Slashdot Mirror
The Tragedy Of Apollo 1 And The Lessons That Brought Us To The Moon (forbes.com)
An anonymous reader writes: On January 27, 1967, the Apollo 1 crew was performing a "plugs-out" test of the Command/Service Module, an essential simulation of how the three-person capsule would perform under in-space conditions under its own power. At 6:30 PM, a voltage spike occurred, leading to a disaster. In 26 seconds, everything changed. The Apollo 1 fire and the tragic death of all three astronauts wasn't due to just a single point-of-failure, but rather due to five independent confounding factors that if any one of them had been different, the astronauts Grissom, White and Chaffee might have survived. As it stands, all the crewed Apollo missions were scrapped for 20 months while NASA changed how they did business. The changes worked remarkably well, and 2.5 years later, humans walked on the Moon.
I did go to the link in an incognito window just to check. It is in fact StartsWithABang's blog. I guess if he thinks he removes his name from the post he'll have better luck.
Lesson learned: If it goes to Forbes, it's likely StartsWithABang.
Well, here you go then:
In flight, the cabin pressure was about 3psi. This meant you could make the whole structure lighter. Now, you can't breath air (for long) at 3 psi, it won't have enough O2 in it, so you make it pure O2. Turns out to be about the same partial-pressure of O2 as it is in normal air at sea level. The flame tests they did on materials at 3psi O2 were satisfactory. (Lower cabin pressure also means you don't need to go through a decompression sequence to get into your spacesuit and go EVA, or try to design a one-atmosphere suit.)
Where that all went wrong of course was the plugs-out test where you're trying to simulate the ship in a vacuum when it's really surrounded by sea-level air. One way to do that is to pump up the interior pressure to one atmosphere plus a bit ( I think they were running about 16psi ) so you can check for leaks and such. If you make up that pressure with pure O2 -- which they did -- you're asking for trouble. Trouble like stuff that doesn't burn well in 3psi O2 might go up like a torch in 16psi O2 ... which nobody tested until after the fire. (Or if they did, higher management and NASA didn't listen, kind of like the deal with letting the O-rings get too cold on Shuttle boosters.)