Solar Powered Airplane Is Here!
Solar Powered Sport Flying on the Horizon - Eric Lentz-Gauthier
I stand mid-field at a small airport nestled in the countryside outside of Milan; Solar Flight’s flight test facility. The Sunseeker Duo is at the far end of the runway beginning its takeoff roll with its designer, Eric Raymond, in the cockpit. For 25 years Solar Flight has been on a quest to build the ultimate solar powered airplane. The Sunseeker Duo is the result. It is the third airplane in Solar Flight’s Sunseeker family, the highest performing solar powered airplane ever built, and the first with a passenger seat.
Solar Flight is led by the husband and wife team, Eric and Irena Raymond. Eric is old school; an engineer, a builder, and a pilot who isn’t afraid to get his hands dirty. He comes by his fascination for pioneering honestly; his father designed underwater camera housings for Cousteau and his cronies, and the home where he grew up was a revolving door of engineers and explorers. Solar Flight carries this pioneering flame. It is only the third time the Duo has flown under its own power. The airplane is so light and its wings so large that it takes off effortlessly. On the ground the airplane is enormous. Its wings droop slightly under their own weight and, though the airplane handles well on the ground, it is obvious that it would rather be somewhere else. With a little speed, the wings lift to life, the wheels leave the ground and retract into the fuselage. The way you can tell when a dog smiles, you can tell the Duo is happy in the sky.
Electric power is the new great era for aviation pioneering, and sport aviation is where electric power has the most immediate promise. The advantages of electric drivetrains in aircraft are significant. Electric motors are supremely reliable, they require almost no maintenance, and cost next to nothing to operate. Their small size and low weight opens possibilities for novel airframe configurations and their efficiency, often above 90%, means less energy used making heat and noise. Energy storage remains the major limitation, but the Sunseeker family sidesteps the energy storage problem by flying directly on solar power. 1510 solar cells are integrated into the structure of Sunseeker Duo’s wings and tail surfaces; each cell provides about 3 watts of power.
The Duo is silent when it lifts off the ground. As it nears me it becomes faintly audible. There is only a faint sound of wind through the propeller; I have heard more noise from a house fan. Sound is energy and energy used to produce sound is energy wasted; the Duo’s silence is testimony to its efficiency. Design of the Sunseeker Duo began in 2010, and construction later that year. It was built in a small workshop in Radovljica, Slovenia, near Irena’s childhood home and the airport where she learned to fly. The town is an epicenter of composites industries; factories that make skis, boats, windmill blades, and sailplanes are all found here. There is no zoning in the town. Factories are mixed between houses, horse stables, and small restaurants. On the edge of town is an ancient fortress that once guarded the pass to Austria through the Julian Alps. The site, within cycling distance of Solar Flight’s workshop, served as a lunch destination during the Duo’s construction. The location is a fitting birthplace for such a fantastical machine. To keep weight down, the Duo relies on carbon fiber for its main structures. No detail is overlooked. “There is a cascade effect of weight reduction; if you switch to a lighter motor, the motor mount can be lighter, and so can everything else, down to the landing gear. When you go around the design loop a second time, even the wings can be smaller to maintain the same wing loading. The weight goes down and down like a ripple effect through the whole plane every time you substitute a steel part for titanium or aluminum.” Says Eric Raymond. The Duo has been around this loop more than a few times. The result is an airplane that is faster, more robust, and more capable than any solar-powered airplane ever built. When it came time to begin test flying, the project moved to an airport in Voghera, Italy. The location is quiet and out of the way, perfect for Solar Flight’s somewhat secret endeavors. Most of the company’s work is consulting done for outside projects. Recent projects include the Boeing Vulture UAV, the Lockheed HALE airship, Solar Impulse’s HB-SIA. Sunseeker Duo’s solar integration is unique in the group. The Duo integrates the solar arrays into the structure of the wing rather than “floating” them on top of the structure, it is the most advanced solar integration in any aircraft to date. Like the single seat Sunseeker, the Duo is built for sport flying and adventure touring. In 1990, to prove the concept of a practical solar powered airplane, Raymond flew Sunseeker I across the United States - the first solar powered airplane to cross America. In 2009 with an updated airplane, Sunseeker II, Raymond made a European tour that included the first Alps crossing by a solar powered airplane.