Do SRBs throttle down in reality?

[okan170]

This leads to an interesting side-effect (and one discovered by NASA) when in-line mounting an SRB, and one that could add an interesting other dimension to KSP rocket design, as the effect can be both an advantage or disadvantage. In real life, SRB thrust tails off to very low levels after "burnout" and does not completely terminate. On the Shuttle, the separation motors very quickly induced a tumble to increase drag and slowed the booster which assisted in separating it from the Shuttle safely.

However, during Ares 1 development, it was realized that a recently-separated in-line SRB would actually continue thrusting forward if simply cut loose posing a pretty big hazard. Lots of separation motors were used to push the stages apart and attempt to counter the thrust. In order to clear the booster properly before J2X ignition, tumble motors had to fire just below the separation plane in order to knock the still-moving SRB out of the way and then induce a tumble. The low altitude of Ares 1 staging also meant that this had to happen very quickly before aerodynamic effects started becoming dangerous. The final assembly would have been somewhat ridiculous.

The Ares 1-X test attempted this without an upper stage and with the tumble motor at the bottom of the SRB. While it may not have recontacted the dummy upper stage, it came very close.

Having to design around either the advantage of side-mounted ease-off or the dangers the effect poses when its used in-line would be an interesting idea for a mod.

[magnemoe]

You could also use the self destruct on the first stage, blowing holes in the side will stop it from trusting. Solid fuel ICBM even uses the blowout panels to terminate trust at correct speed.

This can not be used easily on side mounted boosters. here you have to use tumbling.

[Nibb31]

You could also use the self destruct on the first stage, blowing holes in the side will stop it from trusting. Solid fuel ICBM even uses the blowout panels to terminate trust at correct speed.

This can not be used easily on side mounted boosters. here you have to use tumbling.

At this stage, the SRB thrust is only residual anyway, so it wouldn't make much of a difference. Also you would want to avoid any debris hitting the upperstage, so you want to keep as much integrity as you can while the upper stage is in the vicinity.

[magnemoe]

At this stage, the SRB thrust is only residual anyway, so it wouldn't make much of a difference. Also you would want to avoid any debris hitting the upperstage, so you want to keep as much integrity as you can while the upper stage is in the vicinity.

yes, it depend if the self destruct system is more violent than the trust abort system on ICBM, one solution might be to have two blow out panels where destruct trigger both while trust abort just the lower one. It has to be some pressure in the stage to give an worrisome trust.

I see the problem however once twr get below 1 you want to drop the stage however the lone stage will then get higher TWR and might hit the upper stage.

If you seperate while its still decent with atmosphere you could use atmospheric braking, air brakes perhaps small parachutes, if done somewhat asymmetric it would also give tumble.