One of the most important qualities of field artillery is mobility. As the practice of wars in the first half of the 20th century has shown, sometimes it becomes necessary to quickly transfer cannons from one defense sector to another. Moving guns in a combat situation is a rather complicated procedure, which, moreover, takes a lot of time. All these shortcomings of conventional towed guns and howitzers led to the emergence of self-propelled artillery units. Mounted on an armored chassis, the gun had the ability to engage in battle almost without any additional preparations inherent in towed artillery. At the same time, the self-propelled guns could not be recognized as a full-fledged alternative to field guns. Some other solution was needed to ensure proper mobility.
Arsenalets
The first step in a new direction was made in 1923 at the Leningrad plant "Krasny Arsenalets". Designers N. Karateev and B. Andrykhevich developed a compact light armored self-propelled chassis for a 45-mm battalion gun. A boxer gasoline engine with a capacity of only 12 horsepower was located inside the armored hull of a design called "Arsenalets", which accelerated the chassis weighing a little less than a ton to 5-8 kilometers per hour. Obviously, with such driving characteristics, "Arsenalets" could not keep up with the troops on the march, so the caterpillar track was supposed to be used only for moving directly on the battlefield. Another characteristic feature of the design was the absence of any seat for calculating the gun. The fighter-driver followed the Arsenalts and controlled it with two levers. The prototype self-propelled gun was assembled only in 1928 and did not achieve significant success. Of course, the military was interested in the self-propelled chassis for field artillery, but the design of the "Arsenalets" did not provide any protection for the crew. After testing, the project was closed.
The Arsenalets self-propelled gun is very often referred to the class of self-propelled artillery installations. Due to the absence at the time of its development of any serious ACS projects, such a classification can be considered correct. At the same time, later self-propelled guns of domestic and foreign production were armored chassis with weapons and means of protection for soldiers installed on them. Naturally, all the artillery soldiers no longer had to go for their weapons on foot. So it is no less correct to classify "Arsenalets" to another class of artillery that appeared and formed two decades later - self-propelled guns (SDO).
SD-44
In 1946, the D-44 anti-tank gun of 85 mm caliber was adopted by the Soviet army. This weapon, developed in the Sverdlovsk OKB-9, actually combined all the experience in creating guns of this class. The design of the gun turned out to be so successful that the D-44 is still in service in our country. Soon after the adoption of the gun, the Ural engineers under the leadership of F. F. Petrova began working on a project to increase its mobility using its own engine. The project was prepared only by the beginning of 1949, when it was approved by the Ministry of Arms. The next few years were spent testing, identifying and correcting deficiencies. In November 1954, the self-propelled gun was put into service under the designation SD-44.
When developing a self-propelled gun carriage, OKB-9 designers followed the path of least resistance. The barrel group of the original D-44 cannon did not change in any way. The monoblock barrel with a two-chamber muzzle brake and breech remained the same. The gun carriage has undergone a solid revision. A special metal box was attached to its left frame, inside which was located a M-72 motorcycle engine with a power of 14 hp. Engine power was transmitted to the drive wheels through the clutch, gearbox, main shaft, rear axle, cardan drive and final drives. The engine and gearbox controls were moved to the trunk of the left frame. The driver's seat and steering unit were also mounted there. The latter was a unit consisting of a steering column, a steering mechanism and a steering wheel. During the transfer of the gun to the firing position, the guide wheel was thrown sideways and upward and did not prevent the bed opener from resting on the ground.
In the stowed position, the SD-44 gun weighed about two and a half tons. At the same time, it could travel at speeds up to 25 km / h, and 58 liters of gasoline was enough to overcome 22 kilometers. Nevertheless, the main method of moving the gun was still towing with other equipment with more serious driving characteristics. It is noteworthy that the SD-44 equipment included a self-recovery winch. In the stowed position, its cable was stored on a bulletproof shield, and, if necessary, it was fixed on a special drum on the axle of the driving wheels. Thus, the winch was driven by the main M-72 engine. It took no more than a minute to transfer the gun from the combat position to the stowed position and vice versa for the calculation of five people. With the advent of the An-8 and An-12 military transport aircraft, it became possible to transport the SD-44 cannon by air, as well as to parachute it.
SD-57
Soon after the end of the Great Patriotic War, a number of artillery pieces were developed in our country. Among others, the Ch-26 anti-tank gun of 57 mm caliber was created. This gun had a 74-caliber barrel with a wedge gate, hydraulic recoil devices, and a carriage with two beds and a wheel drive. Serial production of the Ch-26 gun began in 1951. At the same time, the idea arose to increase the mobility of the gun due to the ability to move around the battlefield without using a tractor, especially since OKB-9 was already closely involved in this issue. OKBL-46, which developed the gun, transferred all the necessary documentation to Plant No. 9 in Sverdlovsk: both enterprises had to design a self-propelled gun based on the Ch-26 on a competitive basis. The terms of reference provided for the installation of the engine, transmission and related equipment on the finished tool. In addition, it was required to retain the ability to tow with various tractors for transportation over long distances. Sverdlovsk engineers prepared a draft SD-57, OKBL-46 - Ch -71. In general terms, both options for the motorization of the gun were similar. Nevertheless, in 1957, the SD-57 cannon, which had the best characteristics, was adopted.
The gun itself did not undergo any major changes during the upgrade. The monoblock barrel was still equipped with a highly efficient dual-chamber muzzle brake. The wedge breech was a copy-type system and opened automatically after each shot. The barrel group of the SD-57 cannon is connected with a hydraulic recoil brake and a spring knurler. Guidance mechanisms, bulletproof shield, etc. the details remain the same. The carriage underwent a noticeable revision, which had to be equipped with an engine. A special frame for the M-42 engine was mounted on the left side of the gun carrier sheet. The carburetor engine had two cylinders and produced up to 18 horsepower. The engine was connected to a clutch, gearbox (three gears forward and one reverse), multiple shafts and final drives. The rotation was transmitted to the carriage wheels located directly under the cannon. 35 liters of gasoline were in the tanks inside and outside the beds. To ensure the possibility of independent driving and control of the direction of movement on the right frame (when viewed from the side of the cannon breech), a special unit was mounted that combined a guide wheel, a steering mechanism and a steering column. In addition, the gear lever and pedals were located in the same part of the bed. When bringing the gun to the firing position, the wheel folded sideways. The "origin" of the wheels of the self-propelled carriage is noteworthy: the drive wheels were taken from the GAZ-69, and the guide wheels were taken from the "Moskvich-402". For the convenience of the gunner-driver, a seat was installed on the same right frame. In the middle of the beds there were mounts for a box with ammunition. The SD-57 cannon in the stowed position weighed about 1900 kg. Together with the calculation of five people on the highway, she could accelerate to 55-60 kilometers per hour.
However, its own engine was intended solely for small crossings right on the battlefield. The gun was supposed to be towed to the place of battle by any suitable vehicle. In addition, the dimensions and weight of the gun made it possible, if necessary, to transport it by suitable aircraft or helicopters. So, the SD-57 could be transported, including on the recently appeared Mi-4 helicopter. The airborne troops were among the first to receive the new gun. It was understood that it was the self-propelled guns that should provide the landing units with proper fire support. Indeed, the SD-57 had the ability not only to land landing, but also parachute. At the same time, certain criticism was caused by the power of the gun. In the late 50s, the 57 mm caliber was clearly insufficient to defeat some armored targets. Thus, the SD-57 could successfully fight only with light armored vehicles of the enemy and field fortifications.
SD-66
The main way to increase the firepower of artillery is to increase the caliber. Simultaneously with the SD-57, OKB-9 was developing another self-propelled gun, this time with a caliber of 85 millimeters. The basis for the SD-66 project was the D-48 anti-tank gun, developed at the very end of the forties. In general, it was similar in design to the D-44, but differed in a number of technological and structural nuances. In particular, the D-48 received a new muzzle brake that absorbed up to 68% of recoil. Tests of the D-48 began in 1949, but were seriously delayed due to the fine-tuning of some components and assemblies. So, for example, just a few weeks after the start of testing, the designers were required to develop a new muzzle brake that would not send so many hot gases towards the gun crew. As a result, the adoption of the D-48 cannon took place only in the 53rd year.
In November 1954, OKB-9 was ordered to modify the D-48 cannon to the state of a self-propelled gun. Already in the early stages of the SD-48 project, it became clear that some new solution would be needed regarding the running gear of the gun. The original D-48 together with the gun carriage weighed about 2.3 tons - motorcycle engines would not have coped with the task. For this reason, a corresponding request was sent to the Moscow NAMI. In September of the following year, 1955, employees of the Automobile and Automotive Institute completed the design of the NAMI-030-6 engine with a capacity of 68 hp. and transmissions for it. During this time, the Sverdlovsk designers managed to develop a four-wheeled chassis with a ball shoulder strap and reclining openers. The four-wheeled platform was equipped with bridges from the GAZ-63 car and a similar control system. Thanks to a significant update to the appearance of the self-propelled gun carriage, the SD-48 could conduct a circular attack on targets. The new carriage turned out to be quite difficult and heavy. Therefore, to transfer the gun from the traveling position to the combat position and vice versa, it was necessary to introduce a separate hydraulic system with mechanisms for raising and lowering the gun.
In 1957, the SD-66 project was considered at the Main Artillery Directorate, where it became the object of criticism. To quickly transfer the gun to the firing position, it was required to transport the gun with the barrel forward, which was impossible with the chassis used. There were also claims about the rigidity of the structure and its wear during operation. Nevertheless, GAU recommended trying to correct the identified shortcomings and assemble a mock-up of a self-propelled gun. Shortly thereafter, the project was closed due to the impossibility of fixing all the shortcomings. It is worth noting that the first unsuccessful experience with a self-propelled four-wheeled chassis for a gun influenced the further development of this direction: after SD-66, all domestic SDOs were made according to a three-wheeled scheme, worked out on SD-44 and SD-57.
Sprut-B
The last Russian self-propelled gun at the moment is the 2A45M Sprut-B cannon, developed by OKB-9. The barrel of a 125 mm cannon has no grooves and is equipped with an original muzzle brake. The carriage of the Sprut-B gun was originally designed as towed, but capable of moving independently. In front of the cannon's bulletproof shield, to the right of the barrel (when viewed from the breech side) is an armored box, inside which the engine is located. The basis of the Spruta-B power plant is the MeMZ-967A engine with a hydraulic drive. Engine power is transmitted to the drive wheels located directly under the breech of the cannon. On the left side of the trunk is the driver's workplace with a steering wheel and other controls. The carriage design is interesting. Unlike previous self-propelled guns, "Sprut-B" has a three-bed support structure, which allows it to fire around targets. When the gun is transferred to the firing position, the front frame remains in place, and the side ones are spread to the side and fixed. The front idler is attached to the front frame and swings up. The drive wheels, in turn, rise above ground level, and the cannon rests on the beds and the central base plate.
In view of the large combat mass of the gun - 6.5 tons - the transfer to the combat or stowed position is carried out using the hydraulic system, which reduces the transfer time to one and a half to two minutes. The large weight affected the speed of movement: the gun's own engine provides no more than ten kilometers per hour on a dry dirt road. The low speed during independent movement is more than compensated for by the towing capabilities. With the help of trucks of the Ural-4320 type or MT-LB tractors, the Sprut-B gun can be towed along the highway at a speed of up to 80 km / h. Thus, the running parameters of the gun when towing are limited only by the capabilities of the selected tractor.
The Sprut-B cannon is interesting not only for its equipment for independent movement across the battlefield. The caliber and smooth barrel allow you to use the same range of ammunition that is used with the guns of domestic tanks. Separate cartridge-case shots make it possible to successfully fight the entire range of targets for the destruction of which anti-tank artillery is intended. So, for the destruction of enemy tanks there is a sub-caliber projectile VBM-17, and for firing at weakly protected targets and enemy manpower, the VOF-36 shot is intended. In addition, 9M119 guided missiles with laser beam guidance can be launched from the 2A45M cannon barrel. Such ammunition increases the radius of reliable hitting of targets with direct fire up to four kilometers and provides penetration of 700-750 millimeters of homogeneous armor behind ERA.
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Self-propelled guns are one of the most original ideas ever used in artillery. At the same time, they have not received significant distribution and there are several reasons for this. Firstly, at the time when the first full-fledged SDO projects appeared, the leading countries of the world could or sought to provide each gun with their own tractor. The self-driving equipment looked like just an additional measure. The second reason was the relative complexity of the production of such weapons. Despite the seeming simplicity - to install the engine and transmission on the carriage - the designers faced several rather difficult tasks. The main factor that prevented everything from being done quickly and simply was the shocks and vibrations that occur during shooting. Not every engine can handle such a load without damaging its own structure. Finally, the widespread use of self-propelled guns was hampered by views on the tactics of a hypothetical war. In fact, the SDO was really needed only by the airborne troops, which needed compact and light artillery suitable for landing or parachute landing. The reason for this was the relatively low carrying capacity of the available aircraft. After the appearance of heavy military transport aircraft and helicopters, the Airborne Forces were able to fully use the "combined arms" guns and tractors for them. Accordingly, the urgent need for self-propelled artillery has disappeared.
And yet you shouldn't fire up LMS for its seeming uselessness. The ability to independently move around the battlefield and beyond in a certain situation can save the lives of artillery soldiers or ensure timely repulsion of an attack. It is worth remembering that the class of self-propelled guns appeared as a result of the Second World War, when the mobility of field artillery was of high priority and was able to drastically affect the outcome of a battle or an entire operation. Currently, the world's leading armies are moving to new structures that imply the creation of highly mobile units. Perhaps, in the new look of the world armies there will be a place for self-propelled guns.
