SU-85

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SU-85
SU-85 tank destroyer in Polish Army Museum.
Type	Tank destroyer
Place of origin	Soviet Union
Service history
In service	1943 - ? (out of service)
Production history
Designer	Lew S. Trojanow
Designed	1943
Produced	mid-1943 - late 1944
Number built	2,050
Variants	See Variants section
Specifications
Weight	29.6 tonnes
Length	8.15 m (overall) 6.10 m (hull only)
Width	3.00 m
Height	2.45 m
Crew	4 (commander, driver, gunner, loader)
Armor	45 mm
Primary armament	85 mm D-5T gun
Secondary armament	none
Engine	V-2 12-cylinder diesel 503 hp (375 kW)
Power/weight	17 hp/tonne (12.7 kW/tonne)
Suspension	Christie
Ground clearance	400 mm
Fuel capacity	540 l 810 l - 900 l (with additional fuel tanks)
Operational range	400 km (road)
Speed	55 km/h (road)

The SU-85 was a Soviet self-propelled gun used during World War II, based on the chassis of the T-34 medium tank. Unlike earlier Soviet self-propelled guns which were meant to serve as either assault guns or anti-tank weapons, this vehicle was a dedicated tank destroyer. The designation SU-85 is derived as follows: 'SU' stands for the Russian: Samokhodnaya Ustanovka - self-propelled carriage, while "85" signifies the bore of the vehicle's armament, the 85 mm D-5T gun.

[edit] Development history

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During the early phases of World War II, Soviet tanks such as the T-34 and KV-1 had sufficient firepower to destroy any German tank they encountered. However, in the fall of 1942, Soviet forces first encountered the German Tiger tank. Tests on captured tanks revealed that the 76.2 mm guns used in the T-34 and KV tanks could penetrate the Tiger's armour only from dangerously short ranges.^[1] By spring 1943, the Soviets also knew about the existence of the German Panther tank, although the Panther was not seen in combat until July 1943 during the battle of Kursk. The fielding of these new-generation German vehicles meant that the Red Army required a more powerful anti-tank gun.

Additional testing indicated that the 122 mm M-30S howitzer mounted on the SU-122 self-propelled howitzer was ineffective against the Tiger I's armour. Although it could penetrate the Tiger's armour by using its HEAT rounds, the curved trajectory of the projectiles and a very poor rate of fire made the SU-122 an easy target for the Tiger's 88 mm gun. ^[1] Further tests showed that the best guns to consider for further development were the 85 mm 52-K anti-aircraft gun and the 122 mm A-19 field gun. In May, 1943, a design bureau lead by chief designer Petrov was ordered to develop a new tank destroyer armed with this gun and utilizing a modified SU-122 chassis.

Simultaneously, the TsAKB (a design bureau a chief designer of which was V.Grabin) started design works on changing the armament of the SU-122 to the already existing 85 mm S-18 gun, which was originally developed for KV heavy tanks. Since th gun was already getting obsolete, it was first improved. The improvement consisted of a new mantlet and new cradle. After the said improvements were carried out, the S-18 gun was delivered to the Uralmash factory where the SU-85 was designed in 1943 by a design bureau the chief designer of which was Lew S. Trojanow. The designers couldn't find a way to install the 85 mm S-18 gun in the casemate of the SU-122 because of the size of the gun breech which was far too big. Because of this Uralmash tried to stop any further design works on this vehicle because it was leading to a modification of the entire hull which was extremely expensive at the time when simplicity and cheapness were very important to Soviet military and heavy industry. Although the designers had their own opinions about the vehicle they were supposed to design the Soviet High command forced them to continue working on the project as they were desperate for anything that stood a chance against new German tanks. Two quite different prototypes were built as a result of all this. SU-85-I^[1] which was the first SU-85 prototype used a standard hull of the SU-122, but it was fitted with a new cradle and a new pig-snout-type ball mantlet for the gun. At first a coaxial machine gun was proposed to give the new vehicle some way to protect itself from infantry attacks. This however was abandoned because of lack of space. SU-85-IV^[1] which was the second prototype also utilized the SU-122 chassis as well, but it also had a larger ball mantlet, different from the one used in SU-85-I. Both prototypes used the problematic 85 mm S-18 gun.

At the same time works on mounting the 85 mm D-5S gun designed by Petrov into the casemate of SU-122 started. At first the D-5S gun was thought to be only a side project until the drawbacks of the S-18 were corrected. The two guns were put on comparative trials on which surprisingly the D-5S showed not only the same ballistic capabilities as the S-18, but also was much more reliable and generally unperformed the S-18.^[1] Although the D-5S gun successfully passed all of the trials, the existing cradle of the gun made it impossible to fit a telescoping sight to it. To solve this problem a new sight was developed. It received a designation TSh-15. Another prototype was built. This one was armed with the D-5S gun and also utilized the new TSh-15 sight as well as a new ball mantlet design. It was designed SU-85-II^[1], which apart from the new gun and a new TSh-15 sight, also introduced a new ball mantlet design. This prototype was put on comparative trials against the SU-85-I like the SU-85-IV was before it which was abandoned because of several serious drawbacks. The SU-85-II proved to be supierior to SU-85-I and therefore was accepted for service in the Red Army as the SU-85 tank destroyer after several changes which included changing the gun to D-5T.^[1][2]

In further design work aimed at improving the SU-85, the SU-85-III prototype was built. It had a modified commander's cupola.^[2]

[edit] Description

The SU-85 was a modification of the earlier SU-122 self-propelled howitzer, essentially replacing the 122 mm M-30S howitzer of the SU-122 with a D-5T high-velocity 85 mm antitank gun. The 85 mm gun could penetrate the side armor of a Panther or Tiger at long range, and do so from a small, highly mobile vehicle with all-around armor protection. The new gun required a different mounting featuring a ball-shaped mantlet.

[edit] Production history

SU-85 production started in mid-1943, with the first vehicles reaching their units by August. When the up-gunned T-34-85 medium tank entered mass production in the spring of 1944, there was no point in continuing production of a tank destroyer without superior firepower (Zaloga 1984:181, Perrett 1987:84), so SU-85 production was stopped in late 1944 after 2,050 vehicles had been produced. It was replaced on the production lines by the SU-100 tank destroyer, armed with the more powerful 100 mm D-10S gun.

There were two versions: the basic SU-85 had a fixed commander's cupola with a rotating periscope and three vision blocks; the improved SU-85M had the same casemate as the SU-100, with a commander's cupola as used on the T-34-85.

[edit] Service history

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SU-85 tank destroyer of the Polish 13th Self-Propelled Artillery Regiment. This vehicle is missing its right first road wheel and its fenders.

The SU-85 entered combat in August 1943. It saw active service in Soviet, Polish and Czechoslovak forces on the Eastern Front until the end of the war. It was obsolescent by 1945, and was withdrawn from active service not long after the war, to be exported to many Soviet clients states in Europe and elsewhere.

The SU-85 was used by Bulgaria,^{[citation needed]} Romania,^{[citation needed]} Hungary,^{[citation needed]} Yugoslavia,^{[citation needed]}, where it was withdrawn to reserve stocks by the mid-1980s, but remained in service longer in North Korea (Perrett 1987:84) and Vietnam (Perrett 1987:84). The similar SU-100 remained in service much longer, and some SU-85 and SU-100 were converted and used as command and recovery vehicles (Perrett 1987:85).

In addition to the Second World War, the SU-85 was used in combat by North Korea in the Korean War, by Egypt in the 1956 Suez Crisis, and by both Egypt and Syria in the 1967 Six-Day War (Perrett 1987:84).^{[dubious – discuss]}

[edit] Variants

[edit] Former Soviet Union

• SU-85-I - First SU-85 prototype with a standard hull of the SU-122 as well as a new cradle and a new pig-snout-type ball mantlet for the gun. Armed with 85 mm S-18 gun.^[2][1]
• SU-85-IV - Second prototype also with a standard hull of the SU-122 but it had a larger ball mantlet, different from the one used in SU-85-I. Armed with 85 mm S-18 gun.^[2][1]
• SU-85-II - Third SU-85 prototype with the new 85 mm D-5S gun, a new TSh-15 sight and a new ball mantlet design.^[2][1]
  • SU-85 - Main production model armed with 85 mm D-5T gun.
    • SU-85M - SU-85 with the casemate from the SU-100 tank destroyer, which was larger and could carry up to 60 rounds instead of 48. It also had the same commander's cupola as the one used in the T-34-85.^[2][1]
    • SU-85T - SU-85 tank destroyer converted into an ARV.^[2]
• SU-85-III - Fourth SU-85 prototype with a modified commander's cupola, with direct vision slots and covers.^[2]

[edit] Poland

• WPT-34 (1960s) - Polish repair and maintenance vehicle with a superstructure replacing the casemate, a crane, a large-diameter telescoping snorkel for deep fording operations as well as a large-spade type earth anchor in the rear. It was converted from SU-85 tank destroyers as well as T-34 medium tanks and SU-100 tank destroyers.^[2]

[edit] References

• Perrett, Bryan (1987). Soviet Armour Since 1945, London: Blandford. ISBN 0-7137-1735-1.
• Zaloga, Steven J., James Grandsen (1984). Soviet Tanks and Combat Vehicles of World War Two, London: Arms and Armour Press. ISBN 0-85368-606-8.

[edit] See also

• List of Soviet tanks - covers all periods

[edit] External links

Wikimedia Commons has media related to:

SU-85

• SU-85 at WWIIvehicles.com