Solar-powered plane stops in Cincinnati on its way to D.C.

Alan Boyle, Science Editor NBC News

Solar Impulse

The solar-powered Solar Impulse plane comes in for a landing in Cincinnati on Friday.

The Swiss-made Solar Impulse plane touched down in Cincinnati on Friday for an overnight layover before continuing on to Washington, D.C.
The solar-powered plane has been making its way across America with nary a drop of fuel, which means it didn't have to fly down for a fillup. Rather, the stop was added to Solar Impulse's itinerary because of concerns about windy weather and the pilot's stamina.
Solar Impulse gets its energy solely from the 12,000 photovoltaic cells mounted on its fuselage. That provides enough juice to propel the plane's scooter-sized motors, but it's slow going. The super-light plane can travel no faster than 50 miles (80 kilometers) per hour – and Friday's head winds made the pace even slower.
The cross-country trip's planners determined that pilot Andre Borschberg, Solar Impulse's CEO, couldn't make the nonstop trip to Washington in less than 24 hours, which is the limit set for time in the cramped single-seat cockpit. That's why the Cincinnati stopover was added.
Borschberg took off from Lambert-St. Louis International Airport at 4:01 a.m. CT Friday, and landed in Cincinnati at 8:15 p.m. ET. Solar Impulse's chairman, Bertrand Piccard, is due to take the controls for the next leg of the journey starting at 8 a.m. ET. Arrival at Washington's Dulles International Airport is expected around 1 a.m. ET Sunday.

Solar Impulse: A fuel-free flight across America

Fred Merz

The Swiss-made plane is attempting a record-breaking trip across the U.S. powered only by the sun

Solar Impulse's "Across America" adventure is aimed at highlighting the plane's technologies for American audiences, and preparing the way for an even more ambitious round-the-world odyssey in 2015. The carbon-composite plane has the wingspan of a Boeing 747 jet but is as light as a passenger car. The excess energy generated by the plane's solar cells is stored in 880 pounds' worth (400 kilograms' worth) of batteries. That's what allows the plane to fly through the night.
The 10-year-old project is backed by 90 million euros ($115 million) in investment by Swiss sponsors. Before coming to America, the plane went through a series of record-setting flight tests in Europe and Africa.
The American voyage officially began on May 3 with Solar Impulse's takeoff from Moffett Field in Mountain View, Calif., and continued with stopovers in Phoenix, Dallas and St. Louis. The journey is expected to end with a Washington-to-New York flight in early July.
Solar Impulse's organizers are offering a wide array of outreach activities — including streaming video of Saturday's flight. The plane will be shown off at the National Air and Space Museum's Steven F. Udvar-Hazy Center at Dulles, and Energy Secretary Ernest Moniz is due to meet up with the Solar Impulse crew for a roundtable and news conference on Monday.