Among the executive orders President Trump issued during his last weeks in office was “Promoting Small Modular Reactors for National Defense and Space Exploration,” which builds on the Space Policy Directives published during his term. The order, issued on January 12, calls for actions within the next six months by NASA and the Department of Defense (DOD), together with the Department of Energy and other federal entities. Whether the Biden administration will retain some, all, or none of the specific goals of the Trump administration’s space nuclear policy remains to be seen, but one thing is very clear: If deep space exploration remains a priority, nuclear-powered and -propelled spacecraft will be needed.
The prospects for near-term deployment of nuclear propulsion and power systems in space improved during Trump’s presidency. However, Trump left office days after a hot fire test of NASA’s Space Launch System (SLS) rocket did not go as planned. The SLS rocket is meant to propel crewed missions to the moon in 2024 and to enable a series of long-duration lunar missions that could be powered by small lunar reactor installations. The test on January 16 of four engines that were supposed to fire for over eight minutes was automatically aborted after one minute, casting some doubt that a planned November 2021 Artemis I mission can go ahead on schedule.
NASA gets an order: “The sustainable exploration of the moon, Mars, and other locations will be enhanced by small modular reactors deployed from earth for operations across the solar system,” according to the White House release accompanying the order. “NASA will explore the use of nuclear energy systems for human and robotic exploration missions through 2040.”
The executive order defines “small modular reactor” as any advanced nuclear reactor with a generation capacity of less than 300 MWe and uses that term to encompass microreactors of less than 10 MWe, including transportable microreactors. The order reiterates that advanced reactors will require a viable commercial source of high-assay, low-enriched uranium (HALEU).
Trump ordered that within 180 days, “The NASA administrator, in consultation with heads of other executive departments and agencies, as appropriate, shall define requirements for NASA utilization of nuclear energy systems for human and robotic exploration missions through 2040 and analyze the costs and benefits of such requirements.”
Earlier policy steps: Trump’s Space Policy Directive-1 (SPD-1) was issued in December 2017. Briefly, that directive calls for NASA to “lead an innovative and sustainable program of exploration with commercial and international partners to enable human expansion across the solar system and to bring back to earth new knowledge and opportunities. Beginning with missions beyond low-earth orbit, the United States will lead the return of humans to the moon for long-term exploration and utilization, followed by human missions to Mars and other destinations.”
While SPD-1 included no mention of nuclear, realizing the space exploration goals that it set out would require the high-energy density of nuclear power. Less than two years later, in August 2019, Trump signed National Security Presidential Memorandum-20, “Launch of Spacecraft Containing Space Nuclear Systems,” calling for the development of space nuclear systems and establishing safety and security requirements for the launch of both radioisotope and fission powered systems.
In development: Space Policy Directive-6, released on December 16, called for work in four major fields: nuclear fuels, fission reactors for surface power, thermal propulsion technology, and radioisotope power systems for space exploration. Specific goals of SPD-6 include the following:
- Develop capabilities that enable the production of fuel suitable to a range of planetary surface and in-space power and propulsion applications by the mid-2020s.
- Demonstrate a fission power system on the moon by 2027.
- Establish technical foundations and capabilities that will enable options for in-space nuclear propulsion by the late-2020s.
NASA, the DOE, and the DOD are already working on related projects, and NASA has turned to private companies to solicit designs for a fission surface power reactor for lunar demonstration by 2027 and for nuclear thermal propulsion and radioisotope power systems.
Defense coordination: In the words of the January 12 White House press release, “At President Trump’s direction, the Department of Defense . . . will pilot a transportable small modular reactor for a mission other than naval propulsion for the first time in half a century,” an apparent reference to space nuclear propulsion. The order also calls for an analysis of military uses for space nuclear power and propulsion technologies and an analysis of foreign adversaries’ space power and propulsion programs.
President Trump’s orders to the DOD encompassed both space and terrestrial nuclear power. Land-based, transportable microreactors could increase energy flexibility and energy security at domestic military installations in remote locations. Trump ordered the secretary of defense to “within 180 days of the date of this order, establish and implement a plan to demonstrate the energy flexibility capability and cost-effectiveness of a Nuclear Regulatory Commission–licensed microreactor at a domestic military installation,” and to follow a successful demonstration with additional domestic installations.
Trump further ordered the secretaries of the departments of State, Defense, Commerce, and Energy, together with the NASA administrator, to “develop a common technology road map through 2030 that describes potential development programs and that coordinates, to the extent practicable, terrestrial-based advanced nuclear reactor and space-based nuclear power and propulsion efforts.”