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The ignite command for the Solid Rocket Boosters (SRB) would not be issued unless all three Space Shuttle Main Engines (SSME) were at least 90% of thrust. The launch would have been aborted if one or more of the SSMEs failed to reach required performance before T-minus zero. Abort was possible because the SSMEs could be shutdown after starting.

The SRBs, of course, couldn't be shutdown after ignition. Once the SRB ignition command was issued, abort was impossible (unless maybe both SRBs failed to ignite?).

If only one ignited, what would have happened?

TildalWave
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poke
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1 Answers1

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Everything I can find says the crew would have died. Depending on which one lit, the space shuttle would have either ended up in the ocean, or smacking the Launch Control Center. Of course, before either of those events would happen, the Flight Termination System would have been activated, which would have caused all 3 of the rocket stages to explode.

Even if somehow the SRBs could be ejected when thrusting, the orbiter didn't have enough thrust to lift itself up without SRBs at the launch pad. As a result, the orbiter would have crashed in to the ground, which while it might have been at least slightly more likely to survive than if the FTS had been activated, it still would have almost certainly resulted in a very bad day.

PearsonArtPhoto
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  • Wasn't there any way of dumping ignited SRB core? – TildalWave Oct 31 '15 at 15:54
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    No. The self destruct were all linked as well, so... Even if you could dump the core, the SME couldn't lift off from the ground, which would place you in a really bad spot, where the dumped SRB would essentially explode. All around a bad situation... – PearsonArtPhoto Oct 31 '15 at 16:24
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    Found a discussion of thrust termination for solid rocket boosters here: http://everything2.com/title/thrust+termination ... Hypothetically, thrust from a burning SRB could be terminated so as not to topple the vehicle, but it would appear that no such system was fitted to the Shuttle SRBs. One could imagine all sorts of bad things happening even if such a system was fitted and activated. Best approach (as appears to have been employed): do everything possible to ensure that both engines always light. – Anthony X Oct 31 '15 at 17:21
  • Shuttle SRBs had FTS. It was used in the Challenger accident. See the paragraph labeled Range Safety in this link http://history.nasa.gov/rogersrep/v1ch9.htm Originally there was FTS on the ET too but it was removed eventually. – Organic Marble Oct 31 '15 at 17:46
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    How about blowing the top end open to cancel upwards thrust? Tearing the SRB length-wise? Separating it, let it fly away and then use FTS on it? ... – TildalWave Oct 31 '15 at 17:47
  • Google SRB thrust termination, you will get an eyeful. – Organic Marble Oct 31 '15 at 17:49
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    @OrganicMarble Cool, found some Henry Spencer's posts about it, fourth answer here. So, basically, that was it? SSO and ET wouldn't survive a SRB shutdown. I find that really unsettling. I would have thought that maybe one single approach wouldn't cut it, but that there might be a combination of them that could (reduce forward thrust, reduce core pressure, use of flame retardants, endure the rest... something like that). – TildalWave Oct 31 '15 at 17:57
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    The SRBs were simply made not to fail. If they did fail, bad stuff would happen... – PearsonArtPhoto Oct 31 '15 at 18:12
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    Given that the hold-down bolts would shear from the thrust anyway, can't imagine that an ignition failure on one side could be detected and acted upon by a thrust termination system on the other side before it separated from the pad. Even if that problem were dealt with, you'd have all that rocket fuel burning away right next to all that cryogenic propellant. Not to mention the possibility of hot flying debris emitted by the termination system and/or the solid booster as it burns out. Separating the booster (letting it fly off the pad) could do all sorts of bad things to the orbiter/ET too. – Anthony X Nov 01 '15 at 01:48
  • BTW - All other issues aside, how could a single SRB be allowed to fly itself away from the stack? Weren't the ET and orbiter supported by the SRBs while on the pad? – Anthony X Nov 01 '15 at 01:50
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    The FTS split the SRB casing. It didn't separate the booster. And yes, the full weight of the stack sat on the SRBs and their mounts. – Organic Marble Nov 01 '15 at 02:32
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    There were four giant bolts holding down each SRB, which kept the thing on the pad while the three main engines were firing. The eight bolts were all cut with pyros at the same time the SRBs were ignited. I was thinking that maybe you could not cut the bolts and wait out one SRB burning. However it turns out that the bolts were designed to shear if the pyro didn't fire, so that wouldn't work. Even with just one SRB firing, the thing goes no matter what.

    So the answer is indeed a very bad day.

     – Mark Adler Nov 01 '15 at 06:44
  • Any chance, the operating SRB could be cut loose and allowed to fly away from the rest of the vehicle and the SMEs commanded to shut down? – juvva Nov 01 '15 at 10:29
  • @juwa: See http://space.stackexchange.com/q/10246/25 – PearsonArtPhoto Nov 01 '15 at 10:34
  • Early 70's STS designs included Abort Solid Rocket Motors attached to the aft fuselage of the orbiter. (Jenkins, pp 115-117 in my 1992 printing). If this concept had been retained, MAYBE it could have got the Orbiter off in the case of a launch pad catastrophe, but probably not. – Organic Marble Nov 01 '15 at 14:51
  • I'm no longer certain the shuttle could not lift off with no SRBs attached. It just shed more than half its launch weight. – Joshua Dec 01 '16 at 03:47
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    @Joshua How far would the STS get without the SRBs – user Apr 03 '17 at 15:26
  • I forget the exact details but the film 'SpaceCamp' shows a Shuttle with a group of space cadets on board being accidentally launched into orbit. It comes about when one of the SRBs begins overheating and is about to fire. The controllers monitoring the thing decide to fire the second SRB as the only way to avoid disaster - the exact line is something like "Light it or they're gonna die!" No talk of shutting down the first booster. Good thing the External Tank was full... – GordonD Jan 14 '21 at 13:53