Centripetal force as gravity.

[JonnyBGoode]

So I have what I suppose is a physics question. Suppose you have a rotating space station: A wheel such as the one in 2001, or a Stanford Torus, or a drum like Babylon 5 or The Expanse's Behemoth/Medina Station. You spin it, and you get simulated gravity; I get that part. But it's not "real" gravity; you're still technically in a weightless environment. Now if you were to jump straight up, you'd land roughly where you jumped from, not because there was any "up" or "down", but because you were basically jumping in a ballistic arc due to your angular momentum that made you land at the same point as the station rotated around to that point underneath you.

But what if you were able to jump in the opposite direction from the drum's spin, hard enough to nullify your rotational angular momentum? (Of course, jumping this fast may be a physical impossibility depending on how much "gravity" was being simulated: Babylon 5 was supposedly simulating 1G, and therefore the drum was spinning at about 60mph.) Since you were in space, would you then be floating over the rotating surface? Or would you somehow still "fall" back toward the "surface"?

 

[Face]

AFAIK, we do not have real data for mega-structure artificial-gravity behavior yet, so all is speculation based on well-known physics theories. The theory says that yes, you'd be floating if you e.g. drive a car in the opposite direction of the spin, then jump of a ramp or somesuch. You'd feel "gravity" getting weaker as you accelerate in the car, to a point where the friction of the tires is so small that the engine's power can't be translated to forward motion any more. However, in a habitat you have air, which presumably rotates with the mega-structure as well, causing your car to decelerate again due to friction, and therefore getting it up to speed in the spin direction again. This will cause it to fall back toward the surface sooner or later.

How atmosphere really behaves in such mega-structures would be a nice experiment to do.

 

[Linguofreak]

So I have what I suppose is a physics question. Suppose you have a rotating space station: A wheel such as the one in 2001, or a Stanford Torus, or a drum like Babylon 5 or The Expanse's Behemoth/Medina Station. You spin it, and you get simulated gravity; I get that part. But it's not "real" gravity;

Actually, in General Relativity, centrifugal force and gravity are equally "real" forces (though how much of a "real force" gravity is is called into question). Centrifugal force is just the result of inertia in flat spacetime with a rotating reference frame, and gravity is the result of inertia in curved spacetime with a stationary reference frame. And if you confine your laboratory to a small enough space that you can't measure the effects of curvature, General Relativity says that the two are exactly the same thing.

 

[Linguofreak]

AFAIK, we do not have real data for mega-structure artificial-gravity behavior yet, so all is speculation based on well-known physics theories. The theory says that yes, you'd be floating if you e.g. drive a car in the opposite direction of the spin, then jump of a ramp or somesuch. You'd feel "gravity" getting weaker as you accelerate in the car, to a point where the friction of the tires is so small that the engine's power can't be translated to forward motion any more. However, in a habitat you have air, which presumably rotates with the mega-structure as well, causing your car to decelerate again due to friction, and therefore getting it up to speed in the spin direction again. This will cause it to fall back toward the surface sooner or later.

How atmosphere really behaves in such mega-structures would be a nice experiment to do.

You get at least somewhat of an idea of how atmosphere behaves in such structures from how the atmosphere behaves on planets. Jupiter has its whole belt-and-zone structure because Coriolis forces are quite influential with that particular combination of wind speed, rotational speed, and size. You'd get vertical circulation in a centrifugal habitat similar to the circulation in the plane tangent one of the poles on a planet. Gas centrifuges are another data point.

Most of the uncertainty here is in fluid dynamics, not in the behavior of a solid projectile in such a situation. For that, we have data from years upon years of merry-go-round accidents .

 

[Face]

As long as we don't try it, all we have is predictions based on models built on observations and experiments in other situations. I'd love to see appropriate experiments, even if they are only scaled-down to fit into a rocket.