Task 045: Propellant Budget Analysis (Tsiolkovsky Rocket Equation)

Status: DONE

Description

Add propellant mass analysis using the Tsiolkovsky rocket equation to evaluate whether D-He³ fusion propulsion can realistically deliver the ΔV values computed across all 5 episodes.

Design (Codex-reviewed)

• Codex confirmed function set, recommended adding initial_mass helper and thrust-power checks
• Isp range 10⁵–10⁶ s confirmed as reasonable (cited NASA NTRS Longshot, Daedalus studies)
• Recommended cumulative sequential mass propagation across episodes
• Noted Tsiolkovsky as ideal lower bound (no gravity losses)

Changes Made

1. Rust Core (crates/solar-line-core/src/orbits.rs)

New functions:

• exhaust_velocity(isp_s) — Isp (s) → exhaust velocity (km/s) via g₀
• mass_ratio(delta_v, ve) — Tsiolkovsky mass ratio exp(ΔV/vₑ)
• propellant_fraction(delta_v, ve) — 1 - 1/mass_ratio
• required_propellant_mass(dry_mass_kg, delta_v, ve) — propellant mass (kg)
• initial_mass(dry_mass_kg, delta_v, ve) — pre-burn mass (kg)
• mass_flow_rate(thrust_n, ve) — ṁ = F/vₑ (kg/s)
• jet_power(thrust_n, ve) — P_jet = ½Fvₑ (W)
• G0_M_S2 constant added to constants.rs
• 15 new tests (chemical, fusion, overflow, Kestrel EP01 validation)

2. WASM Bindings (crates/solar-line-wasm/src/lib.rs)

• 7 new wasm_bindgen functions (flat f64 API, matching existing pattern)
• 7 new tests

3. Cross-Episode Summary (reports/data/summary/cross-episode.json)

New section: "推進剤収支（ツィオルコフスキー方程式による検証）"

• Isp sensitivity analysis: 10⁵, 5×10⁵, 10⁶ s
• Per-transfer propellant fractions for EP01, EP03, EP04, EP05
• Cumulative mass propagation (300t dry → 11,873t at Mars departure @ Isp 10⁶ s)
• Enceladus refueling hypothesis
• Thrust-power consistency: 48.1 TW @ Isp 10⁶ s
• Comparison table (Isp sensitivity)
• Updated 総合評価 with propellant budget findings
• Key finding: 48,000t公称値 is consistent as "満載時最大質量" (loaded maximum mass)

4. Test Counts

• Rust core: 80 tests (was 65, +15 new)
• WASM: 21 tests (was 14, +7 new)
• TypeScript: 831 tests (unchanged)
• Total: 932 tests (was 910, +22 new), 0 failures

Files Modified

• crates/solar-line-core/src/constants.rs — G0_M_S2 constant
• crates/solar-line-core/src/orbits.rs — 7 new functions + 15 tests
• crates/solar-line-core/src/lib.rs — re-exports
• crates/solar-line-wasm/src/lib.rs — 7 WASM bindings + 7 tests
• reports/data/summary/cross-episode.json — new section + updated 総合評価