Solar-powered plane preps for first long-distance flight

Just one week before he embarks on a historic flight across America next week, Swiss 'scientist-adventurer' Bertrand Piccard took to the skies over San Francisco's Golden Gate Bridge yesterday in Solar Impulse, a solar-powered airplane that is capable of flying both day and night without fuel.

Piccard's 'Across America 2013' flight is scheduled to take off next Wednesday, May 1st, as he attempts to fly from San Francisco to New York, with planned stops along the way in Phoenix, Dallas, St. Louis or Atlanta, and Washington D.C.. That's not a particularly noteworthy accomplishment in of itself, as there are probably more than a few people who have made that kind of flight sitting in cramped coach seats and eating mediocre airline food. However, what's impressive about Piccard's plan is that he's going to be doing it in a plane that is entirely powered by the Sun, and even though it carries no fuel at all, he's still going to be able to fly it at night.

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Solar Impulse HB-SIA is a specially-designed one-person aircraft that only weighs about as much as a passenger car (about 1,600 kg), but has a wingspan of over 64 metres — roughly the same as that of 747 jumbo jet. The entire top surface of that massive wingspan is made up of an array of solar panels that supply the plane with power, propelling it at speeds of up to 70 km/h and heights of up to 8,500 metres (almost 28 thousand feet).

The way Solar Impulse flies at night is fairly straight forward. It has batteries to store the power it receives from the Sun, but rather than rely solely on those at night, Piccard spends the first half of the night flying the plane like a glider. Before the Sun sets, he takes the plane up to its maximum altitude, and then once the sky goes dark, he begins a slow descent over several hours until he gets to about 1,500 metres above the ground. At that point the batteries are switched on and he can fly on that reserve power until the Sun comes up again.

If Piccard sees only clear blue skies for his trip, it could be just a nice, leisurely flight for him (if you don't count being cramped into a tiny cockpit the whole time). However, any kind of cloudy or stormy weather he meets could put the entire mission at risk. Clouds would limit the amount of power the Solar Impulse's batteries could store, which will make it much more difficult for him to fly during the night, and any turbulence he encounters could put him at serious risk. He'll be relying on his ground crew to keep him informed of weather conditions along the way, so hopefully he can avoid any serious problems.

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This flight across America is only the first step for Piccard, though. The next one will take place in 2015, when he'll attempt to fly all the way around the world, solely on solar power.

“When I was a child I saw my father diving to the deepest point in the ocean with the US navy,” Piccard said in a promotional video on his website. “That was my first inspiration. Today with scientific exploration I want to inspire others also to achieve the impossible thanks to pioneering spirit.”

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