|The fuel-cell UAV in flight. Click to enlarge.|
Researchers at Georgia Institute of Technology have conducted successful test flights of an unmanned aerial vehicle (UAV) with a 22-foot wingspan powered by a 500-watt fuel cell.
The Georgia Tech team believes it to be the largest UAV yet to fly on the power from a proton exchange membrane (PEM) fuel cell using compressed hydrogen. AeroVironment’s 50-foot-wingspan fuel-cell UAV uses liquid hydrogen. (Earlier post.)
Other research groups have also demonstrated hydrogen-powered UAVs, but these aircraft were either very small or used liquid hydrogen (AeroVironment). Compressed hydrogen is less expensive than liquid hydrogen and relatively easier to work with.
In contrast to the micro UAVs, which had no landing gear and had to be hand launched, Georgia Tech’s demonstrator vehicle operates like a full-sized aircraft, requiring no auxiliary batteries or boosters for take-off.
The team extensively modified a commercial fuel cell stack for the UAV, adding systems for hydrogen delivery and refueling, thermal management and air management. The researchers also built control systems and a data acquisition systems to transmit flight data.
Among the design challenges:
Slim performance margins. Researchers developed innovative computer tools to analyze performance, which enabled them to optimize the propulsion system and aircraft design.
Weight management. Creative methods were used to trim pounds, such as using carbon foam for the power plant’s radiator.
Reducing drag, which the team achieved via the long, slender wings (spanning 22 feet), a streamlined fuselage, a rear-mounted propeller and an inverted V-shaped tail.
Miniaturization. The fuselage measured 45 inches in length with a maximum width of 9.75 inches and maximum height of 7.25 inches. Finding components small enough to fit in this space required some ingenuity, such as using a pump from a liquid-cooled computer and a hydrogen tank designed for a paintball gun.
In June, researchers tested the vehicle at the Atlanta Dragway in Commerce, Ga. Hot, humid, windy weather made testing conditions less than ideal and reduced thrust. Yet researchers were able to conduct four flights, with the aircraft traveling between 2.5 and 3.7 meters above ground for up to a minute at a time.
Especially important, the data generated during these flights validated our design methodologies. The data also indicated the aircraft is capable of longer, higher performance flights.—Blake Moffitt, Georgia Tech School of Aerospace Engineering
During the next few months, the team will continue to test and refine the aircraft, making it more reliable and robust. Ultimately, they plan to design and build an UAV capable of a trans-Atlantic flight.
As significant as it is, we are not merely developing a one-of-a-kind airplane. We’re working to define a systems engineering approach for fuel-cell powered flight.—David Parekh, GTRI deputy director and founder of Georgia Tech’s Center for Innovative Fuel Cell and Battery Technologies.
The project is a collaboration between Georgia Tech’s Aerospace Systems Design Laboratory (ASDL) and the Georgia Tech Research Institute (GTRI). In November, the researchers will present details of the project at the Society of Automotive Engineers’ Power System Conference in New Orleans.
The project is supported with internal funding from GTRI, along with grants from the National Aeronautics and Space Administration (NASA) and the National Science Foundation (NSF).
Boeing is working on developing a fuel-cell powered manned light aircraft. (Earlier post.)
Fuel Cells for Micro Air Vehicles (2005, Naval Research Laboratory)