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Life Support

Posted by: spacecowboy - Thu Jan 26, 2006 3:06 am
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Life Support 
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Post Life Support   Posted on: Thu Jan 26, 2006 3:06 am
Calling all life support experts (or anyone with any knowledge of it). In the class I requested launch vehicle information for, I've been assigned the job of coming up with the life support system for a Lunar Transportation System. If anybody knows more than I do (say, read at least one book on that specific topic), let me know -- I'm starting from scratch here, with nothing more than an absolutely uncompromising attitude towards crew safety.

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Post Re: Life Support   Posted on: Fri Jan 27, 2006 4:50 am
spacecowboy wrote:
... an absolutely uncompromising attitude towards crew safety.


Keep'em on the ground then, and use robots. Space is risky and at this stage in development it should be. Or do we have to put warning labels on the air-locks, telling astronauts that breathing vacuum is a health hazard?
[end of rant]

Give them a redundant simple system and a different back-up. Make them both easy to fix with stuff on hand, and use compatible fixtures. (see apollo 13). Emergency hand-crank for the CO2 scrubber fan?

Make the vehicle passively thermally stable in-transit.


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Post    Posted on: Fri Jan 27, 2006 3:40 pm
....Although eliminating the crew would make things much easier, the RFP calls for a minimum crew of 4.

The redundant, relatively simple, and highly robust system is a given. That's just the way I think in the first place. And I didn't know there was a way to make it "passively thermally stable".

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Post    Posted on: Fri Jan 27, 2006 5:46 pm
The Micro-space forum “deep space hardwareâ€


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Post    Posted on: Fri Jan 27, 2006 10:29 pm
Your first issue is how efficient you want your life support system to be. At one extreme you have the Jet Fighter style, open circuit Oxygen system, which wastes at least 80% of your consumed gas. Actually the real extreme is a Mixed Gas, full atmospheric system, which wastes at least 96% of the supplied gas (as compressed air). “At leastâ€


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Post    Posted on: Sat Jan 28, 2006 4:21 pm
As we're designing a system to take a minimum of four people to the Moon and back, and they have to stay on the Moon for a minimum of seven days, I'm pretty sure we want a fairly efficient system -- although building a 99.99999% efficient one would probably be impractical, over-expensive, and would likely not offer much benefit over a 85% efficient one. I was thinking of a mixed-gas system, off the top of my head, but I'm not sure whether this would offer any improvement over a partial-pressure pure-Oxygen system. I'd rather use reuseable systems for everything, as opposed to comsumables (with respect to the CO2 absorbers).

Finally, I assume the 100W figure is per person?

My biggest question is where to find the relevant information.

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Post    Posted on: Sun Jan 29, 2006 4:16 pm
spacecowboy wrote:
... And I didn't know there was a way to make it "passively thermally stable".


I'm no expert, but every object in near Earth space gets heated on one side by the Sun (unless eclispsed, but we're talking about average lunar transit) and to lesser degrees by the Earth & Moon. They also radiate heat on all surfaces. The point at which the two balance determines the object's temperature.

Some vehicles, like the Space Shuttle, need radiators (in the open bay doors) to keep from overheating. Others like the Apollo CSM need heaters to keep from freezing. Both of these require significant electrical power to operate, and are also another system that can fail. I doubt you can do away with them completely, but a vehicle that in standard, in-transit configuration, needs no active cooling or heating would enhance safety.


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Post    Posted on: Sun Jan 29, 2006 5:03 pm
I'm not even sure how to go about that -- but I'll keep it in mind and pass it on to the Space Environment guy (he deals with such things as radiation protection, heating/cooling, and the like, while I get the active systems).

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Post    Posted on: Wed Feb 08, 2006 2:54 pm
Sorry it took me so long to get back on this subject but this is what I have found out. It looks like there is really no good reading material on this subject, but I got a run down on a standard spacecraft life support system.

Traditional categories under the purview of “Life Supportâ€


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Post    Posted on: Wed Feb 08, 2006 3:18 pm
I assume those numbers are per day per person. When considering the heat load for people and equipment, note that 10,000 BTU per day is equivalent to about 122 Watts.


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Post    Posted on: Wed Feb 08, 2006 3:23 pm
Yes


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