A missile that steers itself
A bullet with a backward barrel on it is a rocket. Put that barrel on an auto turret and the rocket turns toward whatever the turret sees.
What you see
A missile that bends toward the nearest target and runs it down. Hornets, homing spells, guided arrows, the heat seekers of a fighter jet: one projectile, two parts.
The trick
A projectile can carry barrels (lesson 13), and a barrel with Recoil pushes whatever it sits on (lesson 11). So a bullet with a backward barrel that has Always fire and a lot of Recoil pushes itself along: that is how the stock Rocketeer works. Now put that engine on an auto turret that rides the bullet. The turret turns toward the nearest target inside its Range and Arc, the engine turns with it, and the push now points at the target.
Numbers that matter
| Field | Value | Notes |
|---|---|---|
| Engine Recoil | 5 | 3 or more to drive the missile; lower it if the launcher's own Bullet speed should carry more of the flight |
| Engine Reload | 0.5 | Short, so the push is steady. Each push costs budget, so the shot must be cheap |
| Engine Lifetime | 0.2 s | The exhaust shot must vanish at once, or it counts against the "in the air" budget |
| Engine Damage, Bullet speed | 0 | The shot is only there to kick |
| Seeker Range | 2000 | How far out the missile can see a target |
| Seeker Arc | 25 | How far either side of the launch direction it will turn |
| Turret layer | under the body | The engine barrel draws over it, so no disc shows |
The arc is measured from where you fired
The turret's Arc is centred on the direction the missile was fired, not on the missile's nose as it turns. A missile with Arc 25 can only chase inside a 50° wedge from its launch line, so a target that steps out of the wedge is safe. Only an Arc of 0 (the full circle) chases all the way round, and a chaser needs a short Range or it locks on to whatever is behind you at launch.
Arc and Range together are the missile's target field. Wide and deep covers a lot of ground but picks a specific target badly; small is precise. The two shapes that work are a wide Arc with a short Range (let the engine, not the launcher's speed, do the flying) and a narrow Arc with a long Range, like the 25 and 2000 here.
Gotchas
- Mount the engine on the turret and leave the turret at Facing 0: turn the barrel to 180, never the turret.
- The engine fires once per missile in the air, so a fast launcher costs a lot: a plain cannon at Reload 1 with this missile is 65 of the 120 a second (lesson 15). The Skimmer tube's Reload 4 brings it to 21.
- In the projectile's view the bullet counts as a body of Size 50, so the 188-long engine is also the missile's drawn tail, and it scales with the launcher's Bullet size.
- A manually guided missile is the same engine on a controllable drone: the player's cursor steers instead of the turret.
The guide to creating missiles is a write-up supplied by Random Troller, the author of the seeking projectile technique.