DCT filter housing
Drifting
Joined: Mar 2016
Posts: 1,731
Likes: 496
From: Glenelg MD
The SRBs separate at ~160,000'. It doesn't really matter what the temp on the ground is (Challenger launched in 36F weather) as the air temp at that altitude is a pretty consistent ~30F. That said, the real issue was two-fold: 1) the air temp was colder (18F) leading up to T-0 launch time, with the o-rings themselves hitting as low as 8F overnight (i.e., the o-rings were less compliant), and 2) poor tolerancing of the sealing/mating surfaces allowed the seals to practically twist open once under the pressure of the rocket. By the time the shuttle assembly hits the SRB sep point, it's traveling Mach 4+, and the air friction against the outer skin has already warmed things up significantly (there's a trade-off between the increasing Mach number and the decreasing air density with altitude... by the time it hits Mach 1, the air density has already deceased about 5x from sea level, but things are quite warm by this point regardless). In a nutshell, the o-ring is well beyond room temp by the time the SRB cuts loose of the assembly, but in the case of Challenger, the seal damage (caused by blow-by) was already past the point of no return.
Luckily for us, the worst that could happen in a similar case is a few drops of fluid pushed out
Last edited by Dan Hintz; Oct 18, 2024 at 09:18 AM. Reason: Lowered launch temps
