The Solar Impulse team sent their solar aircraft out from Moffett Airfield near San Jose, Calif., Friday at 6:12 a.m. Pacific time, for Phoenix, Ariz., on the first leg of a transcontinental U.S. flight. It landed in Phoenix at 12:30 a.m. Saturday. The aircraft is powered by four 10-horsepower electric motors that draw energy from 12,000 photovoltaic cells on its wings and lithium-polymer battery packs that store excess solar energy for use in darkness. Six hours into the roughly 550-nm flight, flying at roughly 40 knots in climb, the aircraft had collected more energy to power its motors than it had stored at takeoff. Even before that, pilot Bertrand Piccard was chatting with family and taking calls from reporters, espousing the benefits of solar power — but not for practical manned flight.
The Solar Impulse team is not shy about their mission to deliver an “important political message” regarding the use of solar energy. Piccard said that the solar flight across the country was intended to bring attention to the possibilities of solar power for buildings, houses and other applications. Piccard believes that integration of solar power is now proven technology that could make a “huge impact on energy consumption.” As for aviation, Piccard concedes the technology must advance beyond current capabilities before solar power can be practically applied. The Solar Impulse HB-SIA does fly on solar power but weighs 3,527 pounds, carries one, and generally cruises at less than 50 mph at 20,000 feet. Piccard said flying the aircraft required managing a great deal of inertia due to the aircraft’s dimensions (its wing spans more than 200 feet). Though light, the moments increased the piloting workload on rudder and stick, Piccard said.