NASA's Helios prototype spans new heights

It has a wingspan longer than a Boeing 747, weighs less than 900 kg, incorporates 14 solar-powered propellers and it's the highest flying propeller-powered aircraft in the world. With its soaring profile and radical "flying wing" design, NASA's Helios prototype is set to revolutionise air-based communications platforms, the placement of low orbit satellites and even unmanned flights in the Martian atmosphere.