We told you about the plans and simulations last May, but now a couple of bold Swiss adventurers just unveiled a prototype of Solar Impulse, a carbon fiber solar-powered airplane they plan to fly around the world in 2011. The 3000-pound aircraft will have a wingspan that's about the same as the Airbus A380, but instead of streaking around the globe at 560 mph, this one will poke along at a mere 40 mph. At that rate, it'll take four weeks for it to carry its single passenger all the way around the planet. Let's take a look at the details and more pics of the plane.

The solar cells on the wings will suck up power for a maximum seven to eight hours a day because of the angle of the sun. The pilot won't have to worry about clouds, though, because the plane will cruise at 42,000 feet. After sunset, the plane's designers hope batteries will power the plane through the night. They admit that battery technology isn't efficient enough now for this to work, but insist that it will be possible by 2011.

For now, they're planning to test-fly the prototype in 2009, with a smaller wingspan of 197 feet that flies for 36 hours at 27,000 feet. Will they make it? With $87.5 million backing up the project, who knows if they'll actually fly all the way around the world, but they'll probably have enough cash to at least mount an attempt. [Times UK, via Inhabitat]