Rosetta - Post Separation Ops at Comet 67P C-G, November 14, 2014 - |
Rosetta - Post Separation Ops at Comet 67P C-G, November 14, 2014 - |
Nov 14 2014, 05:17 AM
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#31
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Senior Member Group: Members Posts: 2087 Joined: 13-February 10 From: Ontario Member No.: 5221 |
I think I heard it mentioned during the press conference today, (I can't find it now), about Rosetta itself possibly landing eventually, similar to what NEAR did at the end of the main mission at Eros? Since it's not like there's anywhere else to go with the remaining delta-v left by the end of 2015, and sunlight levels and activity starting to drop after perihelion, and the low gravity makes the difference between orbiting and 'landing' trivial. The whole thing would weigh a kilo or two, right?
Obviously there's a few more pressing concerns right now, but it's something to eventually think about. |
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Jan 16 2015, 11:28 PM
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#32
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Senior Member Group: Members Posts: 4247 Joined: 17-January 05 Member No.: 152 |
I suspect we're not seeing the "lawn sprinkler effect" here - to see curvature in the jets you'd need the speed of the jet material to be not too much more than the rotation speed. I don't know what the expected order of magnitude speed for the jets is.
To me it looks more like we're seeing different (more or less straight) jets in different directions superposed along the line of sight. So one jet in one direction in behind, and other jets pointing in a bit different directions in front. You'd expect jets from separate vents to travel in somewhat different directions. |
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Jan 20 2015, 11:19 AM
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#33
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
... I don't know what the expected order of magnitude speed for the jets is... Vapor from sublimating ice should relax with about the speed of sound of the specific gas into vacuum. Very small grains should be dragged the same speed. Larger grains may be slower, down to zero for larger grains not able to escape from the comet. With this approach I'd suggest a few hundred meters per second as velocity of the majority of the jets. I thought I've read 400 m/s without explanation somewhere. The above approach is inspired by this vague memory. I'm neglecting interaction with solar wind and uv radiation on the current level of activity and proximity to the nucleus. |
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