US Army flies a 3D printed heavy-fuel engine in a hybrid drone

The US Army Combat Capabilities Development Command Army Research Laboratory (DEVCOM ARL) has flown a heavy-fuel rotary engine, developed with metal 3D printing, in a hybrid unmanned aircraft. The Army describes it as the first 3D printed heavy-fuel engine.

The air-cooled engine needs no liquid coolant and works in a series-hybrid configuration with a new 400-volt motor-generator. It was a clean-sheet design guided by computational fluid dynamics (CFD) modelling, aimed at better fuel atomisation and vaporisation and less leakage of compressed air and fuel vapour. The flight demonstration took place on VICTOR, a mid-sized (Group 3) unmanned aircraft built with Griffon Aerospace.

According to programme manager Chol-Bum “Mike” Kweon, metal 3D printing let the team redesign engine components quickly based on test results, producing a smaller engine that needs no liquid cooling. The report does not say which parts were printed or in which material. Lessons from the programme will feed into PULSAR, a concept for using VICTOR drones in swarms.

Source: VoxelMatters – Army Research Lab flies 3D printed heavy-fuel rotary engine in a hybrid drone (2 November 2026)