Understanding Life Support Systems

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    Life Support Systems
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Discussion Overview

The discussion revolves around the concept of life support systems, particularly in the context of space travel and environments such as shuttles and spacesuits. Participants explore the components and functions of these systems, including the management of gases like oxygen and carbon dioxide, as well as the implications for human physiology in varying atmospheric conditions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants define life support as encompassing the necessary conditions for human survival, including pressure, oxygen, temperature, and CO2 removal.
  • There is a question about the necessity of CO2 removal, with one participant noting its toxicity at higher concentrations and its role in regulating breathing and blood acidity.
  • Participants discuss the differences between the atmospheric conditions in the shuttle and those in spacesuits, highlighting the use of a nitrogen-oxygen mix in the shuttle versus pure oxygen in the suits.
  • One participant explains the need for astronauts to breathe pure oxygen before entering a suit to avoid decompression sickness, known as "the bends," due to nitrogen dissolved in their blood.
  • There is a mention of fire risk associated with pure oxygen environments, particularly in relation to historical incidents like the Apollo 1 fire.
  • Concerns are raised about the effects of high partial pressures of oxygen on human physiology, including potential central nervous system toxicity during physical stress.
  • A participant expresses a desire to learn more about the scientific principles underlying these discussions.
  • One participant identifies themselves as an astronomer and diving instructor, suggesting a background in relevant sciences.

Areas of Agreement / Disagreement

Participants express a range of views on the specifics of life support systems, with some points of agreement on the necessity of oxygen and CO2 removal, but also notable disagreements regarding the details of pressure and gas mixtures used in different environments. The discussion remains unresolved on several technical aspects.

Contextual Notes

Limitations include varying assumptions about the definitions of life support systems and the physiological impacts of different atmospheric conditions, which are not fully explored or agreed upon.

Who May Find This Useful

This discussion may be of interest to individuals studying aerospace engineering, environmental science, physiology, or anyone curious about the complexities of life support in space travel.

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

ok so then it would be in both the suite and shuttle. Now why must CO2 be removed? I mean that's really (except for the 1% [including carbon] of other gases we breath) what we breath in, on this world? So i mean what's so bad about it if this compound has oxygen?
 
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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.
 
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You may also consider the systems on board that assist other bodily functions to be "life support" systems as well...
 
mgb_phys said:
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.

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.
 
Janus said:
Not quite. While the Shuttle uses a nitrogen-oxygen mix at 1 atm, the suits still use pure oxygen at 4.3 lb/in².
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.
 
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.
 
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.
 
  • #10
wow that's a lot of stuff that i really wanta learn but i don't curntly. lol. what sciences do you learn that stuff in?
 
  • #11
I'm an astronomer and diving instructor.
 
  • #12
mgb_phys said:
I'm an astronomer and diving instructor.

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

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