In-situ Resource Utilization (ISRU) Systems (I)

Summary. Systems that "generate products or consumables from local resources", starting with finding and mapping the resources (ADD Rev C, p. 43). Products include water, oxygen, metals, food, construction feedstock and propellant. ISRU has no element in Rev C, but it is central to the Sustained Lunar Evolution segment's economic path. Seven technology gaps list it; five are named in the Moon Base Users Guide (near-term), the highest share of any sub-architecture, though four of those are rated 53–56 of 57. Decomposition letter: I.

NASA's description

"This sub-architecture comprises systems designed to generate products or consumables from local resources on exploration missions. ISRU involves locating, mapping, and estimating extraterrestrial resource reserves and then extracting and processing them to generate products instead.

The practice of ISRU reduces mission dependance on delivering products and consumables from Earth. As humans stay longer and go farther into space, ISRU practices empower Earth independence and more sustainable commercial operations.

ISRU starts with resource identification, characterization, and mapping. This can include natural resources (e.g., regolith, water, atmosphere, etc.) and mission waste (e.g., crew trash, discarded hardware, etc.) ISRU production opportunities that can reduce mission cost or enable new operations include water, oxygen, and metals; human consumables and food production; feedstock for construction, manufacturing, and energy; and commodities for transportation vehicles, mobility systems, and propellant depots." (ADD Rev C, p. 43; spelling as printed)

In the segments

From ADD Rev C:

• Foundational Exploration. Objectives include "characterizing in-situ resources (OP-3)" and expansion of the "ISRU (LI-7)" sub-architecture (p. 28). The unpressurized mobility mission supports "the locating and retrieval of samples and resources" (p. 29). An area of future work: "Assessing the role of ISRU in lunar exploration" (p. 32).
• Sustained Lunar Evolution. The economic path runs from "minimal ISRU and regolith utilization, testing ISRU systems and concepts of operations"; then "the use of ISRU-derived propellants could reduce transportation costs"; eventually "lunar ISRU and mining could reach industrial scale" (p. 34). Larger opportunity comes as "small-scale ISRU propellant production grows to industrial scale" and in-situ manufacturing "becomes more economical than delivering everything from Earth"; later, "exporting propellant and material beyond the lunar surface" (p. 35). A larger population "will rely on local resources to provide water, support food growth, and build out infrastructure", with "small, modular systems" as a bridge to "large-scale ISRU systems" (p. 35). See Sustained Lunar Evolution.
• Humans to Mars. "demonstrating ISRU capabilities (MI-4)" (p. 38). A 2024 white paper weighs ISRU for Mars ascent propellant (below).

Elements

None in Rev C (segment tables, pp. 26, 31–32; see the elements index).

No ISRU function is performed by any element. Appendix B.3 maps none of the 15 lunar FN-I functions to an element. B.5 lists all 15 as unallocated in Foundational Exploration, under eight of the ten ISRU demonstration use cases, UC-I-101 L to UC-I-204 L (pp. 170–173). The other two, UC-I-104 L and UC-I-105 L (water and gas transfer), list only FN-L-203 L and FN-L-205 L. The 15 cover:

• oxygen and water production, storage and transport
• regolith collection and storage
• metals and feedstock processing
• autonomous construction
• advanced and additive manufacturing

Resource identification, FN-U-103 L, sits under four of the eight. The lunar spreadsheet marks all 15 "Unallocated" too (Lunar function allocation).

Technology gaps

Seven gaps list this sub-architecture (derived from the tech gaps spreadsheet, Sub-Architectures column, where it is "In-Situ Resource Utilization Systems"). MB = named in the Moon Base Users Guide (near-term).

Gap	Rating	MB
#0505 In-Situ Additive/Subtractive Construction	29	MB
#0606 Mars ISRU	52
#0605 Lunar Regolith Excavation, Manipulation, and Transportation	53	MB
#0601 Oxygen Extraction from Lunar Regolith	54	MB
#0603 Water Recovery from Lunar Regolith/Ice	55	MB
#0604 Metal Extraction from Lunar Regolith	56	MB
#0502 In-situ Manufacturing of Spares, Repairs, and New Parts	57

Rating 1 is the highest priority (ADD Rev C, p. 199), so these gaps sit at the low end of NASA's order: six of the seven are rated 52–57, in bin 6 (tech gaps spreadsheet). The ADD adds that "all gaps, even those in the lowest priority bin, are highly architecture driven" (p. 78). How the order is set is on the gaps index.

Mars ascent propellant (ACR24 white paper, 2024)

From the 2024 paper "Mars Ascent Propellant Considerations" (source page). It is 2024 context, older than Rev C, and about Mars only. Page numbers in this section are the paper's.

• Why ISRU for ascent. "For most proposed human Mars architectures, the single largest category of mass that must be delivered to the Mars surface is the propellant required for the crew's ascent to Mars orbit upon completion of their surface mission. Production of ascent propellants from in-situ resources would significantly reduce the propellant mass that must be delivered. This is possibly the single most significant application for in-situ resource utilization (ISRU)" (p. 1). The paper quotes objective MI-4, "…Mars ISRU capabilities to support an initial human Mars exploration campaign" (Objectives).
• What Mars offers. "The Martian atmosphere, surface materials (i.e., regolith), and water in the form of buried ice sheets, ice mixed with near-surface regolith, or minerals containing chemically bound water." Besides propellant: breathing gases, water "for crew consumption, radiation protection, and crop growth", and "building materials for landing/launch site berms, radiation protection, and habitat construction" (p. 1).

• Three NASA studies (p. 2; headings as printed, PDF checked):

  Study	Mission studied	Ascent propellant options	What it found
  2009, "Mars Reference Mission Architecture"	"a campaign of three missions, with six crew each, to three different locations"	four: no ISRU; two that combine "the Martian atmosphere and Earth-origin resources"; one using "Martian atmosphere and water extracted from regolith"	"using Martian oxygen for ascent offered the best balance between mass savings, total volume required, and power generation needs", and ISRU "generally lowered the overall mass … while improving overall mission flexibility". It "predated the 2018 Mars global dust storms and their effects on power systems".
  2021, "Human Mars Architecture Study"	"a basic mission that does not manufacture propellant from Martian resources", but moves propellant across the surface and loads it into an ascent vehicle	Earth-origin only	"architectures without ISRU are feasible, but have their own associated challenges", and they "could demonstrate capabilities that reduce associated risks"
  2024, "Strategic Analysis Cycle"	"a single mission of four crew, two of whom would descend to the Martian surface"	three, all with "pre-deployed infrastructure": water from Earth, water from buried ice sheets, water from regolith	the ISRU options "offer significant mass savings and flexibility for mission planning" but "require significant energy, time commitments, and unique assets"

• The trade space (p. 2), in three bands:

  • No ISRU. "A non-ISRU architecture will land fuel needed for ascent before the arrival of the crew for safety reasons, as the crew should not arrive on the Martian surface until their means to return are in place." It still shares "pre-placement of equipment, supplies, and power systems" with ISRU and, if the ascent vehicle isn't landed fully fueled, "autonomous fueling operations".
  • Limited ISRU. Some feedstock from Earth: "the Martian atmosphere and Earth-origin methane or the Martian atmosphere and Earth-origin hydrogen". The 2024 study's water-from-Earth case makes the propellant on Mars "using many of the same processes and technologies as ISRU-intensive architectures".
  • Comprehensive ISRU. Everything from Mars: the atmosphere plus water from regolith or buried ice. These "maximize the use of Martian resources, but also require the most support equipment", and a "significant time commitment".
• Three driving factors (p. 3):
  • Mass. "ISRU does not always represent a total mass cost savings from a mission architecture perspective." Developing and transporting the systems "can exceed the cost of sending propellant (especially if those systems cannot be used across multiple missions)". Any mission "that does not land a fully fueled ascent vehicle" needs mass "for autonomous transportation and loading of propellant".
  • Site selection. ISRU "naturally constrains site selection". Re-using infrastructure at one site saves cost but "would reduce the diversity of regions available for study". "A mission that intends to primarily explore a single site might benefit from ISRU infrastructure, while a mission that explores multiple sites might benefit from landing of propellant."
  • Production rate. The most ISRU-intensive architectures "could require NASA to emplace and operate infrastructure years before a crewed mission". Launch windows come "roughly 26 months" apart.
• No decision. "NASA must thoroughly consider the ascent propellant trade space before selecting an approach" (p. 4). Figure 2 shows "a notional regolith-based ISRU surface infrastructure" from the 2024 study, with fission power, mining areas, rovers and a "Mars Ascent & Landing Vehicle" (p. 4). These are concept labels, not ADD elements; the key is transcribed on the source page.

What changed by Rev C

The wiki's comparison; the paper predates Rev C.

• Still open. "Crew Mars Ascent Propellant Strategy" is an open key definition task in ADD Appendix C's table (category 10, pp. 194–197), and both #0606 and #1105 list it (Key definition tasks). Rev C's areas of future work for Humans to Mars include "return propellant strategies" (ADD p. 39). The paper doesn't name the task; the pairing is the wiki's.
• Still no Mars ISRU strategy. Gap #0606 says "Mars in-situ resource utilization (ISRU) strategies have yet to be defined, several decision options and reference missions rely on ISRU-derived materials and/or propellants" (ADD p. 233). It is rated 52 of 57.
• The 2024 study's scenario is outside two 2025 decisions. It was a single mission with two crew descending. MD-02 (2025) "removed all single-mission scenarios", and MD-05 set a floor of four crew to the surface (ADD pp. 76, 193; Key definition tasks).
• The site trade and MD-02. MD-02's three remaining options are multiple missions "that return to the same site" (two of them) or "to different sites" (one) (ADD p. 193). The paper links one site to ISRU and several sites to landed propellant. No source sets the two side by side; the link is the wiki's.
• Power. The 2024 power decision names "ascent propellant manufacturing" among the needs for which "fission surface power is readily scalable" (Key definition tasks).

Moon Base Phase 1

The Users Guide has no ISRU group among its Phase 1 functional gaps (Users Guide, pp. 8–10), though its power group lists "In-situ resource utilization (ISRU) processing" as a use of power (p. 10). Five of this sub-architecture's gaps are named in the Moon Base Users Guide (near-term), under two associated challenges (Technology and knowledge challenges):

• "ISRU systems": #0601, #0603, #0604, #0605, with data gaps DN-006 L and DN-007 L
• "Manipulating regolith": #0505, #0605

Related pages

Sub-architectures · Infrastructure Support · Power Systems · Sustained Lunar Evolution · Humans to Mars · Gaps index · Data gaps index

Sources

ADD Rev C, pp. 26, 28–29, 31–32, 34–35, 38–40, 43, 76, 78, 170–173, 193–197, 199, 233 · Tech gaps spreadsheet · Mars Ascent Propellant Considerations (2024), pp. 1–4 · Mars Surface Power Technology Decision (2024), p. 3 · Lunar objective decomposition, allocation sheets · Users Guide, pp. 8–13