Solar Impulse takes flight across America: The technology and the vision

May 6th, 2013 | by K Kaufmann | Comments

I first wrote about Solar Impulse almost a year ago, when the Swiss-made, solar-powered airplane made a test flight from Madrid to Rabat in Morocco.

The plane is now flying across the U.S. and last week completed its first leg from San Francisco to Phoenix, where it has become an instant hit. So many people have signed up for the public visits to the plane — the first was Sunday, a second is set for Tuesday – that the SI team is working on setting up a third on Wednesday.

Subsequent stops will be in Dallas, St. Louis, Washington, D.C. and New York.

The picture below, taken by Jean Revillard of the Solar Impulse team, shows the plane taking off early May 3 from San Francisco.

A solar-powered aircraft flies above San Francisco at night.

Additional photos and great video of the takeoff and landing, shortly after midnight on May 4, in Phoenix can be found on the Solar Impulse website.

There’s also an explanation of how the plane can fly at night, when obviously there is no sun.

“As the sun begins to set on the horizon, solar power obviously
decreases. Once the available solar power is not sufficient to support
level flight anymore, the pilot reduces the motors and initiates a
gentle descent (about 0,4 m/s) to a low night loitering altitude of
1000-1500m meters. Out of its maximum altitude of 28000ft (8000m), the
prototype can glide for 4-5 hours consuming almost no electric energy.
When the lowest altitude is reached, usually long after sunset, the
motors, now powered by the batteries, are used to maintain a level
flight at 25 knots until the morning. As the breathtaking tones of the
sun on the horizon start filling the sky with warmth, the aircraft can
once again begin its ascent, and the cycle begins.”

While Solar Impulse is winging its way across the U.S., a team back in Switzerland is already working on the next model of the plane, the one that could be used for an around-the-world flight in 2015.

An article on the technology behind the plane on the website of the Swiss Broadcasting Service is fascinating.

There is not a single rivet in the plane, all parts are glued together, and it is made of a superlight composite material that weights about 3.2 ounces per square meter, which is a little over one square yard. For the next Solar Impulse, the team is going for an even lighter material that would weigh in at a scant .88 ounces per square meter.

Watching the excitement around Solar Impulse made me think of the pioneering days of aviation, when flying across the country or across the ocean was an adventure and aviators such as Charles Lindbergh and Amelia Earhart –  and their planes — were public celebrities.

The Solar Impulse team obviously feels the same. One of five symbolic items in the cockpit with pilot Bertrand Piccard is a small piece of fabric from the Vin Fiz Flyer, the first plane to fly across the U.S. in 1911, piloted by Calbraith Perry Rodgers. According to information on the Solar Impulse website:

It was the first flyer  to be sold to a private citizen by the Wright brothers, who also trained Calbraith as a pilot in only 90 minutes. The Vin Fiz took 3 months to cross the United States at a speed of 45-55 mph (72-88 km/h) with over  15 crashes.”

Piccard is also carrying an Explorers Club flag, a Clean Generation flag and a flash drive containing all the names of the people who have signed up as supporters on the Solar Impulse website.

More than anything, the Solar Impulse team wants the flight to ignite a spirit of innovation around the world, to encourage scientists, business and explorers to push the boundaries of what they think is possible in terms of clean generation. Its message, from the SI website:

“Since we cannot change the character of the human being, let us make an
effort to adapt to the way he functions. Let us try to give him a
personal interest to get into the way of thinking in terms of
sustainable development. Let us prove that we are dealing here with an
enormous new market with all sorts of economic and political outlets for
those who understand how to invest in it in time. . . .

“We are dealing here with a symbol, as solar airplanes are unlikely ever
to carry 300 passengers, but it is a symbol that affects all of us. In
fact, aren’t we all on Earth in the same situation as the Solar Impulse
pilot? If he does not have the right technologies or wastes his energy,
he will have to land before the rising sun enables him to continue his
flight. And as for us, if we do not invest in the scientific means to
develop new energy sources, we shall find ourselves in a major crisis,
which will prevent us from handing over the planet to the next
generation. ”

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