Is it science fiction to consider living on the moon or traveling to Mars in only a few months? Maybe not. The US government is promoting technologies to place nuclear reactors in space to power human existence on the moon and to propel spacecraft to Mars.
In July 2020, the US National Space Council released a strategy for deep space exploration. The strategy includes developing a power reactor to produce electricity to support a long-term human presence on the moon and exploring nuclear propulsion to decrease deep-space travel time. Current nuclear power space systems rely on radioisotope decay to provide small amounts of power to operate systems on spacecraft. Those systems are inadequate for larger missions. A fission reactor is needed to support long-duration lunar exploration, and it is needed soon—the United States wants to land Americans on the moon’s South Pole by 2024 and establish a sustainable human presence on the moon by 2028!
Consistent with these priorities, the NASA-led Kilopower project is developing a 10 kW fission reactor for crewed planetary bases. The Kilopower project team completed preliminary testing in March 2018, and is moving toward flight demonstration. NASA also is evaluating nuclear thermal propulsion (NTP) and nuclear electric propulsion (NEP) as a part of a Mars Transportation Architecture Study. While both systems use a nuclear reactor to generate heat, NTP systems use it to expel gas, and NEP systems convert the heat into electricity to power a thruster. In the fall of 2020, Ultra Safe Nuclear Technologies and General Atomics submitted concepts for NTP designs to NASA.
NASA is considering whether to power these reactors with high-assay low-enriched uranium (HALEU) fuel instead of high-enriched uranium (HEU), which poses a proliferation risk. But HALEU is in short supply. The US Department of Energy (DOE) recently announced plans to establish a domestic supply line for the fuel, citing demand from designers of next-generation commercial power reactors. Several companies including TerraPower and Centrus Energy Corp. and Global Nuclear Fuel and X-energy have recently announced plans to establish commercial-scale HALEU fuel production.
To promote efficiencies, the National Space Council is evaluating common features between space reactor designs and those being developed for the military. The Council’s report highlights Project Pele, which would demonstrate mobile reactors to power military bases on Earth, and the DRACO program, which would develop spacecraft that can maneuver quickly in the region between Earth and the moon. NASA has commissioned a National Academy of Sciences study to assess the primary technical and programmatic challenges, merits, and risks for developing and demonstrating space nuclear propulsion technologies.
NASA and DOE also entered into a memorandum of understanding (MOU) in October 2020. Among other things, the MOU establishes three working groups to assess the infrastructure needed on the moon’s surface, nuclear power and propulsion in space, and space science and innovation. It required those working groups to provide preliminary reports to the Executive Committee earlier this month. NASA also intends to release two solicitations related to nuclear reactors in space in 2021, the first a Fission Surface Power System Design Solicitation and the second a Nuclear Thermal Propulsion Industry Solicitation.
Just last week the White House released a new space policy directive, the National Strategy for Space Nuclear Power and Propulsion, to serve as a strategic roadmap for the use of nuclear power in space. The strategy envisions developing uranium fuel processing capabilities needed for surface power and propulsion systems by the mid-2020s, and developing and testing a surface nuclear power system for lunar missions by the late 2020s. The strategy also promotes the development of advanced radioisotope thermoelectric generators (RTGs), which have long powered a variety of NASA missions, by 2030. Finally, the strategy provides that the sponsoring agency—i.e., NASA, DOE, or DOD—must conduct a thorough technical review to assess the viability of (1) fuels other than HEU for propulsion projects and (2) fuels other than LEU for non-propulsion projects before selecting HEU for those projects.
NASA and DOE have concluded—at least for the time being—that nuclear power must be at the core (pun intended) of moon bases and space travel, and the nuclear industry is responding with zeal and incredible innovation.