And you thought you had decompression problems

[chrpai]

Leak causing slow, steady drop in air pressure on space station

http://www.chron.com/cs/CDA/ssistory.mpl/topstory/2336976

 

[CBulla]

What a job they have to figure out where the problem is!

 

[String]

Leak causing slow, steady drop in air pressure on space station

http://www.chron.com/cs/CDA/ssistory.mpl/topstory/2336976

I wonder when they'll send someone outside with a spray gun and soapy water to look for the leak.....


(im surprised they keep it pressurised at 1atm too).

 

[DA Aquamaster]

The US adopted a 100% O2 atmosphere at about 5 psi pressure during the Mercury program as a means to reduce spacecraft weight due to booster limitations. It allowed for alighter structure and provided increased saftey in orbit. However it presented huge risk on the ground during launch. Nasa howver retained this approach throug out the Mercury, Gemini and Apollo programs. Following the Apollo 1 fire a small change was made with provision to use a normal nitrogen-oxygen atmosphere at launch that bled down during ascent to the 100% O2 atmosphere at 5 psi in flight. With the shuttle program, NASA went with a normal atmospheric pressure in the space craft.

The Soviets had bigger an better booster technology and used a nitrogen oxygen atmosphere at 14.7 psi. from the start. A normal atmosphere in the space craft eliminates the need for astronauts to pre-breathe oxygen for several hours before launch to avoid getting bent, avoids the saftey issues with a 100% O2 atmosphere during launch and recovery phases of the flight, and allows a more natural "shirt sleeve" environment.

 

[String]

You wouldnt need 100% O2 if the pressure was kept at maybe 0.66 bar or so.

For structural reasons its better to keep the pressure differential fairly low or as low as practically possible in any case.

I dont know what pressure the EVA suits are pressurised at but i know they do have to pre-breathe for a few hours prior to use.

 

[blackice]

wow the knowledge of some board members is amazing

 

[rjens]

wow the knowledge of some board members is amazing

Couldn't agree more. You folks are awesome.

RJ

 

[DA Aquamaster]

You wouldnt need 100% O2 if the pressure was kept at maybe 0.66 bar or so.

For structural reasons its better to keep the pressure differential fairly low or as low as practically possible in any case.

I dont know what pressure the EVA suits are pressurised at but i know they do have to pre-breathe for a few hours prior to use.

You need less structure with less pressure and that was the idea early in the NASA program.

EVA suits use a reduced pressure to make the suit more flexible. The average dry suit is a good example. If you put it on and fully inflate it in your living room, you look like the pillsbury dough boy but more importantly to bend an arm you have to further compress the suit as you are essentially changing its volume when you move as the joints are not constant volume. This is very tiring for an astronaut so a lot of effort is made to make space suit joints constant volume. But even with that it is not perfect and less pressure in the suit means less effort to move in the suit.

It also means a small hole in the suit will leak proportionately less air with a lower pressure atmosphere. 100% O2 and 1/3 atmosphere makes a lot of sense.

 

[String]

You need less structure with less pressure and that was the idea early in the NASA program.

EVA suits use a reduced pressure to make the suit more flexible. The average dry suit is a good example. If you put it on and fully inflate it in your living room, you look like the pillsbury dough boy but more importantly to bend an arm you have to further compress the suit as you are essentially changing its volume when you move as the joints are not constant volume. This is very tiring for an astronaut so a lot of effort is made to make space suit joints constant volume. But even with that it is not perfect and less pressure in the suit means less effort to move in the suit.

It also means a small hole in the suit will leak proportionately less air with a lower pressure atmosphere. 100% O2 and 1/3 atmosphere makes a lot of sense.

I was aware of the inflation problem restricting movement (and apparently the russian suits on ISS are still hard to move in, especially fingers) but was more interested in what the actualy EVA suit pressure was purely out of interest from a deco point of view. Obviously 100% O2 at a lower pp wouldnt as much of a fire issue as in a full grown space craft and so on.

FWIW, slightly more nasa information here http://spaceflight.nasa.gov/station/

 

[chrpai]

Obviously 100% O2 at a lower pp wouldnt as much of a fire issue as in a full grown space craft and so on.

Just don't fart.