Moving beyond gunpowder

Railguns. A scifi staple moving towards reality. When deployed, we will see them first in the Navy on ships; the power requirements are quite high and only a ship has the amount of power available to make this feasible.

The lab version doesn’t look particularly menacing—more like a long, belt-fed airport screening device than like a futuristic cannon—but the system will fire rounds at up to Mach 8, drawing on tremendous amounts of electricity to generate the current for each test shot. That, of course, is the problem with rail guns: Like lasers, they’re out of step with modern-day generators and capacitors. 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.

According to Dr. Amir Chaboki, the program manager for Electro-Magnetic Rail Guns at BAE Systems, “The power is available. The challenge is how you use it.” 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. The more daunting challenge is the force of the rail gun itself: A few shots can dislodge the conducting rails—or even damage the barrel of the gun.

While the 32-MJ LRG should start firing soon, it could take another 13 years for a 64-megajoule system to be built and deployed on a ship. The Marines, in particular, are interested in the potential for rail guns to deliver supporting fire from up to 220 miles away—around 10 times further than standard ship-mounted cannons—with rounds landing more quickly and with less advance warning than a volley of Tomahawk cruise missiles.

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. Which means that for now, rail guns are precisely like lasers in one crucial way: They’re Holy Grails, irresistible precisely because they’re out of reach.