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My Antimatter Rocket

  1. Aug 27, 2011 #1
    To put it short, I'm designing an antimatter rocket that a guy at NASA want's to see. I'm working hard but had a few questions for you guys:

    1. What's the easiest way to get Positrons?
    2. Any ideas on either storing it for a month or having a machine keep feeding the engine positrons like a portable accelerator or cyclotron or something?
    3. When crashing into the water after the engine is ejected into orbit, does it matter that much if the rocket is aerodynamic on the way down or does it only matter when the rocket launches?

    Thanks for the help,

    -Lazer
     
  2. jcsd
  3. Aug 27, 2011 #2

    phinds

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    I seem to remember reading recently that a small amount of anti-matter had been stored for 15 minutes and that was considered quite amazing.
     
  4. Aug 27, 2011 #3

    Astronuc

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    Staff: Mentor

    There is no easy way to generate positrons. The can be produced by interaction of gamma rays of minimum 1.022 MeV with a nucleus of an atom in the so-called pair production. However, such positrons slow down in surrounding media and anihilate into 2 0.511 MeV photons. They can be produced by decay of certain proton-rich nuclei, or they can be produced in electron colliders.

    http://www-project.slac.stanford.edu/lc/local/systems/Injector/PositronSource.htm
    http://www.positronannihilation.net/index_files/Positron-Sources.pdf

    http://www.slac.stanford.edu/exp/e166/

    POSITRON SOURCE OPTIONS FOR LINEAR COLLIDERS
    http://accelconf.web.cern.ch/AccelConf/e04/PAPERS/TUZACH01.PDF

    Charged particles are generally not stored in cyclotrons, but rather storage rings, which store charge particles rather than increase the energy.

    It is unlikely to develop effective portable storage devices for positrons.

    Like a rocket motor will burn up in the atmoshpere. The main tank of the shuttle, as aerodynamic as it is, burns up in the atmosphere - usually over the Pacific Ocean.

    A positron anihilation reaction creates 0.511 MeV gamma-rays, and likely the energy density would be fairly low. That doesn't bode well for launching from the surface of the earth, where high thrust (and low Isp) are essentially required.
     
  5. Aug 27, 2011 #4
    Obtain a large sodium-22 source (as per Astronuc) . It emits a lot of positrons (about 90% efficiency). Lifetime is about 2.6 years. See decay scheme in Fig 3.11 on page 8 of

    http://mightylib.mit.edu/Course%20Materials/22.01/Fall%202001/decay%20mechanisms.pdf [Broken]

    1 microamp of positrons requires about a 200 Curie source. You will need a license for anything above a few microCuries.

    This is not suitable for rocket propulsion, unless you can figure out how to accumulate the emitted positrons.

    Before you do anything else, use Newton's equations to calculate the rocket thrust. Also figure out how you might store 1 Coulomb (antiCoulomb?) of positrons.

    Bob S
     
    Last edited by a moderator: May 5, 2017
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