Three years ago, then-Chief of Naval Operations Jonathan Greenert declared that railguns — which fire projectiles with electromagnetic pulses rather than gunpowder — had come so close to battle-ready that he wanted to test-fire one at sea. Since then the Navy has changed course, deciding that permanent land-based test sites would provide more and better data for fewer dollars than an ad hoc installation aboard a repurposed fast transport (variously known as JHSV or EFP). So on November 17, along the Potomac River at the Naval Surface Warfare Center in Dahlgren, Va., a new 32-megajoule railgun built by BAE Systems opened fire for the first time. (See video above). A second railgun is being set up at the Army’s White Sands Missile Range in the New Mexico desert, where there’s enough wide-open space to fire the weapon at its maximum range of more than a hundred nautical miles.