Making History: The First Solar-Powered Flight Around the Globe

This IEEE member is a part of the Solar Impulse 2 team

20 April 2016

A year ago, IEEE Member Paige Kassalen was a senior at Virginia Tech, finishing her degree in electrical engineering. Now she’s helping make history as part of the 16-person ground crew for Solar Impulse 2 (SI2), the first airplane to attempt to circumnavigate the world on solar power alone. The crew is vital because the plane needs more human assistance on the ground than regular airplanes do.

Although SI2 has a wingspan greater than a 747’s, it weighs only 2,300 kilograms, a mere 0.6 percent of the big jetliner’s weight. It also has landing gear with two wheels in tandem, like a bicycle’s, so it’s unstable when moving on the ground, especially in gusty winds. Therefore the ground crew runs or bicycles next to the plane to balance and steer it by hand until it’s close to going fast enough to be stable. Then, once the SI2 lands, the crew holds it down and walks it to its hangar.

And Kassalen has other tasks as well. “Between flights, I do anything needed around the hangar,” she says. “This includes testing and repairing the system that measures the force we apply to the wing when we tie down the plane.”


For now, the plane and its crew are at Kalaeloa Airport, near Honolulu. It landed there in July on the eighth leg of its around-the-world journey, the first solar-powered flight to cross an ocean. That was its longest flight so far—7,212 kilometers from Nagoya, Japan—and set a record as the longest solo airplane flight, at 117 hours and 52 minutes.

On the trip from Japan, SI2’s four lithium-polymer batteries overheated, forcing it to remain six months in Hawaii for repairs. The crew has been waiting for spring’s favorable weather and longer days of sunlight for the next flight, to Phoenix. So far, the eight completed legs of the journey have taken the plane 19,957 km, more than halfway around the world from its starting point in Abu Dhabi in March 2015. The next five legs should take it to and across the continental United States, then across the Atlantic Ocean to southern Europe or northern Africa, and finally back to Abu Dhabi.

Kassalen works for Covestro, in Pittsburgh. The SI2 is outfitted with the company’s insulating materials, rigid foams, composites, and coatings. Covestro was looking for someone with a background in engineering and public relations to join the Solar Impulse ground crew. With Kassalen’s EE degree and skills she picked up chairing the IEEE student branch at Virginia Tech and co-chairing the IEEE Women in Engineering Pittsburgh affinity group, she fit the bill.

In addition to her work for SI2, she keeps Covestro updated on the plane’s status and performs such public relations duties as interviewing the two pilots—only one pilot is aloft in the craft at any time—along the way for a video to be shown at a company event this year. Once SI2 leaves Hawaii, she’ll be documenting her journey on Instagram, Twitter, and other social media platforms.

She and the rest of the ground crew won’t get to fly in the SI2; the cockpit barely has room for its lone pilot. The unheated, unpressurized cabin is anything but comfortable. Insulation developed by Covestro keeps it from minus 20o to 35o C. An oxygen mask must be used at altitudes of 3,600 meters to SI2’s maximum cruising altitude, 8,500 m.

André Borschberg and Bertrand Piccard, who launched the Solar Impulse project in 2003 to highlight the potential of clean, sustainable technology, alternate as SI2’s pilots. They have trained themselves to get by with 10 to 12 short naps a day, using deep-breathing techniques and meditation to reduce their need for sleep. Mostly the plane flies automatically. But electronic systems alert the pilot, even if he’s asleep, should the plane deviate from its course or bank more than 5 degrees. Meanwhile, Solar Impulse Mission Control, in Monaco, sends weather advisories and monitors the pilots’ health via sensors.

The electric energy provided by more than 17,000 monocrystalline silicon solar cells—only 135 microns thick—covering the plane’s upper surfaces is relatively limited. The designers tried to keep the SI2 as light as possible despite carrying four brushless, sensorless electric motors (at 17.5 horsepower apiece) plus the pilot and batteries for flying at night.

Whenever possible, the SI2 takes off and lands at night, when turbulence and wind speeds are reduced. During the day, the plane climbs to 8,500 m, building up potential energy while charging its batteries. At night, it gradually descends to 1,500 m and reduces its cruising airspeed from nearly 91 kilometers per hour to 61 kph, to conserve its batteries.

Flight plans are calculated to minimize cloud cover that would reduce the energy input to the solar cells, and to maximize tailwinds. Sometimes, the conditions govern the choice of destination. On SI2’s next leg, for example, its intended destination is Phoenix, but the actual landing could be anywhere from Canada to Arizona.


Once the plane leaves Hawaii, sometime after 15 April, Kassalen and the rest of the ground crew will travel ahead to each hop along the way until it returns to Abu Dhabi. Kassalen ultimately plans to return to Pittsburgh, where her job at Covestro might not end up in engineering.

When she graduated in June, she saw herself as a typical engineer. But she joined Covestro’s trainee program and spent months learning the company’s operations. She then worked at product forecasting and product management for the firm’s polyurethane business, and identified market trends in its polycarbonate business. She was scheduled to finish her trainee program in technical sales for the coatings, adhesives, and specialties unit until Covestro sent her to work with Solar Impulse. “Now I’m still not really sure what I’ll be doing when I return,” she says.

Whichever path she takes, she says, “IEEE has been extremely influential, shaping me professionally and helping me develop my curiosity and the courage to do things outside my comfort zone.

“Because of IEEE, I’m not afraid to take on any task my employer asks of me.”

This article is part of our April 2016 special report on women in engineering.

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