It takes a Boeing 747 about 10 hours and 36,000 gallons of fuel to fly from eastern China to Hawaii. As soon as Tuesday, Andre Borschberg will attempt the same flight in a high-tech, sun-powered aircraft that resembles a dragonfly. He'll do it over five days, without a drop of fuel.
No one before has attempted a solar-powered flight over such a large expanse of ocean – 5,070 miles. If bad weather or other problems force him to ditch his Solar Impulse plane, Borschberg will have only his wits and a life raft to save him.
Borschberg acknowledges the dangers. So does his fellow Swiss adventurer, Bertrand Piccard, who flew the single-seat plane to China in April and is slated to fly it from Hawaii to Phoenix later this month.
“Yes, we are nervous. I am nervous also,” Piccard said in an interview in Nanjing. “But more than anything, we are impressed. We’re in awe of the enormous distance over water that we have to do: Andre for the first part, and me for the second part.”
Piccard and Borschberg hope to be the first pilots to fly a solar-powered plane around the world. After 12 years of planning, networking and fundraising, they launched their tag-team expedition in March, flying from the United Arab Emirates to Oman, and then on to India, Myanmar, Chongqing, China, and Nanjing.
On Wednesday, scores of Chinese students filed into a portable hanger in Nanjing, a city of 8 million people, to meet the pilots and take a look at their odd-looking craft. The students gawked at the enormous wingspan of the Solar Impulse – at 236 feet, wider than that of a 747.
Despite its size, the plane weighs only 5,071 pounds, about as much as a minivan. Much of that weight comes from the four batteries that sit behind four propellers. When the plane is in flight, those batteries are recharged by 17,248 feather-light solar cells on top of the wings. The batteries then help power the aircraft at night.
Flying the plane is complex. To husband its power, the pilot takes the aircraft as high as possible during the late daylight hours. Then, in the darkness, the plane’s engines are turned off and the aircraft sails like a glider, dropping slowly for about three hours. Then the engines are turned back on, drawing on the batteries until daybreak.
“It is difficult to fly, especially at the beginning,” said Borschberg, a 62-year-old former fighter pilot with the Swiss air reserve. With its lightness and wide wingspan, the plane reacts slowly to a change in controls, making it easy for a pilot to overcompensate, he said.
Some aviation experts have mocked the plane’s slowness; it has a top cruising speed of about 80 mph. Piccard said such critics were missing the point. The goal of Solar Impulse isn’t to set speed records. It’s to demonstrate that a plane can fly around the world without a gas tank and, theoretically, with the sun’s rays, keep flying forever.
“We really want to prove that energy efficiency, solar power and modern technology can achieve the impossible,” Piccard said.