Solar Impulse: Flying Across America Without A Drop Of Fuel

Early Friday morning on an airport runway near San Francisco, Calif. a plane was given clearance for takeoff on a historic journey across America. The plane, called Solar Impulse, will make its transcontinental journey without using a single drop of fossil fuel.

Of Swiss design, the Solar Impulse project is intended to show the world what can be done with clean energy technology like solar power. The single-seater airplane weighs about as much as a car and has the wingspan of a Boeing 747, plenty of room to house the aircraft's 12,000 solar cells.

By day, the solar cells power plane's electric motors while also charging batteries, meaning Solar Impulse - unlike other solar-powered aircraft - can fly at night.

The cross-country flight will take place over five stages, the first of which began Friday with the inaugural flight form San Francisco to Phoenix, Ariz. The plane is being flown by Bertrand Piccard, the Swiss psychiatrist and adventurer who was the first to complete a non-stop, around-the-world balloon flight. Piccard will alternate cockpit time with co-pilot Andr Borschberg.

During Friday's flight the plane is expected to reach a cruising altitude of 21,000 feet, LiveScience reported.

One goal of the Solar Impulse is to fuel a conversation about how the world will meet its goal of reducing CO2 emissions. The project website also states Solar Impulse will tackle the problem of resistance to change, which risks locking society into "dangerous" and "costly" old habits.

"Our airplane is not designed to carry passengers, but to carry a message," Piccard said on the project's webpage.

In 2010 the Solar Impulse successfully completed a 26-hour overnight flight, and later a flight from Switzerland to Morocco in 2012. The project's eventual goal is an around-the-world trip in the solar powered plane.

A live stream of Friday's flight is here.