FLYING using only the power of the sun is an enticing prospect. But manned solar-powered aircraft are fragile and slow, like the ungainly craft which a Swiss team called Solar Impulse plan to fly around the world. Take the weight of the pilot out, however, and things change. A solar-powered unmanned aerial system (a UAS, more commonly called a drone) could fly long, lonely missions that conventional aircraft would not be capable of. Advances with the technology mean many such craft could be swarming into the sky.
Small, battery-powered UASs are already common. The Raven, made by AeroVironment, a Californian company, is a hand-launched reconnaissance aircraft with a wingspan of about 1.4 metres that is widely used by the American armed forces. Thanks to advances in electronics a small UAS like this is now capable of beaming back images from high-resolution video cameras and other sensors.
Eventually, though, the civilian use of small drones may well exceed that of military ones. They can survey pipelines and power cables, perform aerial filming for anyone from television news stations to estate agents, monitor fires, assist in search-and-rescue operations and help carry out research. Aviation regulators are now forming rules that would allow far greater civilian use of such systems.