Inside the solar-powered plane that crossed the US

A view out to the end of the wing, which cants upwards slightly. The wing supports a total of four engines, and is covered in solar panels.

John Timmer

Three years ago, as I was in Switzerland to visit the Large Hadron Collider, a cousin of mine mentioned that they were testing a solar-powered plane at the airfield near his home in Lausanne. If a lightweight, human-powered plane managed to cross the English Channel, a solar-powered craft seemed like an obvious extension (in fact, the same team later crossed the channel in a solar aircraft). Whatever the Swiss were up to, it didn't strike me as that big a step. But with the arrival of that same aircraft in New York City last week, I got a much better sense of what's going on.

In the intervening years, Solar Impulse proved that it WAS a bit more than some solar panels slapped on a lightweight design. It managed to take off without any fuel and complete a flight that lasted more than 24 hours, and it later successfully flew from Europe to North Africa. Its arrival in New York City (see a gallery here) was the final leg in a flight that started over the Pacific Ocean near San Francisco. Ultimately, the aircraft is just a testbed for what will eventually be the first flight around the world to be performed without any fuel.

Solar Impulse, by the numbers

Despite its enormous wingspan (over 63 meters, or 208 feet), Solar Impulse is a relative lightweight, tipping the scales at 1,600kg (3,500lbs). Its basic shape is that of a glider: a long, extensive wing to provide lift and a narrow body to minimize wind resistance. In fact, it's part of the normal flight plan to use it as a glider for several hours (more on that below). Nevertheless, it does have four engines, each rated at 10 horsepower, and these are capable of driving the propellers at 400rpm.