The YF-79 is a liquidcryogenicrocket engine burning liquid hydrogen and liquid oxygen in a closed expander cycle. It is China's fourth generation of upper stage cryogenic propellant engine, after the YF-73, YF-75 and the YF-75D. It can do multiple restarts thanks to an electric spark igniter and a prototype was tested at 60% and 100% (25 tonnes-force (250 kN; 25 LTf; 28 STf)) thrust levels in December 2021.[1]
It will be used on the third stage of the Long March 9.
References
^ abXin, Zhang. "我国重型运载火箭25吨级膨胀循环氢氧发动机首台推力室挤压试验取得圆满成功" [First thrust chamber test firing of China's heavy launch vehicle 25-tonne hydrogen-oxygen expansion cycle engine a complete success] (in Chinese). Archived from the original on 2021-12-22. Retrieved 2021-12-22.