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I Spacecraft design

  1. Aug 26, 2016 #1
    What about the attached as a means of propulsion? It would be a spacecraft with a long magnet in the front. Attached on one side by boons the magnet would have a reflector/deflector or shield of some type e.g. aluminum. In interstellar space there would be charged cosmic particles moving in random directions. Given that charged particles are deflected perpendicularly to their trajectory, and per the right hand rule it would be in a uniform direction. So, would this generate net thrust for the spacecraft? Obviously the benefits would seem to be many... such as not needing to take propellant, being shielded to some extent by radiation, and...hmmm not needing to bring your own energy? momentum would be conserved.
     

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  3. Aug 26, 2016 #2

    berkeman

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    Staff: Mentor

    Thread closed temporarily for Moderation...
     
  4. Aug 26, 2016 #3

    russ_watters

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    What you propose, if possible, would be a perpetual motion machine. It can't work because it would require a biased/monopole magnet to only direct particles in one direction. There is no such thing.

    Since we do not allow discussion of perpetual motion machines, this thread is closed. I recommend you peruse this site for more information on general concepts and explanations of similar unworkable devices (like the permanent magnet motor):

    https://www.lhup.edu/~dsimanek/museum/unwork.htm
     
  5. Aug 26, 2016 #4

    berkeman

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    After extensive Mentor discussion, we believe that there are some important points that can be discussed about the OP's question. Thread is re-opened for those non-PMM discussions. :smile:
     
  6. Aug 26, 2016 #5
  7. Aug 27, 2016 #6

    mfb

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    The flux of cosmic rays is tiny. While it is not completely impossible to use them to get some net force, a device as simple as your sketch doesn't work - for every particle deflected in one direction you would also have particles deflected in other directions. And if you try to stop those, you stop the other particles as well.


    Here is an extremely inefficient approach that generates net thrust: Make your spacecraft out of (ideal) material that absorbs all incoming particles that hit it anywhere. Have a single curved tunnel go through the spacecraft, with a uniform magnetic field parallel to the curvature vector, the magnetic flux return happens somewhere inside the spacecraft. The spacecraft absorbs radiation uniformly apart from two exceptions: (a) electrons with a specific velocity entering at one side, passing through the tunnel and getting deflected towards the center of curvature, and (b) ions entering at the other side with a type-dependent specific velocity, passing through the tunnel and getting deflected in the same way.

    If the spacecraft is in a frame with isotropic flux, it produces a bit of net thrust: half of the momentum change in the tunnel (the other half is balancing the lack of absorbing particles coming from a particular direction).

    If the spacecraft has some speed relative to the frame of isotropic flux already, then the absorption will slow the spacecraft, and the flux of particles going through the tunnel goes down a bit - the spacecraft has some limited maximal speed that depends on its geometry and details of the particle flux. Note that during the acceleration process, in the frame of isotropic flux, the spacecraft slows down some particles (those going through the tunnel) that fly in the direction of the spacecraft more than simple absorption would, which provides both energy and momentum.

    The overall forces are completely negligible.
     
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