The YF-75 is a

liquid Liquid is a state of matter with a definite volume but no fixed shape. Liquids adapt to the shape of their container and are nearly incompressible, maintaining their volume even under pressure. The density of a liquid is usually close to th ...

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 ...

rocket engine A rocket engine is a reaction engine, producing thrust in accordance with Newton's third law by ejecting reaction mass rearward, usually a high-speed Jet (fluid), jet of high-temperature gas produced by the combustion of rocket propellants stor ...

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

gas generator A gas generator is a device for generating gas. A gas generator may create gas by a chemical reaction or from a solid or liquid source, when storing a pressurized gas is undesirable or impractical. The term often refers to a device that uses a ...

cycle. It is China's second generation of

propellant engine, after the YF-73, which it replaced. It is used in a dual engine mount in the H-18 third stage of the

Long March 3A The Long March 3A (), also known as the Chang Zheng 3A, CZ-3A and LM-3A, is a Chinese orbital carrier rocket design. It is a 3-stage rocket, and is usually used to place communications satellites and Beidou navigation satellites into geosynch ...

Long March 3B The Long March 3B (), also known as the CZ-3B and LM-3B, is a Chinese orbital launch vehicle. Introduced in 1996, it is launched from Launch Area 2 and 3 at the Xichang Satellite Launch Center in Sichuan. A three-stage rocket with four strap-on ...

and

Long March 3C The Long March 3C (), also known as the Changzheng 3C, CZ-3C and LM-3C, is a Chinese orbital launch vehicle. It is launched from Launch Complex 2 and 3 at the Xichang Satellite Launch Center (XSLC). A three-stage rocket with two strapon liquid ...

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. The engine also heats hydrogen and helium to pressurize the stage tanks and can control the mixture ratio to optimize propellant consumption.

Development

Given the upward trend on geosynchronous communication satellite's mass and size, a program to develop an engine more powerful than the YF-73 was started by 1982. The proper development of the engine started in 1986 and leveraged the experience of the YF-73. It flew for the first time in 1994. By September 2013, it had accumulated 12 start up and 3,000 seconds of firing time without malfunction. By 2006 and with the project for 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 ...

family a serious redesign program was started. The resulting engine, the YF-75D is a different engine, using a closed circuit expander cycle like the

RL10 The RL10 is a liquid-fuel cryogenic rocket engine built in the United States by Aerojet Rocketdyne that burns cryogenic liquid hydrogen and liquid oxygen propellants. Modern versions produce up to of thrust per engine in vacuum. RL10 version ...

Technical Description

The combustion chamber regeneratively cooled and is made of a zirconium copper alloy. It is manufactured by forging, rolled into shape, and then the cooling channels are milled. The outer wall is electroformed nickel. The nozzle extension uses dump cooling. It is made by welding spiraling tubes which pass cryogenic hydrogen that is dumped since the tubes are open at the bottom. The gas generator feed separate turbopumps for fuel and oxidizer. The single shaft hydrogen turbopump operates at 42,000

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 ...

and uses dual elastic supports to enhance the rotor stability and reliability. The gas generator also incorporates dual heat exchanger that heat hydrogen gas and helium supplied from separate system to pressurize the hydrogen and oxygen tanks. The turbopumps use solid propellant cartridge for start up, while the gas generator and combustion chamber use pyrotechnic igniter. It can restart for two burn profile missions. All subsystems are attached to the combustion chamber and gimbal is achieved by rotating the whole engine on two orthogonal planes with two independent actuators. These actuators use high pressure hydrogen as

hydraulic fluid A hydraulic fluid or hydraulic liquid is the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water. Examples of equipment that might use hydraulic fluids are excavators and backho ...

. The oxygen supply system has a propellant utilization valve before the main LOX valve to regulate its flow and thus variate the mixture ratio. This enables optimization of the propellant reserves and improves performance.

References

External links

Encyclopedia Astronautica

Long March 3B Profile
{{DEFAULTSORT:YF-75 Rocket engines using hydrogen propellant Rocket engines of China Rocket engines using the gas-generator cycle