At the very end of the war, in February 1945, in the design bureau of plant No. 100, whose branch at that time was located in Leningrad, work began on the project of a new heavy tank, which was to become a development of the IS-6 project. By June, a detailed draft design of the future combat vehicle was ready, which received a new index - the IS-7. For its time, it was the most powerful tank and the heaviest among Soviet serial tanks, but this power remained unclaimed. Despite the fact that it was not adopted by the Soviet Army, many technical solutions first used on this combat vehicle were successfully implemented in the future on other serial tanks.
The heavy tank IS-7 was never mass-produced, which did not prevent it from becoming a fairly recognizable combat vehicle, primarily due to its spectacular and memorable appearance. Numerous computer games popular at the present time, in which this tank is present, also played a role. When you look at this multi-ton combat vehicle and its elegant contours of a massive tower, the word grace comes to mind, the IS-7 could be safely called a beautiful tank, just as much as this word was applied to heavy steel monsters designed to instill fear in the enemy on the battlefield.
Variants of prototypes of the IS-7
In total, in the second half of 1945, the design bureau of experimental plant No. 100, under the leadership of the famous designer Joseph Yakovlevich Kotin, prepared several versions of projects for a new heavy tank - objects 258, 259, 260 and 261. According to Vera Zakharova, an employee of the Museum of Armored Vehicles, for the development of Soviet heavy tanks were strongly influenced by the discovery near Berlin in June 1945 of the blown up German monster - the Pz. Kpfw. Maus tank. Taking into account this find on June 11, 1945, in Leningrad, a draft of the tactical and technical requirements for a new Soviet heavy tank was developed.
Initially, it was planned to create a tank with a combat weight of 55 tons, with a maximum speed of 50 km / h, armed with a 122 mm BL-13 cannon with an initial projectile speed of 1000 m / s. At the same time, the frontal armor of the new tank had to withstand the hit of shells from the same gun. Already in June, the set of tactical and technical requirements was changed. The mass of the tank increased to 60 tons, the crew grew to 5 people. The armor was supposed to provide effective protection of the tank from hitting shells from a 128-mm cannon. As standard armament, not only a 122-mm gun was considered, but also a 130-mm cannon with ballistics from the B-13 naval cannon.
Work on a new heavy tank has already begun based on the latest tactical and technical requirements. In September-October 1945, the designers prepared four versions of the future tank: "Objects 258, 259, 260 and 261". They differed from each other mainly in power plants and the types of transmission used (electrical or mechanical). Ultimately, the choice fell on the Object 260 project, which was planned to be equipped with a pair of V-16 engines, an electric transmission and a powerful 130-mm C-26 cannon designed by TsAKB, installed in a cast flattened turret, which became a recognizable feature of all prototypes of the tank. IS-7. Despite its large mass, the tank was quite compact.
This preliminary design of the "Object 260" became the basis for the first version of the IS-7, which was built in metal. True, even then it became clear that the pair of B-16 engines had not been brought to fruition by the Soviet industry; tests and fine-tuning of such an engine in Leningrad demonstrated its complete design unsuitability. The designers turned to a pair of engines for the reason that the country simply did not have a tank engine with the required power - 1200 hp. Ultimately, for the first prototypes of the IS-7 tank, it was decided to use the new TD-30 tank diesel engine, which was created on the basis of the ACh-30 aircraft engine. During the tests, this engine, installed on the first two prototypes, demonstrated its suitability for work, however, due to poor assembly, it required fine-tuning.
When working on a new power plant for a promising heavy tank, a number of important innovations were partly introduced and partly tested in laboratory conditions:
- fire-fighting equipment with automatic thermal cutouts, which worked at temperatures from 100-110 ° С;
- soft rubber fuel tanks with a total capacity of 800 liters;
- ejection engine cooling system.
Also, for the first time in Soviet tank building, designers used tracks with a rubber-metal hinge, double-acting hydraulic shock absorbers, beam suspension torsion bars, as well as road wheels with internal shock absorption, operating under heavy loads. In total, in the process of designing a new tank, about 1.5 thousand working drawings were made and more than 25 solutions were introduced into the project, which had not previously been encountered in tank building. 20 Soviet institutes and scientific institutions were involved in the development and consultations on the project of a new heavy tank. In this regard, the IS-7 became a truly breakthrough and innovative project for the Soviet tank-building school.
The main weapon of the first versions of the IS-7 was the 130-mm S-26 cannon, equipped with a new slotted muzzle brake. The gun had a high rate of fire for such a caliber - 6-8 rounds per minute, which was achieved through the use of a loading mechanism. The machine-gun armament was also powerful, which was only increased in the future. The first two prototypes housed 7 machine guns: one large-caliber 14.5 mm and six 7.62 mm. Especially for this tank, specialists from the laboratory of the Chief Designer Department of the Kirov Plant produced a remote synchronous-tracking electric machine-gun mount, built using separate elements of equipment from foreign technology. A specially made sample of the turret with two 7.62 mm machine guns mounted on the rear of the turret of the experienced IS-7 and successfully tested, providing the tank with high maneuverability of machine-gun fire.
In September-December 1946, two prototypes of the new combat vehicle were assembled. The first of them was assembled on September 8, 1946, until the end of the calendar year, he managed to pass 1000 km on sea trials, according to their results, it was recognized that the tank meets the previously set tactical and technical requirements. During the tests, a maximum speed of 60 km / h was reached, the average speed of a heavy tank on a broken cobblestone road was 32 km / h. The second sample, assembled on December 25, 1946, passed only 45 km during sea trials.
In addition to two experimental tanks, which were assembled by the workers of the Kirov plant and had time to pass tests in late 1946 and early 1947, two towers and two armored hulls were separately manufactured at the Izhora plant. They were intended for testing by shelling from modern 88, 122 and 128 mm guns. The tests were carried out at the NIBT Proving Ground of the GABTU in Kubinka. The results of these tests were used as the basis for the final booking of a new combat vehicle.
Throughout 1947, the design bureau of the Kirov plant carried out intensive work to develop a project for an improved version of the IS-7 tank, improvements were made to the design, including based on the results of tests of two prototypes. The new version of the IS-7 tank was approved for construction on April 9, 1947. Despite the changes made to the design, the tank still passed under the code "Object 260". The heavy tank project really retained a lot from its predecessors, but at the same time, a large number of significant changes were made to its design.
The body of the updated model has become a little wider, the tower is even more flattened. Also, the tank received new curved hull sides, such a solution was proposed by the designer G. N. Moskvin. The tank's booking was beyond praise. The frontal part of the hull consisted of three armor plates 150 mm thick, located at large angles of inclination, the "pike nose" scheme was implemented, already tested on the IS-3 serial tank. Thanks to Moskvin's suggestion, the sides of the tank acquired a complex shape, which also increased the security of the vehicle: the thickness of the upper inclined sides of the hull was 150 mm, and the lower concave sides were 100 mm. Even the rear part of the hull had a reservation of 100 mm (lower part) and 60 mm strongly inclined upper part. The cast four-seat tower of a very large size, at the same time, was extremely low and differed in large angles of inclination of the armor plates. The turret armor was variable: from 210 mm with a total inclination of 51-60 degrees in the frontal part to 94 mm in the aft part, while the thickness of the gun mantlet reached 355 mm.
An innovation of the 1947 machines was an even more enhanced armament. The tank received a new 130 mm S-70 cannon with a barrel length of 54 caliber. 33, 4-kg projectile fired from this gun had an initial velocity of 900 m / s. The 130-mm S-70 tank gun was designed at TsAKB (Central Artillery Design Bureau) specifically for the IS-7 tank. It was a tank version of an experimental 130-mm S-69 corps artillery cannon created here earlier. The gun had a vertical wedge semiautomatic bolt, and was also equipped with an electrically driven loading mechanism, similar to the type of naval artillery installations. This solution made it possible to provide the tank with a sufficiently high rate of fire.
Especially to remove gases from the fighting compartment of the tank, an ejector was placed on the gun barrel, and a system for blowing the barrel with compressed air was introduced. A novelty for those years and for Soviet tank building was the fire control system. The fire control device installed on the IS-7 provided guidance of a stabilized prism at a given target regardless of the gun, automatic firing of a shot and automatic bringing the gun to a stabilized aiming line when fired.
Machine-gun armament has become even more impressive. The tank received 8 machine guns at once: two of them were large-caliber 14, 5-mm KPV. One large-caliber and two 7, 62-mm RP-46 machine guns (post-war version of the DT) were placed in the gun mask. Two more RP-46 machine guns were located in the fenders, the other two were turned back and attached to the outside along the sides of the tank turret. All machine guns were equipped with a remote control system. On the roof of the tower, a second 14.5 mm machine gun was located on a special rod. It was equipped with a synchronous-tracking remote electric guidance drive tested on the first prototype. This system made it possible to effectively fire both ground and air targets, while under the protection of the turret armor. Ammunition of the IS-7 tank consisted of 30 separate loading rounds, 400 rounds of 14.5 mm caliber and another 2500 rounds for 7, 62-mm machine guns.
The heavy tank's crew consisted of five people, four of them were in the turret. To the right of the gun was the place of the vehicle commander, on the left side - the gunner. The seats of the two loaders were located at the back of the tower. They also controlled machine guns located in the fenders, in the rear of the turret and a heavy anti-aircraft machine gun. The driver's seat was located in the elongated bow of the hull.
The updated version of the IS-7 was distinguished by the installation of a new engine. It was decided to use a serial 12-cylinder marine diesel engine M-50T, developing a power of 1050 hp, as a power plant. at 1850 rpm. The engine was created on the basis of a diesel engine for torpedo boats. The installation of this engine, along with the use of a 130-mm gun, also with sea roots, turned the new tank into a real land, if not a battleship, then definitely a cruiser. For the first time in Soviet tank building, ejectors were used to cool the M-50T engine. At the same time, the capacity of the soft fuel tanks, which were made from a special fabric, was increased to 1300 liters.
The electric transmission was abandoned in favor of the mechanical one, created in 1946 together with the Bauman Moscow State Technical University. The undercarriage of the heavy tank included 7 large-diameter road wheels (on each side), there were no support rollers. The rollers were double and had internal cushioning. To improve the smoothness of the tank, the designers used double-acting hydraulic shock absorbers, the piston of which was located inside the suspension balancer.
The fate of the project. Unclaimed power
The first prototype of the IS-7 heavy tank, produced in 1947, began factory tests on August 27. In total, the car traveled 2094 km, after which it was sent to the ministerial bride. On tests, a tank weighing more than 65 tons accelerated to 60 km / h. In terms of its mobility, it surpassed not only heavy, but also medium tanks of its age. At the same time, experts noted the ease of control of the tank. Frontal armor made the vehicle invulnerable to the German 128-mm cannon, which it was planned to equip the Maus with, and could also protect the crew from shelling by its own 130-mm S-70 cannon. The use of a special loading mechanism made it possible to bring the rate of fire to 6-8 rounds per minute. For its age, the tank was revolutionary in terms of its characteristics, there was simply nothing like it in the world at that moment.
Based on the results of the tests carried out, the commission concluded that the IS-7 complies with the specified technical characteristics. 4 more prototypes were built, slightly different from each other, since the project was constantly being finalized. In the fall of 1948, prototype No. 3 was delivered for testing at the NIBT proving grounds. There was talk about the construction of the first batch of 15 combat vehicles, then in 1949 the order was increased to 50 tanks. However, these plans were never destined to come true. On February 18, 1949, on the basis of the Decree of the Council of Ministers of the USSR No. 701-270ss, the development and production of tanks weighing more than 50 tons in the country was stopped. This document put an end to not only the IS-7, but also another heavy tank, the IS-4. The main complaint was the large weight of the tanks, which made it difficult to evacuate them from the battlefield and transport them, not every road bridge could withstand their weight, and the number of railway platforms suitable in terms of carrying capacity was limited. It should be noted that serial tanks with a combat weight of more than 50 tons are not being built in our country until now.
Another heavy tank with the initials of the Soviet leader, the 60-ton IS-4, which was created and put into mass production at ChKZ in 1947, where it began to be assembled after the completion of the production of the IS-3, also played its negative role in the fate of the IS-7. … The heavy tank IS-4, which at the time of its creation had the most powerful armor among all domestic tanks, due to too high specific pressure on the ground (0.9 kg / cm²) was distinguished by low maneuverability on the ground, and not the most reliable transmission. At the same time, its armament was no different from the IS-2 and IS-3 tanks. However, the greatest disadvantage of this combat vehicle was precisely the large mass. Some believe that the IS-4 in some way discredited the idea of creating tanks weighing more than 60 tons, so the military initially had some skepticism about the even heavier IS-7. It is worth noting that an attempt to provide the tank with the highest level of protection brought the IS-7's combat weight to a record 68 tons, instead of the planned 65 tons.
Another possible explanation for the refusal of serial production of the IS-7 heavy tank was simply common sense and pragmatism. The concept of increasing the role of tanks in a probable nuclear missile war, which was nascent at that time, required the country to deploy large tank formations in advance, and therefore release the maximum possible number of armored vehicles even in peacetime. It was believed that in the first two weeks of a future hypothetical conflict, ground forces would lose up to 40 percent of their tanks. In such a situation, the adoption of the heavy tank IS-7, which had dubious prospects for mass production, was declared unacceptable by the military leadership. LKZ simply did not have sufficient capacity at that time, and the launch of production at ChKZ was almost unrealistic.
One of the prototypes of the IS-7 tank has survived to this day, the only tank built in 1948 can be seen in the collection of the Museum of Armored Weapons and Equipment in Kubinka. It is no exaggeration to say that the IS-7 was the best heavy tank ever created in the history of tank building, it would not have gotten lost against the background of modern MBTs. However, its development was not in vain. Many of the ideas implemented in the IS-7 were then used to create the Object 730 tank, which was put into service under the designation T-10 (IS-8).
