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Dongfeng 4
The Dongfeng 4 (DF-4), is a two-stage, liquid-propellant, single-warhead intermediate-range ballistic missile (IRBM) that entered operational service with the PLA Second Artillery Corps in 1980. The Dongfeng 4 was based on the single-stage Dongfeng 3 medium-range ballistic missile (MRBM), added with a second-stage for increased range. The PRC has also developed Dongfeng 4 into the Changzheng 1 space launch vehicle (SLV). The 2009 Pentagon report on the PRC’s military power estimated that 15~20 Dongfeng 4s and 10~15 launchers were in operational by 2009.
Programme
After the successful development of several single-stage ballistic missiles, the PRC began to seek more advanced multistage missiles with longer range. The Ten-Year Plan of Defence Science and Technology in 1963 outlined the next stage of the PRC’s ballistic missile programme was to grasp the multistage rocket technology in order to develop the intercontinental ballistic missile (ICBM) and space launch vehicle (SLV). Since the PRC had never developed a multistage rocket before, Chinese scientists suggested to develop a two-stage rocket SDF-4 as a testbed for developing concepts and technologies for the ICBM system. The SDF-4 uses the single-stage Dongfeng 3 as its first stage, and is added with a newly-developed second-stage.
By 1964, the conflicts in Vietnam had escalated into a full-scale war and the Republic of China forces in Taiwan was actively preparing for an invasion on the China mainland. The worsening international situation had led to the speed-up of the PRC’s ballistic missile programme. As a result, in 1965 the SDF-4 programme evolved into the Dongfeng 4 IRBM with the objective of fielding a 4,000km-range missile capable of hitting the U.S. bases in Guam.The Dongfeng 4 adopted the YF-1 rocket engine originally developed for the Dongfeng 3 as its first stage. The engine burns unsymmetrical dimethylhydrazine (UDMH) as fuel and red fuming nitric acid (HNO3) as an oxidiser. On later PRC ballistic missiles, nitrogen tetroxide (N2H4) replaced HNO3 as an oxidiser to achieve an increased thrust-to-weight ratio. An improved Dongfeng 4A design using the HDMH/N2H4 propellant was proposed in 1966 but was not adopted. The guidance of Dongfeng 4 was a cascade compensation inertial guidance system derived from a similar system used by the Dongfeng 3. The three-megaton thermonuclear warhead, codenamed “512”, was also based on the design of the Dongfeng 3's warhead.
The main challenge for a multistage rocket system was the inter-stage separation, the jettison of the stage that runs out of propellant, and the ignition of the next stage, without interfering the missile or SLV’s flight. The Dongfeng 4 adopts a “hot” inter-stage separation, where the adjacent stages are separated by the impingement of the hot exhaust gas jet from the engine of the ongoing stage. The engine of the second-stage ignites when the two stages are still connected together, thus, eliminating the need for jettisoning devices to provide the separation impulse and considerably reducing the none control duration during the separation. A fibreglass heat insulation layer is added on the top of the first-stage tank to prevent damage due to the high pressure and hot stream of engine exhaust from the upper stage.
A second technical challenge was to develop the new YF-3 rocket engine for the second-stage, which is required to be able to ignite in a near-vacuum condition, due to the missile’s trajectory (>60,000m) expanding outside the Earth’s atmosphere as its range increases. Other challenges included the heat shield of the warhead, and a guidance system with improved accuracy to compensate the deviation resulted by the extended range.
As the existing “Project 150” optical tracking system could not meet the requirements for the flight test of long-range missiles, the PRC built the “Project 154” missile telemetry and tracking system in 1969 at the Jiuquan Missile and Space Centre. A new missile launch base was built in the northeast part of the country in order to carry out the full-range flight test within the PRC's territory.
Following two unsuccessful attempts in late 1969, the first depressed trajectory flight test of Dongfeng 4 was carried out from the Jiuquan Missile and Space Centre (Base 20) on 30 January 1970. The two stages of the missile separated and the second stage ignited successfully as scheduled, and the warhead hit the target spot with high accuracy. This was the first multistage rocket launch of the PRC, an important milestone in its ballistic missile programme. Three months later, on 24 April, a modified Dongfeng 4 with an extra stage, designated Changzheng 1, successfully sent the PRC’s first satellite Dongfanghong 1 into the orbit.
The Dongfeng 4 was originally intended for threatening the U.S. bases in Guam. However, the worsening relations with the Soviet Union in 1969 led to the decision to increase the missile’s range to 4,700km in order to reach Moscow and other targets in Europe Russia from Western China. A modified engine with increased thrust and prolonged burn time was developed as a result. A 280-second burning test of the new engine was carried out successfully in July 1970, but the modified missile was not completed until 1976 due to the political impact of the ‘Culture Revolution’. The revised missile design was tested in two depressed trajectory flight tests in 1976 and five full-range flight tests in 1977~78. The first launch of the missile by the PLA Second Artillery Corps took place in November 1977.
The Dongfeng 4 design was finalised between 1980 and 1983, the missile was class certified in June 1983. However, the modified “512” warhead was not completed until August 1988. The whole development programme lasted 18 years due to changing requirements and political impact. Although the PLA Second Artillery Corps activated two Dongfeng 4 launch regiments as early as 1968, followed by a third regiment in 1970, the initial operational capability of the missile was not achieved until the late 1980s. In 1986, the PLA Second Artillery Corps launched a Dongfeng 4 missile carrying a dummy warhead from the Northeast Missile Test Base during a simulated nuclear retaliation operation. This was the first operational launch of the Dongfeng 4.
The Dongfeng 4 was produced in four batches. The Batch-01 produced in 1969 included 7 examples for initial flight tests and two in the form of the Changzheng 1 SLV. The Batch-02 produced in 1976 included 11 examples in the extended-range version for the design certification flight tests. The Batch-03 produced in 1985 was the first operational version of the missile. The Batch-04 was produced in the mid-1990s. The missile has been regularly launched for training and exercise. The latest launches took place in 1997, 2002, 2004 (two launches), 2005, 2008, and 2009. The missile is expected to continue serving with the PLA for at least another decade.
Design
The Dongfeng 4 is the PRC’s first two-stage ballistic missile. The missile is 29m in length and 2.25m in diameter, and has a total mass of 82,000kg. The first stage of the missile uses four 255kN-thrust YF-1 rocket motors. The second-stage uses a single 320kN YF-3 rocket motor. Both stages burn a storable liquid propellant UDMH/HNO3. The missile uses a cascade compensation inertial guidance system, with an estimated CEP of 1,190m. The missile carries a single three-Megaton thermonuclear warhead for destruction of civilian population centres and large military complexes, but the missile’s accuracy is not sufficient for hitting point targets such as missile silos.
The Dongfeng 4 was the PRC's first underground-silo-deployed missile. The missiles are stored vertically in underground silos and raised to surface level before firing, much like the early U.S. Titans and Atlases. The missile are fuelled inside the silos up to 15 days prior to the firing. This configuration was first tested on 9 February 1980. The cave-deployed version was designed to be stored horizontally in a tunnel, and rolled out to a pre-surveyed launch spot immediately outside the mouth of the tunnel, erected, fuelled, and fired. There are also launch pads suitable for Dongfeng 4 at several missile and space test centres.
Last updated: 20 May 2012