Eight and 9-megajoule rail guns have been fired before, but providing 3 million amps of power per shot has been a limitation. At 32 megajoules, this new system appears to be the most powerful rail gun ever built, and the Office of Naval Research is installing additional capacitors at the Dahlgren facility to support it. The planned 64-megajoule weapon, if it’s ever built, could require even more power—a staggering 6 million amps.
The Navy’s electrically-propelled DDG 100 Destroyer, Chaboki says, is a prime candidate for the final 64-megajoule system. Around 72 megawatts (MW) of the vessel’s power can be used for propulsion. But during combat, the destroyer’s speed could be brought down, freeing up energy for a rail gun. Chaboki calculates that firing the 64-megajoule weapon six times per minute would require 16 MW of power, which would be supplied by either onboard capacitors or pulsed alternators.
Effective rail guns will require a major breakthrough in materials between now and 2020, to keep the guns themselves from being shredded by each high-velocity barrage.
There was a 2003 analysis of using railguns for orbital launches.
For launch to orbit, even long launchers (>1000 m) would need to operate at accelerations >1000 gees to reach the required velocities, so that it would only be possible to launch rugged payloads, such as fuel, water, and material. A railgun system concept is described here and technology development issues are identified. Estimated launch costs could be attractively low (<$600/kg) compared with the Space Shuttle (>$20 000/kg), provided that acceptable launch rates can be achieved.
A european space agency study of rail guns for space launches
A system to launch single stage rocket propelled projectiles to put in orbit nano-satellites using a 3.4 GJ railgun with a length of 180 m.
Ram accelerators would be cheaper and quicker to develop for gun launching payloads into space.
Superthread carbon nanotubes would be the kind of material needed to help reinforce the rail gun
There is other progress being made on better materials including nanograin metals.