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Venera Images, VENERA 13 fully calibrated image
nprev
post Nov 4 2015, 02:29 AM
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Understood. My question was quite poorly constrained. smile.gif Thanks!


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hendric
post Nov 4 2015, 03:40 PM
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Ralph, that report sounds promising for powering a long-duration lander with wind power. 90 times Earth's atmospheric density, would mean the .4 m/s wind is equal to ~3.8m/s, close to cut-in speed for a decent wind turbine. And I would assume windier times and locations are possible? Would it be a good assumption that windspeeds on Venus' surface don't change quickly, since the rotation is so slow?

I guess a space-based instrument won't be able to monitor windspeeds - on Earth the __Scat family of satellites use ocean roughness as a proxy for surface windspeed. I propose a mission to drop a load of neutrally buoyant reflective strips onto Venus along with a radar platform to monitor their distribution. smile.gif


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tanjent
post Nov 5 2015, 05:34 AM
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QUOTE (rlorenz @ Nov 3 2015, 10:45 PM) *
Where terrain (or meteorological) factors introduce an entirely stochastic element to the landing
dynamics, an optimal mission solution may be to build two 90% landers to achieve an overall 99% chance of safe landing.


If the (total) cost of an estimated p=99% mission success is more than double that of a p=90% mission, that formula presents an excellent argument for building and launching duplicate missions, as in the case of Viking or Voyager or MER. Because 81% of the time, you may then hope to realize not one but two successes. (In each case, the second success might be considered partially redundant, but only partially.)
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mcaplinger
post Nov 5 2015, 05:52 AM
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Unfortunately, here in reality the relationship between cost and probability of mission success is not quantifiable with any precision. I'm not even sure that spending more money increases probability of success in all cases.


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JRehling
post Nov 5 2015, 05:42 PM
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QUOTE (mcaplinger @ Nov 4 2015, 10:52 PM) *
Unfortunately, here in reality the relationship between cost and probability of mission success is not quantifiable with any precision.


Agreed. Many in-situ hazards are of unknown incidence, and knowledge of their incidence is exactly the kind of knowledge that the mission is meant to acquire, so there's a Catch-22 there in principle.

Not only Huygens but also an early Venera lander were designed to float. This was overly cautious in both cases, as it turned out. The designers could have thought and spent all they wanted, but ultimately, some exploration had to be done to ascertain whether or not flotation was required. They could have spent a trillion dollars on it and not gotten a better answer than they did by actually flying a mission and seeing what the surfaces of Venus and Titan are like.

Then again, the next Venus lander may unluckily sink into a pond of molten tin. It's hard to prove otherwise until we've explored Venus thoroughly.
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