Rail Gun

I feel much better now that I've made up my mind about politics. Barring unforseen emotional and/or ethical catastrophes, Barack's got my vote. Now I can think about other things, like this:

http://news.aol.com/story/_a/navy-tests-high-tech-railgun/20080131154909990001?ncid=NWS00010000000001

Good heavens. I'm tempted to ask "why" but I already know why: because they're Guys, and Guys think rail guns are cool. Hell, I'd love to have a rail gun!

The main feature of rail guns is the incredibly high velocity of the projectile. The projectiles are so fast you don't even need to put an explosive in them - when your RV takes a 6mm Lexan projectile up side the head at five kilometers per second, you don't need no stinking explosives; raw kinetic energy gets the job done.

But why? What can a rail gun do that a conventional gun can't?

Here's the main difference. In a conventional gun, you burn some amount of powder in the barrel of the gun, which releases a lot of hot gas that pushes the shell out of the gun. The pressure inside the gun is very high and the impulse on the shell is also quite high. And if you want to make the gun shoot farther, you have to worry that the gas pressure might rupture the gun or cause the shell to collapse in the bore.

A rail gun doesn't subject the projectile to a single momentary impulse. Instead it accelerates the projective smoothly during the entire time it's in the rail. There is no freakishly high gas pressure to deal with, acceleration loading is reduced, and all other things being equal, the rail gun will fire a projectile at a much higher velocity. (In practice, there are problems with rail guns too. The design I'm familiar with works by first vaporizing a thin layer of aluminum on the back of the cylindrical Lexan projectile. This allows the high voltage between the rails to arc over, and then by the immutable laws of electromagnetics, including that three-fingered deal that today looks like some thug shooting a gang sign, the arc sends the projectile off down the rail. But it requires good isolation, good capacitors, good switching, and woe betide the rail gunner who lets a hair or a piece of dust bridge the gap between the rails.) If you want your rail gun to shoot farther, you just charge the batteries longer, so to speak.

My sense is that rail guns may have utility in space where the projectiles are not subject to aerodynamic heating, but that modern guns are already plenty powerful enough for everyday use, thank you very much, and a 155mm howitzer is a considerably tougher and more mobile apparatus than a rail gun.

Who here remembers the old Safeguard ABM system? It consisted of two different missiles, the long-range high-altitude Spartan and the short-range terminal-defense Sprint. Sprint accelerated off the pad at 100+ gees and within a few seconds of flight the nose cone was glowing red hot and the missile itself was completely encased in a sheath of incandescent plasma caused by air resistance. That's what a rail gain would do to its projectiles, especially if someone made a mistake and set it to "11".

I think we can put that down in the "fiscally irresponsible and tactically irrelevant but oh so boss all the same" column.