The whole point of using Railguns rather than conventional chemical propellants is that the effectiveness of a railgun is not limited by its size. You can make it as long as you want, and the projectile will continue accelerating along the entire length of it... this means you can make projectiles go faster than a conventional chemical charge gun, but it also means that you can stretch the barrel out as long as you want as the tradeoff for lower G-forces, rather than limiting the muzzle velocity.

E_kin = 0.5*m*v²

thus:

Assuming a projectile of mass 500g and a velocity of Mach 5 (in air) being 1650 m/s, we get a kinetic energy of 680 kJ. I have no idea what they will use as dampening material, but that's a lot of energy to dissipate all at once.

Is that really all you need to fire it, though? Nothing is 100% efficient; how much energy is lost?

Just random, speaking of efficiency: I got a good laugh in my hydrology class the other day when the book told me to assume my observation well was 100% efficient and had zero diameter. If only everything were that good.

No, it is not the energy required to fire it, you are correct in that regard. It is, however, the energy of the recoil that has to be dissipated by the gun carriage and the ship holding it. But I have to admit that I did not think this through any further, that is beyond the kinetic energy that the projectile will have (due to lack of time), and I'm not certain I could come up with a correct estimate, so I won't spew any more formulae unless I know what I say is based on more than meanderings of my thoughts.

"Actually, an orbital launcher has always been one of the objectives of railgun and scram cannon research. However, it may just take more energy to launch a reasonably-sized satellite with a railgun than the traditional way... that and the strong electric and magnetic fields produced during the launch would be likely to fry any of the more sensitive components on board.

Also lnh, sober up before posting. Just reading that sentence gave me a headache."

well you could launch supplies into orbit to be retrieved for use on the ISS, like food, water, etc.

also you have to consider the energy used to make the fuel, transport the fuel, build the rocket to burn the fuel, and the cost of the parts to build the rocket and cost of the facility to build the rocket and fuel.

Hell with the cost, we're gonns shoot shit into space with a RAILGUN!

How kickass is THAT? A frikking RAILGUN!

In theory, the current in amps you need to launch a projectile is...

sqrt((2(pi)*m*a)/((mu[0])*ln|(d-r)^2/r^2|)

I leave it up to you to figure out how many meters/second^2 a needs to be to reach escape velocity by the end of your barrel of arbitrary length, but in layman's terms, the energy you need is approximately 3.7 metric shitloads per kilogram of satellite.

well this one used 10.64MJ to reach 2520 m/s, now from the surface of the earth (at the equator i think) escape velocity is about 11 kilometers per second, another problem is at that speed atmospheric friction becomes a huge problem, alot of things will want to melt, wich generally tends to destroy whatever your trying to shoot up into space. Youde probably have to mount it a couple miles up where the air is thinner, even then it still might burn up

linkified

Skyhooks ftw.