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If the method for creating electrons and positrons from photons, as described in this article, were proven correct, would it be possible to use it for accelerating space ships – using only an energy source such as a nuclear fission reactor (as opposed to having to use a propellant)?

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It's important to note that electron-positron production is well-established for photons or charged particles above the threshold of ~1 MeV total energy. For high-energy charged particles which lose energy by generating "showers" of less-energetic particles, it's the usually the primary energy loss mechanism. Your link is suggesting a photon-photon collider experiment to search for a very specific type of pair production.

Apart from issues of geometry (how do you get the exhaust to go out the tailpipe?), if you had enough light to generate particle-antiparticle pairs, it'd be more efficient to use the light as propellant directly.

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Quick answer: No.

Not so quick answer: momentum conservation. You emit photons with momentum $\vec p$, your spaceship gets propelled with momentum $-\vec p$. When the photons get converted into pairs, they have the same momentum, your spaceship goes the same.

Now, I take you want to use the pairs as an ionic motors. You take the electron positron pairs and push them out with magnetic fields. Why would you want to use photons to generate them? The only reason is that you could use energy as fuel, and you don't have to carry around solid fuel. Except that you will need so much energy to generate your flow of particles that any battery capable of storing the energy will have to be huge.

And then is the efficiency of the process...

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Perhaps rather then to ride in a spaceship, we were to travel by the annihilating electron (the process that occurs when a subatomic particle collides with its respective antiparticle to produce other particles) must occur first such as 0.511 MeV from Solar Hydrogen to send the then electronic signal to another location for 1.02 MeV electron pair production in the reanimation sequence. Roughly to be vaporized by the hydrogen/sun and that electronic signal demodulated and recreated in a pair production.

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protected by Qmechanic Jan 9 '17 at 5:30

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