Close-in air defense (AD) systems play special role among field air defense weapons. Their primary task is to provide air defense of motorized and tank units and subunits in maneuvering combat and on the march by delivering fire on the move. Besides, practical close-in fighting requires that the systems be outfitted with effective AD guns capable of engaging both air and ground targets. The most successful type of these weapon systems is Russia’s famous Shilka self-propelled AD gun mount developed in the early 1960s and designed to fight primarily tactical aircraft and helicopters. The advent of tactical precision-guided weapons (PGW) called for the introduction of a missile channel to fight aircraft and helicopters before they could fire PGW. As a consequence, the renowned Tunguska AD gun-missile system was developed by the Tula Instrument Design Bureau and built in the 1980s.

The intense development of air attack weapons has changed the approach to the modernization of this class of AD weapons. According to experts, the modernization potentialities of such systems as the Shilka and Tunguska have not yet been exhausted and optimal updating can considerably extend their service life, while their combat effectiveness canl satisfy the present-day requirements.

The principal lines of modernization of these systems are described below.

ZSU-23-4 Shilka Self-Propelled Air Defense Gun Mount

The modernization seeks for state-of-the-art design and technologies to update the self-propelled (SP) air defense gun mounts and make them effective in heavy electronic countermeasures (ECM) environments, in adverse weather and dust-laden conditions, in any season and at any time of day or night. The modernization envisages:

1. Integration of the modernized Shilka gun mounts into a unified army information system of air target reconnaissance and designation by organically assigning a mobile air target reconnaissance and control post (MRCP), Sborka, to the battery as its command post (BCP).

2. Improvement of the gun mount’s main part—the RPK-2 radar-computer complex (85 percent of the equipment accommodated in the turret) and creation of a new complex, the RPK-2U.

The radar has been virtually replaced by a new one, operating on the same frequency band but based on solid-state components: all units and systems of the radar have been subjected to modernization and the radar equipment is accommodated in five cabinets (instead of seven). The RPK-2U complex incorporates:

• digital computer system (DCS) which jointly with the radar makes up a fire control radar system (base system);

• television-aided sight and laser rangefinder which together with the radar and digital computer system form an optical-radar fire control system (ORFCS) operating in the passive mode both day and night (moonlight at a quarter of the moon);

• equipment, including:

(a) data receiving/transmitting (DRT) equipment for the gun mount to exchange information with the Sborka battery command post via a telecoded communication channel for reception of external target designation signals and operational control of the Shilka battery engaging a target by one, two, three and more gun mounts;

(b) digital-to-analog and analog-to-digital converters;

(c) trainer for radar operators;

(d) built-in equipment for check and adjustment of the RPK-2U complex low-frequency automatics and turret laying drives (2E2) in static and dynamic conditions;

(e) commander’s guidance unit (CGU).

3. Replacement of a number of systems, units and assemblies by up-to-date ones boasting higher technical and operating characteristics.

4. Updating of the base tracked vehicle and crew life support system.

The fire control radar system has been modified with the aim to:

• extend the air situation information field by integrating the gun mount into the unified field AD system;

• reduce the time of information processing in the fire control system (dead time);

• redistribute regular and random errors and pass bands of the follow-up systems and groups of the radar- computer complex systems;

• change the principle of introducing corrections for the angles of tilt and turn of the mount on the move;

• change the principle of error determination in the generation of total laying angles of the automatic guns;

• introduce and automatically account for meteorological data, corrections for changes in the muzzle velocity due to barrel bore wear, corrections in orientation and others (all refer to know-how);

• change the method of processing secondary information;

• modify some existing modes of battle performance.

The following innovations have been introduced:

• modes of operation to handle low-flying targets in heavy ECM environments (by the stored rate of range variation, stored target coordinates received from the digital computer system, moving target indication (MTI) by radar angular coordinates;

• automated control of the gun mount battle performance from a higher command post (HCP);

• built-in check of the electronic equipment;

• mode of radar operators’ training.

The above innovations have made it possible to:

• cosiderably enhance the air target search potential and acquisition probability;

• improve the radar immunity to passive jamming (with the introduction of angular automation channel protection and modernization of the MTI system range channel), active range deception jamming and tracking a jammer by angular coordinates (with the introduction of modes of tracking by the stored rate of target range variation and its inertial range and angle-aided tracking by signals from the digital computer system);

• provide the security of operation in heavy ECM environments (with the introduction of the optical-radar system);

• improve the precision characteristics of the follow-up systems and groups of the radar-computer complex systems;

• reduce the surveillance time of the fire control system.

The implementation of the above modifications has enhanced the effectiveness of fighting high-speed (up to 500 m/s) and small targets maneuvering at altitudes down to 25 m (0 m with the introduction of the ORS) rather than 100 m.

The air target (aircraft, helicopter) kill probability during one pass of the engagement zone at an ammunition expenditure of up to 300 rounds per gun mount constitutes 0.3 to 0.74 (rather than 0.07 to 0.12) and depends on the organization of control over the combat activity of the battery gun mounts from the higher command post and engagement of the target by one, two, three and more mounts. In addition to better technical characteristics, the operating characteristics have been also improved by providing:

• prompt functional check of the radar-computer complex and its components;

• means to upgrade training and practice of radar operators in handling air targets in heavy ECM environments without aircraft flights (up to five targets with simulation of operation under conditions of passive and noise jamming);

• better controllability and maneuverability of the tracked vehicle and reduced labor content required to maintain and operate the vehicle;

• higher reliability of starting the traction engine;

• better habitability conditions.

The service life of a modernized gun mount after the overhaul of non-modernized systems, units and assemblies has been extended, with spare parts being supplied.

The modernization of the Shilka SP gun mount changes the latter into a modern AD system which fits readily into training, repair and operating structures of clients and can provide cover of stationary installations, tank and motorized columns on the march in adverse weather and dust-laden conditions, in any season and at any time of day or night where other systems outfitted with optical guidance and control systems prove ineffective.

Compared to the Tunguska-M, the Tunguska-M1 system ensures:

• automatic guidance of AD missiles (with manual correction for minor guidance deviations);

• automatic exchange of information with the battery command post (for higher efficiency of battery activity);

• batter immunity of the missile guidance channel (engagement of targets using optical decoys);

• engagement of small targets (cruise missiles of the ALCM type) owing to the use of a radar proximity target sensor (PTS) with circular radiation pattern;

• increase of the engagement zone within a range of 8 to 10 km.

Overall, the combat effectiveness of the Tunguska-M1 system in ECM environments is 1.3 to 1.5 times higher than that of the Tunguska-M system.

As compared to the 9M311 air defense missile, the 9M311-1M is noted for:

• installation of a radar proximity target sensor in place of the 8-beam laser one;

• installation of a pulsed light on the sustainer in place of the flare;

• increased operating time of the missile components which has allowed the firing range to be extended from 8 to 10 km.

The modernization package for the series-produced Tunguska-M system includes:

1. Introduction of reception and automatically controlled external target designation equipment in the SP mount. The equipment is interfaced with the battery command post over a radio channel which allows automatic distribution of targets among the battery SP mounts from the Ranzhir battery command post and considerably enhances the system combat effectiveness to repel mass attacks.

2. Introduction of a relief circuit to significantly facilitate the gunner’s work in optical tracking of a moving air target as if it were a stationary one. This considerably reduces tracking errors, which is essential for engagement of a target by a missile as in this case the miss value should not exceed 5 m.

3. Improvement of the coordinate determination equipment due to the application of a new type missile outfitted with a pulsed light in addition to the source of continuous light. This innovation significantly enhances the immunity of the equipment to optical decoys and the kill probability of targets using optical decoys. The employment of the new missile extends the target engagement range up to 10,000 m.

4. Modified system for measurement of tilt, gradient and course angles to allow an appreciable reduction in the perturbing action on gyros which occurs during movement of the SP mount, reduce errors in measurement of tilt and course angles of the SP mount, enhance the automatic gun fire control loop stability and, consequently, the kill probability.

The Ulyanovsk Mechanical Plant, the leading producer of renowned and advanced close-in and medium-range air defense weapons, offers modernized versions of the Shilka and Tunguska-M systems.

These are our offers for your consideration. Should you accept them, you will acquire highly effective air defense systems to ensure your country’s national security.

For the first time, a combination, in one vehicle, of two weapons systems (missiles and guns) with a common radar-computer suite has been implemented in the Tunguska air defense gun-missile system. The system has received a number of upgrades, and its latest modification, designated the Tunguska-M1, features the performance characteristics which far outweigh those of its predecessors.

The Tunguska-M1 system includes:

• six 2S6M1 self-propelled air defense mounts (combat vehicles);

• six transporter-loaders;

• group SPTA set transporter intended to provide six combat vehicles with spare parts;

• electronic equipment routine repair and maintenance vehicle;

• mechanical and hydraulic systems maintenance vehicle;

• wheeled and tracked chassis repair and maintenance vehicle;

• missile testing and maintenance vehicle.

The 2S6M1 self-propelled mount (SPM) is designed to provide air defense for motorized infantry and armor units in all types of military operations and also to protect various installations from air attacks. It is highly effective against low-flying surprise air targets, including hovering helicopters, and is capable of engaging targets before they are within the effective range of their weapons.

The 2S6M1 SPM is basically a lightly armored tracked vehicle carrying a rotary turret. An armored hull protects the vehicle crew and equipment from small arms fire and shell splinters.

The vehicle chassis has a high degree of structural commonality with tracked vehicles of intermediate weight category. The hydromechanical transmission, hydropneumatic suspension and variable ground clearance ensure the vehicle's high cross-country ability, agility and smooth run on any type of terrain, making it possible to deliver fire on the move without reducing the speed. The hull accommodates the driver's compartment; engine; power transmission; electrical equipment; power supply system; course, pitch and roll angle gyroscopic equipment; turret traverse hydraulic drive; internal communications system; life support equipment; vision devices; and fire fighting equipment.

Mounted on either side of the turret are tipping units, fitted with automatic cannons and missile launchers. The front of the turret carries a tracking radar antenna pedestal and the rear, a target detection and designation radar antenna pedestal. The turret interior accommodates three crew members (commander, operator and gunner); equipment of the radar and digital computer systems; electronic equipment of the pitch, roll and course angle measurement system; weapons elevation hydraulic drive; optical sight complete with the laying and stabilization system; missile coordinates discrimination unit and missile control command coder; internal and external communications equipment; navigation equipment; NBC detection system; ventilation and air-conditioning system; ammunition feed system; and ammunition load.

The radar system includes a target detection and designation radar, ground radar interrogator and a tracking radar. The radar system detects, identifies and tracks targets, determines their dynamic parameters and sends them to the digital computer which computes the control and firing commands for the weapons and the guidance commands for the missile.

The digital computer is designed to generate control and stabilization commands for the weapons systems, optics and radars, as well as to check the SPM systems for functioning. The computer stabilizes the line of sight and the line of elevation, generates missile guidance commands and computes the time of impact. While generating the weapons control commands, the computer allows for weather conditions and muzzle velocity, and while performing the system's scheduled checks, it runs a self test, analyzes the missile control circuits and carries out an overall SPM checkout.

The optical sight, weapons laying and stabilization system, and the coordinates discrimination equipment serve to detect and track targets over an optical channel, determine dynamic parameters of the tracked target and of the fired missile, and send this information to the onboard computer. The coder is designed to convert missile guidance and control commands to coded pulse trains and furnish them to the radar for subsequent transmission to the missile over a radio link.

In motion, the vehicle's pitch, roll and course angle measurement system is activated. The optical, radar and weapons systems are stabilized on the basis of the data generated by the measurement system. The hydraulic laying drives are designed to turn the turret in the horizontal plane and operate cannons and missile launch guides in the vertical plane.

The navigation equipment continually generates vehicle coordinates and sends them to the onboard computer.

The internal and external communications equipment provides reliable internal communication between crew members and with external parties. The vision devices are intended for battlefield surveillance at any time of day or night.

The ventilation and air-conditioning system maintains the temperature required for operation of electronic equipment and in the driver's compartment. The firefighting equipment serves to extinguish fires in the vehicle power plant compartment.

The NBC equipment allows the crew to continue with its mission while crossing contaminated areas and enhances the vehicle survivability under nuclear attack.

The power supply system feeds the vehicle equipment with +27 V DC and 220 V 400 Hz three-phase AC voltages.

The vehicle belt-fed cannons fire a 30mm unified round. The twin barrel cannon pattern provides for a rate of fire of 5,000 rds/min. The evaporation-type liquid cooling system makes the maintenance of the cannons easier, reduces their overall weight and increases the consistency of fire.

A surface-to-air missile (SAM) is held in a container-launcher. It is a bicaliber missile with a separable booster. The launch weight of the missile has been reduced by one half in comparison with the single-stage missiles having similar characteristics. The booster accelerates the missile to a speed thrice the velocity of sound. The sustainer stage has a smaller diameter. It maintains a high speed throughout the flight, making its optical guidance possible. The missile warhead is of a fragmentation rod type. It is characterized by a high length-to-diameter ratio and large weight. The missile is steered towards its target semiautomatically over radio command and optical links. A luminous flux emitted by a light source, carried by the missile, enters an optical detector which is mounted coaxially with the optical sight, where it is converted to an electrical signal proportional to the amount of missile deviation from the line of sight. The electrical signal is fed to the digital computer which generates correction commands. Then, the guidance commands are coded and sent to the missile as coded pulse trains via the target tracking radar.

The missile onboard equipment decodes the incoming pulse trains and generates commands for the control surface actuator. Consequently, the missile is guided precisely along the sight line. The missile impact and proximity fuzes ensure that the warhead is detonated either on impact or in the event of a near miss of up to 5 m.

In operational environments the SPM provides for:

• circular surveillance of air space;

• search for, detection and identification of air threats;

• air threat selection, lockon and tracking either via the radar or optical channel;

• engagement of air targets, including hovering helicopters and aircraft flying at a speed of up to 500 m/s, with missiles or cannons.

The Tunguska self-propelled air defense system can perform missions independently or as part of a unit, on the move or at a halt, at any time of day or night and inany weather. It is equally effective against moving and fixed ground and waterborne threats, as well as against paradropped targets.

Generally, in the enemy countermeasures environment, the fighting efficiency of the Tunguska-M1 system is 1.3 to 1.5 times more effective than the Tunguska-M.