STS-112 apparently had a "stud hangup" resulting from one of the pair of
detonators on one nut not firing due to corrosion. There were, I think, 25
stud hangups in 23 launches (STS-2 and STS-92 each having two.) With the
exception of the one above, I believe those were due to debris, re-contact,
alignment issues, etc. (The original Inconel nut halves were capable of
bouncing back and reconnecting with the stud! The nuts were later made
softer.) A number of changes were made to the system to deal with hangups,
including altering the nuts after Columbia with a crossover between the two
detonators.
NASA seems to have believed the SRBs could handle pulling free 4 hung
studs, out of 8 total.
On Mon, Jan 24, 2022 at 12:48 PM Henry Spencer <hspencer@xxxxxxxxxxxxx>
wrote:
On Sun, 23 Jan 2022, James Fackert wrote:
the explosive bolts that held down shuttle solids to the pad until go
time always scared me.... pretty hostile place for multiple pyro devices
that must work every time. Flame, heat, massive acoustical energy and
stress.
Explosive nuts, actually -- the bolts are a permanent part of the pad, the
SRB bases fit over them, and the nuts tie everything together. For
takeoff, the charges break the nuts. Everything is multiply redundant and
very thoroughly checked out; I don't believe there has ever been even a
partial failure.
I'm told that yes, the SRBs have enough thrust to tear themselves free if
push comes to shove, but that's likely to damage the pad or the SRB bases,
and both are supposed to be reusable. :-)
(And remember that we're not done with the SRBs yet, because the Senate
Launch System uses them...)
Henry
