Spin AG

[parmasson]

There has been some discussion of using spin to generate gravity on space stations and orbital rings. How far from the surface of the station does this effect go? If I jump up or climb up something tall when does the "gravity" effect weaken so that I float away?

 

[Piper]

It depends on the spin rate. Try recalculating the gravity with a reduced (or increased) diameter, say 10 meters or so and see how much it changes for your given spin rate. If you're thinking about climbing the spokes, try calculating it convenient increments like 1/2G, 1/4G and so on.

 

[parmasson]

Ahhhh….
An object moving at 1rpm in a .5 mile diameter experiences 1/2 the force of an object at a 1 mile diameter assuming it is moving (accelerating). With no real gravitational force to pull the object to the center the system has an escape velocity of just over zero mph.
So . . . .
Since the gravity is produced by the spin it stands to reason that if an object was traveling in the opposite direction of the spin on the decks of the station it would cancel out the force caused by the rotation and become weightless.

 

[Uncle Bob]

1 mi diameter, ~1600m to get 1 G the perifery is moving at 89 m/s (200 mph) Canceling that is going take a NASCAR Winston Cup car.


o\]\r\]=\\

 

[parmasson]

Darn fast to be sure but a cool effect nonetheless. Not sure how it would be useful in game terms but it is a good thing to keep in mind.

I love spinning wheel stations.

 

[Andrew Boulton]

Here's a little animation of a Scout/Courier arriving at that 1 mile wide station. It's basic, but you get the idea. Blue Danube not included

http://www.geocities.com/andrew_boulton/station1.avi

 

[parmasson]

That is extra cool. I can just see the thing in orbit around the system gas giant.


It really hits home just how fast 1 RPM is when you are talking about a structure that big.

The only thing that is different from that splendid animation is that the hub is longer for plot purposes. It contains the fusion reactors and main life support stuff. Why is it all in the hub you ask? So that when the poop goes down the characters have to scratch and claw all the way back up from the ring.

Cheers

 

[Andrew Boulton]

I'll modify it.

 

[parmasson]

Thanks!
Damn Spiffy Stuff. BTW the wheel portion of the station looks TALL. How thick is it?
Looks like 20-30 decks with the old eyeball.

 

[Uncle Bob]

The ghost of Stanley Kubric smiles and bows.

Well done, Andrew.

 

[Fritz_Brown]

Actually, it's not the spin that produces the g's, Parmasson. It's the angular acceleration. Running the other direction wouldn't counteract the effect. (Neither would trying to outrun the spin.) The g-force is produced because the station is changing velocity (speed and direction) at 1g at every point around the circumference. It's the same as 1g of push from behind, except produced by the angular change.

 

[Andrew Boulton]

The rim is 100m thick, as is the non-rotating core.

 

[parmasson]

Very good, basic knowledge increased. Thank you Fritz88.

100 meters tall, that is a very long way to fall.

"Excellent . . . "
-C.M. Burns

 

[parmasson]

Concord Station
All figures extremely rounded for the mathematically impaired like myself
1.609 KM Diameter
804m Radius
That makes it about 1,276,000,000 cubic meters volume using the formula for a torus making the displacement 91,143,000 tons. 100m high is about 30 decks with 3m decks after a bit is taken out for superstructure and other stuff. (Hmmm thats about 900,000+ hardpoints . . . )

In the hub . . .
3,142,000 cubic meters in the hub as pictured in the animation.
=224,400 tons displacement. Plenty of docking space for smaller ships.
Gonna take awhile to do the deck plans I reckon
Corrections to my figures are more than welcome.

 

[Uncle Bob]

Originally posted by Fritz88:
Actually, it's not the spin that produces the g's, Parmasson. It's the angular acceleration. Running the other direction wouldn't counteract the effect. (Neither would trying to outrun the spin.) The g-force is produced because the station is changing velocity (speed and direction) at 1g at every point around the circumference. It's the same as 1g of push from behind, except produced by the angular change.

Uh, I think you have discovered a new principle of physics. That or you are wrong.

By conventional mechanics if you move antispinwise it reduces the rate of angular change, the push on you is less, the effect is identical as if you reduced the spin rate. Moving spinwise increases the apparent rate of rotation and thus the "push". Remember the important measure is how fast you are moving in a constrained path. The squirrel cage/centrefuge contrains your path, but the speed of the cage is only important if you are at rest w/respect to the centrfuge.

So if you run anti-spinwise fast enough you can pick you legs up and float while the centrifuge rotates around you. Eventually the "wind" will accelerate you enough that you will drift into the moving floor.

 

[Fritz_Brown]

Doesn't sound right, Uncle. The acceleration is actually from the change in direction, and the point you step to is changing exactly the same amount as the point you left.

But, it has been a long time. Can you give me a reference?

 

[parmasson]

OK let me see if I have this straight. The "gravity" is due to the fact that my body is moving at 200mph and wants to fly in a straight path off into space. Because the station floor is there my path is curved and I "spin" just like in the "Cajun Cliffhanger" a ride at a local theme park. The ride is a large centrifuge in which people are spun at high speed and the floor is taken away. We are plastered to the wall but if someone drops a coin into the centrifuge it is not effected because it is not moving at 50+rpm (not sure of the actual speed).
Same thing with the space station. If an object is not moving at 200mph it cannot feel the effects of the centrifuge because it is in effect standing still.

 

[mike wightman]

Originally posted by Fritz88:
Doesn't sound right, Uncle. The acceleration is actually from the change in direction, and the point you step to is changing exactly the same amount as the point you left.

Close, acceleration is due to the change in velocity, which is a vector quantity (size and direction).

The point you move your foot to is travelling in a different direction to the point you moved it from because the station is spinning - each point has the same angular speed, but different linear velocity.

 

[Uncle Bob]

Originally posted by Fritz88:
Doesn't sound right, Uncle. The acceleration is actually from the change in direction, and the point you step to is changing exactly the same amount as the point you left.

But, it has been a long time. Can you give me a reference?

Uh, that was freshman physics and I don't think I have that book. I think I still have Simon's Mechanics, but I hoope your vector calculus is less rusty than mine.

Butfollowing your own example, the curvature is the same every where but the rate of change per time varies with which way you are moving

And it doesn't matter whether the motion is you or the wheel. On Skylab the Astronauts demonstrated this by running around the walls near the top of their 21 foot diameter main tank. I've seen the video, it takes the about two awkward bounces to pick up speed then they are running normally. I figure better than 0.5 G at their feet, 0.3 G at their belly button and 0.15 G at their heads.

 

[Andrew Boulton]

I've been thinking about the hub - should it spin or not? Not spinning makes docking easier - and you can have external docking ports - but getting from the hub to the spokes is difficult. Spinning is simpler, but docking is harder (remember ELITE?), and ships have to be stored internally.