YF-79

The YF-79 is a liquid cryogenic rocket 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]

YF-79

Country of origin	China
Designer	Beijing Aerospace Propulsion Institute
Associated LV	Long March 9
Predecessor	YF-75D
Status	In development
Liquid-fuel engine
Propellant	Liquid oxygen / Liquid hydrogen
Mixture ratio	6.0
Cycle	Closed Expander Cycle
Configuration
Chamber	1
Nozzle ratio	160
Performance
Thrust, vacuum	250 kilonewtons (56,000 lbf)
Chamber pressure	7.0 MPa (1,020 psi)
Specific impulse, vacuum	455.2 seconds (4.464 km/s)
Used in
Long March 9
References
References	[1][2][3][4]

It will be used on the third stage of the Long March 9.