Fuel Cell Powered Flight Project
David E. Parekh, Blake A. Moffitt, Thomas H. Bradley, and Dimitri Mavris
Georgia Institute of Technology,
Fuel cells hold promise for long-endurance flight due to their efficiency compared to
traditional internal combustion based propulsion. However, the power density of current
systems falls far below what would be needed for flight applications. To begin
addressing these gaps in required performance, a systems-based research approach has
been undertaken to design and develop a fuel-cell powered unmanned air vehicle (UAV).
Beginning with a baseline of currently available commercial systems, research has
focused on optimal design and integration and on identifying technology innovations that
can have the largest impacts on the system performance. Along with developing a
specific demonstrator aircraft, this work establishes a generalized approach for future
design of this emerging class of aircraft.
To establish a foundation for the design of fuel-cell powered aircraft, a conceptual design
was performed that purposely made very few assumptions about interactions between the
various aircraft subsystems. Instead, a large design space was defined by a vast range of
fuel cell technology and power levels, a large range of highly efficient electric motors,
multiple hydrogen storage schemes, and various parameters defining the size and shape
of the aircraft. A full-factorial search of this design space was performed and feasible
aircraft configurations were identified. Response surface methods were then used to
study trends and design tradeoffs. Based on optimizing a combination of performance
metrics, a conceptual design was selected that became the basis for the demonstrator
aircraft. In addition, as systems of the aircraft were completed and tested, the conceptual
design tools were further calibrated and portions of the design process were repeated to
improve the final design of the aircraft.
Once the conceptual design was understood and a high-performance configuration had
been selected from the design space, the low-level system design and integration began.
This portion of the project included the design and construction of three prototype aircraft
with detailed analysis of the weight and function of the aircraft and powerplant
components. The low-level design of the fuel cell and powerplant system included the
specification and engineering of a variety of systems for maximum efficiency and
performance. Custom fuel cell stack structure, compressors, hydrogen management
system, control system and a custom carbon foam radiator were designed and
implemented over the course of the low-level fuel cell design and integration task. The
performance of the fuel cell powerplant was measured within the aircraft and under
experimental settings.
A flight test program was developed to fine tune the 20-foot-wing-span UAV design.
The fuel-cell based propulsion system was developed and integrated into the third
prototype and flown for the first time in June 2006. On-board instrumentation provided
some rudimentary evaluation of the propulsion system performance. Preliminary
analysis of this initial flight test data and comparisons with lab and model data has been
accomplished.
This work is sponsored by NASA and the Georgia Institute of Technology.