Think of the Green Flight Challenge flown on a much smaller course, but allowing hydrogen fuel cell powered balloons to compete against liquified natural gas powered ultralight aircraft, or solar-powered autogyros. You might get a small idea of the creativity and innovation that sponsors hope to unleash in an upcoming event. In the town of Vichy, France, at the Vichy-Charmiel airfield, on July 9-11, the Eco Marathon ULM (Ultra Light Machines) will be held to test the limits of how little energy can be used to fly an aerial craft around a closed-circuit course three times. The rules are simple. The craft using the least energy wins – like the CAFE Foundation’s 2011 Green Flight Challenge, and inspired by the Shell Marathons for high school students who build extreme vehicles that get extreme mileage. There are no speed or weight requirements outside those imposed by the French Civil Aircraft Authority (the DGAC) on the various types of aircraft. Since participants …