Last summer, I went out to JFK Airport in New York to see the Solar Impulse, an amazing sun-powered plane that had just flown safely across the U.S. An amazing plane, with a cabin the size of a Smart Car and the wingspan of a jumbo jet. Yes, with just 40 horsepower it cruised at a heady 43 mph, but it also flew at 27,000 feet.
Now there’s a Solar Impulse 2, unveiled in Switzerland Wednesday, and it’s doing more than continent-hopping—it’s going around the world next year. This plane weighs just 5,000 pounds, has 17,000 solar cells built into its wings, and operates on four beefed-up electric motors that grab stored solar power from a bank of lithium batteries (themselves adding 2,077 pounds to the weight).
The batteries are essential, despite the big weight penalty, because this plane is going to fly night and day, through clouds and sun. Flight training is scheduled for next spring, followed by the round-the-world trip between March and July 2015. Maybe 20 days of that will be flying time but they'll have to stay in the air for days at a time to cross oceans.
This is by no means a non-stop flight, although Solar Impulse 2 (unlike its predecessor) has a toilet. It's got an autopilot function, too. The plan is for an easterly route through the Northern hemisphere, with stopovers to change pilots in India, Myanmar, China, the U.S., Southern Europe or North Africa. The starting and ending point is somewhere in the Persian Gulf.
The flight will be a real test of the pilots, since they’ll be in a tiny unpressurized cabin for an accumulated 500 hours of flight time. It’s either really cold or boiling up there, and they’re relying on high-tech foam insulation to keep them comfortable. They’ll be carrying a life raft and six oxygen bottles.
But these guys are up to it. André Borschberg and Bertrand Piccard are already aviation legends. Piccard was at the controls of the Breitling Orbiter when it made the first nonstop round-the-world balloon trip in 1999. Piccard’s father explored the Mariana Trench in a bathysphere in 1960, and his grandfather, Auguste, was the first balloonist to reach the stratosphere in 1931.
Borschberg is a mechanical engineer with an advanced degree from MIT and lots of flight time in the Swiss Air Force. One or the other of them is going to be at the controls as they go around the world. Sure, this is an adventure, but it also has a serious purpose, which is proving the durability of solar-powered flight, and also the endurance of battery technology. The cells in Solar Impulse 2 are much improved from the first version of the plane.
When I met the pair in New York, a group of city schoolkids was in attendance, and they asked questions like, “What do you guys eat with no refrigerator?” and “How do you fly when the sun isn’t out?” The answers—freeze-dried stuff or sandwiches, and, well, we can’t always fly if the panels aren’t producing anything and the batteries are empty. This kind of flight—like the balloon trips—are very, very dependent on good weather. But Solar Impulse 2 is better able to keep flying through clouds, and it's more durable, too.
Trips like this depend on lots of cool technology, but the balloon attempt failed twice before it succeeded. Luck is part of that, too. Here's the plane's unveiling ceremony on video: