DF-4 - Task origin and scheme design
In 1963, the Ten-Year Plan for National Defense Science and Technology proposed that the development path for the second stage of surface-to-surface missiles should be centered on the development of multi-stage rockets to develop intercontinental missiles. During the exploration of intercontinental missiles at that time, the designer believed that the span from medium-range missiles to intercontinental missiles was too large, and there should be a technical step in the middle. It is envisaged to develop a two-stage test rocket based on medium-range missiles as a transition to The multi-stage rocket technology that must be encountered to solve intercontinental missiles. This model is slightly improved and can be used as a launch vehicle for launching satellites. This is the multi-stage test rocket (codenamed "SDF-4").
In early 1964, Liu Xuan, Zhang Jun, etc. of the First Branch of the Fifth Academy of National Defense presided over the demonstration of the technical approach for the development of medium- and long-range surface-to-surface missiles, and proposed that through the development of this model, multi-stage rocket technology should be broken through. The basic pre-research on the multi-stage rocket also began. At that time, it was proposed to focus on solving the connection and separation of two-stage missiles, separation transition attitude control and engine high-altitude ignition technology. In the autumn of 1964, the Central Special Committee and the General Staff clearly stated that a long-range strategic missile should be developed as soon as possible to meet the needs of the sudden change in the international situation. In this way, the plan evolved from the development of multi-stage test rockets to the development of a new medium- and long-range strategic missile.
The fifth branch and one branch of the Ministry of National Defense made in-depth studies on the technical approaches that should be taken to develop such missiles. At the end of 1964, two schemes were proposed: the first scheme was to develop a medium-range missile as the first stage, with a slight modification as the first stage, and then use the medium-range missile single-tube engine as the power plant to design a new second stage to form A two-stage missile; the second plan is to develop long-range and intercontinental missiles directly, that is, to design a large-diameter two-stage missile with different weight warheads, taking into account both long-range and intercontinental ranges. At the beginning of December of that year, Vice President Tu Shouyi of the First Branch pointed out in his report to the Fifth Court that the branch preferred the first plan and believed that this plan did not have many key technologies and could make full use of the achievements and technological equipment of medium-range missiles to accelerate development. Progress, to achieve the goal of developing successful long-range missiles and launching artificial satellites as early as possible.
On February 3-4, 1965, the tenth meeting of the Central Committee of the Central Committee determined that the Fifth Institute of the Ministry of Defense (which has been established as the Seventh Ministry of Machinery Industry) demonstrated the medium and long-range missile organization and submitted a report. To this end, a branch (which has been renamed the First Research Institute of the Seventh Ministry of Machinery) mobilized the masses to carry out large-scale discussions on the development of surface-to-surface missiles. The big discussion started on February 18 and ended on March 7 and lasted 18 days. Premier Zhou Enlai also appointed Zhao Erlu, deputy director of the National Defense Industry Office, to participate in the seminar. This seminar listened to opinions from various parties, not only put forward the development plan for the next few years, but also demonstrated the technical approaches of some missile models. At that time, all parties believed that a medium- and long-range test rocket should be developed, but whether it was used as a single model was still controversial. In the technical approach to this rocket, it is proposed that the control system adopts the position strapdown guidance scheme, the inertial instrument adopts the air floatation technology, the computing apparatus uses the digital scheme, the attitude system uses the rate gyro, the gas rudder, and the automatic test scheme is used.
On March 8-9, 1965, the Standing Committee of the Party Committee of the First Ministry of the Seventh Ministry of Machines determined that the medium and long-range missiles were included in the development plan as an independent model. The reason is: first, it can technically break through the two-stage rocket technology for intercontinental missiles; second, it can cover the area between medium-range missiles and intercontinental missiles for military use, and it can be slightly improved for launching man-made missiles. Satellite; third, it can be two years faster than intercontinental missiles.
On March 11, 1965, the Party Committee of the First Court reported the "Ground-to-Ground Missile Development Plan" (that is, the "eight-year four-bomb" plan), which stipulated that the Dongfeng No. 4 medium- and long-range missiles should adopt a two-stage layout and use Dongfeng No. 3 medium-range missile As the first stage, the second stage uses a single-tube engine with high-altitude nozzles. The technical key is: the separation between the two-stage rocket, the high-altitude ignition of the second-stage rocket engine, improve the accuracy of the gyroscope and the gyroscope accelerometer, and at the same time put forward the tactical technical indicators such as the range and accuracy of Dongfeng-4. The "four bombs in eight years" plan carried out systematic research and planning on the development plan for strategic missiles from 1965 to 1972. From the combination of two bombs to medium- and long-range missiles, and finally to intercontinental missiles, clear regulations were made. The plan takes into account both the needs of national defense construction and the long-term development of China ís rocket and aerospace technology; it takes into account both technical feasibility and economic affordability, and is a scientific and feasible plan.
On March 20, 1965, the eleventh meeting of the Central Special Committee approved the plan in principle, requiring medium and long-range missiles to begin flight tests in 1969 and finalization in 1971. In May 1965, the Central Special Committee approved the development mission of medium- and long-range surface-to-surface missiles. The Seventh Aircraft Department determined that Ren Xinmin would preside over this development work, and since then, Dongfeng No. 4 has officially started development as an independent missile model.
On April 27, 1965, in order to develop the Dongfeng No. 4 medium- and long-range missile, the First Institute proposed two-stage rocket separation technology, warhead heat protection technology, second-stage engine, high-altitude engine ignition, high-precision inertial device, automated testing, digital device, Large-scale test equipment is regarded as a key research project. The overall design department of the institute put forward requirements on engine performance indicators that month, and the Liquid Rocket Engine Research Institute developed the drawings accordingly, and subsequently issued drawings to start trial production. On the whole, the party committee of the First Court decided in mid-June to immediately organize a medium- and long-range missile development team and complete the plan design in the second half of the year. At the same time, the development progress of the model is also proposed.
On July 15, 1965, the first meeting of the chief designer of Dongfeng No. 4 was held at the First Academy. The meeting discussed the development method of the missile, and proposed that the development work should be taken in two steps: the first step is to make full use of the technical achievements of the Dongfeng-3 medium-range missile, and strive for the flight test in the second quarter of 1967 without higher requirements for accuracy It is to solve the key technology of the two-stage rocket; the second step is to improve the accuracy and solve the matching problem with the ground equipment. The construction was approved by the office meeting of the hospital on July 28. By the end of the year, the development of Dongfeng No. 4 was progressing well. The schemes that have been determined include two-stage separation, two-stage projectile structure, two-stage execution mechanism, guidance system, stability system, ground test equipment, high-altitude engine delivery system, first-stage gas rudder, etc. The pending plans include aiming, thrust adjustment, head separation, and firing method.
Shortly after the start of the development work, the Dongfeng No. 3 single-tube engine (code-named YF-1) succeeded in carrying out a research trial using nitrous oxide instead of nitric acid as the oxidant. The thrust and specific thrust of "YF-1" have been improved to some extent. Therefore, some scientists advocated replacing the "YF-1" engine with propellant, and proposed measures such as lengthening the propellant tank and improving the control system to develop Dongfeng-3. A replaces Dongfeng No.4. At the same time, the overall design department of the First Research Institute also proposed to change the original Dongfeng No. 4 proposal to use nitrous oxide and unsymmetrical dimethylhydrazine as propellants to increase the thrust of the two-stage engine, thus forming the Dongfeng 4A Scheme.
On April 5, 1966, the First Ministry of the Seventh Ministry of Machinery decided to further develop the Dongfeng No. 4 program on the basis of the above three programs. After debate, on the basis of the three proposals put forward by the various sub-systems, the office of the institute determined that, in view of the development of Dongfeng 4 for more than a year, the work has been fully rolled out, regardless of the indicators and progress have been implemented, the decision is still in accordance with Dongfeng Plan 4 continues to work. On May 31, the design of Dongfeng No. 4 was completed. These include: proposing an overall plan; determining the main plan of each subsystem and providing each other with the conditions required for preliminary design; determining a large-scale test plan; proposing and implementing the necessary pre-research projects and test projects.
During the demonstration stage of Dongfeng No. 4 program, the guidance system is one of the key contents. As the range of the missile increases and the flight status changes, the requirements for guidance and attitude control systems increase. In the early 1960s, after in-depth research on the theory of linear compensation for strapdown guidance systems, scientists and technicians proceeded from the characteristics of flight interference and its impact on ballistics and the missile ís own measurement function based on the principle of single compensation scheme , Established a "variable parameter linear automatic control system external interference complete compensation theory", and explored a new way for China's strapdown guidance scheme. In August 1965, the First Institute of the Seventh Machinery Department held a demonstration meeting on the control system plan, and repeatedly analyzed the advantages and disadvantages of using the strapdown full compensation scheme for Dongfeng IV. The method error is small, which can meet the accuracy index requirements. It is a further improvement based on the guidance plan of Dongfeng No. 2 and Dongfeng No. 3, and the technology is relatively mature. In November of that year, the office meeting of the First Institute decided that Dongfeng No. 4 adopted the strapdown full compensation scheme.
This scheme not only has lateral guidance, but also normal guidance to ensure that the guidance error of the missile is smaller. The key to the development of the attitude control system is to solve the problems of the stability of the elastic vibration and sloshing of the two-stage missile with a large aspect ratio, and the influence of the interference caused by the separation of the first and second stages on the stability of the second stage control stage. The Institute of Control Systems adopted measures such as selecting a suitable location to install the pitch, yaw rate gyros, and changing the correction network during flight to properly solve the stability problems of elastic vibration and sway.
The Dongfeng-4 missile has a long range, so the accuracy requirements for inertial devices are several times higher than those of Dongfeng-3. The Institute of Inertial Devices chose air bearing instead of ball bearing, which has the advantages of low friction torque and stable friction characteristics under dynamic environment. Since 1965, in the process of developing air float gyroscope and air float gyroscope, the institute has successfully developed a three-stage cylindrical combination and a small cone type air bearing with repeated cones after repeated experiments, design and processing. This air bearing has high accuracy, reliability and good stability. The successful development of air float gyroscope and air float gyroscope is an important breakthrough in inertial device technology. In March 1966, the first prototype of an air-floating dual-axis three-degree-of-freedom gyroscope was officially put into production.
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