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Changzheng 2
The Changzheng 2 (CZ-2, or "Long March 2") was the space booster version of the Dongfeng 5 (CSS-4) ICBM. The rocket was later developed into a successful family of commercial space launch vehicles, including the Changzheng 2 series for LEO launches, the Changzheng 3 series for GTO launches, and the Changzheng 4 series for polar orbit launches. These Changzheng rockets have been the workhorse of the Chinese space programme over the past 40 years, and are expected to continue serving for at least another decade.
Development History
The CZ-2 began with the request in the late 1960s for a new rocket to launch the 1,800kg FSW recoverable remote-sensing satellite. The First Space Academy (now CALT) was asked to develop the launch vehicle based on its two-stage, liquid-propellant Dongfeng 5 (DF-5) ICBM. The design team submitted two design proposals. The first design proposal would use a newly-designed 55t-thrust YF-25 engine to replace the original YF-23 engine on the second-stage of the DF-5, so that the rocket would work long enough to send a heavier payload into space. This design could increase the payload capacity by 500~800kg.
The second design proposal kept the original DF-5 design but focused on optimising the rocket’s fight profile to increase its payload capacity. By extending the burn time of the swivelling venire motors on the second-stage engine, the payload capacity of the rocket could be increased by 500kg. The two designs were being developed in parallel, but the delay in the development of the YF-25 engine meant that only the second proposal was available at the time. The YF-25 engine finally passed the 130 seconds ground test in 1979. However by then the design proposal was given up.
Despite the high priority of the programme, the development was repeatedly delayed due to technical difficulties. The first depressed trajectory flight of the DF-5 on 10 September 1971 was only partially successful. The second missile, which was launched on 8 April 1973, exploded in the midair 43 seconds into the flight. The DF-5 development was suspend and the First Academy was asked to modify the remaining three test missiles into space launch vehicles.
On 5 November 1974, the first CZ-2 rocket carrying an FSW-0 (Jianbing 1) satellite was launched from the Jiuquan Satellite Launch Centre. However, the vehicle exploded in the midair only 20 seconds into the flight. The following investigation showed that the anomaly was caused by a disconnected cable for the pitch rate gyro signal in the rocket’s guidance system. A year later, on 26 November 1975, the second CZ-2 rocket successfully sent an FSW-0 satellite into its intended 185km Low Earth Orbit. This was followed by two more successful launches in December 1976 and January 1978.
In 1979, the Chinese military ordered six more CZ-2 rockets for subsequent FSW satellite launches. As the rockets from the Barch-01 production of the DF-5 were all used up, the new rockets would be built by converting the missiles in the Batch-02 production of the DF-5. The First Academy used the opportunity to introduce a number of improvements to the rocket’s design. This version of the rocket was designated CZ-2C.
In February 1982, the FSW satellite and CZ-2C rocket were officially enlisted by the People’s Liberation Army, with the costs for future launches being covered by military budget. The production of the satellite and launch vehicle, and the launch operations, would be overseen by the PLA Commission of Science, Technology and Industry for National Defence (COSTIND). This marked the beginning of the batch production of the CZ-2C.
Design Concept
The CZ-2 is a two-stage rocket powered by a liquid bipropellant, with unsymmetrical dimethylhydrazine (UDMH) as fuel and nitrogen tetroxide (N2H4) as an oxidiser. Each stage had two main propellant tanks made of high-strength, lightweight aluminium-cooper alloy. They formed part of the stage’s thrust and weight bearing load structure and were connected by an inter-tank section. The upper tank contained the N2H4 oxidiser, while the lower tank contained the UDMH fuel. Both tanks were pressurised to ensure that they didn’t collapse under their own weight. At the base of the stage is a weight bearing structure that mounted the rocket engine.
The first-stage of the rocket was powered by an YF-21 rocket engine, which consisted of four parallel 75t-thrust YF-20 chamber motors with swinging nozzles. The first-stage was connected to the second-stage via a mesh-bar inter-stage section. The second-stage was powered by a 75t-thrust YF-22 motor with a fixed nozzle, and a swivelling venire motor consisting of four 4.8t-thrust YF-23 chamber motors. The swivelling venire motor was designed for steering and sustaining propulsion for a further 190 seconds after the shutting of the main motor, which would increase the effective payload capability of the vehicle.
This design was also used as the core vehicle of almost all modern Chinese launch vehicles. The CZ-2E and 2F added the vehicle with four strap-on boosters with fixed nozzles. The Changzheng 3 series added the vehicle with a LOX/LH2 third-stage. The Changzheng 4 series added the vehicle with a conventional third-stage which also used the N2O4/UDMH propellant.
CZ-2 Chronology
Sept 1967: The First Academy was tasked with the development of a space launch vehicle based on its DF-5 ICBM design to support the launch of the FSW satellite.
14 June 1969: The first successful ground test of the YF-21 liquid engine.
1973: The First Academy began to convert DF-5 missiles into space launch vehicles.
5 Nov 1974: First FSW launch failed. Launch Site: Jiuquan; Payload: FSW-0-00; The rocket carrying the satellite exploded 20 seconds into the flight. Later investigation suggested that the accident was caused by a disconnected cable for the rocket’s pitch rate gyro signal.
26 Nov 1975: First successful FSW launch. Launch Site: Jiuquan; Payload: FSW-0-01; Payload mass: 1,790kg; The satellite was successfully placed into a Low Earth Orbit (Apogee: 479km; Perigee: 177km; Inclination: 63°; Period: 91.1min). The satellite was recovered three days later.
7 Dec 1976: Second FSW launch. Launch Site: Jiuquan; Payload: FSW-0-02. Payload mass: 1,812kg; Apogee: 489km; Perigee: 159km; Inclination: 59.4°; Period: 91.1min.
26 Jan 1978: Third FSW launch. Launch Site: Jiuquan; Payload: FSW-0-03. Payload mass: 1,810kg; Apogee: 509km; Perigee: 167km; Inclination: 57.0°; Period: 91.1min.
Last updated: 23 February 2012