Astronomy Picture of the Day

Explanation: An example of solar-powered flight, NASA's Helios aircraft flew almost one hundred years after the Wright brothers' historic flight on December 17, 1903. Pictured here at 3,000 metres in in skies northwest of Kauai, Hawaii, USA in August 2001, the remotely piloted Helios is traveling at about 40 kilometres per hour. Essentially an ultralight flying wing with 14 electric motors, the aircraft was built by AeroVironment Inc. Covered with solar cells, Helios' impressive 247 foot wide wing exceeded the wing span and even overall length of a Boeing 747 jet airliner. Climbing during daylight hours, the prototype aircraft ultimately reached an altitude just short of 30,000 metres, breaking records for non-rocket powered flight. Helios was intended as a technology demonstrator, but in the extremely thin air 30,000 metres above Earth's surface, the flight of Helios also approached conditions for winged flight in the atmosphere of Mars.