Onwards to Uranus and Neptune! |
Onwards to Uranus and Neptune! |
Jan 12 2008, 09:40 PM
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#1
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Member Group: Members Posts: 813 Joined: 8-February 04 From: Arabia Terra Member No.: 12 |
As soon as MESSENGER gets to Mercury, the most poorly explored planets in the solar system will be Uranus and Neptune. Could this lead to a revival of interest in the ice giants and their retinue, in the same way that the existence of New Horizons is perhaps partly due to the Pluto stamp*?
*via Pluto Fast Flyby and later Pluto Kuiper Express |
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Jan 14 2008, 05:48 PM
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#2
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Senior Member Group: Members Posts: 1018 Joined: 29-November 05 From: Seattle, WA, USA Member No.: 590 |
I get 16 years for the Hohmann to Uranus, but just 30 2/3 to Neptune -- not 40. Calculating as follows:
1) Since the Hohmann is at 1 AU at perihelion and at the target planet at aphelion, the SMA of the Hohmann is (1+a)/2, where a is the SMA of the planet. 10.1147 AU for Uranus and 15.5518 for Neptune. 2) Kepler's third law says period is SMA to the 3/2 power, but we only want HALF the period (since we're done when we reach the target). That gives me 16.08422 years to Uranus and 30.6650 to Neptune. As a cross check, using these numbers I calculate an 84-year period for Uranus and 165 years for Neptune, so I do think I have it right this time. :-) Even so, 30 years is a long time to wait. So's 16. Add to that the fact that currently we can't even swing the delta-V for a Hohmann to JUPITER for a large probe -- much less one to Uranus or Neptune. That's why Cassini and Galileo had to make all those swings by Venus and Earth first. Aerobraking, ion propulsion, and cheaper boosters all seem needed to get a reasonable-sized package to either destination in a reasonable time. On the other hand, all three look like they might be just over the horizon. --Greg |
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Jan 14 2008, 07:12 PM
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#3
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Member Group: Members Posts: 213 Joined: 21-January 07 From: Wigan, England Member No.: 1638 |
Add to that the fact that currently we can't even swing the delta-V for a Hohmann to JUPITER for a large probe -- much less one to Uranus or Neptune. That's why Cassini and Galileo had to make all those swings by Venus and Earth first. Galileo could have reached Jupiter directly, had it been allowed to use its original liquid-hydrogen-fueled Centaur IUS instead of that pansy solid-fuel IUS... -------------------- "I got a call from NASA Headquarters wanting a color picture of Venus. I said, “What color would you like it?” - Laurance R. Doyle, former JPL image processing guy
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