SAMRs in Space: To Infinity and Beyond!

The push to deploy SAMRs on the Moon and in deep space has rapidly evolved from somewhat of a pipedream into something resembling an organized national push in the U.S. While recent policy moves, notably the April 14 National Space Technology Memorandum-3 (NSTM-3), issued by the White House OSTP, implementing Executive Order 14369, have outlined aggressive deployment timelines, the immediate question is no longer what the government wants to achieve, but whether the nuclear industry can deliver. That question is at the heart of a U.S. Department of Energy (DOE) April 21 Request for Information (RFI) with responses due by tomorrow (May 5), which seeks to assess whether the U.S. is realistically positioned to produce up to four reactors for space missions in five years. DOE’s RFI on the Space Reactor Industrial Base Assessment seeks industry input on the U.S.’s ability to deliver the four space SAMRs, with a focus on identifying deployment constraints rather than SAMR vendor strengths. In the words of Cooper from Interstellar: “It’s not possible. No, it’s necessary.” DOE seems to view the five-year window not as a suggestion, but as a requirement for U.S. space leadership.

While the policy framework has largely been established, with clear targets, such as deploying space nuclear systems by the end of the decade, including a lunar surface reactor ready for launch by 2030, what remains uncertain is whether the supply chain, workforce, infrastructure, SAMR designs themselves, and the fuel cycle can adhere to the government’s ambitious timeline. The latest RFI signals a shift away from high-level ambition and toward the practical challenge of putting SAMRs in space.

Industrial Base

DOE’s Space Reactor Industrial Base Assessment seeks input first on the hurdles facing deployment of SAMRs beyond Earth’s atmosphere. The RFI bluntly asks the industry to identify “what is hard, what is missing, what is at risk,” rather than simply listing technologies and leaving room for hope as a strategy. This hurdles-first approach underscores that while space-bound SAMRs are maturing, scaling those paper reactors into physical units that can operate reliably in some of the harshest environments conceivable is a fundamentally different challenge.

Additionally, DOE’s mandate examines the feasibility of deploying up to four SAMRs over a five-year period, which raises questions about the industry’s ability to deliver. Unlike SAMR projects underway today, with timelines seemingly stretching out forever, space SAMRs are being compressed into a tight deployment horizon, with minimal room for delays. The RFI explicitly calls out potential pinch-points, such as long-lead components, fuel availability, and manufacturing throughput, which underscores that even just a few units progressing in parallel can strain this nascent SAMR segment.

Technology

A notable aspect of the RFI is its technology-agnostic approach. Rather than defining a specific reactor or fuel type for off-Earth missions, DOE has instead asked industry to return a range of technologies with various electrical outputs (<10 kWe to >100 kWe), fuel forms (HALEU TRISO, metallic fuels, or alternatives), heat transport systems (including heat pipes, liquid metal, or gas), and mission profile (orbital, lunar surface, or deep space). At the same time, the RFI focuses on the SAMR itself, from the reactor core through the power conversion system, while excluding broader spacecraft systems. This ultimately highlights that the assessment is less focused on a particular mission and more about whether the SAMR technologies can be produced, qualified, and delivered in enough time to meet the government’s four-unit objective by the end of the decade. Additionally, respondents are specifically asked to identify issues like regulatory timelines, workforce development challenges, and facility limitations that create the largest structural bottlenecks. Of course, boosting funding can accelerate some aspects of development, but certain constraints, including licensing, testing, and fuel supply availability, appear to be hard caps on how quickly SAMRs can be deployed in space.

Supply Chain

The RFI calls on industry to identify sole-source and foreign dependencies within the supply chain, which is likely unsurprising given that the program is rooted in national security aims. However, it is notable that the supply chain for space-based SAMRs remains both highly specialized and relatively shallow. Here, DOE wants to understand which key components rely on the fewest number of suppliers, including advanced fuels, I&C, heat transfer systems, and power conversion technologies. In some cases, those suppliers may be outside the U.S., which adds additional layers of geopolitical risk to the equation. Hence, the RFI directs respondents to provide detailed input on these focal areas, which suggests that DOE seeks to understand both current capabilities and potential pinch points that could upend deployment altogether. This supply chain sensitivity is particularly relevant given the government’s compressed production target. Even a single snag, either due to limited manufacturing capacity or reliance on a sole-source supplier, could upend an entire SAMR system’s chances. As a result, the industrial base assessment is likely to place as much weight on resilience and redundancy as on raw capability.

Policy Ambition, Industrial Action

DOE’s RFI clearly demonstrates that policy alone will not guarantee the SAMR sector’s moonshot dreams are achieved. The challenge now is to translate the government’s policy push into a project pipeline capable of delivering SAMRs on schedule. This includes not only reactor design and fabrication, but also fuel production, and testing.

While we’re on the topic of fuel, it is noteworthy that HALEU is expected to play a key role in early space reactor systems. However, its limited availability and constrained deconversion and fabrication capacity are well-known restricting factors today. These kinds of constraints are precisely what the DOE is attempting to quantify through the RFI process. No SAMR vendors have publicly confirmed plans to respond to the RFI, which is not unexpected given the confidential nature of the process. However, the current SAMR vendor landscape is not entirely opaque. Several companies are already engaged in other missions with NASA through its Fission Surface Power initiative, including teams led by Westinghouse, BWXT, and X-energy. Beyond these programs, a growing group of microreactor developers, such as Radiant, Antares, and NANO Nuclear Energy, are also developing space-centric SAMRs. While the respondents to DOE’s new RFI remain unknown today, the list of vendors working to develop space-based SAMRs highlights the fact that HALEU TRISO fuel appears to be emerging as the leading fuel choice, though some other reactor concepts could emerge with other fuel options. Regardless, near-term fuel demand for space reactors is minimal. Early units will operate at tens of kilowatts, with only a handful of initial deployments, making their share of the broader nuclear fuel market negligible. However, their importance lies in the long run as space-focused SAMRs scale to support future missions.

Conclusion

Ultimately, the space nuclear sector is approaching an inflection point. Policy support, government programs, and private-sector activity appear to be clearing the path to deployment, although execution challenges abound. Progress will depend on ensuring industrial capacity can conform to policy ambitions. Even a few successful SAMRs in space would go a long way to show that space reactors can be built and deployed reliably, laying the groundwork for broader SAMR use in future space operations. If successful, the first few deployments would mark one small step for SAMRs that could set the trajectory for decades to come. We will continue to monitor the SAMR space race and how the DOE’s latest RFI unfolds; in the meantime, keep your eyes on the skies, and May the Fourth be with you.

This article was originally published in the May 4, 2026 issue of the Ux Weekly.