At 12:31 AM 2/3/2003 +0000, Ian Woollard wrote:
Pierce Nichols wrote:I just remembered something else that probably decreases the amount of water required for any system. I'm sure most of you are familiar with the Leidenfrost <sp?> effect, aka film boiling. Basically, a thin film of water will protect an underlying surface from even more heat than you would normally effect, because the thin boiling layer at the surface of the liquid is a good insulator. This is what allows you to snuff out a candle with wet fingers, or even dip a wet hand in molten lead, without being burned.I'm unclear that you want to wet the bottom of the vehicle, because of issues with evenness. Instead I think you need to have the underside dry, but suck heat from it by heating water/steam inside the metal and exhaust the hot vapour through holes; the hot vapour then helps form an insulating layer and reduces heat throughput.
The Leidenfrost effect is actually a nuisance because it limits the heat transfer; you're trying to suck heat from the base and transfer it into water and the layer gets in the way.
If the bottom of the vehicle is wet, then the Leidenfrost effect is on your side, because it reduces heat transfer to the skin of the vehicle.
-p
Mars or Bust!
www.marssociety.com
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