YF-77

The YF-77 is China's first cryogenic rocket engine developed for booster applications. It burns liquid hydrogen fuel and liquid oxygen oxidizer in the gas generator cycle. A pair of these engines will power the LM-5 core stage in a module that includes the mount that enables each individual engine to gimbal in two planes. While it will be lighten at lift of, its function will be that of a sustainer engine, like the European Vulcain on the Ariane 5 and the Japanese LE-7 on the H-II, since the core stage thrust will be supplemented by the YF-100 powered boosters. Like the Vulcain, it uses the less efficient gas generator cycle and even for that application it has less performance than the European engine. It does advances significantly the thrust level of cryogenic rocket technology in China.

Development

In January 2002, the development of a new cryogenic engines was approved by the Commission for Science, Technology and Industry for National Defense. The development responsibility was assigned to the Beijing Aerospace Propulsion Institute, a division of the Academy of Aerospace Launch Propulsion Technology. The preliminary design was accomplished by middle 2002 and the first set of components was manufactured by early 2003. The same year saw the initial component and subsystem tests, with the gas generator successfully performing its first test on July 30. By December 2003 the whole powerpack successfully passed its first integrated test, and on September 17, 2004 a successful 50 seconds firing of a whole prototype engine was achieved.