Gap report: Moon Base / pressurized rover design band

PYRION proposal — evidence coverage, not a prediction or a safety assessment

Engine: pyrion-applicability-engine 0.2.0. Fingerprint (SHA-256 of this report's data): 89c08719778164761886fa09cf170f6c1f6f3ee9ea9775dfb23a09cd95724ed7

The band

Gravity: partial gravity (0.16 g, shown only). Vertices (oxygen, total pressure):

• NESC 8.2 psia, low oxygen corner: 26.5 % O2, 8.2 psia (56.54 kPa) — closing corner (PYRION convention)
• NESC Exploration Atmosphere 8.2 psia / 34 % O2: 34 % O2, 8.2 psia (56.54 kPa) — sourced
• closing corner 34 % O2 at 10.2 psia: 34 % O2, 10.2 psia (70.33 kPa) — closing corner (PYRION convention)
• NESC Exploration Atmosphere 10.2 psia / 26.5 % O2: 26.5 % O2, 10.2 psia (70.33 kPa) — sourced

How it is closed: Bounding rectangle of the two NESC Exploration Atmospheres (26.5 to 34 % O2, 8.2 to 10.2 psia). The challenge corner (30 % O2, 10.2 psi) lies on its top edge. The challenge band itself is open (30 % or more, 10.2 psi or less).

PYRION convention: the two closing corners (26.5 % O2 at 8.2 psia and 34 % O2 at 10.2 psia) are not stated by any source; the rectangle is a way to close an open band with sourced limits, not a NASA design envelope. The 26.5 to 30 % part of the band is below the challenge text (30 % or more) but inside the NESC atmospheres.

What PSI covers today

Cells of the band where at least one investigation is comparable (APPLICABLE): 0 % (0 of 81).

• solid fuel: 0 % (0 of 81)
• liquid fuel: 0 % (0 of 81)
• gas fuel: 0 % (0 of 81)

A cell is covered when at least one investigation is APPLICABLE there, by the same rules and the same ±0.5 % tolerance as evaluate(). Grid fractions depend on the grid; a tested line covers the cells on it within the tolerance but has no area.

Nearest evidence per fuel phase (gravity regime left open)

• solid: PSI-26 BASS (doi:10.60555/58h4-dy80), extrapolation (far outside), normalized distance 0.281; tested in microgravity.
• liquid: PSI-69 FLEX (doi:10.60555/mbq8-0451), extrapolation (outside), normalized distance 0.019; tested in microgravity.
• gas: PSI-159 ACME CFI-G (doi:10.60555/cyt1-kh64), applicable, normalized distance 0.11; tested in microgravity.

What FM2 and LUCI would add (hypothetical)

Hypothetical records are built in memory from what the planning documents state; they are never written to the data.

• FM2 as planned (4 tests, one fabric, solid fuel): 9 more cells covered (11.1 % of the grid). Shape: line — all four tests are at one pressure (8.2 psia), so FM2 covers a LINE of the band, not an area; the share of the band area inside the hull of its test points is 0 %.
• FM2 with both ends of its stated ± 0.3 psi (optimistic what-if, not a plan): 18 cells (22.2 % of the grid); hull area inside the band 15 %.
• LUCI: cannot be placed. LUCI burned samples "in air at normal pressure" in simulated partial gravity (rotating vehicle). The source passage gives no pressure figure and no oxygen figure, so PYRION cannot place it in the oxygen–pressure plane and does not guess one.

Minimum test points (PYRION's geometric convention)

The smallest set of test points whose region (hull plus the 0.5 % tolerance) covers the band is the set of vertices of the band polygon, deduplicated: for a convex band, the hull of the vertices is the band itself, and no smaller set has that hull. It assumes one test per vertex, at the band gravity, for the stated fuel phase (and material), and that a test inside its own region counts like a measured point; it says nothing about how many repeats a test needs. This is a minimum under PYRION's convention that the region between measured tests counts as covered, separately for each material, flow velocity and sample thickness. Flammability limits are thresholds and need not behave monotonically: Olson and T'ien (NTRS 20000057046, PDF p. 3) report, for gaseous diffusion flames in drop-tower tests, "a quenching limit at low stretch and a U-shaped flammability boundary with fuel percentage and stretch rate as coordinates was experimentally demonstrated". Covering the corners therefore does not show that everything between them behaves like the tests; it only makes the band comparable under that convention.

• 26.5 % O2, 8.2 psia (NESC 8.2 psia, low oxygen corner) — already covered by FM2 (planned)
• 34 % O2, 8.2 psia (NESC Exploration Atmosphere 8.2 psia / 34 % O2) — already covered by FM2 (planned)
• 34 % O2, 10.2 psia (closing corner 34 % O2 at 10.2 psia) — missing
• 26.5 % O2, 10.2 psia (NESC Exploration Atmosphere 10.2 psia / 26.5 % O2) — missing

Missing: 2 of 4 points. FM2 contributes 2 (those on its own line of tests). Testing the missing points would make the band comparable under the convention above; it would not by itself show that the band is safe or that the region between tests behaves like them.

Evidence Readiness Level

PYRION convention, like NASA's TRL, for evidence; it measures how much measured evidence exists, never safety.

At the centre of the band: ERL 0 (no test). No PSI test in partial gravity anywhere; the investigations state only microgravity and normal gravity.

• NESC 8.2 psia, low oxygen corner: ERL 0 (no test)
• NESC Exploration Atmosphere 8.2 psia / 34 % O2: ERL 0 (no test)
• closing corner 34 % O2 at 10.2 psia: ERL 0 (no test)
• NESC Exploration Atmosphere 10.2 psia / 26.5 % O2: ERL 0 (no test)

Scale:

• ERL 4 — measured: PSI measured this condition: at least one investigation is comparable (APPLICABLE).
• ERL 3 — near extrapolation: Not measured, but just outside tested data, or each setting was tested only separately (extrapolation: just outside or combination).
• ERL 2 — far extrapolation: Not measured and well outside tested data (extrapolation: outside or far outside).
• ERL 1 — comparable only in another regime: Comparable oxygen and pressure records exist only in another gravity regime, fuel phase or atmosphere type (regime barrier).
• ERL 0 — no test: No PSI test in that gravity regime anywhere, or the extracted records cannot be compared with it.

Sources

• band gravity: Ruff, Impact of Lunar Gravity on Material Flammability, Lunar Surface Science Workshop 2021, page 3, "How is flame spread affected by Lunar-g?", https://ntrs.nasa.gov/api/citations/20210020446/downloads/LSSW%20Presentation_8-12-2021_FINAL.pdf — "glunar = 0.16 gearth"
• convention: flammability limits need not be monotonic: Olson and T'ien, Near-Limit Flamelet Phenomena in Buoyant Low Stretch Diffusion Flames Beneath a Solid Fuel (NTRS 20000057046), PDF p. 3, Introduction (describing a drop-tower study of gaseous diffusion flames), https://ntrs.nasa.gov/api/citations/20000057046/downloads/20000057046.pdf — "a quenching limit at low stretch and a U-shaped flammability boundary with fuel percentage and stretch rate as coordinates was experimentally demonstrated"
• band vertex: NESC Exploration Atmosphere 8.2 psia / 34 % O2: NESC, Impacts of Reduced Pressure Atmospheres on ECLSS (NESC-RP-20-01610), page 18, section 6.2 Spacecraft Cabin Atmospheres for Exploration, https://ntrs.nasa.gov/api/citations/20260003925/downloads/20260003925.pdf — "One of the most enabling means is to design Exploration surface habitat(s) to operate at cabin atmospheric pressures low enough to reduce or eliminate prebreathe protocols. For planning purposes, and for the purpose of this assessment, the potential atmosphere conditions that are being considered are 10.2 psia/26.5% O2 and 8.2 psia/34% O2."
• band vertex: challenge corner 30 % O2 at 10.2 psi: Flame in Freefall: SI-Powered Fire Safety Insights from Microgravity Combustion Data (challenge statement), Potential Considerations, "Spacesuits and oxygen concentration", https://www.spaceappschallenge.org/2026/challenges/flame-in-freefall/ — "The intermediate oxygen concentration used on the Moon will likely be 30% or greater, with a corresponding pressure of 10.2 psi or less."
• FM2 (planned): FM2 (Flammability of Materials on the Moon), NASA web page, web page — "The experiment burns four fuel samples individually in atmospheric conditions planned for future lunar habitats or vehicles."
• FM2 (planned): FM2 science requirements, NTRS 20260001966, PDF p. 10 (slide 9) — "Test 1: 8.2 psia (+/- 0.3 psi), 37% O2 , balance nitrogen) Test 2: 8.2 psia (+/- 0.3 psi), 33% O2 , balance nitrogen) Test 3: 8.2 psia (+/- 0.3 psi), 29% O2 , balance nitrogen) Test 4: 8.2 psia (+/- 0.3 psi), 25% O2 , balance nitrogen)"
• FM2 (planned): FM2 fuel, NTRS 20260001966, PDF p. 10 (slide 9) — "Fabric sheets (Synergy Pro 'Navy') mounted between thin metal frames"
• FM2 (planned): FM2 test concept, NTRS 20260001966, PDF p. 5 (slide 4) — "Test a material with an expected Lunar LOC of 24-26% and an expected oxygen consumption of 0.08 mol fraction"
• LUCI: LUCI (Blue Origin New Shepard flight), NTRS 20250010653, PDF p. 12 — "Two samples are burned simultaneously in air at normal pressure: Cotton-fiberglass composite fabric sheet and a 4-mm diameter rod of acrylic plastic (polymethyl methacrylate)."
• LUCI: LUCI vehicle rotation, NTRS 20250010653, PDF p. 12 — "A steady vehicle rotation of 11 RPM is established, with an effective radius of rotation of 1.22 m at the experiment location."
• LUCI: LUCI follow-on data, NTRS 20250010653, PDF p. 18 — "Flammability limits (%O2) for a subset of materials in Lunar-g Measurements of the flame spread rate over materials in exploration atmospheres"

PYRION proposal — evidence coverage, not a prediction or a safety assessment.