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Posted by Bill S on May 17, 2008 at 12:42:06 pm EDT
In reply to new kind of bag-Lippi Selk Bag posted by MTB416 on May 13, 2008 at 12:50:46 am EDT

Hmmm, since you haven't been paying attention, I will remind you that in fact I am (or was until I retired), quite literally, a rocket scientist (well, ok, I still consult, so I am still a rocket scientist). In one sense, Tom is quite right - camping gear is basic physics. But, Tom, I gotta disagree with you a bit - since rocket science is, in fact, basic physics (plus a bit of basic chemistry), camping gear can be considered rocket science.

MTB, Tom got so hot in the space suit because he forgot one thing - ya gotta turn on the air conditioner that is built into the suit. In space, you basically are balancing the heat input of unfiltered sunlight on one side of you with the emptiness of space on the other (no convection and no conduction to speak of, but direct radiation of a 10,000F body on one side and radiating into 2.7 Kelvin on the other, which is about -450F). The "air conditioner" in the suit balances things out, plus the suit provides insulation, just like a a mummy bag, though much more efficient.

Oh, yeah, why legs on a space suit. That's actually kind of obvious, but basically maneuverability. You do sacrifice some insulation capability, but there is so much direct radiation from that 10,000F big ball of hot, glowing gas (aka the Sun) that your major problem is getting rid of heat when you are in direct sunlight and keeping it in when in shade. The thermal balance is a fun problem to work out. In that case, the thermal inefficiencies of having the legs and arms pretty minor, where in a sleeping bag, they are the major problem.

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