Space/Science — HabitableZone

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

pre-breathing and the history
Nick Hoffman — (archived)

Back in the Apollo days*, the USA adopted an elegant solution to spacesuits - to make the pressure/mobility problem easier and to cut down on the weight of gas and gas bottles needed at launch. They went for a low-pressure oxygen-rich breathing mix. The Russians opted for normal atmospheric composition and pressure.

There were numerous consequences of this, including the Apollo 1 fire, perhaps the Early Soyuz air-leak, and in our case the incompatible breathing mixes and pressures.

Since ISS was designed as an USA-Russia cooperation, it had to be made compatible, somehow, with both choices of suit. The compromise was a near-normal atmosphere in ISS. For the Russians, that's easy, you just suit-up and go. For Americans, the transition to a suit involves pre-breathing a purge mixture of neutral gas and oxygen to reduce blood nitrogen levels. Otherwise, on EVA, when external pressure is acheived, there is a significant risk of the Bends.

Why didn't we adopt the USA breathing mix? Well - the Shuttle was designed as a shirt-sleeves environment too, but there wasn't enough budget to design a new space suit and breathing mix - better the Devil you know, you know !

Plenty of literature on this one...

* Or perhaps before then, for Gemini and Mercury?

Log in or register to post.

The whole thread (49 posts)