New Horizons Trajectory |
New Horizons Trajectory |
Jun 28 2008, 05:55 AM
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#31
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Senior Member Group: Members Posts: 1018 Joined: 29-November 05 From: Seattle, WA, USA Member No.: 590 |
dmuller: Yikes! I'm repeating myself and doing more work the second time! :-) Getting old sucks . . . :-)
Note that the hyperbolic excess doesn't actually depend on which direction NH is going; any small body with the same speed but ANY vector would end up with the same excess (unless it hit something first). That means you can compute hyperbolic excess without knowing the semimajor axis of the hyperbola, as follows: sqrt(v^2 - 2*mu/r) So if you know a thing's speed and its distance from the Sun, you can compute the hyperbolic excess with no other info. Of course, if the object isn't in a hyperbolic orbit, then this'll give you an imaginary result, so you should test that v^2 > 2*mu/r -- which is the same as testing that v^2/2 > mu/r which is the same as kinetic energy > -(potential energy). Cool stuff! :-) --Greg |
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Jun 28 2008, 07:59 AM
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#32
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Member Group: Members Posts: 340 Joined: 11-April 08 From: Sydney, Australia Member No.: 4093 |
Getting old sucks . . . :-) Well, at least you're not on the record for calling the mission "New Messenger" like I am -------------------- |
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Jun 28 2008, 05:09 PM
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#33
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Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
16.6 km/s - Voyager 1 14.9 km/s - Voyager 2 12.5 km/s - New Horizons 11.3 km/s - Pioneer 10 10.4 km/s - Pioneer 11 Tougher question: Are any of these going fast enough (in the right vector) to eventually escape the Milky Way? -------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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Jun 28 2008, 09:48 PM
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#34
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Senior Member Group: Members Posts: 1018 Joined: 29-November 05 From: Seattle, WA, USA Member No.: 590 |
Tougher question: Are any of these going fast enough (in the right vector) to eventually escape the Milky Way? I figure local escape velocity from the Milky Way at about 800 kps, assuming none of the mass of the galaxy is outside the Sun's orbit. Wikipedia says ~1000. http://en.wikipedia.org/wiki/Escape_veloci...cape_velocities The Sun's orbital velocity is 220 kps, so just adding 10 to 20 kps isn't anywhere near enough. --Greg |
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