February 2025 workshop: Mars surface power white-paper briefing (industry and academia deck)

Document: 2025-ia-workshop-wp-mars-surface-power.pdf, 13 slides, 1,563,791 bytes, from https://www.nasa.gov/wp-content/uploads/2025/02/, fetched 2026-10-01T18:28:06Z (sources/manifest.csv). Title slide: "Mars Surface Power", "February 2025", Michael Chappell, Deputy Mars Architecture Lead, Strategy and Architecture Office. Text: sources/text/docs/2025-02-2025-ia-workshop-wp-mars-surface-power.txt; images in sources/raw/slides/2025-02-2025-ia-workshop-wp-mars-surface-power/. Read from the images: slides 4, 9 and 11 (the highlighting, the charts and the scoring symbols). The text-poor slides 1 and 13 (title; "Summary of Decision") were not viewed; their text gives the title, presenter, decision and link. No "Moon Base", "CUI" or "Pre-Decisional" in the text (searched).

What it is. A briefing of the 2024 white paper Mars Surface Power Technology Decision, the decision Rev C lists as MD-07 (Key definition tasks), at the industry and academia workshop of February 2025, before Rev C. The partners' workshop had the same slides (international copy). The decision is the paper's: "Nuclear fission power selected as primary surface power generation technology for initial crewed missions to Mars" (slides 2, 13). The slides add the decision's working: the attributes and which five counted most, who scored them, the mass figures behind "mass advantages", the dust and dust-storm figures, a scoring against measures of effectiveness, and affordability points the paper doesn't make. A summary sits on Key definition tasks.

Slides

Slide	Title, as printed	What it holds
1	Mars Surface Power	Title and presenter
2	Introduction	The decision; "2024 Architecture Concept Review outcome"; "Exercise in process as much as decision outcome"; "Documented in Appendix B of the Architecture Definition Document"
3	Background	Why the decision was taken, and how
4	Decision Attributes	The process and ten attributes, five highlighted
5	Technology Trade Space and Down Select	Two nuclear and six non-nuclear options, with reasons for dropping five
6	Reliability/Availability: Robustness to Reduced Solar Flux on Mars	Solar flux; three reference missions' power needs and solar against fission mass
7	Reliability/Availability: Robustness to Nominal Mars Dust	Dust on InSight's arrays; "~ 0.2 % per sol"
8	Reliability/Availability: Robustness to Dust Storms	The 2018 storm
9	Scalability	Two mass charts
10	Affordability Drivers	Four areas
11	Architecture Measure of Effectiveness	Fission and photovoltaics scored against eight measures
12	Conclusion: Fission Trades More Favorably	Attribute by attribute
13	Summary of Decision	The decision and a link to the paper

What the slides add to the paper

Background (slide 3): "Decision identified due to impacts on the architecture"; "Assessment process involved numerous stakeholders, technical experts, and technical authorities"; "Primarily driven to mitigate loss of mission risks"; "Lays the groundwork for future architecture implementation decisions".

The attributes (slide 4). A five-step process: "Brainstorming and draft attributes", "Stakeholder review and consensus", "Data mapping to attributes", "Stakeholder Scoring", "Scoring rationale review and discussion". Note: "Attributes were developed, reviewed, and scored by STMD, SAO, M2MPO, OSMA". The paper names "stakeholders from across NASA's mission directorates and technical authorities" but not these four (p. 4). The ten attributes, under the paper's four headings; the five in bold are highlighted on the slide, under the banner "Consensus that 5 highlighted attributes are most impactful":

• Reliability / Availability: Robustness to Near Surface Temperature Variations; Robustness to Surface Solar Flux Variations; Robustness to Nominal Dust; Robustness to Dust Storms; Maintainability/Repairability
• Power Needs: Minimum Power Needs for Initial Segment; Scalability; Operational Lifespan
• Extensibility to Future Segments
• Affordability Drivers

The options (slide 5). Nuclear: "Fission surface power systems (FSP)" and "Radioisotope thermoelectric generators (RTGs)". Non-nuclear: "Photovoltaic array with energy storage", "Primary batteries", "Primary fuel cells", "Wind power generation", "Geothermal power generation", "Biogeneration concepts". Reasons printed for dropping five: RTG, "Scalability issues", "Pu-238 production limit & low TRL alt. fuels"; primary batteries, "Poor scalability", "Not practical (mass) even for 2 crew/30 sol/no ISRU"; primary fuel cells, "Energy to make reactants exceeds energy generated", "Needs reactant delivery"; wind, "Insufficient sustained winds for reliable power production"; geothermal, "Energy-intensive infrastructure build needed to implement"; biogeneration, "Complicated by planetary protection constraints". The paper doesn't name Pu-238, and mentions batteries only as storage for solar arrays (search of its text); its geothermal reason is "limited data" (p. 3).

Solar flux and mass (slide 6): "Mars is 1.5x farther from the Sun than Earth, so ~57% less solar energy reaches Mars' atmosphere"; "no solar power is generated about half of each Martian day"; "Fission power output is not affected by solar flux". A table of three earlier reference missions, as printed:

Reference mission	Cargo need	Crew need	Solar	Fission
2009 DRA 5	26 kW ISRU	~35 kW (Hab, Lab, rover MAV)	22.5 t	6 to 8 t (40 kW)
2016 EMC	26 kW ISRU	31 kW (Hab, Lab, Rover, MAV)	11.7 t (N. hem.)	9 t (5 x 10 kWe)
2020 POD	9 kW No ISRU	9 kW (MAV, rover, prop transfer)	11.22 t	7.93 t (10 kW + spare)

"EMC" and "POD" are not expanded. DRA 5.0 is one of the historical studies on NASA's Mars Architecture Studies page. The paper's "about 45 percent of typical Earth values" (p. 2) and the slide's "~57% less" are two ways of putting the flux; the paper prints no masses.

Dust (slides 7–8): "Data from multiple Mars assets shows solar power degradation of ~ 0.2 % per sol without active dust mitigation", over a picture of "Steady accumulation of dust on the InSight solar arrays". "Power studies prior to 2018 underestimated solar power mass based on storms less than half as severe (τ = 5) as 2018 storm (τ = 10.8)"; "Solar power mass increases with storm severity/duration"; "fission power mass is stable regardless of storm severity or duration". (The primary's text layer drops the τ; the copy's prints "t".)

Scalability (slide 9, read from the image). Fission: "Lower, linear mass with increasing power" (ticked). Solar with storage: "Trends higher mass above 10 kW, dependent on ops, latitude, and dust storm assumptions" (crossed). Two charts: system mass against power to 100 kWe for "Fission vs. Sun-tracking PV arrays with RFC energy storage -- Assumes 450 W/m2 (Nominal, Equator), 100 W/m2 (Dust Storm), 12 Hour Night", with bands for "PV/RFC Dust Storm" and "PV/RFC Nominal, Equator" (each at 50% and 100% night power) above an "FSP" band; and "Comparisons of Recent Surface Power Point Design System Mass", nuclear, solar and "updted dust storm solar" points against user power to 150 kW with a linear nuclear trend. The wiki reads no values off them.

Affordability (slide 10): "Development & Construction" ("Heritage development", "Facilities Availability"); "Policy and Certification" ("Space Policy Directive 6 encourages High Assay Low Enriched Uranium (HALEU)", "Lowers safety/security overhead"; "NASA is leading a dozen federal agencies to identify/address space nuclear policy gaps"); "Payload Processing" ("Safety/Security", "Heritage Experience"); "Deployment and Autonomous Ops" ("Particularly robust to loss of mission"); and "Maintainability is a separate attribute, but note that nothing on fission power systems requires EVA maintenance". None of this is in the paper (search for "HALEU", "Directive" and "EVA maintenance").

Measures of effectiveness (slide 11, symbols read from the image). "Decision Attributes were defined specifically for the Mars Surface Power decision to represent the trade-offs of how well the decision options can potentially satisfy agency objectives." Note: "This is the first decision to be added to the Mars architecture. A baseline Mars MOE assessment does not yet exist." Four attributes (solar flux, dust storms, scalability, affordability drivers) are linked by arrows to eight measures. The scale runs from "Major Impact -2" to "Major Improvement 2":

Measure of Effectiveness (MOE)	Fission Power	Photovoltaic with Storage
Surface Location Access	Major Improvement (2)	Moderate Improvement (1)
Environmental Access	Moderate Improvement (1)	Neutral Impact (0)
Power	Major Improvement (2)	Moderate Improvement (1)
Crew Utilization	Moderate Improvement (1)	Moderate Improvement (1)
Uncrewed Utilization	Moderate Improvement (1)	Moderate Improvement (1)
Mass	Moderate Impact (-1)	Major Impact (-2)
Cost	Major Impact (-2)	Moderate Impact (-1)
Development Complexity	Moderate Impact (-1)	Moderate Impact (-1)

These eight measures are not the labels of the 2025 Architecture Update's performance radar chart, whose six labels each end in "Opportunity" (Architecture definition process; the wiki's comparison).

Conclusion (slide 12), fission against solar: dust storms, "Reliable power generation through severe storms" against "Limited/no reliable power generation during storms with tau >7 increases system mass energy storage"; scalability, "Mass advantage Increases with increasing power" against "Competitive mass at/below 10 kW" and "Mass disadvantage grows with power need"; solar flux, "Power not appreciably affected by season, latitude, or day/night" against "Mass/volume dependent on season/location; need energy storage mass for night-time operations"; affordability, "Higher development & unit cost" and "Potential lunar cost/risk buy down" against "Lower development & unit cost" and "Potential for lunar activity cost/risk buy down"; nominal dust, "Dust build-up on radiators may require active/passive mitigation" against "Dust build-up on arrays will require active mitigation" and "Dust suspended in the atmosphere will reduce power generation and increase stored energy mass needed". Cost is the one attribute where the slide marks fission down.

"Appendix B" (slide 2). The decision is "Documented in Appendix B of the Architecture Definition Document", Rev B's appendix for decisions in the February 2025 Architecture Updates deck (source page); Rev C lists the completed tasks in Appendix C.

Oddities

• "updted dust storm solar" (slide 9, chart legend), as printed.
• "Mass advantage Increases" (slide 12), as printed.
• "tau >7" on slide 12 against the 2018 storm's "10.8" and the earlier studies' "5" on slide 8; the slides don't say where 7 comes from.

Related pages

Mars Surface Power Technology Decision · Key definition tasks: MD-07 · #0902 Scalable Mars Surface Power Generation · Power Systems · Humans to Mars · International copy