Skip to content

ESDMD #1107: Cryogenic Fluid Transfer

Low-loss transfer of cryogenic fluids, mainly propellants, between spacecraft and tanks in cislunar space, deep space and on surfaces (bin 1, rating 4 of 57). In-space cryogenic transfer "has not been demonstrated at scale", and boil-off forces a 15–20% propellant mass margin today. It spans all three segments, Moon and Mars (Tech gaps spreadsheet, ESDMD #1107).

Quotations below are from row ESDMD #1107 of the tech gaps spreadsheet. ADD Rev C's Appendix D prints the same table for this gap, and it matches the row except for one function ID under Traceability (ADD Rev C, p. 258; see below).

Description

"There is a need to transfer cryogenic fluids in cislunar space, deep-space and surface applications with minimal leakage. This capability would enable and enhance transportation vehicle performance involving cryogenic propellants, as it would reduce the amount of propellant that must be budgeted for leak margin."

Impacts and benefits: "Closing this gap enables regular transfer of cryogenic fluids across tanks and other interfaces with minimal propellant losses and transfer inefficiencies (such as residual propellant, which is not transferable), and reduces risks associated with fluid leakage."

Current state of the art

"Boil-off rate in current storage solutions necessitates additional propellant mass margin of 15%-20%. In-space transfer of cryogenic fluids has not been demonstrated at scale. Fluid transfer and capillary flow experiments have been conducted aboard ISS."

Performance target

  • Moon/Mars: "System that can enable low-loss cryogenic fluid transfer between spacecraft in microgravity and partial gravity environments."
  • Mars: "In addition, increased autonomy and reliability compared to the lunar performance target."

Child gaps

  • 1107-01: Dust-tolerant hardware components for low-loss cryogenic fluid transfer on the lunar and Martian surface
  • 1107-02: Thermal management to maintain low boil-off rates during transfer
  • 1107-03: Fluid management to enable efficient transfer of cryogenic fluid
  • 1107-04*: Hardware components for repeated reuse for low-loss cryogenic fluid transfer in space

1107-04 (starred) also appears under #1104. The asterisk marks "a child gap with multiple parents" (ADD Rev C, p. 199).

Traceability

  • Use cases and functions: UC-U-501 L -- FN-U-507 L; UC-U-502 L -- FN-U-508 L; UC-U-728 L -- FN-U-502 L; UC-I-102 L -- FN-I-107 L; UC-T-108 M -- FN-T-210 M; UC-U-501 M -- FN-U-502 M; UC-I-102 M -- FN-I-105 M
  • Definition tasks: Mars: Crew In-Space Return Propellant Strategy; Crew Mars Ascent Propellant Strategy

The two sources differ on one pair. The list above is the spreadsheet's. ADD Rev C's table pairs UC-U-501 M with FN-U-501 M, where the sheet has FN-U-502 M (ADD Rev C, p. 258, PDF checked). The other six pairs are the same in both. ADD Appendix B titles the two functions: FN-U-501 M, "Recover propellant from assets on the Martian surface (demonstration)", and FN-U-502 M, "Transfer propellant into storage asset(s) and/or transportation asset(s) on the Martian surface (demonstration)" (p. 147, PDF checked). Both documents are from December 2025, so the newer-wins rule doesn't decide it, and the wiki doesn't pick one (open question 37).

The use case's own title: ADD Appendix B.2.3 lists UC-U-501 M as "Demonstration of recovery of excess propellant from tanks of previous asset(s) on the Martian surface" (p. 133, PDF checked). This is recorded because open question 37 asked for it. It doesn't settle which function the gap's authors meant.

In the Mars decomposition: its "Functions to Use Cases" sheet puts FN-U-501 M to FN-U-504 M all under UC-U-501 M, so both pairings are ones the decomposition makes. It still doesn't say which one this gap means. The other two Mars pairs, UC-T-108 M – FN-T-210 M and UC-I-102 M – FN-I-105 M, are in the sheet too (Mars decomposition, "Functions to Use Cases").

Titles for the IDs above are on Lunar use cases and Lunar functions (ADD Appendix B.2, pp. 110–127), and on Mars use cases and Mars functions (pp. 127–147). For example, UC-U-728 L is "demonstration of recovery of excess propellant from surface asset(s)", FN-U-502 L is "Transfer propellant between assets on the lunar surface", and UC-T-108 M is "Operation of robust Martian transportation systems".

Segments and sub-architectures

Priority

Priority bin 1, overall prioritization rating 4 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

Not established by the sources so far. The Users Guide does not name #1107 among its near-term Moon Base challenges (Technology and knowledge challenges).

Sources

Tech gaps spreadsheet, ESDMD #1107 · ADD Rev C, pp. 78, 114–117, 127, 133, 147, 199, 258