The next time you see something flapping in the breeze on an overhead power line, squint a little harder. It may not be a plastic bag or the remnants of a party balloon, but a tiny spy plane stealing power from the line to recharge its batteries.
The idea comes from the US Air Force Research Lab (AFRL) in Dayton, Ohio, US, which wants to operate extended surveillance missions using remote-controlled planes with a wingspan of about a metre, but has been struggling to find a way to refuel to extend the plane's limited flight duration.
So the AFRL is developing an electric motor-powered micro air vehicle (MAV) that can "harvest" energy when needed by attaching itself to a power line. It could even temporarily change its shape to look more like innocuous piece of trash hanging from the cable.