The US Navy has been working on an electromagnetic railgun and demonstrated it on December 10th, 2010.  Instead of traditional gunpowder to propel the projectile, the Navy did it with electricity.  Classed as a 33 megajoule shot, the ONR (Office of Naval Research) described a megajoule as the power needed to propel a one ton vehicle at 100 mph.  The projectile wouldn't even need a warhead, as the kinetic energy at speeds seven times the speed of sound would be enough to destroy the target. And the gun can hit targets  110 nautical miles away.

This ability to shoot a projectile and destroy a target without explosives is attractive to the Navy for safety concerns. The US Navy still remembers the Arizona exploding at Pearl Harbor, and eliminating a magazine full of powder increases the safety of the ship and crew.  Being able to float huge powerplants on board ship also helps feed the railgun with all the power it could possibly use.