased vibration in the flexible bearings, and flex in a unsupported barrel.  There amy also be a limit to the ammo that can fit in the turret, decreasing the overall firing rate.  Unique to spacecraft is the problem that recoil forces imparted on the spacecraft are not going to be constant, and will thus be harder to account for as they impact the trajectory of the whole craft.  

   Fundamentally turrets have a single advantage; they can be aimed independently of the spacecraft's orientation.  All the other advantages - reduction in number of guns needed to provide coverage in terms of point defence, ability to engage multiple targets in different directions etc are all derived from the former.  The advantage is most pronounced with point defence weapons, as they will face threats from many angles, and need to be able to track fast and close targets.

   Kinetic weapons are ideal for turrets given that unguided kinetics have short ranges, and it is in this envelope that turrets offer the biggest advantage.  Lasers also have a lot going for them.  Since the laser itself is likely to be in the main hull rather than the turret itself, with the beam reflected through a series of mirrors, there can actually be more turrets than the spacecraft can generate laser light for.  Whichever turrets are needed have laser directed into them, and the loss of a few to enemy fire is not such a disadvantage since the total energy output does not decrease.  Particle beams benefit the least.  This is both due tho their long skinny shape in most designs, and to the fact that bending a particle beam at any kind of angle will produce synchrotron radiation.  Tis could of course be overcome by having truely massive turrets or miniaturised particle beams.  In terms of point defence lasers are likely to be dominant given their accuracy at range, and the fact that a missile probably won't be too well armoured compared to a spacecraft.  Adaptive optics can also give point defence turrets quicker focusing and greater accuracy.  Kinetic point defence will be regulated to slower firing 'flak guns' that throw up a wall of shrapnel rather than targeting individual threats.

   Unlike broadside and spinal mounts turrets have the best chance of dominance in a softer SF 'Verse.  This is because they are best suited to short ranged, high relative speed combat where aim will have to be shifted quickly, and the spacecraft will be changing direction often.  They are also suited to battles where enemy spacecraft can emerge unexpectedly from hyperspace in any direction, and in which the spacecraft of both sides end up occupying the same volume of space.  Obviously force fields or shields help in this regard as they encourage ships to close to kinetic range where they can output more damage.  In a hard science 'Verse close quarters battles are unlikely as everyone will be seen long before they get into range, and with the ranges that are more realistic decrease the disadvantage of fixed weapons and emphasise range and accuracy.  Turrets will always be used as point defence installations however, so they will never be absent.  A lot of works also feature turret mounted kinetic guns as secondary weapons, like the Sulaco from Aliens; this is quite likly considering the relatively small size that kinetic weapons can have while remaining potent enough to be included.


Each individual PDC is a little smart robot. I love the scene in S1E4 where Alex is fumbling his first Roci(nante) flight and slams into a bulkhead in the Donnager bay. The PDC on that side ducks into it's housing to avoid damage just before he hits.

(ed note: The point-defense-cannons (PDCs) are mounted on jack-in-the-box barbettes. Described incident is from the scene above)

tweet by James S. A. Corey {Daniel Abraham and Ty Franck} (2020)

A point defense cannon (PDC) is a rapid-fire projectile weapon used by all military-grade spaceships for defense against small ships and missiles.


PDCs are turreted rotary autocannons, utilizing a set of six spinning barrels to spew out thousands of rounds per minute to intercept incoming ordnance. PDCs are laid out on a ship's hull to cover all angles with overlapping fields of fire, providing a "curtain of steel" to more easily and effectively take out missiles. They also utilize thrusters on their rear to counteract the recoil of the firing cannon, that would otherwise knock the ship off course.

PDCs are computer-controlled, as even juiced-up human gunners would find it nearly impossible to effectively track and destroy fast targets like torpedoes. Human gunners do, however, select targets for the guns. The cannon turrets can also be retracted into the hull and can extend outwards in mere seconds.

PDCs are mainly used against guided ordinance, but they also perform fairly well as close range ship-to-ship weapons and can be used for direct space-to-surface strikes on personnel. The rounds seem able to penetrate the armor on most smaller ships.


PDCs were first seen in use on the MCRN Donnager, which used her numerous PDCs to shoot down a hail of plasma torpedoes launched by an attacking squadron of six Amun-Ra-class stealth frigates. While most of the torpedoes were shot down, the advanced guidance systems of the torpedoes, as well as their sheer numbers, allowed two to get through and damage the Donnager's reactor. In the ensuing CQB battle, the Donnager used focused fire from her PDCs to destroy at least one assailant. As the Tachi (later to be renamed Rocinante) escaped the Donnager's hangar bay under a hail of small arms fire, it returned fire with its PDCs to wipe out many of the soldiers that had boarded the Donnager and blow open the hangar door, allowing the ship to escape.

At the assault on Thoth Station, the Rocinante's PDCs were used to intercept torpedoes, destroy an anti-asteroid cannon on the station, and even take out the far better-equipped stealth ship by riddling it with thousands of rounds at point blank range. The enemy also used their PDCs to disable one of the Rocinante's port-side thrusters, hampering her maneuverability during the battle until Amos repaired the damage.

During the sudden and unexpected Ganymede Incident, due to the close proximity and chaos of the incident, PDCs were used as the main weapon by MCRN and UNN ships engaging in combat in Ganymede's orbit, destroying ships on both sides as well as several orbital structures, resulting in a cloud of debris falling to Ganymede's surface and the loss of thousands of military personnel.

During the Io Campaign, the UNN Agatha King used its PDCs to destroy several volleys of torpedoes fired at it by UNN ships loyal to Admiral Souther in retaliation for Nyugen personally carrying out the destruction of the UNN Jimenez. Later when the Hybrid pods were launched en mass towards Mars from the surface of Io, the Rocinante and all the UNN and MCRN ships in the area opened fire on the pods with their PDCs attempting to shoot them down with the Agatha King being the only ship not to engage them. However, many pods were able to escape unharmed due to their stealth tech and sheer numbers. MCRN Hammurabi's PDCs struck one of the pods before its drive could engage, resulting in the pod crashing into the Agatha King, leading the ship and her crew to becoming infected by the Protomolecule.

When the Nauvoo was recovered, Johnson had it renamed the OPAS Behemoth. In addition to attaching several missile pods and railgun turrets, an incredible 170 PDCs were mounted to the ship's 2km hulk, giving it impenetrable defensive coverage to compensate for the ship's enormous target profile and poor acceleration.


  • PDC rounds are repeatedly described as "Teflon-coated tungsten". While not explained in detail in the books, this fact could make PDC rounds "armor-piercing sub-calibre ammunition;" a long narrow tungsten arrow acting as an armor breaking component, surrounded with light teflon-edged sabot, providing maximum barrel exit velocity.
    • The teflon does not affect the ballistics of the round used, but rather allows for harder armor-piercing materials like tungsten to be used without excess barrel wear, as the teflon lubricates the bullet, allowing it to better engage the barrel without grinding it down. This would be a valuable trait to be found in autocannon ammunition, as with the very high rate of fire, harder AP ammunition would wear down the barrels quickly.
  • In the book, unguided weapons like the PDC and railgun, are described as being viable only with ranges of less than 1000km. Given that PDC rounds are far slower than rail gun slugs, their effective range thus is presumably much shorter than even that. Based on the length of ships like the Donnager compared to the visual range at which PDCs are used, this effective range seems to be between 1-5 km.
The Expanse Wiki entry for PDC

Broadside Mounts

These are typically set into the hull aimed at 90° to the thrust axis, with little or no traverse and elevation. Just like a the broadside of a 16th century Man of War sailing ship.

Broadside mounts that can traverse but cannot do elevation are called Casemates. It looks like a vertical cylinder with a gun sticking out of the side.

Just to confuse things, in historical armored fighting vehicles a tank with a casemate is more like a spinal mount. In other words it is a tank build around a huge tank-killing main gun that you have to aim by turning the entire blasted tank. I only mention this so you are not confused if you encounter it in your research.


The Broadside

Definition:  Weapons mounted at right angles to the direction of thrust, usually within the main hull of the spacecraft, and with limited traverse and elevation. 

   A fixed broadside battery is one of the most uncommon arrangements to be seen in SF, with turrets being far more common.  The only one that I can think of in visual SF is the gun deck aboard the Separatist ship at the beginning of Revenge of the Sith.  In written works the Black Fleet Trilogy by Joshua Dalzelle had what sounded like a fixed battery of laser weapons on the ship that acts as the setting for most of the first book, but it was never implicitly stated.  In the Honor Harrington books the beam weapons were, by memory, in broadside arrangement; a necessity imposed by the gravity drives used.  There are also the quite common examples in visual media where turrets are shown that would be unable to fire in any arc except that of a broadside.  Most of the turreted guns seen in the Star Wars movies fall into this category, with the Venator Class being a prime example.

   The scarcity of this arrangement is not unexpected.  With the prevalence of the 'Space is a Ocean' trope it is to be expected that a design philosophy that long ago gave way to turret armament should find little traction.  Where it is found it is most often for the visual effect, or because the work is intentionally trying to mimic the battles of the Napoleonic War transposed into space.

   There are not so many advantages to this type of design, and the conditions under which it become practicable are quite specific.  The main advantages are those shared by any fixed weapon mount.  Each weapon will mass less than an equivalent turret, and be simpler in construction.  It may be more accurate since it can be mounts straight to the spacecraft's structure via recoil absorbing mechanisms, reducing vibration.  Ease of access would also be a big factor, especially with advanced and perhaps temperamental weapons since turrets have never been known as spacious.  The weapon itself might also be more massive than a turret could cope with, or have a larger recoil force.

   Disadvantages are pretty obvious.  Limited traverse and elevation impose a greater need for manoeuvrability on the spacecraft, and run the risk that at close range or high traverse speed a more manoeuvrable target could stay out of the fire arc entirely.  This is partially avoided with lasers, since with adaptive optics they can have quite a good arc of fire without the actual emitter being articulated.  Since they cannot fire forward the spacecraft is at a disadvantage accelerating toward or away from a target, although this may not be a problem depending on the technology level of the 'Verse.  The broadside, and all fixed weapons, are at a disadvantage in a 'Verse where FTL can allow a enemy spacecraft to appear unexpectedly in any direction.  The need to rotate the entire spacecraft is going to slow down response times significantly compared to a turreted vessel.  Conversely the broadside is more attractive in a hard science 'Verse where you will always see the enemy coming.

   A broadside thus falls best into a 'Verse with fairly low accelerations and long engagement ranges.  It also becomes a lot more practical if the main offensive weapon is a missile attack from standoff range, especially if it is one involving tens or hundreds of missiles, and possible submunitions.  The ability to carry more weapons for the same mass than in turrets, coupled with the greater accuracy and potentially greater effective range would give the broadside ship a very good defence against missile spam attacks.  Against such an attack it is the volume, range, and accuracy of defensive fire that will stop your spacecraft from being ventilated by a hypervelocity penetrator, and in this regard the broadside holds the advantage.  Also, the greater the number of weapons, the more incoming can be targeted at once.

   Lasers or kinetic weapons would be the most practical.  Lasers would benefit from having many emitters, allowing more incoming to be targeted at once, and for kinetics it allows a greater overall rate of fire, important given their inaccuracy.  With kinetics it could also extend their offensive range by filling more space with metal than would be possible with fewer weapons and making it difficult to evade with low thrust levels; range would still be terrible compared to other weapons however.   Charged particle beams could interfere with each other, but a neutral beam wouldn't ave that issue.  The soft-kill ability of a particle beam might also prove handy against missile attacks; the beams could even be defocused to fill a huge volume of space with relativistic plasma, providing a potent radiation hazard for any incoming missiles.  But without exact numbers it seems impossible to give any of the three weapon types a clear advantage for broadside use; it depends doll on the details of the setting.

   Some of you might object to the idea that lasers are better with many emitters, and it is a common debate.  Do you use one emitter with longer range, or many smaller?  My reasoning is that in a 'Verse where missiles are a viable main offensive weapon they will broadly be able to fire enough missiles with enough submunitions that the extra range is not such a great advantage, more so since a accelerating missile at a half a light second or so is going to be phenomenally hard to hit, and could be travelling at a huge speed by that time.  In any case, a computer controlled array of smaller emitters can act as a single larger emitter to some extent, in the same way as many modern telescopes use mirrors composed of multiple segments.

   Although not strictly a 'broadside' a missile armed spacecraft might have its storage silos arranged in the same configuration to allow more rapid deployment.  With warfare based on missile spam the ability to unleash more missiles in less time might be the best chance at victory, and having the equivalent of a current VLS(Vertical Launch System) might be the ideal.  This could also look pretty cool visually while maintaining realism, so take notice Hollywood!

Spinal Mounts

Naturally some people who are into hyper-optimization and minmaxing will quickly switch from mounting weapons on a ship, to building the ship around a weapon. You are not strapping the gun to the ship, you are strapping the ship to the gun: the ship is an ACCESSORY.

A monstrously huge weapon, with a fixed forward facing. It has little or no traverse and elevation because it is a fixed mount.

Of course you will have to turn the entire freaking spacecraft in order to aim the weapon, but the ship is going to smite the target with the most bang for your warship dollar. The ship will also have a similar outline as the weapon, probably long and skinny. This is a problem since long and skinny ships have a large moment of inertia, meaning it will be slow and difficult to rotate the ship while aiming. William Moran suggests that a spinal mount ship has many of the advantages and disadvantages of long-range artillery: they are slow to move and slow to aim but they can utterly obliterate a target at extreme ranges.

It certainly will be the sort of ship that will blast the snot out of you if you are stupid enough to turn around and try running away. Popular spinal mount weapons are coil guns, rail guns, and particle beam weapons, since those weapons inflict more damage the longer the weapon barrel is.

The weapon can be mounted on the ship's nose, along the ship's side ("dorsally" or "ventrally", but RocketCat will rip your lips off if you use those terms, more acceptable is "keel mount"), or along the ship's spine.

You can also be annoyingly clever and spinal mount a weapon that is also a propulsion system. This means the weapon fires to the rear, to give any hostile behind you a quick dose of the Kzinti Lesson. Mass driver propulsion is a good fit here.

In extreme cases the weapon is the ship's spine, this is what the Traveller RPG calls a "spinal mount". A good example is the "Wave motion gun" that forms the spine of Space Battleship Yamato. In the real world the A-10 Warthog ground-attack aircraft is pretty much built around its 30 mm GAU-8/A Avenger Gatling-type cannon. And Matthew Marden pointed out to me that in 1890 the USS Vesuvius was virtually a spinal mount, with "dynamite guns" fixed in both traverse and elevation.

Just to be clever, the Traveller RPG postulated a "Janus mount." This is two half-length spinal weapons installed in a single spinal tunnel, one facing fore, one to aft. In reality there would be no reason preventing two full-length spinal weapons installed side-by-side in the spinal tunnel.


The Spinal Mount

Definition: A weapon firing in a fixed forward arc, parallel to the direction of thrust, with limited elevation or traverse, and typically running through a significant portion of the spacecraft's length.

   Spinal or Keel mounted weapons are interesting because, unlike turrets or fixed weapons, they have no current real-world counterpart aside from fighter aircraft.  The sea going battleships that provide inspiration for many SF works used broadsides during the age of sail, and turrets in the era of Big Gun battleships, but a single forward firing weapon has never been used to my knowledge aside from a few submarines like the Surcouf, and that was neither common nor in line with the spinal mounts of SF.  If anything their closest analogy is the main gun of a turretless tank hunter.  Even that is a poor comparison given the role stealth plays in tank warfare, and the degree to which it is impossible in space.

   The rational behind the Spinal Mount is straightforward and pretty logical; the bigger the gun the better, right?  Most 'guns' in SF are in fact accelerators of some kind; railguns, coil-guns or gauss cannon, ram accelerators, and particle beams.  What this means is that muzzle velocity scales directly with the length of the weapon, rather than their being a optimum barrel length as there is with conventional firearms.  There are engineering limits, or those imposed by material science, but the highest theoretical velocity is as close to the speed of light as you can get.  A Spinal mount also translates the power of the weapon to the audience quite easily, especially when coupled with long recharge times and/or cool down.  The MAC guns of HALO and the Wave Motion Cannon of Space Battleship Yamato are pretty typical of this trope.

   There are a few disadvantages with the spinal mount, most of which revolve around the fact that the spacecraft must manoeuvre to aim the weapon.  Even if the finer adjustments are done internally rather than by the spacecraft's alignment it will still limit the speed that the spacecraft can edge widely separated targets.  It also means that if a enemy emerged unexpectedly from hyperspace the spinal mount might not have time to be oriented before it is destroyed.  Most spacecraft armed in this way are shown with only one main gun, with is a disadvantage if it breaks down or is disabled by enemy fire.  The spinal mount might well be a glass cannon, extremely dangerous, but needing other ships to contribute to its defence, especially if under attack by multiple enemy.

   While the time needed to aim, and the disadvantage of only being able to engage targets in the same direction at once are inescapable the problem of manoeuvrability may not be an issue.  A spacecraft equipped with a powerful gauss cannon, railgun, particle beam, or laser, will have plentiful electric power.  This can be used to power multiple thrusters distributed all over the spacecraft, rather than having them clumped together, and allowing acceleration in any direction.  With many fictional spacecraft the main drives are to large, expensive, or radioactive to allow this, but for more realistic low accelerations electrothermal or plasma based drives may do fine.

   The advantages are many.  A spacecraft can fit a larger spinal weapon than it could hope to fit into a turret, something likely to hold true for any size of spacecraft.  This is partially due to the fact that a turret has to turn, and so has limits on the mass and size of the weapon, and partially to the fact that recoil forces along the line of thrust can be absorbed by the thrust structure instead of by a complicated system of articulation.  This can also make the weapon more accurate as it will not have to cope with the vibration of turret articulation, or the fox in a unsupported barrel.  Greater muzzle velocity has the advantage of imparting a longer effective range on particle beam and kinetic weapons, helping to negate their inherent weakness.  Even if the energy they output is the same as a physically smaller weapon, the increased range will make them more effective at ranged combat, something there is likely to be a lot of in space.  And they do not need the cool down time shown in SF.  The most powerful might, but it should not be a surprise to find MAC gun like weapon with rapid fire capabilities. 

   Kinetic weapons benefit the most from a spinal mount as opposed to a turret or broadside since it helps to overcome their greatest weakness - low velocity.  Particle beams may also be common in this role since the long skinny shape of a particle accelerator fits the bill nicely.  Lasers on the other hand do not seem to be a good candidate.  Lasers do not benefit from having a longer physical shape, it is the diameter of the emitter that counts.  While there is an analogue — a spacecraft with a single massive mirror at the front — it has its own advantages and disadvantages, and does not really fit the description of a classic spinal mount.  Operationally it would be employed the same however, and have the advantage in rage over smaller turreted counterparts.

   It is this range benefit coupled with the low turning rate that define the use of spinal weapons.  They are the long ranged artillery of space.  If they can maintain range from the enemy the extra range might make them well right invulnerable, while if used in a defensive role that extra reach will fore the enemy to run a gauntlet of fire.  A battle between two of these spacecraft would be like a sniper duel — few tactics, with the one with the greatest accuracy coming out on top.  They would be at a disadvantage in any battle where there are multiple vectors of attack, or one that starts at close range. In a battlefield dominated by missiles they might not fare to well, but one that focuses on direct fire is likely to see them.

   The 'Verse that features spinal weapon can fall anywhere on the spectrum of scientific realism.  Given their long range and potential firepower it seems likely that any space force will have some in its ranks, and that they will form an important part of tactical doctrine.  One thing to note is that they become less attractive as the number and acceleration of ships increases as this brings out their weakness.  A jump drive that allows enemy to 'slip under the guns' as it were will also compromise them.  In any battle where missiles are unviable, massive firepower is needed from smaller ships, or the enemy will be engaged at extreme range a spinal mount is justified.  Another thing to remember is that a magnetic accelerator could be developed as a civilian cargo launcher on the moon, and repurposed as a weapon during a war, similar to in Heinlein's The Moon is a Harsh Mistress.  Even particle beams or lasers that fit the design requirements might be developed as part of beamed power stations.


Something I've observed about spinal or keel mounts: if you're capable of forward-plotting your target's motion, relative to yourself, and capable of doing interesting heading changes relative to the changing bearing, spinal mounts are much easier to use than most settings give them credit for.

The task is straightforward enough to do manually at a game table. I imagine it would be automated in any real combat environment.

Note that "interesting heading changes" might not be a universal assumption, depending on ship mass, moment arm calculations, weapon range and operational theater. Low orbits can result in targets that pop up into visibility with the maneuver by the target reported only be remote (or ground based) sensors.

From Ken Burnside (2017)

Firing Arcs

People who have played Star Trek and Star Wars wargames are familiar with the concept of "firing arcs". There are a limited number of direction a given ship-mounted weapon can aim, if nothing else the ship's hull will block off about half the sky. It is generally considered to be a design flaw if a ship's own weapons accidentally shoot off part of the ship protruding into the firing arc. Shooting yourself in the foot as it were.

Different weapons can have different firing arcs, depending upon where on the ship they are sited.

So a combat warship has to maneuver in such a manner to maximize the number of all your firing arcs the enemy is occupying while simultaneously minimizing the number of enemy firing arcs you are occupying. In wet naval warfare, the classic maneuver is Crossing the T. The skillful task force doing the crossing can fire all the broadsides that face the enemy. The unskillful task force can only return fire with the couple of guns each ship has that can fire forwards.

But the battle starts even earlier, as the warship designers try to site the weapon mounts in the most advantageous locations on the ship blueprints.


There's an interesting question of what the ideal number of turrets is. One thing that's counterintuitive is that the number of turrets has little effect on total firepower. Your laser engine(s) can fire the beam down a central corridor, with mirrors to select a branch toward any of the laser turrets. No matter how many turrets you have, you can concentrate all laser firepower through one turret. (Rick Robinson calls this a "Laserstar")

I tend to favor two turrets on opposite sides. Besides providing all around coverage and some redundancy, it also allows use of a "hunter-killer" tactic. While one turret fires the laser to kill a target, the other turret can be scanning to "hunt" for the next target. This allows a near instantaneous switch from one target to the next, minimizing down time for the laser engine.

More importantly, this has a big tactical effect on the enemy's options. Suppose each of your ships only had one laser turret, and the enemy knows this. Then the enemy knows it takes some time for you to switch from the current targets to new targets. If the enemy notices that all of your ships are firing on particular targets, he can take advantage of this to open up sensitive sensors or radiators onboard the non-targeted ships. He knows that if you want to fire on a different target, he's got enough time to close protective "shutters". In contrast, with two turrets per ship nowhere is safe from being targeted.

This depends on the type of laser, of course. With typical IR-UV wavelength lasers, the availability of efficient mirrors generally makes this a compelling option. You only need one or two turrets for full coverage (or practically full coverage), but you might still include more turrets for redundancy and/or "hunter-killer" tactics (one turret hunts for the next target while the current turret kills the current target).

Other types of laser work differently. In particular, an X-ray free electron laser requires pointing the entire ship at the target - particularly if a widely spaced zone plate is used to focus it (the zone plate may be light seconds away, placed between the beam generating ship and the target).

And yet, even in that case the electron beam accelerator might be multi-purpose. The electron beam can be diverted to turreted wigglers for short range lasers, and the electron beam might even be used directly for various purposes. In particular, the electron beam could be used for ablative propulsion of dumb defensive drones (just dumb rocks vaguely near the ship), as well as ablative propulsion for the ship itself.

I'd say a "spinal mount" is fixed with respect to the long axis of a spacecraft, but the main direction of thrust could be some other direction. In fact, it makes more sense for the direction of thrust to be sideways to the long axis of a warship, or for the main thrusters to be turreted.

It generally makes sense to try and present a narrow profile to the enemy. This may actually be generally impossible when the enemy has more than one warship, so the ideal shape might actually be a reversed cone (a teardrop shape). But when you need a kilometer long X-ray wiggler, such a compact shape may be out of the question.

If you are pointing toward the enemy, having main thrusters pointing directly away from the enemy basically eliminates all maneuver capability. You have one degree of freedom, along a direction which is entirely dependent upon the enemy's maneuvers. Basically, you give up both maneuver capability and forward planning capability.

But having main thrusters pointed "broadside" gives you two degrees of freedom, and gives you the flexibility to maneuver freely perpendicular to the enemy. Even better is if the main thrusters can rotate a bit in one dimension. That basically gives you complete flexibility to thrust in practically any direction regardless of the enemy's maneuvers.

That's assuming you have something that looks like traditional thrusters. If your main thrust comes from pulsed ablation/spallation of the ship's main armor/hull, things may look very different anyway.

Isaac Kuo

This week, we’re going to have a bit of fun. We’re going to take a look at a science fiction ship design – the eponymous Battlestar Galactica – through the lens of some ship design principles developed for early dreadnoughts. We’re going to be talking about gun position.

We want to start by actually identifying the main battery on the Galactica (and others of it’s class, the Jupiter-Class in the lore of the series) and noting the gun positions. This is actually quite difficult in the show – the shaky cam and use of close-ups often makes it hard to know exactly what part of the ship you are looking at when any of the batteries fire. Fortunately, the (apparently canon, from what I can tell) strategy game Battlestar Galactica: Deadlock provides us with not one but two models of the Galactica’s class (one pre-refit, one post-refit; the latter corresponds to the version seen in the show) from its period of active service, which let us see exactly where the batteries are. The initial configuration looks like this:

While the post-refit configuration (the one that appears, with minor modifications, in the show) looks like this:

The latter clearly has a bit more firepower and a somewhat slimmed down design, but the essentials of the gun layout follows the same basic system. The largest concentration of firepower is in the dorsal gun turrets (on the upper-side of the ship), in two sets of four double-turrets arranged in squares, though the heaviest guns are the front-mounted turrets, slung underneath the ship’s bow in a pair of double-turrets. Those guns are called ‘door-kickers’ in the fiction, though the traditional name for them drawn from the sailing-ship-era would be ‘bow chasers’ (a subset of ‘chase guns’ more broadly), since they are not really part of the main battery. Another, smaller set of heavy guns is set below the ship (ventral), but is not part of the dorsal battery, since the two generally cannot be directed at the same targets (the ventral guns cannot elevate enough and the dorsal guns cannot depress enough, in part because of the placement of the flight pods).

Finally, there is a set of smaller, more rapidly firing point-defense guns arranged on the flight-pod itself, covering the port and starboard respectively. In the game, these guns are the ones responsible for flak barrages, though in the show we also see the guns of the main battery participate. That’s actually not entirely crazy – dual-purpose anti-ship/anti-air guns were deployed on many WWII era surface ships, with even the massive 18.1″ main battery of the Yamato-class being able to fire an anti-air shell – admittedly one that, like most Japanese AA in the war, was of sharply limited utility.

Now, it is true that battlestars as shown in the series have an additional set of weapons: the fighters contained in their two flight pods (sidenote: paired, unconnected flight pods seem like they would create really awful storage and fire-prevention problems for munitions and fuel). But I think it’s fair to say that the primary armament of the battlestar is its main guns. It is quite clear in the series that Colonial Fleet doctrine is to close into range of the heavy conventional batteries and then batter enemy ships into submission – indeed, the combat air group a battlestar carries is very poorly adapted to engage capital ships by itself, as it features no dedicated bomber (the Raptor can do the job, but is really a repurposed scout ship, not a bombing specialist).


So what is wrong with this layout? The main issue (and this becomes painfully clear when playing the game, rather than watching the show) is that the firing arcs of these guns are terrible, for two separate, but important reasons.

The first is the firing sweep the guns themselves have (how wide is the firing arc). The rearmost cluster of dorsal guns are at least partially obstructed by the engine housing in both versions of the ship (more so in the Mk1) and all of the dorsal guns are blocked from firing low and forward by the bow section, which is ‘taller’ than the mid-section where the guns are mounted (this is worse for the Mk1 than the Mk2, but they both have the problem). The ventral guns have all of these problems, but worse, most notably in the ventral gun clusters on the Mk2, which cannot fully depress its guns because they have been, for some inexplicable reason, placed in a depression in the hull.

As an aside: I find the bow-bulge an unlikely design problem. The bow section of a Battlestar doesn’t contain the main weapon system, or the drive system (either FTL or sub-light), or anything for flight operations, which is to say that it is neither the primary weapon system, nor the primary propulsion system. It mostly seems to house crew and command spaces. Looking across naval design over the centuries from oars to sails to nuclear reactors, one of the few constants is that the overall shape and profile of the ships are dictated by propulsion and armament (with crew facilities essentially jammed in ‘wherever they fit’). So it is a bit baffling what in the bow section is so important that it was worth over-sizing the bow and thus partially obscuring the main battery to fit in. Speaking from historical designs, anything in the bow section is likely to be compromised to preserve the main battery’s firing angles.

This gun sweep problem is further compounded by the clustering of the guns themselves. While the clusters will work fine if firing ‘up’ or ‘down’ relative to the ship’s orientation, any relatively flat firing trajectory leaves them blocked by each other that is, the front guns in a cluster cannot fire backwards and the port guns cannot fire starboard and so on. Chances are, the firing ‘deadzones’ are significantly larger than they appear; I’m not clear exactly what the tech is (if these are railguns or traditional chemically propelled guns), but it clearly shows muzzle blast on firing, so a ‘near miss’ of a friendly turret is still going to blast them with hot gas or other firing debris. As we’ll see in a moment, this sort of design issue was present in many early dreadnoughts, and I can’t imagine the vacuum of space would make it any better – on the upside, there would be no pressure wave, but on the downside, that would mean the gas would arrive to the back of the friendly turret with all of its velocity and nearly all of its heat.

The second problem is those firing arcs taken together: there is effectively no angle at which a Jupiter-class battlestar can actually bring most or all of its firepower to bear on a large enemy target. No matter the angle of enemy attack, a significant portion of Galactica‘s guns have quite literally nothing to do. If the target is level and in front of Galactica, only the bow-chasers can fire, but they cannot fire if the target is below or above and only half of them can fire to either port or starboard. Targets on the broadside and level with the flight pods can only be engaged by half of the dorsal and ventral guns (or less, depending on the angle), while targets above Galactica may take the full brunt of the dorsal battery but nothing else.

(As a side note, experienced Deadlock players may note that there is a small window where distant targets which are – relative to a Jupiter – in front and slightly above, may be engaged by both the door-kickers (which can elevate, if only slightly, from the ‘waterline’) and the dorsal battery, but (at least in my experience) that zone is painfully small and hardly seems an intended part of the ship’s design.)

I suspect that the gun positions here were arrived at for cinematic reasons, of course. In shot composition, relative height often indicates power. By having Galactica‘s guns mostly mounted on top, Galactica can be repeatedly put in scenes where it is ‘below’ Cylon adversaries, which I suspect was an intentional effort to visually display the extreme power imbalance between the humans and Cylons. Which is a pretty solid reason to set the ship up this way for a TV show and it works very well in the show to create very dynamic and dramatic combat scenes.

But of course, we’re here for pedantry, not sound visual design. And so we turn to our second section: how was this handled historically, or

What Galactica can learn from South Carolina (BB-26)

Many of these same sorts of issues – what sort of main batter to have, and where should it go – bedeviled naval design in the late 1800s and early 1900s, both before and for the first few years after the development of HMS Dreadnought (launched 1906). Now, there were quite a lot of factors that played a role in the emergence of Dreadnought and the entire ship-type that was named after her; the development of the dreadnoughts was itself a product of the complex interplay of developments in gunnery, armor and steam propulsion, with naval designers attempting to navigate the trade-offs between the three.

But here I want to get at two key ideas: what does it mean when we describe Dreadnought as all big gun and how are all of those big guns are laid out.

To explain the former, we have to actually begin with pre-dreadnoughts (which obviously were not called that in their day – they were just called ‘battleships’). These ships tended to have mixed batteries of guns in a wide range of calibers. The reasoning was that the smaller guns could fire more rapidly and so more successfully engage smaller, faster targets (like torpedo boats), while the big guns were necessary to engage other battleships. These were classed as the ‘primary’ battery (the big guns, mounted in turrets) and a ‘secondary’ battery (the fast-firing smaller guns, usually mounted in casemates); some pre-dreadnoughts also mounted an even smaller ‘tertiary’ battery. Within these batteries, some pre-dreadnoughts mixed calibers as well, since different guns would be at different effectiveness against different targets (as well as for availability concerns, e.g. the Japanese Satsuma class). I find pre-dreadnought design fascinating even though it was a developmental dead-end.

(As an aside: one thing Galactica keeps from the pre-dreadnought era is the use of casemates. A casemate was an armored wall along the side of the ship which would house the secondary guns. The armor of the casemate made these positions more protected than if the guns were just placed, unarmored, on the deck, but casemates often had sharply restricted firing angles (particularly for elevation). Casemates steadily vanished after dreadnought, with the secondary battery – increasingly (post-1920) in an anti-air role – moved to small turrets mounted on the upper decks. But Galactica’s point-defense turrets are mounted in what appear to be effectively casemates, projecting out from between the structural beams that support the outer armor layer. Compared to modern close-in weapon system (CIWS, pronounced see-wiz) mounts, the firing angles for those point-defense weapons are not very good).

In the first half of the first decade of the 1900s, a combination of developments lead towards the development of the all big gun battleship, the first of which was Dreadnought (and thus subsequent all big gun battleships were called ‘dreadnoughts’). Better loading systems and range-finding had improved accuracy (especially at long range) and rate of fire on the big guns, reducing the dependence of fast-firing secondaries (whose duties were, in many cases, offloaded onto escorting cruisers anyway), while improvements in battleship armor made it increasingly clear that anything less than the heaviest artillery was likely to be useless. Since all of the work was likely to be done by the main battery, it made sense to prioritize it more heavily.

A single, uniform main battery of big guns also greatly simplified fire control and direction, because you were now working a single set of guns with identical range, muzzle velocity and firing characteristics. While a more limited secondary battery was kept, the primary focus of Dreadnought‘s design was the main battery, and on the assumption that the main battery, working through a single fire control system, would be focused on a single target. Of course a uniform shell-type over the main battery also makes logistics quite a bit easier as well.

Now the question is: where do all of those big guns go? There are a lot of really fascinating designs in the early years after Dreadnought and in terms of main battery layout, Dreadnought herself is less a final version and more an intermediate stage. Dreadnought cannot face all of her guns in any direction – of the five turrets, only four can fire to port or starboard (the two wing turrets being the problem here), only one turret can fire directly aft (due to the placement of the rear tower). In theory, three turrets can fire forward, but in practice – remember I said we’d come back to this – actually firing the wing guns directly forward was likely to blow out the conning tower (whoops…).

Early dreadnought designs attempted a variety of gun-layouts in an effort to allow for maximum firepower to be concentrated on a single target. Early German designs, like the Nassau– and Helgoland-class used a ‘hexagonal’ layout, which allowed them to mount more guns than Dreadnought, but it didn’t allow them to bring any more of those guns to bear on a single target – the layout was abandoned because it increased the weight of the hull without any real advantage in deliverable firepower.

Another layout was the (crazy, but also kind of awesome) zig-zag layout of ships like HMS Neptune. Neptune could, conceivably bring all of its guns to bear either port or starboard – the staggered arrangement meant that they didn’t obstruct each other. But it also meant that the turrets amidships would have to fire through the upper-works; in practice, this was found to do significant damage to the ship – the same blast-damage problem we saw earlier with Dreadnought‘s wing guns.

(As an aside: the other problem with layouts set with heavy wing turrets is that they tend to make the ship unstable because they move so much of the weight away from the ship’s centerline. I’m not sure, for a space-ship, how much this would be a concern.)

The solution actually came from the US Navy from an odd direction: Congress. No, I am not kidding. The US Navy had been having the same set of realizations that led the British to Dreadnought, and so in 1905, they went to Congress asking if they could build some fancy new battleships too (Dreadnought was well under construction by this point). Congress, however, was about done with the Navy – they had just built and launched six Connecticut class pre-dreadnoughts (remember though, they were just ‘battleships’ at this point), several of which weren’t even done yet and already the Navy wanted a new ship class? So, in an effort to hold down the cost, Congress demanded that whatever the navy built, it had to be 16,000 tons or less.

Dreadnought, to be clear, as 18,120 tons. So weight would need to be saved. Under those kinds of displacement constraints, having turrets that didn’t do anything was hardly an option, meaning that optimal firing positions were vital to be able to get a ship that could stand up to a Dreadnought at a lower displacement. The solution was superfiring.

No, that doesn’t mean ‘firing better’ but rather (following the Latin) firing over. The South Carolina-class would have two turrets forward and two turrets aft, in each case with one turret firing over the one in front of it. The long barrels would put the muzzle blast safely out in front of (most of) the turret-housing of the lower turret. As an added bonus, in some designs, both turrets in a group could protect their magazines and works with a smaller armored ‘citadel,’ which also saved weight. This appears most famously on the absolutely hideous looking (but fairly effective) Nelson-class of British battleships (c. 1927) which had three triple-turrets, all set forward together to save on weight to keep the ship under the limits of the Washington Naval Treaty.

So while Dreadnought had 5 double turrets could put 4 to each broadside, 1 to aft and 1-3 fore, the South Carolina with just four double-turrets could put all four to either side, 2 to the aft and two to the fore, without any danger of accidentally blowing out her own conning tower. Now, there were some challenges for superfiring gun arrangements – taller turrets meant moving more mass up on the ship, bringing the center of gravity up and potentially destabilizing the entire ship. That, in turn, put a sharp limit to the number of turrets which could be ‘stacked’ (typically just two). Which was just as well, because it rapidly became apparent that – forced to choose between more guns and bigger guns – bigger was generally the best option.

While it took a few years to fully catch on, for battleships, superfiring gun layouts eventually dominated battleship design, because it allowed the ship in question to concentrate all of its big-gun anti-capital ship firepower on a single target.

Re-imagining Galactica

Keeping our historical battleship design in mind, we can revisit Galactica. Now, it is perfectly fine if Galactica’s secondary battery (intended to engage fighters and provide point-defense against missiles) is split all over the ship for coverage. But the same factors – weight of fire, ease of fire control, mass-and-space savings – that lead to the development of uniform caliber, superfiring battleship main batteries are all at play here.

The exact positioning of that main battery would depend very significantly on the intended engagement angle. Rather than spreading the main guns all around, the ship would be planned with a single angle that most – if not all – of the main battery could focus on a single target. For a ship moving in three dimensions (instead of two) there are really three options: an angle perpendicular to the ship’s primary direction of acceleration (essentially ‘broadside’ but would also cover dorsal and ventral angles), an angle opposite to the primary direction of acceleration (aft) or with the acceleration (fore).

In the case of the Galactica – a ship armed with mostly shorter range conventional munitions, whose primary threat consists of large enemy carriers operating at long-range using strike-craft and missiles – I’d think a forward engagement angle would be the obvious choice. While Galactica is mostly engaged in time-buying defensive delays in the show, she wouldn’t have been designed for an escort role; Galactica was originally a front-line heavy combat ship, built to engage Cylon capital ships. Given that, it seems likely that Galactica would be firing while attempting to close with their targets – ‘charging’ while firing.

(An aside: Now, I’m assuming the physics and motion model that we see in the show and its associated games. While smaller ships in Battlestar Galactica are often shown to turn on their axis (flying one way and pointing another), larger ships seem to generally stay oriented towards the direction of their velocity. More to the point, ships tend to accelerate in the direction they want to go, rather than following orbital paths or transfer orbits, so I am going to assume that Galactica is likely to face-and-charge an opposing ship, rather than the more complex intercept trajectories you might get from orbital mechanics.)

So how might Galactica‘s main battery be moved in order to improve the firing angles? I think the solution lies in a superfiring gun layout. One of the main limits to superfiring gun positions on a battleship was that they raised the ship’s center of mass, resulting in instability – that’s why a ship like the HMS Nelson can’t elevate its third turret above the other two. But a ship can’t capsize in space (although you would want the vector of acceleration to pass trough the center of mass, so that turning on the engines doesn’t rotate the ship), so you could superposition quite a lot more of the battery. Instead of mounting the guns in clusters on center of the ship, they could be mounted on the bow section, in superpositioned mounts (presumably with crew and command facilities moved to the center section of the ship).

If I could make further design changes, rather than the current layout of a lot of mid-sized guns and some point-defense guns, I might seek to compress the main battery into a handful of much larger emplacements (super-positioned on the bow) while expanding the number of smaller emplacements mounted in dorsal or ventral positions (ideally with nice, big firing arcs). The center section might also be made taller, but not so long (so that it isn’t obscured by the bow or aft) to allow better firing arcs.


This bit of design silliness is by no means limited to Battlestar Galactica. If anything, the firing angles on Imperial Star Destroyers from Star Wars are even worse. The ship is shaped like a diamond, which promises lots of space for superpositioned guns, but instead the main battery is set to either side of the main tower, with the turrets lined up such that they make it impossible for all of the guns to be fired forward.

One thing I haven’t discussed here, but is closely related to the intended angle of engagement is armor placement. Armor is almost never uniformly thick on any armored vehicle, be it a warship or a tank – instead, armor is carefully shaped around key assumptions on the likely angle of attack as well as what parts of the vehicle are most important. You can see this quite clearly in tank design, where rear and top armor is typically much thinner than front or side armor. We’d expect the same consideration for a ship like Galactica – and in Deadlock, this is actually the case – the broadsides and front arc are far more heavily armored than the rear, top or bottom.

Now, does all of this matter? Honestly, no, not really. Certainly, I find that making designs in speculative fiction more plausible by leaning on historical design philosophies can make the fictional world itself feel more real which can improve the storytelling.

But I think the real take-away here is an obvious but oft forgotten one: while it is easy to critique the designs of historical weapon systems, they were in fact the product of quite a lot of smart people working hard to solve difficult problems. “Doing it all” was never an option – every bit of added firepower or armor meant more weight and thus less speed (or, in space, a worse thrust-to-mass ratio). In turn, that meant for a given engine and speed requirement, every bit of armor meant less firepower, and vice versa. Having lots of small guns meant fewer guns in the main battery.

Often when we see designs that are clearly compromised in some way – like, famously, the M4 Sherman – we attribute this to ‘bad’ design, when it is often in fact the product of forced compromises in the design process between competing and incompatible design goals.

(Clarification note: I think a few folks may have misunderstood my comment about the Sherman. I’d actually argue that – in light of the demands placed on its design, particularly by logistics – the M4 Sherman is a remarkable feat of successful design. I was merely noting that it is also a deeply compromised design and one with an (unearned, in my view) bad reputation with many enthusiasts in the public – although this seems to be turning around lately).


This week’s post will be a bit shorter, as the holidays are now upon us and the year is winding down (but don’t worry – I have a humdinger of a series planned for January – no, not that one; one you did not expect). This week is going to serve as a bit of an addendum to Where Does My Main Battery Go and a bit more silly sci-fi fun to round out the year. Specifically, I want to expand a bit on this statement:

Looking across naval design over the centuries from oars to sails to nuclear reactors, one of the few constants is that the overall shape and profile of the ships are dictated by propulsion and armament (with crew facilities essentially jammed in ‘wherever they fit’).

I wanted to expand on this idea and trace it historically.

What I often see in sci-fi settings are space warships that look like this:

Or this:

Or even the venerable Imperial Star Destroyer (in this case, an Imperial I, because yes, I am that kind of nerd – you can tell from the communications tower):

What strikes me as off about these designs are their silhouettes – or rather, what they imply, which is that they have been designed around a shape rather than around a function. For the Star Destroyer, at least, I can see parts of the design that have been forced to make way for the main reactor, which bulges out of the bottom of the ship (but my heavens, the decision was made to deform the primary armor around the reactor, rather than simply designing the ship from the ground-up to put such an important thing entirely internal to the spaceframe?). But for what is essentially a gunship, what is so striking about the Star Destroyer is how muted the main battery is to the overall design – I suspect most movie-goers don’t even notice the turrets set on either side of the central island (which is also, as an aside, a terrible spot for them).

Instead, the main armament – and even, to a degree, even the propulsion – appears to be an afterthought. Some series do this more than others – Star Trek ships generally have very prominent engines (in those classic nacelles), but with such understated main weapons – even on the more militarily focused Constitution and Sovereign classes – so much so that the SFX teams routinely forgot what is where and had the wrong weapon shoot out of the wrong place (Kirk, in particular, seems fond in the original series of firing phasers out of his torpedo bays).

(I don’t want to get too out of the way making fun of Sci-fi ship designs, but can I just note that the basic layout of Federation starships – with engines connected to the main ship by long, fragile pylons, makes no sense. I mean, I understand from a production standpoint that originally the idea was that every ship would have two warp nacelles and they’d always have to have line-of-sight on each other to work (thus the moving nacelles on Voyager and Ferengi ships), but they seem eventually to have ditched that in later designs, which then makes what is supposed to be centuries of Federation ship design look really, really foolish if that line-of-sight thing wasn’t strictly necessary.)

What almost all of these ships seem to have in common is that they look like actually began with the shape of the ship and then back-filled how the key components of the ship might fit in with that shape. And that’s probably because that’s exactly how they were made – with artists and modelers working up from a basic idea of the overall shape and visual style of the ship and adding details. Often – as for instance with designers discussing Star Wars starfighters here (note that they discuss the new movie in the last few minutes) – they began by adopting shapes from existing machines.

The problem with this is that you get a ship where the primary purpose of the craft is literally an afterthought in its design – a few tiny ‘guns’ glued on to the side of the model after it is by and large done. And so what you don’t see – compared to any kind of historical warship – are the ways that the demands of the two most dominant design features, propulsion and armament define the shape and silhouette of a design. Indeed, in some ships, the design seems to literally contort around these features – as well it should, as they are the reason for the ship!

Early Purpose Built Warships

To see what I mean, lets talk about the design of naval warships. Now, in a way, the design of historical warships is, if anything more restrictive than the design of most space warships, which tend (in their respective fictions) to be built in space and never operate in atmosphere. Ships that ply the seas rather than the stars are constrained by the shapes they must have to sail effectively; starships have no such limitations.

I’ll cut to the chase: the silhouettes of historical warships are always dominated by two key factors: propulsion and armament. In nearly all cases, everything not directly linked to one of those two facets of performance is relegated to a secondary status (we should make exception, especially in the modern era for armor, but modern warship armor has more often had to conform to a shape dictated by the other two factors, rather than the other way around – that said, the impact of armor on weight was a huge influence in warship design, and a considerable, but more subtle and harder to spot – but very important – influence on warship shape).

This makes a certain degree of sense: the primary role of any purpose-built warship (aside: I’m going to avoid multi-purpose craft – ships that can serve both military and civilian roles – here, in both my sci-fi and real world examples) is to deliver a primary armament of some sort to a battlespace. The subordination of every other function of the ship to these main purposes plays itself out visually in the design. Let’s start with an old example: possibly the oldest purpose-built warship in the world, the Mediterranean trireme:

What I’m going to do with each of these images is put red marks around the primary armament of the ship in question and blue marks around the propulsion systems. In the event, the trireme is an awkward first example: the oars serve both as part of the propulsion, but also part of the armament, as the trireme’s main weapon was speed. While later Mediterranean oared warships may have been more focused on boarding (this is a hotly contested topic, I recommend W. Murray, Age of the Titans (2012) to get a sense of the debate and the design considerations it spawned), the trireme was definitely a ramming oriented ship. The perfect engagement was one where it got in, got the hit, and then backwatered back away again.

Consequently, triremes were built for speed, because speed was offensive power. Everything was sacrificed for this: there is functionally no cargo room, literally no crew quarters (the rowers slept on their benches) and the ship’s structure is built light and thin (with costs to both survivability and seaworthiness). Occasionally a sci-fi show will joke that a given ship is “little more than guns with an engine strapped on” but the trireme is almost literally this thing – little more than a ram with a (human powered) engine installed in the back.

Centuries of evolution in the design did not change the basic balance of speed and armament:

Moving into the age of sail, we can see a similar dominance in ships of the line:

Now, the ships of the line are a bit of an odd case, because they descend from, and thus share design characteristics with, the multi-purpose sailing ships of the 16th and 17th centuries. Nevertheless, the design demands of being a specialist warship have taken their toll: the demand for more guns meant stacking additional gun-decks vertically, which in turn gives the ship a deep draft (which you cannot see, because it’s below the waterline; and yes, yes, this is a British ship, so I suppose it has a deep draught). That in turn has demanded a broader beam (that is, the ship is wider) to maintain a stable platform – Victory, with three decks of guns (plus lighter guns on the quarterdeck) is nearly 16m wide, while a classic 74-gun third-rate ship of the line might be only 14m wide, and a single-gun-deck ship like a light frigate might need only to be 10-12m wide.

Battleship Design

Alright, I hear you say, but what about a more modern ship? Something with an engine? One of the (more or less) constants of pre-dreadnought and dreadnought design was that, in terms of displacement (essentially weight), around two-third of any given battleship consisted of the main propulsion, the primary armaments, and the armor. Everything else – everything else: crew quarters, crew amenities (food, post, hygiene, recreation, social spaces), command spaces, storage spaces, damage control equipment, machining tools for repairs, all of it – had to be squeezed into the remaining third or so.

Meanwhile, the relatively inflexible demands of the shape of the main battery and primary propulsion (along with the demand for elevated command spaces to allow for effective navigation and spotting) mean that all of those other things had to be crammed into whatever space the ship’s hull made available. As an aside: this design philosophy is abundantly clear if you’ve ever been on a museum ship that lets you get around even a little bit – bunk spaces and mess halls and the like are crammed into whatever space is available, sometimes contorted around other, more important ship functions. For instance, the world’s sole surviving pre-dreadnought, IJN Mikasa:

Now, you may say – “wait, but you’ve designated the secondary guns as part of the main armament” – but remember, this is a pre-dreadnought, so the secondaries are still conceptually part of the main armament, which is why they’re allowed to dictate so much of the ships central mass, rather than being confined to casemates or upper-works wherever they will fit (a more common pattern in later dreadnoughts, until WWII when the placement of secondaries, now anti-air batteries, begin to matter a lot again) – instead, the housing for the casemates of the secondary battery is a core part of the design and takes up a lot of the space above the waterline.

The propulsion system of a ship like this dominates the space of the ship’s lower decks. On Mikasa, directly beneath the smoke-stacks were 25 coal-fueled boilers, which fed power to a pair of triple-expansion engines (a compound steam engine which passes the steam through multiple cylinders to extract more power) set aft of the boilers, which in turn drive the shaft out to the propellers. The space the entire assembly demands is actually visible in the placement of the stacks – no doubt naval designers would have loved to place the smoke-stacks somewhere, anywhere where they wouldn’t frequently cloud the aft spotting tower with smoke, but the demands of powerful engines capable of moving such a heavy ship at respectable speeds forced compromise.

I think modern warships – by modern here, I really mean post-1880 or so – conceal some of the degree to which propulsion and main armament dominate the ship’s design (and thus its appearance) because so much is hidden beneath the decks. Note, for instance that the big-gun turrets are not the only part of that gun system – the entire gun assembly is actually five decks tall, plus the turret, beginning with magazines and ammunition storage at the bottom, and a lift for shells to be brought up to the guns. The motor that turns the turret is roughly at the waterline (on the platform deck) and the systems to elevate and train the guns are themselves nearly two decks tall. That assembly is protected – above and below the main deck by an armored shell called a barbette. A large part of the reason this entire setup is stacked vertically is so that the magazines – which take up quite a bit of space – can be placed as low in the hull as possible, since a hit to a magazine would almost certainly doom the ship. In short, the barrel of the gun and the turret that you see poking out of the top are just the tip of the iceberg of the total gun assembly.

And remember, this is a pre-dreadnought, oriented around a mixed battery of guns. What about a modern ‘super-dreadnought’ all-big gun battleship? Now, I’m sure you’re all expecting Yamato and Musashi‘s massive 18.1in guns, but I don’t have a good internal layout plan for the Yamato, so I’m going to go with an USN Iowa-Class ship, the USS Missouri (BB-63), both because I can find a full deck plan, but it’s also a design I’m more familiar with. Same deal as before:

The turret assembly for each of the (technically-not-triple, they can elevate independently) triple-16in turrets is even larger than Mikasa and runs all the way to the keel and fills nearly all of the horizontal space on every deck with the equipment for raising shells, elevating the guns, turning the turrets, magazines and so on. You can get a pretty good sense of what all of the stations in the turret are doing from this 1955 training video on the operation of the guns.

I want to contrast that with the scale of a Star Destroyer’s main armament – you will need to excuse the poor picture, I took it from my copy of Star Wars: Incredible Cross-Sections (I told you, I am that kind of nerd – I’ve had this book, along with the Essential Guides, since I was in high school, much of it even back before the Dark Times, before the Prequels), the book is quite large and scanner-unfriendly, so I had to use a camera:

By my count, the entire assembly – fire control, power cells, the turret itself, everything but the reactor powering the damn thing – comprises about 8 decks. To give a sense of the comparative size of these two ‘battleships’ – the Mikasa is 131.7m long and has a beam of 23.2m; a Star Destroyer is supposed to be 1,600m, and up to 600m wide. It is, conservatively, something like two thousand times larger than Mikasa (perhaps a thousand times the size of Missouri) in terms of total volume, yet the gun main gun assembly looks to be only a bit larger – and it includes fire control (which was not housed inside the turrets on historical battleships because that is a very silly place for it) – and it only has eight main turrets. The total volume – and one assumes mass – of the Star Destroyer devoted to its armaments – even if the main reactor is included – is shocking small.

It really makes me wonder what all of those other decks are for on a Star Destroyer. Oh, sure, you have the hanger spaces, but these are all in the thin end of the wedge and don’t even seem to fill that – what on earth is taking up all of the space in the massive island in the center-aft of the thing? Looking at various cross-sections and technical drawings, the answer appears to be ‘nothing.’

(As an aside before it comes up: ‘what about aircraft carriers?’ Well, the main armament of an aircraft carrier is its air-wing, which (in its full operation) takes up the entire flight deck, plus the entire hanger deck, both of which in modern carriers run the full length of the ship, plus armory spaces further down and repair and machinery. If anything, an aircraft carrier is more contorted by its main armament than any other modern type of warship.)

Done Right?

After the last post on sci-fi ship design, a number of folks asked me if there were any designs that struck me as having felt a bit more on-target. And there are some – a common design, particularly in video-games, are ships built around a single large spinal-mount railgun (e.g. Mass Effect, Halo), resulting in a design with a main reactor in the middle, plugged into an engine assembly behind it, a gun assembly in front of it, and the rest of the ship essentially wrapped around that core in whatever shape will fit. I also think that – though I am only now making my way through the series – a lot of the ships of The Expanse strike a good balance, for instance the Donnager-class:

The main armament is on the bow in two massive turrets and one assumes that the power, ammunition and battery stems for those huge railguns dominate that mid-ship-section, while the massive engine (and presumably reactor) dominate the ship’s aft (although it also has a lot of big internal empty storage space which I find a little unlikely for a ship that is still essentially a gun-delivery-system. Science-fiction loves big multi-multi-purpose ships with marines and fighters and guns and mid-sized craft, but in practice it is hard to see why those functions wouldn’t be split up between specialist craft (so that you are only lugging the capabilities you need, all the more important when fuel and available delta-v matter).

Rear Firing Weapons

Spacedock has an interesting thought on weapon placement. Please note that he is making the assumption that for a given warship there will be a preferred range (PR) to an enemy target, a range where your weapon types and ranges will have an advantage over the enemy (example, a ship designed like an artillery piece. Much longer range than conventional weapons, but sluggishly unmaneuverable if the enemy gets too close). This may or may not be true for all ships, but if so it is desirable for your ship to maneuver to keep the enemy within the desired range. Which has an implication:

So if the enemy is at location X, when you approach you want to brake to a halt such that the enemy is at the preferred range (PR). Since you were traveling to location X in order to blow that dastardly enemy ship to Em-Cee-Squared, your vector is pointed right at them. In order to decelerate you have to flip and burn, rotating the ship so that the exhaust is traveling in the same direction as the vector so that the thrust brakes the vector down to being stationary.

See what this means? You are showing your ship's fat ass to the enemy.

Now, assume that you are quote "stationary" unquote with respect to the enemy. Oh ho! That foul villain is burning their jets to get closer, so as to get you inside their PR. You will have to back away from them to preserve your range advantage while they try to close. This means burning your jets in the same direction they are. Yep, this means once again you are showing your ship's fat ass to the enemy.

Why is this a problem? Well, just look at the weapon arcs of most media sci-fi spacecraft. They mostly have all the weapons on the nose. So both while braking to a stop and backing away your weapons are pointed in the wrong direction. Meanwhile an enemy with nose mounted weapons can fire at you with everything they got, right up your kilt.

So logically most of the weapons should be on the aft end of your ship, nestled among the engines. This was actually used in the Babylon 5 episode Severed Dreams, when an Omega Destroyer was running away from a pursuing ship, said ship found out the hard way the Omega has rear-firing guns.

Now, of course things are not quite that simple.

  • The video itself notes that it would make sense to mount weapon turrets on outrigger pylons, so they can fire to the fore and to the aft. This would be a good place to use superfiring.

  • The video suggest having additional engines mounted on the fore of the ship, not itty-bitty braking thrusters but ones second only to the engines on the aft. I am personally dubious about this because not only is this wasteful of ship mass (cutting into the allowable weapon mass) but also using these engines will turn the floor into the ceiling. A more extreme example is the Globetrotter concept, which I find difficult to take seriously.

  • If the enemy is trying to back away from you, then you want your weapons to be mounted on the nose.

  • It is possible to use Cascade Vanes to provide reverse thrust. This would allow your ship to slow down and even start backing up while your nose was aimed at the enemy. Drawbacks are it only provides up to 50% of max thrust, and the exhaust has to be cool enough so it doesn't vaporize the vanes.

  • Your ship's propulsion system might be dual-use as a weapon. So you can brake with your engine pointed at the enemy AND give them a quick refresher course on the Kzinti Lesson.

  • The situation changes if you and the enemy are in orbit around a planet or moon. Raising and lowering one's orbital radius requires thrusting in retrograde and prograde directions. Which can be nowhere near the direction to the enemy.


      This is a rendition of a “laserstar”—that is, a warship with a big laser designed for extremely-long-range standoff tactics (i.e., it is artillery).

     In space, higher frequencies for laser weapons are preferred for two reasons: (1) higher frequencies diffract less and therefore the beam can stay focused for a longer distance and (2) higher frequencies are better-absorbed by just-about every material (in a laser weapon you want the target to absorb as much of the beam as possible).
     Therefore, a typical laserstar design uses some kind of “XFEL”—that is, an X-ray free-electron laser, named for the frequency range (the wide spectrum of X-rays) and the underlying technology used to generate the beam.
     XFELs, like most FELs, can be surprisingly efficient in-terms of converting electrical power into coherent light. Nevertheless, there is still inefficiency, and of course there is also the inefficiency of the reactor itself. Wherefore we need the enormous radiator fins you see on the back of the ship. Note that the radiators are behind the wing-like protrusions. This is deliberate: it shields them from incoming fire. Aesthetically, I initially wanted the radiators to come out vertically above and below, but I recognized that that would be unrealistic. Only the best for you.

     The wing-like things are canted forward (the front-facing surfaces come forwards to a point, instead of being flat) by a significant amount, the better to present an angle to oncoming fire (slanted armor is OP). They also have two conical depressions, which are actually rocket nozzles. These face back along the direction of fire so that the ship can be decelerating toward or fleeing from a target, while still being able to bring its laser to bear on that target. This is important because, unlike a conventional laser or kinetic weapon, X-rays don’t bend well, so the ship really must be pointing in the exact direction it wants to fire. (in other words: designed according to Spacedock's idea of rear firing weapons)
     In fact, lenses don’t work at all at such high frequencies. Designers must use grazing-incidence mirrors to shape the beam. Even so, much energy is lost in a grazing-incidence mirror, and the excess energy must be radiated away as heat. This explains the huge hexagonal structure coming out the front, and the six radiator fins sticking out from each focusing ring.

     Even despite the high frequency, some tiny fraction of the light diffracts toward the camera, bathing it in a cancerous wash of ionizing radiation. X-rays are invisible, of course, but, being hard radiation, they are perfectly capable of flipping random bits in, for example, a photoreceptor, giving the appearance of fake visible light. This happens stochastically, explaining why you see random speckles of red, green, and blue color (nearly all cameras ever are RGB). In the original drawing, there are more green speckles than other colors because typical camera Bayer filters have more green than blue or red (since human eyes are more-sensitive to green, it makes sense to have more sample area devoted to green; this leads to more bitflips on green subpixels), but my scanner appears to have made most of them white.

     The sphere in the background was originally intended to be Earth after an apocalyptic war à la Children of a Dead Earth (the existence of laserstars would prove, among other things, my firmly-held belief that humans are lacking in good sense). However, since Earth with boiled oceans would have dense, white cloud cover obscuring everything on the surface, you can feasibly imagine it’s a wide variety of planets or moons as you please.

from a post by Ian Mallett (2019)

3D Firing Arcs

Tabletop starship combat games have been around at least since the 1970s, if not earlier. Even the ones with starship weapon firing arcs. Since this was about a decade before the advent of the home computer, the game designers had to make do with paper and cardboard.

Specifically, they had no access to 3D holographic displays (actually, as of 2020 they still don't). Trying to allow the players to easily figure firing arcs with paper aids was and is a monumental challenge.

I vaguely remember seeing a game simulating Sopwith Camel vs Fokker Triplane World War I aerial combat where the miniature aircraft were attached to vertical rulers by The rulers were set vertically into large square wooden bases. The fact the game was very short lived demonstrated what a poor solution this was. If I recall correctly, there was also no easy way to show the orientation of the aircraft: climbing, diving, upside down, etc. All of these influence player visualization of 3D firing arcs.

In 1997 a company called New Dimension Games came out with a 3D game called MoonDragon. The rulers were replaced by telescoping metal rods with the spacecraft on the tip. The ship miniatures were attached to the tip by a tiny multi-jointed arm to allow orientation of the ship to be displayed. Paper templates indicating the width of the firing arc were held on the ship miniature at weapon locations to see if the opponent was or was not inside the arc.

This game as well soon vanished because player found it was more trouble than it was worth.

So almost all tabletop starship combat games were strictly two dimensional. Game designers figured the added realism was not worth the added difficulty. And after all, the designers argued, "three points define a plane" so three fighting starships can be approximated by playing on a two-dimensional surface (i.e., a conventional game map placed on a table top). If a player asked the designer what about four or more fighting starships, the designer would testily reply with something like "just roll with it, OK?" or "go away kid, ya bother me".

There are three table top wargames that manage 3D firing arcs in a humans-can-play-without-computer-assistance level of usability: Ken Burnside's Attack Vector: Tactical (2004), Birds of Prey (2008) and Squadron Strike (2008). Mr. Burnside has had computerized play aids for Squadron Strike since 2015; there is development work on extending those play aids for Attack Vector: Tactical; I helped start the process back in 2003 with the Visor Handspring, though none of my code is in the current AVID Assistant (which is probably for the better). Since 2018, those smart phone play aids have been expanded into a Virtual Map that now sees somewhere around 6 to 10 games per week.


      As you may guess, I get told "3D doesn't matter in space!" a lot.

The Ways That 3D Impacts Fighting In Space

     A) Orientation — if your guns have firing arcs the belly gun of a B-17 can't shoot at things above it, forward firing guns often can't fire to the rear. If your guns have spherical firing arcs (they can fire in any direction, i.e., they ignore firing arcs), then relative angle and position don't matter, but at that point, I'm not sure why you (and your tabletop game) care about individual ships and position rather than abstract combat factors.

     If your guns have firing arcs, then you have to track orientation of units in 3D and figuring out what's in arc becomes something more involved than just "eyeballing" it.

     Also, rotating things in 3D is easiest if you have an implicit spherical reference frame. It takes more up-front teaching, but it's vastly easier in actual play; the AVID and PHAD (Birds of Prey's (BoP) play aid that I adapted the AVID from) are spherical reference frames, and use quaternions under the hood to make things straightforward.

     B) Movement — if you have two units with velocity vectors and the ability to vector up and down, you now have four objects (the ships and their vector position markers), and it's trivially easy to make a situation that can't be handled in 2D. (Ship A is facing West, decelerating by thrusting in West to cancel its vector in East. Ship B has a vector in South and is thrusting in Up towards the objective. There is no frame of reference shift that will put both ships and their vectors in the same plane; the frame of vector shifts that come closest are nastier table-math than just doing it properly...)

     C) Range — your true range is Pythagorean. This means square roots SQRT(A^2+B^2). This can be pre-done in a lookup table. You can also use half-height altitude scaling for your hex scaling, treat Pi (π) as "3" (This is what BOP does). This is functionally "halve the smaller distance and add it to the larger" which is one trick for approximating the Pythagorean Theorem. A better one is to divide the smaller distance by 3 and round up, adding to the larger. A third trick is to print two rulers at right angles, place a card over them at an angle, with the corner at the altitude and sliding the card up until you cross the horizontal line, mark on the horizontal line, then measure the distance from the corner to the mark — which is easy, as you have a ruler right there.

     D) Bearing Angle — whatever you're using as your atomic angle of care, you have to take the tangent of the horizontal separation and vertical separation to find the bearing angle, and sort to see if it's within a particular bin. You can embed this in the Pythagorean chart (we did it in my games with color coding). The BoP solution (half height altitude and a vertical hex grid) still uses a range-and-altitude comparison to find the bearing angle, but could easily be color coded.

     E) Firing Arcs — Mapping the range and bearing angle to a firing arc; there are some very clever tricks for this that I use in my titles — they basically abstract taking phi and theta and turn it into "can you count to three?"

     F) Energy Management — when people say "3D matters in air combat because you can trade altitude for speed," they're talking about energy management. Energy management can be part of your movement system in a space game; Mode 1 movement in Squadron Strike bleeds speeds from facing changes and gains speed from thrust; building ships that want to thrust for a few turns before they start maneuvering tightly is one way to make them fun. In realistic physics, you can also get energy management effects by fighting in low orbits around planets:

     Prograde thrust takes you out (up in the map frame of reference), up takes you retrograde, retrograde takes you in (down in the map frame of reference) and down takes you prograde. All of these are changing the eccentricity of your orbit and may need correction when you're nearing the other "half" of your orbit where the opposite of your prior maneuver needs a recircularization burn. Thrusting left or right increases the inclination of your orbit. I handle this in Attack Vector: Tactical, and while it's fun, it is absolutely a brain burn kind of fun that, uh, not everyone agrees is fun.

     Basically, orbits turn orbital acceleration into angular velocity, which follows a right-hand-rule described in simple terms in the last paragraph.

     Trust me when I say the math under those simplifications is hairy…

     Finally, while not directly 3D, if you want vector movement, vector addition is faster with written records and arithmetic in opposing boxes rather than counting on the map.

     Partially-3D games that are mostly played in 2D are a reflection of "2D with altitude bands and no directional firing arcs or defenses is still 2D movement" rather than an indictment that 3D doesn't matter.

     The two images here are two different games. The first is SFB (Star Fleet Battles) tournament ships flying in 3D. The original position had 6 ships set up around a center hex — four of them arrayed in a square, one up by the same distance as the other four were from the center, and one down by the same distance.

     This is where we were after two turns of movement, lobbing torpedoes and other avoidable ordnance around…

     The second image is a base assault from Exile's Stars, where a unit that can't maneuver is still being attacked from multiple angles in 3D because of tactical advantages on the part of the maneuvering force.

Mount Protection

Weapons mounts are often armored to increase the weapon's lifespan under hostile weapons fire. There are several types.

A Gun Shield is simply a piece of armor attached towards the muzzle of the weapon. It does not provide much protection from any hostile fire except for return fire from your target.

A Gun Mantlet is like a gun shield attached to the base of the weapon, to protect the vulnerable point where the weapon emerges from the turret. In a real-world armored fighting vehicle, hostile weapons fire at that point could detonate the shell waiting inside the weapon. The resulting explosion, occuring inside the AFV would gut the thing. The mantlet's purpose is to prevent that unhappy chain of events.

This is only needed for conventional turrets where the gun emerges from a slot in the turret. The mantlet protects the open slot, or at least the part of the slot not currently plugged up by the gun. In an oscillating turret there is no slot so no mantlet is needed.

A Sponson is a weapon mount projecting from the "side" of a vehicle. It is a term usually applied to armored fighting vehicles. I am unsure how this differs from a turret. Or how it differs from a casemate. In any event, this maps poorly to a spacecraft which does not have a strong "up" and "down".

A Casemate is a broadside weapon housed in a vertical cylindrical armored shell, with a wide traverse but limited elevation. I'm not sure how this differs from a sponson.

A Turret is a gun covered in an armored structure on a rotating mount that penetrates the armor (i.e., it is not attached to the surface of the armor). It typically has very wide traverse and elevation.

A Cupola is a small turret mounted on top of a Turret. A tiny turret mounted on top of a cupola is called a finial.

Weapon Classifications

These are preliminary classification schemas offered "as-is". Tinker with them to suit your taste.

This scheme was created by Erik Max Francis, and contains some modifications by Isaac Kuo:

  1. Weapons systems.
    1. Banks. Beams of directed particles fired at a target.
      1. Electromagnetic beams. Beams of photons (note this includes lasers, masers, xasers, gasers, etc.).
        1. continuous
        2. pulsed
        3. single-shot submunition
      2. Particle beams. Beams of high-energy charged particles (such as protons).
        1. continuous
        2. pulsed
        3. single-shot submunition
    2. Cannon. Unguided projectiles directed at a ship target.
      1. Kinetics. Mere slugs fired at a target with no explosive capability.
      2. Shells. Unguided projectiles fired at a target which detonated with a proximity fuse and a conventional warhead.
    3. Tubes. Guided projectiles directed at a ship target.
      1. Missiles. Guided projectiles with a proximity fuse. Has higher acceleration than average target ship.
      2. Torpedoes (AKV). Guided projectiles with a proximity fuse. Has lower acceleration than average target ship.
      3. Rockets. Dumbfire missiles, which only accelerate in the direction they were fired.
    4. Releases. Guided projectiles directed at a planetary target.
      1. Atmospherics. Projectiles designed to reenter an atmosphere and detonate over a ground target.
      2. Biologics. Atmospherics with a biological warhead.
      3. Kinetics. No warhead. Does damage with kinetic energy, by large velocities or large mass, or both.
    5. Layers. Latent projectiles merely dropped with only a slightly different speed from the firing ship.
      1. Mines. Conventional warheads which drift in orbit and a proximity fuse which then accelerate toward their target and detonate.
  2. Active defense systems.
    1. Point defense. Smaller-sized kinetics, missiles, and beams directed at incoming weapons.
    2. Minesweepers. Point defense designed to eliminate mines.
    3. Charge dampener (?). Anticharge systems designed to reduce the damage caused by particle beams.
    4. Nanotechnology dynamic armor repair.
  3. Passive defense systems.
    1. Armor.
      1. Ablative armor.
      2. Reflective armor. Armor designed to deflect beam weapons, even as it is worn away.
    2. Shields. [These are pretty hard to classify, since they're the only broad class of system that is hard to explain through current science.]
  4. Active defense systems.
    1. Electronic countermeasures. Electronic equipment designed to foil weapon targeting systems.
    2. B. Decoys. Launched devices designed to foil incoming weapons with false signals.
      1. Electromagnetic decoys. Decoys which emit misleading electromagnetic signals.
    3. Jammer. Electronic equipment designed to foil broadband electromagnetic signals.

This scheme was created by Timothy Miller (Cerebus), and contains some modifications by Erik Max Francis:

  1. Deployment: How the weapons system is initially launched (fired). Note: Do not confuse this description with Guidance.
    1. Active: These weapons deploy themselves upon activation, with the propulsive mechanism integral to the unit; as a class, this includes commonly-termed missiles and torpedoes.
    2. Passive:These weapons are deployed by an external device, launcher or other means.
      1. Gun fired: Deployed by common explosives, as through an artillery piece.
      2. Railgun launched: Deployed by electromagnetic launcher, typically to much higher velocities than possible by Gun-fired or other methods; as such deserves a separate description.
      3. Dropped: Deployed by simply leaving the weapon behind you, without appreciable external impetus.
      4. Hand launched: Thrown, hurled, kicked or otherwise deployed by physical exertion.
    3. Lay in wait: These are fired passively, and activated when they in a given proximity to their target (i.e., "mines")
  2. Guidance: Describes methods of an individual weapon achieving its objective.
    1. Dumb: No post-deployment guidance. Either you aimed right or you didn't.
    2. Smart: Capable of post-deployment guidance of any type (glide, thrust, etc.)
      1. External: Guided by external sensors and control.
        1. Wire guided: Guidance received through trailing wire. Limited in range, but not susceptible to interference.
        2. Signal guided: Less limited in range, but more susceptible to interference.
      2. Internal: Guided by internal sensors.
  3. Kill Type: How the weapons system damages the target.
    1. Kinetic: These weapons carry no warheads, relying on impact energy alone to damage the target.
      1. Single warhead
      2. Scattershot: Weapon segments into shrapnel upon deployment. III-B-1-c types on the other hand delay segmentation until activation
    2. Explosive: These weapons carry explosives of varying types, and rely on on- or near-target detonation to damage the target.
      1. Chemical: Common (or uncommon) chemical explosives.
        1. Blast: Relies on blast effects.
        2. Armor piercing: Self-explanatory.
        3. Shrapnel: Weapons that intentionally shatter or otherwise scatter projectiles to incapacitate or kill. This can be anything from flechette-scattering missiles to hand grenades.
      2. Nuclear: Self-explanatory, includes both fission and fusion devices.
      3. Antimatter
    3. Directed Energy: These weapons transfer energy directly to the target, at range.
      1. Electromagnetic: Lasers and kin (masers, grasers, etc.)
        1. Submunitions: Bomb-pumped lasers
      2. Particle beam: Charged or neutral particles, not to be confused with small-sized railgun-fired projectiles. Typically limited to atomic or sub-atomic particles.
    4. Chemical: Anti-personnel weapons that attempt to poison the biological processes of the target to incapacitate or kill.
    5. Biological: Anti-personnel weapons that attempt to infect the target and incapacitate or kill.
    6. Radiological: Anti-personnel weapons that attempt to expose the target to incapacitating amounts of radiation.
  4. Acquisition: Describes methods of an individual weapon detecting and targeting, its objective.
    1. Active: Weapon emits radiation to detect targets (e.g., radar).
    2. Passive: Weapon passively scans for target emissions (e.g., infrared)
    3. Illumination: Weapons passively scans for an illumination signature painted on target by a third object.
    4. Command : Weapon is issued an attack command by the controlling ship.
  5. Trigger: Generally only for warheads, determines what causes weapon to detonate.
    1. Command: Detonated by command from controlling ship.
    2. Impact: Detonated by contact with target.
    3. Proximity: Detonates within predetermined range of the target.
    4. Timed: Detonates after a pre-determined time.
    5. Check-in: Detonates after the inability to contact a friendly ship after a predetermined period of time.

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