Uranus Orbiter, The other proposed ice-giant mission |
Uranus Orbiter, The other proposed ice-giant mission |
Nov 11 2005, 05:13 PM
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Member Group: Members Posts: 509 Joined: 2-July 05 From: Calgary, Alberta Member No.: 426 |
Since the Neptune Orbiter thread has started to veer into talking about a Uranus orbiter as well, it seemed like a good idea to start a topic for Uranus.
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Nov 29 2005, 02:32 PM
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#2
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
The biggest problem with using steerable aerocapture / landing trajectories is that you need to have a *very* good model of the atmosphere you're using to slow down with.
It's bad enough to have only a vague idea of the temperature/pressure profile of an atmosphere you're using to do straight-line drag braking. If you're designing into your spacecraft and trajectory a need for predictable changes in direction based on lift, *any* significant variation in the atmosphere's pressure, density and temperature profile from your model will result in completely different results. They're talking about needing a Mars orbiter for day-to-day monitoring of the upper atmosphere in order to successfully land future probes -- apparently, Mars' upper atmosphere was so much thinner and extended than predicted during Spirit's EDL that she was very nearly dashed against the surface a la Beagle II. Cassini is seeing that Titan's upper atmosphere also seems highly variable in pressure/altitude. So, in order to successfully use Titan aerobraking for a Saturn orbiter, you'd almost need to already have a working Saturn orbiter there to tell you the detail you need about Titan's atmosphere at that moment... Like many other elegant ideas, this one tends to fall apart when you look at it in greater detail. -the other Doug -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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Nov 29 2005, 03:38 PM
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#3
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Member Group: Members Posts: 903 Joined: 30-January 05 Member No.: 162 |
QUOTE (dvandorn @ Nov 29 2005, 08:32 AM) Like many other elegant ideas, this one tends to fall apart when you look at it in greater detail. -the other Doug {grasping at straws} Can the craft itself scan ahead with a lidar device (or whatever would work) and adjust path 'on the fly' ? Do we expect the Titanian weather reports to repeat precisely every Saturnian year? Are Pluto and Triton far enough out that their atmospheres will model out quite stable in the the relavent altitudes? Would a more 'structured' decel device be worth while? Maybe an RCC wing with some movable aerodynamic surfaces on the trailing edge. (I'm thinking of a shuttle type re-entry with hypersonic manuevuering capability, the craft flies to the appropriate density/altitude, executes the manuvuer wherever that layer happens to be). I'm thinking the amount of gas over a particular surface area will be constant, but its' distribution vertically will vary. Set up something that tolerates the vertical gas distribution range expected and GO! |
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