Water-cooled lander |
Water-cooled lander |
Aug 22 2007, 05:22 PM
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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 22 2007, 09:59 PM
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#2
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Junior Member Group: Members Posts: 53 Joined: 10-September 05 Member No.: 492 |
These calculations are based on the use of water. I remember using test loads for broadcast TV transmitters that employed the latent heat of evaporation of a Glauber's Salt (sodium sulphate) solution to get rid of the dissipated power. I believe that sodium sulphate has a significantly higher latent heat figure -but Wikipedia etc have let me down so I can't find the number right now.
If the specific heat + latent heat approach is a good one then obviously choosing the best compound will give maximum duration on the surface. Rob |
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