Part of epic #412 (PRD-031 / RFC-033 §6). Surfaced while adding flagship profiles (commit dac7dc98).
Problem
The ascent integrator steers with a fixed open-loop pitch table. It reaches a genuine orbit only when that table happens to place the vehicle horizontal at apoapsis at circular speed (falcon-9, titan-ii-glv). Higher-energy stacks (saturn-v, saturn-ib, proton-k — incl. the already-shipped saturn-v) loft and trip the orbit gate on the way down → a suborbital lob, not an orbit. Low-TWR cryo upper stages (atlas-v Centaur) can't circularise in one continuous burn at all. Per-vehicle hand-tuning is fragile (payload-sensitive) and doesn't scale.
Staging mass bookkeeping is correct (spent-stage dry mass IS jettisoned) — this is a guidance problem, not a dead-mass problem.
Tracks
Track 1 — closed-loop guidance (this slice)
Replace the open-loop pitch table with a feedback steering law (linear-tangent / PEG-lite): each step, steer to null the error toward target-altitude + zero vertical velocity at circular speed, cut off (SECO) on target. Any adequately-powered serial stack then reaches a genuine orbit with no per-vehicle tuning; self-corrects for payload.
- Keeps the pitch table as the in-atmosphere ascent (gravity turn), hands to closed-loop once above Max-Q / the atmosphere.
- Promotes saturn-v, saturn-ib, proton-k into the GENUINE_ORBIT guard (src/lib/orbital/flagship-profiles.test.ts) and fixes the shipped saturn-v lob.
Track 2 — coast + restart (follow-on)
Model an engine-off coast to apoapsis then a relight/circularisation burn, for low-TWR cryo upper stages. Unlocks atlas-v (Centaur), and Delta IV / Titan III/IV upper stages (#414).
Track 3 — parallel-boost stage (follow-on)
A "stage 0" that burns in parallel with the core for the first ~1–2 min then drops. Unlocks strap-on vehicles: delta-ii (9 GEM-40), vostok-k / soyuz (4 boosters), ariane-5 (2 EAP), h-iia (SRB-A), atlas-lv-3b.
Done when
- Track 1 lands with tests; GENUINE_ORBIT list expanded; RFC-033 §6 updated with the guidance design.
- Tracks 2/3 scoped as their own slices.
Part of epic #412 (PRD-031 / RFC-033 §6). Surfaced while adding flagship profiles (commit dac7dc98).
Problem
The ascent integrator steers with a fixed open-loop pitch table. It reaches a genuine orbit only when that table happens to place the vehicle horizontal at apoapsis at circular speed (falcon-9, titan-ii-glv). Higher-energy stacks (saturn-v, saturn-ib, proton-k — incl. the already-shipped saturn-v) loft and trip the orbit gate on the way down → a suborbital lob, not an orbit. Low-TWR cryo upper stages (atlas-v Centaur) can't circularise in one continuous burn at all. Per-vehicle hand-tuning is fragile (payload-sensitive) and doesn't scale.
Staging mass bookkeeping is correct (spent-stage dry mass IS jettisoned) — this is a guidance problem, not a dead-mass problem.
Tracks
Track 1 — closed-loop guidance (this slice)
Replace the open-loop pitch table with a feedback steering law (linear-tangent / PEG-lite): each step, steer to null the error toward target-altitude + zero vertical velocity at circular speed, cut off (SECO) on target. Any adequately-powered serial stack then reaches a genuine orbit with no per-vehicle tuning; self-corrects for payload.
Track 2 — coast + restart (follow-on)
Model an engine-off coast to apoapsis then a relight/circularisation burn, for low-TWR cryo upper stages. Unlocks atlas-v (Centaur), and Delta IV / Titan III/IV upper stages (#414).
Track 3 — parallel-boost stage (follow-on)
A "stage 0" that burns in parallel with the core for the first ~1–2 min then drops. Unlocks strap-on vehicles: delta-ii (9 GEM-40), vostok-k / soyuz (4 boosters), ariane-5 (2 EAP), h-iia (SRB-A), atlas-lv-3b.
Done when