jsprogrammer has the merit of having actually done
some calculation, which you evidently have not — although if you think resistance is a thing that inductance can have, maybe you are not in a position to do any calculations. Either way, you should rethink your attitude.
Naval railguns don't have the luxury of accelerating over hundreds of kilometers; they are optimized for muzzle velocity, not efficiency. The things I've seen videos of launch projectiles at about Mach 7.5 (2500 m/s) over about 7 meters. That implies an average acceleration of at least 45000 gees, which means that you're going to have to accept significant inefficiencies that you can avoid in a design that accelerates three thousand times more gently.
In practice, both rotary and linear electric motors typically have efficiencies of over 80%, often over 95%. The proposal in question is a 200-km-long linear electric motor running up the side of a mountain. It's clearly feasible, but it won't cost pennies per launch.
You do need to partially evacuate the launch tube to shove your launch vehicle through hundreds of kilometers of it.
It is not plausible that a naval railgun uses only 28 megawatts. Traveling 7 meters at an average of Mach 3.75 takes 5.6 ms; if the total energy output is 64 MJ, that's an average of 11.3 gigawatts†, which is a lot more than 28 megawatts or for that matter 78 megawatts. So what you do is you charge a big low-ESR capacitor bank (at less than 78 megawatts) before the shot, then discharge it during the shot (at tens of gigawatts). If you're doing that, though, you have no limit on how many railguns you can run from your 78 MW power plant, just a limit on how many total shots per second you can fire among all of them. Your entire paragraph on the topic is incoherent nonsense.
For comparison, a .22 LR 30-grain (1.94 g) copper-plated hollowpoint bullet traveling at 500 m/s out of a 510 mm AR-15 barrel only has at most 2 ms to accelerate to its final 240 J energy and therefore requires over 120 kW of power.
Classical mechanics are perfectly adequate for all of this. No relativistic or quantum effects are relevant. Your suggestion otherwise is absurd.
Calculations in units(1) format for those who want to check them:
(mach 7.5)^2/2 / 7 meters / gravity
7 meters / (mach 7.5/2)
64 MJ / (7 meters / (mach 7.5/2))
30 grains
510 mm / (.5 500 m/s)
30 grains (500 m/s)^2/2
30 grains (500 m/s)^2/2 / (510 mm / (.5 500 m/s))
† With constant acceleration the power output ramps up linearly and ends up at twice the average. With constant power the acceleration ramps down instead, which means that you have to start out at even higher accelerations to get the same average acceleration, and your total time in the barrel is shorter, so your average power is higher, although I don't feel like doing the simple calculus to quantify this at the moment. In either case you have at least a point where the power is a few times higher than this average.