Water-cooled lander |
Water-cooled lander |
Aug 22 2007, 05:22 PM
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#1
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Member Group: Members Posts: 214 Joined: 30-December 05 Member No.: 628 |
There is a recent posting on Emily's Planetary Society blog, which must be Doug's because she's not there herself, although her name is the only name on it. The subject is using water to cool a long-lived surface probe on Venus. It sounds far more practical than any of the other proposals for landing giant atomic-powered refrigerators, or developing a whole new family of high-temperature semiconductors, etc.
But I didn't understand the whispered criticism to the effect that the Ekonomov paper assumed that the water would absorb heat only from the one watt of power driving the instrument package itself. I simply can't believe that he went to the podium and presented his model without taking into account the fact that the surface of Venus is a pretty hot place, and that the proposed probe would be absorbing the ambient heat. This is an interesting proposal and I would like to understand both the original calculation of 50 days to bring the water to a boil, and the cited flaw in the calculation. I too find it hard to believe that it would take 50 days to bring water to a boil on the Venusian surface, but where exactly is the error, and what remains after we correct it? Doug is busy of course, but I hope he will find the time to address this when he returns, if someone else hasn't done so by then. |
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Aug 27 2007, 02:25 AM
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#2
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Member Group: Members Posts: 903 Joined: 30-January 05 Member No.: 162 |
I think we would want a retroreflector (and to use a microwave frequency absorbed by the surface materials) so we would be observing a point source on the surface. If we were monitoring an appreciable area the signals from the perimeter of the expanding shock would cause the beam reflections to interfere.
I think the drift of the spacecraft at the Venusian Lagrange spot would be held slow enough that we could distinguish the (relatively) faster surface jolts. We can also simultaneously illuminate the retroreflectors with 2 different microwave frequencies and correct for atmospheric scintillations. As Venus rotates, the reflectors directly below will affect the return signal via verticle oscillations, retroreflectors illumed near the Venusian limb will reveal motions parallel to the surface. If the technique would work from the 60 degree leading and trailing Venusian Lagrange positions also, we might be able to simultaneously study specific retroreflectors from 2 sats, and be able to characterize ground motions more precisely. |
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