[jzwinck]

You don't need to imagine, we can compute it!

Mach 7 is 2382 m/s. 23 pounds is 10.4 kg.

Since k=mv^2: (1/2) * (10.4 kg) * (2382 m/s)^2 = 29504404 Joules.

That's 29.5 MJ, which is 29.5 megawatt-seconds. So it could mean 29.5 megawatts for one second, except of course the rail time is much less than one second. But who cares, let's convert to household units! 29500 kilowatt-seconds is 8.2 kWh. At an average price of US$0.13/kWh, that comes to just $1 worth of electricity to fire a $25000 projectile.

Oh, yeah, the losses. Those are probably 90% or so, so let's say $10. And mark it up a factor of ten because the electricity is on a boat, so $100, and a factor of 50 because it's a weapons system. So ballpark $5000 in electricity TCO to fire the $25000 projectile.