Development of the Krug ZRK-SD air defense system started in 1957 by the Lyulev OKB design bureau. It was first displayed during a parade in Moscow in May 1965. The system started to be fielded in 1967 and became fully operational in 1969. It was used by the Soviet Army as a long-range SAM. The early version of the Krug entered service in 1965. The first operational deployment version, the Krug-A, entered service in 1967, with extensively modified versions, the Krug-M in 1971 and the Krug-M1 in 1974, which were developed to rectify problems discovered during army service. The upgraded version Krug-M was fielded in 1971 and the Krug-M1 in 1974. A target drone called 9M316M Virazh, developed from obsolete Krug missiles, was proposed for export in 1994. The 2K11 was briefly operated by the Soviet army during the war in Afghanistan in 1979 and 1980, but was withdrawn several months after the initial invasion. In 1997, it was reported that, between 1993 and 1996, some 27 fire units of Krug and 349 missiles had been sold to Armenia. Poland flight tested four missiles in September 2006 against P-15 Termit targets.
Description
Vehicles
The TEL vehicles are tracked based on a GM-123 chassis and carry two missiles each on an elevating turntable for up to 360-degree rotation and 70-degree elevation. The two primary versions of the missile in service are the 9M8M1 and 9M8M2 , both of which are believed to be known to the US DoD as SA-4B. The original 9M8 was first introduced into service in 1965 and followed by the upgraded 9M8M in 1967 before the 9M8M1 in 1971 and the 9M8M2 in 1973. The 9M8M2 actually has a lower maximum engagement altitude and shorter range in exchange for better performance in engaging aircraft close to the battery. Each battery typically consists of two 9M8M1 missiles and four 9M8M2 missiles as well as the following radars:
PRV-9 "Thin Skin" E-band height finding radar, in regiments or brigades command post
Only "Long Track" is mounted on a modified AT-T vehicle, TEL 2P24 and "Pat Hand" 1S32 are mounted on GM-123/ GM-124. "Thin Skin" is mounted on a truck. Batteries may also feature Ural 375D trucks 2T6 carrying spare missiles for reloading the launchers.
Missile
The missiles are launched with the aid of four solid fuel rocket motors inside boosters attached to the outside of the missile. Once they have burned and the missile is aloft, a liquid-fuelled ramjetsustainer engine is ignited. It reaches speeds of up to Mach 4 and has an effective range of 50–55 km depending upon the version. It carries a 135 kg fragmentation warhead. Possible engagement altitudes range from 100 m to 27 km. The 3M8 missile was designed and produced by NPO Novator. Optical tracking is possible for guidance in a heavy ECM environment.
Survivability and anti-jamming capabilities
The Krug had several features that improved the survivability of the radar against anti-radiation missiles. In PImode the system only briefly illuminated the target and the computer calculated it's prolonged path based on data received from early warning radars. After a longer passive period the main radar illuminated the calculated flight direction of the target for a few seconds and recalculate path of the target if necessary. As a result, the system emitted detectable signals only for a few seconds every few minutes, making it difficult to jam or launch an anti-radar missile against the Krug. The system was also able to track the target in full-passive automated PNSmode based on the data provided by "Long Track" mobile EWR via radio datalink. In this mode it was almost impossible to detect the Krug system until the moment of missile launch, because Krug did not emit radiation at all. In 3M mode the krug track on jamming signal emitting container. So the jamming signal that supposed to protect the aircraft made it to a target.
Structure of Krug missile system
SAM-regiment have two SAM-battalions, SAM-brigade have three SAM-battalions. In each headquarter, brigade, regiment and battalion, is one command battery. In each SAM-battalion have three SAM-batteries.
Self-propelled launch vehicle2P24 on GM-123 base, three in each SAM- battery
Rocket guidance station 1S32 on GM-124 base, one in each SAM- battery
Target detection station 1S12 on modified AT-T base, one in each command battery
Transporter-loader vehicle 2T6 on Ural truck base, one in each SAM- battery
