The operator set up the laser cannon on the roof of his pickup truck in the middle of an empty field. It resembles a hobbyist’s telescope with some cameras affixed to the sides. For target practice, one of the engineers launched a small drone, and it flew a few hundred yards away from us, hovering in the gauzy winter sky. The laser swiveled as its cameras followed the target. The operator shouted, “Fire!” Within seconds, the drone began to burn as if struck by invisible lightning, then fell to the ground in a fiery arc.