Unmanned Plane Flies on Solar and Battery Power

AC Propulsion has successfully flown an unmanned aircraft for more than two days using only solar energy. The “SoLong” craft stores solar energy in a lithium-ion battery pack during the day to keep it flying at night. The plane weighs only 28lbs with a wingspan of slightly more than 15 feet. Seventy six sunpower solar cells along its wing produce 225W of power; the craft required only 95W for level flight. According to the company, a critical factor in the SoLong’s success was its high-efficiency electric motor, driven by the company’s patented power controller. The radio-controlled craft features 23 channels of telemetry, navigation data from a global positioning system, and even a live video downlink. AC Propulsion claims that the SoLong could have remained flying indefinitely.

Bertrand Piccard plans to design and build a solar-powered airplane, Solar Impulse, that will circumnavigate the world. Solvay, Altran, and Dassault Aviation have signed on as financial and technical partners. The European Space Agency is also continuing to provide its expertise, which led to a model unveiled in mid-June. The craft will have a 262' wingspan and will weigh only two tons, carrying a single pilot. Piccard hopes to build the craft by 2007 and begin test flights the following year. The actual circumnavigation in 2010 will involve four- to five-day flights with stops on each continent to change pilots.