SU-101 and SU-102 Self-propelled Guns - Design Characteristics

Design Characteristics

The Uralmash-1 was a turretless casemate vehicle with a flat engine compartment in the front and a boxxy elevated crew compartment in the rear, mounted on a suspension taken directly from the T-44 medium tank. The main gun protruded from the crew compartment and arched over the vehicle's engine. Thus, even a long-barreled gun only slightly increased the overall vehicle length, improving maneuverability and eliminating one of the SU-100's major deficits. This layout was referred to as of the Ferdinand sort ("по типу Фердинанда") in internal Soviet documents, referencing the German heavy tank destroyer Ferdinand faced by Soviet forces at that time, which was build in a similar fashion. The layout also spread the vehicles weight more evenly among the road wheels, addressing the mechanical issues faced by the front heavy SU-100.

The crew of 4 consisted of vehicle commander, gunner, loader and driver. While the driver was seated in the front left side of the vehicle next to the engine, the rest of the crew was placed in the crew compartment around the main gun in the rear. Access to the vehicle was provided by a door in the rear of the vehicle. This additionally increased crew survivability, as in the case of an emergency evacuation the crew could exit the vehicle without exposing themselves to enemy fire as much as an evacuation through the roof hatches would require.

The Uralmash-1's hull was made from plates of rolled homogeneous armour, welded together in a sloped fashion to give it improved protection. The frontal plates had a thickness of 90 mm, the sides 75 mm and the rear 40 mm. During firing tests with the empty hull, the vehicle's protection proved to be superior to the much heavier ISU-152 tank destroyer as well as the IS-2 heavy tank.

The SU-101 prototype with the 100 mm D-10S gun came with a combat loadout of 35 rounds. While the horizontal gun traverse at 22.5° and the vertical elevation at 18° were entirely sufficient, the engine compartment limited the gun depression at a very meagre -2°, almost eliminating the vehicle's ability to go hull-down. The bigger 122 mm D-25S gun of the SU-102 prototype, with 28 rounds of ammunition, was even more limited in its gun traverse, not being able to depress the gun further than 0.24° with an elevation of 18.5° and horizontal traverse of 19°. The very limited gun depression is one of the fundamental drawbacks of a rear-mounted gun layout.

The Uralmash-1's vehicle commander was additionally provided with a 12.7 mm DShK machine gun mounted in his roof hatch for use as an anti-aircraft weapon. The DShK ammunition loadout was 450 rounds.

The Russian designation "SU", meaning Samokhodnaya Ustanovka or self-propelled gun, is a rather diffuse term that was equally applied to vehicles which in combat fulfilled the roles of dedicated tank destroyers, infantry-supporting assault guns, and even indirect-fire artillery, i.e. self-propelled howitzers. The SU-101/SU-102 as a replacement for the SU-100, which was mainly used as tank destroyer, was potentially intended to fulfill the latter's role. The 100 mm D-10S of the SU-101 was a dedicated tank gun with capable kinetic energy armour-piercing rounds. The 122 mm D-25S of the SU-102 against that had originally been developed as an artillery howitzer to be used with high explosive rounds. However, in the course of the war, the gun had also proved to be a very effective anti-tank weapon, capable of knocking out even heavy German tanks, and armour-piercing kinetic energy ammunition had been developed to augment this battlefield role. As such the gun was already in use with the heavier ISU-122 tank destroyer.