Transportation Systems (T)

Summary. Moving crew and cargo through every phase of a mission: "launch; transportation through space; entry, descent, and landing; ascent; and Earth re-entry" (ADD Rev C, p. 44). It has the most Rev C elements, six: SLS, Orion, the Human Landing System, CLPS, the Human-Class Delivery Lander and the Lunar Surface Cargo Lander. Seven technology gaps list it, four of them Mars-only and one named in the Moon Base Users Guide (near-term). A 2024 white paper found "a gap in cargo lander delivery … between 500 kg and 12,000 kg" (below). Another 2024 paper explains why heritage Mars landers, which landed about 1 t or less, don't scale to human-class landers of 26–36 t (below). Decomposition letter: T.

NASA's description

"This sub-architecture comprises capabilities that provide transportation functions for all phases of Moon and Mars exploration for both crew and cargo. This includes launch; transportation through space; entry, descent, and landing; ascent; and Earth re-entry.

Transportation systems interface with a variety of systems and payloads in a variety of space and surface environments. These include habitation and other human support systems, ground and in-space communications systems, as well as refueling or recharging systems.

Initial lunar segments will include transportation capabilities for the transit of crew and cargo to cislunar space, the landing of crew and cargo on the lunar surface, ascent of crew and limited cargo to cislunar space, and the safe return of crew and cargo to Earth. As missions expand to Mars, the transportation sub-architecture will evolve to include Mars transit; entry, descent, and landing; and ascent systems for cargo and crew." (ADD Rev C, p. 44)

In the segments

From ADD Rev C:

• Human Lunar Return. Artemis I "tested crewed transportation to and from cislunar space (TH-1, TH-2)" (p. 25). The Crewed Initial Lunar Surface reference mission starts "with transportation": Earth to cislunar space, staging and assembly in cislunar space, cislunar space to and from the surface, and return to Earth (p. 25). See Human Lunar Return for the change to Artemis III.
• Foundational Exploration. TH-1, TH-2 and TH-11 "address a need for transportation systems to transfer crew and cargo to and from Earth, through cislunar space, and between lunar orbit and the surface"; infrastructure objectives LI-5 and LI-6 drive "transportation" (p. 28). Non-polar sorties need "crew descent, landing, and ascent at non-polar sites" (p. 30). An area of future work: "Increasing cargo mass delivered to and returned from the lunar surface" (p. 32).
• Sustained Lunar Evolution. "ISRU-derived propellants could reduce transportation costs" (p. 34); industry could provide "regular and likely reusable lunar access (both robotic and human)" (p. 35).
• Humans to Mars. "transportation systems that can operate between Earth and the Mars vicinity and surface (TH-5, TH-6)" and "systems that return cargo from Mars to Earth (TH-12)" (p. 38). Future work includes "transportation; return propellant strategies; … entry, descent, landing, and ascent options" (p. 39). A 2024 white paper sets out the Mars EDL problem (below); another weighs Mars ascent propellant (ISRU Systems).

Elements

From the segment tables (ADD Rev C, pp. 26, 31–32):

Element	Segments
Commercial Lunar Payload Services	Human Lunar Return, Foundational Exploration
Human Landing System	Human Lunar Return, Foundational Exploration
Human-Class Delivery Lander	Foundational Exploration
Lunar Surface Cargo Lander	Foundational Exploration
Orion Spacecraft	Human Lunar Return, Foundational Exploration
Space Launch System	Human Lunar Return, Foundational Exploration

See the elements index. The three lunar delivery elements are sized against each other on the Human-Class Delivery Lander page. The Moon Base sources name CLPS more than any other element (CLPS).

Technology gaps

Seven gaps list this sub-architecture, all from the #11xx group (derived from the tech gaps spreadsheet, Sub-Architectures column). MB = named in the Moon Base Users Guide (near-term).

Gap	Rating	MB
#1107 Cryogenic Fluid Transfer	4
#1104 Mars Transportation Propulsion	6
#1103 Mars Entry, Descent, and Landing	10
#1105 Mars Ascent Propulsion	12
#1101 Lunar Precision Landing and Hazard Avoidance	27	MB
#1106 Cryogenic Fluid Storage	32
#1102 Mars Precision Landing and Hazard Avoidance	37

Lunar surface cargo (ACR24 white paper, 2024)

The 2024 white paper "Lunar Surface Cargo" compares cargo demand with the landers NASA had in 2024. It predates Revisions B and C, so it is context, not the current architecture. Page numbers in this section are the paper's.

Demand (p. 2). NASA assessed "a representative sample of planned and potential future surface cargo": "many one-time delivery missions for habitation, various types of mobility systems, power augmentation, communications relays, and freezers", plus recurring logistics for crewed missions "(assumed to occur on an annual basis)". "In aggregate, NASA forecasts a cargo demand range of 2,500 to 10,000 kg per year for annual recurring logistics and some frequency of small to large elements during the Foundational Exploration campaign segment. This includes occasional large cargo deliveries of up to 15,000 kg for elements like rovers or habitation modules." The takeaways say 2,000 rather than 2,500 (p. 6). Figure 1 plots each item's mass range under the segment banner (item labels on the source page).

Capability in 2024 (Table 1, p. 3):

Lander type	Mass delivery capability (kg)	Provider
CLPS – Current Task Orders	70 – 475	U.S.
HDL Cargo Lander	0 – 12,000 or 15,000	U.S.
ESA Argonaut Lander*	Up to 2,100	International
JAXA Cargo Lander Capability	Under Study	International

"*Note: Delivered mass represents cargo platform element + payload." The HDL is the cargo variant of the HLS program's landers (p. 2).

The gap. "Despite the capabilities currently in development, a gap in cargo lander delivery has been identified between 500 kg and 12,000 kg, for which significant demand exists" (p. 3). "HDL is the only lander currently expressed in the architecture that can deliver beyond 500 kg to the lunar surface" (p. 6). Current development meets "the Human Lunar Return segment's cargo delivery needs", but "there is a substantial architectural gap in lander capability for the Foundational Exploration segment and beyond" (p. 5).

What a cargo lander must do. The paper's "conceptual reference mission for cargo lander delivery" (p. 1):

• "Delivers non-offloaded and/or offloaded cargo to the lunar surface."
• "Provides all services necessary to maintain cargo from in-space transit through landing on the lunar surface until the cargo is either offloaded from the lander or in an operational state where these services from the lander are no longer needed, in accordance with cargo lander provider agreements."
• "Ensures successful landing at an accessible and useable location on the lunar surface with sufficient precision."
• "Establishes safe conditions on the lunar surface for the crew to approach the lander."
• "Verifies health and functionality of non-offloaded and/or offloaded cargo."
• "Performs any lander end-of-life operations — including potential relocation — ensuring that the cargo or other surface assets are not adversely affected by the lander after landing operations."

Service interfaces may cover offloading, "compatibility to surface mobility system interactions", and power, communications, data or thermal dissipation for the cargo; crew may need "EVA touch interfaces" (p. 1).

Strategy (p. 3). A "responsive cargo lander portfolio" reaching "diverse locations across the lunar South Pole region"; Figure 3 lays eight potential landing regions over a map of the Washington, D.C., area (p. 4). "Leveraging provider diversity in a mixed cargo lander fleet approach addresses some key lessons learned from the International Space Station, including the need for dissimilar redundancy to avoid a situation in which any system becomes a single point of failure." NASA also found "additional capability gaps for lunar cargo and sample return": "The capacity needed to achieve stated objectives greatly exceeds the return capability offered by existing elements."

What changed by Rev C (the wiki's comparison):

• Revision B added the Lunar Surface Cargo Lander (ADD Rev C, p. 3), "much smaller than HDL, delivering moderate amounts of cargo" (ADD p. 59). The paper had said a cargo "reference mission" would be added in Revision B (p. 1). Rev C gives the lander no mass, and the wiki doesn't size it from the paper's 500–12,000 kg gap (open question 45).
• Rev C's one-pagers give no masses for CLPS, the HDL or the cargo lander, so Table 1 has no Rev C counterpart.
• Cargo return became one of Rev C's Foundational Exploration areas of future work: "Increasing cargo mass delivered to and returned from the lunar surface" (ADD p. 32).
• Lunar logistics is one of the 2025 Update's three focus areas for 2026, and the Update points to this paper on logistics (Logistics Systems; Update, pp. 9, 18).

Mars entry, descent and landing (ACR24 white paper, 2024)

The 2024 white paper "Mars Entry, Descent, and Landing Challenges for Human Missions" (source page) is "a high-level overview" of why landing people on Mars is hard (p. 1). It predates Rev C, so it is context. Page numbers in this section are the paper's.

• What EDL is. "EDL is one of the highest-risk phases of spaceflight. During EDL, the spacecraft enters and transits a planetary atmosphere, decelerates, and touches down onto the planetary surface" (p. 1). Three phases (p. 2):
  • Entry, from the "atmospheric entry interface", slowing "from hypersonic velocities" while managing aerodynamic forces and heating.
  • Descent, which "begins with deployment of a dedicated deceleration system", typically "during supersonic flight". Heritage parachutes "are inherently un-steerable, and wind drift can add a kilometer or more of landing error"; retropropulsion "can help avoid hazards".
  • Landing. Retropropulsive engines "induce plume-surface interaction (PSI) with the ground", which erodes the surface and throws debris at "the landing vehicle and nearby surface assets".
• The record. At Mars, "only 12 out of 19 attempted robotic landings have been successful" (p. 1).
• Why Mars is harder (pp. 3–4), headings as printed:
  • Atmosphere. Thin, but heating is "substantial enough to result in loss of mission". Density at the surface is "comparable to Earth's atmospheric density at approximately 30 kilometers in altitude". Variability in density and wind gives "large uncertainty in predicted touchdown location" and "limits reachable surface site altitudes". What still limits heritage accuracy: entry navigation errors, "parachute sensitivity to wind variability", and heatshields that "complicate the use of navigation sensors during entry".
  • Surface Hazards. "The best images from the Mars Reconnaissance Orbiter provide 25 cm resolution. At that resolution, mission planners can identify rocks and features as small as 1 meter in size." Viking 1 came down 8 m from a 1-m boulder. PSI "could produce unstable or unacceptably sloped landing surfaces", and PSI and atmospheric dust "affect EDL sensor measurements".
  • System Validation. "There are no Earth-analog test conditions that completely mimic Mars EDL … a 'test as you fly' approach is simply not possible." NASA combines modeling with component tests in "wind tunnels, vacuum chambers, arc jets, suborbital rockets, and aircraft".
  • System Scalability. Since the 1970s, Mars EDL has used "scaled variations of the original Viking entry capsule and parachute designs". Flown systems landed "between 0.3 and 1 metric tons"; human missions need "over 20 metric tons", "well beyond what a scaled-up Viking design could achieve".
• Landing ellipses (Figure 2, p. 2, read from the PDF): from Viking's 280 x 100 km (1976) to Perseverance's 8 x 7 km (2021), against "Mars Human Landing Systems <0.1 km". "Landing ellipses for human missions to Mars will be smaller than any previous robotic missions."
• Heritage against human scale (Figure 5, p. 5, read from the PDF). Mars 2020: 4.52 m capsule, 3.368 t at entry, 1.050 t landed, sky crane. The projected "Human-Scale Lander", under a "New Paradigm" banner: 16+ m, 49–65 t at entry, 26–36 t landed, no parachute ("N/A"), landing altitude "+/- 2.0" km, "Supersonic Retropropulsion". The full table is on the source page.
• What must be developed (p. 4; Figures 6–9):
  • Entry. High-fidelity simulation of "large, inflatable aerodynamic decelerators and higher-lift aerodynamic bodies to inform and gain insight into industry development efforts".
  • Deceleration. These "cannot be validated with test articles at Mars, but subscale development and high-altitude flight testing on Earth can produce valuable data for developing human-class systems."
  • Guidance and navigation. More precise sensors and algorithms, "alongside supersonic retropropulsion", and "advanced terrain relative navigation".
  • Landing systems. "Higher-thrust engines on human-scale landers will likely create significant PSI ejecta and obscure landing sites." "While lunar PSI data can be valuable, the Martian regolith behaves differently than the lunar regolith, requiring Mars-specific modeling and ground testing."
• The Moon's part. "Landings on the Moon provide valuable insight for Mars EDL, although Mars possesses several unique characteristics that create new EDL challenges" (p. 3).

What changed by Rev C: Mars EDL

The wiki's comparison. The paper names no gap or definition task, so every pairing below is the wiki's.

• Two gaps carry the subject: #1103 (rated 10) and #1102 (rated 37), both Mars-only. #1103's child gaps are close to the paper's list: supersonic retropropulsion, low- and mid-L/D entry systems, and "Robust modeling and simulation for high-mass Mars atmospheric entry" (ADD p. 254).
• Three landed-mass figures. The paper's text says "over 20 metric tons" (p. 4); its Figure 5 projects 26–36 t (p. 5); #1103's 2025 target is "payloads between 25 and 75+ metric tons" (ADD p. 254). The 2025 upper end is more than twice Figure 5's. No source explains the difference.
• Accuracy. Figure 2's "<0.1 km" for human landers matches #1102's target, "Landing accuracy on order of 100 m" (ADD p. 253). #1102 gives Perseverance's ellipse as "7.7 km x 6.6 km", which Figure 2 rounds to 8 x 7 km. #1102's obstacle target, "on order of 1 m", is the smallest size the paper says MRO's best images can show (p. 3).
• Three Mars data gaps cover the paper's themes: the EDL atmosphere (DN-004 M), plume ejecta (DN-005 M) and landing-site alteration (DN-006 M).
• Two open definition tasks: "Cargo Mars Entry, Descent, and Landing Technology" and "Crew Mars Entry, Descent, and Landing Technology" (ADD Appendix C, category 10; Key definition tasks). Both are among #1103's definition tasks.

In the February 2024 workshop briefing: Mars EDL

Before the paper, the February 2024 "Mars Challenges" briefing showed the same banner over a table of Mars landers and a "Human Class Lander Concept" landing 36,000–40,000 kg (entry 47,000–65,000 kg, diameter 16–19 m), with "Upcoming ACR24 White Paper" beside it and "New paradigm needed for Human Class Landers" (Mars challenges briefing, slide 5). The paper's Figure 5, newer, projects 26–36 t, and this page keeps the paper's figures; the difference is open question 91. The same deck notes that humans have ascended only from Earth and the Moon, and that at Mars a "Vehicle likely arrives unprepared for launch" (slide 6).

Moon Base Phase 1

The Users Guide's "Transportation systems (cargo)" group: "Systems that convey cargo between Earth and the Moon (e.g., launch vehicles, transportation systems, cargo landers)" (Users Guide, p. 10). Two FN-T functional gaps: transporting "100s of kg" and "1000s of kg" of cargo from Earth to South Pole sites. Capability target: "Deployment of landers with two metric ton cargo delivery capability to the lunar South Pole region." #1101 is named under the headline challenge "Landing Safely and Accurately on the Lunar Surface" (Technology and knowledge challenges). Full list: Phase 1 functional gaps.

Related pages

Sub-architectures · Infrastructure Support · Logistics Systems · Elements · Human Lunar Return · Gaps index · Lunar Surface Cargo · Mobility Systems · Humans to Mars · Mars EDL Challenges

Sources

ADD Rev C, pp. 3, 25–26, 28, 30–32, 34–35, 38–40, 44, 59, 194–197, 253–254 · Tech gaps spreadsheet · Mars EDL Challenges, pp. 1–5 (pp. 2–5 checked against the PDF) · Users Guide, pp. 10, 12 · Lunar Surface Cargo, pp. 1–6 (checked against the PDF) · 2025 Architecture Update, pp. 9, 18 · Mars challenges briefing, February 2024, slides 5–6