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  1. #1
    TDF Member taz's Avatar
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    C02 scrubber cartridge?

    .

    I have never dived with a closed circuit, I understand the
    principle fully, just never done it but I read a transcript
    from the Apollo 13 moon mission (from launch to splash
    down in real time, 5 days in total of transmitted talk) and
    obviously the part where they had to convert the lunar
    landers C02 cartridge to accept the Command modules
    Cartridge was very interesting.

    Anyway I digress, in the comments from space ship to Earth
    the changing of the cartridge is mentioned quite a lot and
    the cartridge only needed changing about every 12 hours.

    So if the Command modules cartridge could clean the atmosphere
    for 3 men for 12 hours why can't a similar smaller version be used
    for 1 diver for 12 hours?

    Regards

    Rob

    .
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  2. #2
    Divey McDiveface Nickpicks's Avatar
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    How big were the Apollo cartridges compared to a CCR scrubber?
    Does the ambient pressure have an effect?

    Possibly loop volume plays into it too. In a CCR, the loop volume is as small as possible - only a few litres, and the flow through the scrubber is intermittent and driven by inhale/exhale. On Apollo effectivly, the loop is the entire spacecraft, so scrubber flow must be fan driven and constant. I'd expect the atmosphere on apollo to be a bit less humid than the loop on ccr, does moisture affect the scrubber medium?
    The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair.

  3. #3
    Formerly sbc23cam Steve Clark's Avatar
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    The scrubber was quite big. It's probably twice the volume of some CCR scrubbers, probably explains the longer time.


  4. #4
    Established TDF Member nigel hewitt's Avatar
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    Didn't they use Lithium Hydroxide because it was lighter and smaller?
    And they didn't have the problem that it reacts very badly with water.
    Helium, because I'm worth it.
    Waterboarding at Guantanamo Bay sounded like a radical holiday opportunity until I looked it up.

  5. #5
    Established TDF Member MikeF's Avatar
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    google zorg alien

    the atmosphere the scrubber ran in was a pure O2 atmosphere at 5psi (0.34bar) at an average temp of @ 21C and the metabolic rate of the astronauts in zero g would be very low vs a CCR scrubber running at a gas density of say 10bar at an ambient water temp of say 8C with a diver working hard

    surely the scrubber will be running far more efficiently onboard Apollo?

  6. #6
    Nicotine, valium, vicodin... notdeadyet's Avatar
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    It was also a lithium-based scrubber which is far more efficient than calcium/potassium based scrubbers. Lithium and water don't get on well.

    A normal lime scrubber on most decent sized rebreathers will probably do close to 12 hours surface use, I'd bet 8-10 comfortably. Dense gas in a cold environment is another story. They tried them on Everest and they regularly shit the bed due to the temperatures.
    Last edited by notdeadyet; 02-03-2017 at 09:49 PM.
    Caliph Hamish Aw-Michty Ay-Ya-Bastard, Spiritual leader of Scottish State in England

  7. #7
    TDF Member taz's Avatar
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    .

    Lithium Hydroxide

    Yes that was the cartridge.

    So simple answer as usual, eh?



    As usual a font of knowledge this site

    Regards

    Rob

    .
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  8. #8
    Loathes Snorkels String's Avatar
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    Much lower ambient pressure. Much lower workload (ie rate of CO2 production), not working in a hot, near 100% humidity environment (there is such a thing as TOO much moisture to activate the scrubber), using a chemical that was more efficient at scrubbing as they didnt have to worry about someone mixing it with sea water and drinking it.
    Compared to a CCR, the environment on the Apollo craft is fairly benign.


 

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