In the 1950s of the last century, the USSR defense complex in order to protect the country's airspace from a possible enemy developed and actively introduced stationary air defense systems into the troops.
But the rapidly improving aircraft required the creation of mobile air defense systems to directly cover ground forces from air attacks. This prompted the military complex of the Soviet Union to begin the development of mobile
anti-aircraft missile systems, the result of which was the Krug
air defense system, which was put into service in 1965.
Requirements for the Krug anti-aircraft missile system
The development of a mobile anti-aircraft missile system for the needs of air defense of the ground forces began in 1958 as part of the competitive projects “Theme 2” and “Theme 3”. The decree of the Party Central Committee determined the basic requirements for a new type of weapon:
- Interception of air targets flying at a speed of up to 600 m / s at altitudes from 3 to 25 thousand m.
- The probability of destruction in the air of aircraft such as the Il-72 front-line bomber at altitudes of up to 20 thousand meters is at least 80%.
- Detection of objects with an effective dispersion surface such as the Mig-15 fighter at a distance of at least 115 km.
At the same time, the government put developers in harsh conditions, limiting them in time. The first tests of the new Krug air defense system were to begin in the third quarter of 1961. The project manager was appointed designer V.P. Efremov, who was already known for improving the radar and air defense of the city of Moscow. Research was conducted at the NII-20.
Targets and goals
The terms of reference were approved by the government in 1958. According to him, it was required to construct two fundamentally new anti-aircraft guided missiles - 3M8 and 3M10, with command and mixed types of guidance, respectively.
Research in this direction was undertaken by the design team of OKB-8 under the leadership of S. Korolev, who then became part of the experimental design bureau (OKB-2) under the direction of P. Grushin on the basis of TsNII-58.
In connection with the development of new missiles, the need arose to create new missile launch systems, since existing models did not fit in many ways. To unify the details and reduce the development time of the Krug air defense system, the Kub air defense project under development was taken as the basis.
Historical reference
The main problem that the OKB-2 engineers needed to solve was the creation of guided missiles.
One by one research has failed. Several dozen projects were rejected. But in the end, the first tests conducted in December 1961 showed that the developers are moving in the right direction.
After that, the long process of equipment debugging and preparation for the field tests, which had to go through three stages, began:
- At the first step, factory tests were carried out according to the instructions established by the project manager V.P. Efremov.
- At the second stage, state tests were carried out according to the methods proposed by the test site.
- At the final step, serial samples of the Krug air defense system were tested.
All state tests were successfully passed between 1963 and 1964. And on February 3, 1965, by order of the Minister of Defense of the USSR, the new Krug complex under the code 2K11 was adopted by the air defense of the ground forces.
The composition of the air defense system "Circle"
In 1965, anti-aircraft missile brigades began to form, the main weapon of which was the Krug complex. At the same time, the following units were included in the ZRBr:
- The control platoon as part of the 2C12 target detection station and the Krab-1 target designation receiving cockpit (after 1981 it was replaced by the Polyana D-1 cockpit).
- Three anti-aircraft missile batteries, each of which was formed from the guidance station 1C32, self-propelled launcher 2P24 with two 3M8 SAMs.
- The technical battery, which consisted of a 2B9 test and control station, several 9T226 transporters, and a 2T6 transport-loading machine.
The anti-aircraft missile brigade also included refueling machines and technological equipment, which was used to assemble the missiles and refuel them. All the 2k11 Krug air defense system equipment (except for the loading one) was designed on a caterpillar track.
Missile detection and guidance
1C12 radar was responsible for detecting the enemy. It detected air targets at a distance of 180 km at an altitude of not more than 12 thousand meters and at a distance of 70 km, if the height of the target is less than 500 meters. After identifying the enemy, the station gave target designation to the 1C32 machine.
The missile guidance station was responsible for the search for targets given by the given detection and target designation station (1C12), as well as for tracking the launched missiles. Upon detection of the enemy and after completion of all calculations, the data was sent to the launchers, which were deployed in the specified sector and began to "follow". As soon as the enemy entered the affected area, the launched missiles of the Krug air defense missile launcher were launched (photo above).
Released missiles captured the rays of the accompanying antennas, which corrected the trajectory, and also transmitted data for cocking the fuse and other commands.
3M8 anti-aircraft guided missile
As already mentioned, the development of two missiles simultaneously, 3M8 and 3M10, was carried out, the most successful of them was the 3M8 SAM.
It was created according to the aerodynamic scheme "rotary wing" due to the unstable operation of power plants. The design of the rocket was two steps:
- Marching, with an air jet engine running on kerosene fuel.
- Starting, with four self-detachable solid fuel boosters.
The warhead of the high-explosive action of SAMs was placed in the deepened central body of the air intake, and had a mass of 150 kg. There was also an air battery with a balloon and a homing head. Undermining was carried out by means of a radio fuse 50 meters to the target. The total mass of the rocket is 2.4 thousand kg. This missile was used in all complexes of this series, including the Krug-M air defense system.
Missile launcher
The 2P24 launcher performed several tasks at once - it transported missiles to the place of combat duty, guided and launched missiles at targets that were tracked or discovered. At the same time, she could transport two completely ready to defeat the enemy missiles. During start-up, the machine’s calculation was “hidden” inside the control system.
Missiles were located on an arrow equipped with hydraulic cylinders, responsible for changing the angle of departure. The arrow, however, was part of the support beam, which, with the help of cylindrical hinges, was fastened to the installation itself. During transportation, missiles were reinforced with additional supports, which were also located on the boom.
Support Technique
For automated fire control was responsible for the reception of target designation "Crab-1". She controlled the C75 / 60 mobile missile systems, was able to detect and escort at least 10 targets at a distance of 15 to 160 km from the standing position. Processing the coordinates of the targets and the issuance of data for guidance missiles took 32 seconds. The accuracy of the calculations was 90%.
"Crab-1" was part of the complex and its modifications, including in the Krug-M1 air defense system, but due to a 60% reduction in the firepower of units, this target designation booth was replaced with the Polyana D-1 model. Replacement occurred in 1981.
The new combat unit was distinguished by the ability to simultaneously support 62 units of air equipment, as well as the number of simultaneously processed targets, which increased to 16. This machine was the first to realize an automatic system for coordinating the actions of units within the complex. Due to this, the number of destroyed facilities increased by 20% while reducing ammunition consumption by almost 5 times.
Technical characteristics of the complex
After analyzing the data of all the machines that make up the complex, we can conclude regarding the combat effective anti-aircraft missile system circle:
- The maximum speed is 50 km.
- Cruising range of the complex (movement without refueling) - 300 km.
- Response time - less than one minute.
- Deployment of air defense systems - less than 5 minutes.
- The range of hitting the target is from 11 to 43 km, the height is 3-23.5 km.
- The flight speed of the affected objects is not more than 800 m / s.
However, it is impossible to provide accurate data regarding the combat effectiveness of the Krug SAM system. The combat use of technology is a secret even after so many years. It is known that the complexes were used during the Vietnam War, as well as in improving the Barlev’s air line in Egypt.
Model Modifications
The improvement of the complex was carried out mainly in the direction of reducing the "dead zone". As a result, modifications appeared:
- in 1967 - “Circle-A” with a minimum height of target destruction of 250 meters;
- in 1971 - Krug-M with a range of up to 50 km and a height of 24.5 km.
- in 1974 - Krug-M1, which had a reduced near border of 6–7 km and a minimum height of 150 meters.
In 2015, the jubilee medal “50 years of the Krug Circle” was issued, which indicates the relevance of the complex even after half a century, as well as the high merit of its developers to the homeland. Now all models are in storage.