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ESDMD #0301: Systems to Survive and Operate through Extended Periods of Lunar Shadow

Power, thermal and actuation technologies that let surface assets survive and work through long periods of lunar shadow (bin 1, rating 3 of 57). Small spacecraft have survived with damage, and no human-scale element has yet done it. The target is to "survive continuous shadow for 350 hours or more several times a year for 10 years". It is named in the Moon Base Users Guide (near-term), twice: long-duration operations and thermal generators (Tech gaps spreadsheet, ESDMD #0301; Users Guide, pp. 12–13).

Quotations below are from row ESDMD #0301 of the tech gaps spreadsheet unless marked otherwise. ADD Rev C's Appendix D prints the same table for this gap, and it matches the row field for field (ADD Rev C, p. 210).

Description

"Assets on the surface of the Moon will be subjected to large variations in natural and induced environments. The ability to survive and operate through these extreme variations is required to enable long-duration surface operations. New or improved power, thermal management, and actuation technologies are required and will need to work together to accomplish this goal for science experiments, mobility assets, habitats, and more."

Impacts and benefits: "Without gap closure, the inability to survive extended periods of lunar shadow will impact the operating lifespan of surface assets. There may also be an inability to reuse surface assets if systems cannot survive shadowed periods."

Current state of the art

"Small spacecraft have survived extended periods of lunar shadow with damage to subsystems and degraded capability. There is currently no state of the art for any human-scale elements successfully functioning through extended lunar shadow periods."

Performance target

Moon: "Survive continuous shadow for 350 hours or more several times a year for 10 years."

For comparison, the Users Guide's Phase 1 power capability target is to "Demonstrate 5 kW power generation and storage, as well as survival through 120+ hours of darkness" (Users Guide, p. 10; see Phase 1 functional gaps). The two figures have different scopes: the spreadsheet does not tie its target to a Moon Base phase, and the Users Guide does not relate its 120+ hours to this gap.

Child gaps

  • 0301-01: Freeze-tolerant thermal components
  • 0301-02: Extreme temperature-tolerant mechanisms and electronics
  • 0301-03: Energy storage for extreme temperatures
  • 0301-04: Heat rejection systems for the lunar thermal environment

Traceability

  • Use cases and functions: UC-H-105 L -- FN-H-201 L
  • Definition tasks: Moon: âś“LD-03-L Lunar Landing Region Selection. The âś“ is printed in the sheet; the ADD's gap tables say "“✓” indicates completed definition task" (ADD Rev C, p. 204). LD-03-L is a legacy decision: "The lunar South Pole region will be the initial landing area for crewed missions" (p. 75; Key definition tasks).
  • Cross-reference: FN-H-201 L, "Operate habitation systems(s) in uncrewed mode between crewed missions on the lunar surface", is also one of the Users Guide's Phase 1 functional gaps (Users Guide, p. 9; see Phase 1 functional gaps). This link joins the two sources; neither makes it.

Segments and sub-architectures

Priority

Priority bin 1, overall prioritization rating 3 of 57. The rating is "the gap's location in the prioritized list of gaps", so 1 is the highest priority, and bins group gaps of similar priority, bin 1 highest. Criticality, urgency, breadth and depth set the order; cost is not considered (ADD Rev C, pp. 78, 199; method on the gaps index).

Moon Base relevance

For the long-duration challenge, the guide lists #0101, #0201, #0301, #0801 and #0804 together against its three technology bullets, without assigning gaps to bullets. The bullet quoted below is the one closest to this gap's subject.

The Users Guide names #0301 in two places (Users Guide, pp. 12–13):

  • the headline challenge "Operating on the lunar surface for long durations", whose technology challenge includes "Develop extreme temperature-tolerant mechanisms and electronics for operating through periods of lunar shadow without dedicated heating systems";
  • the associated challenge "Thermal generators": "Using radioisotope thermal generators (RTGs) to provide survive the night capabilities requires detailed knowledge of the lunar environmental and systems that can operate there."

The guide ties its challenges to "near-term Moon Base development efforts": missions in phase one "offer opportunities to collect data and mature technologies to enable essential phase two and phase three capabilities" (p. 11). See Technology and knowledge challenges.

Same subject in the Ignition material (the pairing is the wiki's; neither source names a gap). The Building the Moon Base fact sheet lists for Phase 1 "Early power, navigation, communication, and nuclear RHU demonstrations to ensure systems can survive the lunar night" (Building the Moon Base fact sheet, p. 1; "RHU" is not expanded). The CLPS CS-8 task order offers a bonus for "deploying a radioisotope device and transmitting signals from the lunar surface after enduring a full lunar night" (Ignition page). The Moon Base Program's Ignition deck expands the term, "Radioisotope heater units (RHUs) provide heat, allowing for survive the night capability", and sets two figures beside this gap's: "Initial lander demonstrations will survive 120+ continuous hours of darkness and send a signal back to Earth", and RHUs will "Enable future lunar assets to survive 354+ hours of local darkness" (Ignition deck 2, slide 16). The deck's 120+ hours is the guide's Phase 1 target figure, and its 354+ hours is close to this gap's "350 hours or more"; the deck cites neither, and adds RHUs, which neither the gap nor the guide names. See Moon Base needs. The deck's power table phases them: "Demo initial hibernation points" and "Demo initial Radioisotope Heater Units (RHUs)" in Phase 1; "Radioisotope Thermal Generator (RTG) Power Stations", with assets that "begin routinely using RHUs & RTGs to enable night survival and additional night operational capability", in Phase 2; and LTVs "capable using RHU & RTG" of permanently shadowed region exploration in Phase 3 (Ignition deck 2, slides 54 and 57). The guide's Phase 1 target names RTGs; the deck puts them in Phase 2 (open question 83).

In the February 2025 workshop briefing

The technology-gaps briefing at both February 2025 workshops, older than Rev C, used this gap as its example of a gap table "in ADD Rev B, Appendix C" (read from the image). Against today's row (the wiki's comparison): the title, description, impacts and benefits, state of the art, four child gaps, use case–function pair, sub-architectures and segments are the same. Three fields differ. The target was "Survive continuous shadow for 150 (TBR) hours or more several times a year for 10 years", where Rev C has 350 hours and no "(TBR)". The "Key Decision" field was blank, where Rev C has ✓LD-03-L. The priority column was a shaded "Higher Priority" scale with no number; the same deck ranks the gap 2nd in Rev B, bin 1, where Rev C rates it 3rd (technology gaps briefing, slides 4–5). No source read says why the target changed. Moon Base relevance is unchanged: the briefing predates the Moon Base. See Rev B's list against Rev C.

Sources

Tech gaps spreadsheet, ESDMD #0301 · Lunar power white paper, p. 4 · ADD Rev C, pp. 75, 78, 199, 204, 210 · Users Guide, pp. 9, 10, 12–13