Throw a booster clear
Bolt a Separation Motor to each strap-on booster so that, when the Decouplers let go, the spent cases are shoved away from your rocket instead of tumbling back into it.
You need this on any rocket with Solid Boosters on its flanks. A Decoupler alone gives a booster a small push; in the airstream the empty case can swing straight back into the stage it just left, and a piece that hits you is a real collision (Debris and dropped stages).
- You have bought the Radial Staging node, which sells the Decoupler and the Separation Motor together.
- The boosters are on the rocket, on Decouplers, and you have not launched: the motors go on in the hangar.
Steps
- In the hangar, pull a Separation Motor out of the Engines tab. It is the smallest part in the tab: a tan drum with a bell at each end, both turned to one side.
- Drop it on the booster's OUTER flank, level with the middle of the case. It snaps to the booster's rail like a decoupler does. Its push goes straight out from whatever it is bolted to, so level with the booster's middle it shoves the whole case sideways without spinning it.
- Tap the motor, then Symmetry. A linked twin appears on the other booster (Mirror a part). The mirror turns its nozzles the other way, so both motors push their booster away from the core.
- Tap Stages and put each motor in the SAME stage as its booster's Decoupler. Select the motor on the ship and tap + on that stage. Motors light before decouplers in a stage, so the booster leaves already pushing.
- Fly. When the boosters burn out, tap STAGE. Each booster leaves with a one-second flame off its flank and falls away from the rocket.
What you should see
Two short bright jets out of each motor, splayed up and down across the booster's skin, and the boosters sliding outward and dropping behind. The jets last about a second and the motor is spent; nothing of it comes back. The rocket's own thrust, Δv and fuel figures never counted the motors, so nothing on the readout changes when they fire.