# Rail Guns

Hi,

I was just wondering if a projectile that is launched with a rail gun exerts a force in the opposite direction on the frame of the gun itself?

Thanks,
Jason O

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Danger
Gold Member
You again? :tongue:
Hey, dude. Yeah, there's a recoil the same as with any other launching mechanism. The projectile exerts an inertial resistance to the magnetic fields, which in turn pushes against the coils.

Are you sure this is true for a rail gun? from what you are describing, it sounds like you are talking about a coil gun. The rail guns dont have any coils to push against, only the magnetic field produced by the parallel rails.

Danger
Gold Member
You're right; I was thinking of a coil gun. The same principle, however, applies to anything of a similar nature. The magnetic field still exerts an opposing force on the rails.

LURCH
Or to put it another way; the magnetic field pushes the gun and the projectile away from each other (I find that this conceptual image helps many people think more clearly about recoil).

In fact, since rail guns or Gause rifles have a much higher muzzle velocity than firearms (usually), they have much greater recoil. But, I do think that a Gause rifle or other magnetically propelled weapon would have slightly less kick than a firearm of the same muzzle velocity, because the projectile accelerates a bit more smoothly.

Danger
Gold Member
Good explanation of recoil, Lurch. I'll be using that in the future.

There are various articles in which it is stated that the rail gun has less recoil, but I can't see how this would be the case. Equal and opposite forces and all that.

Over the length of the acceleration, whether it be the sharp explosion of conventional propellant or the continual acceleration of the rail gun, the force would still be equal in the opposite direction to the accelerating round.

The only difference is that the mass of the rail gun barrel would be expected to be far greater than a standard barrel due to the electrics and magnets, and therefore would recoil less.

What I'd like to know is have they sorted out the problem of the heat generated by the friction of the projectile travelling up the barrel.

The main concern and block to progress at this time seems to be this.

Can they not tune the maglev part so that it steers the projectile up the barrel rather than by using friction?

Of course, this would require a fair bit more power, but the rail gun uses enormous amounts as it is, so whats a few million watts between friends.

Yes there will be an equal recoil force, however it will be along the stronger axis of the rails, whereas the force from the magnetic field will cause a bigger problem as it pushes the rails apart, causing them to bend.

In response to corkie, it's an interesting idea, but I would guess that it would cause disturbances in the magnetic fields, and the vacuum would surely have to break to allow the particle out of the gun. Besides, there is still the large amount of heat from the enormous current present.