Power for an actual helicopter or multirotor is extraordinarily unlikely to ever be sufficient with solar, even in the short term, on a sunny day. Power for an

Power for an actual helicopter or multirotor is extraordinarily unlikely to ever be sufficient with solar, even in the short term, on a sunny day. Power for an efficient sailplane is alright for an afternoon... but only barely have we achieved the 48-hour golden timespan with extreme size, expensive materials, good weather, and working the batteries to within an inch of their lives. Power for a hyperblimp, which is probably the closest to what Stephenson described (but 1-2 orders of magnitude larger), is easy to provide with solar. Expect them reasonably soon in military applications. There is experimental-but-also-just-barely-workable laser propulsion, and also what I like to call a 'Flying Pole' where a wire-tethered quadrotor sits in one place 100 meters up for a vantage point, indefinitely, with significant practical payload (this is used experimentally by various militaries). Lastly, there is the holy grail, autonomous swarm launch, landing, and refueling, which allows a large number of quadrotors to blanket an area of several kilometers around with close-in distributed surveillance. With the right code and minimal hardware, and importantly a large enough swarm to justify infrastructure, this is highly practical, the engineering just has to be done. I have my doubts that this will be reliable for a while with small fixed wing drones - the wind and approach makes it a much harder problem than VTOL craft. In case you're interested, UAV construction is now a large sector of the RC aeromodelling hobby. I've tried to catalog developments on my wiki, http://dronepedia.com http://dronepedia.com , but it's a firehose of information out there. If you want to dip your toes in, check out a day's discussion on http://diydrones.com http://diydrones.com