The Solar Impulse just completed its final test flight before it travels across the U.S. without using a single drop of fuel. The plane spent most of yesterday cruising around 3,500 feet over the San Francisco Bay, giving many people a chance to see the giant solar aircraft in action. The “Cross America 2013” tour is scheduled to kick off next Wednesday, May 1st, when Solar Impulse co-founder and pilot Bertrand Piccard embarks upon the first leg of the journey from San Francisco to New York.

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Piccard began yesterday’s flight at Moffett Field and made his way up the coast from Half Moon Bay towards San Francisco, flying at the speed of 45 miles per hour. The winged giant spent the day gliding over some of the local icons, including the Golden Gate Bridge.

The plane, named HB-SIA has a wingspan of 208 feet-equal to an Airbus A340 commercial passenger jet airliner but weighs only 3,527 pounds. Its wings are clad with 12,000 solar panels organized into groups of 300 cells. The four 10-horsepower engines are powered by the energy captured during the day. Excess energy is stored in four lithium polymer batteries and used for night flights.

The Solar Impulse has already flown over Paris, Switzerland and Morocco, before it reached the U.S in February. Yesterday’s flight over San Francisco was its third and final test flight before it embarks on the cross-country journey next week.

+ Solar Impulse

Via Wired

Photos from the Solar Impulse Facebok page