Nuclear power on the moon: What we’re watching
After the Trump administration’s new push to get a nuclear reactor on the moon by 2030 was first reported by Politico last month, media played up the shock value for people new to the concept. Few focused on the technical details of the new plan for lunar fission surface power (FSP), which halts and replaces a program that began under the first Trump administration with an early hope of getting a reactor on the moon by the end of 2026. Now, the focus is on streamlining NASA’s internal processes to support commercial space companies that can build a reactor with more than twice the power and mass and have it ready for launch by 2030.
Following an August 4 directive from acting NASA administrator (and secretary of transportation) Sean Duffy, NASA is making organizational changes and preparing a request for proposals expected within 60 days of the directive. (A request for information has already been issued; respondents had just one week to reply.)
Here’s what Nuclear News has been watching in the month since the news broke, and what we know about the size, schedule, fuel, and management of NASA’s new plans.
It's a race: After Politico broke the news August 4, Duffy confirmed the plans on August 5 in comments during a live-streamed Department of Transportation press conference on drone technology.
“We're in a race with China to the moon, and to have a base on the moon we need energy,” Duffy said. “This fission technology is critically important. . . . There's a certain part of the moon that everyone knows is the best. We have ice there. We have sunlight there. We want to get there first and claim that for America.”
Russia and China announced plans in March 2024 to build a nuclear plant on the moon together. The NASA directive focuses on speed, saying the first country to get a reactor on the moon “could potentially declare a keep-out zone which would significantly inhibit the United States from establishing a planned Artemis presence if not there first.”
Unlike the United States, Russia and China have not signed the 2020 Artemis Accords. The Artemis Accords don’t recognize permanent claims of lunar territory but do allow lunar-landing nations to establish “safety zones” around their operations. Those safety zones are “temporary, ending when the relevant operation ceases. The signatories commit to respect the Outer Space Treaty principle of free access in their use of safety zones, as well as the principle of due regard.”
The new specs: The August 14 RFI asked companies for feedback on their interests, risks, capabilities, and preferred funding mechanisms for work on the FSP specifications laid out in Duffy’s memo. Those specs include the following:
Schedule—Reactors should be prepared to launch by the first quarter of fiscal year 2030 (that is, the last quarter of calendar year 2029).
Mass—Reactor designers can assume the use of a heavy-class lander that can carry up to 15 metric tons. (In April 2024, NASA announced that work was underway on large cargo landers capable of delivering up to 15 metric tons of cargo for Artemis moon missions.)
Power—The reactor must have a 100-kWe output using a closed Brayton cycle power conversion system. The NASA directive says the Brayton cycle is specified to “reduce risk and ensure extensibility to higher power systems.”
Financing—The directive said that financing arrangements could change, with “flexibility to NASA to award contract value based on proposed industry capability,” and with “potential industry cost-sharing (i.e., in exchange for industry owning and operating the reactor power once operational).”
In and out at NASA: Here are a few of the changes to NASA’s programs in 2025 and in the August 4 directive that impact the lunar FSP program.
The directive says NASA’s Space Technology Mission Directorate (STMD) “shall immediately cease any new FSP technology maturation efforts that don't support the [anticipated] RFP and align available FY25 funding to support the RFP initial award amount.”
The directive establishes a new position at NASA: a Fission Surface Power Program executive to “provide reporting and updates with maximum transparency” directly to Duffy. Steven Sinacore, formerly director of aeronautics at NASA’s Glenn Research Center, has been named to the role.
The directive shifts FSP from STMD to NASA’s Exploration Systems Development Mission Directorate (ESDMD), which will lead the new FSP program (through the new position of Fission Surface Power Program executive), “with support from Office of General Counsel and Office of Procurement.” NASA staffing for the program is limited to “15 full-time engineer equivalents” and a “minimum viable structure (MVS) for its management team, composed of essential civil servant roles and supported by flexible, targeted contractor expertise.” The pared-down program structure is to “prioritize agility, reduce duplication, and focus on milestone-driven delivery” and “adopt streamlined internal approval pathways that prioritize decision velocity in support of critical milestones.”
Trump’s budget request for NASA for FY2026 included $350 million for “a new Mars Technology program” to “accelerate the development of high priority technologies for Mars,” which includes FSP. The funding is set to grow to $500 million starting in FY27.
What’s been replaced: Back in July 2020, NASA wanted to launch a complete FSP flight system before the end of 2026. Idaho National Laboratory took a lead role and issued an RFI for a reactor with a power output of at least 10 kW and a flight system mass of 2–3.5 metric tons.
By the time a request for proposals was released in November 2021, the goal was for 40 kWe and a maximum mass of 6 metric tons, ready for launch “by the end of the decade.” Contractors worked through phase 1, and in January 2024, NASA expected to issue an open solicitation for phase 2 work in 2025. As recently as early January 2025, one of the awardees—Westinghouse, working with partner Aerojet Rocketdyne—announced it had received a contract to continue phase 1 work developing a scaled-down lunar version of its eVinci sodium-cooled microreactor. (Pivoting to the new specs, Westinghouse now describes its AstroVinci as capable of power ranges between 10 and 100 kWe, with either Brayton or Stirling power conversion.) The other awardees in 2022 were Lockheed Martin (partnered with BWX Technologies and Creare) and IX (a joint venture of Intuitive Machines and X-energy, partnered with Maxar and Boeing).
A team of federal researchers at NASA Glenn Research Center, Los Alamos National Laboratory, and INL had been working on their own 40-kWe designs in parallel to the contractor teams chosen in 2022, specifically to compare two technologies—a gas-cooled Brayton cycle and a heat pipe Stirling engine.
That work, which was intended to “guide future architecture decisions and technology investments,” has been stopped. But earlier this year the team published a paper concluding that both systems were viable, with mass and thermal advantages for the Stirling option and simplified architecture for the Brayton option. Both government designs came in above the mass requirement, at about 7 metric tons.
This 2017 photo shows KRUSTY, the small HEU-fueled Kilopower Reactor Using Stirling Technology, led by NASA’s Glenn Research Center. (Photo: NASA Glenn Research Center).
FSP fuel—a timeline: Neither NASA’s directive nor the August 14 RFI specify a fuel or an enrichment level. Within the last 10 years, high-enriched uranium has fallen out of favor for space applications, with high-assay low-enriched uranium becoming the fuel of choice.
In 2017, the United States successfully operated and tested a small reactor—KRUSTY, the Kilopower Reactor Using Stirling Technology—fueled by a solid core cast from high-enriched uranium (pure uranium-235).
In March 2020, according to NASA, a Department of Energy reactor study concluded that HALEU FSP reactors could be designed to roughly the same weight as the KRUSTY system.
Trump’s Space Policy Directive-6 of late 2020 said that while the use of HEU in space is not prohibited, it “should be limited to applications for which the mission would not be viable with other nuclear fuels or nonnuclear power sources.”
In November 2021, INL published a set of frequently asked questions on the FSP program that said, “FSP reactors are limited to uranium fuel. No specific uranium enrichment is required. . . . There is no additional requirement on the fuel form or type. A moderator is not required.”
According to the paper published earlier this year by members of the STMD FSP team on the 40-kWe reactor program, “Based on guidance from STMD, all design studies were to assume [HALEU] with U-235 isotope enriched to 19.75 percent.”
