Eli5 How does terminal velocity work in lower gravity environments?

Question

I’m having some trouble wrapping my head around this concept. How does falling/reaching terminal velocity change depending on the force of gravity and atmosphere/drag. Example. Falling from the cliff on the Moon vs Earth or Mars vs. Earth.

In: 79

Answer 1

This is primarily a function of density. It might actually be easier for you to think of terminal velocity as buoyancy. The other important component is atmospheric density. There’s also your mass and profile, but we’ll assume that they are the same in all cases and the difference is negligible. Your cliff example is ok, but lets use the real life one, which is a space shuttle entering atmosphere.

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Since the Moon has no real atmosphere, there’s pretty much no terminal velocity. Or if there were, it would be something nonsensical, like 10% the speed of light, or at the least fast enough so if you were traveling at terminal velocity on the moon, you would either hit it or you would orbit the sun.

There’s no good way to aerobreak on the moon since you’re lacking the aero part.

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Mars has some applicable atmosphere. Terminal velocity on mars would be much higher than on earth due to its thinner atmosphere, but it’s at least worth considering. If you do it right, you can slow down to near terminal velocity on mars and save your parachutes some stress. If you managed to jump from a high enough cliff on mars, your terminal velocity would be about 10-100x higher than earth, since the atmospheric pressure is so much lower.

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The real interesting question is a gas giant like Jupiter. Jupiter is large enough to have a terminal velocity ‘profile’. If you started, say, 1000 KM above the ‘surface’ of Jupiter you would accelerate to a very high terminal velocity, probably something like 1000-10000x the terminal velocity of earth, then slowly slow down as the density increased. Assuming you could somehow survive, you would eventually reach a point where your density would be less or equal to than that of Jupiter and your terminal velocity would be zero. You would be forever stuck floating in a high pressure hydrogen soup with a density equal to yours.