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Post by banjomd on Jan 14, 2011 13:00:30 GMT -4
Anybody remember the anecdote about John Young touching a moonrock with his bare hand (in the re-pressurized LM, of course) and almost getting frostbite?
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Post by laurel on Jan 14, 2011 13:15:32 GMT -4
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Post by banjomd on Jan 14, 2011 13:33:29 GMT -4
Thanks, laurel. Will do.
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Post by Glom on Jan 15, 2011 20:00:36 GMT -4
Beautiful story! And I liked how I could just turn around to my new bookcase, pluck a book I haven't read in years off the shelf and get that story.
And isn't the Moon looking especially beautiful right now? Especially with all the fast moving clouds too. It's sunrise over Intrepid too.
The Moon: the reason why we're here.
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Post by ka9q on Jan 16, 2011 0:53:15 GMT -4
That anecdote illustrates just how different the moon is without an atmosphere. When people hear how hot the lunar surface can get, they intuitively assume that everything on it gets as hot because that happens on earth. It's just not true. The loose, porous lunar surface conducts heat poorly and there's no atmospheric convection or conduction, only radiation.
A shaded object on a flat surface cannot see much of the rest of the surface so it cannot pick up radiation from it. It can see whatever's shading it, but that too will be dark. And if it sees the dark lunar sky, it can radiate away its own heat and grow quite cold.
It's hard to see how to survive the 2-week lunar night without some form of nuclear power, but thermal solar power seems especially easy during the lunar day.
Any heat engine accepts heat energy from a hot source, converts some of it to useful work, and rejects the rest to a cold sink. The hotter the source and the colder the sink, the more efficient the engine can be. With no atmosphere, a heat collector would receive a guaranteed 1.3-1.4 kW/m^2 of solar radiation. Concentration with lenses or mirrors could produce very high temperatures. Thanks to the lunar vacuum, a radiator could achieve very low temperatures even in the daytime if it were oriented toward the black lunar sky and shaded from the sun and the surrounding surface with highly reflecting materials like aluminized Mylar. The radiator would have to be fairly large to stay cool while dumping a lot of heat power, but the low gravity would allow it to be constructed from very light materials.
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Post by Czero 101 on Jan 16, 2011 5:01:30 GMT -4
When I go to this link, page 167 is not one of the previewable pages. Cz
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Post by banjomd on Jan 16, 2011 9:53:26 GMT -4
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Post by laurel on Jan 16, 2011 13:13:59 GMT -4
Sorry Cz. It worked at the time I posted it.
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Post by Czero 101 on Jan 17, 2011 0:33:43 GMT -4
Thanks... that works... Sorry Cz. It worked at the time I posted it. No worries, Laurel... Cz
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