[JurijD]

Originally posted by Loser:
I will stand by my contention that the constant, semi-random displacement forces involved in real people living their lives inside a spinning-wheel space station are sufficient to make the concept wholly impractical without significantly different means of station-keeping. Every bit of thruster fuel has to be lifted to orbit as well, and I contend, as well, that it will be expended at a fairly rapid pace.

We had this discussion before A while back when we were talking about sending a manned mission to Mars. And I explained then that If you have a rotating enclosed space station with people inside the people inside CANNOT (I repeat CANNOT) affect the total rotation or linear momentum of the whole system. (Now I don't know what happened to space lab, maybe it was just built badly and that was the reason for its orbit deteriorating, the people inside jumping about surely weren't !) Just look at Mir... those russians had some wild parties up there

EXPLANATION:
Say we have a roating wheel in space and its hollow on the inside. Now lets say that we have an astronaut that starts to run on the inside of that wheel in the same direction the space station is spinning. Running like that would produce a force by his legs that would work against the space station's rotation. BUT! the overall rotational momentum of the space station and the person inside wouldn't change as this is an inclosed system with no outside forces acting upon it and the sum of the rotation energy of the astronaut and the space station would be conserved.
1. space station and astronaut spinnign together: D1 = m*r^2*W1 + a*r^2*W1
D1.. total rotational momentum at the beginning
m.. mass of the space station
a.. mass of the astronaut
W1.. beginning rotational speed
r.. space station radious

2. astronaut start running and achieves a speed of Wa=W1+dW.
D2=m*r^2*Wss + a*r^2*Wa
D2=D1 (the total rotational momentum is conserved)
and with some rearangements we can see:
Wss= W1 - (a/m)*dW
D2.. total rotation momentum at the end
Wa.. ending speed of the astronaut
Wd.. the increase of the astronauts speed over his beginning speed
Wss.. ending speed of the space station

So you see we end up with an astronaut runnin dW FASTER than the speed of the original space stations rotation AND a space station rotating (a/m)*dW SLOWER then before.

But the funny thing is that the moment the astronaut STOPS running the space station will return to ist original rotating speed W1!

Friction and all other forces produced by the astoronauts legs touching the ground of the wheel will make no difference here as this is an inclosed system and it respects the law of the conservation of momentum (linear and rotational).

If this doesnt make sense to you try to think of it this way. Lets say we enclosed you in a hollow sphere in space and gave u the task of movig it around. You woulnd't be able to do it. You could bounce off one of the walls and the spere would go the other way but the moment u hit the opposing wall the spere would stop again. And the center of gravity of the spere and yourself put together would't change in this manuever... so even if you would be in orbit around the earth you couln't deteriorate the speres orbit IN ANY WAY by jumping on the inside of the spere AS THE CENTER OF GRAVITY OF THE SPHERE AND YOURSELF REMAINS CONSTANT AT ALL TIMES

[ December 19, 2003, 08:21: Message edited by: JurijD ]