Weapons — Projectiles, Seekers & ECM¶

The PROJ_* subsystem: everything a fired weapon does after it leaves the rail — guidance, seeker lock, hit probability, detonation, and the countermeasure (ECM) interactions that defeat it. 0x4C0690–0x4C5D30.

Provenance: Ghidra static analysis of the game executable with FA.SMS symbols applied; every symbol is recorded in the symbol database and applied to the Ghidra project. Progress: reconstruction matrix. Markers follow spec-authoring.md: confirmed · inferred · unknown.

A projectile is an entity with a seeker overlay¶

PROJFire (0x4C2170) launches: it resolves the hardpoint store, computes boresight angles (PROJAimAngles), acquires a lock (PROJLock), and spawns one or more projectile entities (PROJAdd, class 6) — cluster/ripple weapons loop. A projectile is a normal entity whose tail carries the seeker/guidance state (target ids, launch/guidance timers, weave and drag scratch); the weapon type record (_cgt) supplies the capability flags (guided / ballistic / loft / powered / radar-IR-ARH seeker class / cluster / special warhead) plus motor timing and the Pk-curve breakpoints.

Per-frame guidance and detonation¶

PROJMoveProc (0x4C11B0, owner-computer only) runs each frame:

Projectile per-frame flow: engine-state and lifetime checks, then guidance (lock, guide, proximity fuse) or seeker search, then thrust and drag.

Engine state (PROJEngineState) advances boost→burn→coast; lifetime or altitude cutoff detonates via PROJSendCollateralDamages + RemoveCurObj. With a target it re-validates the lock and guides (PROJGuideToTarget / PROJGuideLoft), and PROJProximityFuze fires at closest approach; without one it searches (PROJSelectTarget → PROJScoreTarget). PROJHitChance is the probability-of-hit model — signal × range envelope (PROJRangePk) × ECM × flare/chaff × aspect/closure.

ECM / countermeasures¶

Four defeat mechanisms: jammers (PROJHitChance calls HARDFindECMForObj, reducing Pk in the seeker's band), flares/chaff (PROJLaunchDevice dispenses; PROJRetargetMissilesOnDevice rolls seduction on each locked missile and steers seduced ones to the decoy via PROJGuideToDevice), notch/beaming (PROJInNotch defeats pulse-doppler), and sun decoy (PROJSunInSeeker / PROJGuideToSun for IR seekers).

Functions¶

Full record: db/symbols/weapons.csv.

VA	Symbol	Role
`0x4C2170`	`PROJFire`	master launch: aim → lock → spawn projectile(s) → fire sound
`0x4C0A90`	`PROJAdd`	spawn a projectile entity (class 6)
`0x4C11B0`	`PROJMoveProc`	per-frame guidance / detonation proc
`0x4C2F20`	`PROJLock`	seeker lock acquisition
`0x4C1630`	`PROJGuideToTarget`	proportional guidance to the lock target
`0x4C1660`	`PROJGuideLoft`	loft / high-trajectory guidance
`0x4C3250`	`PROJProximityFuze`	closest-approach detonation decision
`0x4C3380`	`PROJHitChance`	probability-of-hit model
`0x4C3890`	`PROJRangePk`	range→Pk envelope lookup
`0x4C39A0`	`PROJLaunchDevice`	dispense chaff / flare
`0x4C3AF0`	`PROJRetargetMissilesOnDevice`	countermeasure seduction roll + retarget
`0x4C2E40`	`PROJInNotch`	Doppler-notch / beaming detection
`0x4C17F0`	`PROJSunInSeeker`	IR sun-decoy check
`0x4C4100`	`PROJSelectTarget`	autonomous seeker target search
`0x4C1870`	`PROJDamageProc`	apply impact damage + kill scoring
`0x4C1F50`	`PROJProc`	class-proc selector (move/event/damage)

Open Questions¶

1. Lock-tone / RWR bookkeeping globals — resolved¶

They are a multi-slot lock-timing table, keyed on the mission clock _currentT. Two kinds of field, all zeroed by PROJInit and read in the PROJ lock-state aggregation:

Expiry timestamps tested <= _currentT — the track-lock group around _trackLockEndT (0x58F100): 0x58F102/104/106/108; and the search-lock group around _searchLockEndT (0x58F1C0): 0x58F1C2/1C4/1C8. Each marks when that lock slot's window elapses.
Active counters/flags tested < 1 — 0x58F1DC/1DE/1E0, the "lock still up" gates.

A single compound predicate (near 0x4C…) ANDs all of these together with _projLocksOnPlayer to decide "no lock currently on the player" — i.e. this table is the state behind RWR silence vs. the search/track lock-tone. So they are confirmed lock-timing slots, not opaque: expiry stamps + active flags for the per-slot track/search locks.

Status: resolved — re-static (lock-timing slots: <=_currentT expiry stamps + <1 active flags).

physics.md — the HARD_* stores management that arms the hardpoints and supplies seekers/ECM lookups.
objects.md — projectiles are entities; the mirror carries their state.
hud.md — the target box, gun reticle, and CCIP pipper that display lock state.
formats/JT.md — the projectile type record.