It’s big. It’s being shown here for the first time. It has four engines. It flew many hours to get to Le Bourget.
The Boeing 747-8?Oh, and it used no fuel on the trip.
That narrows the field down to just one: Solar Impulse.
The first aircraft designed to fly by day and night without requiring fuel and without producing carbon emissions, Solar Impulse was developed over a seven-year period by a team led by Bertrand Piccard, who was the first man to fly a balloon nonstop around the world, and engineer and professional pilot André Borschberg. Their aim is to demonstrate the potential of new technologies for energy savings and renewable energy production.
With Borschberg at the controls, Solar Impulse took off at 5:10 a.m. last Tuesday from Brussels Airport, heading for Paris via Maubeuge, Reims, Troyes and Avallon. Sixteen hours and five minutes after takeoff, including holds for traffic and weather conditions, Borschberg landed here at Le Bourget, parking on the ramp close to where Charles Lindbergh made his historic landfall after the first nonstop solo transatlantic flight in 1927. Average speed over the 363 nm route was 22.5 kt, maximum altitude 31,000 ft.
A Satcom system developed by one of Solar Impulse’s 80 project partners, Swisscom, enabled flight director Raymond Clerc and his team to support the pilot throughout the flight from their mission control center in Payerne, Switzerland.
Solar Impulse will be on display here every day from June 20 to June 26 on Stand G301, opposite the Solar Impulse Chalet A394. Weather permitting, it will make a uniquely silent demonstration flight each morning.
Among the Solar Impulse project’s supporters are Solvay, Omega, Deutsche Bank and Schindler as principal partners; Bayer MaterialScience and Altran as official partners; Lausanne Federal Institute of Technology as scientific consultant, and Dassault Aviation as aviation consultant.
Constructed around a skeleton of carbon fiber and honeycomb composite materials, Solar Impulse has a wingspan of 208 feet – similar to that of an Airbus A340 – and the aircraft weighs 1,600 kg – no more than a typical family automobile. The upper surfaces of its wings and tailplane are covered with a skin of 12,000 encapsulated photovoltaic solar cells, and the undersides with lightweight flexible film. Solar Impulse is powered by four 10-hp electric motors that in turn are fed by 400-kg batteries charged by the cells in the flying surfaces, so that the energy stored during the day enables the aircraft to fly at night.
Each of Solar Impulse’s four underwing engine pods contains a motor, a polymer lithium battery consisting of 70 accumulators, and a management system controlling the charge threshold and temperature. The thermal insulation has been designed to conserve the heat radiated by the batteries and keep them functioning despite the -40 °C encountered at typical cruising altitudes of up to 30,000 ft. A gearbox limits the rotation of each 11.5-foot-diameter, two-blade propeller to 400 rpm.
An onboard computing system gathers and analyzes hundreds of flight management parameters, giving the pilot information to interpret for making decisions, transmitting key data to the ground team and – most important – providing the motors with optimal power for the particular flight configuration and battery charge/discharge status.
Energy management is key to the entire project. At midday, each square meter of surface, in the form of light energy, receives the equivalent of 1,000 watts, or 1.3 hp 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 Solar Impulse’s motors achieve an average power of no more than 8 hp, roughly that available to Wilbur and Orville Wright when they made their first powered flight in 1903. That energy, optimized from the solar panels to the propellers, makes it possible to fly by day and night without conventional fuels.
—Michael Jerram
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