1. Subscribersonhouse
    Fast and Curious
    slatington, pa, usa
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    18 Jan '09 12:56
    This NASA rocket, LOX and LH, the fuel so cold that when it runs, O2 and H2 makes water which collects around the rim and freezes!
    Interesting video.
    http://www.nasa.gov/multimedia/nasatv/on_demand_video.html?param=http://anon.nasa-global.edgesuite.net/anon.nasa-global/MARSHALL/CECE_Engine.asx
  2. Standard memberPBE6
    Bananarama
    False berry
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    28719
    18 Jan '09 20:46
    Originally posted by sonhouse
    This NASA rocket, LOX and LH, the fuel so cold that when it runs, O2 and H2 makes water which collects around the rim and freezes!
    Interesting video.
    http://www.nasa.gov/multimedia/nasatv/on_demand_video.html?param=http://anon.nasa-global.edgesuite.net/anon.nasa-global/MARSHALL/CECE_Engine.asx
    I think the icicles might actually be caused by the Joule-Thompson effect (change in temperature with change in pressure for a constant enthalpy process), which is almost (but not always) a decrease in temperature for a gas undergoing rapid expansion. Here's more info:

    http://en.wikipedia.org/wiki/Joule%E2%80%93Thomson_effect

    I'm suggesting this because according to this link, the temperature in the combustion chamber of a rocket should be quite high (2500 C - 3600 C) in order to maximize thrust:

    http://www.braeunig.us/space/propuls.htm#combustion
  3. Subscribersonhouse
    Fast and Curious
    slatington, pa, usa
    Joined
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    18 Jan '09 21:25
    Originally posted by PBE6
    I think the icicles might actually be caused by the Joule-Thompson effect (change in temperature with change in pressure for a constant enthalpy process), which is almost (but not always) a decrease in temperature for a gas undergoing rapid expansion. Here's more info:

    http://en.wikipedia.org/wiki/Joule%E2%80%93Thomson_effect

    I'm suggesting this because ...[text shortened]... - 3600 C) in order to maximize thrust:

    http://www.braeunig.us/space/propuls.htm#combustion
    The temp is in fact like you said but the cold in this case supposedly comes from the fact the fuel is at liquid gas temps, like H2 at 400 degrees below 0 F or thereabouts and if you look closely you can see frost on the outside of the engine even though an inch away its thousands of degrees, but the extreme cold keeps that heat away from the outside of the engine. I imagine you could get frostbite if you could actually touch the outside of the bell.
  4. Standard memberPBE6
    Bananarama
    False berry
    Joined
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    19 Jan '09 05:371 edit
    Originally posted by sonhouse
    The temp is in fact like you said but the cold in this case supposedly comes from the fact the fuel is at liquid gas temps, like H2 at 400 degrees below 0 F or thereabouts and if you look closely you can see frost on the outside of the engine even though an inch away its thousands of degrees, but the extreme cold keeps that heat away from the outside of the engine. I imagine you could get frostbite if you could actually touch the outside of the bell.
    Hey, you're right...they keep the engine parts very cold:

    http://science.nasa.gov/headlines/y2009/15jan_cece.htm?list733722

    Neat!
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