Launch — powered-ascent act of /fly (Scene 0) — epic (PRD-031 / RFC-033)

[chipi]

PRD: docs/prd/PRD-031.md · RFC: docs/rfc/RFC-033.md · target v2.x

Prepend a powered-ascent act to /fly: the mission timeline extends to one continuous, scrubbable pad → orbit → cruise → arrival arc. Today launch is a zero-duration dot and the sim opens already in cruise — this makes getting off Earth the app's best standalone learning surface (thrust, gravity, drag, staging all legible at once), rendered to a broadcast-grade bar (a live launch on TV, not a moving diagram).

Design spine (locked)

• Scene 0 — new launch-site-relative frame (ENU, m→km); can't live in the AU heliocentric world (float precision).
• Fully integrated EOM — src/lib/orbital/ascent-physics.ts, pure fns, CI-validated like fly-physics; per-profile anchor block is the hybrid escape hatch.
• One continuous timeline — multi-scale clock (seconds-dense ascent ⊕ days-dense cruise); existing trajectory data untouched.
• LaunchProfile per launcher — keyed on fleet_refs launcher id; flagship tier hand-authored + generic 2-stage fallback (global-programs coverage, not NASA/SpaceX-only).
• Reuse — /fly multi-camera montage system — beat-driven shot cutting for flybys #371 montage for the shot sequence, ADR-058 scene handoff, Science Lens, the time scrubber.

Slices (RFC-033 §8)

• S0 · Visual direction lock (gate) — art-directed concept mockups for the key beats; broadcast-grade direction signed off before any code
• S1 · frame + clock + engine skeleton (stylised pad, vehicle rises)
• S2 · ascent-physics.ts full EOM + CI validation harness (Falcon 9)
• S3 · LaunchProfile schema + loader + 2–3 flagships
• S4 · camera montage (reuse /fly multi-camera montage system — beat-driven shot cutting for flybys #371) to the S0-locked direction
• S5 · telemetry HUD + Science-Lens ascent layers (TWR/q/losses + force vectors + ScienceChips)
• S6 · scene handoff → warp into helio / cislunar; continuous timeline end-to-end
• S7 · flagship tier complete + generic fallback
• S8 · launch-site panorama (candidate) — explorable pads via the surface-scene renderer
• S9 · i18n + a11y + polish (14 locales, reduced-motion, D-pad, mobile)

Sibling epic (forward-compat, not this epic)

Descent & landing (Moon/Mars EDL) + orbital rendezvous/docking — completes pad → … → descent → surface. The EOM core, multi-scale clock, and re-basing handoff are built general to extend downward (RFC-033 §9).

[chipi]

S0 · Visual direction — LOCKED (2026-07-16). Art direction approved: photoreal-leaning 3D scene + restrained cyan/monospace broadcast-register HUD + constant bottom timeline scrubber + on-vehicle force vectors. Reference frames + spec: docs/wip/2026-07-16-launch-mockups/README.md (4 beats: tower-clear · onboard-down · stage-sep · MECO→cruise handoff). Next: S1 (frame + multi-scale clock + engine skeleton).