A prototype aircraft powered solely by a ground-based laser has flown through test flights at NASA's Dryden Flight Research Center in California. The plane, which has a wingspan of 1.5 metres and weighs just 300 grams, uses photovoltaic cells to convert the energy from the infrared beam into electricity to power a propeller. The aim of the research is to develop aircraft that can fly at high altitude for indefinite periods. "The craft could keep flying as long as the energy source, in this case the laser beam, is uninterrupted," says Robert Burdine, at NASA's Marshall Space Flight Center, who was laser project manager for the test. "The aircraft could be used for everything from relaying cell phone calls to cable television or internet connections," says David Bushman, project manager for beamed power at Dryden. It could also be used for remote sensing of the Earth's surface or to monitor the atmosphere. There are numerous projects developing long duration, high altitude aircraft, including balloons and solar-powered planes. But spokesman Jerry Berg, at Marshall, points out that solar-powered craft need to carry heavy batteries to remain aloft at night, while balloons are more difficult than airplanes to hold in one location. More here.