Chang Zheng-2F

Crew-rated two-stage liquid-propellant launch vehicle developed from the CZ-2E, capable of delivering 8,000 kg payload to 200 km LEO. Have been used for the launch of the Shenzhou vehicles, Tiangong 1, and Tiangong 2.

Name: Chang Zheng-2E/F (CZ-2E/F), or Long March 2E/F. Type: Liquid-propellant orbital launch vehicle. Contractor: China Academy of Launch Vehicle Technology (CALT, 1st Academy). First Launch: 1999-Nov-19. Launch site: JiuquanStatus: Operational.

CZ-2E

In October 1985, the Ministry of Astronautics formally announced its plan to provide commercial satellite services using Chinese launch vehicles for foreign customers. However, China’s existing CZ-3 launch vehicle could only loft 1,400 kg payload to GTO, far less than the typical mass of Western geostationary telecommunications satellites introduced at the time. In 1986, CALT proposed to modify the CZ-2C into CZ-2E, with the addition of four liquid-fuelled strap-on boosters to the rocket’s first-stage, which could give a LEO payload capacity of 9,000 kg, or a GTO payload capacity of 4,800 kg when coupled with an upper stage.

To increase the propellant capacity, the first-stage of the launch vehicle was stretched by 4.6 m, and the second-stage was stretched by 5.2 m. The satellite and the upper stage were housed inside an enlarged payload fairing that was 10.5 m in length and 4.2 m in diameter. As a result, the overall height of the launch vehicle stack was increased to 50 m.

Other improvements on the CZ-2E included:

– Improved rocket engines with increased thrust and Isp;
– A propellant management system on the rocket’s second-stage;
– Adding the second-stage with flight-control system and solid control rockets;
– Replacing the mesh-bar inter-stage section with a solid design featuring flame deflection windows;
– Digital flight-control system replacing the original analogue design;
– A new telemetry system with higher data transmission capacity;

In September 1987, China Great Wall Industry Corporation (CGWIC) representing the Chinese space industry was selected as the contractor for launching two Hughes telecommunications satellites for Australian telecommunications company Optus. At the time of the contract, all the Chinese contractor had was CALT’s concept proposal and feasibility studies. The CZ-2E did not exist yet, and CALT only had 18 months to develop the rocket and conduct a test launch. Engineering development of the CZ-2E began in October 1988, and the first launch took place on 16 July 1990 from the newly constructed Pad 2 in the Xichang Satellite Launch Centre, successfully placing a dummy communications satellite into its intended transfer orbit.

The first operational launch took place on 22 March 1992. However, the rocket carrying the US-made Australian telecommunications satellite Optus B1 failed to ignite. It took the ground crew 39 hours to secure the launch vehicle and remove the satellite. The same launch vehicle was put back on the launch pad five month later, and successfully placed Optus B1 into orbit on 14 August.

The second CZ-2E carrying Optus B2 was launched on 21 December 1992. However, the satellite exploded inside the payload fairing 45 seconds into the flight, though the launch vehicle continued flying and sent the debris of the satellite into the scheduled orbit. Later investigation suggested that the accident was caused by wind shear. The CZ-2E resumed flight on 28 August 1994, successfully sending the replacement satellite Optus B3 into orbit.

Disaster stroke again five months later on 26 January 1995, when a CZ-2E carrying the APStar 2 communications satellite, manufactured by Hughes (now Boeing Satellite), exploded approximately 50 seconds after lift-off. The failure was believed to have been caused by strong horizontal wind-shear once the launch vehicle had cleared the mountains surrounding the launch site. Chinese engineers believed that the wind-shear had caused a mechanical resonance that caused an explosion in the satellite’s apogee kick stage, while engineers in Hughes believed that the design fault in the rocket’s payload fairing caused it to collapse under the force of the wind-shear.

Exactly who should be responsible for the failure was inconclusive. Following the accident, some modifications were made to the CZ-2E’s fairing design. The next two flights of the CZ-2E were both successful. However, Chinese space planners too the decision to withdraw the launch vehicle from service.

CZ-2F

Despite its poor service records, the CZ-2E found a new life in China’s human spaceflight programme (Project 921) as the CZ-2F. To save the development cost and meet the tight timescale for developing and launching an unmanned Shenzhou test vehicle by 2000, the Chinese space industry proposed to develop the existing CZ-2E into a man-rated launch vehicle as opposite to developing a new design.

The CZ-2F inherited the airframe of the CZ-2E, but had its guidance, navigation & control system completely redesigned. To achieve improved system redundancy and safety, the CZ-2F was also added with two new systems: a launch escape system and a fault detection and diagnosis system. Furthermore, the structure of the first- and second-stage was also enhanced to support the extra weight of the Shenzhou vehicle and launch escape tower. The Shenzhou vehicle is housed inside an enlarged payload fairing, which is directly attached to the launch escape tower on top of the spacecraft.

The launch vehicle consisted of 9 systems: airframe, propulsion, guidance and flight control, propellant management, error detection and diagnosis, launch escape, telemetry, remote test, and auxiliary system. The various modifications resulted in an increase of the launch vehicle’s overall height from 49.69 m to 58.34 m, and its launch weight from 462.5 t to 479.8 t. Launched from the Jiuquan Satellite Launch Centre, the launch vehicle was capable of placing the 8,000 kg Shenzhou vehicle into a 200 x 350 km parking orbit. Between 1999 and 2008, the CZ-2F made 7 flights, placing 7 Shenzhou crew vehicles into orbit.

In 2011, CLAT introduced an improved variant of the CZ-2F, which featured 170 items of improvements in its design and had its payload capacity increased to 8,100 kg for crewed missions and 8,600 kg for unmanned missions. This variant was first used to launch the Tiangong 1 space launch vehicle on 29 September 2011, and all subsequent Shenzhou flight missions. The launch vehicle is expected to remain operational beyond 2020.

Specifications
Stages:...................2
Strap-on boosters:........4
Overall length (m):.......31.17 (CZ-2C) 58.34 (CZ-2F)
Take-off mass (t):........192 (CZ-2C), 479.8 (CZ-2F)
Take-off thrust (kN):.....5,923.2 (CZ-2F)
Thrust-weight ratio:......
LEO capacity (kg):........8,000-8,600 (CZ-2F)
GTO capacity (kg):........4,800 (CZ-2E)

Stages                    1st-stage      2nd-stage      Booster
-----------------------------------------------------------------
Length (m):...............28.5           15.1           15.326
Diameter (m):.............3.35           3.35           2.25
Gross mass (t):...........199            91.4           40.75
Empty mass (t):...........12.55          5.0            3.0
Propellant mass (t):......169            84.76          37.75
Engine, main:.............YF-21B         YF-22B         YF-20B
Engine, vernier:..........No             4x YF-23B      No
Propellant:...............N2O4/UDMH      N2O4/UDMH      N2O4/UDMH
Thrust, main (kN):........2,962          738.4          740.4
Thrust, vernier (kN):.....               4x 47.07
Isp, main (N.s/kg ):......2,556.2        2,922.4        2556.2
Isp, vernier (N.s/kg):....               2,762
Burn time, main (sec):....160.43         301.18         127.26
Burn time, vernier (sec):.               414.68

Payload fairing           CZ-2E
-----------------------------------------------------
Length (m):...............10.5
Diameter (m):.............4.20
Weight (kg):..............1,900 kg
Gallery
References
  • 李成智 [Li Cheng-zhi], 2003. 中国航天技术发展史稿(中)[“A Draft History of Space Technology in China (Part 2 of 3)”]. 山东教育出版社 [Shandong Education Press].
  • 邸乃庸, 朱维增, 吴瑞华 [Di Naiyong, Zhu Weizeng, Wu Ruihua], 1997. 长征系列运载火箭介绍:长征二号系列 [“Introduction to the Long March 2 Series Launch Vehicles”]. 中国航天, 1997年第9/10/11/12期 [China Spaceflight, 1997 Issue 9/10/11/12]

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