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 …