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Solar Impulse in Seville
The Solar Impulse 2 airplane takes off from Seville, Spain. (Credit: Solar Impulse)

Sixteen months after it started, the fuel-free Solar Impulse 2 airplane took off before dawn Monday for what’s expected to be the second-last leg of its round-the-world journey, heading from Spain to Egypt for a pyramid photo op and a Cairo landing.

Solar Impulse co-founder Andre Borschberg was at the controls in the solar-powered plane’s solo cockpit for what could be his last time during the globe-girdling odyssey.

“The unknown is always there,” he said before takeoff. “So I’m crossing my fingers before crossing the Mediterranean Sea.”

The ultra-lightweight plane rose up from Seville International Airport at 6:20 a.m. local time (9:20 p.m. PT Sunday). The Solar Impulse team said Borschberg’s trip is scheduled to take about 50 hours. He’s on track to cross through the airspace of six countries during the flight.

The aim of the $150 million, sponsor-funded Solar Impulse effort is to demonstrate environmentally friendly technologies. More than 17,000 solar cells cover the skin of the carbon composite airplane. More than 800 pounds of advanced lithium polymer batteries can keep the plane going day and night, as long as the weather’s clear.

Thanks to its carbon composite structure, the plane has a wingspan that’s wider than a Boeing 747 (236 feet vs. 224 feet) but weighs only about as much as a minivan (5,000 pounds). The big limitation is that the plane’s four scooter-sized electric motors can propel the plane only about as fast as that minivan.

Egypt holds a special status for Solar Impulse’s other co-founder, Swiss psychiatrist-adventurer Bertrand Piccard. He noted that Egypt was where he completed his round-the-world balloon flight with fellow pilot Brian Jones in 1999.

Piccard recalled that the Breitling Orbiter 3 balloon’s supply of propane fuel was nearly exhausted by the time he and Jones landed. “That’s when I said, ‘I want to fly around the world another time, but with no fuel.'”

Thus were the seeds of Solar Impulse planted, 17 years ago.

A somewhat less capable Solar Impulse plane made a months-long trip across America in 2013, setting the stage for the start of Solar Impulse 2’s round-the-world attempt in March 2015 in Abu Dhabi. Heading eastward, the plane stopped over in Oman, India, Myanmar, China and Japan, with Piccard and Borschberg taking turns in the cockpit.

The batteries overheated during a record-breaking five-day trip across the Pacific to Hawaii a year ago. As a result, the Solar Impulse team had to put the journey on hold for nine months to make repairs and await the return of favorable weather. “We drank the champagne too early,” Piccard recalled.

The odyssey resumed this April. Solar Impulse 2 made good progress from Hawaii to California, then to Arizona, Oklahoma, Ohio, Pennsylvania, New York and across the Atlantic to Spain.

If all goes well with the Seville-to-Cairo trip, Piccard will take the controls for the final leg of the 22,000-mile circuit, returning to Abu Dhabi.

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