A new type of nuclear reactor designed to power manned outposts on the Moon and Mars could, in a few years’ time, be ready for the first space trial, according to project team members. A flight test is the next big step for the experimental Kilopower fission reactor, which has undergone a series of critical soil tests from November 2017 to March 2018. No off-earth demonstration is planned yet, but Kilopower should be operational by 2022, if necessary, said Patrick McClure, Kilopower project manager at the Los Alamos National Laboratory of the Department of Energy (DOE) in New Mexico. I think we could do it in three years and be ready for the flight, “McClure said late last month during a presentation with the NASA Working Group on Future In-Space Operations. I think three years is a very feasible timeframe, “he added, stressing that this is not necessarily what he thinks, but NASA’s, which is developing the Kilopower project with the DOE.

Another kind of nuclear power in space Nuclear power has been driving spacecraft for decades. The NASA Voyager 1 and Voyager 2, New Horizons and Curiosity Mars Rover probes and many other robot researchers are using thermoelectric radioisotope generators (RTGs) to convert the heat released by the radioactive decay of plutonium-238 into electricity. The performance of RTGs is relatively low. For example, the power used by Curiosity and NASA’s upcoming Mars 2020 rover will produce about 110 watts at the start of a mission. (This output will decrease slowly over time.) A manned Mars outpost will have a significantly higher energy requirement: about 40 kilowatts of continuous, 40 kWe electrical power, even for the small research station that NASA plans to build by the end of the 2030s, McClure said. After all, the pioneers need electricity to purify their water, extract oxygen from the carbon dioxide-dominated Martian atmosphere, recharge their rovers, heat their homes, and so forth. Human exploration of Mars will therefore require a different strategy for energy production. And here Kilopower comes into play. Like nuclear power plants designed to remain on Earth, Kilopower is a fission reactor. It converts the heat created by the splitting of atoms into electricity via so-called Stirling engines (in contrast, nuclear power plants generally use this heat to produce turbine-rotating steam.) In the soil test series, completed in March 2018 and known as KRUSTY (Kilopower Reactor Using Stirling Technology), the reactor converted 30% of the gap heat into electricity, according to McClure. This efficiency dwarfs that of RTGs, which convert about 7% of the available heat. This has been a very successful test, “said McClure. The Kilopower project officially started in 2015, but its architects have already demonstrated the basic concept in 2012 through an experiment called Flattop Fissions (DUFF) demonstration. And yes, “Simpsons” lovers, the Kilopower people are your people: DUFF and KRUSTY refer to the legendary animated TV show. Dave Poston, a member of the project team, is a big fan, McClure said. (For the uninitiated, Duff is the beer favored by Homer Simpson, and the degenerate, tax evasive Krusty the Clown hosts a children’s television show in the Simpsons universe.) As the name implies, the Kilopower reactor should produce at least 1 kilowatt of electrical power (1 kWe). The power is scalable to about 10 kWe and can be operated for about 15 years, according to McClure. For example, four larger Kilopower reactors could meet the energy needs of NASA researchers, with a fifth reactor likely to have landed as a replacement. These devices are smaller than you might think. The entire 10 kWe engine would only be 3.4 meters high and the reactor component would be the size of an old metal garbage can. The shieldless core alone would be about the size of a roll of paper towels, McClure said. Nevertheless, these pieces are heavy. With a shield, the entire 10 kWe reactor would probably weigh about 4,400 pounds (2,000 kg). Part of this mass could be reduced if the reactor is buried and therefore does not require as much protection from astronauts, McClure said (without shielding, the 10 kWe reactor would weigh about 1,500 kg.) The Kilopower reactors are pretty safe, he said. The devices are only turned on when they enter space.Therefore, there is no danger of dangerous exposure to radiation, even if the rockets of the reactors strike back at the Earth (the switch does not always have to be on the surface of the Moon or Mars.) The Kilopower reactor is flexible enough to be installed in a space probe without major modifications, which greatly enhances electric propulsion, McClure said.

Plus, the kilo power will self-regulate, McClure said. If the reactor gets too hot, its Stirling engines drain more heat from the uranium core. If the temperature drops too high, the nucleus naturally contracts, capturing more neutrons and causing more atomic splitting collisions. Incidentally, a quartet of reactors in operation could give a true outlook on a Mars outpost. These devices have to emit a lot of “extra” heat into the air of the Red Planet. At 30% efficiency, 70% of the gap heat remains. So they will come equipped with heaters. A striking design features wide, circular heaters on the reactor heads that give them a parasol look. The Kilopower team began investigating possible demonstration missions shortly after KRUSTY’s graduation, McClure said. The first thing thrown at us was a potential Lunar Lander, so we looked at what a potential lunar system might be, “he said. This concept mission is unlikely to fly, McClure added. It aimed at the Moon North Pole, while NASA turned its attention to the Moon’s South Pole for reconnaissance with crew. (The agency intends to send astronauts under the Artemis program until 2024However, the team would welcome a space mission if NASA would actually launch one, McClure said. We are excited, “he said.We look forward to maybe doing something new.

Kilopower is the first truly novel fission reactor concept developed in the US over the last 40 years. It would certainly be a milestone to make it into space, but the project would not break new ground. After all, fission reactors have left the earth. In April 1965, the US put a reactor into orbit of the experimental satellite SNAP-10A.(Failure of an electrical component shut down this reactor after only 43 days.) And the Soviet Union launched more than 30 fission reactors on board satellites from 1967 until the late 1980s.