The YF-20 is a Chinese liquid-fuel

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 accorda ...

burning N₂O₄ and

UDMH Unsymmetrical dimethylhydrazine (UDMH; 1,1-dimethylhydrazine, НДМГ or codenamed Geptil) is a chemical compound with the formula H2NN(CH3)2 that is used as a rocket propellant. It is a colorless liquid, with a sharp, fishy, ammonia-like smell ...

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 a basic engine which when mounted in a four engine module forms the YF-21. The high altitude variation is known as the YF-22 is normally paired with the YF-23 vernier to form the YF-24 propulsion module for second stages. New versions when used individually for booster applications are called YF-25.

Versions

The basic engine has been used since the

Feng Bao 1 The Feng Bao 1 (), also known as FB-1, was a Chinese carrier rocket launched between 1972 and 1981. It was replaced by the nearly identical Long March 2, which had been developed at the same time for political reasons related to China's Cultur ...

rocket and has been the main propulsion of the

Long March 2 Long March 2 rocket family or Chang Zheng 2 rocket family as in Chinese pinyin is an expendable launch system operated by the People's Republic of China. The rockets use the abbreviations LM-2 family for export, and CZ-2 family within Chi ...

Long March 3 The Long March 3 (), also known as the Changzheng 3, CZ-3 and LM-3, was a Chinese orbital carrier rocket design. They were all launched from Launch Area 3 at the Xichang Satellite Launch Center. It was a three-stage rocket, and was mostly used ...

and

Long March 4 The Long March rockets are a family of expendable launch system rockets operated by the China Aerospace Science and Technology Corporation. The rockets are named after the Chinese Red Army's 1934–35 Long March military retreat during the Ch ...

families. * YF-20: Core engine. Flown originally on the

and

Long March 2A The Long March 2A, also known as the Chang Zheng 2A, CZ-2A and LM-2A, was a Chinese orbital carrier rocket which launched FSW-0 reconnaissance satellites. It was later replaced by the more capable Long March 4C. It was developed by the China Acad ...

. * YF-20A: Core engine. * YF-20B (a.k.a. DaFY5-1): Core engine, also used on the boosters. * YF-20C: Core engine, also used on the boosters. * YF-20D: Core engine, also used on the boosters. * YF-20E: Core engine, also used on the boosters. * YF-22: Upper stage version with enlarged nozzle are ratio. Flown originally on the

second stage with no verniers, and on the

with the YF-23 verniers as the YF-24. * YF-22A: Upper stage version. * YF-22B (a.k.a. DaFY20-1): Upper stage version. * YF-22C: Upper stage version. * YF-22D: Upper stage version. * YF-22E: Upper stage version. * YF-25: Booster stage version.

Modules

While the basic engine was used multiple times, it was only used as a single engine for booster application. It is usually bundled into modules of multiple engines. The relevant modules for first stage application are: * YF-21: A module comprising four YF-20. Flown originally on the

and

. * YF-21A: A module comprising four YF-20A. Improved version. * YF-21B (a.k.a. DaFY6-2): A module comprising four YF-20B. Improved version which increased thrust by 7%. * YF-21C: A module comprising four YF-20C. Improved version. * YF-21D: A module comprising four YF-20D. Improved version. * YF-21E: A module comprising four YF-20E. Improved version. The relevant modules for second stage application are: * YF-24: A module comprising an YF-22 and a YF-23 vernier. First flown on the

. * YF-24A: A module comprising an YF-22A and a YF-23A verniers. * YF-24B: A module comprising an YF-22B and a YF-23B verniers. * YF-24C: A module comprising an YF-22C and a YF-23C verniers. * YF-24D: A module comprising an YF-22D and a YF-23D verniers. * YF-24E: A module comprising an YF-22E and a YF-23E verniers.

References

{{DEFAULTSORT:YF-20 Rocket engines of China Rocket engines using hypergolic propellant Rocket engines using the gas-generator cycle