ChangZheng 3 (Long March 3) Launch Vehicle

The ChangZheng 3 (or Long March 3 in its English translation) is a family of space launch vehicles (SLV) developed by the Beijing-based China Academy of Launch Vehicle Technology (CALT), a subsidiary of the China Aerospace Science & Technology Corporation (CASC). The Shanghai Academy of Space Flight Technology (SAST) was also involved in the development programme.

The launcher was designed specifically for Geostationary Earth Orbit (GEO) launches. The launch vehicle is available in four variants: the basic variant CZ-3 (retired), CZ-3A, CZ-3B and CZ-3C.

Design

The ChangZheng 3 launch vehicle was based on the core stage of the ChangZheng 2C, but added with a third-stage. The first and second stage of the launcher burn the UDMH/N2O4 (nitrogen tetroxide) storable liquid propellant. The third stage uses the liquid oxygen/liquid hydrogen (LOX/LH2) propellant. Later variants were added with two or four boosters that also burn the UDMH/N2O4 liquid propellant.

The first stage of the launch vehicle is powered by a YF6-2 rocket engine consisting of four YF-20 chambers motors with swinging nozzles, each producing 75,500kg thrust. The second stage of the core vehicle has a rocket engine consisting of one 75,600kg (742kN)-thrust YF20-1 main motor with fixed nozzles and a YF21-1 swivelling venire motor with four chambers motors (4,800kg/47kN-thrust in total). There are four stabilising fins located at the lower end of the first stage on CZ-3 and CZ-3A.

The third stage employs a YF-75 engine that produces 16,000kg (157kN) thrust. The restarting ability the of third-stage engine allows heavier payload to be delivered to the GTO. The payload fairing is 8.887m in length and 3.35m in diameter. The nose cone of the fairing is made of glass fibre materials and the rest part made of alloy materials. There are windows on the fairing for pre-launch examination and receiving radio signals. The vehicle can carry two satellites in a single launch.

ChangZheng 3 (Chinese Internet)

ChangZheng 3

In 1978, CALT was assigned to develop a new launch vehicle to launch China’s first communications satellite DongFangHong 2. CALT was in charge of the overall design of the launch vehicle as well as the third-stage of the launcher, while SAST was responsible for the development of the first and second stage of the launcher. The ChangZheng 3 can deliver 1,400kg payload to the geostationary transfer orbit (GTO), where the satellite then uses its own apogee kick stage to manoeuvre to its intended position on GEO. A new satellite launch centre was also being built at Xichang, Sichuan Province dedicated for GEO launches.

The first launch of the ChangZheng 3 took place on 29 January 1984, but the third-stage of the launcher failed to restart to move from the parking orbit to the GTO. As a result, the PRC’s first DFH-2 experimental communications satellite carried onboard was placed into an elliptical orbit, making the satellite unusable. Despite the failure, most tests on the satellite and the launch vehicle were carried out as planned. A careful analysis of the failure was made using the telemetry data and the cause of the malfunction was identified as an abnormal mixture ratio in the gas generator for the third-stage.

After some modifications on the third-stage, the ChangZheng 3 resumed its launch three months later and carried out six successful launches consecutively between April 1984 and April 1990, including PRC’s first commercial launch of a foreign communications satellite (AsiaSat 1).

On 28 December 1991, a ChangZheng 3 launcher carrying the domestic ChinaSat 4 (ZhongXing 4) communications satellite failed, again due to third-stage malfunction, leaving the payload with an apogee of only 2,450km instead of nearly 36,000km as required.

The ChangZheng 3 returned to service in July 1994, carrying out another five GEO missions successfully between 21 July 1994 and 25 June 2000, before it was finally retired and replaced by the improved CZ-3A.

ChangZheng 3A

ChangZheng 3A (Chinese Internet)

The ChangZheng 3A is an improved variant of the ChangZheng 3. The diameter of the third stage has been increased from 2.25m to 3m, and the propellant capacity has been increased from 8,200kg to 17,600~18,200kg, resulting in an increase in the launcher’s GTO payload capability from 1,400kg to 2,600kg. An improved control system also allows greater flexibility for altitude control and better adaptability to a variety of launch missions.

Development of the CZ-3A was carried out between 1986 and 1994. The first launch took place on 8 February 1994 at the Xichang Satellite Launch Centre (XSLC), successfully sending a LEO satellite and a GEO satellite into the orbits. On 30 November 1994, a second CZ-3A successfully placed the first DongFangHong 3 communications satellite into the GTO, but the satellite could not reach its intended orbit because its apogee kick stage malfunctioned. By December 2008, a total of 16 launches were carried out, with a success rate of 100%.

ChangZheng 3B

ChangZheng 3B (Chinese Internet)

The ChangZheng 3B was developed in the 1990s to provide commercial satellite launch services for domestic and international customers. By adding four liquid-propellant strap-on boosters to the CZ-3A, the GTO payload capacity of the launcher was increased to 5,100kg, making it the most capable launcher currently in use in the PRC, and at the time of its introduction the second most capable SLV in the world, only after the Russian Proton.

The ChangZheng 3B was introduced in the early 1990s to succeed the problem-prone ChangZheng 2E. The maiden flight of the ChangZheng 3B took place on 14 February 1996 GMT (15 February local time), carrying a commercial satellite Intelsat 708. Only two seconds after lifting off from the launch pad at XSLC, the launch vehicle began to veer off course. The vehicle and the payload then hit the ground and exploded at T+22 seconds, destroying the US$125 million satellite. The Chinese official media confirmed that six people were killed during the accident, with another 57 injured. However, some foreign reporters who witnessed the accident estimated that as many as 500 people could be killed.

The 15 February failure was the most severe accident in the history of PRC’s space programme, and possibly the worst in the world. The cause of failure was traced to the CZ-3B's guidance and control subsystem. A gold-aluminium solder joint in the output of one of the gyro servo loops failed, cutting electrical current output from the power module and causing the inertial reference platform of the vehicle's guidance and control system to slope. This caused computers to send the vehicle veering off the planned trajectory shortly after lift-off. The failed module was the only one of six similar modules that lacked conductive adhesive to reinforce the solder joint.

ChangZheng 3C (Chinese Internet)

Despite the initial failure, the CZ-3B made a second launch successfully on 20 August 1997, sending the Philippine Agila 2 MABUHAY satellite into the GTO. This was followed by another eight consecutive successful launches by October 2008.

ChangZheng 3C

In order to fill the payload capacity gap between the ChangZheng 3A and 3B, CALT developed the CZ-3C, which is almost identical to the ChangZheng 3B, but fitted with only two strap-on boosters. The ChangZheng 3C has a GTO payload capability of 3,800kg, making it suitable for the launch of smaller satellites. The launcher was first revealed in the mid-1990s, and the design was approved by the CASC in 2001. The first launch of the CZ-3C took place on 25 April 2008.

Last update: 20 February 2009