To Nuke or Not to Nuke the Moon, That is the Multi-Billion Dollar Question
Energy is the lifeblood of civilization. This is true on Earth as well as for of our outward move into the solar system. Wherever we go, our actions and our level of success will be dictated by how much energy we have and are able to productively use. You cannot have an industrial civilization without plentiful energy. This is true whether this civilization is on the Earth, Moon, or beyond. With plentiful energy, the stars are at our doorstep.
In the past 20 years of my looking at, reviewing, and analyzing lunar and beyond exploration architectures, my own interests have shied away from nuclear power as part of any architecture as it immediately drives up the price to unaffordable levels and puts a major critical path milestone in the way of success. Solar power is great for low power outposts and can be implemented without a lot of development time and expense. However, as we have moved forward in time, there have been a lot of developments in small nuclear power systems that bear examination. The idea is to trade the value of a low power system powered by solar energy against a high power system powered by a nuclear reactor.
Low Power Industrial Outposts (Solar)
The question becomes, can a low power (solar) lunar infrastructure be built that enables industrialization. First we have to define what low power means. Practically, it means between 500 kilowatts to one megawatt of power. The reason is simple. We can get about 100 kilowatts per Delta IVH launch to the Moon using “traditional” methods. We can probably get about 300 kilowatts per launch to the Moon using a solar electric transportation stage and a Delta IVH launch plus the launch to put the SEP up in the first place. Doing a bit of arm waving the cost for either path will be about $2 billion for five hundred kilowatts and probably about $3 billion using a SEP for a megawatt and about $3.5 billion for a conventional approach.
The question becomes, is 500kw to a megawatt of electrical power sufficient to reach sustainability of a lunar (or anywhere else) industrial outpost. The answer depends on exactly where the facility is located and the richness of the resources (metals and volatiles) that are in the near vicinity of the location. Lets say for the sake of argument that you go to the ideal location, which to me is along the rim of Whipple crater, which itself is on the rim of Peary crater at the lunar north pole.
With a megawatt of power you get a lot for your money. You can do some serious ISRU of propellants, separating water from the regolith by heating it with solar thermal power (not in the megawatt power budget). You can then use electrolysis to separate the water into hydrogen and oxygen that can then be used to fuel single stage to orbit cargo and human carriers. Additionally, you can use the hydrogen and oxygen in closed loop fuel cell vehicles and heavy equipment to do your mining, road building, and other activities. However, even at the tip of the rim of Whipple crater, the sun does not shine all month, all year around. There would be periods when you have to power down to a caretaker level. This does not necessarily have to be bad as it could be the down time needed for maintenance, repair, and roll out of new capabilities.
Over several years some of the power could be used to manufacture solar panels. Indeed this would be one of the most profitable things to do as if a megawatt is the tipping point of sustainability, then more power, developed locally, creates a lot of leverage. There is nothing intrinsically impossible about doing this, you just have to send up the right equipment to do so, and then harvest purified silicon from the lunar regolith. Dr. Alex Ignatiev has a great paper on the subject and has done a lot of work in this area.
Silicon is plentiful on the Moon but it takes a lot of energy to extract it, meaning that as resources are dedicated to this task, fewer resources are available for other activities. ISRU of metal oxides would be the other major consumer of energy on the Moon and thus the productivity of the outpost is directly proportional to the amount of energy you have and how efficiently you use it. Adding solar thermal power is straightforward and can be done largely with local resources, providing a multiplier effect for manufacturing.
This path is entirely doable, but is it the best use of financial resources?
Nuclear Power on the Moon
In earlier iterations of lunar architecture studies, such as in the late 1980’s Space Exploration Initiative (SEI), nuclear power was one of the core systems for power at an outpost/base. This was principally because all of the base ideas that were part of the mainstream were not in the lunar polar regions. At the time we knew far less about the Moon and its resources than we do now, so this made sense. The guiding architecture came from a report, called the “Report of the 90 Day Study on Human Exploration of the Moon and Mars“. This was a very forward looking report at the time that basically had the kitchen sink of technologies, missions, and hardware for exploration built into it. As one example of how forward looking it was, look on page 3-32 (the link to the document is in the title above) and look at the “Long Range Mars Rover”. Here it is reproduced as figure 1:
Unless you have been living under a rock, you can see that the design of this 1989 Mars rover has a lot of similarity to the Curiosity lander that landed on Mars in August of 2012. Another advanced feature was a passive nuclear reactor. This reactor is shown in figure 2:
In looking at the SPT-100 reactor in the SEI 90 study I am struck by how underpowered the entire outpost would have been. They were very ambitious in what they wanted to do but 100 kilowatts of nuclear or solar power (there is a solar variant in the study as well), is simply not enough to do a lot of ISRU, exploration and science. In fairness the ISRU plant was of very modest capabilities and would have been used to make up gasses for the outpost and other non propellant uses.
In the 23 years since the SEI report nuclear technology has advanced fairly rapidly. Most of it is still in the demonstration or research stage but there are several small nuclear reactors that are on the way to operational status.
Here is the money question….
What could you do on the Moon if you had a 25 megawatt reactor (electrical) and 70 megawatts (thermal) energy. It changes everything….
Modern Small Nuclear Reactors
There is a pretty good body of information available on the web to inform people about small nuclear power systems. A very good round up of this information is provided at the World Nuclear Organization web site. There are some interesting common attributes of these small nuclear reactors that make them interesting for the Moon.
- Small Physical Size
- Modular Construction
- Unattended or Reduced Manpower Operation.
- Self Contained
- Low Proliferation Potential
- Ease of Disposal
- Lots of Power
Rather than go through all of them I selected the one that I thought was a very good representative of the group. It is by far the smallest in power with only 25 megawatts of electrical output and 70 kilowatts of thermal output but in comparison with what we have been talking about for the Moon up until now it is an amazing advance!
GEN4 Energy Molton Salt Fast Reactor
The GEN4 reactor is an amazing advance over earlier generation small reactors. Figure 3 shows a conceptual drawing of the reactor system:
Here are the key features of this reactor:
- Advanced reactor design – Use of advanced reactor concepts provides for a safer and simpler reactor, elimination of many potential accident scenarios that affect LWRs, and elimination of complex reactor systems.
- Small reactor – A smaller reactor is more appropriately sized for smaller generation requirements, can directly replace existing diesel fueled generators, and requires no upgrade to existing small electricity distribution systems.
- 10-year power module replacement – The Gen4 Module provides 25 MWe continuously for 10 years on its initial fuel load (compared to an 18 to 24 month cycle for current light water reactors). No on-site refueling is required. After 10 years the entire reactor module is replaced.
- Underground containment vault – The reactor is sited in an underground containment vault to provide isolation from the environment, prevent intrusion or tampering, and avoid harm from natural disasters.
- Factory-assembled transportable power modules – Factory assembly allows for standard designs, superior quality control, and faster construction and on-site deployment.
All of these features make this reactor amenable for lofting to the Moon for installation. How much would it cost? Even if it took ten launches of a Delta IVH or 6 launches of a Falcon 9 heavy, it would be well worth it. The provision of 25 megawatts of electrical energy and 70 megawatts of thermal energy would transform the proposition of lunar industrialization.
Applications for Massive Power
Gone would be the requirement to engineer every last part of a low power system for optimum efficiency. This would save quite a bit of money. The ability to use high power ISRU systems such as vacuum induction melting of metal becomes a no brainer. With high power ISRU and plentiful metal, structures with large interior volumes becomes very feasible. Large interior volumes would allow for plentiful living space for humans and operational space for ground systems. There would be plentiful electrical power and space for growing food, including meat animals.
The thermal energy could be used for the steam reformation of water into hydrogen and oxygen, and do it at an industrial scale, providing fuel for ground based fuel cell vehicles as well as fuel for lunar Single Stage to Orbit (SSTO) cargo transports. The thermal energy could also be used to drive of the volatiles in the mining of water from the permanently dark areas. Hot phase change material could also be easily used to keep equipment warm during their sojourns in the dark areas, removing the need for mobile nuclear power systems.
In short, as here on the Earth, power is everything to a civilization and we should very much consider and study, and develop the means whereby to loft these high power systems to the Moon. It would not be immediately, and for the very near term solar power systems would be used to bootstrap any ground operations on the Moon. However, the leverage and advantage of these high power, modular, and safe nuclear systems must become central to the industrialization of the Moon. It would transform the development of Mars as well and would enable the almost immediate colonization of the red planet.
We now have the technology and the tools that we need to open the solar system to development. We stand at the door. It would be a hell of a lot better use of money than refilling the corrupt coffers of Wall Street or Brussels. Indeed it would moot that as the wealth that would come from such development would of itself refill those coffers, and in a far more productive manner….