A prototype solar-powered airplane completed several important tests last Thursday and Friday.

Solar Impulse's HB-SIA, which was finished this past summer, taxied down a runway using power from the 11,000 solar cells covering its wings and did a series of acceleration and braking tests. The next test will be revving up the plane to its 35km/hour take-off speed.

Founder of Solar Impulse, Bertrand Piccard, a former astronaut and the first man to circle the world nonstop in a balloon, hopes to perform the same feet in a solar-powered plane derived from on the HB-SIA design. Solar Impulse aims to test the prototype in flight next year and to achieve a 36-hour flight without fuel shortly after that. Results from these tests will be used to build a solar-powered plane to will attempt a transcontinental flight sometime after 2012.

A number of solar-powered aircraft exist already, such NASA's Helios, the Solar Riser glider or the Sunseeker which flew across the US in 1990 using a mix of solar power and gliding.

The Solar Impulse prototype is made of lightweight materials, weighing only 3,500 pounds and it has a wingspan of 210 feet. It is intended to fly at only 28 miles per hour to keep energy consumption low. It will store solar energy for night flight.

The video below shows computer simulations of Solar Impulse's plane, and the real thing on the runway.

The major failure of air-traffic control yesterday was yet another sign that our outdated radar-based system needs to be replaced with a sleek new satellite-based one, right? That's the logical progression of much of the coverage out there.

The reality is that, yes, the system needs to be replaced. But yesterday's failure was a high-tech one that could afflict a system based on satellites, too.

The problem wasn't directly related to radar, but with the National Airspace Data Interchange Network, a system for processing flight plans and information for all flights in the country. It failed in both of its locations: Salt Lake City and Atlanta. This meant that automated regional FAA systems couldn't process flight information. As a result, controllers had to enter information manually. This caused delays that rippled across the country. "A satellite-based system would have had the same problem," R. John Hansman, an MIT aerospace and air traffic control expert, wrote to me this afternoon.

The Federal Aviation Administration hopes to roll out a Global Positioning System-based control system, called Next Generation or NextGen, in stages. By 2020 most planes will carry a cockpit gadget that continuously broadcasts the planes' GPS-derived location, altitude, and speed to ground controllers. In later years, the system will extend so that this information is picked up by other planes, too, so that pilots can gain more control over their routing and spacing. As they beam their position information to one another they'll be able, to some extent, to self-navigate. However, there will always be an FAA air-traffic system keeping track. It's unlikely that pilots will ever be permitted to make all takeoff, routing, and landing decisions entirely by themselves in the event of failures of national air-traffic computers, as happened yesterday.