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Well, not pumping the capsule with 100% oxygen definitely helps too.
by craftyguy 7y ago
Well, not pumping the capsule with 100% oxygen definitely helps too.
- andy_ppp 7y agoDoes it have to be 100% oxygen due to pressure or?
- ls612 7y agoThat’s slightly misleading. Originally they put 1 atmosphere of pure O2 in the Apollo capsule. This proved to be a great environment for fires. After that they pressurized the capsule with 5 psi of pure O2, which is about 1/3 atmospheric pressure.
- andy_ppp 7y agoWhat’s wrong with air is what I’m asking? Are the pressures in the cabin too extreme?
- empyrical 7y agoIf you're wondering why there wasn't nitrogen mixed in, it's because the additional systems+tanks for handling nitrogen would've added more weight to the spacecraft. This video goes in to a bit more detail: https://www.youtube.com/watch?v=FvA7N_j_8os https://www.youtube.com/watch?v=FvA7N_j_8os
- jimbosis 7y agoThese two articles talk about this question: https://www.popsci.com/why-did-nasa-still-use-pure-oxygen-after-apollo-1-fire https://www.popsci.com/why-did-nasa-still-use-pure-oxygen-af... https://www.space.com/17338-apollo-1.html https://www.space.com/17338-apollo-1.html
- _Microft 7y agoReducing the pressure reduces the forces on the pressure vessel. I assume that only the oxygen partial pressure is actually important for respiration.
- grkvlt 7y agoInterestingly, that's higher than the ppO2 at sea level, which is about 3 psi, or at ~5K feet (standard airliner cabin pressure) where it's 2.5psi, so they were still running at almost double the amount of oxygen available normally.
- HALtheWise 7y agoMy understanding is that the initial design was intended to fly in space with a ~5psi pure-oxygen environment for the same reasons that previous spacecraft all did, and that American spacewalks today still do: it reduces complexity, reduces weight, and decreases required hull strength. Fire propagation in that environment isn't actually as bad of an issue as you expect because the pressure is correspondingly lower, so their isn't actually more O2 available in the air. The problem is that the Apollo 1 test was run with both a pure-oxygen environment and a positive relative pressure to the outside, but was run on the ground. That meant a ~16psi pure oxygen environment, which is a real fire propagation issue, meaning materials which were specced not to burn in the flight environment could burn during the test.
- rbanffy 7y agoFrom The Earth To The Moon is an awesome series from HBO and the Apollo 1 episode is great, with a great explanation as to why and how it happened.