In 2003-2004 Giner Electrochemical Systems, LLC put me in charge of building a MATLAB/Simulink model that automatically optimized the design of a fuel cell-based power generation system for a stated 2-week high-altitude, long-endurance (HALE) aircraft mission. NASA and other government agencies were convinced that an air-breathing, liquid hydrogen fueled engine would provide the lowest-weight HALE aircraft power plant. Accordingly, they hired us to determine the weight and volume of such a hydrogen-fueled proton exchange membrane (PEM) fuel cell-based system. Other firms optimized the design of alternative power plants, such as a hydrogen-fueled internal combustion engine.
AeroVironment is developing both types of aircraft. In 2005 they demonstrated a 1/4-scale version of their Global Observer HALE aircraft that was driven by a liquid hydrogen-based fuel cell engine. Earlier this month (1/11/2011) AeroVironment's full-scale, liquid hydrogen-fueled, internal combustion engine-based Global Observer took its first flight, lasting four-hours. Ultimately, with its 175 foot wingspan, it will operate for up to a week at 65,000 feet.
Its always good when the theoretical becomes reality!