Segments¶
Summary. ADD Rev C divides the Moon to Mars Architecture into four segments, which it calls "broad phases of exploration": Human Lunar Return, Foundational Exploration, Sustained Lunar Evolution and Humans to Mars, plus a placeholder for "Future Segments" (ADD Rev C, pp. 21–23). They run in order of growing capability, but NASA develops them in parallel. Only the first two segments have elements assigned; for the other two, "functional mapping … is forward work" (p. 45). Segments are not Moon Base phases: no source maps one to the other.
NASA's formal definition of a segment is on Architecture framework.
How segments relate to each other¶
- "NASA structures the Moon to Mars Architecture to empower incremental buildup of capabilities in service to objective satisfaction. Segments delineate the continuum of evolving capabilities and growing objective satisfaction" (ADD Rev C, p. 22).
- "Although these segments appear in sequential order, they are not exclusively serialized. While they do build upon each other, NASA pursues parallel development of architecture segment capabilities. This is especially true where lessons learned at one destination inform concurrent architecture development at another destination (i.e., Mars-forward activities performed during lunar segments)" (p. 22).
- Future segments. "As the architecture accomplishes or adds objectives, NASA will define additional segments to enable continued exploration" (p. 23).
The segments at a glance¶
Taglines are NASA's, from the segment boxes on pp. 22–23. Codes are from the ADD acronym list (ADD Rev C, pp. 292–293). The other columns are read off each segment's section.
| Segment | Code | NASA's tagline | Reference missions | Elements mapped | Areas of future work |
|---|---|---|---|---|---|
| Human Lunar Return | HLR | "Initial capabilities necessary to re-establish human presence on and around the Moon." | 2 (p. 25) | 8, plus the Gateway Logistics Element (p. 26) | 2 (p. 26) |
| Foundational Exploration | FE | "Expansion of lunar capabilities supporting complex orbital, surface, and Mars precursor missions." | 7 (pp. 29–30) | 15, plus the Gateway Logistics Element (pp. 31–32) | 10 (p. 32) |
| Sustained Lunar Evolution | SLE | "Growing capabilities to enable economic opportunity, global access, and regular human presence." | none yet: "future work" (p. 35) | none yet (p. 35) | 3 (p. 36) |
| Humans to Mars | H2M | "Initial capabilities necessary to establish a human presence on Mars." | none yet: "future work" (p. 38) | none yet: "forward work" (p. 38) | 5 (p. 39) |
| Future Segments | — | "Additional segments added for continued exploration of the Moon, Mars, and beyond." | — | — | — |
The ADD's reference missions "demonstrate how architectural capabilities could be used; they are not specific missions NASA will conduct" (p. 25; repeated for Foundational Exploration on p. 28).
Elements by segment¶
From the element tables in each segment section (ADD Rev C, pp. 26, 31–32), checked against the PDF. The Section 2.3 table (pp. 45–46) marks the same segments with icons. Element names follow the Section 2.3 headings; see the elements index, which also records where the ADD's three element tables disagree.
| Element | Sub-architecture | HLR | FE |
|---|---|---|---|
| Commercial Lunar Payload Services | Transportation Systems | ✓ | ✓ |
| Exploration EVA System | Mobility Systems | ✓ | ✓ |
| Exploration Ground Systems | Infrastructure Support | ✓ | ✓ |
| Gateway ("Gateway Crew-Capable Configuration" in the segment tables) | Habitation Systems | ✓ | ✓ |
| Gateway Logistics Element (part of Gateway, Section 2.3.4.1.4) | Logistics Systems | ✓ | ✓ |
| Human Landing System | Transportation Systems | ✓ | ✓ |
| Human-Class Delivery Lander | Transportation Systems | ✓ | |
| Initial Surface Habitat | Habitation Systems | ✓ | |
| Lunar Nuclear Fission System ("Lunar Nuclear Power System" in the FE table) | Power Systems | ✓ | |
| Lunar Surface Cargo Lander | Transportation Systems | ✓ | |
| Lunar Terrain Vehicle | Mobility Systems | ✓ | |
| Lunar Utility Rover | Mobility Systems | ✓ | |
| Orion Spacecraft | Transportation Systems | ✓ | ✓ |
| Pressurized Rover | Mobility Systems | ✓ | |
| Space Communications and Navigation Networks | C&PNT Systems | ✓ | ✓ |
| Space Launch System | Transportation Systems | ✓ | ✓ |
Every Human Lunar Return element carries on into Foundational Exploration. The FE segment "will continue to use elements introduced in Human Lunar Return while adding new capabilities as they become available. Interoperability between elements will be especially important during the segment" (p. 30). No element is mapped to Sustained Lunar Evolution or Humans to Mars: "Functional mapping for the Sustained Lunar Evolution and Humans to Mars segments is forward work" (p. 45).
Gaps by segment¶
Counts derived here from the two spreadsheets' segment columns; neither sheet summarizes them. A gap can list more than one segment.
| Segment | Technology gaps (of 57) | Data gaps (of 25) |
|---|---|---|
| Human Lunar Return | 0 | 17 |
| Foundational Exploration | 32 | 2 (DN-006 L, DN-007 L) |
| Sustained Lunar Evolution | 46 | 0 |
| Humans to Mars | 44 | 6 (all Mars gaps) |
Sources: tech gaps spreadsheet, Segments column; data gaps spreadsheet, Segment column. The two sheets use the segment differently. For data gaps it is the segment "during which the data is needed, but not necessarily when it is collected" (data gaps spreadsheet, Key sheet). The tech-gap sheet doesn't define its column, but ADD Rev C's gap catalog does: "The Moon to Mars Architecture segment(s) for which the capability is needed. A gap's urgency score is partly based on the first segment for which the capability is needed" (ADD Rev C, p. 199). So a technology gap's segments say when the capability is needed, and the first of them bears on its urgency, one of the four priority metrics (gaps index). Per-gap detail is in the gaps index and the data gaps index.
The two zeros, as the ADD explains them or doesn't:
- No technology gap lists Human Lunar Return, by design. "The Human Lunar Return Segment contains technology development and investment by the current programs, so the technology gaps captured in this document do not trace to Human Lunar Return" (ADD Rev C, p. 79).
- No data gap lists Sustained Lunar Evolution, although the ADD says "The data gaps span all architecture segments" (p. 81). The ADD's sentence and the spreadsheet's Segment column disagree (open question 21).
Segments and the Moon Base¶
- No mapping. No source so far maps ADD segments onto the three Moon Base phases. The Moon Base Users Guide doesn't map them either: a search of its extracted text finds no "segment", and it ties ADD functions, tech gaps and data gaps to Phase 1 directly (Moon Base hub). The wiki does not map them either (SCHEMA, "Versions and dates").
- Changes since Rev C. Two later sources change plans the segment sections rely on:
- Artemis III. The ADD says Artemis III "lands crew on the lunar surface" (ADD Rev C, p. 24). The March 2026 fact sheet makes Artemis III an Earth-orbit test in 2027 and Artemis IV the landing, in early 2028 (Going back to the Moon, pp. 1–2). The newer source wins (open question 22).
- Gateway. Three of the nine lunar reference missions involve Gateway or crewed missions to its orbit, NRHO (pp. 25, 30), and Gateway is an element of both lunar segments. The Users Guide says the Power and Propulsion Element "originally planned for the Gateway space station" now goes to SR-1 Freedom (Users Guide, p. 2). None of the wiki's sources says what this means for the Gateway reference missions.
In the executive overviews (2023 and 2024)¶
The 2023 and 2024 executive overviews, both older than Rev C, each give the four segments a page (2023 overview, PDF p. 6; 2024 overview, PDF p. 22). Both open the same way: "The architecture segments below capture the evolutionary nature of NASA's Moon to Mars exploration strategy, growing in complexity over time to meet more of NASA's Moon to Mars Objectives." Most of their text is in Rev C's segment sections, lightly edited. The differences, by the wiki's comparison:
- Human Lunar Return. The 2023 overview says the segment will "land the first woman and first person of color on the lunar surface". The 2024 overview adds "and first international partner astronaut". Rev C has neither phrase (search of the text). Rev C's segment has Artemis III landing crew (p. 24), since superseded (above).
- Foundational Exploration. 2023 and 2024: activities "may include reconnaissance, Mars risk reduction, and initial infrastructure for long-term lunar evolution". Rev C: "initial infrastructure supporting long-term lunar access and utilization" (p. 27).
- Sustained Lunar Evolution. 2023: "Will aim to build future economic opportunity and greater participation in lunar science and exploration"; 2024: "Will stimulate future economic investment and foster participation". Both call it "an 'open canvas,' embracing new ideas, systems, and partners to realize a long-term human presence on the Moon and grow the lunar economy" ("human" added in 2024). Rev C: "an open canvas for embracing new ideas, systems, and partners to grow a truly sustained lunar presence" (p. 33).
- Humans to Mars. All three have "The Moon to Mars Architecture sets a course to finally step foot on a planet beyond humanity's own" (2023; Rev C p. 37), or "beyond our own" (2024). The 2024 overview adds that the longer missions will come "in future segments beyond Humans to Mars".
How the segments lead to Mars, in the 2024 overview's "Why Moon to Mars?": "After the initial Artemis missions of the Human Lunar Return segment, activities in the lunar Foundational Exploration segment will prove the technologies, capabilities, and systems needed for the Humans to Mars segment. The Sustained Lunar Evolution segment will see increased scientific and commercial utilization of the Moon while government-led development continues toward the next horizon" (PDF p. 5). On its segments page, "You are here." is written beside Human Lunar Return (PDF p. 22, read from the PDF).
The 2023 element additions. The 2023 overview puts six new elements in Human Lunar Return that Rev C maps to Foundational Exploration (Elements; open question 33).
Related pages¶
Architecture framework · Sub-architectures · Elements · Objective decomposition · Objectives: the ten goals · Gaps index · Data gaps index · Moon Base phases · NASA's Components web page (the 2024 overview's segment text, reworded; it says it is being updated for 2026)
Sources¶
ADD Rev C, pp. 21–39, 45, 79, 81, 199, 292–293 · Tech gaps spreadsheet · Data gaps spreadsheet · Going back to the Moon, pp. 1–2 · Users Guide, p. 2 · 2023 executive overview, PDF pp. 6, 10 · 2024 executive overview, PDF pp. 5, 22