The benefits of using hydrogen fuel cells to power UAVs have been shown by the Naval Research Laboratory (NRL) with its Ion Tiger UAV setting an unofficial flight endurance record of 26 hours and 1 minute while carrying a 5-pound payload. While taking advantage of hydrogen as a high-energy fuel, the electric fuel cell propulsion system onboard the Ion Tiger also boasts the low noise and signature of a battery-powered UAV.

The Ion Tiger is a UAV research program that merges two separate efforts - UAV technology and fuel cell systems. The Ion Tiger weighs approximately 37 pounds and carries a 4- to 5-pound payload. The 550 Watt (0.75 horsepower) fuel cell onboard the UAV has about four times the efficiency of a comparable internal combustion engine and the system provides seven times the energy in the equivalent weight of batteries. Meanwhile, its small size, reduced noise, low heat signature and zero emissions contribute to its stealthy characteristics.

The Ion Tiger uses Polymer Electrolyte Membrane (PEM) fuel cells—also called Proton Exchange Membrane fuel cells – the type of fuel cell typically used by the automotive industry. This latest flight test improves on Ion Tiger's previous unofficial flight endurance record of 23 hours and 17 minutes that took place just a month earlier and demonstrates that PEM fuel cells can meet or surpass the performance of traditional power systems, providing reliable, quiet operation and extremely high efficiency.

That the new record set by the Ion Tiger more than doubles the record of nine hours set by the fuel cell hybrid powered Puma small unmanned air vehicle (SUAV) just a year and a half ago is an indication of the enormous strides being made in hydrogen fuel cell technology.

Next the NRL will focus on increasing the power of the fuel cell to 1.5 kW, or 2 HP, to enable tactical flights and extending flight times to 3 days while powering tactical payloads.