An effort to fly a solar-powered plane 20,000 miles around the world began Monday when the Solar Impulse 2 took off from Abu Dhabi in the United Arab Emirates and landed in Muscat, Oman.
The relatively short jaunt -- just 250 miles (400km) east -- is the first leg of a planned 12-stop global circumnavigation, the first by a solar aircraft. The longest segments will be five-day trips over the Pacific and Atlantic oceans. Those will be the most serious test of the plane's design, which gathers energy from solar cells, then stores it in batteries for overnight flying in the dark.
The plane landed at about 9:15 a.m. PT after the journey was extended to about 13 hours to let winds subside. After a preflight hiccup, the project reported no problems with Solar Impulse 2 -- but its accompanying chase plane had technical difficulties, and the Web site went offline, too.
Feats of aviation derring-do are as old as the aviation industry, including the Montgolfier brothers' hot-air balloons in the 18th century and Chuck Yeager's breaking of the sound barrier in 1947. Such efforts, while risky and sometimes fatal, often serve to advance the state of the art.
In the case of the Solar Impulse, project leaders and pilots Bertrand Piccard and André Borschberg want to show what can be done with an environmentally friendly plane. The solar-powered craft doesn't emit carbon dioxide, the major culprit in global warming, in contrast to conventional jets.
There was a technical hiccup Monday with part of the plane's electrical system, but engineers took care of the issue and the flight went ahead. The team's next leg leads to Ahmedabad, India, and if successful will be the longest distance a solar plane has yet traveled, according to the project.
The plane is huge, with a wingspan of 236 feet (72m) and four propellers measuring 13 feet (4m) in diameter. That wingspan is wider than that of a Boeing 747 but narrower than that of the world's biggest passenger plane, the Airbus A380.
But Solar Impulse 2 is also extremely light -- less than 5,070 pounds (2,300kg), about the same as a full-size pickup truck. And while the A380 can carry 550 passengers, the Solar Impulse 2 has room for just a single pilot.
Theof the Solar Impulse 2 took place last June. The aircraft follows on from the team's initial prototype, which in December 2009.
Though a single-person plane hardly will overhaul the industry, Solar Impulse hopes to nudge it toward better energy efficiency through improved materials, aerodynamics and components -- and by trying to get the public excited about such issues through its FutureIsClean website.
"Governments hope that free-market forces will make industrialists take responsibility for modernizing production, whilst industrialists wait for governments to impose a legal framework that would eliminate the distortion of competition between clean and dirty production methods," Piccard said on the project website. "The only people we ordinary citizens can prod into action are the politicians, who need our votes to be re-elected."
With the combined power of publicity and telemetry, the trip is unusually well documented. The Solar Impulse Web site includes a map where you can monitor travel progress combined with a screen to check battery status and usage, elevation, heading, aileron configuration, the pilot's health condition, and a flight profile that plots the plane's elevation vs. time.
The plane, designed by 50 engineers, has about 2,900 square feet (269 square meters) of solar cells that can collect 340 kilowatt-hours of energy each day. Its lithium polymer batteries, stored in the plane's four motor housings, weigh 1,396 pounds (633kg), which is more than a quarter of the plane's weight.
The plane is designed to fly at speeds between 22mph (36kmph) and 87mph (140kmph), though lower speeds are more efficient. It's got four 17.4-horsepower motors -- about as powerful as the engine of a small motorcycle.
Updated at 9:47 a.m. PT to add that the Solar Impulse 2 landed successfully.