Researchers report they have set aloft the first large unmanned aerial vehicle powered solely by a compressed hydrogen fuel cell, the same kind of technology being developed for hybrid cars. Although it flew for no more than a minute, further refinements could potentially allow this type of aircraft to make a transatlantic voyage within five years.
Hydrogen fuel cells are desired for their ability to replace fossil fuel in some settings. Their core technology is the proton-exchange membrane, which extracts electricity from hydrogen and oxygen and gives off nothing but water vapor in the process. Prior flights of fuel cell aircraft have involved either small remote-control planes or those powered with liquid hydrogen. ¿Compressed hydrogen, which is what the automotive industry is using, is cheaper and easier to work with,¿ says Georgia Tech doctoral student Tom Bradley, who designed the new fuel cell propulsion system. Besides requiring no refrigeration to keep it liquid, compressed hydrogen also reduces a craft¿s weight, which is an important consideration because the energy density of compressed hydrogen is still only tenths that of gasoline or airplane fuel.
Georgia Tech researchers extensively modified a commercial fuel cell stack and wrapped the system inside a 45-inch-long, seven-inch-tall chassis with a 22-foot wingspan. This June they took it for a spin at the Atlanta Dragway in Commerce, Ga. Despite the drag imposed by high heat and humidity, the craft successfully flew four runs on a straight path; and in classic Wright Brothers style, each flight lasted for up to a minute at an altitude of eight to 12 feet. ¿We anticipate it should be able to fly eight to 10 minutes, but we¿re looking to extend that. We want to climb up well beyond the tree line,¿ says aerospace engineer Adam Broughton, who controlled the plane by remote control.
The challenge in a longer sustained flight is primarily hydrogen storage, Broughton adds, which means a transatlantic flight is in the realm of possibility. ¿It¿s something that¿s on the radar,¿ he says. The Georgia Tech group may have competition, though: Boeing hopes to test a hydrogen two-seater plane in the next year.