The Ion Tiger UAV recently completed a record 48-hr, 1-min flight powered by a liquid-hydrogen-fed fuel cell. The powerplant gives the aircraft the low noise and IR signature of a battery-powered UAV and the efficiency of using high-energy liquid hydrogen and fuel cells.

The plane was developed at the U. S. Navy Research Laboratory, and the flight broke a record set by the Ion Tiger in 2009. For that flight, however, its fuel cell was powered by gaseous hydrogen stored at 5,000 psi, and it stayed aloft for 26 hr and 2 min.

Liquid hydrogen is three times as dense as 5,000-psi hydrogen gas, which gave the revamped UAV more endurance. The key to using the cryogenic hydrogen was development of a lightweight, insulated, and vented container which could serve as the fuel tank. To make the technology suitable for battlefield drones, researchers will need to develop a portable electrolyzer and compressor to pull hydrogen out of water and refrigerate it using electricity, possibly from solar cells or wind turbines.

Resources: U. S. Naval Research Laboratory