By the mid-1970s, the Leningrad Kirov Plant (LKZ) tank design bureau (now under Nikolai Popov after Zhozef Kotin's retirement) was completing work on a turbine powered challenger to the Kharkov T-64 as the Obiekt 219. This was accepted for production as the T-80 tank in 1976; the Kharkov bureau's improved T-64B appeared at this time as well. The T-80 was soon followed by an improved type with additional turret armor, the T-80B in 1978.
The Uralvagon KB undertook a separate effort to bring the T-72 up to T-80B standards, at least in regards to armor protection. A new armor package was added to the turret front of this design, this early prototype was designated Obiekt 182. The new armor raised the vehicle weight by 3 tons, mandating an uprated diesel engine, the V-84.
This new version entered production in 1985 as the T-72B Olkha (Obiekt 184) and T-72B1. This version introduced many small changes into the T-72 family, such as the substitution of new road-wheels with six indentations for the earlier pattern with eight indentations. The initial production batches had the System 902A smoke dischargers mounted on the turret front like the T-72A, but they soon were shifted over to the turret sides for reasons that soon become apparent.
The much thicker turret frontal armor of the T-72B amd T-72B1 led to the unofficial US Army nickname "Super Dolly Parton" when it was first seen in 1986. The turret armor on the T-72B was the thickest and most effective ever mounted on a Soviet tank, surpassing even the T-80B. The primary aim of the new armor package was to defeat antitank missiles; thus it was tailored to defend best against HEAT warheads. It is the equivalent of 520 millimeter thick when faced by APFSDS kinetic energy penetrators, but an impressive 950 millimeters thick when attacked by HEAT shaped charge projectiles.
These performance figures and characteristics are similar to those made possible by the "bra" armor developed by the Nil Stali at this time for the T-55/T-62 upgrade program; it is possible that the T-72B's armor was based on the same configuration, but integral to the turret casting rather than as an applique.
Until the late 1980s, the T-72 tank was not capable of firing tube-launched antitank guided projectiles like the 9M112 Kobra fired by the T-64B and T-80. This was probably part of the effort to constrain the cost of the T-72. However, in the late 1980s, a new generation laser guided tank projectile family was developed to upgrade the T-55, T-62 as well as the T-72 and T-80.
The basic element of this system is the 1K13 laser designator sight. This device is mounted over the gunner's station in lieu of the normal sight. The system selected for the T-72 is designated 9K120 Svir (the similar round on the T-80U is code-named Refleks). The projectile itself is called 9M119, and the entire ammunition round is called 3UBK14.
It is a two-piece round and is stowed in the autoloader like any other type of ammunition. The new projectile considerably extends the range of the T-72, out to 5,000 meters. The Svir has an advanced warhead to permit penetration of advanced tank armor; it is claimed to be capable of penetrating the M-1A1 Abrams armor. The stated performance of the 4.2 kilograms shaped charge warhead is 700 millimeters penetration.
The laser guidance technique used with this projectile is of the beam-riding variety, not semiactive homing as is used with laser guided artillery projectiles. The 1K13 emits a laser beam that is optically rotated to form a narrow "funnel." The Svir missile automatically drops a small cover over the base of the projectile, which protects the optical port during the gun firing. The optical port senses the laser emissions. The laser signal is frequency modulated so that signal is varied from quadrant to quadrant. By monitoring the frequency, the missile's guidance system steers the Svir using small fins on the nose so that it remains in the center of the beam.
The propellant casing for the Svir is much smaller than the normal Zh40 because it was found that when a normal casing was used, it kicked up so much dust in front of the tank that it interfered with the laser signal. (On the earlier Kobra missile, the projectile had to be fired with the gun in elevation due to this problem.) The Svir fits into the ammunition cassette like any other round.
Usually only four to six Svir are carried. This is due to the high cost of each round, about $45,000 on the export market. To put this in perspective, 30 rounds of Svir ammunition are equivalent in cost to an entire T-72 tank. As a result, the Svir is intended for specialized missions. Its main mission is to defend the tank against long-range antitank missile platforms. This would include ground-based missile-firing tank destroyers, as well as antitank helicopters fitted with antitank missiles.
The 9K120 Svir system was first mounted on the T-72B tank. The version without the Svir system is designated T-72B1. With the exception of the Svir fire controls, the T-72B and T-72B1 are otherwise identical.
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