Artificial Gravity by rotation

[PacalB]

There are some complications to this, namely the coriolis effect. When water drains out of the tub it rotates, weather systems on earth rotate, all this is down to the coriolis effect.

Just to add ...

That is a bit of a miscoception and not correct Gimi. The boring truth is that water drains every which way no matter what hemisphere you're in, for reasons having mostly to do with the shape of the drain and the way you poured in the water in the first place, and so on. When water is draining out of your bathtub, the Coriolis effect is insignificant, it amounts to roughly three ten-millionths of the force of gravity.

 

[Ian Doncaster]

The bigger it is, the slower it should rotate to retain about 1g gravity for the outer rim. And the slower it rotates, the more danger there is that by walking or running anti-spinward, you will find yourself becoming weightless and toppling over every now and then...

Wait, there's a fault in my logic... Need to think of it a bit more...

The bigger it is, the slower its angular velocity needs to be. The linear velocity (which is what you're locally overcoming to become weightless) is a different matter - that actually gets bigger with size.

You want 10m/s/s acceleration, and acceleration in a spinning frame is linear velocity squared over radius. So for a 10m radius station, you need to have a linear velocity of 10m/s (angular velocity 0.16 rot/s)

For a 1km radius station, you need a linear velocity of 100m/s - which is better for not accidentally floating off - equals a smaller angular velocity of only 0.016 rot/s - which is better for docking, too.

 

[Susimetsa]

The bigger it is, the slower its angular velocity needs to be. The linear velocity (which is what you're locally overcoming to become weightless) is a different matter - that actually gets bigger with size.

You want 10m/s/s acceleration, and acceleration in a spinning frame is linear velocity squared over radius. So for a 10m radius station, you need to have a linear velocity of 10m/s (angular velocity 0.16 rot/s)

For a 1km radius station, you need a linear velocity of 100m/s - which is better for not accidentally floating off - equals a smaller angular velocity of only 0.016 rot/s - which is better for docking, too.

Thank you! I just knew I had made a misstep in my logic.

 

[synchromesh]

I presented this theory in another thread which does make things a little awkward unless im not understanding correctly but here goes....

Lets take Lave for example.....It rotates for artificial gravity.

You prepare to dock and match the rotation....In theory you now have gravity in your ship because you are also rotating...

As you enter the station the area around the ship would then also have gravity so in theory...Unless you used your landing thrusters you would hit the deck like a sack of spuds ?

Does that make any sense cuz it confuses the hell out of me

 

[Susimetsa]

I presented this theory in another thread which does make things a little awkward unless im not understanding correctly but here goes....

Lets take Lave for example.....It rotates for artificial gravity.

You prepare to dock and match the rotation....In theory you now have gravity in your ship because you are also rotating...

As you enter the station the area around the ship would then also have gravity so in theory...Unless you used your landing thrusters you would hit the deck like a sack of spuds ?

Does that make any sense cuz it confuses the hell out of me

Merely rotating in place does not create gravity. The centre of the station will not have "gravity", only the outer rim. Similarly, only the outer rim of a rotating spacecraft will have some little "gravity", not so much the centre area where the pilot is - he'd still more or less float around if he was not strapped onto his seat.

 

[Gimi]

Just to add ...

That is a bit of a misconception and not correct Gimi. The boring truth is that water drains every which way no matter what hemisphere you're in, for reasons having mostly to do with the shape of the drain and the way you poured in the water in the first place, and so on. When water is draining out of your bathtub, the Coriolis effect is insignificant, it amounts to roughly three ten-millionths of the force of gravity.

I stand corrected (Blame some TV program I saw once I say). Thank you.
At least I'm right about the weather systems. I remember this from lessons in meteorology at the Naval Academy. The effect is however noticeable when creating gravity through rotation though, and needs to be taken into account when constructing rotating space stations.

 

[Andrew Sayers]

EDIT: the truth is out there:
http://www.dvandom.com/coriolis/spacestation.html
With lots of nice diagrams.

Very informative! I'm now even more convinced anyone jumping on a space station will feel an irresistible urge to draw a hopscotch court underneath them

 

[Jack Schitt]

This thread is giving me an overwhelming sense of deja vu. Does anyone fancy a game of baseball?

 

[Captain N]

I just dug this up from that usenet thread...

If people are interested, I've written a script in Perl to
track a baseball (more or less) in a spinning environment. I used my
best guess for parameters of B5's rotation. This simulation includes
centrifrugal and corioliss forces, and a naive stab at air resistance
(modeling it as F=-cv^2), but not rotation and no Magnus force.
*Sigh*

Anyway, I could post the code if people want it. It should be
pretty easy to translate to any other language. As it turns out, the
deflection of the ball is significant but not huge .. maybe 4% or do.
Nonethless, whatever they're playing, it's not baseball as we know it

Gosh, this forum's nerdiness has got nothing on these guys. However, it confirms (lack of Magnus force nonwithstanding) what I suspected that B5 is actually big enough that the coriolis effect would not make a game of baseball impossible (the effect gets smaller the larger the station is)

However it would it still affect the ball's trajectories in subtle ways, making it probably very hard for players coming from terrestrial baseball to adjust.

Baseball played on different planets would also be different due to the varying levels of gravity.

I guess there's a reason why the cosmopolitan inhabitants of the Elite universe prefer the noble game of Zero-G Cricket. At least that game has proper, standard physics everywhere.

 

[AtomicHorror]

A few options - it's something I'm interested to see how they manage it, too.

The smoothest way under powered flight might be to fly in along the centre of the cylinder until you were "above" the pad, then turn to fly a widening spiral around the cylinder, slowing increasing your angular speed and radius so that when you touched down on the pad your relative velocity with respect to it was near-zero. Getting the thrust right to do that would be very tricky, though - autopilot only, or very practised manual pilots. It'd make the original Elite's docking look very easy indeed.

Safer would be to have the docking pads on their own rings, which could be spun up or down independently of the main station body: spin down for takeoff and landing, then once you're safely docked and locked, spin back up for microgravity to resynchronise with the station rotation. Or perhaps have clamps on the axis of rotation that you can fly into and be locked, just needing the relatively easy task of matching rotation, then dragged on rails down to the docking pad.

Alternatively again, if the station is large, and the docking corridor relatively small compared with the station, the linear velocity of the docking pad isn't going to be very big anyway, so some decent landing gear will be able to absorb the velocity you get as you land, so long as you don't land sideways to the rotation.

Or maybe a landing pad that lifts up to the axis of rotation, clamps on to the landing gear and then lowers back down to the dock floor. All the pilot needs to do is keep the ship's spin matched to the dock.