# Would a rover on an asteroid float away because of the low gravity?

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## Summary:

Would a rover on an asteroid float away because of the low gravity?

## Main Question or Discussion Point

I’m wondering if a lander/rover landed on an asteroid with a very low gravity, and we wanted to make said rover move around the asteroid, would it “float” away because of the low gravity? Wouldn’t the normal force and the gravitational force equal 0? If we added a propulsion system, how would we know the amount of propulsion to “give” to the lander? I hope my questions are clear. Thank you!

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Orodruin
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Hopping aside, a rover would float away forever if it reached the escape velocity of the asteroid. The normal vs gravitational force does not have much to do with it as the asteroid is round and not flat. The question becomes one about the size of the asteroid vs how fast you want to be going.

Hopping aside, a rover would float away forever if it reached the escape velocity of the asteroid. The normal vs gravitational force does not have much to do with it as the asteroid is round and not flat. The question becomes one about the size of the asteroid vs how fast you want to be going.
So there’d have to be a way to keep the rover from floating away forever. Would the propulsion system work?

russ_watters
Mentor
Wouldn’t the normal force and the gravitational force equal 0? If we added a propulsion system, how would we know the amount of propulsion to “give” to the lander?
The gravitational field of an asteroid can be measured by sending something to orbit it. That will enable calculating the surface acceleration/gravitational force of thrust required. Yes, thrusters would work. They wouldn't be needed all the time, just when rolling over rough terrain that could cause the rover to jump off the surface.

However, the low gravity also means reduced traction, so a rover would be a very slow way to move.

sophiecentaur
Gold Member
However, the low gravity also means reduced traction, so a rover would be a very slow way to move.
A rover could move around much more quickly if it could fire pegs or grapples into the ground and attach tethers / walking legs. Wheels are clearly not the best solution and thrusters would probably be wasteful of fuel.
I heard mention of multi-legged walking rovers being potentially better than wheels even under planetary gravity in some situations. That makes sense as there are no roads available.

russ_watters
Mentor
A rover could move around much more quickly if it could fire pegs or grapples into the ground and attach tethers / walking legs.
That seems cumbersome, but potentially doable.
Wheels are clearly not the best solution and thrusters would probably be wasteful of fuel.
I heard mention of multi-legged walking rovers being potentially better than wheels even under planetary gravity in some situations. That makes sense as there are no roads available.
I'm mostly not referring to getting around terrain, I'm talking about the difficulty of just moving at all. Anything that relies on friction or has the potential to bounce will be a major problem, and that includes legs. The g on that asteroid the Japanese landed on was .13 millimeters per second2. A rover that relied on friction to move would take hours to accelerate to walking speed if it managed to stay on the ground.

sophiecentaur