Swiss team unveils sun-powered plane

DUEBENDORF AIRFIELD, Switzerland -- It has the wingspan of a Boeing 747 but weighs less than a small car. And it is powered entirely by the sun.

Adventurer Bertrand Piccard on Friday unveiled the Solar Impulse, which, with its sleek white wings and pink trimming, aims to make history as the prototype for a solar-powered flight around the world.

"Yesterday it was a dream, today it is an airplane, tomorrow it will be an ambassador of renewable energies," said Piccard, who in 1999 copiloted the first round-the-globe nonstop balloon flight.

The plane will take part in a series of test flights over the next two years, and based on the results of those a new plane will be constructed for the big takeoff, in 2012.

In a swank ceremony at a military airfield near Zurich, Piccard and co-pilot Andre Borschberg hugged as the curtain was pulled across to give the public its first glimpse of the plane. Numerous dignitaries were in attendance, including Prince Albert of Monaco and major sponsors.

The budget for the project is $98 million, Piccard said.

He and Borschberg said the plane will fly day and night using almost 12,000 solar cells, rechargeable lithium batteries and four electric motors. It will not use an ounce of fuel.

But the maiden flight around the planet will take time.

With the engines providing only 40 horsepower, the plane will fly almost like a scooter in the sky. It will take off at the pedestrian pace of 22 mph, accelerating at altitude to an average flight speed of 44 mph.

Unlike the nonstop balloon trip, the solar flight will have to make stops to allow for pilots to switch over and stretch after long periods in the cramped cockpit.

"You can see it's really small," Borschberg said. "Thirty-six hours is already a challenge. It tests your patience."

The plane's circumnavigation will be split up into five stages, with the stopovers also allowing the team to show off the plane. Borschberg said the stages in the air will last up to five days.

A nonstop round-the-world flight will have to wait until batteries can be made lighter so more pilot comfort can be added to the plane.

The first test flights will be later this year, with a complete night voyage planned for 2010.

"It will be like the Wright brothers," said the 51-year-old Piccard, who comes from a long line of adventurers. His late father Jacques plunged deeper beneath the ocean than any other man, and grandfather Auguste was the first man to take a balloon into the stratosphere.

"We will start one meter above the ground, then three meters, then five meters," he said. "When that works, we'll be able to take it to altitude."

One thing a solar plane cannot handle is bad weather. Because the solar panels are needed for day flying and for charging the 400-kilogram lithium batteries that power the plane by night, it relies on sunshine.

"We'll certainly avoid stormy situations," Borschberg said. "We'll avoid rain as well, because you cannot collect energy in this weather. So the challenge for the team will be to find a path that is favorable. We've been training for five years."

Piccard says the plane should also serve as an inspiration for inventors and manufacturers of everyday machines and appliances.

"If an aircraft is able to fly day and night without fuel, propelled solely by solar energy," Piccard said, "let no one come and claim that it is impossible to do the same thing for motor vehicles, heating and air conditioning systems and computers."

Borschberg said the idea was first envisioned by Piccard and co-balloonist Brian Jones as they finished their 1999 flight with only 90 pounds (40 kilograms) left of an original supply of 3.7 tons of liquid propane, and realized "this historical success could have turned into a failure due to lack of fuel."

"At this moment Bertrand made the decision for his next flight around the world he wouldn't use any fuel, he would be totally independent of fossil energy," said Borschberg, an engineer and fighter pilot.