Solar-power plane airborne on historic round-the-world trip

ABU DHABI, United Arab Emirates -- With its wings stretched wide to catch the sun's energy, a Swiss-made, solar-powered aircraft took off from Abu Dhabi just after daybreak Monday in a historic first attempt to fly around the world without a drop of fossil fuel.

Solar Impulse founder Andre Borschberg was at the controls of the single-seat aircraft when it lumbered into the air at the Al Bateen Executive Airport. Borschberg will trade off piloting with Solar Impulse co-founder Bertrand Piccard during layovers on a 21,700-mile journey.

Some legs of the trip, such as over the Pacific and Atlantic oceans, will mean five days and five nights of flying solo. Both pilots have been training hard for this journey, which will span 25 flight days over five months before this Spruce Goose of renewable energy returns to Abu Dhabi in late July or August.

"It is also exciting because you know, you simulate, you calculate, you imagine, but there is nothing like testing and doing it in real," Borschberg said just hours before takeoff. "I am sure we are all confident, and hopefully we will be able to see each other here in five months."

The Solar Impulse 2 aircraft, a larger version of a single-seat prototype that first flew five years ago, has a wingspan of 236 feet, larger than that of the Boeing 747. Built into the wings are 17,248 ultra-efficient solar cells that transfer solar energy to four electrical motors that power the plane's propellers. The solar cells also recharge four lithium polymer batteries.

At about 5,070 pounds, the Si2 weighs as much as a minivan or mid-sized truck. An empty Boeing 747, in comparison, weighs some 400,000 pounds.

The Si2 is heading first to nearby Muscat, Oman, where it will land after about 10 hours of flight. A typical passenger jet takes just one hour to make the same journey. Piccard says the best speed for the lightweight Si2 -- made of carbon fiber -- is about 25 knots, or 28 mph.

Borschberg has been practicing yoga and Piccard self-hypnosis to calm their minds and manage fatigue during the long solo flights. They aim to rest a maximum of 20 minutes straight, repeating the naps 12 times over a 24-hour period. Goggles worn over the pilot's eyes will flash lights to wake him up.

Neither pilot will be able to stand in the cockpit while flying, but the seat reclines for stretching, and its cushion can be removed for access to a toilet.

Armbands placed under their suits will buzz if the plane isn't flying level. The plane also does not have a pressurized cockpit, so Borschberg and Piccard will be able to feel the changes in temperature. The pilot's blood oxygen levels constantly will be monitored and sent back to ground control.

The plane will reach an altitude of about 28,000 feet during the day to catch the sun's rays and at night dip to around 5,000 feet when flying over the ocean.

"You have to make the cockpit like your own house for a week in the air," Piccard said, telling The Associated Press he will keep a few small mementos from friends with him on the flight, though he declined to say what.