Originally Posted by
FLX/MCT
Were there any contingency scenarios in place for the case that only one booster started successfully?
Yes. It was called 'crash and burn'.
If I remember correctly, the SRBs had three independent igniters, and only needed one to set them alight. So it was one of the less likely failure scenarios, but disastrous if it did happen. The SRBs were bolted to the pad with explosive bolts, but the bolts weren't strong enough to overcome the SRB thrust if the other didn't ignite (that would just introduce another catastrophic failure mode).