@graydon @dymaxion @wonka @dr2chase @cstross

How do you know it's not a quadcopter? A quadcopter is extremely simple and cheap. The monospinner is even simpler and cheaper, but it's much slower and less maneuverable.

There are a lot of cheap RC toy drones, including drones with only two props and motors. But these aren't maneuverable enough to attack a target. The quadcopter seems to be the cheapest option that's also maneuverable enough to be used as a guided weapon.