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I'm certain there are several flight regimes where this could happen, and that the procedures should be different for each one. For instance, this is a very different question before lift off than it is at 40km. So, presuming that the SRBs were burning and then both cut out, what was the procedure at each regime, and what would have happened?

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If they fail to ignite for any reason, then great success if both and not just one: SSMEs can then be shut down and the Shuttle stays on the launch pad with the flight over. SSMEs are started before the boosters are ignited. There is some machinery involved in the booster ignition, so it cannot be said this absolutely cannot fail.

Once started, the Shuttle booster cannot be stopped even deliberately.

Nightrider
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    Can't the SRBs be unzipped? – Anton Hengst Feb 10 '22 at 18:40
  • @AntonHengst yes, they had range safety packages installed. So they could in fact be "stopped". – Organic Marble Feb 10 '22 at 21:39
  • @OrganicMarble And I suspect that blowing up an SRB right next to a ginormous can of liquid hydrogen and LOX is fairly unlikely to help save the crew or the vehicle (or even the launch pad). – TooTea Feb 11 '22 at 19:19
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    @TooTea consider yourself promoted to the rank of "Captain Obvious" :) In all the times this stuff comes up, I have consistently said that there was nothing that could be done. – Organic Marble Feb 11 '22 at 19:25
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    @OrganicMarble Oh, I only meant to (half-jokingly) point out that this manner of stopping thrust is not going to be useful for anything else than blowing everything up, exactly because I have seen many questions like "why didn't they do X to save Challenger". Sorry if that came across the wrong way. I guess I should delete my comment. – TooTea Feb 11 '22 at 19:32
  • @TooTea no, it's fine, I was trying to be humorous too. – Organic Marble Feb 11 '22 at 19:32
  • @TooTea Actually, I have considered it and my (unprofessional) research suggests that if you were to place a valve between the exhaust nozzle and the solid fuel, closing it would theoretically, (I emphasize the word theoretically), it would deprive the fuel of o2 and cause the flame and combustion to cease. – Deko Revinio Sep 21 '22 at 05:24
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    @DekoRevinio Sorry, but that makes little to no sense. The solid propellant is a mix of fuel and oxidizer, it does not use oxygen from the atmosphere (that's kinda the definition of a rocket engine and what makes it work in space). Once you set the mixture on fire, it will keep burning until it consumes itself and trying to seal it in a container is just going to make it go boom. – TooTea Sep 21 '22 at 06:59
  • @TooTea hey, I did EMPHASIZE the word ** theoretically** on the other hand, I have been able to stop a solid booster during a static test (model rocket). all I really had to do was block the exaust port with something, and it stopped. (it kept burning, but did not put out any thrust) – Deko Revinio Sep 21 '22 at 16:10
  • @TooTea on top of that, you can separate the SRB before it "Goes boom". (I did not think of that during the static test, and it resulted in a pretty charred test pad) – Deko Revinio Sep 21 '22 at 16:22