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Space/Science » in reply to pre-breathing? could you elaborate?

re: pre-breathing? could you elaborate?
Chris Vancil — (archived)

Soft Suits use less than "atmospheric" pressure (~4 psi) otherwise you would look like a gingerbread man stiff and unbending. So you pre-breath pure oxygen prior to EVA to prevent the bends. If you used some other gas than Nitrogen in your atmosphere you don't have this issue (usually just squeaky voices).

Nobody has as yet built a Soft Suit which would require zero pre-breathing (ZPB). So the Hard Suits is the only design which allows you to just jump up put it on and do an EVA. In Zero-G a Hard Suit's mass and rotory bearings are not a problem. I don't know why they don't use them on ISS...maybe the storage issues and costs.

Anyway, on ISS the presumption in the past has been any event that requires an EVA right that second and didn't allow for pre-breath would be fatal anyway. A fairly large hole in the station would take hours to empty the air out and it is better to patch from inside than out (if you can get to it). The shortest pre-breath is about 15 minutes I believe.

A good site to check out about this is: Mobility, Mobility, Mobility!
And the main page: The Space Suit Site

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