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Recently, when reading about atomic rockets, I noticed an entry about spin-aligning neutrons to make them shoot out of the rocket's nozzle instead of randomly flying around to wreck the rocket.

Neutrinos, like neutrons, are uncharged, so they can't be aimed using electromagnetic fields, either.

What I noticed is that, since neutrinos also should have a very tiny momentum, wouldn't they also get emitted in the exact opposite direction of something (my guess is that for beta decays it should be the electron on one side, the antineutrino flying out the other direction, but I know nothing so I'm probably wrong) to conserve momentum? If that's the case, then could whatever they fly out of be aimed so as to ensure that the neutrino is aimed at something?

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  • $\begingroup$ Do you mean "neutrons" or "neutrinos"? Your question uses both. Reactor neutrinos would not "wreck" a rocket, but a pure beta emitter isn't a good rocket power source anyway. Reactor neutrons are a very different animal. Consider linking to the article you read. $\endgroup$
    – rob
    Commented Jun 7 at 22:06
  • $\begingroup$ well the neutron part was referring to the article on atomic rockets that inspired me to have a thought on aiming neutrinos, but the question is only about neutrinos, here's the article I read: projectrho.com/public_html/rocket/torchships.php#spinalign $\endgroup$ Commented Jun 8 at 2:16

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Neutrinos interact so seldom that it is not possible to align them after they are created.

The DUNE experiment at FermiLab does create a beam of neutrinos. They actually create a beam of protons. Then they smash the protons into a target, producing pions.

Charged pions are can be steered with electromagnetic fields. They are aimed at a detector, usually a distant one.

The pions decay into a muon and a neutrino going in the same direction as the pion. These run into a wall before hitting the detector. The muon stops, but the neutrino keeps going.

See How do you make a neutrino beam?

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  • $\begingroup$ Ah I see...so the protons are aimed to hit a target, the protons produce pions which can be aimed, aim it at a target then wait for it to decay to muon+neutrino? clever...thanks for the link $\endgroup$ Commented Jun 8 at 2:20
  • $\begingroup$ @General_Ripper Right. In the pion rest frame, the muon & neutrino are emitted with equal & opposite momenta in some random direction. But in the lab frame, that means the neutrino & muon vectors are roughly aligned with the pion vector. This technique works best when the pion speed is close to c, because detectable neutrino speeds are ultra-relativistic. I have some info on that here: physics.stackexchange.com/a/795389/123208 $\endgroup$
    – PM 2Ring
    Commented Jun 8 at 3:43

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