Long March 5

China initiated the CZ-5 programme in 2007, after two decades of feasibility studies, in anticipation of its need for greater low Earth and geostationary transfer orbit payload capacity over the following 20 to 30 years. The rocket was to be manufactured in Tianjin, a coastal city near Beijing, and launched from the new Wenchang Space Launch Site on the southern island of Hainan. Engine work had started earlier: testing directed by CNSA began in 2005, and by mid-2007 both the YF-100 and the YF-77 had been successfully fired. In July 2012 a 1200 kN LOX/kerosene booster engine was test-fired. The first photographs of a CZ-5 under test appeared in March 2015, and the first production vehicle shipped from Tianjin to Hainan on 20 September 2015 for launch rehearsals.

The maiden flight, originally planned for 2014, finally took place on 3 November 2016. The countdown was interrupted three times by flight control computer and tracking software problems, and lift-off slipped by nearly three hours. The second launch, on 2 July 2017, suffered an anomaly shortly after lift-off and was declared a failure 45 minutes into flight; investigators traced the cause to the oxidiser turbopump of one of the core stage's YF-77 engines. A 28-month hiatus followed until the Y3 mission of 27 December 2019 placed the Shijian-20 communications satellite into geostationary transfer orbit, marking the programme's return to flight.

The programme's fourth flight debuted the CZ-5B variant, which keeps the core stage and its four strap-on boosters but deletes the second stage. It flew on 5 May 2020 carrying an uncrewed prototype of China's future deep-space crewed spacecraft. The variant then became the workhorse of Tiangong assembly, beginning with the Tianhe core module. Its core stages, which reached orbit, produced widely reported uncontrolled re-entries in 2020 and 2021.