NASA's announcement that it will accelerate the Fission Surface Power program, targeting deployment of a 100-kilowatt nuclear reactor on the moon by 2030, represents an ambitious acceleration of extraterrestrial energy strategy. From 2021-24, Katy Huff, a professor of nuclear, plasma and radiological engineering at the University of Illinois Urbana-Champaign, held multiple positions in the U.S. Department of Energy, including that of assistant secretary for nuclear energy. Huff shares her perspective on the technical, logistical and policy challenges NASA's effort entails, as well as the benefits of nuclear fission as power source for space infrastructure, with News Bureau writer Maeve Reilly.
Is a reactor on the moon a good idea?
Nuclear energy is uniquely suited for supporting sustained lunar and Martian missions. Because of nuclear energy's high power density and 24/7 resilient operations, NASA has selected nuclear fission power as the primary surface power generation technology for future lunar bases and crewed missions to Mars. Indeed, to deploy a fission reactor on the lunar surface in support of scientific discovery is a noble task. However, completing this task by 2030 would be a monumental undertaking.
If this milestone can be achieved, it will be the result of precision engineering, rigorous safety planning and sustained institutional investment. And, if it succeeds, it will offer an unprecedented opportunity to demonstrate clean, stable energy in the most remote and extreme environment yet.
How would one construct a nuclear reactor in space? Could we even get the materials there?
It's best to deliberately avoid extraterrestrial reactor construction. Instead, the reactor should be fully assembled and fueled on Earth, transported via rocket to the moon or Mars, and deployed at the landing location with minimal setup. Once situated on a stable and level surface, the reactor would need to be activated remotely or by astronauts on site.
Transporting a nuclear reactor to the moon involves overcoming significant mass and size constraints. The original NASA specification called for a complete fission system that could fit within a single launch vehicle payload and weigh less than 6 metric tons while producing 40 kilowatts of electricity. The revised 100 kW goal could power approximately 80 average American homes but will strain those mass limits further. Though I'm no rocket scientist, I know that the cost of sending people and objects to the moon is driven by their mass, and landing systems also will need to account for the reactor's size and weight. Still, with careful systems engineering, these constraints can be managed.
Is the 2030 timeline feasible?
The 2030 target does not align well with recent budgetary trends. NASA's funding has been reduced in the most recent appropriations cycle, raising concerns about whether adequate support will remain for its broader portfolio of missions. Accelerating the FSP program could come at the expense of other critical priorities, including earth science, climate observation and space-based weather forecasting - all core elements of NASA's public-serving mission.
How would the power be used or stored?
The reactor would rely on uranium fuel to sustain a nuclear chain reaction, producing thermal energy. This heat would be converted into electricity using a closed Brayton cycle power conversion system - a requirement specified in the new directive. The generated electricity could be distributed via cable to lunar infrastructure such as habitats, life-support systems, scientific laboratories, communications and rovers. Because the reactor would likely produce electricity continuously, the lunar installation may optionally deploy battery systems to store excess power for use during peak demand periods. The overall system must be designed for reliability and efficiency across a range of mission needs.
Would nuclear reactions work the same way on the moon?
At the fundamental level, nuclear fission reactions operate independently of gravity and atmospheric pressure. However, reactor engineering must account for environmental conditions. Heat transfer fluids will behave differently in lunar gravity, and the design must ensure consistent thermal management in the moon's extreme temperature cycles - swinging up to 200°C from day to night! The reactor must be designed to reach and maintain target operating temperatures in an environment where heat loss or retention will differ markedly from Earth. The system will also need to be fully enclosed to isolate the fuel and coolant from the lunar environment.
What are the safety implications of putting a reactor in space?
Safety concerns fall into two primary categories: launch safety and operational safety on the lunar surface. During rocket launches, there is always a risk of failure. If a rocket carrying a reactor were to explode or fall back to Earth, it could potentially disperse radioactive material. To mitigate this, the reactor would launch in an unirradiated state, using fresh uranium fuel that is only weakly radioactive. Additionally, a radiological contingency plan has been developed for any launch involving nuclear material to comprehensively prepare for response to an accident. There's even a Radiological Control Center at NASA's Kennedy Space Center with special radiological incident response capabilities and highly trained staff who regularly rehearse communications and coordination.
Once on the moon, the safety focus shifts to shielding, containment and autonomous control. All of these challenges will need to be addressed long before the launch date through a robust, safety-focused engineering design process. For example, the reactor must be designed to automatically shut down safely and reliably under any off-normal conditions, like moonquakes, just as terrestrial reactors are designed to do.
Where would the waste go?
That remains an open design question. Spent fuel from the reactor will contain fission products that are significantly more hazardous than the fresh uranium fuel launched from Earth. Bringing that material back to Earth presents more serious risks, especially in the event of an uncontrolled reentry. Historical precedent underscores the risks: in 1978, the Soviet Kosmos 954 satellite, powered by a nuclear reactor, reentered Earth's atmosphere and scattered radioactive debris across a 600 km stretch of Canada. A more practical solution may be to store the waste on the lunar surface in shielded containment structures.
What kind of maintenance would be needed?
Unlike the large-scale reactors used for civilian power grids, space reactors are designed for autonomous operation. NASA's current design targets call for the reactor to operate for 10 years without requiring refueling or physical servicing. While it is always possible that unexpected issues could arise, the system should be designed to minimize those risks and continue operating without intervention for the full mission duration.
