The YF-75D is a

cryogenic rocket engine A cryogenic rocket engine is a rocket engine that uses a cryogenic fuel and oxidizer; that is, both its fuel and oxidizer are gases which have been liquefied and are stored at very low temperatures. These highly efficient engines were first fl ...

burning

liquid hydrogen Liquid hydrogen () is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecule, molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point (thermodynamics), critical point of 33 Kelvins, ...

and

liquid oxygen Liquid oxygen, sometimes abbreviated as LOX or LOXygen, is a clear cyan liquid form of dioxygen . It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an application which is ongoing. Physical ...

in a closed expander cycle. It is China's third generation of upper stage

cryogenic In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th International Institute of Refrigeration's (IIR) International Congress of Refrigeration (held in Washington, DC in 1971) endorsed a univers ...

propellant engine, after the YF-73 and the

YF-75 The YF-75 is a liquid cryogenic rocket engine burning liquid hydrogen and liquid oxygen in a gas generator cycle. It is China's second generation of cryogenic propellant engine, after the YF-73, which it replaced. It is used in a dual engine mou ...

. It is used in a dual engine mount in the H5-2 second stage of the

Long March 5 Long March 5 (LM-5; zh, s=长征五号 , p=Chángzhēng wǔ hào) or Changzheng 5 (CZ-5), also known by its nickname "''Pang-Wu''" (胖五, "''Fat-Five''"), is a Chinese heavy-lift launch vehicle developed by the China Academy of Launch Vehicl ...

launch vehicles. Within the mount, each engine can

gimbal A gimbal is a pivoted support that permits rotation of an object about an axis. A set of three gimbals, one mounted on the other with orthogonal pivot axes, may be used to allow an object mounted on the innermost gimbal to remain independent of ...

individually to enable

thrust vectoring Thrust vectoring, also known as thrust vector control (TVC), is the ability of an aircraft, rocket or other vehicle to manipulate the direction of the thrust from its engine(s) or motor(s) to Aircraft flight control system, control the Spacecra ...

control. As with its predecessor YF-75, the YF-75D can adjust its mixture ratio to optimize propellant consumption. As an additional improvement it can do multiple restarts, against the single one of its predecessor. The combustion chamber required a redesign to keep the power balance. Since the expander cycle uses the heat extracted from the cooling circuits to drive the turbines, the chamber had to be lengthened and the cooling passages redesigned. The engine uses a redesigned hydrogen turbine. It uses an axial two-staged low pressure ratio subsonic turbine that operates at 65,000

rpm Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or r⋅min−1) is a unit of rotational speed (or rotational frequency) for rotating machines. One revolution per minute is equivalent to hertz. Standards ISO 80000-3:2019 def ...

, which is between the second and third

critical speed In solid mechanics, in the field of rotordynamics, the critical speed is the theoretical angular velocity that excites the natural frequency of a rotating object, such as a shaft, propeller, leadscrew, or gear. As the speed of rotation approaches ...

. It rests on dual elastic support dampers around the ceramic ball bearings.

YF-75E

The YF-75E engine is based on the YF-75D engine, and the nozzle ratio is increased to improve its working performance. It is expected to be used in the third stage of the

Long March 10 Long March 10 (), also known as the “''Next Generation crewed launch vehicle''” (), and previously and unofficially as the “''921 rocket''” () or the "''Long March 5G''" (a development of the Long March 5), is a Chinese Super heavy-lift l ...

launch vehicle.

Specifications

References

External links

Engine Manufacturer
Rocket engines using hydrogen propellant Rocket engines of China Rocket engines using the expander cycle {{rocket-stub