Re: Solar sailing vs. laws of physics ?

From: Chuck Kuecker (ckuecker@ckent.org)
Date: Thu Jul 03 2003 - 11:42:05 MDT

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    As long as you call the sail a "heat engine", as Mr. Gold is doing, I guess
    you can call a sailboat's sail a heat engine, too. There's a big difference
    between converting one form of momentum into another and converting heat
    energy into momentum. Sure, the sail will heat up, proportionally to how
    much energy it absorbs, but it is in no way converting heat to momentum,
    unless you want to consider the effect of the momentum of the radiated
    energy off the "heated" sail.

    I don't see why a solar sail would get any hotter from sunlight than any
    other object of similar albedo, either.

    He talks of the Crookes radiometer - a device that has been shown to
    operate because of increased local gas pressure due to the heating of the
    blackened sides of the vanes. This gadget won't spin at all in a good vacuum.

    Sounds like Mr. Gold just does not want anyone spending any of his tax
    money (or investments) on solar sails...

    Chuck Kuecker

    At 18:20 07/03/2003 +0200, you wrote:
    >'The solar sail and the mirror'
    >by Thomas Gold (Center for Radiophysics and Space Research, Cornell
    >University)
    >-3 pages, no figures-
    >
    >http://arxiv.org/abs/physics/0306050



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