ISU-152 of 1945 (Object 704) - an experienced Soviet heavy self-propelled artillery installation (ACS) during the Great Patriotic War. In the name of the vehicle, the abbreviation ISU means “self-propelled unit based on the IS tank” or “IS-installation”, and the index 152 is the caliber of the vehicle's main armament. Clarification of the "1945 model" was required to distinguish the experimental ACS from the serial ISU-152.
Developed by the design bureau of experimental plant No. 100 in 1945 under the leadership of Joseph Yakovlevich Kotin, chief designer of domestic heavy tanks and self-propelled guns of that time. Unlike other experienced self-propelled guns, the ISU-152-1 and ISU-152-2, which were just non-standard rearmed production vehicles, the ISU-152 mod. 1945 was a completely new design. The adoption of the IS-3 heavy tank set the designers of the experimental plant No. 100 the task of creating an appropriate ACS based on it. Since the IS-3 was a radically revised IS-2 in terms of armor protection, the ACS based on it was also designed as an analogue of the serial ISU-152 based on the IS-2 with improved armor.
Enhanced protection was achieved both by increasing the thickness of the armor and placing it at more favorable angles to counter the armor-piercing action of shells. The developers of the armored hull successfully coped with the task: the forehead of the installation was a solid rolled armor plate 120 mm thick, inclined at an angle of 50 ° to the vertical. For comparison, the serial ISU-152 had frontal armor parts 90 mm thick and inclined 30 ° to the vertical. The armor of the gun mask was increased to 160 mm, and together with the armored casing of the recoil devices, the total maximum thickness of the gun armor reached 320 mm. Due to the rearrangement of the fighting compartment, the total mass of the ACS increased by only 1.3 tons compared to the serial ISU-152. For the heavy self-propelled guns ISU-152 of the 1945 model, it had a record low overall vehicle height - 2240 mm. Among all the experienced and serial Soviet self-propelled guns during the Great Patriotic War, the ISU-152 of the 1945 model was the most protected from enemy fire. Its frontal armor was able to withstand the fire of even the most powerful German Pak 43 anti-tank gun.
The design bureau of Fyodor Fedorovich Petrov for the new SPG developed a new modification of the ML-20SM howitzer-gun, the idea of which was put forward back in 1943. Its most important difference from the serial ML-20S was the absence of a muzzle brake, which made it impossible to fire from a gun in the presence of an assault force on the self-propelled armor.
However, the desire to obtain maximum security with fixed dimensions and weight turned into a quite expected drawback - the tightness in the fighting compartment of the self-propelled gun. The rejection of the muzzle brake in the design of the gun led to an increase in its recoil length to 900 mm, and the favorable angles of inclination of the frontal booking required the driver's workplace to be moved to the upper left of the fighting compartment. The field tests carried out showed that such its location leads to a decrease in the viewable space and increased fatigue of the driver due to the large vibration amplitudes of the armored hull when the ACS moves on an uneven surface. As a result, the ISU-152 of the 1945 model was not adopted by the Red Army and was not mass-produced. The only released prototype of this self-propelled gun is currently on display in the Armored Museum in Kubinka near Moscow.
Description of construction
The ISU-152 of the 1945 model had the same layout as the serial Soviet self-propelled guns of that time (with the exception of the SU-76). The fully armored hull was split in two. The crew, gun and ammunition were located in front in the armored wheelhouse, which combined the fighting compartment and the control compartment. The engine and transmission were installed in the rear of the vehicle.
Armored hull and wheelhouse
The self-propelled armored body was welded from rolled armor plates 120, 90, 60, 30 and 20 mm thick. Differentiated armor protection, cannon-proof. The armored plates of the cabin and hull were installed at rational angles of inclination. The recoil devices of the gun were protected by a fixed cast armored casing and a movable cast armored mask, each of these parts had a thickness of up to 160 mm in the parts most susceptible to enemy fire.
Three crew members were located to the left of the gun: in front of the driver, then the gunner, and behind the loader. The vehicle commander and the castle commander were to the right of the gun. The embarkation and exit of the crew were made through four hatches on the roof of the wheelhouse. The round hatch to the left of the gun was also used to bring out the extension of the panoramic sight. The hull also had a bottom hatch for emergency escape by the crew of self-propelled guns and a number of small hatches for loading ammunition, access to the necks of fuel tanks, other components and assemblies of the vehicle.
Armament
The main armament of the ISU-152 of the 1945 model was the ML-20SM howitzer-gun of 152.4 mm caliber with a piston bolt. The ballistics of the gun was similar to the previous version of the ML-20. A large-caliber machine gun of 12.7 mm caliber DShK was paired with the gun. The twin unit was mounted in a frame on the frontal armor plate of the wheelhouse along the centerline of the vehicle. Its vertical guidance angles ranged from −1 ° 45 ′ to + 18 °, horizontal guidance was limited to a sector of 11 °. The range of a direct shot at a target with a height of 2.5-3 m was 800-1000 m, the range of a direct fire was 3.8 km, the greatest firing range was about 13 km. The shot was fired by means of an electric or manual mechanical trigger, the practical rate of fire is 1-2 rounds per minute.
The ammunition load of the gun was 20 rounds of separate loading. The shells were laid along both sides of the wheelhouse, the charges were in the same place, as well as on the bottom of the fighting compartment and on the rear wall of the wheelhouse.
To protect against air attacks, the ACS was equipped with a second, anti-aircraft heavy machine gun DShK on a rotating turret near the loader's hatch with a K-10T collimator sight. Ammunition for coaxial and anti-aircraft machine guns was 300 rounds.
For self-defense, the crew had two submachine guns (submachine guns) PPSh or PPS and several F-1 hand grenades.
Engine
The ISU-152 of the 1945 model was equipped with a four-stroke V-shaped 12-cylinder V-2-IS diesel engine with a capacity of 520 hp. with. (382 kW). The engine was started with a 15 hp ST-700 electric starter. with. (11 kW) or compressed air from two tanks with a capacity of 10 liters in the fighting compartment of the vehicle. Diesel V-2IS was equipped with an NK-1 high-pressure fuel pump with an RNK-1 all-mode regulator and a fuel supply corrector. To clean the air entering the engine, a Multicyclone filter was used. Also, a thermosiphon heater was installed in the engine-transmission compartment to facilitate starting the engine in the cold season and heating the fighting compartment of the vehicle. The ISU-152 of the 1945 model had three fuel tanks, two of which were located in the fighting compartment and one in the engine compartment. The total capacity of the internal fuel tanks was 540 liters. The self-propelled gun was also equipped with two external additional fuel tanks (each 90 liters), not associated with the engine fuel system.
Transmission
ACS ISU-152 of the 1945 model was equipped with a mechanical transmission, which included:
multi-disc main clutch of dry friction "steel according to ferodo";
four-speed gearbox with a range (8 gears forward and 2 reverse);
two onboard two-stage planetary swing mechanisms with a steel-on-steel dry-friction multi-disc locking clutch and band brakes;
two double row combined final drives.
Chassis
The ISU-152 model 1945 has an individual torsion bar suspension for each of the 6 solid gable road wheels of small diameter on each side. Opposite each road roller, the travel stops of the suspension balancers were welded to the armored hull. Driving wheels with removable pinion gear rims were located at the rear, and the sloths were identical to the road wheels. The upper branch of the track was supported by three small one-piece support rollers on each side. Track tensioning mechanism - screw; each track consisted of 86 single-ridged tracks 650 mm wide.
Electrical equipment
The wiring in the ISU-152 self-propelled guns of the 1945 model was single-wire, the armored hull of the vehicle served as the second wire. The sources of electricity (operating voltages 12 and 24 V) were the G-73 generator with the RRT-24 relay-regulator with a power of 1.5 kW and four series-connected storage batteries of the 6-STE-128 brand with a total capacity of 256 Ah. Electricity consumers included:
exterior and interior lighting of the vehicle, illumination devices for sights and scales of measuring instruments;
external sound signal and signaling circuit from the landing force to the vehicle crew;
instrumentation (ammeter and voltmeter);
electric triggering of the cannon;
communication equipment - radio station, target designator and tank intercom;
electrician of the motor group - the electric motor of the inertial starter, the bobbins of spark plugs for the winter start of the engine, etc.
Surveillance equipment and sights
All hatches for the entry and disembarkation of the crew had Mk IV periscopes for observing the environment from inside the vehicle (4 in total); several more such devices were installed in the roof of the wheelhouse. The driver monitored through a special periscope device in the roof of the wheelhouse.
For firing, the self-propelled gun was equipped with two gun sights - a breaking telescopic TSh-17K for direct fire and a Hertz panorama for firing from closed positions. The TSh-17K telescopic sight was calibrated for aimed firing at a distance of up to 1500 m. However, the firing range of a 152-mm howitzer-gun was up to 13 km, and for firing at distances over 1500 m (both direct fire and from closed positions), the gunner I had to use a second, panoramic sight. To provide visibility through the upper left round hatch in the wheelhouse roof, the panoramic sight was equipped with a special extension cord. To ensure the possibility of fire in the dark, the scope scales had illumination devices.
Means of communication
Communication facilities included a 10RK-26 radio station and a TPU-4-BisF intercom for 4 subscribers. For more convenient target designation, the self-propelled gun commander had a special one-way light-signal communication system with the driver.
The 10RK-26 radio station was a set of a transmitter, a receiver and umformers (single-armature motor-generators) for their power supply, connected to the on-board power supply network with a voltage of 24 V.
10RK-26 from a technical point of view was a simplex tube heterodyne short-wave radio station operating in the frequency range from 3.75 to 6 MHz (respectively, wavelengths from 50 to 80 m). In the parking lot, the communication range in the telephone (voice) mode reached 20-25 km, while in motion it slightly decreased. A long communication range could be obtained in the telegraph mode, when information was transmitted by a telegraph key in Morse code or another discrete coding system. The frequency was stabilized by a removable quartz resonator; there was also a smooth frequency adjustment. 10RK-26 made it possible to simultaneously communicate at two fixed frequencies (with the abovementioned possibility of smooth adjustment); to change them, another quartz resonator of 8 pairs was used in the radio set.
The tank intercom TPU-4-BisF made it possible to negotiate between the crew members of the self-propelled guns even in a very noisy environment and connect a headset (headphones and laryngophones) to a radio station for external communication.
