Robot 'Floaty' rides the wind like a bird, staying stable without propellers (opens in new tab)

Current flying objects face a trade-off: Drones with propellers, for instance, are very agile and able to hover; however, they use up a lot of energy. Airplanes, on the other hand, feature fixed wings that allow them to fly very efficiently. The downside: They can't remain suspended in the air like a kestrel on the lookout for prey.