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Solar Impulse in Cairo
The Solar Impulse plane rolls out of its hangar in Cairo for its flight to Abu Dhabi. (Credit: Solar Impulse)

The Swiss-built Solar Impulse 2 airplane rose into the skies over Cairo, Egypt, tonight to finish off its 16-month, 22,000-mile, fuel-free journey around the world.

The 17th and final leg of the odyssey began at 1:29 a.m. Sunday local time (4:29 p.m. PT Saturday). If the itinerary proceeds according to plan, the solar-powered plane should arrive about 48 hours later in Abu Dhabi, where Solar Impulse started out in March of last year.

This last flight had to be postponed for a week because the winds were too strong, and because the pilot – Swiss psychiatrist-adventurer Bertrand Piccard – wasn’t feeling well enough to take on the grueling flight. Tonight, Piccard said such setbacks just came with the territory.

“This is an adventure,” Piccard told reporters before takeoff at Cairo International Airport. “It’s not a business plan, it’s an adventure.”

Piccard and Solar Impulse’s other co-founder, Andre Borschberg, have alternated piloting duties in the plane’s solo cockpit. Borschberg flew into Cairo less than two weeks ago, and tonight he was monitoring the takeoff from the $170 million project’s mission control center in Monaco.

“Everyone here in the flight control is wishing you a fantastic flight,” Borschberg told Piccard over a radio link.

In addition to adding a new page in the aviation record books for the first-ever solar-powered flight around the world, Solar Impulse is aimed at demonstrating environmentally clean technologies.

“Solar Impulse is not only an aeronautical project. It’s a project for energy, for a better world, to show what is pioneering spirit,” Piccard explained. “Today, if we want to protect the environment, if we want to fight climate change, but also if we want to give access to energy to the poorest people in the world, to the most remote villages, we need renewable energy.”

This odyssey follows up on an earlier trip across America that Piccard and Borschberg made with a smaller solar-powered plane. Thanks to lightweight composite materials, Solar Impulse 2 boasts a wingspan that’s wider than that of a Boeing 747 jet (236 feet vs. 224 feet), but the plane weighs no more than a minivan (5,000 pounds).

Solar Impulse 2 is equipped with more than 17,000 solar cells and 800 pounds of advanced lithium polymer batteries that can keep it flying day and night, as long as the skies are sunny.

The trip from Cairo to Abu Dhabi will be challenging: Solar Impulse’s scooter-type electric motors can push the plane ahead only at about the speed of a minivan, topping out at 90 mph or so. That means the plane and the pilot will have to cope with two days’ worth of blistering temperatures and turbulent air over Egypt, the Red Sea and the Arabian desert.

A year ago, Solar Impulse’s batteries overheated during the plane’s Pacific crossing. That forced a months-long gap in the flight plan while the battery system was upgraded. This time around, the Solar Impulse team says the batteries should withstand the heat. Piccard will have to withstand it as well.

A successful return to Abu Dhabi will mark the end of a journey that included visits to Oman, India, Myanmar, China, Japan and a string of U.S. stopovers ranging from Hawaii to California to New York. Last month, Piccard made the Atlantic crossing to Spain, which set the stage for the final flights to Cairo and Abu Dhabi.

The end of the round-the-world circuit won’t spell the end of the adventure. Piccard and Borschberg say they’re establishing a non-governmental organization called the International Committee of Clean Technology to build upon Solar Impulse’s legacy.

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