Life support?

davo

What exactly is life support? Is it somthing on the shuttle or in their suites? Is it just somthing to recreat the environment of Earth? Please can some one elaborate?

mgb_phys

It's the general term given to all the stuff that keeps you alive!
The pressure, oxygen, temperature, CO2 removal etc.

davo

ok so then it would be in both the suite and shuttle. Now why must CO2 be removed? I mean thats really (except for the 1% [including carbon] of other gases we breath) what we breath in, on this world? So i mean whats so bad about it if this compound has oxygen?

mgb_phys

CO2 is about 0.03% of air but it is toxic at about 5% (about the same concentration as you breathing out) - ifyou don't remeove it from the air it eventually kills you.
CO2 controls your breathing and blood acidity among other things.

YOu can breath in either air or pure oxygen, the only thing you NEED is O2, butthe rest of the air just has to not have anything toxic. Early US capsules used pure O2 but it was a nasty fire risk, modern craft use air and add extra oxygen from tanks as it used up while at the same time removing CO2.

The shuttle flies with a shirt sleeves atmosphere, you don't need a suit inside it, the suit backpack basically contains smaller versions of the shuttle life support systems.
A submarine or a scuba diving rebreather is a similair system.

russ_watters

You may also consider the systems on board that assist other bodily functions to be "life support" systems as well...

Janus

Not quite. While the Shuttle uses a nitrogen-oxygen mix at 1 atm, the suits still use pure oxygen at 4.3 lb/in².

This leads to one drawback. Since the astronauts are breathing a nitrogen-oxygen mix in the shuttle, they have nitrogen disolved in their blood. If they were to go directly to the lower pressure of the suit, the nitrogen would bubble out and they'd get the "bends".

To get around this, an astronaut planning to go EVA has to breathe pure oxygen from a portable unit for 2.5 hrs prior to donning his suit. This flushes the nitrogen out of his blood.

mgb_phys

Interesting - presumably to reduce the pressure load on the suit and stop it doing a 'michelin man', I suppose there isn't much fire risk inside a suit.

russ_watters

Fire risk is dependent on [partial] pressure, so it is greatly reduced by the reduced pressure. That's what makes the error that led to the Apollo 1 fire all the more idiotic. It was acutally pressurized - above atmospheric pressure, with pure oxygen. All sorts of normally benign things become flammable under those conditions.

mgb_phys

Really! I had always assumed the Mercury capsules were run at near 0.21bar and 100% O2 to reduce the mechanical stress while giving a normal ppO2.
Apart from the fire risk, there is a danger of a CNS hit if you are highly physically stressed at high O2 partial pressures.

davo

wow thats alot of stuff that i really wanta learn but i dont curntly. lol. what sciences do you learn that stuff in?

mgb_phys

I'm an astronomer and diving instructor.

davo

then you could really help me in my WAS program, right?