THE railgun sends a 20 pound projectile rocketing through the air at seven times the speed of sound Navy scientists have set a world record during a test of an electromagnetic railgun, a hi-tech cannon that sends a 20-pound projectile rocketing through the air at seven times the speed of sound. The supergun, which can destroy a target 100 miles (160Km) away, has officially been branded the most powerful in the worldafter tests at a U.S. Navy firing range. The futuristic gun was tested twice at the Naval Surface Warfare Center in Dahlgren, Va., and the first shot generated 33 megajoules of force out of the barrel. One megajoule is a unit of energy roughly equal to the energy generated by a 1-ton vehicle moving at 100 MPH, to put this into perspective. Instead of relying on explosive propellants like gunpowder to fire, the gun uses a giant surge of electricity to propel the slug out of the barrel at crazy speeds. MD