As the name implies, the Solar Impulse project’s plane HB-SIA is powered entirely by the sun’s rays. Though it had flown before, this was the first time it had flown long enough that it needed to rely on storing solar energy to get through the night: the first time that’s ever been done by a solar plane.
The way the plane works, with four electrical engines and solar panels on the wings, is both remarkably simple in concept and extremely difficult in practice. As well as using a carbon fiber design to keep the weight low, the power of the plane is limited to around 6kW and the top speed is a mere 43 miles per hour.
The plane took off at 6.51 am local time in Switzerland yesterday morning, reached a top altitude of 28,000 feet, and touched down again at 9 am today. It still had three hours of battery life remaining, more than expected.
http://www.youtube.com/watch?v=uzHTeqOg4dA&feature=player_embedded
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