Category: Cold War Soviet Heavy Tank Prototypes

Object 718

The Object 718 (incorrectly known as Object 705A). Illustrated by Pavel Alexe

Soviet Union (1945-1948)
Superheavy Tank – Blueprints Only

Megalophilia is a term rarely encountered in the world of military history, yet the phenomenon has been a recurring theme since the beginning of mankind (and, ultimately, wars). Massive weapons of war, envisioned to destroy and conquer any enemy resistance, more often than not failed hilariously, hurting their creators more than the enemy. In popular history, Nazi Germany is the one most often mentioned in regards to this topic. One does not even have to mention the Maus tank, Schwerer Gustav railway gun, Bismarck battleship or the Me 323 Gigant transport aircraft.

The fascination for super-heavy tanks was a common theme prior to the Second World War in several nations and continued into the war. The Soviets had their own fair share of such heresies, such as the Edward Grote’s designs, T-42, KV-4, and KV-5 and more. However, the theme of such heavy tanks slowly died during the war, with the occasional exception. One such exception was the Object 718, often called Object-705A – a 100-tonne super-heavy tank armed with a 152 mm gun and having dozens of centimeters of raw armor, as Soviet tank design moved towards more advanced protection philosophies, such as low silhouettes and steeply angled plates requiring thinner armor.

Yet, with the discovery of the German monster tanks, like the Maus and Jagdtiger, Soviet officials realized that their own heavy tanks were inferior. Although the war was over, further developments on even heavier tanks continued. On the 11th of June, 1945, the GABTU ordered the development of a 60-tonne heavy tank armed with a S-26 130 mm gun and the suspension had to be torsion bars. Kirov Chelyabinsk (ChKZ) answer to this request came in the form of the Object 705 and Object 718, while Kirov Leningrad (LKZ) came in the form of the Object 258, Object 259 and Object 260 (IS-7).

Ironically, on the 2nd of April, 1946, not even a year after the initial request, V.A. Malyshev ordered all heavy tank projects above 65 tonnes to be canceled. However, his request did not hold up in practice, with the 100 tonne Object 705A still being under development and the ultimate versions of the IS-7 weighing over this threshold.

One of the final IS-7 prototypes. While certainly a massive tank, and likely on par with the Object 705A in terms of dimensions, the 100-tonne weight of the Object 718 makes them hard to compare.
Source: Soldat.pro

Design

The Object 718 was a direct evolution from the Object 705, a lighter 65-tonne heavy tank. Both vehicles featured a rear-mounted turret for better balancing of weight and to reduce gun overhang. The Object 705A was to be armed with a colossal 152 mm M-51 gun, using two-part ammunition and two loaders. Weighing 100 tonnes on paper (a figure likely to grow as the design would transition from paper to reality), the armor would have been impressive in raw thickness, yet clever use of angling the side armor plates into a diamond-like shape, the overside protection was increased. To protect itself from infantry, soft-skin vehicles, and even aircraft, a secondary turret was added to the rear of the turret, armed with 2 KPVT 14.5 mm heavy machine guns.

It likely had a crew of 5; commander, gunner, 2 loaders and driver, in a standard Soviet crew layout. The driver sat alone in the hull, while the massive turret encompassed the rest of the four crewmen.

Silhouette of the Object 705. The Object 718 would have likely been similar in layout, just larger.
Source: TiV No. 09 2013

Hull

The exact details of the tank remain mostly unknown. Even a full blueprint of the hull is, so far, missing. Careful analysis and speculation would indicate that the hull was very similar to that of the ‘lighter’ Object 705, but lengthened to fit the larger turret and heftier rounds. The Object 718 would have been 35 tonnes heavier, out of which at least 10 tonnes would come from the larger turret and the 152 mm gun and its ammunition. The remaining 25 tonnes would likely come from thicker frontal armor, overall increased hull volume, and a new engine. This new engine would have been either a diesel or turbinepower output of 2,000 hp, to be able to reach useful speeds. This engine was likely the outcome of post-war Soviet-German work on turbine engines. The transmission was a planetary system automatic. In terms of suspension, a single torsion bar per wheel was used.

One of the main reasons behind the Object 718 was for more armor. Although the exact armor values are yet unknown, comparison to the Object 705 and other heavy tanks of the time (also taking in consideration the weight) results in the frontal hull being at least 220 mm thick, angled at circa 60 degrees. The side armor would be at least 150 mm thick angled inwards at circa 57°. The rear armor angled upwards and was at least 120 mm thick. According to a document on the project, it was to whitstand incoming shells with a muzzle velocity of 1200 m/s.

152 mm M-51

One of the few certain things about the Object 718 is the main armament, the M-51 152 mm gun, developed at Factory No.172 as a tank variant for the 152 mm M-31. In terms of ballistics, it was mostly identical to the regular M1935 Br-2 howitzer, but with considerable upgrades in other areas. Firstly, the archaic breech block door was replaced with a more modern horizontal sliding breech block. It also received the famous TsAKB style slotted muzzle brake, which could absorb up to 70% of the recoil, decreasing the need for powerful recoil absorption pistons. It still had two recoil absorption cylinders and two brake cylinders to absorb recoil, but these were considerably lighter, and in tandem with the muzzle brake, decreased the recoil from 1,400 mm (on Br-2) to 520 mm. Very noticeable is the sheer volume of the breech, which was needed to offset the long barrel. One prototype of the gun was built and passed factory tests in the summer of 1948.

Soviet slotted muzzle brake compared to a German-style muzzle brake.
Source: Tank – The Military Publishing House of the Ministry of Defense of the USSR

Turret

The only known blueprint is of the turret, a lengthened variant of the original. It almost resembles a UFO-like shape to increase the angle at which most projectiles would hit the surface. To cut down on the weight, the rear and top has been limited to around between 30 and 50 mm of armor, while the front has over 250 mm thick. The mounting of the M-51 gun is also very clear, showing the lack of gun depression. It is also significantly longer than the original to compensate for the larger recoil and potentially even turret-stowed projectiles.

On the roof of the turret, the turret ring of a second, smaller turret can be seen. This was a brand new design feature incorporated on some heavy ChKZ designs, first incorporated on the Object 726, and apparently, also the Object 718 (as the two were likely designed simultaneously). The turret resembles contemporary American tank secondary turrets, having a hemispherical shape. It was armed with a pair of 14.7 mm KPVT heavy machine guns. It was far too small for a crew member to fit in it, and was probably mechanically controlled from within the turret by one of the loaders. The idea was not entirely dropped after the cancellation of these super-heavy tanks. The Object 777 still used a similar turret, but with only one turret KPVT. For the turret traverse, ChKZ created hydraulic drives in 1948, but they were deemed unsuccessful and shortly after, the entire project was canceled.

Cutout view of the turret showing its armor thickness and the M-51152 mm gun.
Source:TiV No. 09 2013

The Object 726 model 1947, designed in parallel with the Object 705A, but weighing less than half of it, at just 48 tonnes.
Source: TiV No.10 2014

The 4-tracked Object 726 mod. 1948. The second turret on top was likely very similar to that of the Object 705A.
Source: TiV No.10 2014

Suspension & Running Gear

As this would be amongst one of the heaviest tanks ever designed by SKB-2, seriously strong suspension and running gear were needed. An entirely new set of large-diameter wheels was designed for the program. The Object 705 likely used the same wheels.

As per the blueprints, the wheels were steel-rimmed, clamped between two stamped steel lids. This left a distinctive space between the rim and the interior of the wheel. The same wheel system is mirrored on the other side. The two parts are held together with large bolts, creating a space for the track guides.

The suspension consisted of relatively simple torsion bars, running from the wheel straight into the narrow hull. The torsion arms were mounted in opposite facing pairs, instead of facing the same direction, like on other torsion bar sprung tanks. The spacing in-between each torsion bar pair was enough to fit another torsion bar, as seen in the blueprints.

Side cutout view of the wheels used on the Object 718. These were likely designed specifically for the project.
Source: TiV No. 09 2013

Side cutout view of the torsion arm and torsion bar attachment on the Object 705A. Note the steep angle of the hull.
Source: TiV No. 09 2013

Cutout top view (left) and cutout side view (right) of the torsion bar arrangement. Note how they are mounted in opposite facing pairs, an unusual solution.
Source: TiV No. 09 2013

A Maturing Tank Force

Although being under development for almost 3 years (a very long time for Soviet standards), the Object 718 never got particularly far. Both the GABTU and Soviet officials began discouraging especially heavy tank projects. Even internally, ChKZ was focusing on other, more fruitful projects, like the IS-3 and IS-4 or various self-propelled guns.

It also started to become clear that heavy tanks were beginning to get outperformed by medium tanks. Development of the T-54 had reached an advanced stage in the late 1940s, with better mobility and lower weight, yet the firepower and armor were not far behind.

In contrast, heavy tanks, especially super heavy ones, like the Object 718, would hinder the Soviet tank force rather than improving it. Such a heavy tank, not only requiring massive amounts of money and resources poured into developing, production and maintenance, would also require an entirely new logistical force, from rail cars to mobile bridges.

Ultimately, the Object 718, alongside its lighter brother the Object 705 and its LKZ rival, the IS-7, all got their lives cut short by the Council of Ministers of the USSR on the 18th of February, 1949, where it was requested that the development of all heavy tanks and SPGs weighing over 50 tonnes should be terminated.

The Soviet Union would ‘force itself’ into adopting a new heavy tank into service, despite the rather large disappointments in the form of IS-3 and IS-4. This would be the T-10, one of most modern heavy tanks of the time. Whether or not it was necessary is up for debate. The British Conqueror heavy gun tank and American M103 heavy tank entered service in the mid to late 1950s.

Soviet heavy tank development continued into the 1950s, with very advanced designs, such as the Object 279 and Object 770, far ahead of any contemporary Western heavy tank. They were, however, redundant as by now, new Soviet medium tanks could easily outperform any heavy tank using new technologies. On 22nd July 1960, Nikita Kruschev forbade the development and adoption into service of all tanks weighing over 37 tonnes. Thus, all heavy tank development stopped.

The Object 718 (incorrectly known as Object 705A). Illustrated by Pavel Alexe

Object 718 Specifications
Dimensions (L-W-H)	7.2 – 3.7 – 2.4 m
Total Weight, Battle Ready	100 tonnes
Crew	5 (Commander, Gunner, Driver & 2 Loaders)
Propulsion	2000 hp diesel/turbine engine
Speed	35 km/h (hypothetical)
Range	Torsion bar, 7 wheels per side
Armament	152 mm M-51 gun coaxial 14.5 mm KPVT heavy machine gun Secondary turret w/ dual 14.5 KPVT
Armor	Hull armor: Approx. Front top plate: 220 mm at 55° Front bottom plate: 200 mm at -50° Side plates: 150 mm at 57° (inwards) Rear plates: 120 mm Top: 30 mm Belly: 30 mm
Total Production	0, blueprints only

Sources

Domestic armored vehicles 1945-1965 Soljankin, A.G., Pavlov, M.V., Pavlov, I.V., Zheltov
TiV No.10 2014 A.G., Pavlov, M.V., Pavlov
TiV No. 09 2013 A.G., Pavlov, M.V., Pavlov
https://yuripasholok.livejournal.com/2403336.html
The genius of Soviet artillery. Triumph and tragedy of V. Grabin – Shirokorad Alexander Borisovich

Cold War Soviet Heavy Tank Prototypes

Object 705 (Tank-705)

Soviet Union (1945-1948)
Heavy Tank – None Built

Background

In the latter stages of the Second World War, a great deal of Soviet tank design focused on improving existing heavy tanks, such as the IS-2, and building entirely new designs. This resulted in a number designs, with various degrees of performance and success, such as the IS-6 and IS-3.

After the discovery of the Maus and an in-depth look at German projects, the Soviets thought that the new imminent war against the West would require serious heavy tanks, with more armor and better guns than what they currently had. So, on 11th June, 1945, the GABTU (Main Directorate of Armored Forces) requested the development of new heavy tanks armed with the 130 mm S-26 gun, weighing 60 tonnes, and using torsion bar suspension. This led to a series of complex heavy tank and SPG designs, which would eventually lead to the heaviest Soviet tank of all time – the IS-7.

Developed and built at Kirov plant Leningrad after almost 5 years of development, the IS-7 is often regarded as the peak of heavy tank design. However, the Soviets officials’ displeasure with such heavy vehicles led to the cancellation of design and development of all AFVs weighing over 50 tonnes. The act came into practice at the meeting of Ministers of the Soviet Union on 18th February 1949, ending the IS-7’s life.

But few know of the other Kirov plant’s design, meant as a rival to the IS-7 (Object 260). Kirov Chelyabinsk (ChKZ) and Kirov Leningrad (LKZ) had been rivals for years, and so there are many parallel projects by the two factories. Their design was called Tank-705 as per the blueprints, but would eventually be known as the Object 705. The project started in June 1945 and was terminated in 1948, alongside other heavy tanks.

Development first began in June 1945, immediately after the discovery and analysis of German heavy AFVs. This triggered a series of projects over several design bureaus and factories. For ChKZ, the IS-3 was proving to be a success, and the IS-4 (Object 701) was soon to enter production. In contrast, LKZ had just lost several programs, most importantly, the IS-6. But the experience gained from it led to a series of promising designs. Fast forward a couple of years, and LKZ had full-scale mock-ups of one of the best heavy tanks ever designed, and was beginning prototype production. Meanwhile, Chelyabinsk and its design institute, SKB-2, had a series of disappointments, especially in the IS-4. In parallel, ChKZ had been working on the Object 705 and 718 (also called Object 705A) designs, but, as they were not deemed crucial or urgent, progress was slow. Further problems came with the 80th order on 2nd April, 1946 from V.A. Malyshev, when the mass of heavy tanks was limited to 65 tonnes. While the Object 705 still fit the criteria, the Object 718 did not. Yet work continued regardless.

The 1946 LKZ Object 260 was very similar to the Object 705 in terms of capabilities, although it came slightly later.
Source: Domestic armored vehicles 1945-1965

Design

All that remains of the Object 705 are two drawings, one general silhouette and one detailing the armor profile and thickness. The tank was meant to weigh around 65 tonnes, use heavily sloped armor plates, and mount a thick cast turret mounted to the rear. This was done not only to use the engine as protection, but to also offset the length of the gun. What exact engine it would have used is unknown, but likely one between 750 and 1,000 hp for it to reach the expected 40 km/h. The transmission was a planetary automatic design. It is important to highlight is the sheer size of the tank design, being 3.6 m wide and 7.1 m long (just the hull), dwarfing the IS-4 (6,682 (hull only) x 3.26 x 2.4 m).

Dark silhouette view of the Object 705 with the dimensions. This is the only known drawing showing the complete view of the vehicle.
Source: TiV No.9 2013

The crew was probably of 4: commander, gunner, loader, and driver. The crew were all situated inside the turret, with the gunner on the left side of the gun, the loader behind, and the commander on the opposite side. The driver was placed inside the turret, and would have a pivoting station, which allowed to always face the front of the hull. This was not the first, nor last, time Soviet designers would try to incorporate this idea. Two of the periscopes were mounted on the turret roof, the one on the left side was to be used by the commander and the one on the right was to be used by the loader. The driver also had his own periscope, but mounted further forwards. The gunner likely did not have his own periscope, and had to rely on his sight and/or crew callouts.

Armament

In terms of main armament, it is uncertain what the Object 705 would have used. Some sources claim it was a high-power 122 mm gun, while others state directly that it was a BL-13 122 mm gun. This was no new and revolutionary gun by the late 1940s, it was actually developed by OKB-172 in 1944, with several upgrades made later, such as the BL-13T and BL-13-1. The rate of fire varied between the different versions of the gun, as the upgraded variants had a mechanical gun rammer, but it was between 5 to 10 rounds per minute. Such long reload times were caused by the two-part ammunition. Secondary armament consisted of a coaxial 12.7 mm DhSK heavy machine gun mounted on the right side of the gun and potentially a roof-mounted DhSK.

However, a larger caliber gun (130 mm) is not entirely out of the equation, as later IS-7 designs used such a caliber, and the diameter of the barrel on the silhouette of the tank is thicker than that of a 122 mm gun. To back this theory up, on 11th June, 1945, specifications clearly stated that the gun on the new heavy tank should be a 130 mm S-26, the land version of the naval B-13. At the same time, the BL-13 was already deemed obsolete when facing German heavy tanks.

The S-26 was developed between 1944 and 1945 at TsAKB by head engineer V.G. Grabin. It was largely based on the B-13 130 mm naval gun (not to be confused with the previously discussed BL-13) with a semi-automatic horizontal sliding breech lock, slotted muzzle-brake, and barrel smoke evacuator. Rate of fire was around 6 to 8 rounds per minute. The shells weighed 33,4 kg and had a muzzle velocity of 900 m/s.

Ammunition was stored along the angled sidewalls, a solution present on most Soviet tanks with angled sidewalls. The exact number of rounds stowed is hard to estimate, but most tanks using similar guns carried around 30, split into charges and projectiles.

Digitally blue-tinted drawings of the BL-13 122 mm gun. Note that the barrel length proportions are not to scale.
Source: Warspot

S-26 130 mm gun. This was the gun GABTU requested to be mounted on the heavy tank in the summer of 1945.
Source: Domestic armored vehicles 1945-1965 Soljankin, A.G., Pavlov, M.V., Pavlov, I.V., Zheltov

Armor

A study of the drawing showcases the armor thickness and the complex arrangement of the armor plates. The upper frontal plate consists of one 140 mm thick plate, angled at 60°. On the top corners, it is met by a plate angled upwards across the upper side of the engine bay. The lower plate is also 140 mm, angled 55º from the y-axis. In terms of side armor, a very interesting idea was adopted. The two 130 mm armored side walls were brought inwards at a steep 57° angle, creating a diamond-like shape from the front. SKB-2 had used angled walls on the IS-3, but only on a minimal level for more interior space. Instead, such diamond-shaped sides were first used by the Kirov Leningrad plant on the first IS-7 design, the Object 257. This option provided excellent side protection from conventional projectiles, but also increased mine resistance, as the blast force was directed outwards. All this came as a trade-off for interior space. A major issue with this design feature is the narrow-angle created at the bottom of the tank. This space is very hard to use, and essential components like engine and transmission have to be moved up, making the tank taller. Another big issue was the suspension, namely where exactly to put it. On the Object 257, the issue was resolved by designing a brand new external suspension, using volute spring bogies like on the Sherman tank. The exact solution on the Object 705 is, naturally, unknown, but a handful of different options could have been used.

The turret was rounded and flat, creating angles between 50º and 57º. Armor varied greatly depending on the strike face, with the thickest front part being 140 mm and the thinnest roof section being 20 mm.

Cutout armor profile of the Object 705. Note the protrusions from the hull for the final drive.
Source: TiV No.9 2013

Roadwheels and Suspension

One of the most curious aspects of the design was its wheels. Seven large steel-rimmed wheels per side were used. A hint comes from SKB-2’s other super heavy tank project at the time, the massive 4-tracked Object 726 behemoth, which featured among other wheel and suspension ideas, large, steel rimmed roadwheels. There is a serious possibility of them being used on the Object 705 as well. These wheels would later become a mainstay in heavier ChKZ designs, such as the Objects 752, 757, 770, and 777, the latter two using hydropneumatic suspensions.

Steel-rimmed roadwheel from the Object 770 at Kubinka.
Source: Magic Models

Yet blueprints of the Object 718 show a slightly different set of wheels. These were drawn as steel rimmed and with deep spacing between the rims and rest of the stapled steel lids. The wheels seem to have been mostly unique to the Object 705A. The Object 705 could have used the same wheel design or something else, as the lower weight allowed for more playroom in terms of weight thresholds on the components.

Cutout view of the roadwheel used on the Object 718. These were different to other large-diameter wheels used by ChKZ.
Source: TiV No.9 2013

Implementing conventional torsion bars running across the length of the hull initially seems challenging due to the hull floor being so narrow, due to the inwards angled side walls. Yet the simple solution to this was that the tank hull was simply very wide. This allowed the side walls to keep a steep angle while still allowing for a sufficiently long torsion bar to be mounted. Such issues had been encountered by Soviet engineers both previously and later, with a variety of solutions such as bundled torsion bars, lifting the torsion bars higher up into the hull, or moving the torsion arm on the outside of the wheel.

Cutout view of the suspension (single torsion bar) used on the Object 705A. Note the angle of the hull.
Source: TiV No.9 2013

Object 705A

At some point during the development of the Object 705, an even heavier variant was designed. It would have weighed 100 tonnes and be armed with the 152 mm M-51. Just the mass alone would place the Object 705A as one of the heaviest Soviet tanks designed post-war. Yet blueprints only show specific details, such as the turret, suspension, roadwheels, and transmission. A lack of hull blueprint makes it hard to legitimize it as a complete design, and it is entirely possible that its hull never got drawn to begin with. This naturally leaves the proposal in a lot of mystery and up to significant speculation.

Conclusion – Weight Shaming

With so little information available, it is hard to properly judge the capabilities of the Object 705 and 718, even when compared to the different variations of the IS-7. The vehicles were likely designed between 1947 and 1948, at which point the BL-13 was already outclassed (Kirov Leningrad had used it on the IS-6 and other projects in 1945). So, in that respect, the Object 705 fell behind the IS-7. Yet in terms of armor, it was on par, if not even better protected than the most advanced IS-7 variant. As for the Object 718, the lack of information prevents any conclusions to be drawn, with the one and main issue being the weight of 100 tonnes. When discussing both the Object 260s and Object 705s, it is generally clear that such heavy vehicles could prove vulnerable and simply too heavy for effective battlefield use. The heaviest Soviet tank in service, the IS-4, weighed 53 tonnes and was still considered overweight and too slow. Thus it seems almost natural that the Soviet government saw the limitations and waste of resources devoted to such heavy vehicles. The final nail in the coffin for these designs was the cancellation of all AFVs above 50 tonnes on 18th February, 1949.

Object 705 rendition, illustrated by Pavel ‘Carpaticus’ Alexe

Object 705 specifications
Dimensions (L-W-H)	7.1 – 3.6 – 2.4 m
Total Weight, Battle Ready	65 tonnes
Crew	4 (Commander, Gunner, Driver & Loader))
Propulsion	1,000 hp engine of unknown type
Speed	40 km/h (hypothetical)h
Armament	130 mm S-26 or 122 mm BL-13 gun coaxial 12.7 mm DShK heavy machine gun
Armor	Hull armor: Front top plate: 140 mm at 55° Front bottom plate: 140 mm at -50° Side plate: 100 mm at 57° Top: 20 mm Belly: 20 mm
Total Production	Blueprints only

Sources

Cold War Soviet Heavy Tank Prototypes

K-91 (Rear-Mounted Turret)

Post author By Pavel Alexe
Post date October 4, 2021
No Comments on K-91 (Rear-Mounted Turret)

Illustration of the K-91 with a rear mounted turret. Illustration by Pavel Alexe, funded through our Patreon campaign.

Soviet Union (1949)
Heavy Tank – Blueprints Only

After the Councils of Ministers of the USSR had terminated all heavy tank projects of 50 tonnes and more in 1949, many Soviet design bureaus and factories saw their opportunities to design new vehicles. One of these was OKB IC SV (Design Bureau of the Engineering Committee of the Armed Forces) led by Anatoly Fedorovich Kravtsev. They designed three vehicles, two heavy tanks and one SPG, under the name K-91.

Development

The Councils of Ministers of the USSR stated on 18th February, 1949 in the decree No.701-277§ that all design, development and production of heavy tanks heavier than 50 tonnes shall end. Kravtsev’s team at OKB IC SV set to work almost immediately to design some lighter heavy tanks that would replace both heavy and medium tank classes, whilst also being the platform for Self-Propelled Guns (SPGs). The lead engineer was I.T. Levinov and the designer was Matyukhin.

The bureau designed three vehicles, named K-91. The first was a heavy tank with a large, front-mounted turret that encompassed all 4 crewmembers. The second was a rear-mounted turret heavy tank that featured an odd-shaped hull and an autoloader. There was also an SPG.

Design

The second variant of the K-91 heavy tank design was less elaborately depicted than the first (there is no knowledge on the chronological order in which the tanks were designed, and are numbered as such simply to differentiate them). From the 4 available drawings, the tank had the turret mounted in the rear of the hull and the engine and transmission were mounted all the way in the front. This offered a lot more protection to the crew, as the mechanical components acted as a form of armor against fragments following penetration. The crew, consisting of 3 men, were all seated in the turret. Most curiously, the hull had a very odd shape. From above, it was almost shaped like an egg, while from the side, it was flat. This awkward hull design, combined with the stowage of ammunition in the turret, resulted in a lot of empty space in the hull.

Side view of the K-91 rear-mounted proposal. From this angle, the hull seems very flat and unremarkable.
Source: Technic and Weapons No. 9, 2013, M.V. Pavlov, I.V. Pavlov Domestic armored vehicles of 1945-1965, page 35

Crew

As aforementioned, the tank had a crew of 3; commander, gunner, and driver. They were all seated in the turret. The gunner sat on the left side of the gun and only had his main gun sight as vision, having to rely entirely on the commander’s calls. The commander sat right behind him, surrounded by the ammunition, and had only one periscope to view out of. He had a protrusion from the otherwise semi-spheric turret, akin to a commander cupola. This is where the periscope was mounted and, most likely, this was his entry and exit hatch. The gunner most likely also used this hatch. The commander was close to the gun breech, potentially meaning that he could manually load the gun if the automated system failed.

Lastly, the driver was seated on the right side of the gun. Since he was seated in a rotating turret, he was given a pivoting device that would allow him to remain facing the front of the hull regardless of the rotation of the turret. This, however, makes it unclear if the turret was able to perform a full 360° rotation. Right behind him was the plethora of ammunition. Since the driver was placed quite high in the turret, he also had a protrusion from the rounded cast turret.

From this angle, the bizarre, almost UFO-like hull shape is clear. Despite it having no vertical angling, the Z-axis angling gave it very good LOS protection.
Source: Technic and Weapons No. 9, 2013, M.V. Pavlov, I.V. Pavlov Domestic armored vehicles of 1945-1965, page 35