One of cooler techniques in Kerbal Space Program is safe, easy and cheap separation of side boosters by sending the rocket into a short spin; upon separation centrifugal force ejects the boosters to the sides, so there's no need for separation motors, strong explosive decouplers or other techniques assuring separated boosters don't crash into the rocket.

Is or was this technique used, or proposed in practice?

  • $\begingroup$ I haven't heard of the technique being used IRL, so I'm going to guess that small separation rockets on the boosters require less energy than putting equivalent spin on the core -- remember that the boosters are near-empty lightweight shells at separation time. $\endgroup$ Apr 4, 2017 at 15:25
  • $\begingroup$ @RussellBorogove: OTOH many rockets are spin-stabilized, so this would come as "free". $\endgroup$
    – SF.
    Apr 4, 2017 at 15:31
  • $\begingroup$ It's difficult to steer a spin-stabilized rocket, so you only see that on small sounding rockets, which don't need strap-on boosters. $\endgroup$ Apr 4, 2017 at 15:34

1 Answer 1


As far as I know, spin separation was never used for strap-on Boosters. The practical issue is, that the centrifugal force puts a lot of stress on the connections between the boosters and the center core. Also, manouverability is practically zero while the rocket is spinning. That means that a gravity turn or change of azimuth are not possible during ascent. Also, you would waste fuel to spin the rocket and stop it from spinning later on (if you need a manouver Change). Another negative point of spinning rockets is the additional sloshing of the fuel inside the tanks which could lead to engine outages.

Therefore, spin stabilization on orbital rockets is basically not used. So is spin separation. KSP is, after all, still very simplified when it comes to practical details in spaceflight.


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