Categories
Cold War Soviet Prototypes

Object 911B

Soviet Union (1963-1964)
Light Tank – 1 Prototype Built

The evolution of warfare and technologies in the years following the conclusion of the Second World War had a major impact on the way warfare would be conducted in the future. With the proliferation of nuclear armament, radiation protection became a major feature for new vehicles. Operations in the Second World War also showed that river crossing could sometimes prove difficult, as these could form major natural blocking points that most armored vehicles would find impossible to cross outside of a few heavy and sturdy bridges. Amphibious vehicles would prove to be a major asset to cross rivers even outside of these bridges, or in the event that they were destroyed or heavily defended. Many amphibious light tank designs were created in the late 1940s to early 1960s. The Soviet design bureau of the Stalingrad/Volgograd tractor plant was behind several of them. The most famous is without a doubt Object 740, which became the PT-76, the most produced light tank of the Cold War. In the early 1960s, Volgograd would design a prototype infantry fighting vehicle for the program which would lead to the BMP-1. A light tank prototype would also soon follow using the chassis and suspension of this infantry fighting vehicle. The infantry fighting vehicle prototype was designated Object 911, and, as such, the light tank would be Object 911B. Both included some innovative or original features, but none would be adopted by the Soviet military.

A photo of Object 911B during its trials, with the suspension set for higher ground clearance. Source: Solyankin, Pavlov, Pavlov, Zheltov. Otechestvennye boevye mashiny vol. 3

Volgograd’s Object 911 and 906

The idea of a combat vehicle that would combine amphibious capacities, a dismounted infantry complement, and an armament that could provide fire-support to these infantry dismounts and accompanying tanks was developed in the late 1950s Soviet Army. A formal call for prototypes fulfilling this role to be designed was issued by the GBTU (The General Armored Directorate, the service in charge of armored vehicles procurement) on October 22nd 1960. The requirements were sent to a large number of design bureaus, and, at that time, called for an 11-12 tonnes vehicle that would feature a crew of 2 and transport 8 to 10 infantry dismounts.

One of the manufacturers which began work on a design was the Volgograd tractor plant (VgTZ). Volgograd had extensive experience in amphibious vehicles design from the PT-76, which it had been producing since the early 1950s, and of which a number of derivative designs had already been designed.

Soviet naval infantry PT-76B moving through water in front of a Whiskey-class submarine. The PT-76 was without a doubt one of Volgograd’s greatest successes. Source: twitter

Volgograd’s proposals, by 1963, took the shape of two distincts prototypes, the Object 911 and the Object 914. The Object 914 took the clear basis of the PT-76 chassis. The Object 911, however, was more distinct. Though there was still PT-76 inspiration and a number of common parts, such as the hydrojets and road wheels, the vehicle differed massively in other aspects. Likely the most noticeable were the four large, retractable aviation wheels which could give the Object 911 a wheeled drive, intended for use on roads during transfers to increase maximum speed and reduce fuel consumption. Object 911 also used an adjustable suspension which could be used to change the ground clearance of the vehicle.

The Object 906, a vastly improved amphibious light tank design Volgograd was working on from 1960 to 1963. The general layout of its autoloader would be picked up by Object 911B. Source: pinterest

In the same timeframe as it worked on infantry fighting vehicle prototypes, Volgograd had also designed and produced three prototypes of the Object 906. This was a vastly modernized and improved design based on the PT-76. It included a new, more powerful diesel engine, as well as an autoloaded 85 mm gun which significantly improved firepower in comparison to the PT-76’s 76 mm gun, particularly against armored targets and at range.

The Object 911B

By 1963, the Object 906 was at the testing stage with three prototypes, and would eventually be rejected within the year. At the same time, work had concretized on the Object 911, and manufacturing of the prototype took place within this year.

A ¾ view of the Object 911 prototype on its tracks. Source: Solyankin, Pavlov, Pavlov, Zheltov. Otechestvennye boevye mashiny vol. 3

If the Object 911 was to be adopted, it had been made clear by the GBTU’s requirements that the vehicle’s chassis was to be used for a whole family of various derivatives. This could, for example, include a light amphibious tank, something Volgograd had extensive experience with. The other Volgograd prototype from the program, the Object 914, used a more conventional drivetrain which could perhaps be easier to modify into derivatives. But, being very similar to the PT-76, there would be little reason to design a light tank version of the Object 914, seeing as the Object 914 could already be described as an infantry fighting version of a light tank. In comparison, the Object 911 could provide a more interesting base, particularly as the vehicle had an overall low profile enhanced by an adjustable height suspension.

Volgograd had already worked on a very low-profile amphibious light tank in the form of a derivative of the Object 906. This was the Object 906B, which was armed with a 125 mm tube missile launcher and featured two crewmembers in the turret. While work on the Object 906 and the Object 906B was discontinued during 1963, re-using components from them, notably the autoloader from the Object 906 and the general layout of the Object 906B, could prove valuable.

A profile schematic view of the Object 906B. The vehicle was never built, but the Object 911B would take direct inspiration from its layout and profile. Source: Solyankin, Pavlov, Pavlov, Zheltov. Otechestvennye boevye mashiny vol. 3

As such, in 1963, the designing of a light tank version of the Object 911 would be carried out. The resulting vehicle would be named Object 911B. While using the chassis of the Object 911, it introduced a large variety of changes, not all directly linked to its function as a light tank. While keeping the same 73 mm Grom armament, it took inspiration from the Object 906B’s layout and the Object 906’s autoloader. A prototype of the Object 911B would be manufactured and tested in 1964.

The Object 911B’s Hull and Armor Layout

Schematics showing a general view of the Object 911B, as well as comparing its profile to the PT-76. Source: Imgur

The Object 911B was a particularly low vehicle. Its height would vary between 1,265 mm and 1,615 mm depending on the set height of the suspension. This was particularly small. At its lowest, the height of a child, and even at its highest, the height of an average to small man. This would result in increased survivability, as the vehicle would be a hard target to hit at range, though at the same time creating proper crew conditions with such a low profile could be difficult. Length was 7.1 m, and width was 2.8 m. The weight of the Object 911B when loaded with crew, fuel, and ammunition would have been 12.5 tonnes. Thanks to its fairly small dimensions and reduced weight, the Object 911B was air-transportable by the Antonov AN-12.

The Object 911B used a peculiar hull and armor layout in order to increase the survivability of the vehicle and crew. This is typically not an easy task on a light amphibious tank, which has to use light armor protection and cannot afford to have large, thick metal plates in order not to compromise buoyancy and to retain a light weight.

A side cutaway view showing the very peculiar armor layout and arrangement of the Object 911B. Source: Imgur
A front cutaway view showing the side armor protection of the crew compartment. Source: Imgur

To the front of the vehicle was what is typically described as a “cargo compartment”. This section was quite long, and did not contain any vital parts necessary for the vehicle to function. This storage space was reportedly capable of containing two men lying down, which could allow Object 911B to evacuate wounded servicemen. One can also imagine this feature may have been used to evacuate the crew of another knocked out or broken down Object 911B, seeing as the vehicle had a crew of two. The cargo compartment’s possible use to transport personnel in emergencies is further supported by the presence of two access hatches on the roof sides. When empty, the large size but low weight brought by this compartment would likely also help with the Object 911B’s buoyancy. The armor protection of this part of the vehicle can only be described as minimal. The front plate was only 10 mm thick, angled at 45° towards the back, while the roof was 6 mm thick and the floor a mere 4 mm. The sides likely had the same 10 mm thickness as the front, but without the considerable angling of the front plates

Behind this cargo compartment would be the crew compartment. The two were separated by an armored bulkhead. Being 35 mm thick, though mostly vertical with no or minimal angling, this bulkhead was actually intended to be the main frontal armor of the vehicle’s hull. An advantage of its position inside the vehicle was that it covered significantly less space, and as such, was much lighter than a similar armor layout applied to the front of the vehicle. When added to the 10 mm of the front armor and the considerable empty space of air separating it from the 35 mm bulkhead, this armor layout was actually quite considerable for a light infantry tank, and would typically protect the crew from heavy machine-gun fire, and often even autocannons. The front armor of the turret, which would not benefit from the 10 mm of armor of the cargo compartment and spacing separating it from the bulkhead received 40 mm of armor angled backward at 48° frontally, and 40 mm angled backward at 30° on the sides, with the same thickness to the rear. The hull sides were also quite thickly armored, with 45 mm on the upper sides and 20mm on the lower sides. The roof and floor of the crew compartment were also thicker, at 10 mm each. The crew compartment, within the vehicle’s turret, contained the two crewmembers, a driver to the right and a commander/gunner to the left.

The crew compartment was then separated from the rear compartment by another 35 mm bulkhead. The vehicle’s powerplant and transmission were to the rear. This part of the vehicle had the same light armor layout found on the front cargo compartment. The floor was 4 mm thick, while the roof and rear were 6 mm, and the sides likely 10 mm. The lower rear plate was angled at 48°, while angling on other plates was inexistant or minimal. This light armor protection was a necessity to keep weight down, but penetrating hits in this section of the vehicle would obviously be much more damaging than in the cargo compartment, easily leading to the vehicle’s engine being damaged or destroyed.

Engine and Transmission

The Object 911B used the same UTD-20 diesel engine as had been used on the Object 911. This engine had previously been set as part of requirements sent to different manufacturers to produce an infantry fighting vehicle prototype and all competitors to the Object 911 also featured it. It produced 300 hp at 2,600 rpm, and reached its maximum torque output of 981 N.m at 1,500 to 1,600 rpm. Without any fuel or oil, the engine weighed 665 kg, and had a consumption of 175 to 178 grams of fuel per hp and hour. A total of 500 liters of fuel were stowed within the Object 911B.

An UTD-20 engine, which was widely used in Soviet infantry fighting vehicles and light tank prototypes from the 1960s onward. Source: https://geek-tips.imtqy.com/

An advantage of the UTD-20 was its limited size compared to its output, which was a very favorable feature for mounting it in light armored fighting vehicles such as the Object 911 or the Object 911B, allowing for the very low silhouette adopted by the vehicles. The engine was used to drive a rear transmission. The Object 911B’s transmission used a two-disc main friction clutch, composed of dry steel and asbestos, a two-flow non-differential gear and rotation mechanism, and two single-row planetary on-board gearboxes. The Object 911B used a two-shaft, 5-speeds gearbox. It was reversible, meaning the vehicle could drive with the same maximum speed and gear ratios backward. The vehicle was also capable of neutral steering.

In addition to this engine and transmission, the Object 911B also featured two hydrojets. These were found in the rear sides of the vehicle. They were taken straight from the PT-76. These hydrojets were powered via a driveshaft with a reducer, linked to the gearbox, and would allow for far quicker movement on water than vehicles using merely tracks or wheels for amphibious crossings. A trim vane could also be deployed to prevent waves from washing over the vehicle.

The Object 911B on water during its trials. This photo gives a good view of the trim vane deployed, but also of the vehicle’s radio antenna. Source: Source: Solyankin, Pavlov, Pavlov, Zheltov. Otechestvennye boevye mashiny vol. 3

Suspension and Drivetrain

The suspension of the Object 911B was directly based on the one found on the Object 911, but incorporated a number of changes. A standout feature of the Object 911 had been its four retractable aviation wheels, which allowed for wheeled drive. The advantages of such a design were higher maximum speed and reduced fuel consumption when driving on roads, which would prove useful out of combat. However, it led to increased complexity in production, maintenance, crew training, and cross-country mobility. As such, these retractable wheels were removed from the Object 911B’s design.

The Object 911 also included another innovative feature, an adjustable suspension. This was found to be less of a hassle, while at the same time having more uses, including in combat, and as such was retained on the Object 911B.

A front view of Object 911B, with its suspension likely at or close to its highest point. This photo also gives a good view of the headlights, mounted on the turret, as well as the cupola, which is not in fact crewed by the commander but the driver. Source: Solyankin, Pavlov, Pavlov, Zheltov. Otechestvennye boevye mashiny vol. 3
Front schematics of Object 911B at the highest and lowest suspension setting. Source: Solyankin, Pavlov, Pavlov, Zheltov. Otechestvennye boevye mashiny vol. 3

The suspension of the vehicles was not exactly identical. The Object 911B was longer and had a longer track run, and as such used an additional road wheel, bringing the number to six per side. These were stamped steel hollow road wheels, the same type as used on PT-76, or at least a very similar type. Their main advantage was that their hollow construction both saved weight and improved buoyancy. Each road wheel was mounted on a suspension arm of which the movement was assured by a pneumatic suspension. The suspension’s height could be adjusted and considerably lowered. The highest ground clearance the Object 911B could raise itself to was 450 mm, which was more than any other Volgograd amphibious tank design from the era, including the PT-76 and the Object 906. When fully lowered, the ground clearance would be reduced to 100 mm. These changes in ground clearance would result in the Object 911B’s height varying from 1,625 mm to 1,265 mm. The higher ground clearance would be useful when the vehicle was driving over rough or irregular terrain, preventing risks of the lower hull being stuck on an obstacle, which would damage it or result in the vehicle losing track tension and getting bogged down and stuck. The lower ground clearance, on the other hand, would have the obvious advantage of significantly reducing the already tiny silhouette of the Object 911B. The vehicle’s drive sprocket was mounted to the rear, with a front idler. As on the Object 911, three return rollers, made of aluminum, were also present.

The tracks used on the Object 911B reportedly varied from the RMSH type used on the Object 911.

Crew compartment and turret

The crew compartment of the Object 911B was mostly in the vehicle’s turret. Both crewmembers were seated in this turret, with the driver to the right of the gun and the commander/gunner to the left. The turret had a frustoconical shape. It was of a fairly wide but very low design, differing significantly from the standardized turret featured in the Object 911.The turret rotation speed seems to have been of 30 degrees/second.

The low height of the vehicle likely resulted in the turret being quite cramped. Taking the minimum height and ground clearance of the vehicle into account, the vehicle must have been at most 1.15 m from hull floor to turret roof, not even accounting from the spacing which would exist between the floor and the seat’s bottom. This particularly low profile, though it could be commended in a way, necessitated for men of below-average height to operate the vehicle reasonably.

Comprehensive work was invested in making the crew compartment safe against nuclear threats. It was given good insulation, using special materials in addition to the steel. The Object 911B also included a radiation and chemical reconnaissance device, which would be able to measure level of radiation in an area and would be able to automatically shut the hatches if the nuclear elements that precede the shockwave of a nuclear detonation were detected.

Other equipment fitted inside Object 911B included four thermal detectors present in the cargo compartment and a further two in the engine compartment. If excessive heat was detected, these would trigger a fire extinguisher that spat out an extinguishing chemical mixture. A 2 l cylindrical container for this mixture was present in both the cargo and engine compartment.

The crew compartment featured the R-123 high/very high-frequency radio transceiver, by this point a new introduction in Soviet vehicles, which could assure communications at ranges up to 20 km on two bands. The radio antenna was on the left side of the turret. It was coupled with an internal R-124 intercom system for communications between the gunner/commander and driver. It also featured a TNA-2 navigation device and a “Brusok” encryption device for the vehicle’s outside communications. Power for this electrical equipment was provided by a 5 kW VG-7500 generator that powered two 12ST-70 batteries. 10 F1 fragmentation hand grenades, as well as a signal pistol with ten cartridges, were also stored within the crew compartment.

The R-123 radio station. Source: pinterest
An R-124 intercom system dismounted from a vehicle. Source: http://pribor.zp.ua/

Crew Positions

The gunner on the Object 911B was located to the left of the gun. Right on top of his head was a fairly large rectangular hatch he could enter or exit from.

A view of the Object 911B’s turret from the right, with the two crewmembers present inside the turret. Source: Solyankin, Pavlov, Pavlov, Zheltov. Otechestvennye boevye mashiny vol. 3

Vision devices at the gunner’s disposal included a large periscope to the front and three TNPO-170 prismatic periscopes to the side. The gun was automatically loaded, but could also be loaded manually, a task he would handle if the autoloader was no longer working. Sources refer to the vehicle’s main sight as the PKB-62, with a field of view of 15° at day and 6° at night. This appears identical to the 1PN22 combined day-night sight used on the Object 911, and this may simply be two different ways of referring to the same sight. If the 1PN22 was indeed used, this sight had two channels, one for day and one for night, which would be toggled by rotating an internal mirror. The gunner would look through the same eyepiece in any case. Using the day channel, the sight had a magnification of 6x and a field of view of 15°. The night channel had a magnification of 6.7x and a field of view of 6°. It had a three-stage light intensifier system that would amplify light by 50,000 to 75,000 times. It also featured vastly simplified lead and range corrections scales in order to ease night firing.

A close-up of the seat and commands of the driver’s post. This rotating position was one of the more peculiar features of the Object 911B. Source: Solyankin, Pavlov, Pavlov, Zheltov. Otechestvennye boevye mashiny vol. 3

The driver had by far the most peculiar position on Object 911B. His seat, as well as the controls, were placed in a sort of ‘bathtub’. This ‘bathtub’ itself rotated within the turret. It would systematically remain aligned with the front of the tank. This was meant to allow the driver to always look straight in the position he was driving towards, but on vehicles with similar devices, such as the MBT-70, this is known to have made drivers disorientated and sick, and this may have been an issue here as well. Advantages included much better visibility for the driver, as well as, in most vehicles, resulting in less chances of crew casualties from anti-tank mines (mines would usually explode under the first road wheel, which the driver would be further away from thanks to his placement in the turret – the presence of the armored bulkhead would also grant protection against fragments). In the matter of crew survivability, the driver being in the turret could also usually escape the vehicle faster, and there would be no risk of the opening of his hatch being compromised by the gun barrel at an unfortunate time.

When reversing, this crew position was even more peculiar. A mechanism was built within the transmission gear mechanism to allow the vehicle to be driven in reverse. When wanting to reverse, the driver would be able to disconnect the clutch and pedals of his position, which t would then rotate 180°, and the controls would then be reconnected to the gearbox. In this fashion, when reversing, the driver would face towards the rear and could look straight towards where he was driving, making this essentially quite similar to driving towards the front.

A view of the Object 911B’s turret from the left, with the driver’s position shifted slightly towards the right. Source: Solyankin, Pavlov, Pavlov, Zheltov. Otechestvennye boevye mashiny vol. 3
A front view of the Object 911B’s turret, with the reverse driving triggered and the driver facing to the rear. This angle also shows a good view of the vehicle’s mantlet and main gunner periscope. Source: Solyankin, Pavlov, Pavlov, Zheltov. Otechestvennye boevye mashiny vol. 3

When it came to vision, the driver had three TNPO-170 prismatic periscopes as well as a TVN-2B night vision device to enable safer and easier night driving. The position’s periscopes were placed on a cupola which was slaved to the movement of the driver’s position inside the vehicle, so as with the driver’s position, they would always face in the direction the tank was driving, regardless of the turret’s position.

Armament

General schematics of the 2A28 Grom. Source: Tankograd

The main armament of the turret was a 73 mm 2A28 Grom low-pressure smoothbore gun. This was a fairly short gun, with a 2,117 mm tube and 2,180 mm total length. The design was overall made to be very simple and light. For example, it lacked any bore evacuator, and the gun fumes were instead to be evacuated from the turret, which featured a ventilator for this purpose. The gun overall weighed only 115 kg and had an average barrel life of 1,250 rounds. The recoil mechanism of the Grom was contained in an armored sleeve, wrapped around the base of the barrel. Gun elevation angles in the Object 911B extended from +30° to -3°, which was limited even by Soviet standards. The gun could elevate electrically and manually.

A number of PG-15V rounds, here captured by Azerbaijan from Armenia during the 2020 Nagorno-Karabakh War. The round was produced in massive quantities, and despite more modern ammunition to fulfill both anti-armor and anti-personnel roles, having been available since the 1970s, it is still widely used. Source: reddit

There was only a single shell type available to the 2A28 Grom in the 1960s, the PG-15V. It used the PG-9 HEAT anti-tank grenade already used by the SPG-9 73 mm recoilless gun, but swapped the original propellant charge with a more powerful PG-15P, which was meant to ensure a longer effective range. The projectile was fin-stabilized and featured a rocket engine towards the rear, with propellant present towards the middle of the grenade. This allowed it to reach a higher speed than would typically be expected from a gun as short as the Grom, with a maximum velocity of 655 m/s.

The explosive charge of the PG-9 grenade was a 322 g explosive mixture which would be equivalent to 515 g of TNT. An advantage of the PG-9 was that it featured a high standoff distance (i.e distance between the shaped charge and tip of the fuze) of 258 mm. In practice, this meant that, upon hitting a target, the jet of molten metal would have a significant length to take shape into a thin, dense jet. The results were a great armor penetration for the time and small size of the gun. The projectile’s armor penetration was officially rated at 300 mm at all ranges. In practice, this was slightly higher, as the official figure was based on the quantity of armor which would be pierced with the shell then having significant post-penetration effects inside. The maximum penetration achieved could vary between 302 and 346 mm, with an average value of 326 mm. In practice, this meant the Grom could quite reliably penetrate any tank operated by NATO in the 1960s.

The shell was not without issues, however. The downside of HEAT projectiles and a very short barrel were an overall low accuracy and high dispersion. The Grom’s PG-15V projectiles were notably very vulnerable to wind. The nominal maximum range of the Grom was of 800 m, but even at this range, only a 34% hit rate was achieved against a T-55 during trials. Even if this tank was quite smaller than most NATO tanks, in practice it can still be said a vehicle wielding a Grom would have to get to close ranges to use this gun effectively against armored targets. Additionally, during the 1960s, the PG-15V was the only available shell for the 2A28 Grom. HEAT shells are not purely anti-tank projectiles, and by nature also have some capacities against other targets. They can notably be effective when used against field fortifications and bunkers. However, due to their design focusing on producing a jet of molten metal in one direction, they offer very limited capacities when attempting to fire at infantry in the open. For the vast majority of vehicles, this would fairly easily be dealt with by simply shifting to a high-explosive fragmentation shell, but no projectile of the type would be available for the Grom until 1973.

The 2A28 Grom was fed by an autoloading mechanism. This was not the same as the crescent-shape conveyor present on the Object 911’s standardized turret design, which would contain all 40 73 mm Grom projectiles carried inside the vehicle.

While the Object 911B also had a 40 rounds ammunition stowage, its autoloader only held 27 at a time. The commander/gunner could feed more rounds into it once some were expended, or in the unlikely scenario all rounds within the autoloader were expended and no new shells had been placed into it, he could manually reload the gun as well. The autoloader mechanism was a horizontal electrically-driven conveyor belt. It would ensure a rate of fire of 9 rounds per minute. The autoloader could be installed or removed from the vehicle for repair or replacement via a special hatch.

Photos of the 7.62 mm PKT machine gun. Source: weaponsystems.net

The 2A28 Grom was supplemented by a 7.62 mm PKT coaxial machine gun. Mounted to the right of the gun, it would effectively be the only reliable means of dealing with infantry in the open. It fed to the right and ejected to the left. The PKT was fed from 250 rounds ammunition boxes and would fire at a cyclic rate of fire of 700 to 800 rounds per minute, at a muzzle velocity of 855 m/s. It would be able to expend two ammunition boxes in quick succession before the barrel would need to be replaced, or at least the firing interrupted for a bit to prevent overheating. A total of 2,000 7.62 mm rounds were stowed within the Object 911B.

Crucially, the Object 911B did not feature the 9M14 Malyutka missile or control system featured on the Object 911. This technically meant that the light tank was less armed than the infantry fighting vehicle, a considerable disadvantage. The Grom had a limited effective range, and while the Malyutka was not the most accurate or reliable missile, it was still a much better weapon to take out armored targets at longer ranges. Without the Malyutka, the Object 911B could only engage enemy armor within the reduced effective range of the Grom.

Trials and Performances

The Object 911B prototype was completed and trialed in 1964.

The vehicle was able to reach a maximum speed of 72.5 km/h on road. This was a considerable improvement from the Object 911 which would only manage 57 km/h on tracks. The main reason likely was the removal of the extendable wheels and changes to the suspension. On water, the vehicle could reach a similar maximum speed of 10 km/h, which was generally the norm for vehicles equipped with the PT-76’s hydrojet design. The maximum range on road was 500 km, similar to the Object 906 and exceeding the PT-76. Ground pressure was 0.42 kg/cm².

Object 911B at its lowest suspension height next to a PT-76B during its trials. The low profile of the vehicle at the lowest suspension setting was exceptional. Source: Solyankin, Pavlov, Pavlov, Zheltov. Otechestvennye boevye mashiny vol. 3

The vehicle’s armor protection was tested against two different threats. The first was against 76.2 mm projectiles fired at ranges of 2,000 m with a muzzle velocity of 665 m/s. These were likely kinetic projectiles fired from the PT-76’s D-56T (this velocity matches with the BR-350B and BR-354 APBC-HE shells, the latter of which was more common by this point in time). The frontal crew compartment armored bulkhead and turret armor were both found to resist penetration at this range. These were satisfactory performances. While the D-56T was not a very powerful gun and the projectiles were fired at a long range, a light amphibious tank is not a vehicle that is expected to resist armor-piercing weapons at pretty much any range, and indeed many vehicles fulfilling a similar role, such as the PT-76 or M551 Sheridan, would still be fairly easily penetrated even at this range.

More representative of the armament a light tank with good armor protection for the type may be expected to resist, the Object 911’s crew compartment was also tested against the 14.5 mm KPV. The weapon failed to penetrate both the front bulkhead and the hull sides. This was once again quite a considerable feat. The 14.5 mm KPV was one of the most powerful mass-produced heavy machine guns around, and if the Object 911B’s crew compartment was impervious to it, it would certainly resist NATO’s .50 cal Browning M2HB. In certain conditions, such as with some range and with imperfect firing angles, which are to be expected in combat, the crew compartment of the Object 911B may have stood decent chances to resist fire from many NATO autocannons of calibers around 20 mm, which would be an impressive performance for a light amphibious tank.

Conclusion – Interesting Performances with no Niche to Fulfill

Ultimately, the Soviet Army did not adopt the Object 911B, and work on the vehicle was discontinued after the trials ended in 1964.

A number of reasons can be found for the rejection of the vehicle. The most obvious was that the original Object 911 was not picked to become the BMP-1, being ruled out of the candidates due to complications with its drivetrain fairly early on. The other Volgograd prototype, the Object 914, was a more serious candidate but was eventually rejected in favor of the Object 765, which would become the famed BMP-1 that remains widely in use across the world today. There would have been little motivation in adopting a light tank derived from an infantry fighting vehicle which was rejected. Even though the Object 911B had significant parts commonality with vehicles already in service, such as the engine, road wheels, or armament, it would still lead to increased logistical complexity.

However, outside of these external considerations, the Object 911B had faults of its own. Some aspects of the vehicle were genuinely quite impressive, with the exceptionally low profile at the foremost. The armor protection given to the crew was also significant for a vehicle of the type. The crew of an Object 911B would have much more chances to survive enemy fire than the one of another amphibious light tank, such as the previous Soviet PT-76, the American M551 Sheridan, or the British FV 101 Scorpion fitted with a floatation device. Being able to resist heavy machine-gun fire or even light autocannons is significantly better than most vehicles of the type and would protect the Object 911B’s crew from some widely-encountered threats. This level of protection only extended to the crew, with the cargo and crucially engine compartment only being protected against rifle-caliber projectiles, but it was still significant.

The Object 765 prototype, which would be adopted and become the BMP-1 in 1964. With this vehicle already scheduled for production, there was little need for the Object 911B. While one may point to several advantages of the Object 911B in terms of survivability, this was not as strong as an argument in comparison to the eight dismounts and 9M14 Malyutka missile sported by the BMP. Source: Solyankin, Pavlov, Pavlov, Zheltov. Otechestvennye boevye mashiny vol. 3

However, the vehicle’s firepower was far too low to justify its existence. The Object 911B was only armed with the same 73 mm 2A28 Grom as the BMP-1 and a coaxial machine gun, and its lower profile and better armor protection could hardly create the need for it. In comparison, the BMP-1 would not only transport eight dismounts, but also feature a 9M14 Malyutka missile, which means it would be far better equipped to deal with enemy armor at range. Indeed, for all of the Object 911B’s advantages in survivability granted by its low profile and armor protection, these would be in large part negated by the need to be at small ranges for the Grom to have a good chance to hit enemy targets. At those ranges, enemy guns would have far lower difficulty to target the smaller profile of the Object 911B, and the vehicle would likely fall prey to most tanks before it could be at short enough range to target them unless it could be undetected until the moment it fired. While this would be easier for the Object 911B than pretty much any other tank, it is still not something to be relied upon, particularly if the vehicle was to be used offensively. The issues of disorientation that could arise from the driver’s placement in the turret were also not resolved.

In short, while very interesting in several aspects, the Object 911B did not fulfill any niche where a vehicle of its kind was necessary, and as such it is not surprising it was not adopted by the Soviet Army. Unlike the Object 911, the Object 911B does not appear to be preserved at the Kubinka Tank Museum, or at least not in its visitable parts, as no modern photos of the vehicle have emerged. It may have been scrapped, or still be preserved outside of public view.

Object 911B, illustrated by Pavel “Carpaticus” Alexe

Object 911B specifications

Dimensions (L-W-H) 7.100 x 2.800 x 1.625 to 1.265 m
Ground clearance 100 to 450 mm (adjustable)
Combat weight 12.5 tonnes
Engine UTD-20 6-cylinders 300 hp diesel engine
Suspension Adjustable pneumatic springs
Transmission mount rear
Forward gears 5 (reversible)
Road wheels 6
Maximum speed (road) 72.5 km/h
Maximum speed (water) 10 km/h
Range 500 km (road)
Crew 2 (driver, commander/gunner)
Gunner’s vision devices Main periscope
3 x TNPO-170 prismatic periscopes
PKB-62 (1PN22 ?) sight
Driver’s vision devices 3x TNPO-170 prismatic periscopes in a rotating cupola facing towards the direction the vehicle is driving in
TVN-2B night vision device
Main gun 73 mm 2A28 ‘Grom’ with 40 rounds (27 stowed in autoloader)
Autoloader Electrically-driven horizontal conveyor belt
Secondary armament Coaxial 7.62 mm PKT with 2,000 rounds
Hull armor Cargo compartment:
10 mm/45° (front)
4 mm (floor)
6 mm (roof)
Likely 10 mm (sides)Crew compartment:
35 mm (front bulkhead)
45 mm (upper sides)
20 mm (lower sides)
35 mm (rear bulkhead)
10 mm (roof and floor)
Turret:
40 mm /40° (front)
40 mm /30° (sides)
Likely 40 mm (rear)
10 mm (roof)
Engine compartment:
4 mm (floor)
6 mm (roof and rear)
Likely 10 mm (sides)
Effective protection of crew compartment 76.2 mm projectile fired at 665 m/s and a range of 2,000m (front bulkhead and turret)
14.5 mm KPV fire from all angles
Numbers produced 1

Sources

Solyankin, Pavlov, Pavlov, Zheltov. Otechestvennye boevye mashiny vol. 3
73-мм ГЛАДКОСТВОЛЬНОЕ ОРУДИЕ 2A28Техническое описание и инструкция по эксплуатации (73-mm SMOOTHBORE WEAPON 2A28 Technical description and operating instructions)
БОЕВАЯ МАШИНА ПЕХОТЫ БМП-1 ТЕхничЕскоЕ ОПИсаниЕ И ИНСТРУКЦИЯ ПО ЭКСПЛУАТАЦИИ (COMBAT VEHICLE INFANTRY BMP-1 Technical Description AND THE OPERATING INSTRUCTIONS)
BMP-1 field disassembly, Tankograd
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