Autogyros are the duck-billed platypuses of the aviation world. They look like helicopters, operate on the same principles as airplanes, and can be pulled like a kite. And if L-3's new Valkyrie drone is any indication, there's a chance autogyros might join the U.S. Navy.
First, the principle of the machine: While an autogyro looks most like a helicopter, the rotor is instead unpowered, and provides lift much like the wings of an airplane—by being pulled through the air, in this case by a cable. (Most autogyros throughout history have been powered by onboard engines, which made them look like the awkward offspring of an airplane and a helicopter.)