Development methods for tank construction ideas have never been simple and straightforward. This statement is true for any country and perhaps for any generation. Sometimes, when studying information resources you cannot stop wondering how ambitious and unusual the ideas of many construction engineers were.
Search and creative work continued even when developing something radically new seemed to have no sense. For instance, in the 1940s, the classic concept of the tank was already formed. Caterpillar tread, the gun mounted in the rotating turret, tank compartment interior – all these parts became more or less a common standard. At first sight there was nothing to develop in this area at that time. Moreover, the attempt to deviate from the common concept was treated as something odd, which was unacceptable for a serious construction engineer.
A series of evidently unviable projects and ideas, which seized the USSR Central Defense Committee in the late 1930s, favored shaping of a negative image of armored vehicles with unconventional design layout. The specialists quickly got tired of studying great bunches of schemes and in order make their life easier, they decided to decline projects without their proper review in the way it was done with consideration given to perpetual engine projects by the invention bureau.
The reason why the tank project of military engineer third rank N.M Vostretsov wasn’t thrown to the trash box remains unknown as the official correspondence on the project’s practical realization hasn’t yet been found. Perhaps it is kept somewhere in the Central Archive of the Ministry of Defense, waiting for its sophisticated research. There are also few documents related to the development progress of combat vehicles SHT-1A and SHT-2T, the only remaining representatives of the particular vehicle types - spherical tanks, which were built, tested and one of them even took part in the warfare.
Nikolai Mikhailovich Vostretsov was born on May 2nd 1904 in Orenburg. His father was the head of the workshop at the knitting manufactory of the merchant Dolohov, his mother died when Nikolai was less than 3 years old. Father was in charge of bringing up the boy and used to take him to his workplace, showing how the manufacturing machines operated. This instilled the boy’s passion to mechanisms, and he hoped that his son would follow his footsteps in future. In school, Vostretsov junior showed his aptitude for exact sciences, and he would have taken his father’s business if it were not for the Revolution of 1917. When the country fell into Civil War, the boy had to stop studying. In 1919, Nikolai’s father, who didn’t sympathize with Red Army views, decided to leave the city and move to the eastern territories, which were under control of the Russian Army under the command of Admiral Kolchak. This decision resulted in a tragedy. One late evening not far from the steading Novo-Troitski, the wagon, which father and son were driving, was detected by the horse patrol belonging to the IV corps of the Kolchak army. Taking the pilgrims for enemy spies, Cossacks attacked the scared people. The father was knocked down by the horse. Nikolai, who was sitting on the edge of the cart, was whacked in his face with the whip. The boy jumped from the wagon and rushed to the roadside bushes. He ran through the forest for a long time, bumping on the trees until he fell on the ground exhausted. Having rested, badly injured and covered with blood, he made his way back to Orenburg and only within three days he arrived at the Red Army camp. Then he was put into hospital, where he got bad news, the boy’s left eye was badly injured.
Vostretsov lived alone in the old flat and took odd jobs until the end of the Civil War. After the war he sold his modest property and went to Moscow searching for a new life. He worked at Mitischenskiy factory, studied at worker’s faculty and later in Leningrad Polytechnic Institute. He returned back to the factory in 1936 and worked there as a constructor. Despite his disability, he got the permission to study in the Academy of Mechanization and Motorization WPRA.
In 1939, Nikolai Vostretsov was transferred to the construction bureau of KIM Moscow Automobile Factory, where he took part in designing and constructing light tanks. Due to his flexible way of thinking and good technical skills, he was soon awarded with military technician title of the second class.
In May 1940 Nikolai Vostretsov designed a medium tank with the model name “Spherical Tank” and provided it to the Central Defense Invention Committee. The design of the vehicle was extremely odd: the hull of the tank had a spherical shape; suspension was represented by two springy treads containing metal and rubber elements with spikes for proper terrain adhesion. According to Vostretsov, the construction should have been equipped with a 76mm gun mounted in the superstructure of the hull. The vehicle was supposed to be geared by paired gasoline engines M-17, similar to those mounted on the BT-7.
The “Spherical Tank project was suddenly on the go. However, due to the fact that the vehicle had a very unusual shape, the major factories didn’t get involved in the vehicle’s construction. The construction group, headed by Vostretsov, moved to Viksa, which is not far from Gorkiy (old name of Nizhny Novgorod), where construction engineers set to work.
In April 1941, the prototype of the ironclad “spherical” tank was assembled and prepared for tests. It quite significantly differed from the initial designs. First, the use of tread was considered as unnecessary. Instead, the tank acquired two wide tracks, which encircled the tank. The tracks were pulled on the rims and when necessary, could be easily dismantled. Without tracks the tank could move but its maneuverability characteristics significantly dropped. Nevertheless, this very drawback could be treated as insignificant. Far more important was the fact that unlike the tanks of standard construction, the spherical tank didn’t lose its mobility when tracks were wrecked.
The armament scheme of the tank had changed. The machine-gun turret, similar to that of a T-28 medium tank, was mounted instead of the gun superstructure. A coaxial machine gun DT should have been mounted in the machine gun turret. Sponsons for 76mm short-barreled guns L-10 were fixed on both sides of the tank. This meant the loss of round fire capability was compensated by doubling the fire power. Taking into account the very high maneuverability characteristics of the spherical tank, complete rotation of the hull to the target wasn’t a big problem.
The balancing system was wisely designed. Generally speaking, due to the gyroscope principle, the spherical tank moved rather firmly. However, when turning, in cases of sudden stops or other quick maneuvers, there was a risk it could turn over. In order to prevent this, Vostretsov developed a ballast system, which was a balance wheel weighing 4 tons and hidden under the tank’s bottom. The upper part of the balance wheel was attached to the independently fixed floor of the cabin, which was always in horizontal position regardless of the tilting angle of the tank.
It was decided to use a B-2 diesel engine instead of the gasoline version because the construction engineers thought it to be the more reasonable option.
Road tests proved that the tank behaved well on the terrain. It was easy to handle, it turned standing in one place like a top and easily passed ditches and trenches. When rapidly accelerating, the tank could jump up a 1.2 meters high scarp.
On the other hand, many defects came out. The propulsion rims turned out to be prone to quick deformation because of inappropriate wrong steel grade, and the ventilation system malfunctioned so that the compartment became quickly filled with smoke. The walking floor of the tank was prone to jamming in most improper positions. Nevertheless, spherical tank was recommended for further tests and received the SHT-1A index.
After the beginning of the Great Patriotic War, development work on the spherical tank significantly slowed down. There weren’t enough resources which could be allocated to the group of designers. However, the project wasn’t closed due to its quite serious development prospect. During the peace time period it was decided to replace the expensive gun L-10 with the F-34, a similar gun which was mounted on the T-34 tank. In the middle of 1942, Vostretsov announced that the project development should be postponed. At the same time he started developing another spherical tank – SHT-2T weighing 35 tons.
This tank was 15 tons heavier than its previous model. Its armor, therefore, was thicker and the tank itself was bigger. The tank being average in classification, behaved on terrain more like a quick heavy tank, which consequently led to introduction of “T” letter in its index.
The construction engineers intended to make SHT-2T an assault tank designed to break through the enemy defense positions. It is not surprising that two 152mm ML-20 1937 year model howitzers were mounted in its sponsons. These powerful guns could also be used on the move: the sponsons balancing system neutralized the recoil. However, the gunner found himself in quite a complicated situation because each time the tank shot, the gunner together with his seat was lifted up almost vertically.
The landfills test of SHT-2T took place in July 1943 together with military tests of the final SHT-1A modification. The last one was equipped with 85mm D-5C gun, recently developed by F.F. Petrov. Despite the fact that the overall accuracy improved, Vostretsov decided that there is no possibility to develop two projects simultaneously and therefore again put the project aside.
After tests and improvement of SHT-2T, it was decided to test it in real combat conditions. On August, 10 1943 the tank was put on the flatcar and sent to Chernigov, where the major offensive operation was about to begin. To keep the new tank in secret, it was covered with a large plank box. It was written in accompanying documents that it was a new type of obstructive aerostat with a solid hull frame was being redeployed for tests to the front line.
The tank engaged in the battle with a special tank company of the 2nd Tank Army. It was planned that the tank would be involved in the battle in the secondary wave. However, these plans were interfered by circumstances. On September 12th 1943, a German group of up to two motorized infantry companies with support from 6 Pz IV tanks and one tank destroyer Stug flanked the attacking Soviet division. There was not a single military platoon nearby which could stop Germans except for the company which included SHT-2T. Having received the battered infantry company as support, Soviet soldiers joined the battle against the Germans near the village of Gudzevka.
The appearance of the spherical tank slightly confused the enemy forces. They even ceased fire for some time. The tank accelerated and started to move towards German infantry, together with two T-34 tanks. The Germans didn’t even have time to deploy the anti-tank gun before the spherical vehicle was about 50 meters from their position. Two howitzer shots mixed the enemy ammunition together with the combat crew. While the guns were reloading, the tank moved along the enemy defense line firing with machine-guns. Almost the entire enemy company quickly retreated.
A Pz IV tank standing at the edge of the forest fired at the Soviet spherical tank, but the shell didn’t penetrate the curved armor plate. The SHT driver turned the vehicle towards the enemy tank. The German vehicle hastily backed to the forest. It could have escaped but for the track, which got stuck in the pit. The tank tilted to one side with its bottom firmly stuck before skidding and turning for some seconds trying to get away from the trap. Then SHT opened fire with its two howitzers again. One shell missed the target and the second practically blew the turret off the German tank.
Having come to their senses, the Germans opened fire at the strange vehicle using all their guns. Tankers of the special tank company recalled that enemies were shooting at the spherical tank even from machine-guns. However, only multiple sparks bounced from the armour plates. After a few seconds SHT-2 received a hit at the right sponson and remained with one gun. The two guns scheme proved its efficiency that time: the tank rapidly turned towards allies’ position having simultaneously fired at the German troop’s position. The explosion knocked out another anti-tank gun together with its crew.
SHT-2T proved its high combat efficiency. The USSR People's Commissariat of Heavy Industry issued a decree to put the tank on combat duty. However, the decision hasn’t been taken: it was necessary to build a special factory in order to set up mass production of spherical tanks.
It was a great shock for Vostretsov. The construction engineer shrank into himself, but continued working. In January 1944, Nikolai Mikhailovich fell ill with flu. The state of health of the designer shaken by work, stress and poor nutrition finally gave away. As a result, there were complications and flu turned into meningitis. Despite all the best efforts of the doctors, Vostretsov died in the hospital in Gorgiy on February 8, 1944.
After death of the engineer, blueprints of another tank project were found in his documents. The tank was entitled “Object “Sphere””. It was a vehicle weighing 55 tons and it was considered as an alternative to the heavy tank IS-2. It should have been equipped with 122 mm guns, mounted in side sponsons. The speed limit of the tank was 60 km/h and it was capable of running underwater. But unfortunately, this tank remained in sketches.