One of the most important enablers of a sustained presence in space is reliable power, and a new partnership between NASA and the U.S. Department of Energy is intended to provide just that. The agencies have established a new partnership to work on a fission surface power system, which will be capable of lasting for years on the surface of the Moon without refueling, with potential application to Mars missions in the future.
This agreement has been developed on top of many years of collaboration in space nuclear systems, ranging from projects such as SNAP-10A to more recent ones, including Kilopower. Although solar panels or batteries have powered many missions in the past, they have limitations in regions with long night periods, shadowed crater regions, or regions with dust storms. A nuclear reactor does not have these limitations, offering constant power to enable habitat, mobility, science, or resource utilization missions.
As proposed, the lunar surface reactor will provide at least 40 kilowatts of electrical power, sufficient for 30 typical residential homes, for a period of ten years. Such a system will be able to provide base modules for the Artemis missions, charge rovers, and provide life support and research equipment with continuous operation. The technical development of this system has been initiated by NASA’s Glenn Research Center with funding from the Space Technology Mission Directorate’s Technology Demonstration Missions program at the Marshall Space Flight Center.
This is a challenging design task. The device must be small enough to fit in a spacecraft’s payload bay, strong enough to withstand the forces of launching and landing, and capable of operating on its own once deployed. Designs being considered include gas-cooled Brayton, liquid-metal Stirling, and thermoelectric conversion schemes, each with different trade-offs of weight, efficiency, and operating temperature. For instance, it has been shown that a low-weight design of about 5,300 kg could use a liquid-metal Stirling converter with a stainless steel reactor, while a refractory reactor could use the Brayton conversion principle at about 4,200 kg.
In 2022, contracts were awarded to three industry teams: Lockheed Martin with BWX Technologies and Creare, Westinghouse with Aerojet Rocketdyne, and IX, a joint venture of companies Intuitive Machines and X-Energy with Maxar and Boeing. The preliminary designs will inform the final flight-certified system expected to be launched before the end of this decade. The demonstration mission will prove its functionality in the lunar environment. The next step would be to build systems for Mars.
Another area of importance is fuel supply. The fuel that will be used in this reactor is low-enriched uranium, and DOE is trying to increase its production capacity through its HALEU Availability Program. This involves processing material from research reactors that are government-owned and then lowering its enrichment to meet the desired levels, as well as developing centrifuge enrichment capacity to meet the fuel requirements of next-generation reactors.
Safety is also a core part of this program. Organizations like Sandia National Laboratories are tasked with probabilistic risk assessment and safety analysis reports to ensure compliance with mission safety standards during a launch. Such reports consider possible accident scenarios during a mission, either during a launch, landing, or during its operation. For NASA and DOE, however, the lunar reactor is much more than a mission milestone. It is a key enabling technology that embodies their “Moon to Mars” concept. By demonstrating that nuclear fission is capable of providing reliable and long-term power in a hostile environment, they hope to unlock the door for permanent presence and exploration in our solar system.