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]
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]
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:
