Unfortunately, the hydrogen typically has to be stored in large heavy pressurized tanks. Last month, however, a Raptor E1 electric drone made a successful test flight running on a unique new system that's actually lighter than the lithium-ion battery it replaced.

The flight was carried out on Jan. 19th at Scotland's Oban Airport, by a team from the Scottish Association for Marine Science (SAMS). Although the flight only lasted 10 minutes with the drone cruising at an altitude of 80 m (262 ft), the fuel cell reportedly had enough fuel to fly for two hours.

That fuel took the form of approximately 100 small solid pellets contained within an unpressurized cartridge. Made by Britain's Cella Energy, those pellets are composed of a proprietary chemical compound, and they steadily produce hydrogen gas when a small amount of heat is applied. The Arcola Energy-manufactured fuel cell converts that gas into electricity, which was used to power the drone's motor.