It's the same explaination. When the SRB joints flexxed the o-rings were meant to stay in place, but the joints were defective and NASA knew the o-rings were moving. However NASA also believed the o-rings could still take the abuse, because although they were moving they were getting shoved deeper into the joint, in a way that wasn't intended but was nonetheless at least marginally effective at stopping exhaust blow-by shortly after it began. But when the o-rings were cold and stiff... they didn't move the same way, exhaust blew by them longer and cut right through. At that point the SRB turns into a cutting torch (the SRBs didn't actually explode until after the shuttle broke up and range safety sent the signal to kill the boosters.

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Mikhail_K 4 hours ago | parent [-]

> However NASA also believed the o-rings could still take the abuse, because

> although they were moving they were getting shoved deeper into the joint,

Why would they be "shoved deeper," when the problem is that the joint opens wider under load?

	▲	anonymars 3 hours ago \| parent [-]
		See here: https://www.researchgate.net/profile/Scott-Post/publication/... What would happen "normally" (i.e. the normalization of deviance) was that the rotation (from the SRB joints bowing--essentially "ballooning") would create a gap, and the O-rings would get blown into that gap and ultimately seal in there With Challenger, it was too cold, so the O-ring rubber was not malleable enough to seal into that space (like the O-ring towards the right of the diagram), so the hot gases were allowed to blow by and erode the O-ring. If they had sealed in (like the one on the left) it would have just taken the pressure but not worn away