Rotary engines help aircraft reach supersonic speeds

A drone equipped with an engine that uses explosive force to propel the aircraft many times faster than sound made its first successful flight at an airport in Gansu province.

The FB-1 rotary explosion engine (FB-1 RDE) was developed by the Chongqing University Institute of Technology in collaboration with Shenzhen-based Thrust-to-Weight Ratio Engine (TWR). The engine was activated and tested during the taxiing phase of the drone on a runway of about 5 meters long, but it is unclear whether the engine will continue to operate during flight, the South China Morning Post reported on September 25.

Drone equipped with rotating engine before its first flight. (Photo: Bilibili).

The engine firing test was also the first flight of a university-built drone with TWR's participation. A series of ground tests had previously been conducted with the RDE engine before it was placed on the drone for its first flight. The engine, which uses kerosene fuel and rapid ignition technology , can provide the power to accelerate the aircraft from zero to several times the speed of sound.

Conventional turbofan engines use propellers to suck in air, creating high drag at speeds above Mach 3 (2,302 km/h). Ramjets can help aircraft overcome this limitation by compressing the intake air in their shape, but they cannot provide better combustion efficiency. RDE could be the optimal solution. The new engine has an annular combustion chamber, where controlled explosions generate shock waves that lead to complete combustion of fuel and air.

The explosion is much more efficient than turbojets and ramjets, giving RDE the potential to revolutionize supersonic flight while consuming less fuel. Unlike scramjets, which typically require speeds above Mach 4 (4,939 km/h) to start, RDEs can start from zero and are easier to maintain. However, the technology comes with challenges. The engine's inner walls must withstand the impact of frequent shock waves, requiring high standards of structural integrity and material strength.

A successful test could have far-reaching implications for applications ranging from commercial space rockets and high-speed drones to military aircraft and guided missiles. According to TWR, their RDE engine achieves 1,000 Newtons of thrust and is expected to launch products within the next two years.