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UAVs may fly longer on hydrogen fuel cells

Over the past decade, hand-launched drones have proven so useful that the military has bought more than 12,000 of them. Some weigh less than a pound and have wings that span just 2.4 feet. Others weigh 14 pounds and stretch 9 feet from wingtip to wingtip.

Small enough to be carried in a backpack, they can be snapped together in minutes and hurled into the air. Driven by battery-powered electric motors, they can usually stay aloft for an hour or two.

Now the military wants small drones with longer dwell times. It’s on the verge of getting them, thanks to hydrogen fuel cells.

Fuel-cell maker Protonex has shown it can fly a 14-pound UAV for nine hours on electricity generated by a hydrogen fuel cell and fuel cartridge that together are just bigger than a 2-liter soda bottle.

Now, with a $3.3 million contract from the Defense Department, Protonex plans to make a fuel-cell-and-cartridge combination that’s even smaller and has greater energy density, said Scott Pearson, Protonex chief executive.

The company’s new fuel cell is being designed to power to an AeroVironment Puma AE UAV. The 4.6-foot-long Puma has a 9-foot wingspan and carries electro-optical and infrared cameras for day and night surveillance. The fuel cell powers the cameras, communications gear and flight controls, as well as the electric motor that turns the plane’s propeller.

Protonex has built a variety of fuel cells to power UAVs. They produce 100 watts to 500 watts of continuous power, and use a lithium-ion battery to provide extra power for taking off or maneuvering. Electricity from the fuel cell keeps the battery charged.

Fuel-cell-powered UAVs fly two to four times longer than battery-powered UAVs, Pearson said.

Extra time in the air means U.S. troops are able to observe targets for longer periods and view larger areas before their UAVs have to return to refuel, said Lt. Mark Roosz, who works on fuel cell-powered UAVs at the Air Force Research Laboratory.

A small fuel cell-powered UAV is attractive to the military because it makes small, relatively inexpensive UAVs capable of performing persistent surveillance — something now done only by larger, much more costly drones, said Steven Gitlin, a spokesman for Puma producer AeroVironment.

The Puma AE may also be attractive to the Navy. “AE” in the name stands for “all-environment,” and the rugged, waterproof Puma can land at sea. AeroVironment is promoting it for maritime intervention operations, search-and-rescue missions, coastal and port patrols and drug interdiction operations.

Pumas are operated with a 6-by-10-inch hand-held controller that features a 4-by-6-inch screen that displays the UAV’s video feed, and five knobs for directing the UAV and its onboard cameras.