New Space and Tech

Solar Panel Robots and Mini Nuclear Reactors Could Power NASA’s Future Moon Base

By Jon Kelvey
June 22, 2023
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Solar Panel Robots and Mini Nuclear Reactors Could Power NASA’s Future Moon Base
The eVinci microreactor.
Image credit: Westinghouse.

Space robotics company Astrobotic Technology and electric power behemoth Westinghouse are joining forces to develop nuclear power for NASA and the Department of Defense to use in outer space, with the two companies announcing the collaboration in a memorandum of understanding on June 1. The result of the two Pennsylvania companies’ collaboration may help NASA return to the Moon — this time to stay — as well as power future missions to Mars.

NASA — as well as other space agencies — has its eyes set on the lunar South Pole. Setting this as the destination for its Artemis Moon program makes a lot of sense from a scientific point of view. The mountainous and cratered terrain shelters the region from a low Sun angle, meaning there exist areas in permanent deep shadow, where frozen water ice has lurked silently for millions of years, offering scientists a window into the early days of the Moon, the Earth, and the solar system. The presence of water ice also provides raw material NASA astronauts can use to practice creating potable water, rocket fuel, and other essentials — what NASA calls “in situ resource utilization” — that can not only enable long-term habitation of a planned lunar base camp, but may be essential for later missions to Mars.

But the same terrain features that make the lunar South Pole interesting also make it difficult to manage. A bright Sun that’s low on the horizon will cast long, deep shadows that can render solar power systems inconsistent. That’s where nuclear power comes in. Westinghouse was already developing a new type of nuclear fission reactor for terrestrial use it calls the eVinci microreactor: a prefabricated, modular approach to nuclear fission power that generates modest amounts of usable energy with minimal external infrastructure. And now, the company will work with Astrobotics to find ways to develop an energy infrastructure for the lunar surface. While neither company has elaborated on what the specifics of the partnership will look like, there are hints that they’ll explore pairing the eVinci microreactor with the LunaGrid power grid being developed by Astrobotics.

The two companies are no strangers to developing energy systems for NASA. Westinghouse was one of three companies awarded $5 million contracts by NASA in June 2022 to develop nuclear power systems for NASA’s Fission Surface Power project, the other two being aerospace giant Lockheed Martin and the Houston Texas based-IX. Astrobotic, meanwhile, was one of three companies to win $6.2 to $7 million NASA contracts to further develop solar array systems for Moon missions in August of 2022. The other two winners were Honeybee Robotics of Brooklyn, New York, and, again, Lockheed Martin.

Designing a fission microreactor for space

One of the major pros to the eVinci microreactor is that it can basically operate autonomously,” without an on-site human operator, MIT nuclear scientist and engineer Jacopo Buongiorno told SpaceRef. Such autonomous operation is a valuable trait for a power source on the Moon or Mars, where no astronaut will be able to afford to dedicate all their time to managing a power plant, he says. Also beneficial is the eVinci’s compact size. “This thing fits within a standard shipping container,” Buongiorno says.

Buongiorno is not involved with the new collaboration between Westinghouse and Astrobotic, but has been familiar with the eVinci design since 2018, when he says Westinghouse was first developing the reactor for the US Department of Defense.

Instead of using pressurized liquid sodium to cool the reactor core, a common practice in nuclear reactors, Westinghouse envisions using heat pipes, which are long, steel alloy pipes with unpressurized sodium sealed inside to passively transfer heat from the reactor core to outside air or water. The sodium evaporates at one end of the heat pipe near the reactor core, Buongiorno explained, and condenses at the far end outside of the reactor, transferring the heat and eliminating the need for large, complex pumps and cooling towers.

“In the vast majority of the nuclear power plants that are currently in operation, you have water literally flowing through the core of the reactor,” picking up heat and taking it elsewhere,” Buongiorno said. Meanwhile, the eVinci reactor core has “essentially no moving parts,” reducing the mass of the system and the number of things that could fail.

“For space, reliability and weight are the name of the game,” Buongiorno added, “and so I think in both cases, eVinci is a potential winner.”

The eVinci design allows for small fission reactor units that can be combined to supply power for systems ranging from 200 kilowatts to 5 megawatts of electricity, according to Westinghouse documentation, all from a box that comes from the factory ready to go with eight years’ worth of fuel. That fuel, uranium, will also come in the form of Tri-structural isotropic (TRISO) particles or pebbles: uranium bits sealed within layers of ceramic so that the fuel can’t melt and release radioactive fission products.

Westinghouse declined to comment for this story, but the company has told the US Department of Energy that it plans to test the first operational eVinci reactor later in 2023. Despite all of Westinghouse’s innovations with the eVinci reactor, the reactor would need further adaptations to work in space, according to Buongiorno.

First, the design would need to be launch proofed, he says, ensuring that the forces of a rocket launch will not warp or break any essential components.

And then, although eVinci is tiny compared to most nuclear power plants, its current iteration still weighs about 100 tons — far too massive for a space mission.

“That’s bloody heavy for a rocket,” Buongiorno told SpaceRef, but “my understanding is for these [lunar] surface applications, 5 megawatts is actually more than they really need. So there is margin for actually making it even a bit smaller.”

A power grid for the Moon

Meanwhile, Astrobotic has been developing a system it calls LunaGrid as a solution to the spotty access to sunlight at the lunar South Pole. The system would use tethered robotic rovers carrying solar panels to catch sunlight where they can, supplying power to NASA or other clients via their tethers and wireless charging. The company plans to test the first elements of LunaGrid on the Moon by 2026.

Roving solar panels and modular nuclear fission reactors are, at least at the surface, orthogonal approaches to generating power on the Moon. But Astrobotic Vice President of Business Development Dan Hendrickson told SpaceRef that he sees them as complementary, with solar solutions providing power for smaller missions in the near future, and nuclear power taking a bigger role in later NASA missions.

”We believe nuclear power is a great fit for larger efforts like an Artemis base camp, and we’ve always intended LunaGrid to be a power agnostic grid long-term,” Hendrickson told SpaceRef. “Solar will help us meet near-term capability needs while other power sources like nuclear are matured and then integrated into LunaGrid over time.”

Exactly what that integration will look like, and indeed, what form the Astrobotic-Westinghouse collaboration on a space nuclear reactor will take in the near term, remain to be seen. But Buongiorno at least thinks some sort of mix of the two companies’ solar and nuclear approaches would be a good idea. Nuclear reactors can provide power even when there’s no sunlight on the Moon, while lighter, simpler solar power can help NASA to save money compared to relying entirely on nuclear power.

“It seems like a good marriage of two technologies,” he said. 

Jon Kelvey

Jon Kelvey is a science writer covering space, aerospace, and biosciences. His work has appeared in publications such as Air & Space Magazine, Earth and Space News, Slate, and Smithsonian in addition to SpaceRef.