NASA and the US Department of Energy have locked in a decade-long partnership to put fission reactors in space, signing a memorandum of understanding titled Accelerating American Leadership in Space Nuclear Power and Propulsion. The document was signed on 8 October at the White House Office of Science and Technology Policy’s “Science: A New Golden Age” summit by NASA Administrator Jared Isaacman and Energy Secretary Chris Wright. It takes effect on 1 November, runs for ten years unless revised or extended, and supersedes two earlier accords: a radioisotope power systems MOU from 2016 and a space fission systems MOU signed in December 2025. Interagency agreements established under those earlier documents remain in force.
The memorandum opens with the case that has driven the programme for years: “Opening the solar system to sustained human presence is the great engineering challenge of this century. It requires power that works everywhere: through the lunar night, in Mars orbit, and past Jupiter where the Sun is just another star.”
- Aggressive timeline: Space Reactor-1 Freedom is slated to launch in December 2028, with Lunar Reactor-1 targeted for the lunar surface by 2030.
- Propulsion payoff: Fission-based designs could compress a Mars transit from 6-9 months to roughly 3-4 months, cutting crew radiation exposure and consumable mass.
- Strategic race: China and Russia both have active space nuclear programmes, while the 1967 Outer Space Treaty leaves fission reactors in a legal grey zone.
Two reactors, two deadlines
Space Reactor-1 Freedom (SR-1) is described by NASA as humanity’s first fission-powered interplanetary spacecraft, an nuclear electric propulsion demonstrator aimed at moving reactors out of the laboratory and into operational deep space. Its mission, named SkyFall, is bound for Mars. The fission reactor is designed to start up 48 hours after the craft escapes Earth’s gravity, then drive electric thrusters for the cruise. Its scientific payload packs three Ingenuity-class helicopters carrying cameras, ground-penetrating radar and radios, tasked with surveying candidate human landing sites, probing for subsurface water and relaying navigation data for later landers.
Lunar Reactor-1 (LR-1) follows. It is a fission surface power system meant to keep a planned Moon Base running through the two-week lunar night and inside permanently shadowed craters where solar arrays are useless. A 2025 Executive Order on Ensuring American Space Superiority directs NASA to have a launch-ready lunar surface reactor by 2030, a goal the agency says it is pursuing with “steady progress” alongside the DOE. Flying a reactor before any lunar landing, NASA argues, retires nuclear flight risk, qualifies the supply chain and builds the specialist workforce the later missions will need.
Why fission rewrites the maths
Space exploration has relied on solar panels and radioisotope generators for decades, but both hit hard limits beyond Mars, where sunlight is too weak to feed ambitious missions. Under the new MOU, NASA keeps mission and programme authority, while the DOE designs, fabricates, tests and delivers the hardware, including fuel production and authorisation of nuclear materials, with safety analysis required unless the Nuclear Regulatory Commission licenses an activity. NASA may also procure commercially developed space nuclear systems.
Fission’s appeal is not limited to reactors. NASA continues to deploy radioisotope power systems, which have energised spacecraft since 1961. The Dragonfly mission to Saturn’s moon Titan, launching in 2028, will rely on a Multi-Mission Radioisotope Thermoelectric Generator plus 24 Light Weight Radioisotope Heater Units to power and warm the car-sized rotorcraft as it hops between landing sites. NASA and the DOE also plan to supply 24 similar heater units to the European Space Agency’s Rosalind Franklin Mars rover.
“We are entering the ‘Nuclear NASA era,’ which represents a major transformation for space exploration,” Isaacman said. “Nuclear power will allow us to go farther, operate longer, and field more capable spacecraft and instruments than ever before. The work we’re doing today is laying the foundation for the fission-powered spacecraft of tomorrow.”
Competition, dual use and the fine print
The agreement lands inside a race that is rarely labelled as such. China has announced a nuclear propulsion reactor for its lunar missions in the 2030s, and Russia has the Zeus project, which includes a nuclear space tug intended to be operational before 2030. Private industry adds its own pressure: operators including SpaceX and Blue Origin need more efficient propulsion for ambitions beyond Earth orbit.
The awkward part is dual use. The same reactors that warm a lunar habitat could, in principle, feed orbital kinetic weapons platforms, a dimension absent from the official communiqués. The 1967 Outer Space Treaty bans nuclear weapons in space, but it says nothing about fission reactors, leaving a wide legal corridor. This is not NASA’s first attempt — the Prometheus project, cancelled in 2005 under budget cuts, promised something similar and died quietly.
What makes 2028-2030 plausible rather than aspirational is convergence. Bipartisan political backing exists where it did not twenty years ago, terrestrial small modular reactor programmes are accelerating partly to meet AI’s energy demands, and lessons in miniaturisation, waste handling and passive safety transfer directly to flight hardware. If SR-1 leaves the pad on schedule, the United States will have converted a laboratory concept into an industrial base — and set a pace that rival programmes will spend years trying to match.