Architecture Definition (ACR25 white paper)

Document: Architecture Definition, a six-page white paper headed "2025 Moon to Mars Architecture" and footed "2025 Moon to Mars Architecture Concept Review". No date is printed. The download path (/2025/12/) dates it to December 2025, and the file name ends in -v3. Files: text sources/text/docs/2025-12-acr25-wp-architecture-definition-v3.txt; raw sources/raw/docs/2025-12-acr25-wp-architecture-definition-v3.pdf (fetched 2026-10-01T07:22:47Z from https://www.nasa.gov/wp-content/uploads/2025/12/acr25-wp-architecture-definition-v3.pdf, per sources/manifest.csv). Page numbers: the printed page numbers (1–6) match the PDF pages and the text file's [page N] markers, unlike the 2025 Architecture Update (open question 29). All six pages were checked against the PDF.

Summary. The paper explains how NASA turns the Moon to Mars Objectives into an architecture: by answering six guiding questions (Why, Who, Where, What, When, How) through "architecture definition tasks", in an order set by "architecture roadmapping". It argues that answering "Why?" first, rather than "When?" as Apollo did, keeps the architecture tied to NASA's objectives. Its Table One is a snapshot of twelve Mars "priority key definition tasks", MD-01 to MD-12, with four marked closed. ADD Rev C points to it for "more information about the flow of guiding questions and architecture roadmapping" (ADD Rev C, p. 74, footnote 22).

What it replaces. "This white paper supersedes two previous Moon to Mars Architecture white papers: Systems Analysis of Architecture Drivers (2022) and Key Mars Architecture Decisions (2023). It reflects updates to NASA's approach for defining the Moon to Mars Architecture" (p. 1, the "NOTE" box). Neither superseded paper is among the wiki's sources (none of the files in sources/manifest.csv carries either title). The 2025 Architecture Update describes the paper as one that "Updates two previous white papers" (2025 Architecture Update, p. 17).

Contents, and where the wiki uses them

Page	Section	What it holds	Wiki home
1	Introduction; Figure One "Six guiding questions"	The six questions; trade space; key definition tasks; outcomes; why roadmapping matters	Architecture definition process
2	Figure Two "Architecture question flow, prioritizing 'When'"; Impacts of Guiding Questions; Key Terms table	The Apollo example; six key terms	Architecture definition process
3	Figure Three "… prioritizing 'Why'"; Architecture Definition; Architecture Roadmapping	Iterative, not linear; what a (key) definition task is; the crew-number and habitat-window examples; the three-step process	Architecture definition process; Key definition tasks
4	Figure Four "Notional definition flow"; Priority Definitions	The digital model; how the Mars catalog was built ("nearly 100 candidate definition tasks"); priority definitions	Architecture definition process
5	Definition Task Outcomes; Case Study (Mars surface power); Conclusion; Table One	Three kinds of outcome; MD-07 as a worked example; MD-01 to MD-12	Key definition tasks
6	Key Takeaways; References	Five-line summary; four references	this page

What the PDF shows that the text layer loses

• Figure One (p. 1) is a ring of six colored circles: WHY "We Go", WHO "Is Involved", WHAT "We Do There", WHERE "We Go", WHEN "We Go", HOW "We Go". The center reads "Answers to six driving questions help NASA tell a compelling architecture story".
• Figures Two and Three (pp. 2–3) are the same two figures as ADD Rev C pp. 73–74, with the same labels and example drivers (both checked against the PDFs). They are tabulated on Architecture definition process.
• Figure Four (p. 4) is described on Architecture definition process. It is notional and names no tasks.
• Table One (p. 5) comes out of the text layer as IDs, titles and body text interleaved. The rendered table pairs each ID with its title, and its shading marks MD-02, MD-04, MD-05 and MD-07 as closed. The table is on Key definition tasks.

What it adds to ADD Rev C

ADD Rev C Section 3.1.2 (pp. 73–74) carries a shorter version of the roadmapping argument and the same two figures. The paper adds:

• the six questions listed once each (p. 1), where the ADD's list repeats "Where" and omits "When" (open question 21)
• the Apollo example for prioritizing "When", and the Mars consequences (p. 2)
• a key-terms table (p. 2)
• the three-step roadmapping process, the digital modeling environment and Figure Four (pp. 3–4)
• how the Mars catalog was built, "nearly 100 candidate definition tasks" (p. 4)
• Table One: a "snapshot" of twelve Mars priority key definition tasks by title, with closed ones shaded (p. 5). For "a complete list of identified definition tasks", the paper refers readers to the ADD (p. 4). ADD Section 3.1.3 lists only the four completed ones; ADD Appendix C also lists MD-01 to MD-12 (p. 194), with the same titles word for word and the same four done (Key definition tasks).
• three kinds of definition outcome, each with a Mars example, and the MD-07 case study (p. 5)

It covers Mars tasks only. It names no lunar (LD) task, though it says "Whether planning future lunar exploration or preparing for the first human missions to Mars, NASA uses the same roadmapping process" (p. 1).

Key takeaways (p. 6)

As printed in the box:

• "The Moon to Mars Architecture must answer a series of overarching questions: Who, What, When, Why, and How?"
• "To address these guiding questions and develop the architecture, NASA conducts architecture definition tasks."
• "Some tasks have major impacts on the end-to-end architecture. The agency tracks these 'key definition tasks' to capture their relationships and flow-down impacts and establishes a priority order to maximize efficiency and minimize re-work."
• "Completed key definition tasks can result in a ground rule, decision, methodology, or other definition outcome that shapes the architecture."
• "NASA's Architecture Definition Document captures the latest list of ongoing key definition tasks and the results of completed key definition tasks."

Oddities

• Five questions, not six, in the takeaways. The first takeaway lists "Who, What, When, Why, and How?" and leaves out "Where" (p. 6, PDF checked). The introduction lists all six (p. 1) (open question 21).
• Three orders for the same six questions. The introduction asks "Why we go? Who is involved? Where we go? What we do there? When do we go? How we go?" (p. 1). Figure One sets them in a ring, and Figure Three's recommended flow runs Why, Where, Who, What, When, How (p. 3). The paper says that "in practice, developing the architecture is iterative, not linear" (p. 3), so the wiki doesn't treat this as a contradiction.
• "Utiliation Options", as printed, under WHAT in Figure Two (p. 2). ADD p. 73 prints the same.
• "ser-vice" in the key-terms table's definition of an architecture definition task (p. 2), and "complement each another" (p. 3), both as printed.
• Title variants. Table One's "Initial Human Mars Segment Science Objectives Priorities" (MD-01) is "Science Objective Priorities" in the tech-gap spreadsheet. Its "Primary Mars Surface Power Generation Technology" (MD-07) matches the spreadsheet; ADD Section 3.1.3 has "Mars Primary Surface Power Generation Technology" (p. 75).
• LD and MD are not expanded here either (open question 27).

References (p. 6)

1. NASA's Moon to Mars Objectives (the September 2022 document; see Moon to Mars Objectives (2022))
2. John F. Kennedy's address to Congress, May 25, 1961 (cited for the Apollo mandate)
3. The Moon to Mars Architecture Definition Document page
4. "Mars Surface Power Technology Decision, 2024 Moon to Mars Architecture White Paper" (source page; its content is on Key definition tasks)

Related pages

Architecture definition process · Key definition tasks · Humans to Mars · ADD Rev C · 2025 Architecture Update · "Why Moon and Mars?" white paper