Onwards to Uranus and Neptune! |
Onwards to Uranus and Neptune! |
Feb 14 2008, 05:25 PM
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#76
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
I believe trajectory search and optimization software nowadays uses Keplerian orbits and patched conics to find plausible/optimum trajectories (and things like impact parameter or miss distance during flybys) and then when a "conceptual" trajectory is selected, it's precisely worked out by numerical integration and taking into accounts other factors such as solar light pressure, etc. That last part might be iterative and computationally more expensive, but it's all within reach of modern computers.
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Feb 14 2008, 08:17 PM
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#77
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
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Feb 17 2008, 08:17 PM
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#78
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Junior Member Group: Members Posts: 21 Joined: 29-November 06 From: SESE/ASU Member No.: 1437 |
This has got me thinking about if you could pull off a Uranus/Neptune Orbiter for less than $850 million...
Aerocapture is obviously the way to go, and the Titan Explorer orbiter seems a good place to start. It masses ~1800 kg wet, while the cruise stage ~1500 kg, mainly fuel. If we drop the balloon and lander, we cut out roughly 2/3 the mass of the cruise stage, giving a payload mass of ~2300 kg. That's about half the mass of TE. The option then is either to use a low-end EELV (Atlas 401, Delta IV sans SRBs, or Falcon 9) for a single launch (more likely), or launch two spacecraft (one Neptune, one Uranus) on an Atlas 551 (much more cost effective, but less likely). The point is, I don't think it's a given that a ice giant orbiter has to a ridiculously expensive Battlestar Galactica style mission like Cassini. It's just like Mars Sample Return; if you're willing to use new technology (aerocapture and ASTG in this case) and make compromises, you can turn a perpetually paper mission into reality... Simon |
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Feb 18 2008, 04:35 AM
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#79
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Junior Member Group: Members Posts: 22 Joined: 2-March 06 Member No.: 691 |
There is the opportunity, brought up in another thread, for a Jupiter > Saturn > Neptune tour with launch opportunities 2016-1018. It could then go on to visit one or more KBOs. A presentation on this opportunity as a New Frontiers candidate was made to a group reviewing the program in November, I think. An ideal mission would drop a probe into the Saturn atmosphere as well as Neptune. It would also do a close fly-by of Triton. Don't know if the orbital mechanics will allow this and still do the probe relay. This had me thinking... why can we not have three droppers, one at each? This would make an orbit of Neptune cheaper. How do you ask.. if you drop of a probe into Jupiter, Saturn, and before you make Neptune orbit you have less mass to slow down. what do you all think? |
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Feb 18 2008, 08:55 AM
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#80
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
you have less mass to slow down. What about mass you actually need to launch? Does it go down as well? -------------------- |
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Feb 18 2008, 02:55 PM
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#81
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Member Group: Members Posts: 903 Joined: 30-January 05 Member No.: 162 |
This has got me thinking about if you could pull off a Uranus/Neptune Orbiter for less than $850 million... Simon Not to put you off of working through cost savings for interesting mission concepts, but my ideas for a 'cheap' Neptune orbiter were pretty thoroughly discredited and chewed up here a while back . . . |
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Feb 18 2008, 05:08 PM
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#82
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Senior Member Group: Members Posts: 1018 Joined: 29-November 05 From: Seattle, WA, USA Member No.: 590 |
I think the problem with launching a Neptune and Uranus probe in the same rocket is that the next obvious launch window for that is about 80 years away.
Of course, gravitational assists are complicated beasts; there could well be some complicated sequence that managed to split them up at the right point and get them both to the right places, but it'd be a wonder to behold. --Greg |
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Feb 18 2008, 07:15 PM
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#83
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
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Feb 19 2008, 03:03 AM
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#84
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Senior Member Group: Members Posts: 1018 Joined: 29-November 05 From: Seattle, WA, USA Member No.: 590 |
I thought about that, but I think the trouble is that one of the two is going to get a pretty lousy gravitational assist, and given the distances involved, that seemed like a loser -- and maybe not even enough delta-V to get both to their targets.
And, as you say, every year it gets worse. --Greg |
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Feb 19 2008, 04:45 AM
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#85
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Junior Member Group: Members Posts: 22 Joined: 2-March 06 Member No.: 691 |
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Feb 19 2008, 04:26 PM
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#86
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Senior Member Group: Members Posts: 1018 Joined: 29-November 05 From: Seattle, WA, USA Member No.: 590 |
How does that follow? You'd clearly have less mass to launch if you didn't drop anything at the earlier planets.
--Greg |
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Feb 20 2008, 06:26 AM
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#87
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Junior Member Group: Members Posts: 21 Joined: 29-November 06 From: SESE/ASU Member No.: 1437 |
Well then drop the second vehicle and fly the one with a faster trajectory. Point is, I still think it's possible to build a very capable New Frontiers-class Neptune Orbiter...
Simon |
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Feb 21 2008, 12:42 AM
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#88
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Senior Member Group: Members Posts: 1018 Joined: 29-November 05 From: Seattle, WA, USA Member No.: 590 |
I hear you. I'd love to see a serious proposal. Say, starting with $90 M for a Falcon 9 Heavy to put 12 tons in GTO. What can you do with 12 tons in GTO with about $800M to spend on it? And, assuming no other never-before-flown technology.
--Greg |
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Feb 21 2008, 01:14 PM
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#89
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Junior Member Group: Members Posts: 66 Joined: 8-November 05 From: Australia Member No.: 547 |
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Feb 21 2008, 04:27 PM
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#90
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Senior Member Group: Members Posts: 1018 Joined: 29-November 05 From: Seattle, WA, USA Member No.: 590 |
Sorry, but i'll believe it only when I see it fly. And even if it ever does, it'll cost way more than 90M. Good points, but my question is "taking Falcon 9 Heavy on faith -- but nothing else, does that change the picture? That is, is the launch vehicle cost the only thing that keeps us from having a New Horizons-class Uranus or Neptune orbiter?" --Greg |
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