Tank protection is developed based on information about anti-tank weapons of the potential enemy, physics of interaction between those weapons and a tank's armour, and the conditions in which tanks are used and that they fight in. An analysis of anti-tank weapons is a necessary step towards designing tank armour. In the 1950s it became clear that further improvement of tank protection simply through improving the characteristics of steel alloys is impossible. This was primarily true when protecting the tanks from HEAT warheads. The idea to use fillers to protect from HEAT ammunition appeared during the Great Patriotic War, but was not developed until after its conclusion.
Work to improve anti-HEAT protection of both tanks already in production and those just being developed began in the 1950s. New conceptual ideas of active armour were also developed, but the fastest and less risky solution was the development of composite armour that could protect the tank from the most common HEAT warheads used by the potential enemy.
|Hull of Object 432, draft project, 1960.
|Turret of Object 432 compared with Object 430, draft project, 1960. This drawing shows one of the transitional designs where composite armour was not yet used.
- Cast steel armour with ultraporcelain inserts with 420 mm basis and 450 mm equivalent protection against HEAT.
- Cast turret with a steel frame, aluminium anti-HEAT layer (poured after the initial casting), external steel armour, and aluminium layer. The total maximum thickness of this turret would be 500 mm offering 460 mm equivalent protection against HEAT.
|Production T-64 turret with aluminium filler.
|Production T-64 turret with aluminium filler, cutaway. The turret guaranteed protection from 85 mm and 100 mm HEAT shells (equivalent to NATO 105 mm HEAT shells) and 100 mm flat-tipped AP at angles up to +/- 35 degrees.
"We had the task of correcting this drawback without increasing the distance between the turret rotation axis and the center of the hatch. The front of the turret therefore had to be reduced by almost 200 mm compared to the "steel-aluminium-steel" turret (from 600 to 410 mm). The decision to reduce the thickness of the turret armour while maintaining its resistance to shells was proposed by V.V. Ierusalimskiy. He proposed doing this by using high hardness steel inserts hardened with the differential isothermic process. This would give a very hard core and a comparatively softer and more flexible outer surface.
The result was quite decent, better than the experimental turrets with ceramic balls that VNII Transmash was working on. Their turrets were thicker than the turret with high hardness steel inserts. One drawback of this turret was the insufficient toughness of the weld seam between the retaining plate and foundation of the turret. It could be destroyed with a nonpenetrating hit from APCR shot.
These results led to a decision to begin producing a batch of turrets with high hardness steel inserts after the welds have been strengthened. However, there was an unsolvable issue. The batch of high hardness steel inserts produced for this task had insufficient impact malleability. When hit with shells, the steel inserts resulted in brittle damage and penetration."
|Cutaway of the turret with ceramic balls.
"As a result of trials conducted in 1967 by organization A-7701 (VNII Transmash), three turrets with an experimental ceramic filler were tested: K22, K23, and K24.
Based on the results of these trials, organization A-3530 in their letter #7852ss dated December 22nd, 1967, proposed to produce a trial batch of turrets with ceramic filler: 5 units for the 434 tank and 50 units for the T-64 tank.
I find it necessary to make the following notes regarding this proposal.
- Not a single turret out of K22, K23, and K24 had the weight required by the Chief Designer.Not a single turret has the required internal volume and turning radius.This data is absent from report #005105 on the trials of K22, K23, and K24 turrets dated October 20th, 1967.Measurements taken by unit 68054 show that the turrets are 200 kg overweight (given the height requirements for 548 mm + up to 6 mm as accepted for T-64 and 434 turrets).The turning radius of K22, K23, and K24 turrets is greater than the requirement by 10-20 mm according to our calculations. This does not permit one to judge the protection and resilience characteristics of turrets with a ceramic filler produced according to the dimensions and weight provided in the blueprints
- Despite the turrets being overweight, their resilience cannot be considered satisfactory. For instance, a hit from a 100 mm AP shell near belts I-II (shot #17) resulted in a 370 mm long tear in the lower section that moved the metal along the crack by 30-40 mm.
This kind of hit would disable the turret entirely.
Damage of this kind on turrets with aluminium filler or with high hardness steel inserts was not observed.
K22 and K23 had tearing and spalling of the outer layer of armour.
For example, after K23 was hit with a 100 mm shell, a chunk 300 by 300 by 120 mm was knocked off the turret. Such damage was not observed even on turrets with aluminium filler.
Trials of the K16/17 turret with ceramic filler at the Pavlograd proving grounds showed very low resilience when hit with 100 mm ammunition with a tungsten carbide penetrator fired from the D-10T gun (see report #28 dated December 25th, 1967). Out of 7 hits to all areas of the turret in the +/- 35 degree range with an impact velocity of 1400-1430 m/s 7 penetrations were made with an exit diameter of 70-80 mm. Penetrations were made in areas where the weight of the cutaway would be equivalent to that of the K23 and K24 turrets.
Penetration trials conducted by us show that protection from this type of armour piercing shot at a velocity of 1400-1450 m/s can be achieved using armour with aluminium filler, fiberglass, and high hardness steel inserts in the thicknesses used on T-64 and 434 hulls and turrets.
New domestic 100 and 122 mm subcaliber shells with a tungsten carbide core are analogous to 105 mm APDS shot used by NATO tanks, the M60A1 and Leopard. In our opinion, protection of the T-64 tank against 105 mm APDS must be achieved at a range up to 1000 m. Calculations and other data show that the British APDS shot penetrates up to 350 mm of rolled medium hardness armour at 1000 m (impact velocity 1360 m/s) at angles of up to 35 degrees. This impact velocity surpasses domestic subcaliber shot of the same type.
Based on the above, organization V-2652 considers the proposal to build 55 turrets with ceramic filler for T-64 and 434 tanks moved forward by the Malyshev factory and organization A-3530 to be premature, as it is not supported by a proportional amount of evidence from trials of similar turrets or samples of armour.
In our opinion, the following is necessary for turrets with ceramic filler:
- Determine whether or not they satisfy the requirement for protection when they meet the size and weight requirements set in the blueprints.
- Determine the level of protection from subcaliber shot with a tungsten carbide core, as when testing turret K16/17 the level of protection was very low.
- Conduct work to improve the resilience of turrets with ceramic filler when hit in the region of belts I-II with 100 mm shot.
The proposal to produce 55 turrets with ceramic filler can only be considered when all of the above issues are resolved with a positive result."
|70 mm ceramic ball filler from a T-64A turret.
- Keeping the structure robust and resilient despite the use of highly brittle materials.
- Protect the turret both from HEAT and kinetic penetrators, particularly subcaliber shot with a tungsten carbide core.
- Mass production of composite armour.
- Development of a ceramic filler that needed to match high protection requirements.
|Mass produced T-64A turret with a ceramic filler.
|Cutaway of the production T-64A turret.
"We were informed of a letter from director of organization V-2652 comrade A.T. Larin, in which he baselessly lists three drawbacks of Object 434 turrets with a ceramic filler. We have the following to say about this issue:
As it stands, the letter from organization 2652 contains not a single element of truth to it, and its goal is unclear."
- The K-23 turret with ceramic filler was produced in accordance with blueprint R.165-2012-10 produced by the Chief Designer and accepted by Military Representative #30 of the Ministry of Defense at the Heavy Machinebuilding factory. K-23 is equivalent in weight to the S-10 turret with steel inserts. The turning radius and height are within the range specified by the blueprint, regarding which there is a note on the measurement diagram.
- The resilience of the turret is quite satisfactory as noted by the trials commission, units 68054 and 52682-III (report of unit 68054 numbered #3438 and letter from unit 52682-6 #K/855668 dated January 12th, 1968).
- Only a different turret was fired upon with tungsten carbide ammunition at Pavlograd, and even then it was fired at from angles greater than 35 degrees.
|Belt IV of the turret with a ceramic filler.
- T-64A style turrets required new production lines to produce corundum spheres and baskets for installing them into casting molds.
- Processes for obtaining turrets with required resilience and robustness were never developed, as ceramic elements were subjected to changes as a result of being cast in molten steel, even with thermal isolation paste.