The U.S. Navy is interested in unmanned systems for numerous reasons, such as offering reduced manning and creating the ability to carry out missions in environments hostile to humans. However, numerous challenges remain, such as the limited endurance of battery-electric vehicles. At NRL, we targeted the limited endurance of battery-electric unmanned air vehicles (UAVs) proposing hydrogen fuel cells as a path to long-endurance propulsion. NRL developed the Ion Tiger UAV, first using a 1.1-kg 550-Watt fuel cell built by Protonex Technology Corporation in the power train. The Ion Tiger flew for 26 hours on hydrogen fuel cell propulsion in November 2009 using compressed hydrogen gas as the fuel, and 48 hours in April 2013 using liquid hydrogen fuel. More recently, NRL has designed and built in house a flight-weight, modular 1.5 to 5 kW PEMFC using metal bipolar plates as the backbone – first with 3D printed titanium bipolar plates, and more recently using automotive-grade, formed stainless steel bipolar plates. We have also developed the methodology to make catalyst-coated membranes in house to speed development of new designs.
The overall success of our hydrogen UAV program is due to advances in materials, electronics, and thermal management, integrated into an aerodynamically efficient package. The resulting fuel cell–powered UAVs are relatively small (35 to 100 lbs) but they are quiet and efficient, allowing them to do “big airplane” missions. The full system approach, with basic and applied research as its foundation, is clearly a tribute to the corporate research approach that Dr. Kunz espoused.