First came the rough sketch of DARPA's DiscRotor, a helicopter whose blades retract into a disc once the craft hits a certain speed. Now we've got the concept video. Which hopefully means we're that much closer to the real thing.

It's an idea that seems too far out there to come true, but clearly progress has been made towards realizing DARPA and Boeing's DiscRotor dreams. What's gained by using a spinning disk instead of rotors? More mobile, faster hover vehicles that can get troops in and out of critical situations in a hurray. Not to mention it looks, you know, incredible. [Aviation Week via Core77]