Water plumes over Europa |
Water plumes over Europa |
Dec 12 2013, 04:55 PM
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#1
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Member Group: Members Posts: 401 Joined: 5-January 07 From: Manchester England Member No.: 1563 |
This seems like the relevant place to post this (could be wrong): Water plumes from Europa? Apologies if it's already been up. The link to the Science article at the bottom doesn't work for me, does anyone have a working link to the original? Cheers.
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Jan 8 2014, 11:54 PM
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#2
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Senior Member Group: Members Posts: 2106 Joined: 13-February 10 From: Ontario Member No.: 5221 |
The issue with parking directly in Europa orbit for any lengthy period is dealing with the high radiation environment and its effect on electronics, correct? Because staying near would take a lot of guesswork out of detecting and intercepting plumes.
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Jan 9 2014, 06:04 AM
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#3
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
A craft would have limited lifetime in Europa orbit. Moreover, that is extremely expensive in terms of delta-v to get into Europa orbit, then back out of it, then out of Jupiter's gravity well and back to Earth. Jupiter' gravity is the great obstacle here, not Europa's. What would make a mission like this work is only diving through Jupiter's gravity well, and getting that energy back on the way out.
The cheapest option would be to avoid Jupiter orbit at all, but that requires that the plumes are active at the time of a rendezvous predetermined years in advance. If we had the notion of the plumes performing on schedule regularly, that would be the best option. Otherwise, Jupiter orbit is essential. Europa orbit would kill the craft with radiation if it had to wait a long time for the plumes. So a high Jupiter orbit is the most flexible. |
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Jan 9 2014, 05:44 PM
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#4
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Member Group: Members Posts: 715 Joined: 22-April 05 Member No.: 351 |
A craft would have limited lifetime in Europa orbit. Moreover, that is extremely expensive in terms of delta-v to get into Europa orbit, then back out of it, then out of Jupiter's gravity well and back to Earth. I wasn't suggesting being in Europa orbit, just that as the orbit around Jupiter becomes closer to one that matches Europa's orbit, the encounter speed goes down. What the best tradeoff would be between a slow enough encounter to preserve complex molecules and getting out of Jovian orbit, I don't know. The proposed Enceladus LIFE mission, which would perform an Enceladus sample return a la Stardust (and many of the principals were part of the Stardust team), planned for a ~6 km/sec encounter. This would preserve large molecules but destroy any intact organisms. Being in Jovian orbit allows multiple encounters to build up the sample. However, if the plumes (if they persist) occur only at a certain point in Europa's orbit, it may be difficult to match the Jovian orbit to encounter Europa at that point within a reasonable time. -------------------- |
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Jan 9 2014, 07:30 PM
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#5
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
For a mission that sits in a circular parking orbit around Jupiter and then shifts to a Hohmann transfer orbit that intersects Europa's orbit, the relative speeds at the encounter are a function of the initial orbital radius. Here are the relative encounter speeds for three different parking orbital radii:
Ganymede-to-Europa: 1.9 km/s Callisto-to-Europa: 5.2 km/s 2*Callisto-to-Europa: 11.2 km/s I'm not including the additional acceleration which would take place due to Europa's gravity. This would be about 2.0 km/s added in each case. So in the Ganymede case, we could have collection take place at about 3.9 km/s. Stardust, for comparison's sake, encountered Wild 2 at 6.1 km/s. The penalties of having the parking orbit closer are to increase delta-v on arrival/departure to/from the jovian system and to increase radiation exposure. The radiation at Ganymede is very roughly 2% that at Europa (depends on which spectrum of charged particle energy we're talking about), so a survival time for craft systems on the order of years should be possible at that distance. This would also allow for Ganymede gravity assists that could be provide some of the delta-v for, e.g., departing the Jupiter system. |
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Jan 9 2014, 10:46 PM
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#6
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Member Group: Members Posts: 715 Joined: 22-April 05 Member No.: 351 |
For a mission that sits in a circular parking orbit around Jupiter and then shifts to a Hohmann transfer orbit that intersects Europa's orbit, the relative speeds at the encounter are a function of the initial orbital radius... John - Thanks for doing the calculations. The good news is that after the capture, Ganymede flybys can be used to crank the orbit back up to lessen the delta V of the burn to return to Earth. Do you know how that compares to the flyby speeds from a Jovian flyby? -------------------- |
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