(Henry Spencer) :

In article ,
Derek Lyons wrote:
It's also possible to design an emergency escape suit *that doesn't
require prebreathing*. Get in it, seal it, and pop out the airlock.
Prebreathe while dropping the pressure down to a level where you can
move the suit, complete the remainder of the escape sequence.

Unfortunately, starting from the station's normal 14.7psi atmosphere, suit
prebreathing even on an emergency basis takes about four hours, which is
kind of a long time to just float in the suit. (Preplanned spacewalks use
less prebreathing time than that because those guys live in reduced
pressure, with increased oxygen content, for 12+ hours first.)

Guys without current spacewalk training are going to be essentially
immobilized until pressure is down to near-normal suit levels; there isn't
going to be any useful mobility during the transition. Guys *with*
current spacewalk training -- which puts a lot of emphasis on building up
hand and arm muscles in particular -- may have some limited mobility late
in the transition.

Why does prebreath take so long? Bubbles? But at the lower pressure tere is
not that much gas in the blood, is there? People often dive to 30 to 50 feet
and come back up in time measured in minutes not hours. So why so long? And
if caution is the main reason for such a long time how much can it be cut
back for an emergency?

Earl Colby Pottinger

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