Orbital mechanics question

[DuncanS]

In the scenario of orbiting a satellite around the moon. What is the main force that keeps the satellite moving with the moon around the earth, as it also orbits the moon? I.e. does the satellites orbital velocity take into account the velocity needed to keep it orbiting the moon AND orbiting the earth? Or do you just orbit the satellite in relationship to the moon, and the moon itself sort of "drags" the satellite along with it in it's own orbit around the earth. I'm sure the answer is both, but in a "simple" model, what would be the main factor keeping the satellite from falling behind the moon as the moon itself moves around the earth.

Sorry if the question isn't clear.

 

[Gravity_Ray]

If I understand your questions correctly, a space ship or a small object in the orbit of a moon (say our Moon), is so small that the moon dominates its behavior. The Planet that the Moon orbits will have a negligible effect on the space ship. Basically the ship's orbit is only affected by the Moon. So a ship will continue to orbit the Moon while the Moon will continue to orbit the planet, while the planet will continue to orbit its star, while the star will continue to orbit the center of its galaxy, etc...

This orbital behavior falls under the Newton's law of motion under orbital mechanics. No change will occur unless some force acts upon that space ship as it continues to orbit.

Hope that is what you were asking.

 

[MeteorWayne]

Certainly the earth (as well as the sun and every other object in the solar system and Universe) has a very small effect, but in a lunar orbit, the primary influence is the moon's gravity.

 

[DuncanS]

Gravity_ray, yes thats pretty much what I was asking, and your answer mostly jives with what I would think. However I don't think it's as simple as "No change will occur unless some force acts upon that space ship as it continues to orbit."

If you have the moon in isolation, not orbiting anything else then the satellite may be in a circular orbit at X km above the surface at Y velocity. But once the moon is orbiting another body at some velocity, then the orbit of the small satellite is going to be affected to some degree -- If it starts at that "back" of the moon, (the side opposite it's forward orbital velocity), by the time it orbits to the "front" of the moon (the side facing it's forward motion) the moon will have "moved under it" so to speak and the satellite will now be closer to the surface by some amount. Now perhaps at such a distance from the earth the moons orbital velocity is slow enough compared to the satellites own that this doesn't amount to much and the satellite is simply "pulled along" with the moon. But it's not a matter of simple inertia since the moon isn't orbiting at constant velocity since by definition it's velocity is constantly changing.

 

[neilsox]

Orbits around Earth's moon are thought to be unstable long term, probably because of the gravity of the Sun and the Earth which distort the orbit around the Moon significantly, If you think of this gravity as a force, then yes, a significant change occurs in the orbit due to outside forces.
An alternate view point is the gravity well of the Moon is lumpy and the lumps change over the course of a month and a year, Neil

 

[MeteorWayne]

Orbits around Earth's moon are thought to be unstable long term, probably because of the gravity of the Sun and the Earth which distort the orbit around the Moon significantly, If you think of this gravity as a force, then yes, a significant change occurs in the orbit due to outside forces.
An alternate view point is the gravity well of the Moon is lumpy and the lumps change over the course of a month and a year, Neil

That's not an alternate view, that's the fact. Please don't speculate in this forum.

 

[neilsox]

Isn't theory more correct than fact. I agree that 90% of the experts agree the warping of space is preferable to thinking gravity is a force. Where is the new student mislead if they use the simpler explanation that considers gravity a force? Neil

 

[MeteorWayne]

neilsox,
As is so often the case, I have no idea what you are talking about.

I was referring to the FACT that the moon's mass is lumpy, and that's what makes lunar orbits unstable.