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Centripetal Space Stations

  1. Nov 10, 2009 #1
    I'm doing a project on being able to create Earth like conditions in space. Basically its artificial gravity on space stations.
    I have a few thoughts and I just need to know if they're right so I don't go wandering a long a path and find out its the wrong one!

    I'm mostly using the concept of rotating space station, with people sticking to the edge.
    First of all I'll need to use equations for circular motion, the centripetal acceleration:

    a = v^2 / r

    and for people to feel Earth-like gravity, the acceleration will need to be 9.81 ms^-2, the acceleration due to gravity.

    Now, something I'm not sure about. Does the mass of the space station make a difference? Would I only be using mass in equation if I was calculating the centripetal force (m*v^2 / r) for an object with mass "m" inside the space station?


    Also, I was thinking of how you could actually get the station to rotate. Currently satellites have rockets so they can blast themselves in to the right orbit if they start to wander. But I don't like the idea of having rockets, I thought of something else.
    Space Station 5 from 2001 is a good basis for what I was thinking. It has 2 rings.
    I thought it would be possible to make one ring rotate the other. It is on Earth, tie a wheel to a motor and the wheel spins. But if the motor is on one ring, rotating the other, what is to stop the motor ring rotating? Nothing.
    So if the motor at the centre of Ring A was to rotate an identical Ring B at twice the velocity required for the aritifical gravity then both rings would move, in opposite directions at the same speed. Ring A relative to Ring B is rotating at the same speed as the motor but its actual speed is half that because half the motor is using half the energy to rotate itself (and Ring B)

    So ignoring the fact construction of such a thing would be hard and expensive, is that what would happen in theory? If Ring A + Motor = Ring B (or would their masses not make a difference?)

    I'm wondering because I don't think I've read any concepts like that, most things I've read just state that "it rotates", so I'm thinking I may have missed something obvious and don't want to put it in to my project if its totally wrong.
  2. jcsd
  3. Nov 10, 2009 #2


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    Staff: Mentor

    The mass of the person and the space station do not matter for your calculation. You are just duplicating the acceleration due to gravity with your centripital acceleration due to rotation of the space station.

    Interesting idea for creating the rotation. That way you can create it and manage it all with electrical power from solar panels. Two issues would be tying the two sides together electronically (probably could use an RF coupling), and how to make a good atmospheric seal between the two halves that are counter-rotating and the outside vacuum...
  4. Nov 11, 2009 #3
    berkeman is correct.
    Also, your rotation theory utilizes conservation of angular momentum, which I am sure you can find tons of material on.
    I am not really clear on your question on that part due to the wording. But the masses of each part absolutely do play a central role.
    This is the same principle that Gyroscopes use in space craft orientation.
  5. Nov 11, 2009 #4
    I found something similar to what I was thinking of and it actually used. I was thinking of a Reaction Wheel, the ones they use in spacecraft are small motors inside the craft. Spin the wheel fairly quickly one way, the craft will rotate (slowly, its bigger than the wheel) the other way.
    Good to know its possible and that they actually exist!
  6. Nov 12, 2009 #5
    Well done! Glad as a questioner that you took the initiative and did your own research. It's saddening just how many people don't. They have a world of knowledge at their finger tips if they would but ask the right questions.
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