Solar Impulse aircraft flies, briefly (photos)

The first plane designed to fly day and night without fuel, the Solar Impulse HB-SIA lifted off for its maiden flight on December 3 from its home at Dubendorf Airfield, near Zurich, Switzerland.

Four electric propellers and a bank of batteries powered the prototype craft on its test voyage, or "flea hop," as the Solar Impulse team calls it. The plane did resemble a huge insect hopping off the ground.

The team had spent several weeks running ground tests on the Impulse to assess its control, acceleration, braking paths, and engine power. After the plane passed with flying colors, the decision was given for pilot Markus Scherdel to guide the prototype on its initial test trip. Following a series of runway checks, Scherdel steered the craft off the ground.

The wingspan of the Solar Impulse matches that of a Boeing 747, but the craft weighs only as much as a midsize car. Its array of 12,000 solar cells mounted on the wings are designed to pump renewable solar power to the plane's electric motors. Those solar cells also energize the Impulse's batteries during the day, eventually allowing it to take flight at night.

During its brief but momentous test flight, the Impulse got all of 1 meter (3.2 feet) off the ground and flew a distance of 350 meters. (By comparison, the Wright Brothers flew about 260 meters in 59 seconds in the longest flight of their first day of trying at Kitty Hawk in December 1903.)

Scherdel is applauded after his successful test flight. "This is an amazing aircraft," he said. The closer you get involved, the more unique are the challenges."

"We've done it," wrote Solar Impulse co-founder Bertrand Piccard in his blog after the flight. "It actually took off! With its immense wingspan and low speed, it seemed to just hang in the air without moving for 30 seconds. But that was enough for it to fly 350 metres. The whole team held its breath while test pilot Markus Scherdel stabilised the Solar Impulse with a few tweaks of the ailerons before touching down smoothly."

Co-founders Piccard and Andre Borschberg exchange a handshake following the completion of the craft's test flight.

"This is the culmination of six years of intense work by a very experienced team of professionals," said Borschberg. "This first 'flea hop' successfully completes the first phase of Solar Impulse, confirming our technical choices."

The Solar Impulse team members raise their arms in cheer over the flight of their creation. The 70-member team worked for more than six years on the design, construction, and testing of the Solar Impulse before the prototype could take flight.

"Never before--in the whole history of aviation--has an aircraft so big, so light and consuming so little energy actually flown," wrote Piccard in his blog. "How can I thank such a magnificent team, how can I sufficiently congratulate all those engineers, who, under the supervision of Andre, have calculated, designed and built this first prototype?"

The Solar Impulse is scheduled to make more test flights early next year, with the team gradually increasing its distance with each new test. The craft should then be ready to journey on its first night flight next summer, ih which it will use captured solar energy to power its engines when the sun goes down.

From there, the team hopes to take longer and higher flights in 2011; then in 2012, a transatlantic trip followed by the ultimate objective--a full journey around the world.

"On the one hand I find it terrific to see a dream come true," said Piccard. "On the other hand, I remain humble in the face of the difficult journey still to be accomplished--it's a long way between these initial tests and a circumnavigation of the world."

For more photos of the Solar Impulse, see "Photos: Soaring ambition for solar aircraft."