At 05:01 PM 2/19/2003 -0800, Michael Wallis wrote:
Yes, but you'd have to carry water ( = heavy) plus tanks, lines, valves, sensors and heaters. That's a lot of weight vs some extra HTP and running the engines at "idle".
Actually, I've managed to convince myself that transpiration cooling is not intrinsically heavier than ablative, all other things being equal. Both function by the same mechanism, i.e. absorbing and carrying off the heat by evaporating an expendable coolant. Water will absorb more heat per kg than anything else I know of, due to its extremely high specific heat and latent heat of vaporization. Therefore, all other things being equal, you will have to evaporate a smaller mass of water than of ablative plastic to dissipate a given heat load. I think that the mass of supporting structure & ancillary equipment probably brings the total system masses close enough to be a wash.
-p
Mars or Bust!
www.marssociety.com
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