Are stable orbits possible between Mars and Jupiter?

  • #1
Albertgauss
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Just quick question: Could you put space stations (or even other small planets) at any aribitrary orbit or any radius in between Jupiter and Mars? Or, if something attempted to do so, would the orbit be unstable, and the object drift to either Mars or Jupiter?

I was reading about Lagrange points, positions of stable orbits around planets and moons. Lagrange points are special, in which small objects compared to the moon or planet can maintain their position with respect to the larger planet/moon. If the smaller mass is not at the Lagrange point, it will fall into the planet or fly away. But if you are far away from a large planet---like way in between Mars and Jupiter---are Lagrange points even worth considering? That is, is the issue or stable VS unstable orbits and Lagrange points only relevant when the object is near large graviational body relative to itself?
ArbitOrbit.jpg
 
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  • #2
Janus
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There are plenty of asteroids in stable orbits between Mars and Jupiter, so such orbits exist. There are some orbital radii that won't work however. Look up "Kirkwood gaps".
 
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  • #3
Vanadium 50
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Also "stable" is not a binary thing. Stable for one orbit? No problem. Stable for a trillion? Might be impossible.

If you are talking about a space station, how many orbits do you really need? Five? Fifty?
 
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  • #4
Albertgauss
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Stable on the order of centuries, is what I was thinking, longer than the lifetime of a person.

I did start reading about the Kirkwood Gaps, very interesting--those seemed to be in the asteroid belt. What about in the regions between Mars and the Asteroid belt, or between the Asteroid belt and Jupiter---would such space provide stable orbits on the order of centuries as well?
 
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  • #5
Janus
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Stable on the order of centuries, is what I was thinking, longer than the lifetime of a person.

I did start reading about the Kirkwood Gaps, very interesting--those seemed to be in the asteroid belt. What about in the regions between Mars and the Asteroid belt, or between the Asteroid belt and Jupiter---would such space provide stable orbits on the order of centuries as well?
Mars is roughly 1.52 AU from the Sun and Jupiter is 5 AU. The asteroid belt, including periphery groups, extends from 1.78 to 4.2 AU.

Graphically, it would look something like this, with the red dot being Mars, the magenta one Jupiter and the blue line the asteroid belt.

aster-belt.gif


So the asteroid belt includes most of the orbital radii between mars and Jupiter.
In addition, the circle surrounding Jupiter represents its "gravitational sphere of influence". This is distance from Jupiter where its gravitational effect begins to exceed that of the Sun's.

So there are only fairly small "gaps" between Mars and the belt and between Jupiter and the belt. Object's placed there wouldn't likely be stable for the "long term". But "long term" means a something a bit different in astronomical terms vs. human terms. For example, the orbital precession of planetary orbits is measured in fractions of degrees per century.
 
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  • #6
Albertgauss
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That last graph helped a lot. I realize I was visualizing the asteroid belt as a thin layer (radially)) between Mars and Jupiter, which was wrong, so the graph there helped to correct that the asteroid belt really does extend, comparatively, from Mars to Jupiter.

I think I'm good here. If people have other comments, by all means, post them, but I feel I have the information I wanted. Thanks for your help everyone.
 
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  • #7
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For visualization of Kirkwood gaps, see:
https://en.wikipedia.org/wiki/Kirkwood_gap#/media/File:Kirkwood_Gaps.svg
This graph does not extend to especially 5 AU of Jupiter. I have seen some that do.
But in terms of broad regions, shortage of asteroids there does not prove instability. Narrow gaps do... but the instability of Kirkwood gaps is said to be on timescale of a few million years. Not a few tens.
 
  • #8
stefan r
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The Hilda group asteroids are worth looking at. They are effected by Jupiter but never run into any planets.

If you are looking for a safe place for a station the Kirkwood gaps might be a good choice because asteroids do not have stable orbits there.

A better place for a station might be the Trojan orbits. If your colonists plan to come and go from the station then you want a low delta-v to flyby Jupiter. The tendency toward throwing things into new orbits is a feature when your economy depends on transporting supplies (or people) in and out of other orbits.

Some stations might be described as a mining operation on an asteroid. In that case an asteroid close to an unstable orbit is a better asteroid. You set the outpost on such an asteroid and give it a slight nudge. Dangerous mining tailings could be dumped into a collision course. Valuable resources are tossed toward consumers.
 
  • #9
Albertgauss
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That's really great, Stefan r. I never even heard of the Hildas until now. I'm already reading about them thanks to your post. Thank you for mentioning that, Its really cool!
 
  • #10
ohwilleke
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Also, if a space station is in a marginally unstable orbit, even on a scale of several times around the Sun, that is tolerable, because unlike asteroids, the space station can be tweaked into position with a slight amount of thrust (either integral to the facility or applied with an external craft) now and then.
 

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