Borschberg launched his final flight in Solar Impulse 2 from Seville, Spain, on July 11, and 16 hours into what would be a flight of 48 hours and 50 minutes, he was working to occupy his mind and hands.
“There is nothing to do except rest,” said the voice from mission control in Borschberg’s ear, broadcast live around the world via YouTube, along with flight telemetry and images from the cockpit.
“For your information, something funny,” Borschberg was told. “It’s colder in the cockpit than outside.”
The outside air temperature was 39 degrees Fahrenheit, and the cockpit interior was just below freezing. Borschberg mused that the insulation was a little “too good,” but opted not to open the window.
Borschberg landed July 13 after covering 2,327 miles across the Mediterranean Sea, at an average speed just over 41 knots. While shorter in distance and duration than Borschberg’s record-setting five-day trip from Japan to Hawaii, his final flight of the solar circumnavigation owns the distinction of traversing the largest number of distinct airspaces in a single mission.
Co-founder Bertrand Piccard, who has taken turns with Borschberg piloting the 16 legs to date, will bring Solar Impulse back to Abu Dhabi, United Arab Emirates, where the journey began in March 2015.
“This was an emotional and meaningful leg for me, being able to enjoy once more the incredible sensation of flying day and night thanks only to the energy of the sun and enjoying fully the present moment,” Borschberg said in a news release after landing. “It also brought back many memories about the project: from the moment I heard about Bertrand’s incredible vision of an airplane with perpetual endurance, to the creativity, motivation and spirit demonstrated by the entire team and partners throughout this adventure.”
Piccard also reflected on how far the solar-powered airplane, and his vision of promoting clean technology and inspiring others has come.
“This landing in Cairo brings Solar Impulse back to the origin of my dream. Egypt is the country where I landed after my non-stop round the world balloon flight in 1999, and it’s precisely here that I had the idea of an airplane flying around the world on solar power,” Piccard said in a July 13 news release. “André and his team of engineers helped to translate my vision into reality, and I congratulate them for having built such a revolutionary airplane.”
The revolution has not been without challenges. The team spent months in Hawaii repairing and redesigning the electrical system, after the batteries overheated on the first leg of the Pacific Ocean crossing. After repairs and testing, the journey resumed in April, and Solar Impulse landed in Mountain View, California; Phoenix; Tulsa, Oklahoma; Allentown, Pennsylvania; and New York City before crossing the Atlantic Ocean in June and landing in Spain. Outside of the overheated batteries, there have been few technical faults, though Piccard noted in the July 11 press release that the team is taking nothing for granted.
After more than 22,000 miles, “people might start to find it obvious to fly day and night without fuel, but it’s still a very difficult endeavor and the challenge will remain open until the last minute,” Piccard said.