If you’ve ever wondered why NASA’s recent space missions haven’t made more aggressive use of nuclear power, the Space Administration’s Office of the Inspector General issued a report this week that may have your answer. The decade-long project to develop better nuclear space systems is, to put it lightly, a bit of a mess.
The NASA OIG’s report [PDF] reviews NASA’s Radioisotope Power Systems (RPS) program, which began in 2010 with the goal of developing next-generation power systems for spacecraft. Despite an average yearly investment of nearly $40 million, “NASA has not produced a viable new RPS technology since the Program began,” the OIG says in its report.
The OIG’s assessment of the program doesn’t get much better from there. According to the report, the org “lacks a clear resource allocation strategy” to ensure its projects are actualized. Along with that, the program makes “optimistic assumptions about the maturity” of its technology, leading to two projects ultimately being canceled.
Those two technologies – the Advanced Stirling Radioisotope Generator (ASRG) and the Enhanced Multi-Mission Radioisotope Thermoelectric Generator (eMMRTG) – faced various issues. In the ASRG’s case, it was in development well before the RPS program kicked off, but was canceled in 2013 because of a technical setback, coupled with “underestimation of cost and schedule.”
eMMRTG’s demise was due to those aforementioned maturity assumptions – it was recategorized from research tech to a flight project in 2018 “before it had achieved sufficient maturity levels,” the OIG said. Because of that, it failed to pass project reviews and was terminated a year later.
According to the OIG, “strategic funding decisions” also contributed to both project’s failures.
RPS project managers, whom the OIG spoke with as part of its investigation, said the cancellation of those two projects has disincentivized contractors in the RPS industry, which has in turn made future projects more expensive and less likely to succeed.
Because of these problems, the RPS Project hasn’t managed to offer nuclear power technology that is more cost-effective or ready for flight than existing solar power systems – or anything else for that matter. And that’s not even getting started on NASA’s need for nuclear fuel and the problems it’s facing on that front.
Per the OIG, one of the RPS Program’s primary objectives is to be the procurement source for nuclear fuel when it’s needed for NASA missions and projects, but even that has been a problem. The Department of Energy, which produces the plutonium-238 and cladding used by NASA projects, is bound by national security rules not to share too much information about its Pu-238 production, which the OIG said in turn makes it difficult to plan and propose new RPS-powered missions.
Along with that, the DoE simply isn’t producing enough fuel, the OIG added. Based on NASA’s 2022 Planetary Decadal Survey plan, NASA will need a total of 288 fueled clads (Pu-238 pellets secured inside a metal cylinder) by 2033.
Per the report, “based on our calculations using the high end of the 10 to 15 fueled clads produced per year, without a major ramp-up in production DOE can only produce about 187 fueled clads over that time period — 101 fewer than needed,” the OIG said.
Better space nuclear … when exactly?
The OIG has proposed nine recommendations for NASA leadership, including developing a resource allocation plan for the 13-year-old project, conducting regular technology readiness assessments and figuring out how to sort problems with the DoE to get a better understanding of the Pu-238 pipeline.
All of these problems, the OIG said, are being repeated in current projects, such as the Next-Gen Mod-1 flight system. That effort isn’t being adequately evaluated for technological readiness, the auditors added.
The OIG found project managers on the RPS’s next-gen nuclear projects have said they don’t want to implement oversight tools required by NASA and Congress, which the OIG said “will exacerbate an already challenging development effort.”
NASA leaders were given a draft copy of the report, and the OIG said they “concurred or partially concurred with our recommendations and described planned actions to address them.” The OIG said NASA management’s response was adequate, and so considers the recommendations resolved.
There is still no word on what “resolved” means in terms of a timeline for getting improved nuclear power systems on future spacecraft. The Reg asked NASA about this and will update this story if it is able to provide a timeline. ®
Updated to add on March 24
A spokesperson for NASA has been in touch to say the Next-Gen Mod-1 flight system does not include parts of the canceled ASRG and eMMRTG systems, which we earlier suggested. The agency told us the Mod-1 is new and the Mod-0 uses some previous parts:
No parts from the ASRG or eMMRTG systems are being used on the Next Gen RTG project. The Next Gen RTG Mod-0 incorporates parts from the heritage system, the GPHS-RTG. The Next Gen RTG Mod-1 is a new system; though its design is based on the GPHS-RTG, Mod-1 will be a completely new build.
We’re happy to make that clear.