Jul 272012
At Mach 3+, the SR-71 would get blisteringly hot. This was not due to “friction” with the air as is often claimed, but due to compression of the air. In effect, the SR-71 was a bloody great hammer smashing air molecules; since it was moving three times the speed of sound, the molecules simply could not flow out of the way and instead were compressed to many times normal density and shoved out of the way. The compression occurred quickly enough that the heat built up in the process could not radiate away, and instead was conducted to the skin of the plane.
Interestingly, the hottest part of the plane – apart from the engines – was the one part that the engineers and pilots most wanted to keep cool: the cockpit.
