Are Gauss Guns railguns OR coilguns?

[doctorevilbrain]

That's not the impression that I've got from reading Ultra Tech.

[Strategos' Risk]

Regarding the difficulties of creating a working coilgun- what happens when the magnetic coils fail to switch at the right time as the round is traveling through it?

[Varyon]

Originally Posted by Strategos' Risk

Regarding the difficulties of creating a working coilgun- what happens when the magnetic coils fail to switch at the right time as the round is traveling through it?

From my understanding, the coils serve to attract the projectile and pull it forward. Turning off too early means the projectile isn't pulled forward for as long, while failure to turn off at the right time will mean that the projectile starts to decelerate (due to the coils now pulling it backward). In both cases, that's going to slow down the projectile. Turning on too early in and of itself I think would just waste energy - but as many coilgun designs are reliant on capacitors that need charging, this will likely result in the coil turning off early due to the capacitor being emptied too soon. Due to the way these need to be designed, any issue here tends to compound on itself with later coils - if the first coil turns off too early or too late, the projectile is slowed down, and thus isn't in the right position (or going the right speed) when the next coil turns on, resulting in it functionally turning off too early, then this happens to the next one, then the next, etc - with enough coils, you might wind up with the projectile coming to stop or even being propelled backward a bit.

That assumes you have the coils working off timers. It might be possible to have something set up that detects the location of the projectile, turning the coil on when it reaches a certain point in the barrel and off when it reaches another (basically right in the middle of the coil if I'm understanding things correctly). Provided you design the capacitors to hold a larger charge than they need for typical operation, that would probably be more forgiving of early errors (you'd still wind up with a slower projectile at the end, but not to the same extent). I don't know how difficult it would be to design such (or if you even could), nor how much extra weight and power requirements you'd be adding on, but it might be an option.

However, I assume that with either version, having the projectile "float" rather than being in contact with the barrel would call for absolutely exacting precision, as any wobble will result in it veering off and coming into contact with the barrel wall. Something that uses the magnetic coils to push rather than pull it would probably be more conducive to having a "floating" projectile. I think that calls for the projectile to itself be a magnet (permanent or electromagnet), while the "pull" variant just needs it to be ferromagnetic.

[Anthony]

Originally Posted by Strategos' Risk

Regarding the difficulties of creating a working coilgun- what happens when the magnetic coils fail to switch at the right time as the round is traveling through it?

By itself, one coil (out of many) not working correctly is probably tolerable, but there's a risk it throws the stability of the whole system off, with results up to and including the projectile impacting the side of the barrel and the whole system needing to undergo major repairs.

[johndallman]

Originally Posted by Strategos' Risk

Regarding the difficulties of creating a working coilgun . . .

Working coilguns exist (Forgotten Weapons video), although they're very low-powered.

[Strategos' Risk]

Thank you all for your information. It greatly helped for the writing of this.

[FrackingBiscuit]

Originally Posted by Anthony

The latter is what GURPS calls electrothermal or electrothermal-chemical.

The weapon in the video in question is an electromagnetic rocket gun, a railgun with a projectile containing coolant/propellant. Heat from the railgun evaporates the propellant, which is ionized into a plasma. In contrast, an electrothermal-chemical gun uses a pulse of plasma to combust conventional propellant. They have some similar operating principles, but they're not the same thing, and GURPS is not referring to EM rocket guns when it talks about ETC.

Note also that pure electrothermal guns (as in, not electrothermal-chemical guns) are also a separate thing, which uses a plasma pulse and an inert propellant like plastic flakes or water rather than gunpowder.