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Confusion about how the momentum is transferred

  1. Jul 13, 2012 #1
    I'm thinking of non pyrotechnic ways to make changes in the velocity of a satellite in space and my concepts here might be totally wrong, but i wondered if transfer of momentum might work.
    That is, as in the first image if i have a small mass compressed by a spring and i release it later by some mechanism so it springs away from the satellite, will i succeed in reducing the speed of the satellite? i know i might affect the moment of inertia of the satellite but what could the effects be if i have magnetotorquers to stabilize my satellite.
    My professor dismissed it after ten seconds of listening to it and didn't explain why.

    also, I read about the inter satellite separation mechanism the canX 4/5 used and i might not have understood the working fully but this is what i think they have done to separate the satellite.
    They used an electrical debonding epoxy sold as ElectRelease to hold two plungers (one whose tip is a cone and the other whose tip is a cup. When current is passed the bond breaks and the belleville springs decompress and pull the plungers away from each other till it hits against the base plate shown by aluminum. you'll notice in the last picture of the second image theres a millimeter gap between the plunger and the aluminum base; this is the mechanism when it is loaded with the epoxy. when it gets debonded the springs expand and the plunger jumps back. the aluminum base is connected to the satellite face by the four screws and the belleville springs and the plates shown in red (called push plates) all sit inside the satellite(the link: https://tspace.library.utoronto.ca/bitstream/1807/31620/1/Urbanek_Jakub_201111_MASc_thesis.pdf it's explained properly here)
    my question is, in this mechanism, are the satellites going to move away from each other with however small a relative velocity? (taking a ideal case neglecting effects of drifts) or will the satellites just separate and stay there?

    Attached Files:

  2. jcsd
  3. Jul 13, 2012 #2


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    If you emit the ball in forward direction, yes. However, what is the advantage of this mechanical system? There are conventional systems which have a better thrust to mass ratio (rockets, or if the system should be really small just compressed gas), and if you have enough time an ion drive is even better.

    If you separate two satellites with a "kick", they will continue to drift away. Their different orbits will change their relative movement within the timescale of the orbital period.
  4. Jul 13, 2012 #3
    Thanks, you're right there are much more practical systems.
    It's a small system and we were just discussing ideas. They wanted something original, something that hadn't been done before so i suggested this. and the prof made me feel the physics might be wrong.
    In the ISS system i wasn't sure if this mechanism causes them to move away at all. the plunger is thrust inwards so i think if anything they should move towards each other....?
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