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Antimatter propulsion?

  1. Aug 20, 2015 #1
    hello everyone, i wasn't sure what category this should go under so General Physics was the safest bet.

    to my understanding when antimatter and normal matter collides its a 100% conversion into light, is this correct?

    if so, the conservation of mass says all the mass that was originally there is still there but instead of few atoms of antimatter and matter it is now millions upon billions of photons, is that also right?

    if so, in the future, near or far i don;t know, could we perhaps have a controlled reaction between the two in a engine of sorts that then directs these photons in a single direction using mirrors to achieve space flight?
    using the momentum equation m1v1=m2v2 if we wanted to get one ton to achieve escape velocity (11,000 m/s) we would need 19 grams of antimatter and another 19 grams of matter. because 1000(a ton in kg)*11000(escape velocity)=3*108(speed of light / speed mass will be travelling after reaction)*0.0367(amount of mass needed to balance equation)

    there's definitely something im missing, i know its hard to create and store antimatter and even harder to make something which can do what im asking but i feel as if i would of heard something somewhere if a project like this was in development, there's got to be a reason why it isn't, any details or information on this would be great, thanks.
     
  2. jcsd
  3. Aug 20, 2015 #2

    mfb

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    Not necessarily - it depends on the type of matter and the way they meet. Proton/antiproton (or in general hadron/hadron) collisions produce muons and neutrinos as well.
    That depends on the way you define "mass".
    There are no proper gamma ray mirrors, but something along this line could be possible, yes.

    The amount of antimatter needed depends on the mass of the spacecraft.
    All the antimatter created in the last decades wouldn't lift your rocket even by a centimeter. There is no realistic way to produce or store grams of antimatter in the near future. CERN experiments can store about 10-18 grams of (neutral) antimatter, that is 19 orders of magnitude below your numbers.
     
  4. Aug 20, 2015 #3
    iv read before that anti matter / positrons to be precise are used in medical PET and are produced by radioactive decay. what do you know of this and could we not gather it from this process rather than the LHC at CERN?
     
  5. Aug 20, 2015 #4

    sophiecentaur

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    To expect this to be a practical solution presupposes that a suitable 'bottle' could be made that would use substantially less energy to store this antimatter until it needed to be used, than the energy available from the 'drive'. It would be along the lines of using superconductors for power transmission in the absence of room temperature superconductors.
     
  6. Aug 20, 2015 #5

    mfb

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    Collecting positrons from radioactive decays would be possible, but even more inefficient than particle accelerator generated antimatter.
    Positrons all have a positive charge - as soon as you try to store relevant amounts of them the electrostatic repulsion becomes to strong. To store larger amounts, you would need positrons and antiprotons to form neutral hydrogen. The record is somewhere in the range of 1000 atoms over less than an hour. Far away from practical amounts.

    While the LHC produces antiparticles, those are not stored. The antiproton experiments at CERN use the smaller PS and SPS accelerators.
     
  7. Aug 20, 2015 #6
    Last edited by a moderator: May 7, 2017
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