First Solar-Powered Flight Around the World

Swiss adventurer Bertrand Piccard unveiled Friday the prototype of a solar powered plane he plans to fly around the world to highlight the potential of alternative energy sources.

The project was launched in 2003 and after six years' work by 70 engineers and technicians on the Solar Impulse, which has a number of high profile backers including Deutsche Bank, watchmaker Omega and Swiss chemicals maker Solvay and a budget of 70 million euros ($97.53 million).

The Impulse has the wingspan of a Boeing 747-400 and the weight of an average family car (1600 kg), resulting in new standards for size to weight. Over 12,000 solar cells mounted onto the wing will supply renewable energy to the four electric motors with a maximum power of 10 HP each. During the day they will also charge the lithium-polymer batteries (400 kg), which will permit the HB-SIA to fly through the night.

The question of energy determines the whole project, from the structure’s dimensions to the extreme weight constraints. At midday, each m2 of land surface receives the equivalent of 1000 Watts, or 1.3 horsepower of light power. Over 24 hours, this averages out at just 250W/m2. With 200m2 of photovoltaic cells and a 12 % total efficiency of the propulsion chain, the plane’s motors achieve no more than 8 HP or 6kW – roughly the amount of power the Wright brothers had a available to them in 1903 when they made their first powered flight. And it is with that energy, optimized from the solar panel to the propeller by the work of a whole team, that Solar Impulse is striving to fly day and night without fuel!

The HB-SIA is the first prototype of the Solar Impulse project. Its mission is to demonstrate the feasibility of a complete day-night-day cycle propelled solely by solar energy. After fine-tuning on the ground, the aircraft should make its first test flights between now and the end of 2009, first of all at Dübendorf airport. A first complete night flight is programmed for 2010 and will take place over Switzerland.

The results from the HB-SIA and their analysis will serve to develop and build a second aircraft, the HB-SIB for circumnavigating the word in five stages, each lasting several days, in 2012.

The pilots will spend 36-hours in the plane's tiny one-man cockpit and fuselage in initial flights to test its ability to fly overnight. The round-the-world attempt will be made in five stages, each lasting several days.