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ASU-57 airborne self-propelled mount

The ASU-57 was a small, lightly constructed Soviet assault gun specifically designed for use by Soviet airborne divisions. From 1960 it was replaced by the ASU-85. The ASU-57 was designed to be a light-weight assault gun that could be air-dropped and deployed by rocket-assisted parachute along with the troops. It was lightly armored and armed with a 57 mm gun Ch-51, a development of World War II ZIS-2 but with some similarities to the Ch-26. From 1954, an improved 57mm gun Ch-51M with much shorter double-baffle muzzle brake was fitted. The ASU-57's engine was taken from the GAZ-M-20 "Pobeda" civilian car. The ASU-57 was a successful design, and saw service with Soviet airborne divisions for around 20 years before being replaced by the ASU-85. During its years of operation 54 vehicles would have been assigned to each airborne division.

For airborne units, after landing to their destination, the most dangerous are mechanized and tank units. In the Soviet Union in this area, designers focused on creating anti-tank automated control systems. The military department does not completely abandon the idea of a tank for the airborne troops, but ACS has become one of the main types of armored airborne equipment for a long time.

The end of WW2 was marked by the creation of new models of various weapons and equipment for all military branches, including the Airborne Forces. Previously, in the construction of airborne landing equipment, attention was paid to light tanks. The British attempt to move away from this principle and create a semi-closed type self-propelled installation with a 57-caliber gun on the chassis of a light tank. The British did not implement the project.

Self-propelled anti-tank airborne guns were built on the original chassis, designed on OKB-40. In October 1946, the designers of the Gorky Plant No. 92 began the development of 76 mm guns, the designers of the Mytishchi Plant No. 40 began the development of the original chassis for the design of the airborne landing system in March 1947. The ready sketch of the original chassis called "object 570" was prepared in November 1947. The first prototypes of the LS-76S guns are ready. The guns are transferred to the Mytishchi plant, where they are equipped with ready-made chassis. In December of the same year, the first self-propelled gun is ready for testing at the beginning of 1948. The self-propelled gun began to undergo factory tests. By the middle of the year, the prototype entered a series of field tests. By the end of 1948, a sample of the LB-76S gun was called D-56S and was ready for mass production.

Tests at the test site ASU-57 were held in April 1949. In mid 1949 four experimental airborne self-propelled guns underwent tests in the 38th Airborne Corps. In June of that year, the vehicle passed military tests. On December 17, 1949, by a resolution of the Council of Ministers of the USSR, self-propelled guns were adopted for service under the name ASU-76. This was the first armored vehicle that entered the USSR Armed Forces specifically for the Airborne Forces.

The ACS-57 series production was launched in 1951. The guns for the “Ch-51” and “Ch-51M” installations were manufactured by Plant No. 106, the chassis was assembled at the MMZ, and the ASU-57 self-propelled guns were fully assembled at the same factory.

The body design is a box of welded and riveted panels. Nose - two armored plates welded to the sides of the hull. The lower armor plate is attached to the front of the bottom. Hull sides, made as vertical armored sheets, are connected by welding with niches of the suspension and sides, and with frontal shields. The bottom of the machine is made of duralumin sheet, rivets connected to the frontal armor plates and niches in the pendants. Protection of the fighting compartment - folding frontal and side sheets. The duralumin sheet mounted at the stern is riveted to the sides and bottom of the hull. The car is covered with a tarpaulin top. The MTO is located in front of the car, a gun, ammunition, observation devices, sights, and a radio station are located in the stern. The places of the commander of the self-propelled installation and the driver-mechanic are immediately located. The commander at the same time performed all the duties of the loader, gunner and radio operator.

The fighting compartment, where the Ch-51 gun of 57 mm caliber was located, turned out to be quite cramped. Monoblock type gun barrel equipped with an ejector and a muzzle brake. Also, the gun was equipped with a clip vertical shutter, a mechanical semi-automatic and a trough-type cradle. In front of the cradle is a pipe in which a hydraulic retractable brake and a recuperator are located. Behind the cradle, guides were placed to capture the trunk. The cradle and the swinging part of the gun are made on the frame. The lifting mechanism is made of sector type. Vertical angles from 12 to -5 degrees. The rotary mechanism of the screw type made it possible to point the gun horizontally from 8 to - 8 degrees. When firing a shot from a closed position, a panorama was used; when firing a shot from an open position, an optical sight OP2-50 was used. The average rate of fire was 10 rds / min.

Gun ammunition - 30 unitary ammunition. Ammunition used: sub-caliber armor-piercing tracer, armor-piercing tracer with armor-piercing up to 10 centimeters, high-explosive fragmentation with a range of up to 6 kilometers.

In 1955, work began on the modernization of the guns. The upgraded gun is called Ch-51M. The gun received a slotted type muzzle brake. The opening of the shutter and the release of the sleeve began to be made at the end of the run. The turning mechanism received a braking device. The average rate of fire was 10 rds / min. Gun ammunition - 30 unitary ammunition. Ammunition used: sub-caliber armor-piercing tracer, armor-piercing tracer with armor-piercing up to 10 centimeters, high-explosive fragmentation with a range of up to 6 kilometers.

The gun received a slotted type muzzle brake. The opening of the shutter and the release of the sleeve began to be made at the end of the run. The turning mechanism received a braking device. The upgraded gun is called Ch-51M. The gun received a slotted type muzzle brake. The opening of the shutter and the release of the sleeve began to be made at the end of the run. The turning mechanism received a braking device.

Due to the use of aluminum alloys in the design, the designers achieved a reduction in the size of the machine, as well as a reduction in its mass. The bow was made of two armor plates welded together and with the sides of the hull. The front of the bottom was attached to the bottom sheet. The sides of the hull were vertical armored plates, which were welded to the niches of the suspension and sides, as well as to the frontal shields. The bottom of the hull and feed were protected by duralumin sheets. For the convenience of the crew, the upper parts of the frontal and side sheets were made folding.

The chassis of the machine included three rubberized road wheels, a rubberized idler wheel, which is also a support one, with a built-in screw-type tension mechanism, two support rollers and sprockets on each side, with two gear rings with an asymmetric tooth profile. The vehicle received high mobility and throughput thanks to the caterpillar mover. The suspension of the car was a tubular-rod torsion bar with hydraulic shock absorbers on the front nodes. The 204 mm wide metal small track chain consisted of 80 tracks.

In the MTO of the machine there is a 4-cylinder liquid-cooled engine M-20E. The designers assembled in a single unit, which is located on 4 elastic supports in the MTO, gearbox, engine, side clutches. An individual torsion bar suspension with hydraulic shock absorbers is located on the front nodes. Each side has 4 road wheels dressed in rubber and 2 supporting rollers. The last roller of the supporting type serves as a guide, for this it is provided with a screw tension mechanism. Caterpillars are metal, with a fine link. And, although the caterpillar turned out to be rather narrow, the specific pressure of the self-propelled gun was extremely low, which allowed the ACS to calmly pass both deep snow and swamp areas. For external communication in the ASU-57, a 10RT-12 radio station was used.

The vehicle could immediately overcome a ditch or trench up to 1.4 m wide and a vertical obstacle up to 0.5 m high. The maximum elevation angle reached 30 °. ASU-57 could overcome water obstacles, but only ford, because it was not equipped with floating equipment. The depth of overcoming fords should not exceed 0.7 m. The specific pressure of the machine on the ground was only 0.35 kg / cm2, which is equal to the pressure on the ground of an adult. The installation was transported with the help of heavy Yak-14 and IL-32 gliders, and to avoid the buildup of the hull at that moment, the machine had a special device that fixed the extreme nodes of the suspensions to the hull.

For transportation of self-propelled guns used aircraft BTA. The main carrier was the Yak-14, from which the ASU-57 was parachuted. The self-propelled crew landed with airborne units separately from the machine itself. To keep the machine inside the aircraft stationary, a special device was used, which was attached to the suspension nodes on the ACS. In 59, the Soviet Union adopted the An-12 transport aircraft. This significantly increased the capabilities of the airborne units during landing. Now the units with their equipment confidently fit in the same plane. An-12 series aircraft were equipped with TG-12 roller conveyors. For the production of ASU-57 landing, specially designed parachute platforms were used. The platforms were equipped with multi-dome parachute systems MKS-5-128R and MKS-4-127. The platforms were called PP-128-500, and a little later they used the P-7 platform. One An-12B aircraft could accommodate two self-propelled guns at a checkpoint. The total weight of the ASU-57 on the PP-128-500 is 5.16 tons. A self-propelled gun could also be transported by a heavy helicopter, produced in 1959 - Mi-6.

On the basis of ASU-57 two more cars were created. ASU-57P - floating airborne self-propelled artillery mount. The car appeared in 1954. Its power transmission included a power take-off box with a drive to a propeller located in the bottom niche. First, the designers equipped the machine with two propellers driven by steering wheels. This provided remarkable maneuverability on the water, however, the tracks did not turn off, when approaching the shore the engine worked in lower gears, so it lacked traction. A more successful option was already tested on a light pre-war tank T-40, where the propeller with the rudder in the stream were located in the tunnel. The cooling system was additionally equipped with a heat exchanger, which provides heat removal from the coolant to the seawater leaving the propeller when afloat.

In addition, the Ch-51P gun was installed on the ASU-57P, an improved version of the Ch-51M, in which the pipe was connected to a more technologically advanced active muzzle brake, breech structure, semi-automatic mechanism and a lifting device.

This improved version of the ASU-57P was never adopted. Not the last role in this was played by rather weak security, meeting the needs of the armed forces in this kind of machines due to the ASU-57 already mass-produced, as well as the appearance of the already more powerful SU-85 machine by that time.

The ASU-57 was one of the lightest armored vehicles of its time, especially among tracked vehicles, by mass being at the level of tankettes and small tanks. The dimensions of self-propelled guns, exceeding the ZIS-2 anti-tank gun by only 90 mm in height and 441 mm in width, were extremely small as well. Some experts ASU-57 was seen in some way as a successful solution for the reconciliation of wedges with anti-tank gun, which tried to implement in various countries of the 1930s.

The ASU-57 was one of the first steps on the transformation of Soviet airborne forces from lightly armed units, capable of performing only limited tasks and focused mainly on passive defense of the landing area, to fully mechanized mobile forces. In the 1950s, the ASU-57 attracted considerable attention of Western military experts; according to some estimates, the airborne troops of the NATO countries did not have anything comparable, relying on 106-mm recoilless guns as heavy weapons.

The general estimates of ACS-57 by experts accumulated since the Cold War are rather contradictory. So, in Soviet and post-Soviet literature, the assessment of ASU-57 as an effective anti-tank weapon is common. In Western sources, the effectiveness of ACS-57 received a mixed assessment. Developed according to the requirements of 1940, the cannon in the 1950s was already outdated. Steve Zaloga gave a low rating to the anti-tank capabilities of the ASU-57, as the modest 57mm shell would have been ineffective against Western tanks of the 1950s. By other specialists, however, the ASU-57 was assessed as an effective means of giving troops additional firepower as an assault gun, and by some in the 1970s it was assessed as obsolete, but still effective in this role.

Despite all its shortcomings, however, the ASU-57 made a significant contribution to increasing the firepower, anti-tank capabilities and mobility of the Soviet airborne troops. As an additional advantage of the ASU-57, it was also noted that the practice of transporting infantrymen on armored self-propelled guns, common in the Airborne Forces, increased the mobility of the airborne assault forces, which is traditionally low for this type of troops due to the shortage of airborne vehicles. Despite the small size of the machine and its significant overload during such use, in addition to increasing mobility, infantrymen and self-propelled guns could balance and in close cooperation support each other in battle.