Invisible drones

NewScientistTech has a piece on Invisible Drones that talks about a new Phantom Sentinel aircraft that is Y-shaped and... yes - possibly invisible:

'"Persistence of vision" turns the fast-moving rotors of any helicopter into a near-transparent blur, while the slow-moving body looks solid. Inventor Michael Dammar has come up with a way of making the whole body of an aircraft spin as it flies, turning it into a single blur in the sky. This would not evade radar but should help the aircraft avoid visual identification.

The so-called Phantom Sentinel aircraft is Y-shaped, consisting of a single long wing attached to two short aerodynamic extensions which each end in a propeller. And the weight is carefully balanced so that the centre of mass is positioned between the two extensions. When the motors are running, the solid part of the aircraft spins around this centre of mass, and the longer wing generates lift. The whole thing moves so fast that persistence of vision turns it into a single blur.'

Well - more a blur than invisible then...!