CASC flight-validates multi-restart YF-75DB hydrogen engine

(SpaceEnergy) China Aerospace Science and Technology Corporation has disclosed flight validation of its YF-75DB hydrogen-oxygen upper-stage engine, including multiple restart capability and hour-scale coast performance.

The engine, developed by CASC Sixth Academy’s Beijing Institute 11, uses low-pressure torch ignition instead of conventional pyrotechnic ignition. Propellant drawn from the engine’s hydrogen and oxygen pump cavities feeds the torch, removing the need for expendable igniters and additional high-pressure ignition hardware.

CASC said the architecture can in principle support near-unlimited restart cycles and provides at least three reliable high-altitude ignitions. A third burn can be reserved for rapid upper-stage disposal after payload deployment.

Ground testing demonstrated coast periods of up to three hours. On its first flight, the engine completed an initial 1,000-second coast followed by a further coast of about one hour, according to CASC.

The 10-tonne-thrust engine was developed in 16 months and is 40kg lighter than its predecessor configuration following simplification of its gas-supply and telemetry systems. It is now standard equipment on the Long March 8A.

CASC said future development targets include six-hour coast capability for medium-Earth, geosynchronous and deep-space missions, while longer-term concepts include orbital refuelling and upper-stage reuse.