Sub-architectures

Summary. ADD Rev C divides the Moon to Mars Architecture into 12 sub-architectures, each with a one-letter "Decomposition Abbreviation" from A to X (ADD Rev C, p. 40). The letter is the one in function and use-case IDs such as FN-P-101 L (Power Systems). The technology-gap spreadsheet uses the same 12, with small spelling differences ("Autonomous Systems & Robotics", "In-Situ"). The Moon Base Users Guide groups its Phase 1 functional gaps "by associated sub-architecture", under seven of the 12.

NASA's formal definition of a sub-architecture is on Architecture framework.

Why NASA uses them

"Sub-architectures capture the complex relationships between programs, projects, systems, and operations that must interact in a tightly coupled manner. Dividing the architecture into sub-architectures allows NASA to assess functions and use cases for consistency, gaps, and improvements. It also helps to identify areas for common standards and interoperability" (ADD Rev C, p. 40).

The 12

Name and letter from the table on p. 40, checked against the PDF. Elements are from the segment tables (pp. 26, 31–32). Tech-gap counts are derived from the spreadsheet's Sub-Architectures column, with the number named in the Moon Base Users Guide (near-term) in brackets (tech gaps spreadsheet; gaps index). The last column is the Users Guide's Phase 1 functional-gap group (Users Guide, pp. 8–10).

Letter	Sub-architecture	Elements	Tech gaps [MB]	Moon Base Phase 1 group
A	Autonomous Systems and Robotics	none	13 [6]	"Autonomous systems and robotics", 7 functions
C	Communications and Positioning, Navigation, and Timing Systems	1	4 [2]	"Communications and PNT", 4 functions
D	Data Systems and Management	none	5 [1]	none
H	Habitation Systems	2	11 [3]	"Habitation systems", 5 functions
X	Human Systems	none	11 [0]	none
G	Infrastructure Support	1	7 [2]	none
I	In-situ Resource Utilization Systems	none	7 [5]	none
L	Logistics Systems	1	7 [4]	"Logistics systems", 4 functions
M	Mobility Systems	4	11 [7]	"Mobility systems", 4 functions
P	Power Systems	1	5 [3]	"Power systems", 5 functions
T	Transportation Systems	6	7 [1]	"Transportation systems (cargo)", 2 functions
U	Utilization Systems	none	2 [0]	none

A gap can list several sub-architectures, so the gap column adds up to 90, not 57. Autonomous Systems and Robotics is listed most often (13 gaps) but has no element. ISRU has five of its seven gaps named in the Moon Base Users Guide (near-term), and also no element.

The letter in function and use-case IDs

The p. 40 table heads its letter column "Decomposition Abbreviation", and the ADD says "the summary tables below provide a brief overview of the sub-architectures, including the abbreviations used in the objective decomposition" (p. 40). The function and use-case IDs in the sources carry these letters in second place: FN-A-104 L, FN-C-201 L, FN-H-101 L, FN-X-103 L, FN-L-201 L, FN-M-302 L, FN-P-101 L, FN-T-201 L, FN-U-103 L (Phase 1 functional gaps), and FN-T-103 L and UC-T-103 L in the revision history (p. 4). Reading the second letter as the sub-architecture is the wiki's reading of p. 40. The ADD doesn't spell out the ID format in pp. 1–46, and Appendix B (pp. 109–135) doesn't either.

In Appendix B's lists:

• All 12 letters are used. Appendix B's lunar lists use every one of the 12 letters, and no other: 163 use cases and 208 functions (pp. 110–127). The lists run in the order T, G, H, X, L, P, M, C, D, A, I, U, not the p. 40 order.
• The trailing L and M. They mark the lunar and the Mars list: every ID in the "Lunar Use Case" and "Lunar Function" tables ends in L, and every ID in the "Mars Use Case" table ends in M. B.1 says the two "follow independent numbering schema" (p. 109).

Confirmed by a source: the key sheet of the lunar objective decomposition spreadsheet lists the 12 letters with a sub-architecture name each, numbered 1 to 12 in the B.2 order ("1 Transportation T" to "12 Utilization U"). It also names groups by hundreds within each letter, such as P 100 "Generation" and P 200 "Storage". So the letter is the sub-architecture on the source's own word, not only the wiki's reading of p. 40. The key's names are shorter than the p. 40 ones ("ISRU", "Logistics"; "Communications, Navigation, Positioning, and Timing") (source page).

Counts per letter are on Use cases and functions, Lunar use cases and Lunar functions (open question 8).

The Moon Base Users Guide's groups

The Users Guide summarizes "sets of functional gaps that NASA and its partners must close to enable the first phase of Moon Base development by associated sub-architecture" (Users Guide, p. 9). Its seven groups are seven of the ADD's 12, with shortened names; "(cargo)" is the guide's addition to Transportation. The five without a group are Data Systems and Management, Human Systems, Infrastructure Support, ISRU and Utilization.

The guide files six functions under a group whose letter differs from the function's own (read off Phase 1 functional gaps; the guide doesn't comment on it):

Function	Letter in the ID	Users Guide group
FN-M-401 L, unload cargo	M (Mobility)	Autonomous systems and robotics
FN-M-501 L, reposition cargo	M (Mobility)	Autonomous systems and robotics
FN-X-103 L, crew countermeasures	X (Human Systems)	Habitation systems
FN-L-301 L, manage waste	L (Logistics)	Habitation systems
FN-A-103 L, robotic reconnaissance	A (Autonomy and Robotics)	Mobility systems
FN-U-103 L, resource identification	U (Utilization)	Mobility systems

So the guide's groups follow the sub-architectures loosely, not by ID letter.

Across the segments

The ADD names sub-architectures when it describes how segments grow. Foundational Exploration's lunar infrastructure objectives drive "Expansion of the power (LI-1), C&PNT and data systems and management (LI-2, LI-3), transportation (LI-5, LI-6), mobility (LI-6), ISRU (LI-7), and utilization (LI-9) sub-architectures alongside surface infrastructure development to support industry (LI-4, LI-8)" (p. 28). Sustained Lunar Evolution "will require additional investments in communications, navigation, ISRU, power, and transportation sub-architectures" (p. 35). For Mars, "Mars elements fall into the similar sub-architectures as existing lunar exploration elements" (p. 38). See Segments.

History

The revision history says Rev A (Jan 2024) "Refined and added sub-architectures (Data Systems and Management, Infrastructure, In-situ Resource Utilization, Robotics)" (p. 3). Rev C's names for those are "Data Systems and Management", "Infrastructure Support", "In-situ Resource Utilization Systems" and "Autonomous Systems and Robotics" (p. 40).

The 2023 executive overview gives the full names: "The first eight of the sub-architectures listed below were included in the first edition of the Architecture Definition Document, with the last four added as part of the 2023 Architecture Concept Review process" (PDF p. 7). Its brackets marked "New for 2023" hold Data Systems and Management, Infrastructure Support, "In-situ Resource Utilization (ISRU) Systems" and Autonomous Systems and Robotics (read from the PDF). So the first edition (April 2023) had eight: C&PNT, Habitation, Human, Logistics, Mobility, Power, Transportation and Utilization Systems. The overview calls the first "Communications, Navigation, Positioning, and Timing Systems". Both overviews give each sub-architecture a one-line description in the same words (2023, PDF p. 7; 2024, PDF p. 23), for example Logistics Systems: "Package, handle, transport, stage, store, track, and transfer items and cargo." Rev C doesn't use these lines (search of its text for several of them).

Related pages

Architecture framework · Segments · Elements · Gaps index · Phase 1 functional gaps · Objective decomposition · Use cases and functions

Sources

ADD Rev C, pp. 3–4, 26, 28, 31–32, 35, 38, 40, 109–134 · Tech gaps spreadsheet, Sub-Architectures column · Users Guide, pp. 8–10 · 2023 executive overview, PDF p. 7 · 2024 executive overview, PDF p. 23