Eco Factor: Zero-emission prototype helicopter designed to fly on PEM fuel cells.

United Technologies Corp has demonstrated a significant breakthrough in hydrogen-powered flight, by fling an unmanned helicopter equipped with proton exchange membrane fuel cell for more than 20 minutes.

The helicopter has a rotor diameter of two meters. The RC helicopter was originally designed to fly on batteries, but was later modified to demonstrate the potential of hydrogen fuel cells. The team believes that the achieving vertical flight represents a milestone as the power requirements are much higher than what is needed to fly a fixed wing aircraft.

Via: Wired496772