The challenge is to circle the world in an airplane that doesn’t use fossil fuels and emits no greenhouse gas, but the Solar Impulse is taking it one feat at a time. This summer, the Solar Impulse solar airplane will cross America, flying from San Francisco to New York City, spreading its environmental message as it inspires skywatchers to see the outlines of a future powered by renewable energy sources. More than a solar-powered plane, the Solar Impulse represents the promise of that alternative future based on new, lightweight technologies, renewable energy, and the spirit of possibility.
“The grand exploits of the 20th century were conquests: North and South Poles, Everest, the depths of the ocean, the Moon. Those of the 21st century, in my view, will need to consist much more of preserving, if not improving, the quality of life on our planet. How do we reconcile economic and ecological interests and promote the use of new technologies to save energy and create new power sources? Solar Impulse is a symbol of this mindset,” says pilot Bertrand Piccard, a co-founder of Solar Impulse, and a world-renowned adventurer. He was the first air balloonist to circle the globe non-stop.
Seven years of study, design, manufacture, and testing, went into the HB-SIA Solar Impulse prototype aircraft, including the construction of a cockpit simulator to give the pilots experience inside the small space, and in maneuvering the plane with its light body and oversized wingspan. The effort led to the Solar Impulse’s success in a historic milestone: the first ever night flight by solar airplane. The aircraft was in the air for 26 hours, both day and night, on July 7th and 8th, 2010. The second morning of that flight, the plane reached 40% battery reserves, the lowest of the entire run. Two years later, in July 2012, the Solar Impulse passed another milestone: the first solar-powered intercontinental journey, a round trip flight between Europe and Africa.
In absence of the sun, the Solar Impulse relies on four solar-charged electric motors housed under the wings. They make up 25% of the plane’s total weight, making an ultralight structure for the rest of the plane necessary.
At a March 28 press conference, when asked about the drawbacks of solar flight, Piccard acknowledged that “you pay a price.” The plane has the wingspan of a jumbo jet (63.4m/208 ft.) and weighs as much as a small car (1600kg/3.527 lb). These physical limitations have challenged partners to find the lightest possible materials that will do the job, with impressive results, but will keep solar airplanes from being practical for passenger flight anytime soon.
“It is not the easiest way to fly, but it is the most fabulous way to fly,” said Piccard, “because the more you fly, the more energy you build on board.”
“Just imagine your energy reserves increasing during flight! To make this dream a reality, we had to make maximum use of every single watt supplied by the sun, storing any surplus in our batteries,” states Andre Borschberg, Solar Impulse co-founder, and also a pilot, on the Solar Impulse site. The plane is “a flying laboratory for clean technologies” with scientific implications of interest to many different industries.
Piccard and Borschberg officially launched Solar Impulse in 2003, and began their quest to build a manned solar airplane capable of continuous flight around the world, along with partners Brian Jones and Luiggino Torrigiani. They formed alliances along the way with the Ecole Polytechnique Federale de Lausanne, the European Space Agency, and Dassault Aviation, and others.
Fast forward ten years, this summer starting May 1st, if weather permits, the Solar Impulse will make its way across the United States. Negotiations are still in progress about one leg of the route, but it looks like the plane will fly from San Francisco, California to Phoenix, Arizona, to Dallas, Texas, and, via another unnamed city to Washington, DC, ending up in New York City in early July – a cross-country flight powered only by the sun. Each leg is designed to last no longer than 24 hours. This is because the plane currently has no auto-pilot, and longer time frames then become dangerous when flying alone. Week long layovers will give the American public the chance to get to know the Solar Impulse and enjoy a little old-fashioned summer barnstorming.
The Solar Impulse team is also beginning work on the HB-SIB prototype, a bigger solar airplane they plan to use to circumnavigate the globe in 2015. The design changes include a larger, pressurized cabin, and an even longer wingspan.
Is solar-powered aircraft the future of aviation?
“It would be crazy to say yes,” answered Piccard, “But it would be stupid to say no. In 1903 people could not imagine passenger flight either.”
As Piccard spells out on the SolarImpulse.com website, “Solar Impulse was not built to carry passengers, but to carry messages. We want to show what can be achieved using clean technologies, to reduce our society’s dependence on fossil energies. What we can achieve in the air, anyone can do on the ground, in their everyday lives.”
Green City Journal will regularly update on the Solar Impulse’s summer tour, so check back often. Learn more at Solar Impulse.