Sustained Lunar Evolution (SLE)¶

Summary. The third segment: "Growing capabilities to enable economic opportunity, global access, and regular human presence" (ADD Rev C, p. 22). NASA calls it "an open canvas" and the "broad future state". It has no reference missions, no elements and no allocated functions yet: "there is insufficient depth to allocate functions beyond high-level capabilities" (p. 33). Instead the ADD sketches three notional paths: science capability, economic opportunity, and duration and population. 46 of the 57 technology gaps list this segment, more than any other; no data gap does.

All page numbers below are ADD Rev C unless marked otherwise. For what segments are, see Segments.

Description¶

"The Sustained Lunar Evolution segment is the broad future state that builds on the Human Lunar Return and Foundational Exploration segments and enables capabilities, systems, and operations to support regional and global utilization (science, etc.), expanded economic opportunity, and a steady cadence of human presence on and around the Moon" (p. 22).
"The focus of Sustained Lunar Evolution is growth beyond the Foundational Exploration segment to enable increased global science capability, long-duration/increased population, and large-scale production of goods and services derived from lunar resources" (p. 33).
"This segment is an open canvas for embracing new ideas, systems, and partners to grow a truly sustained lunar presence. The steps for achieving use cases for the Sustained Lunar Evolution segment will involve broad coordination between partners and exploration systems" (p. 33).
"At this time, there is insufficient depth to allocate functions beyond high-level capabilities associated with segment objectives. However, this section discusses notional examples of the future use case and the sub-architecture dependencies over time as a placeholder for future architecture development work" (p. 33).

Objectives¶

"This segment is driven by" (pp. 33–34):

RT-9, a recurring tenet: "foster the expansion of the economic sphere beyond Earth orbit to support U.S. industry and innovation" (see recurring tenets)
TH-3: "develop system(s) to allow crew to explore, operate, and live on the lunar surface and in lunar orbit with scalability to continuous presence conducting scientific and industrial utilization as well as Mars analog activities"
the Lunar Infrastructure goal: "create an interoperable global lunar utilization infrastructure where U.S. industry and international partners can maintain continuous robotic and human presence on the lunar surface for a robust lunar economy without NASA as the sole user, while accomplishing science objectives and testing for Mars" (Objectives)

A sustained surface architecture "would further enable key objectives in lunar/planetary science, heliophysics, human and biological science, and physics and physical science", and new science objectives "identified through discoveries made during other segments" (p. 34).

Three notional paths¶

"For Sustained Lunar Evolution, architecting from the right requires the development of economically plausible use cases and functions in coordination with NASA's partners" (p. 34). The ADD sketches how three "sustained states" could grow; "Notional evolutionary paths for these key areas could emerge as follows" (p. 34).

Path	Notional sequence	Notes
Increased science capability (p. 34)	More mobility and range at the South Pole → more sample return → "lunar global access for crew and cargo would enable scientific investigations anywhere on the Moon"	Needs delivery of instruments anywhere, sample conditioning and return, and astronauts who can "rapidly react to discoveries". FE already includes "the function to return science samples gathered during a 30-day–class mission". Communications must evolve "to allow concurrent science missions distributed across the lunar globe to send data via high-speed links", trading "satellite constellations, surface relay infrastructure, and technologies such as optical links".
Increased economic opportunity (pp. 34–35)	"minimal ISRU and regolith utilization" → "ISRU-derived propellants could reduce transportation costs" → "lunar ISRU and mining could reach industrial scale"	"governments are no longer the sole source of funding for lunar activities". Larger-scale opportunity emerges as "small-scale ISRU propellant production grows to industrial scale, aggregate power grows from kilowatts to megawatts, and the use of in-situ material and manufacturing becomes more economical than delivering everything from Earth". Later, "exporting propellant and material beyond the lunar surface". Needs "additional investments in communications, navigation, ISRU, power, and transportation sub-architectures".
Increased duration and population (p. 35)	Durations and crew numbers grow "until the segment sustains one or more permanent lunar outposts and a continuous human lunar presence" (p. 34)	Missions "will rely on local resources to provide water, support food growth, and build out infrastructure". An interim step: "small, modular systems to act as a bridge between initial Foundational Exploration capabilities and large-scale ISRU systems". "A year-round population will require power augmentation (e.g., nuclear fission power) to account for variations in sunlight over the course of the lunar year." "At some point in this evolution, the possibility of lunar tourism appears."

Reference missions and elements¶

Reference missions: "Future work for this segment will include defining additional reference missions and detailed concepts of operations" (p. 35).
Elements: none mapped. "Although the sub-architectures will evolve during the Sustained Lunar Evolution segment, further decomposition will introduce use cases and functions that inform development of future systems and elements for the segment" (p. 35). "Functional mapping for the Sustained Lunar Evolution and Humans to Mars segments is forward work" (p. 45).

Areas of future work¶

"The functional mapping for this segment remains forward work" (p. 35). The areas, as printed (p. 36):

"Identifying a future state and expanding demand signals to maximize objective satisfaction and empower government, industry, international, and academic partners to explore the Moon"
"Supporting the development of policy and standards to enable many actors to explore the Moon together"
"Expanding demand signals for advanced technologies and services, including logistics, mobility, robotic servicing, ISRU, habitation, assembly and construction, science systems, and communications, data, and navigation"

Gaps that list this segment¶

Derived from the spreadsheets' segment columns.

Technology gaps: 46 of 57, every gap except the 11 that list only Humans to Mars (tech gaps spreadsheet, Segments column; gaps index). The 32 Foundational Exploration gaps all list SLE too (FE page). The 14 that list SLE but not FE:
- SLE and Humans to Mars (13): #0304, #0306, #0308, #0401, #0402, #0403, #0404, #0405, #0406, #0502, #0503, #1001, #1004. Six of them are the crew health gaps #0401–#0406, all in Human Systems.
- SLE only: #0605 Lunar Regolith Excavation, Manipulation, and Transportation, the one gap whose only segment is SLE, though it is named in the Moon Base Users Guide (near-term) (see the gap page)
Data gaps: none (data gaps spreadsheet, Segment column; data gaps index). The ADD's own description says "The data gaps span all architecture segments" (p. 81), which the Segment column doesn't bear out, and nor do the ADD's own 25 data-gap tables in Appendix E (pp. 265–289) (open question 21).

In the recurring tenet assessments¶

Two of the ADD's tenet assessments (Section 3.5) name this segment as where open questions land:

Commerce. "the undefined Sustained Lunar Evolution segment specifically points to opportunities for increasing the economic sphere". Some vertical or horizontal integration by commercial entities across sub-architectures "is particularly relevant to the Foundational Exploration segment and even more critical for visions of the Sustained Lunar Evolution segment" (pp. 102–103; RT-9).
Maintenance. A topic for further study is "Whether and how to apply a modular open systems approach to enable a long-term autonomous repair capability supporting the Sustained Lunar Evolution segment" (p. 94; RT-5).

Moon Base relevance¶

Not established by the sources so far. No source maps this segment to a Moon Base phase, and the wiki does not assume one.

Segments · Foundational Exploration · Humans to Mars · Sub-architectures · ISRU Systems · Power Systems · Objectives: the ten goals · Gaps index

Sources¶

ADD Rev C, pp. 22, 33–36, 45, 81, 94, 102–103 · Tech gaps spreadsheet · Data gaps spreadsheet