Coil gun vs Rail gun (practical stand point)

[StargateMillennium]

I'm curious from a practical standpoint what one would have over the other. I understand how they work mechanically, but what is the practical differences between the two? The only one I can tell is that the rail gun would wear down faster due to the need for direct contact and the coil gun would just be more expensive and difficult to make and may require more power.

And if that's the case, would coil guns be the next step after rail guns? Or is it needlessly complex for something that provides no other benefit?

[thekillman]

Railguns: Simple design and operation. High wear rates, difficult to scale beyond a certain point.
Coilguns: Complicated design and operation. Low wear rates. Easier to scale, though size becomes an issue.


Railguns operate by electrifying two rails and using the lorenz force to accelerate a projectile. The issue is twofold:
-that same lorenz force works on the rails themselves. The barrel is much longer than the thickness of a bullet. Your gun wants to tear itself apart, meaning it needs to be more and more reinforced with greater energy.
-The electricity running between the rails can easily ionize the air. the friction of the bullet generates heat, making ionization even easier. Beyond a certain point, you've made a plasma gun. And unlike Scifi, those are very ineffective. However, you can pump more current through the gun in order to fire faster bullets, so length of rail is not necessarily as limiting.

Coilguns operate by using magnets to attract a bullet, then shut them off. The next set of magnets then attracts the bullet. The issue is once more twofold:
-Magnets do not turn on and off instantly. Induction means that turning off the magnet will take time, and the stronger the magnet, the longer it will take. So when the bullet has passed through the magnet, the magnet is still on and will slow down the bullet. Clever design will be needed to minimize this.
-The above will also mean that to achieve a certain speed, you need a certain length of coilguns. As the bullet goes faster, the on/off switch needs to be faster. This means huge diminishing returns, and so increasingly cleverer and more complex machinery. Longer barrels will also be increasingly needed.

But essentially, Railguns scale better at the lower end of the spectrum (up to a few Km/s), while coilguns can go well beyond that yet will hit size issues.

And if that's the case, would coil guns be the next step after rail guns? Or is it needlessly complex for something that provides no other benefit?

The main benefit for railguns is that you can fire solid chunks of metal. This makes munitions storage easier and safer. The main weakness of a ship is the munition chamber, since if that's hit then a massive explosion is likely. Coilguns will be too complex for the same level of firepower, though they might find some uses.

Still, the main argument for conventional arms is simplicity.