These air defense systems were supposed to operate both centrally and autonomously, searching for and detecting targets of the division's radar station. The high probability that the actions of the ground forces with the participation of a large number of armored vehicles would be dynamic and maneuverable required their protection with the help of air defense systems with a deployment time of 5-10 minutes. At the same time, the military air defense systems themselves had to have high mobility and maneuverability, equipped with navigation and topographic equipment, equipped with telecode radio communications for exchanging command and technical information with each other, automating all combat operations, and have built-in power units. The required level of their reliability and combat readiness during operation in the troops had to be supported by highly mobile repair and control stations.
For the first time, the task of creating a military air defense system was formed in the Decree of the Council of Ministers of the USSR dated March 27, 1956, which provided for the development of a complex capable of hitting air targets at a distance of up to 20 km, in the range of heights from 2 to 12-15 km and at speeds up to 600 m / from. However, this work did not leave the project stage. Therefore, the solution of the tasks of the military air defense for the next few years was to be carried out by the S-75 and S-125 air defense systems.
S-75 - mobile anti-aircraft missile system
In the late 1950s. the leadership of the USSR came to grips with the problems facing the military air defense systems. In August 1958, an independent branch of the armed forces was formed - the Air Defense of the Ground Forces. Shortly before this, the military-industrial complex (MIC) began the first full-scale work on the creation of military air defense systems - the Krug and Kub complexes, in the tactical and technical requirements for which the above parameters were set in terms of cross-country ability, time of putting into combat readiness, stability of communication between by means of the complex.
The management of the program for the implementation of the first military air defense missile system 2K11 "Circle" was entrusted to 31, the summer chief designer of the Moscow Research Institute-20, Veniamin Pavlovich Efremov.
ZRK 2K11 "Circle"
Initially, the "Circle" was intended to destroy targets flying at speeds up to 600 m / s at altitudes from 3 to 25 km, at a distance of up to 45 km. It was supposed to include a 1S12 detection and targeting station (the lead executor - NII-208), a 1S32 missile guidance station (NII-20). An unexpected problem was caused by the choice of a missile developer. The joint Resolution of the Central Committee of the CPSU and the Council of Ministers of the USSR on the development of the Krug military air defense system, adopted on February 13, 1958, did not mention the already recognized by that time authorities in the field of creating anti-aircraft missiles OKB-301 S.A. Lavochkin and OKB-2 P .D. Trushin. The development of a rocket for the "Circle" from the very beginning acquired a competitive character. One of those who received an offer to develop it was the engine-building OKB-670 of M.M. Bondaryuk. The reason for such an unusual choice was that already the first estimates showed that the basis of the design of the new the rocket will be a ramjet engine. But M.M. Bondaryuk rightly judged that if the design bureau could cope with the propulsion part of his design bureau, then it would hardly be possible to deal with all the other elements of the rocket - the development of the airframe and various equipment.
For some time, they worked on their version, the S-134 missile, at the TsNII-58, headed by the famous artillery designer V.G. Grabin. However, in the summer of 1959, after the accession of TsNII-58 to OKB-1 Korolev, this topic was closed, as it did not coincide with the main direction of the enterprise's work.
As a result, the "Circle" was transferred to the Sverdlovsk artillery OKB-8, which drastically influenced the further fate of the enterprise. Its leader, Lev Veniaminovich Lyuliev, reacted to the task of developing a new missile with great, although not entirely justified, optimism. As he said later. "At that moment, I was poorly versed in missiles and could not imagine all the difficulties that we will have to face in developing them." But as time has shown, Lyuliev managed to find the right ways and approaches to this work, which was started with the accelerated training of specialists. In order not to waste precious months looking for young specialists who graduated from specialized (mainly Moscow) institutes, or persuading the management of other design bureaus to release "extra" rocket specialists, Lyuliev, with the support of the leadership of the military-industrial complex, agreed to send his leading workers to OKB-2 P.D. Grushina, to work as trainees in the design and engineering departments. Having thus acquired the much-needed initial baggage of knowledge and experience, the Sverdlovsk citizens began to design their rocket. And they turned out to be more than capable students. The rocket and launcher they created differed from analogues in innovative solutions.
Initially, the rocket for the "Circle" was created in two versions, with different guidance systems: ZM8 with a radio command, and ZM10 with a combined - radio command in the main area and homing with a semi-active radar head - at the final. But later we stopped at the ZM8 version.
The ZM8 rocket was made according to the aerodynamic X-shaped scheme with rotary wings; and the stabilizers - according to the "+" scheme.
The design of the rocket was two-stage - with a solid-propellant booster and a sustainer ramjet engine running on kerosene. Such a propulsion system was several times superior in energy to other types of rocket engines. At high supersonic speeds, it was more economical than a turbojet engine, had a simple design and was relatively cheap. However, these advantages hid many problems, about the ways of solving which many rocket scientists at that time had only the most approximate judgments.
In the final design, the missile's main stage hull was a ZTs4 supersonic ramjet engine with a recessed central body, which housed a 150 kg warhead, a radio fuse and an air pressure accumulator balloon. Further along the engine path, there were straightening grids, nozzle blocks and combustion stabilizers. The fuel supply was provided by a turbopump unit, for the operation of which isopropyl nitrate monofuel was used. In the central part of the annular body of the engine, tanks with kerosene, steering gears, wing attachment points were located, and in the tail section - the control system equipment blocks.
The launch and acceleration of the rocket to supersonic speed was provided by four ZTs5 side solid-fuel boosters from the 2P24 launcher. To separate them from the sustainer stage, a pair of small aerodynamic surfaces were fixed on each of them.
The launcher was created at OKB-8 on the chassis of a 100-mm self-propelled gun SU-100P. The artillery part of the launcher included a support beam with a boom hinged in its tail section and lifted by two hydraulic cylinders. On the sides of the boom, brackets with supports were attached to accommodate two missiles. The missiles could be launched at an angle of 10 to 55 degrees to the horizon. At the start of the rocket, the front support swung down sharply, making way for the passage of the lower stabilizer console. In the process of acceleration, the rocket was supported by additional supports, also fixed to the boom. One support of the truss was brought in from the front and fixed both missiles. Another support was advanced from the sides opposite to the arrow.
The first throw-in launch of the ZM8 product, equipped with full-scale starting engines, took place on November 26, 1959, the rocket energetically left the launcher, but collapsed during the separation of the starting accelerators. However, for the young team, the result of the first launch was more than worthy. And soon, attempts began to fly with a running main engine, during which the residents of Sverdlovsk had a chance to face many previously unfamiliar problems. Thus, the first attempts to launch a main engine in flight were accompanied by surge, during which the rocket lost controllability. As one of the participants in these works noted later: “Each ramjet is unique in its specific design. About ten thousand nozzles had to be annealed before its optimal shape was found. Each step during development was difficult and was done literally from scratch. "
Zur 3M8 exhibit National Museum of the US Air Force (National Museum of the United States Air Force)
Required additional study and issues of ensuring the vibration resistance of the onboard equipment of the rocket and shielding the transponder antenna from the combustion products of the main engine. The problem of the "8st second", which manifested itself in the first launches of the ZM31, was connected with the latter, after which the signal of the onboard transponder disappeared several times on the 1C32 radar. The solution to this problem was found by V.P. Efremov, who proposed to transfer the transmitting-receiving antennas from the rocket body to the stabilizer. In general, of the 1960 rocket launches carried out before the end of 26, only 12 were successful.
But by this time, another participant in the competitive development began to step on the heels of ZM8. OKB-2, which proposed the 19D rocket. The proposal to develop this missile for the "Circle" was received at the beginning of 1959, after the release of a preliminary design for the 17D rocket, intended for use as part of the modernized S-75 air defense system, as well as the M-31 shipborne air defense system. In the decree issued on July 4, 1959 this initiative was supported by the country's leadership.
Work on the 19D was transferred to the Moscow branch of OKB-2, since by that time the main problems in creating the 17D were considered close to resolution, and the 19D was supposed to differ from it only in the elements of control equipment compatible with the Krug's guidance means. By April 1960, the branch had prepared a draft design and released the main part of the technical documentation required for the manufacture of prototype missiles.But soon, due to a number of failures in the 17D tests, work stalled, and the full documentation for the 19D was transferred to the plant only in February 1961. As a result, the previously planned dates for testing the Circle with both the ZM8 missile and the 19D missile were disrupted.
At the beginning of February 1961, the heads of enterprises working in the Circle were summoned to a meeting of the Commission on military-industrial issues under the Council of Ministers of the USSR, where they were sharply criticized by the Chairman of the Commission D.F. Ustinov.
Soon a decision of the Commission was issued "On the unsatisfactory state of work on the creation of the Krug military anti-aircraft complex." It noted that most of the enterprises “… did not complete this development in a timely manner and thwarted the deadline established by the government document for presenting the complex for joint tests., Made a significant lag in the development of a prototype guidance station,… they are unacceptably slow in developing the rocket,… the manufacture of missiles does not provide the normal course of tests. "
However, the first real results from this “shake-up” were obtained only by the end of 1961, although all participants in the work made every effort to achieve them. So, on August 25, after another series of failures during the ZM8 launches, a special commission was created, which developed proposals for the next modifications of the rocket - ways to eliminate burnouts of the combustion chamber of the main engine, failures of on-board equipment, and insufficient strength of structural elements.
In the fall of 1961, to replace the experimental model of the complex, which was used to carry out comprehensive factory tests, the elements of the first prototype arrived at the test site. At the end of the year, the first ZM8 was prepared for testing in a closed guidance loop and received confirmation of the correctness of the decisions made by the developers of the complex, after which they began to fine-tune its equipment, including the control system. Then, having received information about the first successful launch of ZM8 in a closed loop, D.F. Ustinov demanded that the developers of the "Circle" begin joint tests in March 1962.
However, 1961 cannot be called successful for its developers. Now the 19D developers couldn't keep up with the pace reached by the Krug developers. In the same 1961, only five of these missiles were manufactured and sent to the test site, of which only one was launched from the 2P28 launcher, made especially for it in a single copy based on the SU-1 PLO. Work on the 17D rocket also developed unsuccessfully. The next stage in deciding on its fate was the period from February to May 1961, when it was planned to end the development of 17D in the control loop of the S-75M air defense system. But it was not possible to meet this deadline either. After the S20M air defense missile system with a 1961D missile was adopted on April 75, 20, the tension in work on the 17D began to subside. The process of its fine-tuning began to resemble more and more the work on testing a flying laboratory, which included the development of promising solutions. And, ultimately, in the summer of 1963, work on 17D and 19D was stopped.
The upgraded anti-aircraft missile system C-75-2 "Volga-2A"
Meanwhile, in the winter of 1963, a prototype "Circle" with ZM8 missiles was first demonstrated at the Kubinka training ground for the country's leadership. And by that time at the Emben test site, its intensive tests were already underway, which at the final stage were mostly successful. After several dozen launches, the state commission chaired by A.G. Burykina recommended the complex for adoption. On October 26, 1964, a corresponding resolution was issued by the country's leadership, and a year later, on November 7, 1965, Krug launchers with ZM8 missiles were first shown at a military parade on Red Square in Moscow.
In general, the developers of the "Circle" managed to fulfill most of the requirements set in 1958. Thus, the range of the complex was from 11 to 45 km, the height of target destruction was from 3 to 23,5 km at a flight speed of up to 800 m / s. The reaction time of the complex was 60 s, the mass of the rocket was 2450 kg. At the same time, according to the results of state tests, a list of more than a hundred comments and suggestions was compiled, which were proposed to be implemented in further work on the "Circle".
The main ones were:
- expansion of the “Circle” affected area;
- increasing the effectiveness of shooting at some points of the affected area, especially at low altitudes;
- determination of the accuracy characteristics of the radar in the presence of "mirror" surfaces.
These works were supposed to be carried out in several stages. As a result, in 1967 the Krug-A air defense missile system was adopted, for which it was possible to reduce the lower boundary of the affected area to a height of 250 m and bring the close border closer to a range of 9 km.
At the next stage of work, in 1971, the Krug-M air defense system was adopted, the far border of the affected zone of which was increased to 50 km, and the upper one - to 24,5 km.
Another version of the Krug-M1 air defense missile system, put into service in 1974, could hit targets at a minimum altitude of 150 m and a minimum range of 6-7 km.
For several decades, the Krug air defense system was in service with the air defense units of the Land Forces of the USSR of the Warsaw Pact countries and a number of countries in the Middle East. And although during its many years of service this complex never took part in hostilities, its creation and operation was an important event in stories development of domestic military air defense.
In the 1990s, at the stage of the completion of the combat career of the Krug complex, the 8M9 Virage targets were developed on the basis of the ZM319 family of missiles.