The YF-100 is[when?] a Chinese governmentLOX & kerosene rocket engine. Development began in the 2000s, with testing directed by the China National Space Administration (CNSA) commencing in 2005. The predecessor was Russian RD-120 acquired in the 90's. Development works are mainly carried out by the Xi'an Aerospace Propulsion Institute. The engine had been successfully tested by mid-2007. It adopts a staged-combustion cycle, which use oxidizer-rich preburner to produce hot gas to drive the turbine. It will be used as booster engines for China's next generation of launch vehicles, namely the Long March 5 series. It is China's first rocket engine to adopt the staged-combustion cycle.