A one-of-a-kind aircraft powered solely by solar energy took to the skies above Silicon Valley early Friday morning on the first leg of a planned trip across the U.S.
The aircraft, called Solar Impulse, has the wingspan of a jumbo jet but weighs the same as a small passenger car and can theoretically fly forever.
At a little after 6:00 AM, in front of a small crowd of spectators and a row of media cameras, the propellers on the aircraft revved and it began to move along the runway at Moffett Field in Mountain View. Within a few seconds it was airborne, climbing slowly away from its home for the last two months and, the team hopes, into another page of aviation history.
"In terms of today's flight, it's a very big contrast," Bertrand Piccard , pilot of the Solar Impulse, told reporters about an hour before takeoff. "On one side, we have to be very precise, it's an aeronautical first. We have to coordinate with the FAA, with air-traffic control, so there is a hard workload for the pilot. On the other side, it's complete freedom because we have no fuel on board. It's completely solar powered so theoretically the plane can fly forever. We don't need to refuel."
The secret to its light weight is a fuselage made from carbon fiber sheets three times lighter than paper. The solar cells that cover the tops of its expansive wings are thin, at just 135 microns, and it makes incredibly efficient use of the power it generates. Losses in the plane's motors amount to roughly 6 percent, versus around 70 percent in conventional motors, according to the project team.
Solar Impulse has already set several aviation milestones in Europe, including the first ever solar-powered night flight in 2010, the first international solar flight in 2011 and the first intercontinental solar flight in 2012. It also holds five world records, including one for duration: an impressive 26 hours, 10 minutes and 19 seconds.
The journey that began on Friday is scheduled to end in New York sometime in July. The first leg, at pace equivalent to about 70 kilometers per hour, takes it from Moffett Field in Silicon Valley to Phoenix, Arizona, where it is scheduled to land at around 1:00 AM Saturday morning. Further flights will go to Dallas, St. Louis, Washington D.C., and New York.
Martyn Williams covers mobile telecoms, Silicon Valley and general technology breaking news for The IDG News Service. Follow Martyn on Twitter at @martyn_williams. Martyn's e-mail address is email@example.com