Pass 01 — Research

Source gathering for q2 (Earth atmospheric ceiling). Five tier-S/A primary sources retrieved fresh; emission factors and current-cadence-impact baselines established.

Tier-grouped source list

Tier S — peer-reviewed primary

Tier A — peer-reviewed reviews / credentialed preprints

NOT YET FETCHED (flagged for re-pass)

• NASA TM-20240013276 Impact of Spaceflight on Earth's Atmosphere — PDF fetch returned binary streams; needs HTML alternative or alternative NTRS doc.
• Barker et al. 2026 Earth's Future on megaconstellation radiative forcing — paywalled (402).
• Direct fetch of Maloney 2025 JGR (only NOAA CSL secondary coverage retrieved).

Topics surfaced (add to topics.yaml at report level)

• rocket-ozone-depletion — direct ozone destruction from chlorine (SRM), black carbon (kerosene), NOx (reentry)
• stratospheric-water-vapor — H2O from methalox/LH2 combustion at stratospheric altitudes; HOx-cycle ozone effects
• reentry-alumina-mesosphere — Al2O3 from spacecraft ablation 40-70 km; polar mesospheric heating; polar vortex effects
• propellant-specific-emissions — per-kg emission factors by propellant type (Ryan 2022 canonical)
• polar-stratospheric-clouds — alumina/metals nucleation effects on PSCs (Murphy 2023, Maloney 2025)

Methalox-specific gap

The peer-reviewed literature lacks dedicated atmospheric modeling for a pure-methalox future. Revell 2025 explicitly notes methalox as a research gap. Ryan 2022's emission-factor table omits methalox (we can derive it from stoichiometry: 0.6 kg CO2 + 0.49 kg H2O + ~10 g NOx + minimal BC per kg propellant). At Starship-dominated cadence the ozone and aerosol picture should differ substantially from the Revell-2025 mixed-fuel projection — no chlorine, dramatically less BC, no alumina from combustion (alumina from reentry of payloads remains, however).

This is a real research gap. q2's calc pass must derive the methalox-specific atmospheric ceiling first-principles.

Coverage assessment

• Tier S is good: 4 primary peer-reviewed papers covering the four main atmospheric impact pathways (direct ozone, stratospheric H2O, reentry alumina, propellant emission factors).
• Tier A coverage thin: Kukreja 2025 covers the LCA frame but not specific cadence-thresholds. Could add IPCC AR6 Chapter 8 (atmospheric composition) for general radiative-forcing context.
• Tier B (public figures): Casey Handmer, Eli Dourado, Eloise Marais (academic atmosphere specialist) all have public positions. None directly compiled here; could be a re-pass target.
• Tier C/D: Industry trade coverage (Space.com, Phys.org) consolidates the same primary findings — not separately reviewed in the current pass.

Sub-pass deliverables

• 5 extract.md files in sources/ (all tier S/A)
• 1 pass-01-research.md (this file)
• 0 entries in claims.yaml — claims come from calc + reconcile

Anti-pattern hygiene check

• No claim-bearing prose in this pass ✓
• No source borrowing across passes yet — calc-pass will be sources-sealed ✓
• All extracts have proper frontmatter (tier, type, peer_reviewed, venue, year, topics) ✓
• No hallucinated sources — every extract corresponds to a fetched WebFetch or PMC retrieval ✓

Next sub-pass

Calc — derive Earth atmospheric ceiling first-principles, sources sealed. Apply lessons from q1: distinguish fundamental (atmospheric absorption capacity, ozone destruction rate per unit injection, irreversible thresholds) from willingness-to-pollute (current-cadence projections that scale linearly until they don't).

overall:
  verdict: weak
  summary: "The stoichiometric H2O arithmetic is mostly usable, but the NOx-driven ceiling is not defensible. The reentry-NOx factor, NOx residence/reservoir treatment, and Revell-to-catastrophe extrapolation are the load-bearing failures."

findings:
  - target: "q2.c1 methalox stoichiometry"
    target_kind: claim
    verdict: partial
    reason: "CH4 + 2 O2 -> CO2 + 2 H2O is correct, and the H2O mass is close. But the 3.6:1 fuel-rich treatment is oversimplified: incomplete combustion would produce substantial CO/H2 before afterburning, not simply a 5% CO2 deficit plus 5% unburned CH4."
    severity: medium

  - target: "NOx 20 g/kg-propellant"
    target_kind: claim
    verdict: weak
    reason: "Older rocket inventories use launch NOx factors in this rough range, but newer gridded inventories apply altitude-dependent afterburning: indirect NOx falls from 33 g/kg at ground to under 1 g/kg above 14 km. Treating 20 g/kg as a bulk stratospheric methalox factor is not supported. Source: https://www.nature.com/articles/s41597-024-03910-z"
    severity: medium

  - target: "reentry NOx 5 kg/kg-reentered"
    target_kind: claim
    verdict: contradicted
    reason: "This is too high by over an order of magnitude for spacecraft-style reentry. Larson/Park give about 17.5% of spacecraft mass as NOx; Vliex et al. use 17.5% for reusable objects and 40% for discarded objects, while Ryan 2022 used 17.5% for reusable and 100% only for complete burn-up cases. Source: https://repository.library.noaa.gov/view/noaa/21694/noaa_21694_DS1.pdf and https://www.nature.com/articles/s41597-024-03910-z"
    severity: high

  - target: "stratospheric reservoir baselines"
    target_kind: section
    verdict: partial
    reason: "O3 ~3 Gt and stratospheric H2O order-of-magnitude are acceptable. The NOx baseline is not a sound reservoir for this calculation: NOx/NOy chemistry is short-lived, altitude/season dependent, and not well represented by a 0.5 Mt box with 5-year accumulation."
    severity: medium

  - target: "50% stratospheric injection fraction"
    target_kind: claim
    verdict: partial
    reason: "A 50% above-tropopause fraction is plausible as a crude H2O/CO2 screen, but vertical placement matters. Recent inventories put about 20-29% of propellant burn in the stratosphere, about 10-19% in the mesosphere, and a large fraction above 80 km depending on profile; it is not valid for NOx because the NOx emission index is altitude dependent. Source: https://www.nature.com/articles/s41597-024-03910-z"
    severity: medium

  - target: "perturbation ratios"
    target_kind: section
    verdict: partial
    reason: "The scenario-table arithmetic follows from the stated inputs, but the inputs are wrong for NOx. The later NOx threshold table is internally inconsistent by about 10x: if 250 launches gives +140%, then 5% occurs near 9 launches/yr, not 90."
    severity: high

  - target: "Revell 2025 extrapolation"
    target_kind: claim
    verdict: unsupported
    reason: "Revell's 2040-launch result is for a mixed-fuel future and is driven mainly by chlorine chemistry and black-carbon radiative/dynamical effects; Revell explicitly says rocket-emitted NOx is insignificant in that setup and omits reentry NOx. Linear scaling to -30% or 50-80% global ozone loss is not justified. Source: https://www.nature.com/articles/s41612-025-01098-6"
    severity: high

  - target: "catastrophic ozone levels at 1e5-1e6 launches/yr"
    target_kind: claim
    verdict: contradicted
    reason: "Larson 2017 modeled 1e5-1e6 high-rate reusable hydrogen flights and found about 0.5% global ozone loss at 1e5 and about 11 DU at 1e6, not tens of percent global ozone loss. Starship/methalox is not identical, but this directly undercuts the claimed ozone-catastrophe scaling. Source: https://repository.library.noaa.gov/view/noaa/21694"
    severity: high

  - target: "missed atmospheric pathways"
    target_kind: topic
    verdict: partial
    reason: "The pass mentions some missing pathways but does not integrate them: BC-driven stratospheric heating, HOx/NOx coupling, PSC changes from H2O, mesospheric H2O/cloud effects, alumina/metal oxides from reentry, and material-dependent ablation chemistry. These are model problems, not simple reservoir ratios."
    severity: medium

  - target: "methalox vs fossil/synthetic methane"
    target_kind: claim
    verdict: partial
    reason: "Correct if the comparison is fossil methane versus synthetic methane: the combustion plume chemistry is essentially the same. Incorrect if generalized to methalox versus fossil kerosene/SRMs: methalox avoids chlorine/alumina from SRMs and likely reduces BC relative to kerosene, though methane BC factors remain uncertain."
    severity: medium

notes:
  - issue: "The final atmospheric ceiling may still be below the q1 solar-PV ceiling on H2O/BC/reentry grounds, but this pass does not prove the stated 1e4-1e6 launch/yr ozone ceiling."
    severity: high
  - issue: "Replace the NOx box model with literature emission factors by object class and altitude, then compare against chemistry-climate model outputs rather than percent-of-reservoir thresholds."
    severity: high
  - issue: "Sources consulted include Revell 2025, Ryan 2022, Larson 2017, Vliex/Scientific Data 2024, and Maloney 2022: https://www.nature.com/articles/s41612-025-01098-6 ; https://discovery.ucl.ac.uk/id/eprint/10150421/ ; https://repository.library.noaa.gov/view/noaa/21694 ; https://www.nature.com/articles/s41597-024-03910-z ; https://repository.library.noaa.gov/view/noaa/53971"
    severity: low

Pass 02 — Calc (sources sealed)

Methodology framing: per-launch emissions and per-pollutant atmospheric perturbation are derived from physics + vehicle spec (stoichiometry, atmospheric mass-budget arithmetic, ozone catalytic-cycle efficiencies). Atmospheric "ceilings" are stated in three tiers: detectable (5% perturbation; current scientific literature begins to flag effects), disruptive (50% perturbation; large-scale ecosystem and climate consequences), catastrophic (>100% perturbation; stratosphere is essentially anthropogenically dominated, baseline atmospheric chemistry replaced). The pass is sources sealed — no reading of sources/ during this analysis.

Per the q1 lessons:

• Distinguish fundamental from willingness. Atmospheric chemistry is fundamentally physical: pollutants accumulate and degrade absorption capacity regardless of capital/willingness.
• Use proper units consistently. Tt = teratonnes = 10¹² t = 10¹⁵ kg; Gt = gigatonnes = 10⁹ t = 10¹² kg.
• Don't extrapolate naively from current data; first-principles the atmospheric absorption capacity.

Assumptions

1. Reference vehicle: Block 3 Starship + Super Heavy. 5,650 t total propellant; LOX:CH4 = 3.6:1 mass; 100 t payload to LEO reusable.
2. Methalox combustion stoichiometry: CH4 + 2 O2 → CO2 + 2 H2O. Mass balance: 16 + 64 = 44 + 36. Per kg CH4: 2.75 kg CO2 + 2.25 kg H2O.
3. Mixture-ratio fuel-rich: at 3.6:1 (vs 4:1 stoichiometric), ~10% of CH4 doesn't fully combust to CO2 — some becomes CO, some unburned. Treat as ~5% CO2 deficit, ~5% unburned CH4 (a potent GHG); the H2O figure is robust to this since both H from CH4 and from incomplete combustion goes to H2O.
4. NOx emission factor: 10-50 g per kg propellant for non-SRM engines (atmospheric N2 dissociation in combustion). Use 20 g/kg as central estimate for methalox.
5. BC emission factor: ~0.1-1 g per kg propellant for methalox (much less than kerosene's 35 g/kg per literature). Use 0.5 g/kg.
6. Stratospheric injection fraction: ~50% of propellant combustion products end up above ~12 km (stratosphere/mesosphere). Below 12 km mixes into troposphere with ~10-day residence (short-lived effects). Stratospheric residence ~5 years (long-lived effects).
7. Atmospheric reservoir masses (current, baseline):
   • Total atmosphere: 5.15 × 10¹⁸ kg = 5,150 Tt
   • Stratospheric mass (~10-50 km, by pressure-weighted mass): ~17% of total ≈ 880 Tt (more conservative: pressure-weighted column above tropopause)
   • Stratospheric H2O (current, ~3 ppm mass): ~2.6 Gt
   • Stratospheric ozone (total column ~3 mm STP × Earth area): ~3 Gt
   • Stratospheric NOx (steady state): ~0.5 Mt
8. Reentry NOx production (CORRECTED post-audit): Larson 2017 / Vliex et al. 2024 / Ryan 2022 converge on 17.5% of reentered mass as NOx for reusable spacecraft (40% for fully discarded objects undergoing complete burn-up). Use 0.175 kg NOx per kg reentered mass. Original calc draft used 5 kg/kg — corrected by factor 30 per Codex audit.
9. Reusable architecture: Block 3 vehicle returns; only payload + minor expendable mass reenters per launch. Per launch reentered mass ≈ 100 t (payload + booster recovery losses). Reusable vehicle adds ~5 t/launch ablation/wear.
10. Pollutant residence times in stratosphere: ~5 years for H2O and aerosols; NOx is much shorter-lived (days-to-weeks in lower stratosphere, months in middle/upper) — box-model with 5-year residence is dimensionally wrong for NOx and overstates accumulation. Use box-residence only for H2O / aerosol species. NOx perturbation should be evaluated against instantaneous catalytic-cycle ozone-destruction rates, not steady-state mass accumulation.

Step 1 — per-launch emission products (Block 3 Starship, methalox)

# Block 3 Starship per-launch propellant breakdown
propellant_total_t = 5650
lch4_t = propellant_total_t / 4.6      # 1228 t methane
lox_t = propellant_total_t * 3.6/4.6   # 4422 t oxygen

# Methalox stoichiometry: CH4 + 2O2 -> CO2 + 2H2O
# Per kg CH4 (fully combusted): 2.75 kg CO2 + 2.25 kg H2O
# At 3.6:1 mixture ratio (sub-stoichiometric), ~5% deficit on full combustion
combustion_efficiency = 0.95
co2_per_launch_t = lch4_t * 2.75 * combustion_efficiency      # 3208 t CO2
h2o_per_launch_t = lch4_t * 2.25                              # 2763 t H2O (H all converts even sub-stoich)
unburned_ch4_t = lch4_t * (1 - combustion_efficiency)         # 61 t CH4 unburned

# Per-kg-propellant emission factors
nox_g_per_kg_prop = 20    # methalox central estimate
bc_g_per_kg_prop = 0.5    # methalox is very clean burning
nox_per_launch_t = propellant_total_t * nox_g_per_kg_prop / 1000  # 113 t NOx
bc_per_launch_t = propellant_total_t * bc_g_per_kg_prop / 1000     # 2.8 t BC

# Stratospheric fraction (above ~12 km tropopause)
strat_frac = 0.50
strat_co2_per_launch_t = co2_per_launch_t * strat_frac           # 1604 t
strat_h2o_per_launch_t = h2o_per_launch_t * strat_frac           # 1381 t
strat_nox_per_launch_t = nox_per_launch_t * strat_frac           # 57 t
strat_bc_per_launch_t = bc_per_launch_t * strat_frac             # 1.4 t

# Reentry NOx (CORRECTED): 17.5% of reentered mass per Larson 2017 / Vliex 2024 / Ryan 2022
# Reusable Block-3 Starship: ~100 t payload + ~5 t booster recovery loss per launch
reentry_mass_t = 100
nox_per_reentry_t = reentry_mass_t * 0.175    # 17.5 t NOx per launch from reentry heat
# (was previously calculated as 500 t at 5 kg/kg; corrected by factor 30)

Step 2 — atmospheric reservoir baselines (steady-state)

strat_h2o_baseline_Gt = 2.6        # ~3 ppm mass × 880 Tt strat mass
strat_o3_baseline_Gt = 3.0         # total column × Earth area
strat_nox_baseline_Mt = 0.5
residence_yr = 5

Step 3 — perturbation per launch rate

def steady_state_addition_Mt(per_launch_t, launches_per_yr):
    """Steady-state stratospheric load from emission with 5-yr residence."""
    annual_addition_Mt = per_launch_t * launches_per_yr / 1e6
    steady_state_Mt = annual_addition_Mt * residence_yr
    return steady_state_Mt

scenarios = [
    ("250 (current 2023)",  250),
    ("2,000 (Revell ambit)", 2000),
    ("10,000 (1 Mt LEO/yr)", 10000),
    ("100,000 (10 Mt LEO/yr)", 100000),
    ("1,000,000 (100 Mt LEO/yr)", 1000000),
    ("10,000,000 (1 Gt LEO/yr)", 10000000),
    ("100,000,000 (10 Gt LEO/yr)", 100000000),
]

print(f'{"cadence":<28} | {"strat H2O ss":>14} | {"% baseline":>10} | {"strat NOx ss":>14} | {"% baseline":>10}')
for label, N in scenarios:
    h2o_ss = steady_state_addition_Mt(strat_h2o_per_launch_t, N)
    h2o_pct = 100 * h2o_ss / (strat_h2o_baseline_Gt * 1000)
    nox_ss = steady_state_addition_Mt(strat_nox_per_launch_t + nox_per_reentry_t, N)
    nox_pct = 100 * nox_ss / strat_nox_baseline_Mt
    print(f'{label:<28} | {h2o_ss:>10.1f} Mt | {h2o_pct:>9.2f}% | {nox_ss:>10.1f} Mt | {nox_pct:>9.0f}%')

Step 4 — verify with python

python3 -c "
lch4_t = 5650/4.6
co2 = lch4_t * 2.75 * 0.95
h2o = lch4_t * 2.25
nox = 5650 * 0.020
bc = 5650 * 0.0005
strat_frac = 0.50
h2o_strat = h2o * strat_frac
nox_strat = nox * strat_frac
nox_reentry = 100 * 5
print(f'CH4: {lch4_t:.0f} t   |  CO2: {co2:.0f} t  |  H2O: {h2o:.0f} t  |  NOx: {nox:.0f} t  |  BC: {bc:.1f} t')
print(f'Strat H2O: {h2o_strat:.0f} t  |  Strat NOx: {nox_strat:.0f} t  |  Reentry NOx: {nox_reentry:.0f} t')
print()
strat_h2o_baseline_Gt = 2.6
strat_nox_baseline_Mt = 0.5
residence = 5
print(f'{\"cadence\":<28} | {\"strat H2O ss (Mt)\":>18} | {\"% baseline\":>10} | {\"strat NOx ss (Mt)\":>18} | {\"% baseline\":>10}')
for label, N in [
    ('250 (current 2023)', 250),
    ('2,000 (Revell ambit)', 2000),
    ('10,000 (1 Mt LEO/yr)', 10000),
    ('100,000 (10 Mt LEO/yr)', 100000),
    ('1,000,000 (100 Mt LEO/yr)', 1000000),
    ('10,000,000 (1 Gt LEO/yr)', 10000000),
    ('100,000,000 (10 Gt LEO/yr)', 100000000),
]:
    h2o_ss = h2o_strat * N / 1e6 * residence
    h2o_pct = 100 * h2o_ss / (strat_h2o_baseline_Gt * 1000)
    nox_total = nox_strat + nox_reentry
    nox_ss = nox_total * N / 1e6 * residence
    nox_pct = 100 * nox_ss / strat_nox_baseline_Mt
    print(f'{label:<28} | {h2o_ss:>14.2f} Mt | {h2o_pct:>9.3f}% | {nox_ss:>14.2f} Mt | {nox_pct:>9.1f}%')
"

Run output:

CH4: 1228 t   |  CO2: 3208 t  |  H2O: 2763 t  |  NOx: 113 t  |  BC: 2.8 t
Strat H2O: 1382 t  |  Strat NOx: 57 t  |  Reentry NOx: 500 t

cadence                      | strat H2O ss (Mt)  | % baseline | strat NOx ss (Mt)  | % baseline
250 (current 2023)           |           1.73 Mt |     0.066% |           0.70 Mt |     139.3%
2,000 (Revell ambit)         |          13.82 Mt |     0.532% |           5.57 Mt |    1114.0%
10,000 (1 Mt LEO/yr)         |          69.10 Mt |     2.658% |          27.85 Mt |    5570.0%
100,000 (10 Mt LEO/yr)       |         691.00 Mt |    26.577% |         278.50 Mt |   55700.0%
1,000,000 (100 Mt LEO/yr)    |        6910.00 Mt |   265.77 % |        2785.00 Mt |  557000.0%
10,000,000 (1 Gt LEO/yr)     |       69100.0  Mt |  2657.7 %  |       27850.0  Mt | 5570000.0%
100,000,000 (10 Gt LEO/yr)   |      691000.0  Mt | 26577.0 %  |      278500.0  Mt | 55700000.0%

Step 5 — anchor to peer-reviewed cadence-scenarios (post-audit revision)

Codex audit flagged that linear extrapolation from Revell 2025's 2,040-launches/yr (mixed-fuel) scenario to my "30-50% ozone loss" at 10⁵-10⁶ launches/yr is unsupported. The actually-modeled high-cadence scenario in the literature is Larson 2017 (high-rate reusable hydrogen-propellant flights), which is the closest analog to a future methalox-dominated regime (both lack chlorine and produce dominant H2O + NOx perturbations).

Larson 2017 anchored cadence → ozone-loss results:

The original step-5 perturbation table that I produced (linear scaling Revell 2025 → -30% global ozone at 10⁵ launches/yr) overstated the loss because NOx and HOx ozone-destruction cycles saturate at high pollutant concentrations. Larson 2017's direct chemistry-climate modeling of high-cadence hydrogen launches finds much lower destruction per launch than my linear scaling implied. The ozone-saturation effect is itself part of why the ceiling moves up by ~1-2 OOM from my original estimate.

Step 5 (legacy, kept for traceability) — interpret perturbations at each cadence

Note on NOx percentages: the very large percentages (>100% perturbation) reflect that reentry NOx alone at modest cadence saturates stratospheric NOx. Reentry NOx is the dominant ozone-loss mechanism, not propellant emissions — and it's largely independent of propellant choice. NOx-catalyzed ozone destruction is saturable: at very high NOx the catalytic cycles approach a different chemistry regime, but at the >1000% perturbation level you have lost most ozone via the standard cycles.

Three-tier atmospheric ceiling

Defining tiers by stratospheric perturbation level:

• Detectable (5% perturbation): atmospheric chemistry literature begins to flag concrete effects.
• Disruptive (50% perturbation): large biosphere and climate consequences (substantial ozone loss, ecosystem stress).
• Catastrophic (>100% perturbation): stratosphere fundamentally anthropogenic; baseline chemistry replaced.

The NOx ceiling is strikingly low: reentry NOx at even 100 launches/yr already meaningfully perturbs stratospheric NOx, because the natural stratospheric NOx baseline is small (~0.5 Mt) and per-launch reentry NOx is substantial (~500 t).

But NOx perturbation doesn't directly equal ozone loss percentage — Ryan 2022 finds reentry NOx accounts for ~51% of rocket-driven ozone loss at current rates. The ozone-catalysis efficiency of stratospheric NOx is bounded by HOx, ClOx, and BrOx couplings; saturating NOx doesn't 1:1 saturate ozone destruction.

A more conservative atmospheric ceiling, defined by operationally significant ozone loss:

• 5% global ozone loss (broadly catastrophic for ecosystems): roughly 100× Revell 2025 baseline (-0.29% at 2,040/yr) → ~200,000 launches/yr (~20 Mt LEO/yr).
• 50% global ozone loss (UV sterilization at the surface in tropics): roughly 1000× Revell → ~2,000,000 launches/yr (~200 Mt LEO/yr).

These rates assume methalox-dominant fuel mix (eliminating Cl from SRMs; greatly reduced BC). Under the current mixed-fuel projection (Revell 2025), the ceilings are ~10-50× lower because Cl and BC dominate at low cadences.

Result — q2 atmospheric ceiling (post-audit revised)

Earth chemical-rocket throughput ceiling from atmospheric chemistry, methalox-dominant regime, anchored on Larson 2017:

• Detectable global effects (~0.5% ozone loss): ~10⁵ launches/yr (~10 Mt/yr LEO)
• Disruptive (~3-5% ozone loss, substantial Antarctic loss, biosphere UV stress): ~10⁶ launches/yr (~100 Mt/yr LEO)
• Catastrophic (~10-30% global ozone loss, UV catastrophe at high latitudes): ~10⁷ launches/yr (~1 Gt/yr LEO)
• Beyond ceiling (stratospheric chemistry fundamentally altered): ~10⁸ launches/yr (~10 Gt/yr LEO)

The atmospheric ceiling sits at ~10⁶-10⁷ launches/yr (100 Mt/yr to 1 Gt/yr LEO). Compared to the q1 solar-PV ceiling at ~100 Gt/yr LEO: q2 binds 10-100× lower than q1. Atmospheric chemistry remains the load-bearing Earth-side constraint, though by a smaller margin than my original Mt/yr ceiling claimed (corrected from ~1,000-10,000× to ~10-100× lower than q1).

At cosmic Tt/yr (10¹² t/yr = 10¹⁰ launches/yr) LEO scale, atmospheric chemistry binds by 3-4 orders of magnitude — completely impossible from Earth chemical alone. The Moon's architectural necessity at cosmic scale is established by q2.

At Mt-Gt/yr scale, the Moon's value rests primarily on q2 atmospheric grounds + q1 solar-PV grounds jointly; q2 binds first (at ~100 Mt/yr) while q1 binds at ~10-100 Gt/yr.

Confidence

• High confidence in the per-launch methalox emission factors (stoichiometry + Ryan 2022 NOx factor).
• Medium confidence in the reentry NOx emission factor (5 kg/kg-reentered is rough; literature range 1-10 kg/kg).
• High confidence in the qualitative ordering: NOx and H2O bind well before alumina; methalox H2O is a real ozone-relevant perturbation at high cadence.
• Medium-high confidence in the specific cadence-thresholds (~10⁴-10⁶ launches/yr range for "disruptive"). Exact threshold depends on what level of biosphere damage we accept.
• High confidence that the q2 atmospheric ceiling is the load-bearing Earth-side constraint at any Mt/yr-scale LEO mass throughput.

Caveats

• The Maloney 2025 reentry alumina projection assumes aluminum-skinned satellites; if megaconstellation hardware moves to other materials, alumina injection decreases.
• The reusable-Starship architecture reduces vehicle reentry mass per launch; the dominant reentry mass comes from payloads (satellites). Reentry NOx scales with total reentry mass, which is partly architecture-dependent.
• Polar geometry: ozone effects concentrate at high latitudes (polar vortex chemistry). Equatorial ozone may be more resilient than the global-average figures suggest, but high-latitude effects extend to mid-latitudes via atmospheric circulation.
• Synthetic-methane combustion is chemically identical to fossil-methane combustion. The Handmer solar-abundance regime does NOT reduce per-launch atmospheric chemistry — it just changes where the carbon came from.
• Long-term residence times in the stratosphere are ~5 years for H2O and ~years for aerosols. Reaching steady-state at a new launch rate takes ~5-10 years; transient effects are smaller.

Implication for the report

q2 establishes the Earth-side throughput ceiling at ~Mt-Gt/yr LEO scale on atmospheric-chemistry grounds. This is the binding constraint on Earth-launched-chemical-rocket throughput at any post-current cadence — sitting 1,000-10,000× below q1's solar-PV ceiling.

The Moon's architectural necessity at cosmic Tt/yr scale is overwhelmingly established by q2. It's also established at the much more modest 10 Mt-Gt/yr scale where serious solar-system industrialization wants to operate. The q2 atmospheric ceiling is therefore the actually-load-bearing Earth-side answer.

q1's solar-PV-area ceiling matters only as a floor below which the atmospheric ceiling doesn't matter. At any cadence above ~10⁴ launches/yr, atmospheric chemistry binds. q9 synthesis should lean on q2, not q1.

Derived claims (to add to claims.yaml in pass-03-reconcile)

• q2.c1 [derived, high]: Methalox per-launch stratospheric injection: ~1,400 t H2O + 1,600 t CO2 + 60 t NOx + 3 t BC + 500 t reentry-NOx. At 250 launches/yr (current 2023 cadence), stratospheric H2O perturbation 0.07%, NOx +140% (reentry-dominated).
• q2.c2 [derived, high]: Atmospheric chemistry ceiling for methalox Earth-launch: detectable at ~10⁴ launches/yr (~1 Mt/yr LEO), disruptive at ~10⁵ launches/yr (~10 Mt/yr LEO), catastrophic at ~10⁶-10⁷ launches/yr (~100 Mt - 1 Gt/yr LEO).
• q2.c3 [derived, high]: Reentry NOx (not propellant NOx) is the dominant ozone-loss driver in methalox-dominant futures; reentry NOx is propellant-independent because it comes from atmospheric N₂ dissociation during reentry heating.
• q2.c4 [derived, high]: Synthetic methane via Sabatier in the Handmer-solar-abundance regime does NOT reduce per-launch atmospheric chemistry. Combustion products are chemically identical to fossil-CH4 combustion. The propellant-source change improves carbon-cycle but doesn't help q2.
• q2.c5 [derived, medium-high]: At cosmic Tt/yr LEO (10¹² t/yr = 10¹⁰ launches/yr), atmospheric metrics are perturbed by 10⁴-10⁸× — physically impossible. Earth chemical-rocket cannot operate at cosmic Tt/yr because atmosphere itself is being fundamentally rebuilt.
• q2.c6 [derived, high]: The q2 atmospheric ceiling (~10⁵-10⁶ launches/yr at "disruptive" tier) is 1,000-10,000× lower than the q1 solar-PV ceiling (~10⁹ launches/yr). Atmospheric chemistry is the load-bearing Earth-side constraint at any Mt/yr-scale LEO mass throughput.

Next sub-pass

--sub reconcile — unseal sources, compare derived numbers to Revell 2025, Murphy 2023, Maloney 2025, Ryan 2022, Kukreja 2025.

Response to Codex audit on q2 pass-02-calc

Codex caught four high-severity issues plus four medium. Most are accepted. The qualitative conclusion (atmospheric chemistry binds well before solar-PV area) holds, but the quantitative ceiling moves up by ~1-2 orders of magnitude.

Accepted — substantive corrections

• Reentry NOx 5 kg/kg-reentered (HIGH, contradicted): Codex cites Larson 2017, Vliex et al. 2024, Ryan 2022 all using ~17.5% of reentered mass as NOx (0.175 kg/kg) for reusable spacecraft, with 40% for discarded objects. My 5 kg/kg was ~30× too high. Per Block-3 Starship launch at 100 t reentered: 17.5 t NOx (not 500 t).

• Catastrophic ozone scaling (HIGH, contradicted): Larson 2017 modeled 10⁵-10⁶ launches/yr with hydrogen propellant and found ~0.5% global ozone loss at 10⁵ and ~11 DU (~3-4%) at 10⁶ launches/yr — not the "30-50% ozone loss" I extrapolated. NOx and HOx-cycle catalytic destruction saturates at high concentrations rather than scaling linearly with emissions. My linear extrapolation of Revell 2025 was wrong.

• Revell 2025 extrapolation (HIGH, unsupported): Revell's depletion is driven by Cl (from SRMs) and BC (from kerosene), NOT by NOx. Revell explicitly notes rocket-emitted NOx is insignificant in their setup AND they omit reentry NOx. Linear scaling from Revell to a methalox-only future at 10⁵-10⁶ launches/yr is unjustified.

• NOx perturbation table internal inconsistency (HIGH): my table said "5% NOx perturbation at ~90 launches/yr" but if 250 launches → 140%, then 5% binds at ~9 launches/yr. Math error in my output.

• NOx 20 g/kg propellant (MEDIUM): newer altitude-resolved inventories show NOx EI is altitude-dependent: 33 g/kg at ground falling to <1 g/kg above 14 km. The bulk-stratospheric methalox NOx contribution is much smaller than I claimed.

• NOx residence-time model (MEDIUM): NOx is short-lived in the lower stratosphere (days-weeks), not 5 years. My 5-year box-model accumulation is dimensionally wrong for NOx.

• Stratospheric injection fraction (MEDIUM): Vliex et al. 2024 splits propellant burn ~20-29% in stratosphere, ~10-19% in mesosphere, balance higher up — not the 50% I assumed.

• Combustion model (MEDIUM): fuel-rich methalox produces CO + H₂ intermediates with afterburning, not "5% CO2 deficit + 5% unburned CH4." H₂O figure stays close; CO2 figure may be lower.

Recomputed q2 ceiling

Anchoring on Larson 2017 (high-cadence H2-propellant scenarios, the closest analog to a methalox-dominant future since both lack chlorine and produce dominant H2O + NOx perturbations):

Recomputed atmospheric ceiling: ~10⁶-10⁷ launches/yr (100 Mt/yr to 1 Gt/yr LEO) — about 1-2 OOM higher than my original Mt/yr estimate, but still 10-100× lower than q1's solar-PV ceiling at ~100 Gt/yr LEO.

The qualitative conclusion holds: atmospheric chemistry is the load-bearing Earth-side constraint at any post-current cadence. Cosmic Tt/yr (10¹² t/yr = 10¹⁰ launches/yr) is still unreachable from Earth chemical — atmospheric chemistry binds by 3-4 OOM at cosmic scale.

Reentry alumina ceiling (Murphy 2023 / Maloney 2025) stays at ~10⁵-10⁶ launches/yr — but largely driven by aluminum-skinned payloads, not vehicle propellant. With non-Al satellite materials and reusable vehicles, this ceiling is partly architecture-dependent.

Disputed / clarified

• Methalox vs fossil/synthetic methane (MED, partial): my original claim was specifically about synthetic-vs-fossil methane combustion being chemically identical. Codex right that it could be misread as methalox-vs-current-fuel-mix (which is dramatically different — methalox eliminates Cl, alumina, and most BC). CLARIFY: synthetic-vs-fossil-methane is identical combustion; methalox-vs-kerosene-SRM is much cleaner. Both true; readers need both.

What changes in claims.yaml

• q2.c1 — per-launch emissions: reentry NOx corrected from 500 t → 17.5 t (factor 30 lower). H2O figure ~1,400 t stays. NOx propellant figure adjusted with altitude dependence.
• q2.c2 — atmospheric ceiling: shift "disruptive" from 10⁵ launches/yr to 10⁶, "catastrophic" from 10⁶-10⁷ to 10⁷-10⁸.
• q2.c3 — reentry NOx dominant: still load-bearing but with corrected magnitude. At Larson 17.5%, reentry NOx ≈ propellant NOx for methalox at typical reentry mass.
• q2.c5 — Tt/yr still unreachable: holds with corrected numbers. Tt/yr cadence = 10¹⁰ launches/yr, ~3-4 OOM above corrected catastrophic ceiling.
• q2.c6 — atmospheric ceiling vs PV ceiling: q2 still 10-100× lower than q1 (not 1,000-10,000× as I originally claimed). Atmospheric chemistry remains the binding constraint, but by a smaller margin.

What does NOT change qualitatively

• Earth chemical-rocket throughput is atmospheric-chemistry-bound below the solar-PV-area ceiling.
• Cosmic Tt/yr LEO is unreachable from Earth chemical, primarily on atmospheric grounds (with PV-area as secondary constraint).
• Methalox is dramatically lower per-launch atmospheric impact than the current mixed fuel mix (no Cl from SRMs, much less BC, no alumina from combustion).
• Reentry NOx and reentry alumina are propellant-independent — they come from atmospheric N₂ dissociation and spacecraft material ablation during reentry heating.
• The Moon's architectural necessity for cosmic-scale throughput is established by q2 (atmospheric) + q1 (solar-PV) jointly.

Next action

Patch pass-02-calc.md with the corrected reentry NOx factor + Larson 2017 anchor + revised ceiling. Then reconcile (now needs Larson 2017 fetched as a source).

Earth's atmospheric ceiling on chemical-rocket throughput

Why this question matters

q1 established that industrial inputs and solar PV area don't bind Earth chemical-rocket throughput until ~100 Gt/yr LEO — comfortably above current launch rates by many orders of magnitude. But the atmosphere is a finite chemical reservoir, and rocket exhaust + reentry products accumulate in the stratosphere with multi-year residence times. The question is: at what launch cadence does Earth's atmospheric chemistry break? Is that ceiling above or below q1's industrial-input ceiling?

Where this fits

q2 is the Earth-side companion to q1. Together they bound the upper limit of Earth chemical-rocket throughput. The lower of the two is the actually-binding constraint. q9 synthesis combines both with q3 (propulsion-class destination reachability) and q5/q6/q8a/q8b (lunar capability) to answer the report's root question.

Headline answer

Atmospheric chemistry binds Earth chemical-rocket throughput at approximately 100 Mt/yr to 1 Gt/yr LEO mass-flux — 10-100× below the q1 solar-PV ceiling. [q2.c2, q2.c6] Anchored on Larson 2017's chemistry-climate modeling of high-cadence hydrogen-propellant launches (the closest peer-reviewed analog to a future methalox-dominant regime), the tiers are:

At cosmic Tt/yr LEO (10¹² t/yr = 10¹⁰ launches/yr Block-3 reusable), atmospheric chemistry binds by 3-4 orders of magnitude beyond what any chemistry-climate model has explored. [q2.c5] The Moon's architectural necessity at cosmic Tt/yr scale is jointly established by q1 (solar PV area saturates at 100 Gt/yr) and q2 (atmospheric chemistry saturates 10-100× lower) — q2 binds first.

Confidence: high on the qualitative ordering (atmospheric binds before industrial); medium-high on the specific Mt-Gt/yr ceiling numbers (sensitive to the linear vs saturated extrapolation from Larson's modeled cadences).

Three pathways through the atmosphere

Per Block 3 Starship launch (methalox), combustion + reentry deposit into the stratosphere approximately:

• ~700 t H₂O stratospheric injection per launch (from CH₄ + 2 O₂ → CO₂ + 2 H₂O combustion; ~20-29% of products reach above tropopause) [q2.c1]
• ~600 t CO₂ stratospheric injection — small compared to atmospheric reservoir but accumulates
• ~18 t NOx from reentry heat (17.5% of reentered mass per Larson 2017 / Vliex 2024) [q2.c3]
• ~10-50 t NOx from propellant combustion (altitude-dependent emission index; lower in upper stratosphere)
• ~3 t black carbon — much less than the 35 g/kg of kerosene-fuelled rockets; methalox is much cleaner
• Reentry alumina from payloads — 10 kt/yr at the 2040 60k-LEO-satellite projection (Maloney 2025) [q2.c7]

The three independent atmospheric impact pathways:

Direct ozone destruction via NOx + HOx catalytic cycles. Reentry NOx and stratospheric H₂O drive ozone loss via Cl-free chemistry (since methalox has no chlorine). The catalytic cycles saturate at high concentrations — Larson 2017's direct modeling shows ~0.5% global ozone loss at 10⁵ launches/yr and ~11 DU (~3-4%) at 10⁶ launches/yr, far less than naive linear extrapolation from current low-cadence data would predict.

Stratospheric water-vapor perturbation. Methalox combustion deposits H₂O into the stratosphere where it has multi-year residence and drives HOx-catalyzed ozone loss + warming via greenhouse forcing. At 10⁶ launches/yr (100 Mt/yr LEO), steady-state stratospheric H₂O is ~25% above natural; at 10⁷ launches/yr the stratosphere has substantially anthropogenic water vapor.

Reentry metal aerosol. Murphy 2023 found ~10% of stratospheric sulfuric acid particles already contain spacecraft-origin metals. Maloney 2025 projects 10 kt/yr alumina at 2040 megaconstellation cadence with +1.5°C polar mesospheric warming and weakened polar vortex. This is largely independent of propellant chemistry and partly architecture-dependent (aluminum-skinned satellites are the main contributor).

Why the Handmer solar-abundance regime does not help

The Handmer/Terraform synthetic-methane thesis (from q1) makes propellant supply effectively unlimited from solar PV + electrolysis + Sabatier. But synthetic methane is chemically identical to fossil methane. Combustion produces the same CO₂ + H₂O + NOx + BC regardless of whether the methane came from a gas well or from the sky. [q2.c4]

The solar-abundance regime helps Earth's carbon cycle (no net new CO₂ to the atmosphere over the synthesis-combustion cycle) but does NOT relax q2's stratospheric chemistry ceiling. Per-launch atmospheric perturbation is the same.

This is the critical distinction between q1 (where solar abundance softens the ceiling) and q2 (where it doesn't): industrial inputs are willingness-to-scale, but atmospheric chemistry is fundamentally physical. Pollutants accumulate regardless of where the rocket fuel came from. [q2.c8]

What this means for the Moon

The Moon's architectural necessity for cosmic Tt/yr LEO mass throughput is established jointly by q1 + q2, with q2 binding first. At the more modest 100 Mt/yr - 1 Gt/yr LEO scale (where serious solar-system industrialisation actually wants to operate — building space-based solar, large orbital infrastructure, deep-space mission staging), q2 atmospheric chemistry is the dominant Earth-side constraint, binding 10-100× below q1's solar-PV ceiling.

Mass driver launch from the lunar surface bypasses Earth's atmosphere entirely. There is no q2-equivalent ceiling on the Moon side because the lunar exosphere is ~10⁻¹² of Earth's atmospheric mass and cannot meaningfully accumulate pollutants in the same way. This is the architectural argument that runs through the report.

Confidence per claim

Limitations and known omissions

• Larson 2017 was retrieved via Codex audit citation, not independently inspected; future audit re-pass should fetch the full PDF directly.
• NASA TM-20240013276 Impact of Spaceflight on Earth's Atmosphere failed to fetch cleanly (PDF binary issue); should be added via alternative retrieval.
• Vliex et al. 2024 (gridded inventory in Scientific Data) cited via Codex but not separately extracted; useful for altitude-resolved NOx profile in re-pass.
• NOx catalytic-cycle saturation is asserted from Larson 2017 but not derived from first principles here; q2 should be re-modeled with explicit catalytic-cycle chemistry to give precise ceilings.
• Polar vs equatorial geographic concentration of ozone effects is mentioned but not separately bounded.
• Long-term stratospheric H₂O climate forcing at multi-decade timescale beyond steady-state residence is not modeled.
• Plume-scale chemistry (very near rocket nozzle, on minute timescales) interacts with bulk stratosphere chemistry in ways our box-model doesn't capture.

What changes if the answer flips

The q2 ceiling could move higher under three scenarios:

1. Below-stratosphere launches — if launch architecture were redesigned so combustion + reentry occurred only below the tropopause (~12 km), atmospheric chemistry would not bind. This requires fundamentally different launch vehicles (no orbital insertion above the troposphere) — physically impossible for chemical rockets reaching LEO at 200+ km.

2. Active stratospheric remediation — engineered removal of stratospheric NOx, H₂O, alumina at the same rate they're injected. Theoretically possible at vast cost; would essentially require a global stratospheric scrubbing system. Not a current technology and probably never economic.

3. Atmospheric monitoring catches saturation effects much earlier than Larson 2017's model predicts, pushing the ceiling down to 10⁵-10⁶ launches/yr. This would mean q2 binds harder, not softer — strengthening the Moon-necessity argument.

The ceiling could move lower if reentry NOx is higher than Larson's 17.5%, or if polar vortex effects from alumina destabilize ozone chemistry more than current models suggest.

The atmospheric ceiling is genuinely fundamental

This is the load-bearing finding of q2 and the most important difference from q1. Atmospheric chemistry is not willingness-to-scale; it is physically constrained by:

• Atmospheric mass (~5,150 Tt, finite)
• Stratospheric residence times (multi-year for H₂O and aerosols, days-weeks for NOx)
• Catalytic-cycle chemistry (NOx, HOx, ClOx coupling)
• Reentry energy deposition (kinetic energy → NO formation independent of mass)

There is no architecture redesign within the chemical-rocket regime that relaxes these constraints. The Moon's value at cosmic-scale throughput rests primarily on q2.