The railgun utilizes two metal rails that, when under a electrical current, utilize the Lorentz force to accelerate a metal projectile to super sonic speeds.

In light of this, Can the rails be replaced with plasma instead?

Seeing as plasma also carries an electrical current, I wonder if such a design is possible, how it would work and what would its performance be.

Edit: The way I envision such a system working is to use short range high intensity laser pulse to ignite the air to create the plasma and use that to launch the projectile before the plasma dissipates. The main reason for this is that while it is true that the plan ads would get blown out, it would be easier to repeat the cycle and have a consistent rate of fire instead of having to replace the rails after wear and arc damage. Of course this is my idea and I’m not sure this could work or if there are better designs out there.

  • $\begingroup$ How would you contain the plasma to keep it in the two-parallel-rails configuration? $\endgroup$ – Patricia Shanahan Nov 19 '19 at 3:58
  • $\begingroup$ Who says it needs to be contained for long? $\endgroup$ – Seraphim Nov 19 '19 at 5:08
  • $\begingroup$ Accelerating charged particles is maybe the easiest thing ever. However, if you have an ultra low density bullet, that's what that is, you will get very little bang for your buck. People want heavy bullets. $\endgroup$ – Raditz_35 Nov 19 '19 at 5:25

Can the rails be replaced with plasma instead?

The wear and tear in a railgun is largely due to bits of the rails being replaced with plasma. Such is the result of striking an arc and running that much current through it.

I had a think about a plasma-rail gun a while back and more or less discarded the idea, because what you end up with is the need to stabilise the projectile (so you shoot straight) and accelerate the projectile and retain the plasma rails for as long as it takes for the projectile to sweep through the barrel. You can't physically contact the projectile (because the arc will erode whatever you have in contact with the projectile, taking you back to square one) leaving you with the unenviable task of having three different and quite powerful electromagnetic effects in the same small volume all trying to do different things.

That's not to say that you couldn't handwave the technical issues out of the way. I'd use a cold (non-thermal) plasma as the rails though, which will be much easier to interface with than the hot kind (you can stick your hands in a low-density cold plasma without will effects, for example). It does imply a fairly high level of technology, though.

  • $\begingroup$ How high are we talking? Regular use and grasp of fusion power advanced? $\endgroup$ – Seraphim Nov 19 '19 at 16:06

Yes, it could, but the question is why. Plasma either destroys whatever it touches, or cools and stops being plasma when it touches things. So you need to do what fusion reactors do, and contain the plasma with powerful electromagnets, not just a durable container. But then you could just use the same magnets to push the projectile. Remember, whatever force the plasma applies to projectile will be applied to the plasma as well, and if you want to keep the plasma contained, the magnets must be able to counter it. So why not just cut out the middle man and use the magnets to push the projectile directly?

  • $\begingroup$ this, very much. The plasma is a huge extra expenditure of energy for absolutely no gain. it is a large net loss. $\endgroup$ – John Nov 19 '19 at 6:06
  • $\begingroup$ If you can control the magnetic field to the point that you can make a rail out of plasma, why do you not also make the bullet out of plasma as well? Turn your rail gun into a lightsaber that shoots its blade $\endgroup$ – Nam Nguyen Hoang Nov 19 '19 at 9:52
  • 1
    $\begingroup$ @NamNguyenHoang because confinement in an an object which you control and can supply large amounts of power to is rather different from supplying power to a small fast moving object that you're not connected to. $\endgroup$ – Starfish Prime Nov 19 '19 at 10:46
  • $\begingroup$ Ok, I guess that's fair $\endgroup$ – Nam Nguyen Hoang Nov 19 '19 at 10:47

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