Thinking of going for a swim? Keep an eye out for the Reusable Unambiguous Swimmer Warning Vehicle, a torpedo that can hunt down any swimmer who poses a threat to U.S. waters. It circles around its victim, relays the exact GPS coordinates of the prey, and sounds an alarm.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.