Aileron

The Solar Impulse 2 is a long-range solar-powered fixed-wing aircraft currently attempting to circumnavigate the world under solar power alone. Built in 2014, it began its attempt in March 2015 from Abu Dhabi, headed east across Asia, to Hawaii, and then eventually hopes to cross the United States, the Atlantic, and back to Abu Dhabi. The plane has a wingspan of 236 ft (compare to 196 ft of a B747), weighs 5100 lbs, and has a cruise speed of 49 kts. Four electric 17.4 hp motors are powered by batteries and solar panels on the wings. It charges its batteries and climbs during the day and then runs off batteries and descends at night.

I had the privilege of visiting the plane at the end of its ninth leg where it flew across the Pacific from Kalaeloa, Hawaii, to Mountain View, California. After passing security at Moffett Federal Airfield (KNUQ) and then being treated to a pair of F-18s taking off, we were welcome into the Solar Impulse's custom inflatable hangar. The plane looks delicate, like something from the future where people live in the sky. Its wings and empennage are fabric stretched over a thin frame. Its dimensions are that of a large glider, with long thin wings and a glide ratio of 40:1.

The crew in the hangar was busy preparing for the plane's next leg to middle-America, but they were also very interested in showing their guests around and answering questions. The team is passionate about demonstrating the possibilities of transport without fossil fuels and indeed, if it weren't for the human on board, the SI2 could remain in perpetual flight. But what fun is an airplane if we're all watching from the ground?

More seriously, it is a big point they're trying to drive home. The technology for emission-free transport is already here; it's just a matter of scaling it.

Solar Impulse 2 empennage

Solar Impulse 2 fuselage from under left wing