YF-20

A YF-20K engine
Country of origin	China
First flight	1995-06-01
Designer	Academy of Aerospace Liquid Propulsion Technology
AssociatedLV	Feng Bao 1,Long March 2,Long March 3 andLong March 4
Status	In Production
Liquid-fuel engine
Propellant	N2O4 /UDMH
Cycle	Gas Generator
Configuration
Chamber	1
Nozzle ratio	12.69
Performance
Thrust, vacuum	816.3 kN (183,500 lbf)
Thrust, sea-level	731.5 kN (164,400 lbf)
Chamberpressure	7.1 MPa (1,030 psi)
Specific impulse, vacuum	289 seconds (2.83 km/s)
Specific impulse, sea-level	259 seconds (2.54 km/s)
Burn time	160s
Gimbal range	±10° (when integrated on the YF-21B)
Dimensions
Diameter	84 centimetres (33 in)
Dry mass	712.5 kg (1,571 lb)
Used in
Feng Bao 1 first stage andLong March 2C,Long March 2D,Long March 2E,Long March 3,Long March 3A,Long March 3B andLong March 4A, boosters, first stage and second stage.
References
References	[1][2][3][4]

TheYF-20 is aChineseliquid-fuelrocket engine burningN₂O₄ andUDMH in agas generator cycle. It is a basic engine which when mounted in a four engine module forms theYF-21. The high altitude variation is known as theYF-22 is normally paired with theYF-23vernier to form theYF-24 propulsion module for second stages. New versions when used individually for booster applications are calledYF-25.^[5][6]

The basic engine has been used since theFeng Bao 1 rocket and has been the main propulsion of theLong March 2,Long March 3 andLong March 4 families.^[6][7][8]

• YF-20: Core engine. Flown originally on theFeng Bao 1 andLong March 2A.^[8][9][10]
• YF-20A: Core engine.^[11]
• YF-20B (a.k.a.DaFY5-1): Core engine, also used on the boosters.^[2][12][13]
• 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 theFeng Bao 1 second stage with no verniers, and on theLong March 2A with the YF-23 verniers as theYF-24.^[8][10]
• YF-22A: Upper stage version.
• YF-22B (a.k.a.DaFY20-1): Upper stage version.^[12][13]
• YF-22C: Upper stage version.
• YF-22D: Upper stage version.
• YF-22E: Upper stage version.
• YF-25: Booster stage version.

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.^[10][14][15]

The relevant modules for first stage application are:

• YF-21: A module comprising four YF-20. Flown originally on theFeng Bao 1 andLong March 2A.^[8][10]
• 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%.^[12]
• YF-21C: A module comprising four YF-20C. Improved version.^[16]
• 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 aYF-23 vernier. First flown on theLong March 2A.^[10]
• 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.^[16]

• Rocket engines of China
• Rocket engines using hypergolic propellant
• Rocket engines using the gas-generator cycle

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