# Artificial Gravity through Rotation BUT on a vacuum

1. Jan 16, 2014

### Razorback-PT

Hi everyone, here's the situation: Everyone knows that you can simulate artificial gravity by rotating a space ship. Usually these scenarios include an atmosphere with regular air inside. I know that the inclusion of air has an influence on the effects inside by way of friction. How different (if at all) would it be to do the same experiment but in a vacuum.

I've made an animation to illustrate the point.

What would happen to the man standing on the outside of the ship? Would he be able to stand there perfectly perpendicular to the ground or would the coriolis effect make him lean?

What would happen if he were to jump straight up?

I'm working on a video game that takes place aboard a spinning space ship. In one of the scenes the player has to go outside and climb a ladder through the spine of the ship. I'd just like to know if that's possible and if yes, what would it be like, compared to regular gravity here on Earth.

Last edited by a moderator: Apr 29, 2017
2. Jan 16, 2014

### kurros

There is no difference between what happens to each of the people. If he jumps "straight up", as it appears to him in the rotating frame, then in the stationary frame his velocity vector gets an extra component towards the centre of rotation, but the net vector still points mostly tangential to this. So he leaves the surface, but his straight line motion quickly intersects with the curved path of the box again, so he lands back on the box.

The air is not necessary for this; i.e. you don't need any friction to keep synchronised with the rotation of the box, because it is just rotating at constant velocity. If you jump, and then the box suddenly stops rotating, then your path will no longer intersect with the box and you are "flung" off into space. Of course if you don't jump and the box stops then much the same thing happens, except your legs get pulled out from under you as the ground zooms off to one side.

Edit: As for the Coriolis effect, I don't believe this is something one can "feel". In the rotating frame it "acts" uniformly on your whole body, and has no r dependence, so you don't feel it just like you don't feel gravity pulling on you when you are in free fall. So it won't make you lean or any such thing. Actually, it is velocity dependent, so you might feel some funky things between parts of your body moving at different velocities relative to each other, like if you wave your arms or something.

Edit2: Ahh ok I forgot some things. This website explains some nice extra effects http://www.dvandom.com/coriolis/spacestation.html
The most fun ones are these I think:
1. If the Coriolis effect is noticeable, then, in the rotating frame, when you jump up you won't land exactly where you started, because your velocity is not perfectly "synced" with the box like I claimed unless you are travelling almost parallel to the box, which is the limit of no Coriolis effect.
2. Similarly, you won't rotate during your flight, so if the box has rotated noticeably during the time it takes to land from your jump, then you won't be exactly upright when you land, which could be unfortunate.
3. As you climb up and down the ladder your velocity has to change to match the increased/decreased velocity of the ladder. So you feel a (Coriolis) force pulling the ladder away from you sideways, but only when you move up or down it.

Last edited: Jan 16, 2014
3. Jan 16, 2014

### kurros

Haha this one (from the same webpage) is fun as well, and I had not thought about it before:

"Staying at a constant radius doesn't eliminate your troubles either. If you move in the same direction as spin, you increase your personal ω and feel heavier...go too fast and you won't be able to stand at all! If you move against the spin, you could potentially come to a standstill and start to float while the ground rushes by under you, although the wind would quickly slow you down enough to regain your footing. Still, having your weight change depending on which direction you move is going to make for treacherous footing. And keep in mind that walking is not exactly a constant radius proposition, you tend to bounce up and down a little, which will only make things worse if you have a small-radius, high-speed chamber."

Lesson: make your space station big enough and rotate slowly enough to minimise these effects, coz they aren't much fun.

4. Jan 16, 2014

### Razorback-PT

Thanks a lot for that detailed explanation and the quick reply. That helped a lot! That link was very helpful as well.

I believe the ship is big enough to reduce those effects considerably. It's about 300 meters long.

5. Jan 16, 2014

### AlephZero

That seems a bit confused. You were rotating at the same angular velocity as the space station before you jumped, so you will continue to rotate at the same angular velocity, unless you deliberately change your angular velocity by the way you jump.

However because of the Coriiolis effect, you will land at a different angular position around the circumference of the space station, so you will not be perpendicular to the "ground" when you land again.

6. Jan 16, 2014

### kurros

Hmm yes that sounds better.