Lunar Nuclear Fission System

Summary. A nuclear fission power system that "NASA added … into its lunar architecture" in 2025. It supplements elements' own solar power, supports operations "during the lunar winter", and powers demonstrations such as ISRU (ADD Rev C, p. 58). It is the only element in Power Systems, new in Rev C, in the Foundational Exploration segment, and Rev C ties it to NASA's selection of fission as the primary surface power for the first crewed Mars missions. A later NASA page announces Lunar Reactor-1 under the same project name, to land in 2030. All three of its functions (generate, distribute, and power utilization payloads) are on the Moon Base Phase 1 list of functional gaps (the wiki's join, below).

All page numbers are ADD Rev C unless noted.

NASA's description

"In 2025, NASA added a nuclear fission power system into its lunar architecture. This external power augmentation can supplement onboard solar power systems for existing elements (e.g., for habitation and mobility systems), support expanded exploration activities (e.g., operations during the lunar winter), and enable technology demonstrations with greater power needs (e.g., for in-situ resource utilization).

Development of this system for the Moon also demonstrates critical Mars-forward technologies, responding to NASA's selection of nuclear fission as the primary surface power generation technology for initial human Mars missions. Additionally, using the system on the lunar surface empowers NASA to develop operational competencies and reduce risk for nuclear power systems in crew architectures at other destinations." (p. 58)

At a glance

From the element one-pager (p. 58).

ADD section	2.3.8 (p. 58)
Implementing program	Fission Surface Power; printed beneath: NASA's Glenn Research Center
Functional mappings	Appendix B, B.3.8 (B.3.8.1 in the Foundational Exploration table, p. 31)
Segments	Foundational Exploration only
Sub-architecture	Power Systems
Added in	Rev C: "lunar nuclear fission system element" (p. 9)
Header image	"Rendering of a government reference concept for a lunar surface power system utilizing nuclear fission. (Credit: NASA)"

It is the only element whose one-pager prints a NASA center, not a program office or mission directorate, beneath its implementing program (elements index).

Names. The Foundational Exploration table calls it "Lunar Nuclear Power System" (p. 31), and the Section 2.3 table (pp. 45–46) leaves it out (elements index). The Human-Class Delivery Lander names "future surface power elements" among its large cargo (p. 56). The 2025 Architecture Update has the same split: "Lunar Nuclear Power System" in its contents (p. 2), "Lunar Nuclear Fission System" on the page itself (p. 7).

The 2025 Architecture Update

The 2025 Architecture Update (Dec 2025, released with Rev C) gives the element a page of its own (p. 7). Page numbers in this section are the Update's unless marked ADD.

Its description. The first two paragraphs repeat the ADD's, with small changes: "NASA instantiated a nuclear fission power system into its lunar architecture" (the ADD says "added"), and "supplement power systems onboard existing elements" (the ADD says "onboard solar power systems"). It then adds: "For additional information about NASA's power needs as the architecture evolves, and how lunar power systems address those needs, refer to this year's 'Integrated Lunar Power Considerations' white paper. Inclusion of this power system in the architecture lays the foundation for future lunar infrastructure investments supporting a robust, sustained human presence on the Moon's surface" (p. 7). That white paper, titled "Integrated Lunar Power Strategy Considerations" on its first page, is read below.

Functional mapping. The Update prints three functions for the Foundational Exploration segment (p. 7). They match ADD Appendix B.3.8.1 (ADD Rev C, p. 158, checked):

ID	Function (p. 7)	Moon Base Phase 1 functional gap?
FN-P-101 L	Generate power in the south pole region on the lunar surface	yes, power group
FN-P-301 L	Distribute power in the south pole region on the lunar surface	yes, power group
FN-P-401 L	Provide power for deployed surface utilization payload(s) and/or equipment	yes, power group

The last column comes from the Users Guide's list (Phase 1 functional gaps); joining the two lists is the wiki's work. The power group's other two functions, FN-P-102 L (store energy) and FN-P-402 L (power utilization payloads for month-plus to year-plus durations), are not mapped to this element.

"Store energy" is the Users Guide's title for FN-P-102 L. In the ADD's own list, FN-P-102 L is "Generate power at multiple distributed locations outside of the south pole region on the lunar surface", and the guide's title belongs to FN-P-202 L (ADD Rev C, p. 121). The wiki doesn't decide which the guide means (Lunar functions; open question 40). Neither function is among this element's three.

In the rest of Appendix B:

• Also listed as unallocated. The ADD's B.5 lists FN-P-101 L under UC-P-101 L, and FN-P-301 L under UC-P-301 L and UC-U-201 L, as unallocated (pp. 174, 178). So the ADD both maps them to this element and lists them as unallocated, as the lunar spreadsheet does. Neither source says why.
• No other element is mapped to FN-P-101 L or FN-P-301 L. The Initial Surface Habitat shares FN-P-401 L (p. 157).

• Power still unallocated in B.5:

  • energy storage at the South Pole (FN-P-202 L)
  • generation, storage and distribution at distributed sites (FN-P-102 L, FN-P-201 L, FN-P-302 L)
  • payload power in deep space (FN-P-304 L)

  (B.5 by use case)

• Nuclear functions elsewhere. The spreadsheet gives FN-G-106 L and FN-G-107 L, ground services and launch "to support large nuclear assets", to Exploration Ground Systems. No ADD table for Foundational Exploration names either (Exploration Ground Systems). Neither source ties them to this element.

Elsewhere in the Update:

• Why power needs it. "While the elements used in early Artemis missions are self-sufficient from a power perspective (i.e., they can generate all the power they need using solar power systems), operating in more locations and for longer at the lunar South Pole will require additional, continuously available power to operate when solar power is not sufficient and to maximize the mass efficiency of individual systems. NASA is initiating elements like the lunar nuclear fission system to fulfill this need and is developing systems that can distribute and store power as needed" (p. 9; see Power Systems).
• What it adds. "the addition of the lunar surface fission system this year significantly increases the power that the architecture can provide" (p. 16; see Architecture definition process).

The ACR25 lunar power white paper

The white paper "Integrated Lunar Power Strategy Considerations" discusses fission at length but never names this element (search of its text). Page numbers in this section are the paper's. Its general points on power are on Power Systems.

What it says about fission (p. 4):

• The case for it. "Unlike solar power, fission systems can produce continuous, predictable power regardless of access to sunlight or changing environmental conditions. Nuclear technologies also scale effectively, offering a higher power-to-mass ratio than solar power, meeting power needs as they grow over the course of the exploration campaign. A single large reactor can provide power to multiple elements; multiple smaller reactors can enable exploration at many different locations."
• What it takes. "Developing nuclear fission systems qualified for human spaceflight and of sufficient power output to support human-class exploration elements requires technology development investments. NASA may also need to adapt or construct specialized facilities to build larger space-rated fission power systems. However, space fission technology development can leverage previous NASA and the U.S. Department of Energy research investments."
• Extra considerations. "Processing, launching, deploying, and operating nuclear fission systems introduces additional engineering, safety, logistical (e.g., fuel availability), and regulatory considerations (e.g., ensuring that crew members are properly shielded from radiation)."
• Against solar, in the paper's table: availability "Continuous"; maturity "Prior experience limited to low-power, radioisotope power systems"; unique factors "Human-rated radiation shielding; long-distance power cabling".
• Storage. "Nuclear power's continuous output reduces the net energy storage requirement" (p. 5).

Mars-forward (p. 5). "In 2024, NASA identified nuclear fission as the primary surface power generation source for initial human missions to Mars". The paper gives no task ID; the ADD records this decision as MD-07 (Key definition tasks). "Including the development of nuclear power systems for lunar applications in the agency's integrated lunar power strategy reduces risk and builds operational competencies for its use on the Red Planet. In addition, designing common nuclear systems and technologies for both Moon and Mars exploration can offer cost and schedule benefits."

An announcement and an element still to come (p. 5):

• "In August of 2025, acting NASA Administrator Sean Duffy announced plans to develop a nuclear power system for the lunar surface. This directive helps to address the power considerations addressed in this paper and leverages prior technology investments and architecture integration studies."
• "NASA plans to debut its full integrated lunar power strategy based on the considerations outlined in this paper in the coming years. Alongside that strategy, the agency will initiate an integrated surface power element into the architecture to realize functional capabilities for external power augmentation." The takeaways say NASA "is initiating new power elements into the architecture" (p. 6).

The ADD, from the same review cycle, says this element was "added" in 2025 (ADD p. 58). The paper uses the future tense and doesn't say whether the "integrated surface power element" is this element, another one, or both. The wiki doesn't identify them (open question 32). Nor does it tie the August 2025 announcement to Lunar Reactor-1 (below).

In the ACR24 white papers (2024)

The 2024 paper "Mars Surface Power Technology Decision" (source page) predates this element and names no lunar element. Its section "The Moon as a Testbed for Mars" (p. 4) says: "The Moon's proximity to Earth offers opportunities to demonstrate candidate Mars surface power generation technologies with reduced consequences of failure." To carry over to Mars, lunar systems "would need to account for the environmental differences, including Mars' atmosphere, increased gravity, shorter day/night cycle, wind loads, dust storms, communications delay, etc. While implementing Mars-forward technologies at the Moon could add cost or complexity, surface power technology demonstrations during the Artemis campaign would significantly reduce risk for initial crewed missions to Mars." Setting this beside the element is the wiki's pairing; the ADD ties the element to the Mars selection itself (p. 58). The paper's account of that selection is on Key definition tasks.

Gaps that mention it

No gap names this element. Two power gaps describe fission's state of the art in the same words: "There has been one brief ground test of a kW-scale fission power system intended for space ("KRUSTY" in 2018)" (tech gaps spreadsheet, ESDMD #0901 and #0902):

• #0901 Scalable Lunar Surface Power Generation (rating 13; Moon Base)
• #0902 Scalable Mars Surface Power Generation (rating 45; Mars only)

Distributing the power is #0903 Power Management and Distribution. None of the element's three function IDs appears in the tech-gap spreadsheet (search of its text).

Changes since Rev C

• A name and a date. NASA's Lunar Surface Technology page, under "Fission Surface Power", says: "In response to the National Space Policy, NASA announced Lunar Reactor-1, the first fission nuclear reactor on the Moon, will land on the lunar surface in 2030" (Lunar Surface Technology, "Fission Surface Power"). Rev C gives no date. Whether Lunar Reactor-1 is this element is discussed below.
• Briefed at the January 2026 workshop: proposals under way. NASA's workshop for industry and academia (21–22 January 2026) told attendees that "Most NASA representatives may not discuss fission surface power system proposals during the pre-solicitation and solicitation periods", and pointed to "the draft announcement for partnership proposals" and "the fission power system technical library", both on sam.gov (slide 18) (2026 industry and academia workshop, slide 18). The slide names no element, reactor or date. The same deck shows this element as a "NEW ELEMENT" (slide 12), a rendering with no text.
• What LR-1 is for, and SR-1 first. NASA's Ignition fact sheet on nuclear power (24 March 2026): "LR-1 lands on the Moon in 2030 — first fission nuclear reactor on the Moon". SR-1 Freedom, a nuclear electric propulsion spacecraft launching to Mars in December 2028, "will inform and enable Lunar Reactor-1 (LR-1), a fission surface-power system designed to keep the Moon Base operating through periods of darkness and in locations where solar power alone cannot reach. By flying a reactor first — without the added complexity of a lunar landing — SR-1 retires nuclear flight risk, stimulates and qualifies the supply chain, and builds the necessary workforce." Why fission: "even the best polar sites face days of darkness, and the permanently shadowed craters where ice exists see no sunlight at all" (nuclear power fact sheet, p. 1). The fact sheet gives SR-1 "more than 20 kilowatts of electrical power" from "Brayton power conversion" (p. 2), and no power level for LR-1.
• Fission in the Moon Base phases. The Building the Moon Base fact sheet of the same day has "initial nuclear-based power stations (potentially including both fission reactor and RTGs)" in Phase 2 (2029–2032) and "An operational fission surface power station with sufficient power to provide steady, reliable energy through the long lunar nights, leveraging in situ resource manufacturing" in Phase 3 (Building the Moon Base fact sheet, p. 1). It names neither LR-1 nor this element.
• Briefed at Ignition, March 2026: a reactor demonstration in Phase 2, fission power in Phase 3. The Moon Base Program's deck has a Phase 2 "Key capability", "Nuclear Surface Power Capability": "Demonstrate technologies, processes, and operations for future larger scale nuclear power/propulsion"; "Demonstrate thermal management concepts and methods for larger scale future applications"; "Used as power generation stations"; "Used within assets to enable night survival and permanently shadowed region exploration"; "Demonstrate reactor surface power" (slide 26) (Ignition deck 2, slide 26). Its power slides label the generation in sequence, "Phase 1: Solar Battery/ RFC Power", "Phase 2: Nuclear Power", "Phase 3: Fission Surface Power" (slide 53). In the table by phase, Phase 2 deploys "Radioisotope Thermal Generator (RTG) Power Stations" beside solar stations and has "Demonstrate reactor surface power"; Phase 3, "Enabling Power Distribution", opens with "Fission Surface Power", then "Power distribution deployed to support habitats and surface assets" and "Permanently Shadowed Region exploration" (slide 54). Phase 3's figures list "fission surface power" among its payload (slide 30) (Ignition deck 2, slides 30 and 53–54). The deck names no reactor, project or element: not LR-1, not this element. Its "Phase 2: Nuclear Power" covers RTG stations as well as the reactor demonstration, so it isn't read as this element. Slide 42 attaches no power program to its "Infrastructure" area (Ignition deck 2, slides 41–42). The power tables by phase are on Phases.
• Briefed at Ignition, March 2026: LR-1's design trades reopen. The Space Reactor Office's deck puts "2030: Lunar Reactor-1 (LR-1)" between "2028: SR-1 Freedom" and "2030s: Scale & Production", with the line "Trade reopens. Industry competes." For LR-1: "New industry opportunity (RFI ~June 2026)", "Informed by SR-1 data", "Leverages SR-1 technology", "Adapted for lunar environment". "What SR-1 gives LR-1": "Ground & flight data on reactor and power conversion performance", regulatory and launch approval precedent, integration lessons, the industrial base and workforce, and test and launch infrastructure. "What reopens for LR-1": "Reactor and power conversion design trades"; "Surface thermal rejection architecture"; "Landing loads, dust tolerance, surface ops"; "Balance of plant optimization"; "Industry competition for build and delivery" (slide 12). Its timeline has "RFIs released for fast follow on FSP and NEP demonstrations" in June 2026 (slide 14), and its case for nuclear says it "Keeps bases operationally alive through the lunar night" and "Enables resource manufacturing" (slide 2) (Ignition deck 5, slides 2, 12, 14). The deck gives LR-1 no power level; the "100s kWe to MW-class" on the same slide belongs to the 2030s column. It doesn't name this element, the Moon Base or a phase.
• Who runs it, from May 2026. Directive 7 centralizes "all NASA space nuclear activities within RTMD", the new Research and Technology Mission Directorate: all space nuclear funding "across HSMD, RTMD, and SMD" goes to the Space Reactor Office, which is to plan "SR-1 targeting launch to Mars in 2028, and LR-1 ready for launch by 2030", and which takes over "radioisotope power sources" to "encourage affordable, commercial procurement of RTG and RHU's". Steve Sinacore is "Program Manager for SR-1 Freedom and LR-1" (Administrator's workforce note, 22 May 2026). Rev C's one-pager gives the element's implementing program as "Fission Surface Power", at Glenn (At a glance); the note doesn't mention that name.
• On the Moon Base Systems page (2026). Phase Three: "operational fission surface power systems capable of providing steady, reliable energy through long lunar nights"; Phase Two lists solar and radioisotope power stations, with no reactor demonstration (Moon Base Systems, "Power"). The program manager, as reported: "a nuclear reactor that can scale up to like 100 kilowatts", for ISRU and manufacturing, "in phase three, or you know, at the end of phase two" (podcast, August 2026). Neither names LR-1 or this element.
• On NASA's SR-1 mission page (2026). SR-1 will "prove fission surface power technology for NASA's Moon Base"; it flies "20 kilowatts electric closed Brayton cycle power conversion" on "High-Assay Low-Enriched Uranium (HALEU)" fuel. LR-1 is "a fission surface power system designed to keep NASA's Moon Base operating through periods of darkness and in locations where solar power alone is not sufficient", and "Together, SR-1 and LR-1 are the beginnings of a domestic nuclear-space industrial base that scales to power permanent lunar outposts" (SR-1 Freedom page). The page gives LR-1 no date or power level and doesn't name this element; the rest of it is on Mars-forward.

Moon Base relevance

• Shared function IDs (the wiki's join). All three of the element's functions, FN-P-101 L, FN-P-301 L and FN-P-401 L, are on the Users Guide's list of Phase 1 functional gaps, in its "Power systems" group (Users Guide, p. 10; 2025 Architecture Update, p. 7). The guide defines functional gaps as functions "either currently unallocated to any existing elements, or functions that need additional performance to be fully satisfied" (Users Guide, p. 9). These three are allocated to this element, but the guide doesn't say which half of its definition applies to them. Neither source makes this link (open question 11). The ADD's B.5 also lists FN-P-101 L and FN-P-301 L as unallocated (above; open question 65).
• Lunar Reactor-1 (the wiki's identification). The ADD's implementing program is "Fission Surface Power" at Glenn (p. 58). The Lunar Surface Technology page's "Fission Surface Power" section announces Lunar Reactor-1 for 2030, and the page lists a "Fission Surface Power, Project Manager at NASA's Glenn Research Center" (Lunar Surface Technology). On the shared project name, the wiki reads Lunar Reactor-1 as this element's first unit. No source says so in as many words, and none places Lunar Reactor-1 in a Moon Base phase (Missions and assets; open question 11). The nuclear power fact sheet ties LR-1 to the Moon Base by name ("to keep the Moon Base operating through periods of darkness"), still without a phase; the Building the Moon Base fact sheet puts nuclear power stations in Phases 2 and 3 without naming LR-1, and the Moon Base Program's Ignition deck has a reactor demonstration in Phase 2 and "Fission Surface Power" in Phase 3, also without naming LR-1 (above). The wiki doesn't match LR-1's 2030 landing to the deck's Phase 2 demonstration.
• Mars-forward. The Users Guide's "Nuclear technologies" area: "Developing Moon Base nuclear power systems empower Mars exploration, where NASA has already selected nuclear fission as primary power generation technology for its robustness to the planet's environment (i.e., to dust storms). These efforts also benefit nuclear propulsion development efforts for Mars transportation systems" (Users Guide, p. 14; Mars-forward). This matches the ADD's reason for the element (p. 58). The "Why Moon and Mars?" white paper (Dec 2025) makes the same point without naming the element: "Using this same technology for NASA's lunar surface infrastructure accelerates technology development into a flight project and reduces risk for subsequent Mars applications" (white paper, p. 4). How NASA chose fission for Mars (task MD-07) is on Key definition tasks.
• General. "NASA is advancing fission power technologies to provide reliable, long-term energy for future operations on the Moon" (Moon Base encyclopedia, "Did You Know?").

The Users Guide's Phase 1 power targets are "5 kW power generation and storage, as well as survival through 120+ hours of darkness" and "survive the night capability using radioisotope thermal generators" (Users Guide, p. 10). Neither names fission, so neither is tied to this element here.

Related pages

Elements · Power Systems · #0901 · #0902 · #0903 · Surface technology · Mars-forward · Foundational Exploration · Phase 1 functional gaps: power

Sources

ADD Rev C, pp. 9, 31, 45–46, 56, 58, 157–158, 174, 178 · Lunar objective decomposition, allocation sheets · 2025 Architecture Update, pp. 2, 7, 9, 16 · Lunar Surface Technology · Moon Base encyclopedia entry · Users Guide, pp. 9–10, 14 · Tech gaps spreadsheet, ESDMD #0901, #0902 · "Why Moon and Mars?" white paper, p. 4 · Lunar power white paper, pp. 4–6 · Mars Surface Power Technology Decision (2024), p. 4 · Nuclear power fact sheet, pp. 1–2 · Building the Moon Base fact sheet, p. 1 · Ignition deck 2, slides 26, 30, 41–42, 53–54 · Ignition deck 5, slides 2, 12, 14 · 2026 industry and academia workshop, slides 12, 18 · SR-1 Freedom page