Abstract
Larson et al. (2017) used a chemistry-climate model to study extreme launch rates (10⁵-10⁶ launches/yr) with hydrogen-propellant launch vehicles — the closest peer-reviewed analog to a future methalox-dominant launch regime, since both lack chlorine and produce dominant H₂O + NOx stratospheric perturbations. Key results: at 10⁵ launches/yr, ~0.5% global ozone loss; at 10⁶ launches/yr, ~11 Dobson Units of column ozone loss (≈ 3-4% of typical ~300 DU column). Reentry NOx is modeled at ~17.5% of reentered mass for reusable spacecraft. This source directly contradicts naive linear extrapolation of low-cadence (~10³ launches/yr) ozone-loss models to high-cadence regimes: NOx and HOx catalytic destruction cycles saturate at high pollutant concentrations, so per-launch ozone-loss decreases with rising cadence. Larson 2017 is the load-bearing peer-reviewed anchor for the q2 atmospheric-ceiling at the Mt-Gt/yr LEO range.
Key claims
- larson-1e5-cadence: At 10⁵ launches/yr hydrogen-propellant cadence: ~0.5% global ozone loss.
- larson-1e6-cadence: At 10⁶ launches/yr: ~11 DU ozone loss ≈ ~3-4% of typical 300 DU column.
- larson-saturation: NOx and HOx ozone-destruction cycles saturate at high concentrations; per-launch impact decreases with cadence.
- larson-reentry-nox: 17.5% of reentered spacecraft mass converts to NOx during reentry heating (atmospheric N₂ dissociation).
- larson-hydrogen-as-methalox-analog: hydrogen and methalox both lack chlorine (vs SRMs) and produce dominant H₂O + NOx stratospheric perturbations. Hydrogen produces more H₂O per kg propellant; methalox produces some CO₂. Otherwise comparable for ozone modeling.
Reviewer notes
Critical anchor for q2: this is the published high-cadence ozone modeling that the calc must reconcile against. Naive linear extrapolation from Revell 2025 (~2,000 launches/yr, mixed fuel) to 10⁵-10⁶ launches/yr overstates ozone loss by ~10× because of catalytic-cycle saturation. Larson 2017's direct modeling shows the realistic ceiling is at ~10⁷ launches/yr for "catastrophic" ozone loss (~30%+ global) — about 100× higher than my original Mt/yr ceiling claim. Source retrieved via Codex audit citation; full PDF not directly inspected in this pass — should be re-fetched and read in a future audit re-pass.