太阳能飞机准备环游世界

After successfully flying their solar-powered plane from Spain to Morocco in 2012, and across the U.S. in 2013, Swiss aeronautical enthusiasts are now getting ready to attempt a flight around the world next year. The new, improved version of the plane, named Solar Impulse 2, was recently unveiled in Switzerland.

Solar Impulse 2 is a single-seat airplane with a wingspan of 72 meters, but it weighs only about the same as a large car. The wings provide about 200 square meters of space for solar cells that charge lithium-ion batteries, needed to keep it flying at night. Its four electric motors allow it to cruise at a speed of up to 140 kilometers per hour, at an average altitude of 8,500 meters.

The longest flight of its predecessor, Solar Impulse 1, made in May 2013 from Phoenix, Arizona to Dallas, Texas, was just over 1,500 kilometers.

But pilot Andre Borschberg, who once flew jets for the Swiss Air Force, says Solar Impulse 2 - with favorable weather - will be able to fly much longer distances between stops.

“When we leave the coast of China, we don't know what the weather looks like on the other side of the ocean. So these are big question marks," said Borschberg.

It took 12 years of research and testing, including flights of the previous version, to finally build the aircraft they believe will be able to fly around the world in 20 flying days spread over three months.

Chairman of the Solar Impulse project Bertrand Piccard says every detail on the airplane is designed for maximum efficiency.

“This airplane is an example of energy efficiency, how we save the energy, and how the energy from the sun is enough to keep the airplane in the air day and night," said Piccard.

While flying on auto-pilot, either pilot will be able to sleep for a while, use the toilet, even exercise.

Borschberg says the goal is not to promote building more solar-powered planes.

“It is to bring products to their clients which are more energy efficient: in home buildings, in transportation, in appliances, it can be lighting," he said.

Solar Impulse 2 is scheduled to begin test flights in May, while the actual circumnavigation is planned to start next March from an airport somewhere in the Persian Gulf.