I hope this discussion of MHD energy conversion will not seem out of place in a meeting on advanced reactor concepts. The· fact is that to be useful in space, the MHD generator needs high temperatures of the sort that can only be produced by advanced types of reactors. I hope that today I can make the case, or. at least establish a reasonable possibility, that to be useful in space the advanced reactor concepts in turn need the MHD generator.

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     Although I think many of -you know how an MHD generator works, let me review the basic principles briefly. Figure 1 illustrates the principle and compares it to that of a turbine generator. The basic principles are the same in the two cases. These are that expansion of a gas produces motion of a conductor and the motion of a conductor through a magnetic field generates an electromotive force. In the case of the MHD generator, the gas is itself an electrical conductor and is moved through the magnetic field. Observe that the MHD generator performs the function of both a turbine and a conventional generator. The function that it performs best is that of the turbine. In fact, it is really more useful to think of it as a high temperature turbine rather than as an electrical generator. In practice, an MHD generator would resemble a rocket nozzle with a field coil wrapped around it. It would have no hot, highly stressed, moving parts; no close tolerances; and the only solid parts, namely the walls, are readily accessible for external cooling, as are the walls of a conventional rocket. As a result, it can handle temperatures and pressures like a rocket nozzle and can stand erosive and corrosive atmospheres which would completely destroy any other type of energy conversion device in a very short time. Also as we will see later, it can produce very large amounts of power per unit volume and per unit weight.

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     The primary limitation on how and where one uses an MHD generator is a low temperature limit. This is because at the present time the only way that we are sure is practical for rendering a gas conducting is introducing into it a few tenths of a percent of an alkali metal seed material and then heating it. Results obtained in combustion products, but typical for all gases, are shown on Figure 2. The points are experimental; the solid line is theoretical. Observe that the conductivity is a very steep function of temperature. In practice we find that below about 20000°K, the exact value depending upon just what gas is used, the conductivity becomes too low to be useful. Observe that a few hundred degrees change in temperature can bring about an order of magnitude change in conductivity. This in turn can bring about order of magnitude improvement in the performance of an MHD converter.

     This illustrates why you should not be misled by statements in the literature (or photographs of our devices) into assuming that MHD generators are intrinsically very large and heavy. In our struggle to fit MHD generators into existing technology, we do indeed make them as large and as heavy as the traffic will bear. But the technology which you people are discussing here can move us a very long way up this exponential curve. For example at just about 40000°K in hydrogen an MHD generator containing one cubic meter of volume could generate as much electric power as the sum total of all of the power plants in this country, i.e., about 200,000 megawatts.

     Now given a turbine which has no temperature or power limit and can handle any atmosphere, the next question is, how exactly can it be usefully employed in space? The answer (as is usual for questions of this nature) is that there are a virtual infinity of possibilities. The real problem of course is trying to decide which, if any, of these possibilities arc really worth pursuing. I obviously should not take the time here to discuss them all. So I will discuss rather briefly a few schemes which, I hope, illustrate the range of possibilities.

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     In devising these propulsion schemes, one of the ground rules has been that it should not be necessary to retain fuel within the reactor. Desirable perhaps, but NOT necessary. Figure 3 illustrates a system in which it is obviously not necessary. What we have here is essentially a conventional closed thermodynamic power cycle which is using the propellant as its heat sink. In effect what happens is that heat is transferred between the reactor and the propellant by means of solid surfaces up to the maximum temperature that solids can be used, and above that it is transferred by means of the MHD generator and the accelerator. That is, energy is transferred by convection and conduction up to perhaps 2000°K; and above that, energy and also momentum is transferred electrically. Compare this with concepts such as the glow plug and the coaxial jet in which radiation is used to transfer energy at temperatures above the solids limit. In this respect, I think the MHD scheme has two things to its advantage. First of all, without trying very hard one can make the energy delivered at the electrode wall of an MHO generator at a given temperature be orders of magnitude greater than the energy per unit area delivered by even blackbody radiation. The second advantage of the MHD scheme is that wall materials and structures which are transparent to DC electric power arc a great deal easier to find than materials which are transparent to optical electromagnetic frequencies.

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     Figure 4 is a simplification of the scheme shown in Figure 3. Here the same gas is used as working fluid in the reactor and MHD generator and as the propellant. As a result, the compressor and the heat exchanger are eliminated. Here we depend upon the fact that at a generator exit temperature of 2000 to 2500°K practically all of the fuel will be condensed and can be recovered by a gas-liquid separation technique without cooling the gas any further.

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     Figure 5 illustrates the point that use of an MHO converter can do more than simply provide a way around the fuel containment problem. Shown here is the open cycle propulsion scheme illustrated in Figure 4, except that the power output of the generator is not put back into the propellant but rather used in an external air accelerating device. Obviously this is not a propulsion system for deep space. What we have here is the nuclear MHO analog of a turbo-rocket. The propulsive efficiency of such an arrangement is much higher than that of a rocket alone, assuming you are in the appropriate range of flight velocity through the atmosphere. In the case of a nuclear MHD turbo-rocket this appropriate velocity range could be from zero right up to the satellite velocity. Moreover, an electric ram jet might turn out to be a much easier device to get good performance out of than a comparable chemically fueled ram jet when operating in the hypersonic velocity range. There are a number of reasons for this, but what they all boil down to is just that electricity is a more highly organized or available form of energy than is chemical energy.

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     Figure 6 shows the kind of specific impulse one might expect to get from the type of propulsion systems shown in Figures 4 and 5. This is shown as a function of the pressure ratio across the generator and the top temperature produced by the reactor. "Unaugmented rocket" corresponds to the system shown on Figure 4. The "augmented rocket" corresponds to the system shown on Figure 5. For the latter, the specific impulse shown is a weighted average over the flight velocity from zero up to the satellite velocity, and a range of values is shown corresponding to a range of assumptions about the efficiency of the electric air accelerator, or electric ram jet. η_a / η_t = 1 corresponds to an accelerator efficiency equal to the thermal efficiency of a rocket nozzle, that is about 70%; then η_a / η_t = 0.5 corresponds to an efficiency of about 35%.

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     The closed cycle shown in Figure 3 may also be operated either as a pure rocket or as an air augmented rocket, and the performance that would result is shown in Figure 7. The closed cycle would be a good deal heavier than the open one. However, I believe that in sizes corresponding to a thrust level of 100 tons and up, both systems could be made to have a thrust to weight ratio substantially in excess of one.

     In order to get a specific impulse greater than 2000 to 3000 seconds in space it is necessary to consider a system which uses a radiator. This is true whether one is considering a nuclear-MHD scheme or a nuclear reactor working alone. As is well known, a key, if not the key, to making a system of this type with a reasonable thrust to weight ratio is attaining a high heat rejection temperature. In addition, gains of up to a factor of five can be made simply by making the cycle more efficient. Presently conceived space electric power supplies have a temperature limit set by their reactor and conversion device. By using a gas core reactor and an MHD generator there would no longer be a limit on top cycle temperature. Then the compressor and the radiator temperature could rise accordingly to what is now the top cycle temperature. Eventually it should be possible to also make an MHD compressor, and then only the radiator would be a solids limited device.

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     However, even with "solids limited compressors" we can do orders of magnitudes better than presently conceived electric power systems as is shown on Figure 8. Here power per unit radiator area is displayed vs top cycle temperature for a variety of radiator and generator temperatures. It shows that we ought to be able to do at least a hundred times better than SNAP 8 in terms of power per unit radiator area. Assuming that the weight of all cycle components scales by the same factor, and there is reasonable grounds for supposing that it might, the result would be a propulsion system for· interplanetary flight whlch would be very hard to heat.

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CONCLUSION

     Now that Tom Brogan has shown you something of our present. work, I would like to make one or two further comments arid then summarize.

     First of all I imagine that in the figures that were. shown you observed the very massive field coils in our present devices. I would like to assure this audience again that this is not an inevitable feature. First, the devices you have seen were designed for combustion product gases which produce a rather well defined temperature and hence conductivity. Now as we saw earlier, conductivity is an exponential function of temperature, and the size of the generator is pretty much proportional to the gas conductivity. Secondly, very large reductions in the size and weight of the magnet can be made by cryogenic cooling, and most of these propulsion systems would have an abundance of hydrogen available for this purpose.

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     Figure 17 illustrates these points. On it coil mass is plotted as a function of the size of the generator in terms of gross megawatts of output. The top curve is for a combustion fired generator in which the coil dissipates 30% of the gross power or 6% if the coil is liquid oxygen cooled. The Mark V generator which Tom Brogan discussed falls slightly below this curve because its dissipation is closer to being 50%. You observe that it is a break-even generator. If it had been made much smaller, all of the copper in the world would not have made it self-excite. The lower curve shows what would happen if the gas conductivity and velocity is increased as it would be in a nuclear system at 2500°C using hydrogen as the working gas. Here the dissipation is 10% at room temperature, or 1% if the coil is cooled enough to produce a factor of 10 increase in conductivity. This could easily be accomplished using liquid hydrogen. In fact, much greater gains should be possible. Observe here that as long as the power level is greater than 10 megawatts the coil will weigh on the order of 1 ton. At power levels on the order of 1000 megawatts and up, this corresponds to an extremely small weight per kilowatt of energy handled.

     In summary then, there is no reason why an MHD generator cannot be made light enough. for the kind of high thrust propulsion systems which we have been discussing here.

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     Figure 18 attempts to summarize the kind of systems that we think we can build using an MHD generator and advanced reactors on a map of specific impulse vs engine thrust to weight. The curve labeled "gas core propellant cooled" corresponds to systems as illustrated in Figures 3 and 4. The curve labeled "air breathers" corresponds to a system such as that shown on Figure 5, but includes also schemes using a closed as well as an open cycle. The vertical lines labeled "radiators" correspond to systems such as were discussed in connection with Figure 8. This figure gives the impression that for boosting off the surface of the earth, or any other body, air (or "atmosphere") breathers are hard to beat, and that for interplanetary flight into space, radiating systems are hard to beat if you can get up to power to weight ratios equal to, or exceeding 1 kilowatt per kilogram. However, the main point that I want to make with this curve is just, that by combining an MHD generator with advanced high temperature reactors, we can make propulsion systems whose performance is comparable to what you can hope to get in any other way. In particular they are comparable to, or perhaps better than, what you could hope to get with a gas core reactor alone…and you do not have to solve the fuel containment problem in order to get it!

PREFACE

     The fundamental objective of this work has been to gain an insight into the basic power producing and operational characteristics of the nuclear piston engine, a concept which involves a type of pulsed, quasi-steady-state gaseous core nuclear reactor. The studies have consisted primarily of neutronic and energetic analyses supplemented by some reasonably detailed thermodynamic studies and also by some heat transfer and fluid mechanics calculations.
     This work is not to be construed as being a complete exposé of the nuclear piston engine's complex neutronic and energetic behavior. Nor are the proposed power producing systems to be interpreted as being the ultimate or optimum conditions or configurations. This dissertation is rather a beginning or a foundation for future pulsed, gaseous core reactor studies.
     Nuclear piston engines operating on gaseous fissionable fuel should be capable of providing economically and energetically attractive power generating units.
     A fissionable gas-fueled engine has many of the advantages associated with solid-fueled nuclear reactors but fewer safety and economical limitations. The capital cost per unit power installed (dollars/kwe) should not spiral for small gas-fueled plants to the extent that it does for solid fueled plants. The fuel fabrication (fuel and cladding, spacer grids, etc.) is essentially eliminated; the engineering safeguards and emergency core cooling requirements are reduced significantly.
     As a circulating fuel reactor, the nuclear piston engine's quasi-steady-state power level is capable of being controlled not only by variations in the neutron multiplication factor but also by changes in the loop circulation time. It is shown that such adjustments affect the delayed and photoneutron feedback into the reactor and hence provide an efficient means for controlling the reactor power level.
     The results of the conducted investigations indicate good performance potential for the nuclear piston engine with overall efficiencies of as high as 50% for nuclear piston engine power generating units of from 10 to 50 Mw(e) capacity. Larger plants can be conceptually designed by increasing the number of pistons, with the mechanical complexity and physical size as the probable limiting factors.
The primary uses for such power systems would be for small mobile and fixed ground-based power generation (especially for peaking units for electrical utilities) and also for nautical propulsion and ship power.

CHAPTER I: INTRODUCTION

Description of Engine Operation

     The investigated nuclear piston engines consist of a pulsed; gaseous core reactor enclosed by a moderating-reflecting cylinder and piston assembly and operate on a thermodynamic cycle similar to the internal combustion engine. The primary working fluid is a mixture of uranium hexafluoride, UF₆, and helium, He, gases. Highly enriched UF₆ gas is the reactor fuel. The helium is added to enhance the thermodynamic and heat transfer characteristics of the primary working fluid and also to provide a neutron flux flattening effect in the cylindrical core.

     Two-and four-stroke engines have been studied in which a neutron source is the counterpart of the sparkplug in the internal combustion engine. The piston motions which have been investigated include pure simple harmonic, simple harmonic with dwell periods, and simple harmonic in combination with non-simple harmonic motion.

     Neutronically, the core goes from the subcritical state, through criticality and to the supercritical state during the (intake and) compression stroke(s). Supercriticality is reached before the piston reaches top dead center (TDC), so that the neutron flux can build up to an adequate level to release the required energy as the piston passes TDC.

     The energy released by the fissioning gas can be extracted both as mechanical power and as heat from the circulating gas. External equipment is used to remove fission products, cool the gas, and recycle it back to the pistpn engine. Mechanical power can be directly taken by means of a conventional crankshaft operating at low speeds.

     To utilize the significant amount of available energy in the hot gas, an external heat removal loop can be designed. The high temperature (~1200 to 1600°K) HeUF₆ exhaust gas can be cooled in an HeUF₆-to-He heat exchanger. The heated He (~1000deg;K to 1400deg;K) is then passed either directly through gas turbines or is used in a steam generator to produce steam to drive a turbine.

     The total mechanical plus turbine power per nuclear piston or per cylinder ranges from around 3 to 7 Mw(e) depending on the selected piston engine operating characteristics and the external turbine equipment arrangement. Thus, power generating units of from 10 to 50 Mw(e) capacities would consist of a cluster of 4 to 8 pistons in a nuclear piston engine block, Larger power plants can be conceptually designed by increasing the number of pistons with the mechanical complexity and physical size as the probable limiting factors. Overall efficiencies are as high as 50% implying heating rates of around 6800 BTU/kr-hr. Fuel costs are presently estimated as being below $0.20 per million BTU or around 1.4 mills/kwe-hr (based on fiscal year 1974 costs).

Applications and Highlights of the Nuclear Piston Engine Concept

     Already-developed nuclear reactor concepts like pressurized water reactors (PWRs), boiling water reactors (BWRs), and high temperature gas-cooled reactors (HTGRs) can be economically competitive only when they are incorporated into large capacity power systems. Given the fuel cycle costs and operation and maintenance costs for these reactor concepts, it is their high capital costs which economically prevent them from being used on a scaled-down basis for 20-50-100 Mw(e) units. The cost per unit power installed (dollars/kwe) for scaled-down units operating on these already-developed solid-fueled core concepts would be extremely high.

     A nuclear piston engine power plant, however, will not require the sophisticated and costly engineered safeguards and auxiliary systems associated with the solid-fueled cores of current large capacity nuclear power plants. The inherent safety of an expanding gaseous fuel can be engineered to take the place of many of the functions of the safeguards systems. Hence, while gaseous core, nuclear piston engine power plants would possess relatively high costs per unit power installed as compared to comparably sized fossil-fueled units, their capital costs per unit power installed would be considerably less than for any scaled-down nuclear units operating on current solid-fueled core concepts.

     In addition to decreased capital costs, the nuclear piston engine should possess fuel cycle costs which are about half the fuel cycle costs of most present large capacity nuclear plants. Fuel fabrication costs, transportation costs to and from the fabricator, and transportation costs to and from the reprocessor will all be eliminated. These costs typically comprise from 40 to 50% of the current nuclear fuel cycle costs (based on fiscal year 1974 costs).

     Thus, it would appear as if power production costs for a nuclear piston engine will not only be less than those of conventionally fueled peaking units, but that they should also approach the power production costs of large-scale fossil and large-scale nuclear-fueled plants.

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NASA researchers demonstrate the ability to fuse atoms inside room-temperature metals

      Nuclear fusion is hard to do. It requires extremely high densities and pressures to force the nuclei of elements like hydrogen and helium to overcome their natural inclination to repel each other. On Earth, fusion experiments typically require large, expensive equipment to pull off.
     But researchers at NASA’s Glenn Research Center have now demonstrated a method of inducing nuclear fusion without building a massive stellarator or tokamak. In fact, all they needed was a bit of metal, some hydrogen, and an electron accelerator.
     The team believes that their method, called lattice confinement fusion, could be a potential new power source for deep space missions. They have published their results in two papers in Physical Review C.
     “Lattice confinement” refers to the lattice structure formed by the atoms making up a piece of solid metal. The NASA group used samples of erbium and titanium for their experiments. Under high pressure, a sample was “loaded” with deuterium gas (D + D fusion fuel), an isotope of hydrogen with one proton and one neutron. The metal confines the deuterium nuclei, called deuterons, until it’s time for fusion.
     “During the loading process, the metal lattice starts breaking apart in order to hold the deuterium gas,” says Theresa Benyo, an analytical physicist and nuclear diagnostics lead on the project. “The result is more like a powder.” At that point, the metal is ready for the next step: overcoming the mutual electrostatic repulsion between the positively-charged deuteron nuclei, the so-called Coulomb barrier.

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     To overcome that barrier requires a sequence of particle collisions. First, an electron accelerator speeds up and slams electrons into a nearby target made of tungsten. The collision between beam and target creates high-energy photons, just like in a conventional X-ray machine. The photons are focused and directed into the deuteron-loaded erbium or titanium sample. When a photon hits a deuteron within the metal, it splits it apart into an energetic proton and neutron. Then the neutron collides with another deuteron, accelerating it.
     At the end of this process of collisions and interactions, you’re left with a deuteron that’s moving with enough energy to overcome the Coulomb barrier and fuse with another deuteron in the lattice.
     Key to this process is an effect called electron screening, or the shielding effect. Even with very energetic deuterons hurtling around, the Coulomb barrier can still be enough to prevent fusion. But the lattice helps again. “The electrons in the metal lattice form a screen around the stationary deuteron,” says Benyo. The electrons’ negative charge shields the energetic deuteron from the repulsive effects of the target deuteron’s positive charge until the nuclei are very close, maximizing the amount of energy that can be used to fuse.
     Aside from deuteron-deuteron fusion, the NASA group found evidence of what are known as Oppenheimer-Phillips stripping reactions. Sometimes, rather than fusing with another deuteron, the energetic deuteron would collide with one of lattice’s metal atoms, either creating an isotope or converting the atom to a new element. The team found that both fusion and stripping reactions produced useable energy.

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     “What we did was not cold fusion,” says Lawrence Forsley, a senior lead experimental physicist for the project. Cold fusion, the idea that fusion can occur at relatively low energies in room-temperature materials, is viewed with skepticism by the vast majority of physicists. Forsley stresses this is hot fusion, but “We’ve come up with a new way of driving it.”
     “Lattice confinement fusion initially has lower temperatures and pressures” than something like a tokamak, says Benyo. But “where the actual deuteron-deuteron fusion takes place is in these very hot, energetic locations.” Benyo says that when she would handle samples after an experiment, they were very warm. That warmth is partially from the fusion, but the energetic photons initiating the process also contribute heat.
     There’s still plenty of research to be done by the NASA team. Now they’ve demonstrated nuclear fusion, the next step is to create reactions that are more efficient and more numerous. When two deuterons fuse, they create either a proton and tritium (a hydrogen atom with two neutrons), or helium-3 and a neutron. In the latter case, that extra neutron can start the process over again, allowing two more deuterons to fuse. The team plans to experiment with ways to coax more consistent and sustained reactions in the metal.
     Benyo says that the ultimate goal is still to be able to power a deep-space mission with lattice confinement fusion. Power, space, and weight are all at a premium on a spacecraft, and this method of fusion offers a potentially reliable source for craft operating in places where solar panels may not be useable, for example. And of course, what works in space could be used on Earth.

NASA Detects Lattice Confinement Fusion

A team of NASA researchers seeking a new energy source for deep-space exploration missions, recently revealed a method for triggering nuclear fusion in the space between the atoms of a metal solid.

Their research was published in two peer-reviewed papers in the top journal in the field, Physical Review C, Volume 101 (April, 2020): “Nuclear fusion reactions in deuterated metals” and “Novel nuclear reactions observed in bremsstrahlung-irradiated deuterated metals.”

Nuclear fusion is a process that produces energy when two nuclei join to form a heavier nucleus. “Scientists are interested in fusion, because it could generate enormous amounts of energy without creating long-lasting radioactive byproducts,” said Theresa Benyo, Ph.D., of NASA’s Glenn Research Center. “However, conventional fusion reactions are difficult to achieve and sustain because they rely on temperatures so extreme to overcome the strong electrostatic repulsion between positively charged nuclei that the process has been impractical.”

Called Lattice Confinement Fusion, the method NASA revealed accomplishes fusion reactions with the fuel (deuterium, a widely available non-radioactive hydrogen isotope composed of a proton, neutron, and electron, and denoted “D”) confined in the space between the atoms of a metal solid. In previous fusion research such as inertial confinement fusion, fuel (such as deuterium/tritium) is compressed to extremely high levels but for only a short, nano-second period of time, when fusion can occur. In magnetic confinement fusion, the fuel is heated in a plasma to temperatures much higher than those at the center of the Sun. In the new method, conditions sufficient for fusion are created in the confines of the metal lattice that is held at ambient temperature. While the metal lattice, loaded with deuterium fuel, may initially appear to be at room temperature, the new method creates an energetic environment inside the lattice where individual atoms achieve equivalent fusion-level kinetic energies.

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A metal such as erbium is “deuterated” or loaded with deuterium atoms, “deuterons,” packing the fuel a billion times denser than in magnetic confinement (tokamak) fusion reactors. In the new method, a neutron source “heats” or accelerates deuterons sufficiently such that when colliding with a neighboring deuteron it causes D-D fusion reactions. In the current experiments, the neutrons were created through photodissociation of deuterons via exposure to 2.9+MeV gamma (energetic X-ray) beam. Upon irradiation, some of the fuel deuterons dissociate resulting in both the needed energetic neutrons and protons. In addition to measuring fusion reaction neutrons, the Glenn Team also observed the production of even more energetic neutrons which is evidence of boosted fusion reactions or screened Oppenheimer-Phillips (O-P) nuclear stripping reactions with the metal lattice atoms. Either reaction opens a path to process scaling.

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Illustration of the main elements of the lattice confinement fusion process observed

     In Part (A), a lattice of erbium is loaded with deuterium atoms (i.e., erbium deuteride), which exist here as deuterons. Upon irradiation with a photon beam, a deuteron dissociates, and the neutron and proton are ejected. The ejected neutron collides with another deuteron, accelerating it as an energetic “d*” as seen in (B) and (D). The “d*” induces either screened fusion (C) or screened Oppenheimer-Phillips (O-P) stripping reactions (E).

     In (C), the energetic “d*” collides with a static deuteron “d” in the lattice, and they fuse together. This fusion reaction releases either a neutron and helium-3 (shown) or a proton and tritium. These fusion products may also react in subsequent nuclear reactions, releasing more energy.

     In (E), a proton is stripped from an energetic “d*” and is captured by an erbium (Er) atom, which is then converted to a different element, thulium (Tm). If the neutron instead is captured by Er, a new isotope of Er is formed (not shown).

     More details are in this paper

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A novel feature of the new process is the critical role played by metal lattice electrons whose negative charges help “screen” the positively charged deuterons. Such screening allows adjacent fuel nuclei to approach one another more closely, reducing the chance they simply scatter off one another, and increasing the likelihood that they tunnel through the electrostatic barrier promoting fusion. This is according to the theory developed by the project’s theoretical physicist, Vladimir Pines, Ph.D, of PineSci.

“The current findings open a new path for initiating fusion reactions for further study within the scientific community. However, the reaction rates need to be increased substantially to achieve appreciable power levels, which may be possible utilizing various reaction multiplication methods under consideration,” said Glenn’s Bruce Steinetz, Ph.D., the NASA project principal investigator.

“The key to this discovery has been the talented, multi-disciplinary team that NASA Glenn assembled to investigate temperature anomalies and material transmutations that had been observed with highly deuterated metals,” said Leonard Dudzinski, Chief Technologist for Planetary Science, who supported the research. “We will need that approach to solve significant engineering challenges before a practical application can be designed.”

With more study and development, future applications could include power systems for long-duration space exploration missions or in-space propulsion. It also could be used on Earth for electrical power or creating medical isotopes for nuclear medicine.

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      But as my old mucker Craig Buckley (28 years experience in the Hydrogen Storage research field) pointed out to me all those years ago at Salford, even at high pressure there simply aren't that many deuterons per metal atom.

     So the deuterons, which are very small, are nowhere near one another and will reside in the interatomic voids. If you want them to fuse you have to do something to smash them together. They are not stuffed together in the alloy so can't fuse because there are 10^-10 m apart

      Any reaction that needs solid state materials is at best a fancy RTG. It’s not a Propulsion system power source for anything other than slow electric drives.

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Casimir batteries and engines

A common assumption is that the Casimir force is of little practical use; the argument is made that the only way to actually gain energy from the two plates is to allow them to come together (getting them apart again would then require more energy), and therefore it is a one-use-only tiny force in nature. In 1984 Robert Forward published work showing how a "vacuum-fluctuation battery" could be constructed. The battery can be recharged by making the electrical forces slightly stronger than the Casimir force to reexpand the plates. (so it is more of an advanced capacitor or rechargable battery than it is a power source)

In 1995 and 1998 Maclay et al. published the first models of a microelectromechanical system (MEMS) with Casimir forces. While not exploiting the Casimir force for useful work, the papers drew attention from the MEMS community due to the revelation that Casimir effect needs to be considered as a vital factor in the future design of MEMS. In particular, Casimir effect might be the critical factor in the stiction failure of MEMS.

In 1999 Pinto, a former scientist at NASA's Jet Propulsion Laboratory at Caltech in Pasadena, published in Physical Review his Gedankenexperiment for a "Casimir engine". The paper showed that continuous positive net exchange of energy from the Casimir effect was possible, even stating in the abstract "In the event of no other alternative explanations, one should conclude that major technological advances in the area of endless, by-product free-energy production could be achieved." In 2001 Capasso et al. showed how the force can be used to control the mechanical motion of a MEMS device, The researchers suspended a polysilicon plate from a torsional rod – a twisting horizontal bar just a few microns in diameter. When they brought a metallized sphere close up to the plate, the attractive Casimir force between the two objects made the plate rotate. They also studied the dynamical behaviour of the MEMS device by making the plate oscillate. The Casimir force reduced the rate of oscillation and led to nonlinear phenomena, such as hysteresis and bistability in the frequency response of the oscillator. According to the team, the system’s behaviour agreed well with theoretical calculations.

Despite this and several similar peer reviewed papers, there is not a consensus as to whether such devices can produce a continuous output of work. Garret Moddel at University of Colorado has highlighted that he believes such devices hinge on the assumption that the Casimir force is a nonconservative force, he argues that there is sufficient evidence (e.g. analysis by Scandurra (2001)) to say that the Casimir effect is a conservative force and therefore even though such an engine can exploit the Casimir force for useful work it cannot produce more output energy then has been input into the system.

In 2008 DARPA solicited research proposals in the area of Casimir Effect Enhancement (CEE). The goal of the program is to develop new methods to control and manipulate attractive and repulsive forces at surfaces based on engineering of the Casimir Force.

A 2008 patent by Haisch and Moddel details a device that is able to extract power from zero-point fluctuations using a gas that circulates through a Casimir cavity. As gas atoms circulate around the system they enter the cavity. Upon entering the electrons spin down to release energy via electromagnetic radiation. This radiation is then extracted by an absorber. On exiting the cavity the ambient vacuum fluctuations (i.e. the zero-point field) impart energy on the electrons to return the orbitals to previous energy levels, as predicted by Senitzky (1960). The gas then goes through a pump and flows through the system again. A published test of this concept by Moddel was performed in 2012 and seemed to give excess energy that could not be attributed to another source. However it has not been conclusively shown to be from zero-point energy and the theory requires further investigation.

(ed note: see original article for links to references)

8.19 The vacuum energy drive

     The most powerful theories in physics today are quantum theory and the theories of special and general relativity. Unfortunately, those theories are not totally consistent with each other. If we calculate the energy associated with an absence of matter—the "vacuum state"—we do not, as common sense would suggest, get zero. Instead, quantum theory assigns a specific energy value to a vacuum.

     In classical thinking, one could argue that the zero point of energy is arbitrary, so we could simply start measuring energies from the vacuum energy value. However, if we accept general relativity that option is denied to us. Energy, of any form, produces spacetime curvature, and we are therefore not allowed to redefine the origin of the energy scale. Once this is accepted, the energy of the vacuum cannot be talked out of existence. It is real, and when we calculate it we get a large positive value per unit volume.

     How large?

     Richard Feynman addressed the question of the vacuum energy value and computed an estimate for the equivalent mass per unit volume. The estimate came out as two billion tons per cubic centimeter. The energy in two billion tons of matter is more than enough to boil all Earth's oceans.

     Is there any possibility that the vacuum energy could be tapped for useful purposes? Robert Forward has proposed a mechanism, based upon a real physical phenomenon known as the Casimir Effect. I think it would work, but the energy produced is small. The well-publicized mechanisms of others, such as Harold Puthoff, for extracting vacuum energy leave me totally unpersuaded.

     Science fiction that admits it is science fiction is another matter. According to Arthur Clarke, I was the first person to employ the idea of the vacuum energy drive in fictional form, in the story "All the Colors of the Vacuum" (Sheffield, 1981). Clarke employed one in The Songs of Distant Earth (Clarke, 1986). Not surprisingly, there was a certain amount of hand-waving on both Clarke's part and mine as to how the vacuum energy drive was implemented. If the ship can obtain energy from the vacuum, and mass and energy are equivalent, why can't the ship get the reaction mass, too? How does the ship avoid being slowed when it takes on energy, which has an equivalent mass that is presumably at rest? If the vacuum energy is the energy of the ground state, to what new state does the vacuum go, after energy is extracted?

     Good questions. Look on them as an opportunity. There must be good science-fictional answers to go with them.

      McAndrew laughed, a humorless bark. "I'll tell you why, Jeanie. You flew the Merganser. Tell me how the drive worked."

     "Well, the mass plate at the front balanced the acceleration, so we didn't get any sensation of fifty gee." I shrugged. "I didn't work out the math for myself, but I'm sure I could have if I felt like it."

     I could have, too. I was a bit rusty, but you never lose the basics once you have them planted deep enough in your head.

     "I don't mean the balancing mechanism, that was just common sense." He shook his head. "I mean the drive. Didn't it occur to you that we were accelerating a mass of trillions of tons at fifty gee? If you work out the mass conversion rate you will need, you find that even with an ideal photon drive you'll consume the whole mass in a few days. The Merganser got its drive by accelerating charged particles up to within millimeters a second of light speed. That was the reaction mass. But how did it get the energy to do it?"

     I felt like telling him that when I had been on Merganser there had been other details—such as survival—on my mind. I thought for a few moments, then shook my head.

     "You can't get more energy out of matter than the rest mass energy, I know that. But you're telling me that the drives on Merganser and Hoatzin do it. That Einstein was wrong."

     "No!" McAndrew looked horrified at the thought that he might have been criticizing one of his senior idols. "All I've done is build on what Einstein did. Look, you've done a fair amount of quantum mechanics. You know that when you calculate the energy for the vacuum state of a system you don't get zero. You get a positive value."

     I had a hazy recollection of a formula swimming back across the years. What was it? h/4πw, said a distant voice.

     "But you can set that to zero!" I was proud at remembering so much. "The zero point of energy is arbitrary."

     "In quantum theory it is. But not in general relativity." McAndrew was beating back my mental defenses. As usual when I spoke with him on theoretical subjects, I began to feel I would know less at the end of the conversation than I did at the beginning.

     "In general relativity," he went on, "energy implies space-time curvature. If the zero-point energy is not zero, the vacuum self-energy is real. It can be tapped, if you know what you are doing. That's where Hoatzin draws its energy. The reaction mass it needs is very small. You can get that by scooping up matter as you go along, or if you prefer it you can use a fraction—a very small fraction—of the mass plate."

The first suggestion that vacuum energies might be used for propulsion appears to have been made by Shinichi Seike in 1969. (‘Quantum electric space vehicle’; 8th Symposium on Space Technology and Science, Tokyo.)

Ten years later, H. D. Froning of McDonnell Douglas Astronautics introduced the idea at the British Interplanetary Society’s Interstellar Studies Conference, London (September 1979) and followed it up with two papers: ‘Propulsion Requirements for a Quantum Interstellar Ramjet’ (JBIS, Vol. 33,1980) and ‘Investigation of a Quantum Ramjet for Interstellar Flight’ (AIAA Preprint 81-1534, 1981).

Ignoring the countless inventors of unspecified ‘space drives,’ the first person to use the idea in fiction appears to have been Dr Charles Sheffield, Chief Scientist of Earth Satellite Corporation; he discusses the theoretical basis of the ‘quantum drive’ (or, as he has named it, ‘vacuum energy drive’) in his novel The McAndrew Chronicles (Analog magazine 1981; Tor, 1983).

An admittedly naive calculation by Richard Feynman suggests that every cubic centimetre of vacuum contains enough energy to boil all the oceans of Earth. Another estimate by John Wheeler gives a value a mere seventy-nine orders of magnitude larger. When two of the world’s greatest physicists disagree by a little matter of seventy-nine zeros, the rest of us may be excused a certain scepticism; but it’s at least an interesting thought that the vacuum inside an ordinary light bulb contains enough energy to destroy the galaxy … and perhaps, with a little extra effort, the cosmos.

In what may hopefully be an historic paper (‘Extracting electrical energy from the vacuum by cohesion of charged foliated conductors,’ Physical Review, Vol. 30B, pp. 1700-1702, 15 August 1984) Dr Robert L. Forward of the Hughes Research Labs has shown that at least a minute fraction of this energy can be tapped. If it can be harnessed for propulsion by anyone besides science-fiction writers, the purely engineering problems of interstellar — or even intergalactic — flight would be solved.

• 

Primordial black holes

R(am)	M(Mt)	kT(GeV)	P(PW)	P/c2(g/sec)	L(yrs)
0.16	0.108	98.1	5519	61400	≲0.04
0.3	0.202	52.3	1527	17000	≲0.12
0.6	0.404	26.2	367	4090	1
0.9	0.606	17.4	160	1780	3.5
1.0	0.673	15.7	129	1430	5
1.5	1.01	10.5	56.2	626	16—17
2.0	1.35	7.85	31.3	348	39—41
2.5	1.68	6.28	19.8	221	75—80
2.6	1.75	6.04	18.3	204	85—91
2.7	1.82	5.82	16.9	189	95—102
2.8	1.89	5.61	15.7	175	106—114
2.9	1.95	5.41	14.6	163	118—127
3.0	2.02	5.23	13.7	152	130—140
5.8	3.91	2.71	3.50	38.9	941—1060
5.9	3.97	2.66	3.37	37.5	991—1117
6.0	4.04	2.62	3.26	36.2	1042—1177
6.9	4.65	2.28	2.43	27.1	1585—1814
7.0	4.71	2.24	2.36	26.2	1655—1897
10.0	6.73	1.57	1.11	12.3	4824—5763

Abstract

Artificial Singularity Power (ASP) engines generate energy through the evaporation of modest sized (10⁸-10¹¹ kg) black holes created through artificial means. This paper discusses the design and potential advantages of such systems for powering large space colonies, terraforming planets, and propelling starships. The possibility of detecting advanced extraterrestrial civilizations via the optical signature of ASP systems is examined. Speculation as to possible cosmological consequences of widespread employment of ASP engines is considered.

Introduction

According to a theory advanced by Stephen Hawking [1] in 1974, black holes evaporate at a rate given by:

t_ev = (5120π)t_P(m/m_P)³ (1)

where t_ev is the time it takes for the black hole to evaporate, t_P is the Planck time (5.39e-44 s), m is the mass of the black hole in kilograms, and m_P is the Planck mass (2.18e-8 kg) [2]

Hawking considered the case of black holes formed by the collapse of stars, which need to be at least ~3 solar masses to occur naturally. For such a black hole, equation 1 yields an evaporation time of 5e68 years, far longer than the expected life of the universe. In fact, evaporation would never happen, because the black hole would gain energy, and thus mass, by drawing in cosmic background radiation at a rate faster than its own insignificant rate of radiated power.

However it can be seen from examining equation (1) that the evaporation rate goes inversely with the cube of singularity, which means that the emitted power (=mc²/t_ev) goes inverse with the square of the mass. Thus if the singularity could be made small enough, very large amounts of power could theoretically be produced.

This possibility was quickly grasped by science fiction writers, and such propulsion systems were included by Arthur C. Clarke in his 1976 novel Imperial Earth [3] and Charles Sheffield in his 1978 short story “Killing Vector.” [4]

Such systems did not receive serious technical analysis however, until 2009, when it was examined by Louis Crane and Shawn Westmoreland, both then of Kansas State University, in their seminal paper “Are Black Hole Starships Possible?” [5]

In their paper, Crane and Westmoreland focused on the idea of using small artificial black holes powerful enough to drive a starship to interstellar-class velocities yet long-lived enough to last the voyage. They identified a “sweet spot” for such “Black Hole Starships” (BHS) with masses on the order of 2×10⁹ kg, which they said would have lifetimes on order of 130 years, yet yield power of about 13,700 TW. They proposed to use some kind of parabolic reflector to reflect this radiation, resulting in a photon rocket. The ideal thrust T of a rocket with jet power P and exhaust velocity v is given by:

T = 2P/v (2)

So with T = 13,700 TW and v=c = 3e8 m/s, the thrust would be 8.6e7 N. Assuming that the payload spacecraft had a mass of 1e9 kg, this would accelerate the ship at a rate of a=8.6e7/3e9 = 2.8e-2 m/s². Accelerating at this rate, such a ship would reach about 30% the speed of light in 100 years.

There are a number of problems with this scheme. In the first place, the claimed acceleration is on the low side. Furthermore their math appears to be incorrect. A 2e9 kg singularity would only generate about 270 TW, or 1/50th as much as their estimate, reducing thrust by a factor of 50 (although it would last about 20,000 years). These problems could be readily remedied, however, by using a smaller singularity and a smaller ship. For example a singularity with a mass of 2e8 kg would produce a power of 26,900 TW. Assuming a ship with a mass of 1e8 kg, an acceleration of 0.6 m/s² could be achieved, allowing 60% the speed of light to be achieved in 10 years. The singularity would only have a lifetime of 21 years. However it could be maintained by being constantly fed mass at a rate of about 0.33 kg/s.

A bigger problem is that a 1e9 kg singularity would produce radiation with a characteristic temperature of 9 GeV, increasing in inverse proportion to the singularity mass. So for example a 1e8 kg singularity would produce gamma rays with energies of 90 GeV (i.e. for Temperature, T, in electron volts, T = 9e18/m.) There is no known way to reflect such high energy photons. So at this point the parabolic reflector required for the black hole starship photon engine is science fiction.

Yet another problem is the manufacture of the black hole. Crane and Westmoreland suggest that it could be done using converging gamma ray lasers. To make a 1e9 kg unit, they suggested a “high-efficiency square solar panel a few hundred km on each side, in a circular orbit about the sun at a distance of 1,000,000 km” to provide the necessary energy. A rough calculation indicates the implied power of this system from this specification is on the order of 10⁶ TW, or about 100,000 times the current rate used by human civilization. As an alternative construction technique, they also suggest accelerating large masses to relativistic velocities and then colliding them. The density of these masses would be multiplied both by relativistic mass increase and length contraction. However the energy required to do this would still equal the combined masses times the speed of light squared. While this technique would eliminate the need for giant gamma ray lasers, the same huge power requirement would still present itself.

In what follows, we will examine possible solutions for the above identified problems.

Advanced Singularity Engines

In MKS units, equation (1) can be rewritten as:

t_ev = 8.37e-15 m³ (3)

This implies that the power, P, in Watts, emitted by the singularity is given by:

P = 1.08e33/m² (4)

The results of these two equations are shown in Fig. 1.

• 

No credible concept is available to enable a lightweight parabolic reflector of the sort needed to enable the Black Hole Starship. But we can propose a powerful and potentially very useful system by dropping the requirement for starship-relevant thrust to weight ratios. Instead let us consider the use of ASP engines to create an artificial sun.

Consider a 1e8 kg ASP engine. As shown in Fig 1, it would produce a power of 1.08e8 Gigawatts. Such an engine, if left along, would only have a lifetime of 2.65 years, but it could be maintained by a constant feed of about 3 kg/s of mass. We can’t reflect its radiation, but we can absorb it with a sufficiently thick material screen. So let’s surround it with a spherical shell of graphite with a radius of 40 km and a thickness of 1.5 m. At a distance of 40 km, the intensity of the radiation will be about 5 MW/m², which the graphite sphere can radiate into space with a black body temperature of 3000 K. This is about the same temperature as the surface of a type M red dwarf star. We estimate that graphite has an attenuation length for high energy gamma rays of about 15 cm, so that 1.5 m of graphite (equivalent shielding to 5 m of water or half the Earth’s atmosphere) will attenuate the gamma radiation by ten factors of e, or 20,000. The light will then radiate out further, dropping in intensity with the square of the distance, reaching typical Earth sunlight intensities of 1 kW/m² at a distance of about 3000 km from the center.

The mass of the artificial star will be about 10¹⁴ kg (that’s the mass of the graphite shell, compared to which the singularity is insignificant.). As large as this is, however, it is still tiny compared to that of a planet, or even the Earth’s Moon (which is 7.35e22 kg). So, no planet would orbit such a little star. Instead, if we wanted to terraform a cold world, we would put the mini-star in orbit around it.

The preferable orbital altitude of the ASP mini-star of 3000 km altitude in the above cited example was dictated by the power level of the singularity. Such a unit would be sufficient to provide all the light and heat necessary to terraform an otherwise sunless planet the size of Mars. Lower power units incorporating larger singularities but much smaller graphite shells are also feasible. (Shell mass is proportional to system power.) These are illustrated in Table 1.

The high-powered units listed in Table 1 with singularity masses in the 1e8 to 1e9 kg range are suitable to serve as mini-suns orbiting planets, moons or asteroids, with the characteristic radius of such terraforming candidates being about the same as the indicated orbital altitude. The larger units, with lower power and singularity masses above 1e10 kg are more appropriate for space colonies.

Consider an ASP mini-sun with a singularity mass of 3.16e10 kg positioned in the center of a cylinder with a radius of 10 km and a length of 20 km. The cylinder is rotating at a rate of 0.0316 radians per second, which provides it with 1 g or artificial gravity. Let’s say the cylinder is made of material with an areal density of 1000 kg per square meter. In this case it will experience an outward pressure of 10⁴ pascals, or about 1.47 psi, due to outward acceleration. If the cylinder were made of solid Kevlar (density = 1000 kg/m³) it would be about 1 m thick. So the hoop stress on it would be 1.47*(10,000)/1 = 14,700 psi, which is less than a tenth the yield stress of Kevlar. Or put another way, 10 cm of Kevlar would do the job of carrying the hoop stress, and the rest of mass load could be anything, including habitations. If the whole interior of the cylinder were covered with photovoltaic panels with an efficiency of 10 percent, 100 GWe of power would be available for use of the inhabitants of the space colony, which would have an area of 1,256 square kilometers. The mini-sun powering it would have a lifetime of 84 million years, without refueling. Much larger space colonies (i.e, with radii over ~100 km) would not be possible however, unless stronger materials become available, as the hoop stress would become too great.

Both of these approaches seem potentially viable in principle. However we note that the space colony approach cited requires a singularity some 300 times more massive than the approach of putting a 1e8 kg mini-sun in orbit around a planet, which yields 4π(3000)² = 100 million square kilometers of habitable area, or about 80,000 times as much land. Furthermore, the planet comes with vast supplies of matter of every type, whereas the space colony needs to import everything.

Building Singularities

Reducing the size of the required singularity by a factor of 10 from 1e9 to 1e8 kg improves feasibility of the ASP concept somewhat, but we need to do much better. Fortunately there is a way to do so.

If we examine equation (3), we can see that the expected lifetime of a 1000 kg singularity would be about 8.37 x 10^-6 s. In this amount of time, light can travel about 250 m. and an object traveling at half the speed of light 125 m. If a sphere with a radius of 125 m were filled with steel it would contain about 8 x 10¹⁰ kg, or about 100 times what we need for our 1e8 kg ASP singularity. In fact, it turns out that if the initial singularity is as small as about 200 kg, and fired into a mass of steel, it will gain mass much faster than it losses it, and eventually grow into a singularity as massive as the steel provided.

By using this technique we can reduce the amount of energy required to form the required singularity by about 7 orders of magnitude compared to Crane and Westmoreland’s estimate. So instead of needing a 10⁶ TW system, a 100 GW gamma ray laser array might do the trick. Alternatively, accelerating two 200 kg masses to near light speed would require 3.6e7 TJ, or 10,000 TW-hours of energy. This is about the energy humanity currently uses in 20 days. We still don’t know how to do it, but reducing the scale of the required operation by a factor of 10 million certainly helps.

ASP Starships

We now return to the subject of ASP starships. In the absence of a gamma ray reflector, we are left with using solid material to absorb the gamma rays and other energetic particles and re-radiate their energy as heat. (Using magnetic fields to try to contain and reflect GeV-class charged particles that form a portion of the Hawking radiation won’t work because the required fields would be too strong and too extensive, and the magnets to generate them would be exposed to massive heating by gamma radiation.)

Fortunately, we don’t need to absorb all the radiation in the absorber/reflector, we only need to absorb enough to get it hot. So let’s say that we position a graphite hemispherical screen to one side of a 1e8 kg ASP singularity, but instead of making it 1.5 m thick, we make it 0.75 mm thick. At that thickness it will only absorb about 5 percent of the radiation that hits it, the rest will pass right through. So we have 5e6 GW of useful energy, which we want to reduce to 5 MW/m² in order for the graphite to be kept at ~3000 K where it can survive. The radius will be about 9 km, and the mass of the graphite hemisphere will be about 6e8 kg. A thin solar sail like parabolic reflector with an area 50 times as great and the carbon hemisphere but a thickness 1/500th (i.e. 1.5 microns) as great would be positioned in front of the hemisphere, adding another 0.6 e8 kg to the system, which then plus the singularity and the 1e8 kg ship might be 7.6e8 kg in all. Thrust will be 0.67e8 N, so the ship would accelerate at a speed of 0.67/7.6 = 0.09 m/s², allowing it to reach 10 percent the speed of light in about 11 years.

Going much faster would become increasingly difficult, because using only 5% of the energy of the singularity mass would give the system an effective exhaust velocity of about 0.22 c. Higher efficiencies might be possible if a significant fraction of the Hawking radiation came off as charged particles, allowing a thin thermal screen to capture a larger fraction of the total available energy. In this case, effective exhaust velocity would go as c times the square root of the achieved energy efficiency. But sticking with our 5% efficiency, if we wanted to reach 0.22 c we could, but we would require a mass ratio of 2.7, meaning we would need about 1.5e9 kg of propellant to feed into the ASP engine, whose mass would decrease our average acceleration by about a factor of two over the burn, meaning we would take about 40 years to reach 20 percent the speed of light.

Detecting ET

The above analysis suggests that if ASP technology is possible, using it to terraform cold planets with orbital mini-suns will be the preferred approach. Orbiting (possibly isolated) cold worlds at distances of thousands of kilometers, and possessing 3000 K type M red dwarf star spectra, potentially with gamma radiation in excess of normal stellar expectations, it is possible that such objects could be detectable.

Indeed, one of the primary reasons to speculate on the design of ASP engines right now is to try to identify their likely signature. We are far away from being able to build such things. But the human race is only a few hundred thousand years old, and human civilization is just a few thousand years. In 1905 the revolutionary HMS Dreadnought was launched, displacing 18,000 tons. Today ships 5 times that size are common. So it is hardly unthinkable that in a century or two we will have spacecraft in the million ton (10⁹ kg) class. Advanced extraterrestrial civilizations may have reached our current technological level millions or even billions of years ago. So they have had plenty of time to develop every conceivable technology. If we can think it, they can build it, and if doing so would offer them major advantages, they probably have. Thus, looking for large energetic artifacts such as Dyson Spheres [6], starships [7,8], or terraformed planets [9] is potentially a promising way to carry out the SETI search, as unlike radio SETI, it requires no mutual understanding of communication conventions. Given the capabilities the ASP technology would offer any species seeking to expand it prospects by illuminating and terraforming numerous new worlds, such systems may actually be quite common.

ASP starships are also feasible and might be detectable as well. However the durations of starship flights would be measured in decades or centuries, while terraformed worlds could be perpetual. Furthermore, once settled, trade between solar systems could much more readily be accomplished by the exchange of intellectual property via radio than by physical transport. As a result, the amount of flight traffic will be limited. In addition, there could be opportunities for employment of many ASP terraforming engines within a single solar system. For example, within our own solar system there are seven worlds of planetary size (Mars, Ceres, Ganymede, Calisto, Titan, Triton, and Pluto) whose terraforming could be enhanced or enabled by ASP systems, not to mention hundreds of smaller but still considerable moons and asteroids, and potentially thousands of artificial space colonies as well. Therefore the number of ASP terraforming engines in operation in the universe at any one time most likely far exceeds those being used for starship propulsion. It would therefore appear advantageous to focus the ASP SETI search effort on such systems.

Proxima Centauri is a type M red dwarf with a surface temperature of 3000 K. It therefore has a black body spectrum similar to that of the 3000 K graphite shell of our proposed ASP mini-sun discussed above. The difference however is that it has about 1 million times the power, so that an ASP engine placed 4.2 light years (Proxima Centauri’s distance) from Earth would have the visual brightness as a star like Proxima Centauri positioned 4,200 light years away. Put another way, Proxima Centauri has a visual magnitude of 11. It takes 5 magnitudes to equal a 100 fold drop in power, so our ASP engine would have a visual magnitude of 26 at 4.2 light years, and magnitude 31 at 42 light years. The limit of optical detection of the Hubble Space Telescope is magnitude 31. So HST would be able to see our proposed ASP engine out to a distance of about 50 light years, within which there are some 1,500 stellar systems.

Consequently ASP engines may already have been imaged by Hubble, appearing on photographs as unremarkable dim objects assumed to be far away. These should be subjected to study to see if any of them exhibit parallax. If they do, this would show that they are actually nearby objects of much lower power than stars. Further evidence of artificial origin could be provided if they were found to exhibit a periodic Doppler shift, as would occur if they were in orbit around a planetary body. An anomalous gamma ray signature could be present as well.

I suggest we have a look.

Cosmological Implications

One of the great mysteries of science is why the laws of the universe are so friendly to life. Indeed, it can be readily shown that if any one of most of the twenty or so apparently arbitrary fundamental constants of nature differed from their actual value by even a small amount, life would be impossible [9]. Some have attempted to answer this conundrum by claiming that there is nothing to be explained because there are an infinite number of universes; we just happen to live in the odd one where life is possible. This multiverse theory answer is absurd, as it could just as well be used to avoid explaining anything. For example take the questions, why did the Titanic sink/it snow heavily last winter/the sun rise this morning/the moon form/the chicken cross the road? These can all also be answered by saying “no reason, it other universes they didn’t.” The Anthropic Principle reply, to the effect of “clearly they had to, or you wouldn’t be asking the question” is equally useless.

Clearly a better explanation is required. One attempt at such an actual causal theory was put forth circa 1992 by physicist Lee Smolin [10], who says that daughter universes are formed by black holes created within mother universes. This has a ring of truth to it, because a universe, like a black hole, is something that you can’t leave. Well, says Smolin, in that case, since black holes are formed from collapsed stars, the universes that have the most stars will have the most progeny. So to have progeny a universe must have physical laws that allow for the creation of stars. This would narrow the permissible range of the fundamental constants by quite a bit. Furthermore, let’s say that daughter universes have physical laws that are close to, but slightly varied from that of their mother universes. In that case, a kind of statistical natural selection would occur, overwhelmingly favoring the prevalence of star-friendly physical laws as one generation of universes follows another.

But the laws of the universe don’t merely favor stars, they favor life, which certainly requires stars, but also planets, water, organic and redox chemistry, and a whole lot more. Smolin’s theory gets us physical laws friendly to stars. How do we get to life?

Reviewing an early draft of Smolin’s book in 1994, Crane offered the suggestion [11] that if advanced civilizations make black holes, they also make universes, and therefore universes that create advanced civilizations would have much more progeny than those that merely make stars. Thus the black hole origin theory would explain why the laws of the universe are not only friendly to life, but the development of intelligence and advanced technology as well. Universes creates life because life creates universes. This result is consistent with complexity theory, which holds that if A is necessary to B, then B has a role in causing A.

These are very interesting speculations. So let us ask, what would we see if our universe was created as a Smolin black hole, and how might we differentiate between a natural star collapse or ASP engine origin? From the above discussion, it should be clear that if someone created an ASP engine, it would be advantageous for them to initially create a small singularity, then grow it to its design size by adding mass at a faster rate than it evaporates, and then, once it reaches its design size, maintain it by continuing to add mass at a constant rate equal to the evaporation rate. In contrast, if it were formed via the natural collapse of a star it would start out with a given amount of mass that would remain fixed thereafter.

So let’s say our universe is, as Smolin says, a black hole. Available astronomical observations show that it is expanding, at a velocity that appears to be close to the speed of light. Certainly the observable universe is expanding at the speed of light.

Now a black hole has an escape velocity equal to the speed of light. So for such a universe

c²/2 = GM/R (5)

Where G is the universal gravitational constant, c is the speed of light in vacuum, M is the mass of the universe, and R is the radius of the universe.

If we assume that G and c are constant, R is expanding at the speed of light, and τ is the age of the universe, then:

R = cτ (6)

Combining (5) and (6), we have.

M/τ = (Rc²/2G)(c/R) = c³/2G (7)

This implies that the mass of such a universe would be growing at a constant rate. Contrary to the classic Hoyle continuous creation theory, however, which postulated that mass creation would lead to a steady state universe featuring constant density for all eternity, this universe would have a big bang event with density decreasing afterwards inversely with the square of time.

Now the Planck mass, m_p, is given by:

m_p = (hc/2πG)^½ (8)

And the Planck time, t_p, is given by:

t_p = (hG/2πc5)^½ (9)

If we divide equation (8) by equation (9) we find:

m_p/t_p = c³/G (10)

If we compare equation (10) to equation (7) we see that:

M/τ = ½(m_p/t_p) (11)

So the rate at which the mass of such a universe would increase equals exactly ½ Planck mass per Planck time.

Comparison with Observational Astronomy

In MKS units, G = 6.674e-11, c= 3e+8, so:

M/τ= c³/2G = 2.02277 e+35 kg/s. (12)

For comparison, the mass of the Sun is 1.989+30 kg. So this is saying that the mass of the universe would be increasing at a rate of about 100,000 Suns per second.

Our universe is believed to be about 13 billion years, or 4e+17 seconds old. The Milky Way galaxy has a mass of about 1 trillion Suns. So this is saying that the mass of the universe should be about 40 billion Milky Way galaxies. Astronomers estimate that there are 100 to 200 billion galaxies, but most are smaller than the Milky Way. So this number is in general agreement with what we see.

According to this estimate, the total mass of the universe M, is given by:

M = (2e+35)(4e+17) = 8e+52 kg. (13)

This number is well known. It is the critical mass required to make our universe “flat.” It should be clear, however, that when the universe was half as old, with half its current diameter, this number would have needed to be half as great. Therefore, if the criteria is that such a universe mass always be critical for flatness, and not just critical right now, then its mass must be increasing linearly with time.

These are very curious results. Black holes, the expanding universe, and the constancy of the speed of light are results of relativity theory. Planck masses and Planck times relate to quantum mechanics. Observational astronomy provides data from telescopes. It is striking that these three separate approaches to knowledge should provide convergent results.

This analysis does require that mass be continually added to the universe at a constant rate, exactly as would occur in the case of an ASP engine during steady-state operation. It differs however in that in an ASP engine, the total mass only increases during the singularity’s buildup period. During steady state operation mass addition would be balanced by mass evaporation. How these processes would appear to the inhabitants of an ASP universe is unclear. Also unclear is how the inhabitants of any Smolinian black hole universe could perceive it as rapidly expanding. Perhaps the distance, mass, time, and other metrics inside a black hole universe could be very different from those of its parent universe, allowing it to appear vast and expanding to its inhabitants while looking small and finite to outside observers. One possibility is that space inside a black hole is transformed, in a three dimensional manner analogous to a ω = 1/z transformation in the complex plane, so that the point at the center becomes a sphere at infinity. In this case mass coming into the singularity universe from its perimeter would appear to the singularity’s inhabitants as matter/energy radiating outward from its center.

Is there a model that can reconcile all the observations of modern astronomy with those that would be obtained by observers inside either a natural black hole or ASP universe? Speculation on this matter by scientists and science fiction writers with the required physics background would be welcome [13].

Conclusions

We find that ASP engines appear to be theoretically possible, and could offer great benefits to advanced spacefaring civilizations. Particularly interesting is their potential use as artificial suns to enable terraforming of unlimited numbers of cold worlds. ASP engines could also be used to enable interstellar colonization missions. However the number of ASP terraforming engines in operation in the universe at any one time most likely far exceeds those being used for starship propulsion. Such engines would have optical signatures similar to M-dwarfs, but would differ in that they would be much smaller in power than any natural M star, and hence have to be much closer to exhibit the same apparent luminosity. In addition they would move in orbit around a planetary body, thereby displaying a periodic Doppler shift, and could have an anomalous additional gamma ray component to their spectra. An ASP engine of the type discussed would be detectable by the Hubble Space Telescope at distances as much as 50 light years, within which there are approximately 1,500 stellar systems. Their images may therefore already be present in libraries of telescopic images as unremarkable dim objects, whose artificial nature would be indicated if they were found to display parallax. It is therefore recommended that such a study be implemented.

As for cosmological implications, the combination of the attractiveness of ASP engines with Smolinian natural selection theory does provide a potential causal mechanism that could explain the fine tuning of the universe for life. Whether our own universe could have been created in such a manner remains a subject for further investigation.

References

1. Hawking, S. W. (1974). “Black hole explosions?” Nature 248(5443): 30–31. https://ui.adsabs.harvard.edu/abs/1974Natur.248…30H/abstract

2. Hawking Radiation, Wikipedia https://en.wikipedia.org/wiki/Hawking_radiation accessed September 22, 2019.

3. Arthur C. Clarke, Imperial Earth, Harcourt Brace and Jovanovich, New York, 1976.

4. Charles Sheffield, “Killing Vector,” in Galaxy, March 1978.

5. Louis Crane and Shawn Westmoreland, “Are Black Hole Starships Possible?” 2009, 2019. https://arxiv.org/pdf/0908.1803.pdf accessed September 24.

6. Freeman Dyson, “The Search for Extraterrestrial Technology,” in Selected Papers of Freeman Dyson with Commentary, Providence, American Mathematical Society. Pp. 557-571, 1996.

7. Robert Zubrin, “Detection of Extraterrestrial Civilizations via the Spectral Signature of Advanced Interstellar Spacecraft,” in Progress in the Search for Extraterrestrial Life: Proceedings of the 1993 Bioastronomy Symposium, Santa Cruz, CA, August 16-20 1993.

8. Crane, “Searching for Extraterrestrial Civilizations Using Gamma Ray Telescopes,” available at https://arxiv.org/abs/1902.09985.

9. Robert Zubrin, The Case for Space: How the Revolution in Spaceflight Opens Up a Future of Limitless Possibility, Prometheus Books, Amherst, NY, 2019.

10. Paul Davies, The Accidental Universe, Cambridge University Press, Cambridge, 1982

11. Lee Smolin, The Life of the Cosmos, Oxford University Press, NY, 1997.

12. Louis Crane, “Possible Implications of the Quantum Theory of Gravity: An Introduction to the Meduso-Anthropic principle,” 1994. https://arxiv.org/PS_cache/hep-th/pdf/9402/9402104v1.pdf

13. I provided a light hearted explanation in my science fiction satire The Holy Land (Polaris Books, 2003) where the advanced extraterrestrial priestess (3rd Class) Aurora mocks the theory of the expanding universe held by the Earthling Hamilton. “Don’t be ridiculous. The universe isn’t expanding. That’s obviously physically impossible. It only appears to be expanding because everything in it is shrinking. What silly ideas you Earthlings have.” In a more serious vein, the late physicist Robert Forward worked out what life might be like on a neutron star in his extraordinary novel Dragon’s Egg (Ballantine Books, 1980.) A similar effort to describe life on the inside of a black hole universe could be well worthwhile. Any takers?

"Now that we are dependent on heavy metals rather than fossil organics and sunlight, economics have simply gone away. You want a lesson in economics from a biophysicist's point of view? It works like ecology—it breeds and selects. Not that we actually carry them in our pockets, but the gram of uranium has become our most basic unit of currency. Thanks to chronic short-staffing, we consider it equivalent to half an hour of human labor, though its energy potential is some twenty-six million times greater. Aside from ourselves, it is the first driver of our economy, the reasons for which are not at all arbitrary."

"For energy reasons," I said.

He winced slightly, shifted position in his chair. "Energy? Well, yes and no. Energy is less important than transmutation potential. In rough terms, a fusion reactor cascading a gram of deuterium/tritium up into a gram of iron—the basin of the binding energy curve—will liberate enough energy to boil about twenty thousand tons of water. A gram of uranium in a ladderdown reactor produces approximately the same. And yet, the uranium is worth ten thousand times more, because in laddering it down, we don't have to sink all the way to iron. We can stop anywhere along the way, and our waste products are isotopes of hydrogen which we can cascade back up, again stopping wherever we like below that magic number, iron fifty-six. A ladderdown economy sees value not only in what a substance is, but also in what it can become, and uranium, alone among the stable elements, can become anything." (all the elements with an atomic number over 82 {uranium} only have isotopes that are known to decompose through radioactive decay.)

---

Many people are surprised to learn that lead's energy potential is only twenty-five percent less than uranium's, but the thing to remember is that lead has ten fewer transmutation targets—eighty-one versus ninety-one—which translates into a factor of a thousand reduction in its value (Lead has 82 protons and uranium has 92 protons, so lead has 10 fewer transmutation targets). Gold, three rungs lower still, is worth about a five-thousandth as much as uranium (Gold has 79 proton, 13 fewer transmutation targets than uranium, 3 fewer than lead). It has beautiful mechanical and electrical properties, but really, the major cost of paving the streets with it is the labor.

---

The energy density of antihydrogen is about 250 times what we can achieve with ladderdown, and the production and storage are difficult. Wonderful fuel, the best, but the last time I checked, a gram of it cost over eighty thousand g.u.

---

Turns out we'll be paying for our food and clothing purchases after all, using, of all things, our shoes. No kidding! Our guide pointed out some bracelets, and though they were fashioned of plain gold he assured us they were very expensive. From the labor that went into them, I assumed, for they were handmade, but no, it turns out the fingernail-sized "dollars" that have been spent on our behalf are also made of gold, and derive their value from their own intrinsic worth as metal. As if we Munies walked around trading actual grams of uranium back and forth. This is what comes of not using ladderdown!

The Gladholders think our "duck shoes" are frightfully amusing anyway, and when they found out what the sole weights were made of, I thought they'd never stop laughing. and when they offered to replace those same blocks with equivalent masses of lead, which of course is five times more valuable back home, I thought we'd never stop laughing.

---

The biophysicist's voice came back careful, almost embarrassed. "It's never been a secret that nuclear energy presents … certain dangers. We think of ladderdown as a 'clean' technology, which in a radiation sense it certainly is."

"But?"

"But. The quantum spatial distortion is normally induced and focused within a shielded reactor, where its effects can be controlled to within a few Planck radii. How else to tunnel out only the desired nucleons, yes? But if we invert the distortion function along the B-axis, essentially turning it inside out in three-dimensional space, the same ladderdown tunneling can be induced stochastically in a much larger spherical shell, centered about the inductor. Shielding irrelevant, because it's inside the affected region, you see? Considered too hazardous for use in bloom cauterization, the phenomenon has no industrial applications. Look it up under Things Not to Try."

Most of that went right over my head, but the gist seemed clear enough: he was talking about releasing energy, lots of it, in an uncontrolled manner. He was talking about a bomb.

The generating capacity is usually there, but the problem is infrastructure and interconnectors.

Essentially the customer (harbour) is now acting as a supplier.

The problem is that most of a (typical) nuclear sub's reactor steam goes into direct drive turbines to run the shaft. The turbogenerators to produce electrical power are much smaller; far below the capacity of the reactor.

Turboelectric designs have existed.

This paper was originally intended to be a follow on my experiences as an engineer aboard commercial tankers. The original intent was to provide a description of World War II-built turboelectric Destroyer Escorts and to illustrate the commonality they shared with commercial T-2 Tanker power plants. In the process of preparing this post, it became apparent that it would be desirable to expand it’s scope to include a discussion of the experiences that the U.S. Navy had in the delivery of ship to shore electrical power for humanitarian assistance.

In general, the amount of ship to shore power that can be delivered by US naval vessels is limited by a number of factors, including installed generating plant capacity and the availability of topside shore power connections. By far, the majority of current naval vessel electrical distribution systems are three phase, 450 VAC, 60 Hz. Exceptions are nuclear carriers, the newest LHA and LHD types, and the DDG 1000 Class ships which have (or will have) 4160 VAC distribution systems. The new T-AKE 1 Class ships operated by MSC have 6600 VAC integrated diesel-electric power plants. As a general rule of thumb, it becomes necessary to go to higher voltages aboard ships with generating plants with a capacity of 10,000 kW or greater because of circuit breaker interrupting capacity and cable limitations.

The DDG 51 Flight IIA Class will be used as an example to illustrate existing limitations in generating plant capacity. Each of these ships is fitted with three gas turbine driven ship service generators (SSGTG), rated at 2500 kW 450 VAC, 60 Hz (3000 kW on DDG 91 and follow). Using these ships as an example, this would appear to provide a total generating plant capacity of at least 7500 kW. However, there are several additional limitations that must be taken into account.

1. Generators must never be intentionally loaded to more than 90% capacity.
2. Due to circuit breaker limitations, only two sets may be operated continuously in parallel. The third set serves as a standby unit.

Given these limitations, the usable generating plant capacity aboard these ships is approximately 4500 kW (5400 kW on the later ships). In addition, ships must supply their own in-port services that may be as much as 2500 kW or more. This only leaves a margin of about 2000 to 3000 kW of available excess energy. This is a bit misleading because the ships only had two topside shore power connections, each consisting of four cables; each rated at 400 amperes giving a total of 3200 amperes through eight cables. Assuming a power factor of .8 and no more than 90% loading, this results in a total delivery capability of about 1800 kW. Coupled with the fact that many of the countries that could require humanitarian relief have 50 Hz distribution systems, these factors impose severe limitations on the ability of modern surface combatant ships to deliver shore power. Destroyer tenders (AD) and submarine tenders (AS) could deliver as much as 7000 kW at 450 VAC to ships alongside them. Only two submarine tenders remain in service as of 2014, USS Emory S. Land (AS 39), based in Diego Garcia, and USS Frank Cable (AS 40), based in Guam. Modern ships with integrated electric drive plants have high generating plant capacities. However, significant alterations would be required to make them capable of delivering large amounts of shore power.

The above limitations did not exist aboard older ships with turboelectric and diesel-electric plants because these ships had separate propulsion and ship service generating plants. It was possible to divert the bulk of the power from the main propulsion generators to shore at either 50 or 60 Hz provided that adequate cable reels were available. Some examples are discussed in the following paragraphs.

Approximately 440 Destroyer Escorts (DE) was built between 1943 and 1944. Ninety-five of them were converted to high-speed transports, and another seventy-eight was delivered to the United Kingdom under the Lend Lease agreement where they served as Captain Class frigates. The ships were divided into six classes and had four different propulsion plants including geared steam turbine, turboelectric, geared diesel, and diesel-electric systems.

One hundred and two ships of the Buckley (DE 51) and an additional twenty-two ships of the Rudderow (DE 224) had twin-screw turboelectric (TE) propulsion plants rated at 12,000 SHP. Maximum sustained speed was approximately twenty-four knots. A major reason for the use of turboelectric propulsion systems was limitations in reduction gear manufacturing capabilities during the war. Priority had to be given to manufacturing the double reduction gears required on destroyers, which had propulsion plants rated at 60,000 SHP. General Electric and Westinghouse manufactured the systems. They had many commonalities with the propulsion plants aboard the T-2 tankers described in a previous post. The machinery arrangement was similar to that aboard navy destroyers with alternating fire rooms and engine rooms. Each fire room contained a single D type boiler which produced superheated steam at a pressure of 450 PSI and a temperature of 750° F. Each engine room contained one main propulsion generator rated at 4600 kW, 2700 VAC, 93.3 Hz, 5400 RPM, one ship service turbo generator rated at 300 kW at 450 VAC/40 kW DC, and a 6000 SHP, 400 RPM main propulsion motor. The main propulsion control consoles were very similar in appearance to those on T-2 tankers. The ships had the capability of operating both main motors on a single main generator.

During World War II, a total of five ships of the Buckley Class and two British Captain Class frigates were converted into floating power stations for the purpose of supplying electrical power to shore in the event of a power outage. It is understood that a number of other ships of the class were recycled as floating power stations for coastal cities in Latin America under a program sponsored by the World Bank. However, no additional information is readily available concerning this program. A discussion of the services provided by the five Buckley Class ships is contained in the following paragraphs.

A major part of the conversion process consisted of the removal of torpedo tubes and installation of large cable reels located on the O1 Deck, as shown in the following illustrations:

• 

The floating power plants had a total generating plant capacity of approximately 8000 kW (estimated), 2300 VAC, 60 Hz, .8 Power Factor. This equates to a usable generating plant capacity of approximately 7200 kW taking into account the 90% load factor. 50 Hz power could be easily provided to locations where necessary. The only action required was to slow the main generators down from 3600 to 3000 RPM by the use of the governor control levers. This capability does not exist in any vessels currently in service.

USS Donnell (DE 56) was converted into a power barge in England in 1944 after a torpedo struck it during convoy duty. Damage was fairly extensive and propulsion power could not be readily restored. The ship was then towed to Cherbourg, France, where it supplied power for a period of time. This experiment was considered to be very successful. It resulted in the decision to convert the other vessels on this list into floating power plants.

USS Foss (DE 59) provided power to the city of Portland, Maine, in 1947-1948 during a severe drought and a number of forest fires. At the time, it was assigned to operational development duties along with its sister ship, the USS Maloy (DE 791). There is no record of Maloy ever being converted into a floating power plant. Foss later supplied shore power to various ports in Korea in 1950-1951.

• 

USS Whitehurst (DE 634) and USS Wiseman (DE 667) supplied power to the city of Manila for several months in 1945. During that period, Wiseman also provided drinking water to Army facilities in the harbor area. Wiseman later supplied power to the city of Masan, South Korea in 1950. USS Marsh (DE 699) supplied power to the island of Kwajelin from May until September in 1946. It later supplied power to the cities of Masan and Pusan in 1950 during the Korean War.

USS Lexington (CV-2) and USS Saratoga (CV-3) entered service in 1928. Both ships were ahead of their time. They were fitted with turbo-electric propulsion systems rated at 180,000 SHP. The ships had four steam turbine driven main propulsion generators each rated at 35,200 kW, 5000 VAC. Unlike more modern installations, the plants were not integrated and ship service power was DC supplied by 6 separate generators, each rated at 750 kW, 240 Volts DC. Up until the early 1930s, the only use the U.S. Navy had made of AC was in the propulsion systems aboard the USS Langley (CV-1) and six battleships that entered service in the 1920s.

In 1929, Washington State suffered a drought that resulted in a loss of hydroelectric power to the city of Tacoma. The U.S. Navy sent Lexington, which had been in the shipyard at Bremerton to Tacoma to provide power to the city. A considerable amount of coordination was required between the city and the ship in order to allow Lexington to provide power. The hookup consisted of twelve cables connected to circuit breakers and a bank of transformers located on the dock with a total rating of 20,000 kVA. The ship then provided a total of 4,520,960 kilowatt hours from one main propulsion generator between 17 December, 1929 until 16 January, 1930, at an average rating of 13,000 kW until melting snow and rain brought the local reservoirs up to a level where normal power could be restored.

• 

• 

The US Army also had a Nuclear Power Program in the 1960s. As part of this program they converted an existing Liberty ship into the Sturgis (MH-1A), a floating nuclear power station. This involved the removal of the existing propulsion plant and installation of a pressurized water reactor in a 350-ton containment vessel. After several months of testing Sturgis was towed to the Panama Canal Zone where it supplied 10,000 kW of power to operate the locks from 1968 through 1976 because of a water shortage which had an impact due to the loss of hydroelectric power. Unfortunately, the cost of operation proved to be very high and Sturgis was retired in 1976 after the Army Reactor Program was discontinued. Sturgis was then defueled and placed into the James River Reserve Fleet.

References:

1. NAVPERS 10864-C – Shipboard Electrical Systems, 1969
2. Paper – Ship to Shore Power, US Navy Humanitarian Relief, Scott, 2006
3. Transactions, SNAME, 1929
4. NAVSEA Ship Information Book, AS39/40
5. DDG 51 Flight IIA Electrical Plant Load Analysis
6. NAVSOURCE
7. USS Lexington (CV-2) report following supplying power to the City of Tacoma for a month, 1930.

Background

While the author was training to become a US Navy Enlisted Reactor Operator, qualified operators repeatedly stated, “This sub could power a small city.” In a similar vein, it was proposed that US Navy ships should provide electrical power during the response to Hurricane Katrina in New Orleans. These off the cuff assessments prompted a more realistic assessment: is it feasible to power facilities ashore from a ship?

History

During World War II, there were seven destroyer escorts converted into Turbo-Electric Generators (TEG) specifically for the purpose of providing electrical power to shore facilities. They were the Donnell (DE-56), Foss (DE-59), Whitehurst (DE-634), Wiseman (DE-667), Marsh (DE-699), and two British lend-lease ships; Spragge (K-572, ex-DE-563) and Hotham (K-583 ex-DE-574). Data for these ships are sparse in general.

Consider the Wiseman, for which more data is available. This ship had oil fired boilers producing steam to turn turbine generators which in turn powered electric propulsion motors. This electric ship configuration is optimal for providing electric power ashore since all the power in the ship is already being converted to electric. The Wiseman had transformers and cable reels topside to deliver power at high voltages over relatively long distances. Wiseman powered the city of Manila during WWII and the port of Mason during the Korean War. Wiseman delivered 5,806,000 kWh to Manila over five and a half months, giving an average generation capability greater than 1.4 MW.

The US Army also used ship to shore power to power remote stations. One notable case is that of the Sturgis/MH-1A, A WWII era Liberty ship equipped with a nuclear power plant used to provide power to the Panama Canal Zone from 1968 to 19753. The MH-1A power plant on the Sturgis generated 10MW electrical power which allowed the canal locks to be operated more frequently.

Thus history shows that ships can provide power to the shore, if only in limited amounts, and using specialized ships.

Present

There are currently no US Navy ships designed specifically to provide power to the shore. They are however designed to be powered from the shore and this capability could be used to act as a power source. For example, the author’s ship, USS Key West (SSN-722), a Los Angeles class nuclear powered fast attack submarine, once received ‘shore power’ from a destroyer while moored alongside the destroyer anchored off Monaco. This allowed the labor intensive nuclear reactor plant on the submarine to be shutdown. The gas turbine generators on the destroyer require fewer watchstanders and had to run to power the destroyer’s own loads. This anecdotal evidence shows that power can be made to flow from at least one US Navy ship and conceivably could flow from most.

The capability to provide power can be evaluated by considering the ship as a load and assuming that whatever power it can draw, it can deliver. For USN ships smaller than carriers and amphibious ships, the unit of measure is the single shore power cable. These cables are rated to 400A at 450V 3 phase or 0.312MW assuming a unity power factor4. Submarines and surface combatant ships typically can connect up to eight cables, yielding a total of 2.5MW. For a carrier, the shore power supply must deliver 21MVA at 4160V5. Amphibious ships are presumably between these values. Without significant changes, current Navy ships could theoretically supply 2.5 to 21MW of electrical power to the shore. This again assumes generation capacity to match the ship as a load and also assumes this capacity is above that required to power the ship and its power plant.

What if more power is needed? More ships could be used, but there is also more power onboard each ship. This other power is the power for propulsion. Remembering the Wiseman, it was an ideal ship for supplying power because all the power of the boilerswas first converted to electricity by turbine generators. Today’s Navy ships are not ‘all electric’ and so a significant portion of the power onboard is dedicated to propulsion and is often coupled directly to the propeller shafts. Steam plants fired by oil or nuclear reactors offer a sort of middle ground. While the propulsion turbines are coupled to the shafts, the steam can be diverted upstream. In this scheme, high pressure steam would be piped out of the ship and used to drive a larger turbine generator. The spent low energy steam and condensate would then be piped back into the ship and into the condensate system, closing the loop. Piping is not as forgiving or flexible as cabling, this would not be a trivial set up and is probably impossible for a submarine.

Considering the publicly available shaft horsepower ratings for the ship as the electrical power available, it is clear that much more power is in the hulls than is available through the shore power connections.

Table 1 Power Available From Steam Plant Ships
Ship type	Total Shaft Power (HP)	Electrical Power (MW)
Fast Attack Submarine	35,000	26
Large Deck Amphib	70,000	52
Carrier	260,000	194

Note that most surface combatants are driven by gas turbine or diesel engines and their propulsion power cannot feasibly be extracted from the ship.

Future

The Navy is driving toward all electric ships in a case of history repeating. This is driven by the desire to access propulsion power to supply combat systems. As stated previously, all electric ships are ideal for providing power to shore since all their power is first converted to electricity. The future destroyer DD(X) is being designed as an all electric ship with two Rolls-Royce MT-30 gas turbine generators producing a total of 78MW of electrical power.

The future carrier CVN(X) will be nuclear powered and have a steam plant but will also have increased electrical generation (104MVA) to support launching planes using electrical power.

Neither DD(X) nor CVN(X) is designed to deliver power outside the hull, but it would be easier to export it as electrical current than as steam. Loads

To investigate the claim of powering a small city, a ‘rough order of magnitude’ (ROM) calculation was performed. The author’s most recent electrical utility bill was used to determine the average power of a house, and then this number was used to determine how many houses could be powered. The bill was for 1203kWh over a 29 day period giving an average load of 1.7kW. Again, this is a ROM calculation and does not incorporate seasonal variations in power use nor the likelihood of reduced use in an emergency situation.

Using the existing shore to ship power capability, the submarine can power 1,500 nominal homes: more of a town than a small city. The carrier can power 12,000 houses and that is a small city.

Table 2 Powering Houses with Existing Ships Equipment
Ship type	Shore Power (MW)	Houses
Submarine	2.5	1,500
Carrier	21	12,000

If the steam plant of an amphib or a carrier were modified to increase electrical generation to match propulsion power, many more houses could be powered, equivalent to a medium city based on population only.

Table 3 Powering Houses with Steam Plants
Ship type	Steam Power (MW)	Houses
Amphib	52	31,000
Carrier	190	110,000

Lastly, if all the generation capability of future ship classes could be made available external to the hull, a large population could be supplied.

Table 4 Powering Houses with Future Ships
Ship type	Generation Power (MW)	Houses
DD(X)	78	46,000
CVN(X)	104	61,000

The US Navy is not chartered to act as a power utility, they are not likely to power the shore except at forward military or disaster locations. In these cases, residential housing is not likely to be the first load supplied. Instead, hospitals and other vital infrastructure are likely to receive priority. This prioritization is important since a single hospital can be a significant load. Based on one report discussing emergency generation installation, a value of 2MW per hospital was determined.

Using shore power, a submarine or surface combatant can power one hospital with a small surplus. This undermines the claim for a small city since few loads will be powered after the hospital. A carrier can power ten and a half hospitals, likely allowing some residential power after the vital infrastructure is supplied.

• 

• 

MH-1A was the first floating nuclear power station. Named Sturgis after General Samuel D. Sturgis, Jr., this pressurized water reactor built in a converted Liberty ship was part of a series of reactors in the US Army Nuclear Power Program, which aimed to develop small nuclear reactors to generate electrical and space-heating energy primarily at remote, relatively inaccessible sites. Its designation stood for mobile, high power. After its first criticality in 1967, MH-1A was towed to the Panama Canal Zone that it supplied with 10 MW of electricity from October 1968 to 1975. Its dismantling began in 2014 and was completed in March 2019.

Design

The MH-1A was designed as a towed craft because it was expected to stay anchored for most of its life, making it uneconomical to keep the ship's own propulsion system.

It contained a single-loop pressurized water reactor, in a 350-ton containment vessel, using low enriched uranium (4% to 7% ²³⁵U) as fuel.

The MH-1A had an elaborate analog-computer-powered simulator installed at Fort Belvoir. The MH-1A simulator was obtained by Memphis State University Center for Nuclear Studies in the early 1980s, but was never restored or returned to operational service. Its fate is unknown after the Center for Nuclear Studies closed.

Panama Canal Zone, 1968–1976

After testing at Fort Belvoir for five months starting in January 1967, Sturgis was towed to the Panama Canal Zone. The reactor supplied 10 MW (13,000 hp) electricity to the Panama Canal Zone from October 1968 to 1975.

A water shortage in early 1968 jeopardized both the efficient operation of the Panama Canal locks and the production of hydroelectric power for the Canal Zone. Vast amounts of water were required to operate the locks and the water level on Gatun Lake fell drastically during the December-to-May dry season, which necessitated curtailment of operations at Gatun Hydroelectric Station

The ship was moored in Gatun Lake, between the Gatun Locks and the Chagres dam spillway. Beginning in October 1968 the 10 MW electrical power produced by the MH-1A plant aboard the Sturgis allowed it to replace the power from the Gatun Hydroelectric Station, which freed the lake water for navigation use. To help out further, the Andrew J. Weber, a diesel-fueled power barge of 20 MW capacity, was deployed to the Canal Zone in November 1968. These two barges not only contributed to meeting the Canal Zone’s power requirements, but also made possible the saving of vast quantities of water that otherwise would have been needed to operate the hydroelectric power station. The Corps of Engineers estimates that over one trillion gallons were saved (or, rather, freed up) between October 1968 and October 1972 – enough to permit fifteen additional ships to pass through the locks of the canal each day.

After one year of operations in the Canal Zone, the MH-1A reactor had to be refueled, a process which took one week (17–25 October 1969), according to a 1969 Corps of Engineers report. According to a 2001 report by the Federation of American Scientists, the MH-1A reactor had a total of five cores during its operational life. It used low-enriched uranium (LEU) in the range of 4 to 7 %, with a total amount of uranium-235 supplied being 541.4 kilograms (for the five cores).

The Sturgis was eventually replaced by two 21 MW Hitachi turbines, one on the Pacific side of the isthmus and one on the Atlantic side.