Armor protection of the tanks of the second postwar generation T-64 (T-64A), Chieftain Mk5P and M60

© Andrei Tarasenko

Technical data on soviet 1-st post WW2 generation of tanks, Like T-54, T-55 and T-62 are well known and well described in literature. But what if Soviet “premium” tanks of 70-s era were engaged into real combat against western tanks in Europre.

This article provides description of "Object 432" (T-64) and T-64A tank combined protection (composite armor, anti radiation and chemical protection) in comparison to western designed tanks – “Chieftain” Mk5P and M60A1. Information on T-64 protection includes technical project (presentation) dated 1961 and technical drawings from various periods. Information on “Chieftain” Mk5P and M60A1 tanks is a result of study of captured tanks delivered to USSR in 1970s and beginning of 1980-s, published in technical reports of that period. The importance of information is the common testing criteria based on Soviet approach to tanks testing and protection design. This article contains mostly direct citations of facts and numbers published in reports with some comments.

T-64 was the first tank with complex combined protection. When designing the T-64 tank, designers paid equal attention to the issues of protection firepower and mobility. For its time, the "Object 432" (T-64) tank had the most powerful armor protection not only among Soviet tanks. No medium or heavy tank in the world could match T-64 the level of protection, including the British “Chieftain” tank, which was considered by some researchers as the one of most heavily protected Western block tank.

Also much attention was paid to the issue of protecting the crew from the penetrating radiation of an atomic explosion, which was one of the important requirements for the Soviet designers at that time.

The war to which the Soviet’s were preparing meant the widespread use of tactical nuclear weapons, the same was expected from opponents.

The complex combined protection of the "Object 432" consisted of:

• armored steel, which main purpose was protection against armor-piercing sub-caliber projectiles;

• anti shaped charge materials of large thicknesses, which are significantly inferior in strength to steel, which means that they are much lighter;

• special anti-radiation materials, providing, in combination with the rest of the elements, biological protection.

Technical requirements for "Object 432" armor protection level against armor piercing projectiles. Chief designers notes are visible on the paper,

crossing out 1000 m distance of protection, provided against M68 105 mm gun  rounds and replacing it with 500 m

"Object 432" hull and turret armor protection

Like all pioneers, the designers of the T-64, led by Alexander Morozov, had to face many difficulties in solving the task of equipping the tank with composite armor, an important role in the solution of which was played by VNII-100. Not all initial decisions proved to be correct, but there was no previous experience in design of composite armor in anywhere at that time.

In the initial technical project of the tank "Object 432" presented in 1961 [1] two versions of the filler were considered:

Cast turret with “ultraporcelain” inserts with the initial base thickness equal to 420 mm with and anti-cumulative protection equal to 450 mm;

Turret with “ultraporcelain” (ceramic) inserts.

Protection was provided in 70° frontal arc

Cast turret, consisting of a steel armor base with cavities, an aluminum anti-cumulative inserts were filled into turret cavities after casting a steel base. The total maximum LOS thickness was ~ 500- 620 mm. Turret anti shaped charge protection level equivalent to ~ 460 mm of steel.

"Object 432" turret with aluminum filler with LOS numbers of LOS thickness

Both versions of the towers gave more than one ton of weight saving compared to a homogeneous steel turret of equal protection. Due to delays in manufacture of “ultraporcelain”

ceramics and initial quality concerns an aluminum filler was chosen for the serial production of "Object 432" medium tank, which received T-64 designation.

About 1300 (1285) T-64 tanks were produced (1964-1969) and served in Soviet army up to the 1990-s when they were mostly scrapped according to arms limitations treaty in Europe.

During the accumulation of experience, a number of drawbacks of the turret were revealed, primarily related to its large dimensions of the thickness of the frontal areas which cramped tanks interior.

In 1967-1970 period a new the design of modernized T-64A turret with high hardness steel plates inserts was in production. Finally in 1971 initiall design with “ultraporcelain” was mastered and balls inserts were used up to the end of serial manufacture of T-64A and its modifications in 1987 (turret LOS – 450- 460 mm).

https://www.youtube.com/watch?v=R6Uda5F_fKg

Historical 1976 documentary about T-64A manufacture on Malyshev Plant in Kharkov. 94% off all processes were machine aided

T-64 front hull protection was also new for tank design. The front hull had composite protection consisting of 80 mm steel plate at 68 °  and 140 mm STB (glass fiber) plate with total thickness of 220 mm ( 587 mm LOS). Such armor was equivalent to 450 mm of steel against shape charge projectiles. Protection against kinetic energy projectiles was provided mainly by frontal steel plate, glass fiber also contributed about 40 mm of protection.  No supporting back plate was initially suggested.   

"Object 432" from 1961 technical project presentation with 80 steel  + 140 glass fiber front hull

Driver’s sights placement and front hull of the "Object 432"

The upper sides of the hull were made of 45 mm thick armor and had lapels - "cheekbones" located at an angle of 78 ° 30 to the vertical.

First variant of T-64 "Object 432" front hull design

First variant of T-64 "Object 432" used for target practice in 90-s

The use of fiberglass, also provided a reliable (with exceeded technical requirements) antiradiation protection. The absence in the technical design experience resulted in not ideal solution. Lack of back plate evidently decreased frontal hull survivability. The upper sides of the hull - "cheekbones" were also more vulnerable to shaped charge attacks.

The lack of back plate after the glass fiber layer shows a complicated search for the right technical solutions for creating the optimal three-layer armor.

T-64A "Object 434" drawing with “classical” 80 steel + 105 glass fiber + 20 steel front hull

After the solution of initial frontal hull design problems "Object 432" and all later produced variations, including T-72 and T-80 used same three-layer armor for a next decade.

Finally at the beginning of 70-s composite armor of soviet tanks provided reliable protection against shaped charge projectiles equivalent to 450 mm of homogenous armor for hull and turret. And against kinetic projectiles at the levels of 410 mm for turret and 305 mm for hull. Protection against 105mm APDS was penetrating 120 mm/60° at 2000 m was provided from 500 m.

The overall increase of weight of the tank over T-62 was only 2 metric tons.  

It should be noted that the layout of the driver compartment provides additional protection for the driver on the left and right by the front group of fuel tanks, which is produced last, and the left 4 battery packs. To further protect the sides of the hull from cumulative short-range weapons, flap-mounted aluminum anti shaped charge shields were installed on the sides of the tank, later replaced with solid rubber-metallic screens.

Explosive reactive armor

Soviet designers were pioneers not only in composite armor, but in the area of explosive reactive armor, locally known as dynamic armor.

The idea of reactive armor appeared on the basis of WW2 experience, first materials were published in 1946, following laboratory tests in 1949. Full scale testing of experimental hulls with ERA using 115-mm APFSDS and various shaped charge warhead commenced in 1968 with good results. The success of testing allowed recommending a new design of the hull front for installation on T-64A tank. But due to reasons not clear for now this works did not realized in production. It can be assumed that the existing armor protection level of T-64A tanks was adequate to the treats of 70-s. Another reason was a strong opposition of certain high rank military officials to the installation of explosives on tank external surfaces.     

Results of fire trials of experimental “object 775” hull in 1968

T-64 reactive armor designed in 1968

Installation of new ERA on T-64A tank could provide increase of protection against shaped charge projectiles at the level of 600 mm RHA with decrease of frontal hull weight. Protection level against  APDS and APFSDS remained on same or increased level as the hull with composite armor

Protection from weapons of mass destruction

In addition to composite armor, the key attention was paid to protection from the weapon of mass destruction. To protect the crew from penetrating radiation in the area where the crew workplaces were located and where the thickness of the armor protection was insufficient, a special anti-radiation lining and appliqué was installed. In addition, this lining provided some additional level of protection from splinters, breaking off from the armor during the shell impact.

On the T-64, an automatic collective defense system against WMD and chemical weapons system was installed. A powerful filter-ventilation unit provided overpressure inside the tank, which excludes the immission of contaminated air inside the tank. Therefore, the crew could overcome the contaminated areas without special protective equipment.

Biological protection of driver

The biological protection of the hull was determined by the protection of the driver, which, for better visibility, is located along the longitudinal axis of the tank, which made it possible to implement its local anti radiation protection. The main element of this protection was the 140 mm fiberglass plate of the upper front hull, which is supplemented with polyethylene lining placed on the sides of the roof, including the hatch cover, which is made of 45 mm thick steel. To ensure the necessary radiation protection when the tank is in the contaminated area hull bottom area in the driver's zone was equipped with a lead pad.

Biological protection of turret crew

Large arrays of armor in the front part of the turret allowed to use thin 20 to 10 mm anti radiation lining, which increased to 40 - 60 mm at turret sides and rear.

The roof of the tower is equipped with a rebound of 50 mm thickness. The lower part of the working places is protected by the falsifications of the polyethylene layer 30 mm thick on the inner cylindrical surface of the felling.

Overall protection against penetrating radiation from a nuclear explosion of an average caliber (30 KT) was decreased 15 times.

Protection of turret with anti radiation lining

Fuel tanks also provided protection to the driver from sides

This ensured the safe location of the crew in a tank at a distance of 900- 1000 m from the epicenter of the explosion with an allowable dose of 200 roentgen per hour.

The protection also provides 18-time decrease of radiation in the contaminated area, which allowed the crew to be in the area of radioactive contamination at a level of 300 roentgen per hour for 12 hours, at an admissible dose of 200 roentgens.

Protection from incendiary weapon

Attention was also paid to the protection from incendiary weapon such as napalm, widely used in the West. First of all it concerned rollers of the tank. The tank's rollers had internal cushioning. The main part of the rubber was covered with an aluminum cap. Thus, the tank could cross the fire zone without threat of being left without rubber bandages.

The use of an ejection cooling system with a sealed box under the roof of the motor compartament reliably protected the engine and transmission assemblies from the penetration of incendiary mixtures.

Comparison of armor protection of T-64 with the "Chiftein" Mk5P

In the early 1980s, the USSR received "Chiftein Mk5P" tank [2] which was tested in conditions similar to that of domestic tanks, according to the methods developed by domestic specialized organizations. Tank was captured by Iraqi troops from Iranian army during initial phase of Iraq-Iran war. Measurements of thicknesses and angles of inclination of armored elements, research of chemical composition and mechanical properties of cast and rolled armor material were carried out.

Results of study

The design of the "Chieftain" is made in accordance with the concept adopted in England in 1944, according to which preference was given to factors of protection and firepower. "Chieftain" is made according to the classical layout scheme. According to the geometric diagram of the hull and turret, as well as the design of a number of units and chassis units, the “Chieftain” tank has a succession with the tank of the first post-war generation “Centurion”.

The same marks of steel armor were used for hull and the turret protection, which were used earlier for the “Centurion” tank.

Both tanks have large dimensions and weight. The weight of the "Chieftain" Mk5P is 54.8 tons. The weight of the hull and the turret armor is 29 tons, which is 53% of the total mass of the tank.

The hull is made welded using homogeneous cast and rolled armor of medium hardness. The cast upper hull detail has a complex streamlined geometric shape.

The lower frontal part is made of rolled armor 76 mm thick with an angle of 45°. The main sides of the hull are made of rolled armor 38 mm thick with an inclination angle of 10 °.

In the aft part of the over tracks shelves in the zone of the motor-transmission compartment there are compartments in which the rubber-fabric fuel tanks are placed. The walls of the compartments are made of rolled steel armor with a thickness of 13 mm.

Along hull entire length on both sides of the tank at a distance of 800 mm from the main hull anti-cumulative screens (four sections) are installed. They are made of aluminum alloy 10 mm thick. The turret roof is made of rolled armor and 35 mm thick.

Let’s  examine the geometric scheme of armor protection (figure).

Scheme for armor protection of the “Chieftain” Mk5P tank on the basis of a study of the sample received by the USSR

Analyzing the tank protection scheme (see the figure) together with the data (table below) it can be concluded that the tank has no anti shaped charge protection of hull and turret, since the horizontal thicknesses of homogenous armor do not exceed 250 mm.

However, it should be noted that a four-section aluminum side-screen with a thickness of 10 mm is installed on the hull sides. The presence of such screens allows, taking into account the shielding effect of the running gear parts (rollers and suspension hoods), to provide protection of the lower side from the shaped-charge in the course angles of ± 25-30 °.

Conclusions:

It turned out that the protection level of frontal projection of turret and hull provides protection from the 125 mm APFSDS (3BM-9, 3BM-15) from a distance of more than 3000 m (tank can be penetrated from distance up to 3000 m).

All types of shaped charge rounds (HEAT) can penetrate "Chieftain Mk5P" at all realistic ranges of fire.

115 mm APFSDS used for T-62 and T-64 guns can defeat “Chieftain’s” armor at a range of 1600 m. The studied example of the "Chieftain Mk5P" was manufactured in 1974 at the state-owned Royal Ordnance Factories in Leeds.

Protection of the upper frontal part of the hull and the frontal part of the turret provides protection:

from 100-mm caliber and armor-piercing sub-caliber shells of the T-54/55 tank at a distance of 500 m;

from 115-mm APFSDS of the T-62 and T-64 tank at a range of 1600 m.

protection from 125-mm APFSDS of T-64A (T-72, T-80)tanks is not provided. The tank can be penetrated by these projectiles from a distance of more than 3,000 m.

The rest of the projections of the hull and the turret have a low level of protection. Rear parts of the hull and turret has anti-bullet and anti-fragmentation protection. The welded joints of the hull and tower parts are made with the use of mechanical processing of the edges and have small legs of welded joints made without a complete fusion. Such a design of welded joints has a low survivability in firing by armor-piercing sub-caliber and high-explosive fragmentation projectiles.

Characteristics of sub-caliber projectiles for the D-81 gun

Features of the “Chieftain” Mk5P turret are:

a narrow embrasure with a width of 255 mm, which makes it possible to exclude the armored muzzle of the gun;

the fastening of the cannon (trunnion) in the tide protruding in the frontal part of the tower, which significantly reduces the weakened zone of the frontal projection of the tower;

the presence of compartments outside of main armor of the fighting compartment in the aft part of the turret, in which additional equipment is located.

Distance D and velocity V of penetration

* Considered with hull and the turret safe maneuvering zones for the hull ± 20 °, and for the turret ± 35 °;

** including the casing of the support rollers to the body;

** at nominal speed.

Comparison of armor protection T-64 with the tank M60

In the early 1970s, the USSR received a sample of the M60A1 tank, captured from IDF. The tank was subjected to thorough research in all areas which were published in soviet specialized literature [3].

The armored design of the American M-60A1 tank and its subsequent modifications is different in that both the body and the tower are made of a homogeneous cast steel of a transverse thickness.

The hull is made of solid cast steel with welded bottom. The cast part of the bottom has a thickness of 40 mm, and the welded parts under the combat under the engine-transmission compartments are, made of rolled steel 20 mm thick and 920 mm wide. The sheets are bent in the middle 1.5 ° from the horizontal axis and together with the sides form a U-shaped configuration of the bottom.

The sides of the hull have a complex configuration, which allows to arrange individual parts at constructible angles of inclination up to 50° from the vertical axis. The thickness of the side variable - from 40 to 60 mm, decreasing to the bottom. The vertical part of the hull, 55 mm thick, occupies less than a third of the total area of ​​the side.

The upper front hull detail has the same thickness ( 120 mm) over the whole surface at a constructible angle of 64 °; the thickness of the lower frontal detail is variable in height (150- 110 mm), decreasing to the bottom at a constructible angle of 55 °.

The front roof of the hull has a thickness of 50 mm and an inclination angle to the horizontal axis of 6°30. Drivers hatch and driver periscopes are taken out onto roof, which decreases weaken zones of hull front. The rear hull above the engine-transmission compartment has a thickness of 20 mm.

The turret of the tank is a cast with variable thickness with different structural angles in height and contour and with a characteristic elongated aft niche. The frontal sections have a thickness of 180- 150 mm, structural angles of 30-22 °.

The sides of the turret are not symmetrical: the left side is 85- 115 mm thick at angles of 36-13 °, the right side has a lug under the commander's turret, and the side thickness is 95- 112 mm at angles of 25-13 °.

The front roof of the turret has a thickness of 45 mm at an angle of inclination to the horizontal axis of 17 ° 30, the main roof - 35 mm.

Turret back has a thickness of 60 mm at a design angle of 10. Armor mask-cradle and commander's turret are also cast. The thickness of the walls and the roof of the commander's turret is 30 mm. The armor mask-cradle has a thickening to the center.

The armored protection of the M-60A1 tank is highly differentiated. The use of cast armor made it possible to use a variable thickness in the lower frontal hull, on the sides and rear of the hull, and also on the turret - along the height and along the contour.

The frontal projections of the tank are protected from its own 105-mm gun projectiles from the real battle distances: the upper front sheet of the hull is from a distance of 1000 m; the front sections of the tower - when firing at point-blank.

From the armor-piercing 100, 122 and 115 mm projectiles of tank guns, the frontal projections of the tank are protected as follows:

Turret - at the course angles of firing ± 30 ° - from a distance of more than 3000 m, at 0 ° - when firing at point-blank;

Upper front hull detail - when firing at point-blank with a 100 mm shell; From a distance of 1000 m - from 122 and 115-mm shells.

Protection of the turret at a course angle of firing 0 ° is ensured at a relatively small thickness, mainly due to large angles of slew – 55-60 °. At the course angles of firing ± 30 ° the protection of the turret decreases very sharply and it can be penetrated by armor-piercing-subcaliber projectiles from a distance of more than 3000 m.

The upper front hull detail is protected due to the thickness of the steel plate and a large structural angle of 64 °. The level of protection of the lower frontal sheet of the body is somewhat lower than that of the upper one, but its protection is much higher than that of existing serial tanks.

Scheme of armor protection of the tank M60A1 [4]

* - The positions in the figure are indicated in parentheses

** - turret front angles of slew 55 - 60 °

The sides of the hull provide protection against a 105 mm armor-piercing-sub-caliber rounds from a distance of 1000 m only at the course angles of firing ± 15 °.

The developed rear part of turret increases the internal volume and gives turret a prolongated form, which determines the significant overlapping of the turret rear of the engine-transmission compartment and the appearance of "shot trap" of large dimensions.

This can lead to a significant weakening of protection from high-explosive fragmentation and armor-piercing fusible projectiles. M-60A1 tank is not protected from the existing cumulative rounds at any range.]

Unlike the West German tank "Leopard-1 A4" and the English "Chieftain", there are no even anti-cumulative screens along the sides of the hull.

A cast cradle mask attached to the gun barrel creates an additional protection for the turret at the weakened point of under the embrasure, but this zone is still a weakened place. Mask-cradle can protect only from splinters and bullets. A weakened place of protection is also the zone of the joint between the tower and the hull, where the possibility of flying fragments can cause the tower to get stuck. A significant weakening of armor protection is created by the commander's turret, protected only from a 20 mm rounds.

The scheme of weakened zones of armored protection of the tank M-60A1

1 - the joint of the hull and tower, 2 - the commander's turret, 3 - the cannon's embrasure, 4 - the blinds, 5 - the hatches, 6 - the embrasure of the range finder, 7 - driver's viewing devices

Comparison of side and frontal projection of T-64 and M60 tanks

Relatively large area of ​​the frontal projection (in comparison with other foreign tanks) indirectly weakens the defense, increasing the probability of hitting the tank. This was specially important criteria in the times when most tanks had no laser rangefinder systems (1960-1970-s). An internal volume of the tank M-60A1 ( 18 m3) allows to place the internal equipment freely and provide the maximum comfort for the crew. With an overall weight of 49.6 tons, the weight of the armor protection is 27 tons. Overall, the M-60A1 tank has a relatively low level of protection. It should be noted that the zones weakened by the protection on the M-60A1 tank (figure) are significantly reduced due to the removal of all driver hatch holes and observation instruments to horizontal sections or to sections with large structural angles of protection.

Conclusions

Hull and turret of the "Chieftain" has no protection against shaped charge projectiles, and can be hit with cumulative ammunition both in the frontal and in the side projection. Since the horizontal thicknesses (LOS) of turret armor does not exceed 250 mm the tank can be penetrated hby 125 mm APFSDS from a distance of 3000 m and 115 mm APFSDS from a distance of 1600 m.

The weight of the tank "Chiften" Mk5R is 54.8 tons. The weight of the protection is 29 tons, which is 53% of the total tank weight.

Hull and turret of the M60A1 tank also do not have anti-cumulative protection. Only the most secure frontal projection can not be penetrated by an armor-piercing sub-caliber projectile of the 105-mm cannon of this tank from a range of about 1 km when firing at a course angle of ± 15 °.

At the course angles of firing ± 30-35° the protection of the turret decreases very sharply and it can be penetrated by armor-piercing-subcaliber projectiles (100- 125 mm) from a distance of more than 3000 m.

The weight of the reservation M60A1 is 27 tons with a weight of 49.6 tons.

Soviet approach to armor protection required ± 35° area of safe maneuvering zone for turret, which largely exceeds the parameters for both "Chieftain" and M60A1.

Protection against WMD of T-64 tanks also much superior to western tanks of that time. 

Despite the fact that the "Chieftain" has a large overall mass, its armor protection does not exceed M60A1, but is inferior to it in some aspects.

Also this article concerns only protection against armor-piercing-subcaliber projectiles, as both western tanks can be easily penetrated by all existing HEAT rounds of 60-70 period at any ranges.

It is worth noting that despite the conservative design approach for the "Chieftain" does not cancel British innovative approach to tanks design in general. Since the second half of the 60-s the development of a new type of armor, called " Burlington" started in UK .

Judging from now uncovered reports available in British archives western designers were not aware of a fact, that T-64 tank (and it’s modifications) had composite armor.

It is evident from 1978 report «Technical Assessment of the Soviet T-64 medium tank».

Page from the report «A Technical Assessment of the Soviet T-64 medium tank»

Starting from the first half of the 1980s, this type of armor will be installed on NATO and US tanks, providing them with high rates of anti-cumulative resistance and protection against APFSDS.

Almost in that period of time in USSR works on so called active armor barriers started, which used common features as in British “ Burlington” design – use of energy of attacking projectile to defeat it. There were two approaches in this area – one headed by research institute of steel (NII Stali) and another headed by hydrodynamics laboratory of Siberian department of academy of Science of Soviet Union. They were both realized in a new generation of Soviet composite armor implemented in T-72B and T-80U and T-80UD tanks.

Overall in 60-s ERA Soviets were definitely leaders in armor protection, this situation shifted in the beginning of 80-s. But this is a theme fore another research.

Sources:

1. Medium tank “Object 432”. Calculation-explanatory note to the draft design. - Kharkov: Malyshev plant, 1961

2. Questions of defense technology. - 1983. - No. 5 (111)

3. Questions of defense technology. - 1976. - Issue 67

4. Armored forces herald. - 1980. - No. 4