Researchers at the U.S. Army Combat Capabilities Development Command Army Research Laboratory (DEVCOM ARL) have successfully flown VICTOR, a hybrid-electric vertical take-off and landing drone powered by a heavy-fuel rotary engine. Metal 3D printing helped the team rapidly redesign engine components during development.
The engine uses JP-8, a kerosene-based military fuel that is denser than regular jet fuel. That property can help reduce the amount of fuel carried or increase range, while supporting the military’s aim of using one fuel across more of its equipment. But JP-8 is less volatile and harder to atomize, and its higher flash point makes ignition more challenging than with gasoline.
The ARL team used computational fluid dynamics and a clean-sheet design to improve the engine. Dr. Kweon, one of the researchers, told Army.mil that metal 3D printing enabled the team to quickly revise components based on testing. The iterations improved fuel atomization and reduced compression leaks, while making an air-cooled engine possible. That design removes the need for a bulky liquid-cooling system and reduces the propulsion system’s size.
Rather than mechanically driving the propellers, the rotary engine turns a 400-volt motor-generator, which supplies electricity to the propeller motors. This lets the engine run at its preferred speed independently of the propellers. The military has not disclosed details of VICTOR’s battery configuration.
VICTOR can take off and land without a runway, including on terrain unsuitable for conventional two-winged aircraft that cannot perform vertical take-offs and landings. The Army has shared video of the drone’s first flight. The source reports that a battery system could allow it to travel significant distances on one fuel-up, while air cooling avoids maintenance associated with a liquid-cooling system.
Sources: Tom's Hardware.