The YF-75 is a

liquid A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, a ...

cryogenic In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cr ...

rocket engine A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordanc ...

burning

liquid hydrogen Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point of 33 K. However, for it to be in a fully li ...

and

liquid oxygen Liquid oxygen—abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries—is the liquid form of molecular oxygen. It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an applica ...

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 The YF-73 was China's first successful cryogenic liquid hydrogen fuel and liquid oxygen oxidizer gimballed engine. It was used on the Long March 3 H8 third stage, running on the simple gas generator A gas generator is a device for generating ...

, 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 geosynchron ...

Long March 3B The Long March 3B (, ''Chang Zheng 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 rocke ...

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 control the attitude or angular velocity of the v ...

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), and also by its nickname "''Pang-Wu''" (胖五, "''Fat-Five''"), is a Chinese heavy-lift launch vehicle developed by the China Academy of Launch Vehicle ...

family a serious redesign program was started. The resulting engine, the

YF-75D The YF-75D is a liquid-fuel rocket, liquid cryogenic rocket engine, cryogenic rocket engine burning liquid hydrogen and liquid oxygen in a closed Expander cycle (rocket), expander cycle. It is China's third generation of upper stage cryogenic fue ...

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. Three RL10 ve ...

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 with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines. Standards ISO 80000-3:2019 defines a unit of rotation as the dimensionl ...

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 In pyrotechnics, a pyrotechnic initiator (also initiator or igniter) is a device containing a pyrotechnic composition used primarily to ignite other, more difficult-to-ignite materials, such as thermites, gas generators, and solid-fuel rockets. The ...

. 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 backhoe ...

. 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