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Onwards to Uranus and Neptune!
Mark6
post Feb 25 2008, 02:00 AM
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QUOTE (nprev @ Jan 19 2008, 11:18 AM) *
No argument there! laugh.gif Still, the fact of the matter is that Uranus & Neptune are really off the radar screen right now, and have been for a considerable period of time. I don't like it either, but it is what it is. NH took advantage of an excellent launch opportunity to get to Pluto within a reasonable time to complete the initial recon of the major objects in the Solar System (Note: NO planet/ain't a planet comments welcomed!!! mad.gif I'm serious! Uh, would be remiss without mentioning Dawn as part of this effort as well

By that logic a flyby of Eris & Dysnomia should take priority over Uranus or Neptune. After Dawn and New Horizon reach their targets, Eris is the only "major object" left unexamined.
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JRehling
post Feb 25 2008, 04:34 AM
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edstrick
post Feb 25 2008, 06:12 AM
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"Sedna would be a somewhat more appealing target."

After the Synoptic Survey Telescope's nearly whole sky survey's been going for a year and they've had time to chew on data to spot slow moving 24'th magnitude objects over the whole sky. we're going to have a LOT more Sedna's and other very interesting objects, including some that will blow our mind. There remains the possibility of a considerably larger object way-the-<bleep>-out-there that's one of the possibilities being invoked for explaining the dynamic structure of the KB.

We can keep updating our personal lists of our "KB and Beyond objects we'd like to explore", but till around 2015, when results will be coming in from the SST, etc., all these discussions will be based on a tiny sample of what's in the KB
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Mark6
post Feb 25 2008, 01:25 PM
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QUOTE (JRehling @ Feb 25 2008, 05:34 AM) *
Eris would be a good target, but loses out big-time in terms of the cruise time needed to get there. What's more, I bet you a soda-pop that before the craft got there, Eris will be down the list of largest remaining unexplored objects.

I would not take this bet. My previous post was only semi-serious.
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JRehling
post Feb 25 2008, 06:16 PM
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nprev
post Feb 25 2008, 06:57 PM
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Yeah, the LSST will undoubtedly provide a LOT of surprises; gonna be interesting, to say nothing of paradigm-shifting (such investigations nearly always are, of course)... wink.gif

Getting back to Uranus & Neptune, I'm beginning to think that NH evolutes for flybys might be the way to go given the current state of the art for propulsion & on-board power. As has been pointed out on this thread, any given portion of any of the Uranian moons is illuminated for a few decades or so over an 84 year period, so a flyby really is as good as an orbiter there. Hopefully some innovative proposals might be forthcoming from the community...?


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A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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laurele
post Feb 26 2008, 07:00 AM
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"So we should find any Sednas (now the 5th largest KBO) out to about 200 AU."

I thought Sedna is in the Oort Cloud rather than the Kuiper Belt. Is that incorrect?
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edstrick
post Feb 26 2008, 08:37 AM
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Sedna is between what were supposed to be KB orbits and Oort orbits.

That "supposed" theory has been rattled more than a bit by our expanding understanding of KB dynamics, but it's still got a perihelion way beyond the classical KB.

"You can't get there from here" ... "Tiz a Puzzlement".


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Greg Hullender
post Feb 26 2008, 06:44 PM
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Mike Brown has sometimes called Sedna an "Inner Oort Cloud object," speculating that it's one of a number of bodies between the Kuiper Belt and the Oort Cloud. I just can't WAIT for the LSST to show us what's really out there!

--Greg

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nprev
post Feb 26 2008, 07:57 PM
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I just had a probably very silly idea, and would like to bounce it off of our orbital dynamicists: What about using a cometary heliocentric orbit to reach Uranus or Neptune?

Suspect that the required delta-V might be prohibitively large, but here goes anyhow. What I have in mind is basically using the Sun for a gravity assist by doing a close flyby & throwing an orbiter into a cometary trajectory with its apogee tangental to the orbit of either planet; if the planet just happens to be there at the time, then presumably minimal deceleration would be required to enter orbit.

Very simplistic, and probably not practical (thinking you might need as much as a 50 km/sec maneuver to swing by the Sun close enough)..but thought I'd throw it out there anyhow.



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ngunn
post Feb 26 2008, 08:04 PM
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You could try it this way:
http://www.physics.uci.edu/faculty/STAEF2002Desorp.html
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JRehling
post Feb 26 2008, 09:36 PM
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"Gravity assist" by definition involves a second large body in addition to the Sun. You don't get anything by flying by the Sun in terms of digging out of the Sun's gravity well. In fact, you suffer a net loss. Basically, if the Sun is the only body whose pull is significant (until the craft gets to Uranus/Neptune), then the orbit is going to be a conic section. And the minimum energy involves never being closer to the Sun than necessary (ie, Earth, for launch).

The down side of a minimum-energy orbit is that it will take a long time to get there. But it would only be worse if you tried dipping inside the Earth's orbit. Anything you gained by falling sunwards you'll lose, exactly, on the way out.
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Mark6
post Feb 26 2008, 09:57 PM
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QUOTE (JRehling @ Feb 26 2008, 09:36 PM) *
"Gravity assist" by definition involves a second large body in addition to the Sun. You don't get anything by flying by the Sun in terms of digging out of the Sun's gravity well. In fact, you suffer a net loss.


Actually, there is a way to do it: Powered Solar gravity assist
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ilbasso
post Feb 26 2008, 10:13 PM
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Also, as Star Trek IV showed us, is that by going close to the Sun for a gravity assist, you will go forward several hundred years in time. We could load the craft with nearly extinct animals so that it could repopulate the Earth on the way back out to a KBO. Oh, but then the craft will be several hundred years behind us and we won't get the benefit of its data. Hmm, back to the drawing board...


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ngunn
post Feb 26 2008, 11:03 PM
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The Sun Diver idea is not a 'gravity assist'. It is using solar power (heat) to change the trajectory at perihelion by shedding mass with the right direction and speed. Have another look. It works. So does the idea of a solar sail edge on to the sun on approach and fully presented for illumination after perihelion. Going close to the sun pays off both ways.
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