Biofuels may be the most mainstream option for powering the airplanes of the future, but solar power shouldn't be completely overlooked--just take a look at the Solar Impulse, a completely solar-powered plane that just finished its first test flight, a 1.5-hour trip above Switzerland. The Boeing 747-sized plane, which features 12,000 solar cells on its wings, reached an altitude of 3,937 feet and an average speed of 44 mph during its 87-minute flight.
This wasn't technically the first test for the Solar Impulse. In December 2009, the propeller plane took a quick 1,148 foot "flea hop" off the ground. But this week's test flight was the first extended trip for the electric motor-equipped plane, which was piloted by Marcus Scherdel. Overall, Scherdel was satisfied with the flight. In an interview on the Solar Impulse website, the pilot noted, "I have to say that today we were flying very slow--at one point the ground speed had dropped to 12 knots per hour (22 km/h)--and we never intended to test the critical parameters of the plane. This will be one of the goals in the upcoming flights."
And rest assured, there will be upcoming flights. The Solar Impulse project has a $94 million budget, much of which comes from major sponsors like Solvay, Omega, and Deutsche Bank. The next test: a 36-hour night flight. In 2012, the Solar Impulse will attempt a round-the-world flight. If that goes well, don't be surprised if solar cells start popping up on commercial aircraft soon after.