Solar Impulse to fly world's longest solo flight from Japan to Hawaii

Doyle Rice | USA TODAY

Weather permitting, the sun-powered Solar Impulse 2 plane will continue its historic around-the-world journey this weekend with the longest, most perilous flight of its trip up next: A non-stop, four- or five-day flight over the Pacific Ocean from Japan to Hawaii.

This leg will be not only the world's longest solar-powered flight of all time, but it will also be the longest solo airplane flight (in time) ever attempted. Likening himself to legendary aviation pioneers such as the Wright Brothers and Charles Lindbergh, pilot André Borschberg called this "the moment of truth" for the mission and its team.

Unlike the first few legs of the flight, which were over land in Asia, there will be no landing the airplane if something goes wrong above the vast Pacific Ocean. Fellow pilot Bertrand Piccard (the two pilots have alternated legs of the journey) said that in the worst-case scenario, "a parachute and a life raft" would have to be used by the pilot to save his life.

Borschberg is flying this upcoming leg, which will span more than 4,000 miles. He'll only be able to take small, occasional naps while his team monitors the flight and will be bringing several hundred pounds of food, water and supplies on board.

Given the low speed of the ultra-light aircraft, the five-month round-the-world mission will take 500 flight hours — or nearly three weeks in the air — and cover about 22,000 miles. The Solar Impulse is the largest aircraft ever built with such a low weight, equivalent to that of a small car.

The journey began March 9 with a flight from Abu Dhabi, United Arab Emirates, to Muscat, Oman. To date, the pilots, both from Switzerland, have completed six legs of the mission. The seventh and most recent leg, from Nanjing, China, to Honolulu, Hawaii, had to be shortened because of bad weather, necessitating a landing in Japan on June 1.

The plane, which damaged its wing slightly upon landing in Japan, and both pilots have been waiting there for a weather window to open.

During the day, the plane charges its batteries by flying at an altitude of 27,000 feet — well above low-level clouds that can block the sun. The charge allows it to fly through the night.

"We need to find good weather for four days," Piccard said.

The plane needs clear skies to recharge the batteries, so clouds must be avoided, he said. Staying away from turbulence and strong winds is also important for the light-weight aircraft.

Meteorologists, air traffic controllers, engineers and mathematicians are all working from a control center in Monaco to ensure the flights go smoothly.

"Energy is what matters," Borschberg said. "We need to be in a sunny environment."

Once the plane reaches Hawaii, the next flight will be over the Pacific to Phoenix. From there, Solar Impulse will land at a location in the Midwest, then New York City, then two final flights over the Atlantic Ocean and the Mediterranean Sea before landing back at Abu Dhabi.

In addition to aviation records, the pilots, who are the mission's founders, also want to raise awareness about climate change, showcasing what can be done using nothing but renewable energy.

"The most important thing isn't to make world records," Piccard said. "It's to show what we can do with clean technologies," he said, ones that could simultaneously reduce carbon dioxide (CO2) emissions and stimulate economic growth.

"We will never improve the situation if we continue to speak of climate change as a big and expensive problem, or by asking people to reduce their lifestyle to protect nature," he said.

The burning of fossil fuels such as gas, oil and coal releases carbon dioxide into the atmosphere, which is heating up the planet to levels that cannot be explained by natural variability. Since the late 1800s, the Earth's temperature has risen by more than 1 degree.

"There are a lot of clean technologies that have been used to make Solar Impulse fly day and night without fuel," Borschberg said. "It is the first airplane with an unlimited endurance."

He added: "Many of these energy efficient solutions are starting to be commercialized, as they are economically attractive and have real potential to considerably reduce worldwide energy consumption."

Citing the fantastic potential of clean energy sources such as solar, Piccard said he wants to let people know that the technology in the Solar Impulse could be used in cars, houses and other places.

"We want to bring solutions, not just talk about problems," Piccard said. "We want to demonstrate we can do incredible things. This is the project of my life."