[1][4] Although the YF-77 is ignited prior to liftoff, the LM-5's four strap-on boosters provide most of the initial thrust in an arrangement similar to the European Vulcain on the Ariane 5 or the Japanese LE-7 on the H-II.

In January 2002, the development of a new cryogenic engines was approved by the Commission for Science, Technology and Industry for National Defense.

The concept review confirmed that the performance goal and launcher requirements were met, and the engine was ready for integration for the first launch of the Long March 5 rocket.

[1] Engine development began in the 2000s, with testing directed by the China National Space Administration (CNSA) commencing in 2005.

The engine also has dual heat exchanger to supply hot gaseous hydrogen and oxygen for tank pressurization.

[1] 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.