Solar Airplane Poised for First Flight

Question:  When is it news that an airplane taxis down a runway?

Answer:  When it’s the first plane powered solely by solar power.

The HB-SIA is the first prototype of the Switzerland-based Solar Impulse project. Its mission is to demonstrate the feasibility of a complete day-night-day flight cycle propelled solely by solar energy – and using no fuel. The airplane recently completed a test run near Zurich Switzerland in which it taxied down the runway power by its own engines.

The HB-SIA is a totally unprecedented aircraft, with a 63-meter wingspan (comparable to a Boeing 747-400) and the weight of an average family car. Never before has such a large craft been built with such low weight. Over 12,000 solar cells mounted onto the wing supply renewable energy to the four electric motors with a maximum power of 10 HP each. During the day the cells also charge the lithium-polymer batteries, which will permit the HB-SIA to fly through the night. After four years of research, studies, calculations and simulations by the 70-person team, the HB-SIA represents the beginning of a new, more concrete, phase.

The first taxiing test involved low speeds with the prototype going through a series of acceleration and breaking maneuvers to check that the plane’s calculated and simulated strains are not being exceeded. During the test, computers monitored the plane’s behavior via embedded telemetric devices and the results met the designers’ expectations. Solar Impulse will conduct further runway tests, doubling the speed up to 10 knots.

“The runway tests are necessary and involve a certain amount of risk for the landing gear. The chances of damaging the plane are greatest during low-speed ground maneuvers. The faster the plane goes the more lift it gets from its wings, meaning that there is less load on the wheels”, explains André Borschberg, co-founder and CEO of Solar Impulse.

The next stage in testing will take the prototype up to its 35 km/h take-off speed so it can do short hops. These tests will allow the company to manage and record the numerous unknown factors that the aircraft will encounter in a real-life flight. If the results are conclusive, it could make a 36-hour flight - the equivalent of a complete day-night-day cycle – over Switzerland in 2010 without any fuel.

The results from testing the HB-SIA will serve to develop and build a second aircraft, the HB-SIB, that is designed to circumnavigate the word in five stages, each lasting several days, in 2012.