The Long March 3 (Chang Zheng-3, or CZ-3) is a family of orbital launch vehicles designed for launching geostationary communications satellites and deep-space probes. First introduced in 1984, the three-stage launch vehicle was designed to send the payload into a highly elliptical Geostationary Transfer Orbit (GTO), where the satellite then uses its own apogee kick stage to move to its intended location on Geostationary Earth Orbit (GEO).
China initiated the indigenous geostationary communications satellite programme in 1975 under the code name Project 331. The Ministry of Astronautics decided in 1977 that the satellite was to be launched by a three-stage, liquid-propellant launch vehicle based on the Long March 2. The 1st Academy (CALT) was tasked with the launch vehicle’s overall design and the third-stage. The 8th Academy (SAST) was responsible for the development of the first- and second-stage. Base 067 (AALPT) was put in charge of the liquid engines.
The two R&D academies each submitted their proposal for the new launch vehicle. Both proposals were based on the two-stage Long March 2, but differed in their third-stage designs.
The Long March 2A concept, proposed by SAST, featured a YF-40 third-stage engine burning burning the conventional N2O4/UDMH bi-propellant. The technology was relatively mature and would require less time to develop, but at the expense of a lower payload capacity.
The Long March 2B concept, proposed by CALT, featured a YF-73 third-stage engine burning the cryogenic LOX/LH2 bi-propellant. The low boiling points of liquid oxygen and liquid hydrogen made it difficult to store and transport, and the propellant is highly inflammable and explosive. The technology was more challenging to develop but could offer a higher payload capacity.
The Ministry of Astronautics and the military were originally favouring the more advanced YF-73. However, an explosion during a ground test of the engine in January 1978, followed by a fire incident in March of the same year, led to serious doubt about the design. The development was only saved after Ren Xinmin, Director of the 1st Academy and a founding member of China’s missile and space programme, persuaded the military to continue their endorsement for the project.
The YF-73 engine finally passed the 800-second ground burning test in 1980, paving the way for the engineering development of the launch vehicle, which was subsequently renamed Long March 3.
A ground test vehicle was delivered to Xichang Satellite Launch Centre for a launch rehearsal in 1983. The first flying vehicle was delivered to Xichang on 1 January 1984. The launch was originally scheduled for 26 January. However, the final examination of the launch vehicle on the pad identified a fault with the its inertial guidance platform. The satellite and payload fairing had to be removed from the launch vehicle in order to allow the faulty platform to be replaced. This delayed the launch by three days.
At 20:24 CST on 29 January 1984, the Long March 3 (Y1) vehicle carrying the Dong Fang Hong 2 (#01) experimental communications satellite blasted off from Pad 3 at Xichang. The launch vehicle’s first- and second-stage worked normally. The third-stage ignited and shut down as scheduled, but failed to re-ignite after entering the 400 km initial parking orbit. As a result, the satellite was placed into an elliptical orbit (Perigee: 400 km; Apogee: 64,800 km) instead of GEO. Despite the failure, the ground control was able to test the positioning and data transmission with the satellite on the wrong orbit.
Two months later, on 8 April at 19:20 CST, the Long March 3 made its second flight Xichang, successfully placing its payload, Dong Fang Hong 2 (#02), into the GTO. Six days later, the satellite was moved to its intended position at 125°E on GEO, making China the fifth country in the world capable of developing and launching geostationary satellites.
In 1985, the Chinese Ministry of Astronautics announced its intension to provide commercial satellite launch service for foreign customers using its Long March launch vehicle family. On 7 April 1990, a Long March 3 launched from Xichang successfully placed the U.S.-built Asia 1 communications satellite into orbit. This was China’s first commercial satellite launch.
Flight Sequence and Trajectory
The Long March 3 was launched from Xichang Satellite Launch Centre located in the central-western province of Sichuan. The first-stage was shut down and jettisoned at T+126 seconds. The payload fairing was jettisoned at T+259 seconds. The main engine of the second-stage was shut down at T+255 seconds. The second-stage was jettisoned at T+263 seconds.
The third-stage sent the satellite into an initial parking orbit (Perigee: 170 km; Apogee: 450 km; Inclination: 27°) before shutting down its engine. The satellite, still attached to the rocket, flew powerlessly until it reached the equator plane. The third-stage engine then re-ignited to push the satellite into a transfer orbit (Perigee: 400 km; Apogee: 36,000 km), where the satellite then used its own apogee kick stage to move to the intended location on GEO.
The entire flight lasted 1,245.34 seconds, flying over Sichuan, Hunan, Guangxi, Guangdong, Fujian, and then over the southern tip of Taiwan to fly above the Pacific. The satellite is then inserted into orbit at 160.33°E above the Equator.