The Changzheng 4A (CZ-4A, or “Long March 4A”) was the three-stage version of the CZ-2, added with a liquid motor third-stage. The rocket was originally developed as a backup to the CZ-3 for the launch of the geostationary communications satellite, but was later adopted for launching Earth observation remote-sensing satellites into high-inclination polar orbit. The rocket has now been replaced by the improved CZ-4B and CZ-4C.
When the geostationary communication satellite (Project 331) was launched in the early 1970s, the Ministry of Aeronautics proposed two designs for the launch vehicle. The first proposal was to add the two-stage CZ-2 with a third-stage burning the same N2O4/UDMH liquid propellant used by the first- and second-stage of the rocket. The second proposal used a more advanced third-stage burning the low temperature LOX/LH2 propellant.
The two rockets were being developed by the Shanghai Space Bureau (now SAST) and the Beijing-based First Academy (now CLAT) respectively. Although the ministry was in favour of the more advanced LOX/LH2 design, the other rocket was also kept as a backup, in case the other development failed. The two development programmes were run in parallel until 1984, when the development of the CZ-3 featuring the LOX/LH2 third-stage was finally completed.
Following the success of the CZ-3, the CZ-4 programme was stopped. However, the design of the rocket was not abandoned. Instead, it was used to develop a new rocket CZ-4A, intended to launch China’s first polar orbit meteorology satellite Fengyun 1A (Project 771). The development of the CZ-4A began in 1985 and the rocket made its first launch successfully on 7 September 1988.
Two years later, on 3 September 1990, the CZ-4A made its second flight, putting the Fengyun 1B satellite and two Daqi 1 balloon satellites into their intended orbits. The was also the last flight of the CZ-4A.
The CZ-4A was similar to the CZ-2 in design. By stretching the rocket’s first-stage by 4 metres, it could carry an additional 40 tonnes of propellant. The first-stage also featured an improved YF-21B liquid motor engine, which gave a maximum thrust of 2,942kN.
The newly-developed third-stage was powered by an YF-40 liquid motor engine, which consisted of two fully swivelling chamber motors and carried a total of 11.3 tonnes N2O4/UDMH liquid propellant. Other improvements included a computerised guidance system, and an onboard propellant management system.
|Overall length||41.9 m|
|Core stage diameter||3.35 m|
|Take-off mass||249 t|
|Take-off thrust||2,942 kN|
|Payload capacity||1,250 kg (30.5° GTO)
4,590 kg (200 km, 70° LEO)
4,150 kg (200 km, 90° LEO)
2,200 kg (750km LEO)
2,100 kg (750 km, 99° SSO)
1,650 kg (900km LEO)
|Length||24.65 m||10.40 m||4.954 m|
|Diameter||3.35 m||3.35 m||2.9 m|
|Gross mass||187.26 t||38.58 t||13.14 t|
|Empty mass||9.83 t||3.08 t||1.8 t|
|Propellant mass||177.43 t||35.5 t||11.34 t|
(Swivelling) 4 X YF-23F
|Thrust*||2,942 kN|| (Main) 719.8 kN
(Swivelling) 4X 46.1 kN
|Isp*||2,550 N.s/kg||(Main) 2,835 N.s/kg
(Swivelling) 2,742 N.s/kg
|Burn time||150.6 s||(Main) 126.8 s
(Swivelling) 136.8 s
* Sea-level values for the first-stage, and vacuum values for the second- and third-stage
- The CZ-2A and 2B designations had already been given to the two three-stage versions of the CZ-2 for the launch of the geostationary communications satellite. They were later re-designated CZ-4 and CZ-3 respectively.
Last updated: 23 February 2012