Solar aviation history
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The Solar Impulse is not the first solar airplane imagined by man, but it is certainly the most ambitious. None of its predecessors has ever managed to fly right through the night with a pilot on board. Solar aviation began with reduced models in the 1970s, when affordable solar cells appeared on the market. But it was not until 1980 that the first human flights were realized. In the United States, Paul MacCready's team developed the Gossamer Penguin, which opened up the way for the Solar Challenger. This aircraft, with a maximum power of 2.5 kW, succeeded in crossing the Channel in 1981 and in quick succession covered distances of several hundred kilometres with an endurance of several hours. In Europe, during this time, Günter Rochelt was making his first flights with the Solair 1 fitted with 2500 photovoltaic cells, generating up to 2.2kW. In 1990, American Eric Raymond crossed the United States with Sunseeker in 21 stages and 121 flying hours over a period of almost two months. The longest lap was 400 kilometres. The Sunseeker was a solar motor bike-sail plane with a smoothness of 30 for a tare weight of 89 kg and was equipped with solar cells in amorphous silicon. In the middle of the 1990s, several airplanes were built to participate in the ‘Berblinger’ competition. The aim was to be able to climb to an altitude of 450m with the aid of batteries and to maintain a horizontal flight with the power of at least 500W/m2 of solar energy, corresponding to about half of the power emitted by the sun at midday on the equator. The prize was won in 1996 by Professeur Voit-Nitschmann’s team from Stuttgart University, with Icaré II (25 metres wingspan with 26 m² of solar cells.) Even if it did not allow a pilot on board, one could not forget Helios, developed by the American company AeroVironment for NASA. This remote controlled aircraft, with a wingspan of more than 70 meters, established a record altitude of nearly 30 000 metres in 2001. It was destroyed during a flight two years later, probably by turbulence, and crashed into the Pacific Ocean. In 2005, Alan Cocconi (picture), founder of AC Propulsion, succeeded in flying an unmanned airplane (drone) with a 5-metre wingspan for 48 hours non-stop, propelled entirely by solar energy. This was the first time a device of this type was able to fly through a whole night, thanks to the energy collected by, and stored in, the solar batteries mounted on the plane. And in September 2007 and again in August 2008, the Anglo-US company QuinetiQ flew 54 hours, then 83 hours 37 minutes, with its drone Zephyr (27 kg, wingspan 12m), at altitudes of 18 000m. “The pioneer is not always the one who succeeds, but the one who is not scared to fail.” Bertrand Piccard br> |