A seal. One stupid, leaking seal. If I am not wrong of PTFE compound ( =Teflon with a filler )
The wikipedia article mentions a rubber seal ( NBR ?)- which I strongly doubt.
http://en.wikipedia.org/wiki/Space_Shut ... r_disaster
PTFE seals with compounds cost between 10 to 30 US$ each, especially made. ( I know because I sell them )
For this application it needed a lot of paperwork. And that is where the story started and ended: red tape.
I didn't read this report. But as far as I can remember reading another report some years ago, NASA was warned about possible disfunctional seals due to temperature differences.
This warning was not just a line hidden in a 1,000 paper manual. It had been reported again and again. The seal manufacturer had been chosen on price only.
The tricky thing about seals is that you can not test them. If you test them, you can not use them again. You manufacture them according a specific procedure, test some samples, and if nothing weird happens, it is
assumed that those seals will always do their job: close a compartment. There are very little control possibilities after manufacturing to see if the seal is properly made.
The seal itself was OK and made according specification. But the chosen material, in that cold environment with mechanical distortion was an engineering mistake.
As the article mentioned, the Challenger disaster is referred to many times what the cost can be to use the wrong seal.
Thousands of people have died in airplane accidents due to bad seals in hydraulics, fuel systems, door seals etcetera. But also in cars , faulty seals have caused many casualties: brake systems, hydraulic stearing, fuel pipes etcetera.
Nuclear accidents happened because valves didn't close anymore or got stuck and couldn't open. Poisonous gasses/fluids escaped because the gasses/ fluids disintegrated the seal material. As a kid we put plastic jumping balls in petrol, so they would grow bigger and get a nice red colour. But we knew to stretch it not too long or you could see the balls get bursts at the outside. We were seven and knew already about the destructive relation between chemicals and plastics/rubber. And every house mother knows how to get chewing gum out of her child's clothes: put it in the freezer and it falls off. Sad that those NASA engineers had forgotten about their childhood experiences.
