Lev Izraelevich Gorlitskiy started the war in the role of the chief designer of artillery at factory #185 in Leningrad. From June to October of 1941, his department was tasked with placing weapons into long-term fortified positions to protect approaches to Leningrad. In October, the factory was evacuated to Sverdlovsk and became a part of the Ural heavy machinebuilding factory.
One year later, in October of 1942, Gorlitskiy headed a newly formed design bureau at Uralmash, tasked with developing SPGs. A very sharp need in them was felt after new Tiger tanks appeared on the battlefield.
Three SPGs developed by Lev Izraelevich in 1942-1944 contributed significantly to victory over Germany.
Gorlitskiy's first creation was the SU-122, an assault gun. A 122 mm howitzer was placed in an immobile casemate. The gun shot HE, later HEAT ammunition. Despite numerous drawbacks, the vehicle was received well. The gun was effective against soft targets and personnel, but the low muzzle velocity did not allow it to effectively engage tanks.
SU-85 (1943) was a specialized SPG, designed to fight German Tigers and Panthers. its 85 mm gun could penetrate their armour from short and medium distances, but could be ineffective at ranges over 800 meters.
In 1944, Gorlitskiy's design bureau developed a tank destroyer with a 100 mm gun: the SU-100. It was the most dangerous enemy of all German vehicles. The only tanks it had problems with at long distances were King Tigers, Jagdtigers, and Ferdinands.
The design of all of the above vehicles was classic for Soviet SPGs: a chassis of a serial tank, casemate in the front, decent frontal armour. This layout was simple and technologically sound, but had two drawbacks. One was that the front of the chassis was overloaded, which decreased reliability of the suspension. The second was that long anti-tank guns made it more likely that the gun will stick into the ground in an unlucky move.
These issues could not be resolved in the classic style, a new approach was necessary. Layouts with a rear fighting compartment were tested, but Gorlitskiy had even more novel ideas.
New Look at SPGs
Gorlitskiy wrote in his memoirs that he wanted to make a vehicle "with long term prospects, compatible with all modern requirements". Under the new system of SPGs, the vehicles would be a part of a support class. These SPGs had to be universal, with the ability to destroy enemy tanks, fortifications, and personnel equally well.
The first step of Gorlitskiy's design bureau was to carefully study domestic and foreign experience. German Waffentrager vehicles aroused their interest. These vehicles consisted of a tracked mount with a gun on top, protected only by a light shield. This was Gorlitskiy's inspiration for the SU-100P or "item-105".
The SU-100P was not like any fully armoured Soviet SPG. Gorlitskiy bet on mobility and firepower. A new chassis was designed with armour no thicker than 15 mm. It carried a D-10S gun on a rotating mount. The gun was covered by a small open cabin and had an unheard of horizontal gun traverse: 155 degrees. The vehicle could fire from direct or indirect positions.
The SU-100P chassis was made from scratch, In a rare case among Soviet designs, the engine compartment was located in the front. A new gearbox gave the tank's driver control at any speed and on a road of any complexity. For the first time in Soviet tank building, rubberized track link bearings were used, increasing the lifespan of tracks.
In 1955, after trials and improvements, the SU-100P was accepted by the Soviet Army, but only a small number was made: no more than 24 vehicles. The main reason for this was the "rocket boom" that reigned during Khrushchev's rule.
The SU-100P's chassis had better luck. It turned out to be very much in demand. Even during trials, the chassis was borrowed by two other vehicles: the SU-152G and SU-152 "Taran". Later, the chassis was lengthened to 7 road wheels and used by many vehicles. Among them are the BTR-122 tracked APC, Krug AA missile platform, and other launchers. The chassis was also used by the Akatsiya SPG, Tulpan self propelled mortar, and Giatsint-S 152 mm SPG.
Article author: Vladimir Pinayev
Original article available here.