Solar Impulse in Phoenix
The Solar Impulse 2 plane comes in for a landing in Phoenix like a UFO. (Credit: Solar Impulse)

A solar-powered ultralight airplane called Solar Impulse 2 landed in Phoenix tonight after a nearly 16-hour flight from California’s Silicon Valley, finishing up another leg of its environmentally friendly round-the-world odyssey.

The odyssey has been proceeding for more than a year, with occasionally lengthy stopovers. But making time is not the point: If Swiss pilot Andre Borschberg wanted to get to Phoenix quickly, he could have taken a commercial jet flight from San Jose in less than two hours.

Instead, Borschberg lifted off from Moffett Airfield, near San Francisco, at 5:03 a.m. PT. He landed at Phoenix Goodyear Airport at 8:55 p.m. PT (MST) amid gusty winds. The plane was quickly brought inside its hangar for protection.

“It’s more difficult to handle the airplane on the ground than in flight,” Borschberg said jokingly to the crowd that turned out to greet him at the airport. “That’s the reason why we stay so long up there.”

Borschberg and Solar Impulse’s other co-founder, Swiss psychologist-adventurer Bertrand Piccard, have been alternating the piloting duties for the round-the-world trip, which began in Abu Dhabi in March 2015. The $150 million effort got as far as Hawaii last July, but the plane’s batteries were damaged by overheating during a five-day Pacific crossing.

After months of repairs, the odyssey resumed last month with a 62-hour trip from Hawaii to California.

Solar Impulse 2 is an upgraded version of an airplane that made a coast-to-coast trip across America in 2013 – a trip that including a stopover in Phoenix . It’s equipped with more than 17,000 solar cells and enough battery capacity to keep it flying day and night in good weather. Thanks to lightweight materials, it has a wingspan that’s wider than a Boeing 747 jet but weighs only about as much as a family car (5,000 pounds).

The biggest limiting factor is speed: Because it’s powered by four scooter-type electric motors, Solar Impulse 2 typically travels only about as fast as a family car. Also, the plane usually has to wait until nighttime to land, to avoid interfering with other airport traffic.

The point of the exercise is to show how environmentally clean technologies can be used in a variety of industrial applications, ranging from electric-powered aviation to high-tech insulation materials that were developed for Solar Impulse and are already being used in next-generation refrigerators as well.

The round-the-world feat involves psychological as well as technological challenges: Piccard and Borschberg have spent days-long stretches of time cooped up in a solo cockpit, with a seat that can be converted to serve as a sleeping couch. Yoga and meditation help them cope. The pilots turn on a computer program to keep the plane on track during their catnaps.

After Phoenix, Solar Impulse 2 is expected to make at least a couple of additional hops heading for New York. Then there’ll be an Atlantic crossing to Europe, followed by a flight to Abu Dhabi to close the 22,000-mile circuit.

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