A Plane Fueled Only by Solar Energy Flies Across the U.S.

In a quest reminiscent of the Wright brothers’ achievements in aviation, an airplane fueled 100% by solar power made an across-country journey that ended in Washington DC this week, though it has a bit further to travel.  The name of the spindly aircraft is Solar Impulse, and it’s the first solar-powered airplane to fly both day and night.  This privately funded feat – the culmination of 10 years of planning at a cost of about $150 million – was designed to showcase the possibilities for clean energy.solar energy

The Solar Impulse is an ultra-light aircraft which seats one pilot in a cramped cockpit; there is no room for passengers.  The approximately 11,000 photovoltaic cells gather solar power which fuels the plane’s four engines, and solar energy is also stored in batteries on the aircraft.  The airplane’s wingspan is 208 feet, which is the same as a jumbo jet; 10,746 of the solar cells are on the wings.  The solar-powered plane weighs 3,500 pounds, the same as a small car.

The nearly two-month journey of the Solar Impulse began in San Francisco with stops in Phoenix, Dallas, St. Louis, Cincinnati, and Washington DC.  The aircraft travels at a maximum speed of 50 miles per hour; with help from the wind, it can go as fast as 100 mph.  Obviously, speed wasn’t the purpose of the undertaking.  The hope of those who worked on the project was to demonstrate that efficient technologies are possible without the aid of fossil fuels.  And more specifically, it’s possible to fly an airplane long distances in both the daytime and nighttime with solar energy as the sole power source.

In spite of the futuristic technology used on the Solar Impulse, the cross-country flight was similar to the earliest years of aviation.  The lone pilot had to rely on improvisation in numerous tricky situations that came up.  The air travel was easiest on clear, calm days, when the pilot took the plane to a maximum altitude of 28,000 feet, turned off the engines to preserve power, and then began a gradual, gliding descent.  This process was repeated many times throughout the journey, which made riding in the Solar Impulse comparable to riding an airborne rollercoaster in slow motion.

The solar-powered airplane was forced to land at night, after commercial flights had landed, because of the aircraft’s slow speeds.solar panels

The two adventurers who took turns piloting the plane, Bertrand Piccard and André Borschberg, discovered that the plane’s huge wingspan combined with its light weight made a terrible combination with turbulence.  In Dallas, Borschberg said, the plane travelled backwards for a while when facing 40mph headwinds.  An extra overnight stop in Cincinnati was necessary due to strong headwinds.

The most difficult part of the mission across the U.S., Piccard said, was siphoning moisture from the plane after early-morning fog inundated the mechanisms.

The next stop for the Solar Impulse is to go on display at the Smithsonian’s Steven F Udvar-Hazy air and space museum, where a much wider audience can get a close look at the innovative plane.  Lofty future plans for the aircraft include a possible around-the-world flight, possibly as soon as 2015.

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