In the second half of the forties, the development of new types of military equipment intended for the airborne troops began. Among other things, the Airborne Forces needed light airborne artillery self-propelled guns. In the shortest possible time, several similar machines with different weapons were proposed. One of the most interesting samples was the ASU-57 machine, developed at OKB-115.
Glider and self-propelled gun
In the creation of new armored vehicles for the Airborne Forces, the leading role was played by enterprises that had the necessary experience in this area. However, in 1948, OKB-115, headed by A. S. Yakovlev. At that time, the bureau was developing the Yak-14 landing glider, and in parallel it was planned to create a light SPG compatible with it. The new sample was named ASU-57 ("Airborne self-propelled unit, 57 mm"), because of which it can be confused with the development of the same name of the plant # 40.
According to some sources, the project of the self-propelled gun ASU-57 was created not by OKB-115, but by the Kharkov tank repair plant No. 115. However, the data discovered and published in recent years refutes this version. It was the aviation design bureau that made the new model of land equipment.
Despite the lack of experience, OKB-115 quickly coped with the new task. The assignment for the design of the ACS appeared at the beginning of February 1948, and by the end of February a set of drawings was to go into production. The start of factory tests was scheduled for the end of March. During the development, the approved appearance of the car had to be adjusted, but its radical changes were not envisaged.
Design features
The ASU-57 project provided for the construction of a tracked ACS of a conning tower with a partially open fighting compartment. The front part of the hull was given over to weapons and crew seats, and behind them was the engine compartment. Measures were taken to simplify operation in the Airborne Forces, in particular landing.
ACS received a welded hull with differentiated armor thickness from 4 to 12 mm. The frontal projection was covered with a large inclined sheet, above which was placed the so-called. lantern - a curved shield with viewing devices. For suspension under the cargo glider, the lantern was folded back and down. The frontal plate had a niche for a gun mount.
In the stern of the hull, on the right along the side, a GAZ-M-20 gasoline engine with a capacity of 50 hp was mounted. The transmission included a bevel main gear, a four-speed GAZ-AA gearbox, two side clutches and two single-row final drives. The engine and transmission were controlled by a traditional set of levers and pedals. The electrical system of the machine was based on the GBF-4105 generator.
The undercarriage had four rubberized road wheels with torsion bar suspension on each side. The same roller without a rim was used as a steering wheel. The drive wheels were placed at the back. The caterpillar was assembled from the tracks borrowed from the T-20 "Komsomolets" tractor.
A machine for mounting the main armament was placed in the bow of the hull. ASU-57 received an automatic cannon 113P with a caliber of 57 mm, originally created for promising fighter aircraft. The gun was mounted with a shift back, because of which only a limited part of the barrel with a muzzle brake protruded through the embrasure. The barrel passed through the habitable compartment, and the breech was located next to the engine compartment.
The 113P cannon used a short recoil based automatic. The technical rate of fire is 133 rounds per minute. Next to its breech on the left was a feed mechanism with a box for loose tape for 15 unitary shots 57x350 mm. Nearby were two boxes for 16 and 20 shells. Normal ammunition was determined at 31 shots, with an overload - 51 with the placement of an additional tape in a separate box. Recharging after the consumption of the first tape was carried out hydraulically. The next reload required crew intervention.
The gun mount received hydraulic drives for aiming in two planes, as well as a hydraulic reloading mechanism. Horizontal aiming was carried out in a sector with a width of 16 °, vertical - from -1 ° to + 8 °. Aviation collimator sight PBP-1A was used for guidance. Later it was replaced by the K8-T product, borrowed from tank machine-gun installations.
The crew consisted of only two people. To the right of the cannon in the nose of the hull was the driver. The gunner commander was placed on the left. For observation, they had their own observation devices in the lantern. Access to the crew seats was through the roof. Nominally, the ACS was supposed to have a radio station, but it was not installed on the prototype.
The length of the ASU-57 from the OKB-115, taking into account the gun, slightly exceeded 4.5 m. The width was 3.8 m, the height was only 1.38 m in the firing position, or slightly more than 1 m with the lantern folded. Combat weight - 3255 kg. The car was supposed to reach speeds of up to 45 km / h, and the 120-liter tank gave 167 km of power reserve. ASU-57 had to overcome various obstacles, incl. fordy.
Failed tests
At the beginning of the summer of 1948, plant No. 115 handed over a prototype of the new amphibious assault rifle to the Kubinka training ground for testing by the army. For several weeks, the car demonstrated driving and fire performance. The test results were far from desired.
The power plant of the ACS turned out to be weak. Service was difficult. There was no shielding of the wiring. After 62 hours of operation, the engine had to be changed due to a serious breakdown. The transmission, however, worked normally and without significant problems. The undercarriage was not strong enough, and therefore regularly needed to tighten the bolts and nuts. There were no slats above the track, which caused the self-propelled gun to become covered with dust. The absence of a muffler on the exhaust pipe created discomfort and led to the risk of fire.
Fire tests were limited to 21 shots, after which all the shortcomings became clear. The muzzle brake of the 113P cannon raised dust, interfering with observation, and also negatively affected the crew. In addition, at the first shot, he broke the only headlight. The hydraulic guidance system provided insufficient movement angles of the gun. At the same time, there was no synchronous movement of the gun and sight. During operation, the pressure in the hydraulic system quickly dropped, interfering with guidance. The design of the guidance systems excluded the use of a traveling gun stopper.
The collimator air sight made it difficult to aim at long distances. The ammunition supply system was unsuccessful. The project provided for a quick replacement of the tape by the gunner, but in practice, reloading required the work of two gunners and took about 10-15 minutes. In this case, people had to leave the protected compartment.
There were many other disadvantages as well. Poor protection of the crew from shelling from the side and from the stern, the absence of an entrenching tool, an insufficient set of spare parts, etc. were noted.
According to the test results, the ASU-57 was recognized as unsuccessful and did not meet the requirements of the army. The prototype was returned to the manufacturer. Soon, comparative tests of several new models were completed, and the car of the same name from plant No. 40 was adopted.
Attempt to modernize
In the same 1948, OKB-115 made an attempt to correct the shortcomings and improve the existing ACS. New proposals were implemented on a model, and then in the form of a full-fledged prototype.
The modernization project provided for the abandonment of the semi-open habitable compartment. Additional armor appeared behind the lantern, which formed the roof of the wheelhouse. The viewing devices in the lantern were being altered. The boxes for spare parts and other property, as well as external fasteners, have undergone a major update. The composition of the power plant was retained, but all auxiliary units were altered, which caused complaints during the tests.
The gun mount lost its hydraulics and was operated by manual mechanisms. The declination angle was increased to -2 ° with the possibility of increasing to -5 ° by opening the hatches above the breech. The hydraulics in the gun reloading mechanism were replaced by pneumatics. The PBP-1A sight was replaced with an OP-1 product with magnification. Other minor improvements were introduced.
ASU-57 still did not have machine-gun armament, but now it was proposed to supplement the gun with missiles. At the stern, it was planned to mount a lightweight detachable launcher for 30 RS-82 rockets. The launch was controlled from under the armor or from the remote control.
The updated ASU-57 retained the same dimensions, but became heavier up to 3.33 tons. The launcher for the RS-82 added 320 kg of mass. Mobility remained the same.
At the end of October 1948, the ASU-57 of the second version was sent to Kubinka for new tests. After inspections, at the beginning of February 1949, it was returned to plant No. 115 without any particular complaints about the operation and reliability of the units. However, the military no longer considered the OKB-115 project in the context of future rearmament.
The further fate of the experienced ASU-57 is not known for certain. Apparently, they did not save it and dismantled it for parts. The first and last project of the aviation OKB-115 in the field of ground armored vehicles did not give the desired results. It should be noted that the Bureau nevertheless made a significant contribution to the development of the airborne troops. His glider Yak-14 entered service and was actively used for many years. However, he had to carry self-propelled guns ASU-57 developed by another bureau.
