In my sci-fi universe, there are two types of energy weapons: plasma cannons, and particle beam weapons. The way things currently are is that energy weapons are space-based, because they don't work in the magnetic field of a planet. Of course, this also leads to ships having magnetic shields, to negate the weapons. This works with plasma, the shield cancels out the magnetic containment of the plasma, which causes the plasma itself to dissipate and lose energy. It might still do something when it hits the hull, but not as much as a regular bolt would. But what would it do with particle beam weapons? would it negate them, soften the blow, do nothing, or something else? If nothing, what would work as shielding against beam weapons?

This universe is built on both real-world and theoretical science with a little bit of hand-waving and rule of cool, so I guess a kind of "firm" science, but I want the science of the tech to be as based in realism as possible.

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    $\begingroup$ If the particle beams use charged particles, then it's affected just as plasma, which is also composed of charged particles, is. If the particle beams use neutral particles, then the magnetic shielding has no effect and you need to resort to good, old-fashioned armor. (Of course, this ignores the fundamental issue with both plasma and particle beams where dispersion from electromagnetic repulsion and thermal kinetic dispersion give them about as much effective range as a spitball.) $\endgroup$ Jul 21, 2021 at 3:43
  • $\begingroup$ That’s what I was thinking, that a charged particle beam would be repelled. I could probably think of a way to explain why one is used and not the other, and is it reasonable to assume that the technology might exist, thousands of years from now, that would give them a longer range? My space battles aren’t being fought on a huge scale, like what a hard science battle would be, so if they could theoretically have a maximum range of a couple hundred kilometers that would work perfectly, lol. $\endgroup$ Jul 21, 2021 at 13:27
  • $\begingroup$ On the surface of Earth, the magnetic field is very weak. So ship's should be easily protected because they could generate this trivial field? $\endgroup$
    – NomadMaker
    Jul 21, 2021 at 14:51
  • $\begingroup$ @GrumpyYoungMan (may I call you Grumps?) your comment is the answer so you should post it as one. Because if I do, after your comment, then I feel shamefully derivative. I am ok with that feeling as regards AlexP but I feel the need to contain it somehow. $\endgroup$
    – Willk
    Jul 21, 2021 at 16:49
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    $\begingroup$ @Willk Being only a couple of sentences I didn't think it was worthwhile but, since you asked, I'll create an answer. As an aside though, I don't mind if people create answers that cover what I say in comments; often I'll provide information in comments because I don't have the time to develop a full-fledged answer. $\endgroup$ Jul 21, 2021 at 20:11

1 Answer 1


It depends on the type of particle beam.

  • If the particle beam uses charged particles (protons, ionized atoms, etc., then it's affected by the magnetic shield in the same way as plasma is, since plasma is itself charged particles (ions).
  • If the particle beam uses neutral particles (neutrons or neutral atoms), then the magnetic shielding has no effect and you need to resort to good, old-fashioned armor. There has been ongoing research about creating neutral particle beams for weaponry (e.g. https://www.popularmechanics.com/military/weapons/a26858944/pentagon-particle-beam-space-2023/ ) but nothing practical has emerged from it yet.

(As an aside, there are fundamental issues with both plasma and particle beams that, as far as we know today, make them difficult to use as spacecraft weapons:

  • Electromagnetic repulsion: plasma and charged particle beams tend to fly apart because the charged particles that makes up the beam repel each other powerfully, causing the beam to expand.
  • Thermal expansion: Even if neutral particles are used, the beam is still a large quantity of particles in close proximity which are thermally "hot", such that collisions by particles within the beam also cause the beam to expand, much like gas coming out of a air compressor.)
  • $\begingroup$ Could you make a plasma of equal protons and electrons to keep the beam together? I am very much not a physicist as you can probably tell :-D $\endgroup$ Jul 22, 2021 at 10:30
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    $\begingroup$ @Whelkaholism Most plasmas classically studied do have roughly equal proportions of electrons and neutrons--this is known as quasineutrality (charged particle beams need not have this property, as they are normally a single type of particle). The main thing that causes classical plasmas to expand is actually the OPs second point (thermal expansion). This is because particles in classical plasmas have a thermal energy that dwarfs the electrostatic potential between particles (a condition known as weak coupling). This is likely to be the case for any plasmas you'd be shooting out of a cannon $\endgroup$ Jul 23, 2021 at 16:04
  • $\begingroup$ Oops, I meant to say equal amounts of electrons and protons, not neutrons $\endgroup$ Jul 23, 2021 at 17:27

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