1:72 “Object 511” a.k.a. “ZSU-37-6 / Лена” prototype, USSR Army, during state acceptance trials; Donguzskiy weapon test range, Orenburg Oblast, summer 1979 (What if/kit-bashing)

1:72 “Object 511” a.k.a. “ZSU-37-6 / Лена” prototype, USSR Army, during state acceptance trials; Donguzskiy weapon test range, Orenburg Oblast, summer 1979 (What if/kit-bashing)

+++ DISCLAIMER +++
Nothing you see here is real, even though the conversion or the presented background story might be based on historical facts. BEWARE!

Some background:
The ZSU-37-6 (“ZSU” stands for Zenitnaya Samokhodnaya Ustanovka / Зенитная Самоходная Установка = "anti-aircraft self-propelled mount"), also known as Object 511 during its development phase and later also as “ZSU-37-6 / Лена”, was a prototype for a lightly armored Soviet self-propelled, radar guided anti-aircraft weapon system that was to replace the cannon-armed ZSU-23-4 “Shilka” SPAAG.
The development of the "Shilka" began in 1957 and the vehicle was brought into service in 1965. The ZSU-23-4 was intended for AA defense of military facilities, troops, and mechanized columns on the march. The ZSU-23-4 combined a proven radar system, the non-amphibious chassis based on the GM-575 tracked vehicle, and four 23 mm autocannons. This delivered a highly effective combination of mobility with heavy firepower and considerable accuracy, outclassing all NATO anti-aircraft guns at the time. The system was widely fielded throughout the Warsaw Pact and among other pro-Soviet states. Around 2,500 ZSU-23-4s, of the total 6,500 produced, were exported to 23 countries.

The development of a potential successor started in 1970. At the request of the Soviet Ministry of Defense, the KBP Instrument Design Bureau in Tula started work on a new mobile anti-aircraft system as a replacement for the 23mm ZSU-23-4. The project was undertaken to improve on the observed shortcomings of the ZSU-23-4 (short range and no early warning) and to counter new ground attack aircraft in development, such as the A-10 Thunderbolt II, which was designed to be highly resistant to 23 mm cannons.

KBP studies demonstrated that a cannon of at least 30 mm caliber was necessary to counter these threats, and that a bigger caliber weapon would offer some more benefits. Firstly, to destroy a given target, such a weapon would only require from a third to a half of the number of shells that the ZSU-23-4’s 23 mm cannon would need. Secondly, comparison tests revealed that firing with an identical mass of 30 mm projectiles instead of 23 mm ammunition at a MiG-17 (or similarly at NATO’s Hawker Hunter or Fiat G.91…) flying at 300 m/s would result in a 1.5 times greater kill probability. An increase in the maximum engagement altitude from 2,000 to 4,000 m and higher effectiveness when engaging lightly armored ground targets were also cited as potential benefits.

The initial requirements set for the new mobile weapon system were to achieve twice the performance in terms of the ZSU-23-4’s range, altitude and combat effectiveness. Additionally, the system should have a reaction time, from target acquisition to firing, no greater than 10 seconds, so that enemy helicopters that “popped up” from behind covers and launched fire-and-forget weapons at tanks or similar targets could be engaged effectively.
From these specifications KBP developed two schools of thought that proposed different concepts and respective vehicle prototypes: One design team followed the idea of an anti-aircraft complex with mixed cannon and missile armament, which made it effective against both low and high-flying targets but sacrificed short-range firepower. The alternative proposed by another team was a weapon carrier armed only with a heavy gatling-type gun, tailored to counter targets flying at low altitudes, esp. helicopters, filling a similar niche as the ZSU-23-4 and leaving medium to high altitude targets to specialized anti-aircraft missiles. The latter became soon known as “Object 511”.

Object 511 was based on the tracked and only lightly armored GM-577 chassis, produced by Minsk Tractor Works (MTZ). It featured six road wheels on each side, a drive sprocket at the rear and three return rollers. The chassis was primarily chosen because it was already in use for other anti-aircraft systems like the 2K11 “Krug” complex and could be taken more or less “off the rack”. A new feature was a hydropneumatic suspension, which was chosen in order to stabilize the chassis as firing platform and also to cope with the considerably higher all-up weight of the vehicle (27 tons vs. the ZSU-23-4’s 19 tons). Other standard equipment of Object 511 included heating, ventilation, navigational equipment, night vision aids, a 1V116 intercom and an external communications system with an R-173 receiver.

The hull was – as the entire vehicle – protected from small arms fire (7,62mm) and shell splinters, but not heavily armored. An NBC protection system was integrated into the chassis, as well as an automatic fire suppression system and an automatic gear change. The main engine bay, initially with a 2V-06-2 water-cooled multi-fuel diesel engine with 450 hp (331 kW) was in the rear. It was later replaced by a more powerful variant of the same engine with 510 hp (380 kW).
The driver sat in the front on the left side, with a small gas turbine APU to his right to operate the radar and hydraulic systems independently from the main engine.
Between these hull segments, the chassis carried a horseshoe-shaped turret with full 360° rotation. It was relatively large and covered more than the half of the hull’s roof, because it held the SPAAGs main armament and ammunition supply, the search and tracking radar equipment as well as a crew of two: the commander with a cupola on the right side and the gunner/radar operator on the left side, with the cannon installation and its feeding system between them. In fact, it was so large that Object 511’s engine bay was only accessible when the turret was rotated 90° to the side – unacceptable for an in-service vehicle (which would probably have been based on a bigger chassis), but accepted for the prototype which was rather focused on the turret and its complex weapon and radar systems.

Object 511’s centerpiece was the newly-developed Gryazev-Shipunov GSh-6-37 cannon, a heavy and experimental six-barreled 37mm gatling gun. This air-cooled weapon with electrical ignition was an upscaled version of the naval AO-18 30mm gun, which was part of an automated air defense system for ships, the AK-630 CIWS complex. Unlike most modern American rotary cannons, the GSh-6-37 was gas-operated rather than hydraulically driven, allowing it to "spin up" to maximum rate of fire more quickly. This resulted in more rounds and therefore weight of fire to be placed on target in a short burst, reduced reaction time and allowed hits even in a very small enemy engagement window.

The GSh-6-37 itself weighed around 524 kg (1.154 lb), the whole system, including the feed system and a full magazine, weighed 7,493 pounds (3,401 kg). The weapon had a total length of 5.01 m (16’ 7“), its barrels were 2.81 m (9’ 2½”) long. In Object 511’s turret it had an elevation between +80° and -11°, moving at 60°/sec, and a full turret rotation only took 3 seconds. Rate of fire was 4,500 rounds per minute, even though up to 5.500 RPM were theoretically possible and could be cleared with an emergency setting. However, the weapon would typically only fire short bursts of roundabout 50 rounds each, or longer bursts of 1-2 (maximum) seconds to save ammunition and to avoid overheating and damage – initially only to the barrels, but later also to avoid collateral damage from weapon operation itself (see below). Against ground targets and for prolonged, safe fire, the rate of fire could alternatively be limited to 150 RPM.
The GSh-6-37 fired 1.09 kg shells (each 338mm long) at 1,070 m/s (3.500 ft/s), developing a muzzle energy of 624,000 joules. This resulted in an effective range of 6,000 m (19.650 ft) against aerial and 7,000 m (23.0000 ft) against ground targets. Maximum firing range was past 7,160 m (23,490 ft), with the projectiles self-destructing beyond that distance. In a 1 sec. burst, the weapon delivered an impressive weight of fire of almost 100 kg.
The GSh-6-37 was belt-fed, with a closed-circuit magazine to avoid spilling casings all around and hurting friendly troops in the SPAAG’s vicinity. Typical types of ammunition were OFZT (proximity-fused incendiary fragmentation) and BZT (armor-piercing tracer, able to penetrate more than 60 mm of 30° sloped steel armor at 1.000 m/3.275’ distance). Since there was only a single ammunition supply that could not be switched, these rounds were normally loaded in 3:1 ratio—three OFZT, then one BZT, every 10th BZT round marked with a tracer. Especially the fragmentation rounds dealt extensive collateral damage, as the sheer numbers of fragments from detonating shells was sufficient to damage aircraft flying within a 200-meter radius from the impact center. This, coupled with the high density of fire, created a very effective obstacle for aerial targets and ensured a high hit probability even upon a casual and hurried attack.

The gun was placed in the turret front’s center, held by a massive mount with hydraulic dampers. The internal ammunition supply in the back of the turret comprised a total of 1.600 rounds, but an additional 800 rounds could be added in an external reserve feed bin, attached to the back of the turret and connected to the internal belt magazine loop through a pair of ports in the turret’s rear, normally used to reload the GSh-6-37.

A rotating, electronically scanned E-band (10 kW power) target acquisition radar array was mounted on the rear top of the turret that, when combined with the turret front mounted J-band (150 kW power) mono-pulse tracking radar, its dish antenna hidden under a fiberglass fairing to the right of the main weapon, formed the 1RL144 (NATO: Hot Shot) pulse-Doppler 3D radar system. Alongside, the 1A26 digital computer, a laser rangefinder co-axial to the GSh-6-37, and the 1G30 angle measurement system formed the 1A27 targeting complex.
Object 511’s target acquisition offered a 360-degree field of view, a detection range of around 18 km and could detect targets flying as low as 15 m. The array could be folded down and stowed when in transit, lying flat on the turret’s roof. The tracking radar had a range of 16 km, and a C/D-band IFF system was also fitted. The radar system was highly protected against various types of interference and was able to work properly even if there were mountains on the horizon, regardless of the background. The system made it possible to fire the GSh-6-37 on the move, against targets with a maximum target speed of up to 500 m/s, and it had an impressive reaction time of only 6-8 seconds.
Thanks to its computerized fire control system, the 1A27 was highly automated and reduced the SPAAG’s crew to only three men, making a dedicated radar operator (as on the ZSU-23-4) superfluous and saving internal space in the large but still rather cramped turret.

Development of Object 511 and its systems were kicked-off in 1972 but immediately slowed down with the introduction of the 9K33 “Osa” missile system, which seemed to fill the same requirement but with greater missile performance. However, after some considerable debate it was felt that a purely missile-based system would not be as effective at dealing with very low flying attack helicopters attacking at short range with no warning, as had been proven so successful in the 1973 Arab-Israeli War. Since the reaction time of a gun system was around 8–10 seconds, compared to approximately 30 seconds for a missile-based system, development of Object 511 was restarted in 1973.

A fully functional prototype, now officially dubbed “ZSU-37-6“ to reflect its role and armament and christened “Лена” (Lena, after the Russian river in Siberia), was completed in 1975 at the Ulyanovsk Mechanical Factory, but it took until 1976 that the capricious weapon and the 1A27 radar system had been successfully integrated and made work. System testing and trials were conducted between September 1977 and December 1978 on the Donguzskiy range, where the vehicle was detected by American spy satellites and erroneously identified as a self-propelled artillery system with a fully rotating turret (similar to the American M109), as a potential successor for the SAU-122/2S1 Gvozdika or SAU-152/2S3 Akatsiya SPGs that had been introduced ten years earlier, with a lighter weapon of 100-120mm caliber and an autoloader in the large turret.

The tests at Donguzskiy yielded mixed results. While the 1A27 surveillance and acquisition radar complex turned out to be quite effective, the GSh-6-37 remained a constant source of problems. The gun was highly unreliable and afforded a high level of maintenance. Furthermore, it had a massive recoil of 6.250 kp/61 kN when fired (the American 30 mm GAU-8 Avenger “only” had a recoil of 4.082 kp/40 kN). As a result, targets acquired by the 1A27 system were frequently lost after a single burst of fire, so that they had to be tracked anew before the next shot could be placed.
To make matters even words, the GSh-6-37 was noted for its high and often uncomfortable vibration and extreme noise, internally and externally. Pressure shock waves from the gun muzzles made the presence of unprotected personnel in the weapon’s proximity hazardous. The GSh-6-37’s massive vibrations shook the whole vehicle and led to numerous radio and radar system failures, tearing or jamming of maintenance doors and access hatches and the cracking of optical sensors. The effects were so severe that the gun’s impact led after six months to fatigue cracks in the gun mount, the welded turret hull, fuel tanks and other systems. One spectacular and fateful showcase of the gun’s detrimental powers was a transmission failure during a field test/maneuver in summer 1978 – which unfortunately included top military brass spectators and other VIPs, who were consequently not convinced of the ZSU-37-6 and its weapon.

The GSh-6-37’s persisting vibration and recoil problems, as well as its general unreliability if it was not immaculately serviced, could not be satisfactorily overcome during the 2 years of state acceptance trials. Furthermore, the large and heavy turret severely hampered Object 511’s off-road performance and handling, due to the high center of gravity and the relatively small chassis, so that the weapon system’s full field potential could not be explored. Had it found its way into a serial production vehicle, it would certainly have been based on a bigger and heavier chassis, e.g. from an MBT. Other novel features tested with Object 511, e.g. the hydropneumatic suspension and the automated 1A27 fire control system, proved to be more successful.

However, the troublesome GSh-6-37 temporarily attained new interest in 1979 through the Soviet Union’s engagement in Afghanistan, because it became quickly clear that conventional battle tanks, with long-barreled, large caliber guns and a very limited lift angle were not suited against small targets in mountainous regions and for combat in confined areas like narrow valleys or settlements. The GSh-6-37 appeared as a promising alternative weapon, and plans were made to mount it in a more strongly armored turret onto a T-72 chassis. A wooden mockup turret was built, but the project was not proceeded further with. Nevertheless, the concept of an armored support vehicle with high firepower and alternative armament would persist and lead, in the course of the following years, to a number of prototypes that eventually spawned the BMPT "Terminator" Tank Support Fighting Vehicle.

More tests and attempts to cope with the gun mount continued on a limited basis through 1979, but in late 1980 trials and development of Object 511 and the GSh-6-37 were stopped altogether: the 2K22 “Tunguska” SPAAG with mixed armament, developed in parallel, was preferred and officially accepted into service. In its original form, the 2K22 was armed with four 9M311 (NATO: SA-19 “Grison”) short-range missiles in the ready-to-fire position and two 2A38 30mm autocannons, using the same 1A27 radar system as Object 511. The Tunguska entered into limited service from 1984, when the first batteries, now armed with eight missiles, were delivered to the army, and gradually replaced the ZSU-23-4.

Having become obsolete, the sole Object 511 prototype was retired in 1981 and mothballed. It is today part of the Military Technical Museum collection at Ivanovskaya, near Moscow, even though not part of the public exhibition and in a rather derelict state, waiting for restoration and eventual display.

Specifications:
Crew: Three (commander, gunner, driver)
Weight: about 26,000 kg (57,300 lb)
Length: 7.78 m (25 ft 5 1/2 in) with gun facing forward
6.55 m (21 ft 5 1/2 in) hull only
Width: 3.25 m (10 ft 8 in)
Height: 3.88 m (12 ft 9 in) overall,
2.66 m (8 8 1/2 ft) with search radar stowed
Suspension: Hydropneumatic
Ground clearance: 17–57 cm
Fuel capacity: 760 l (200 US gal, 170 imp gal)

Armor:
Unknown, but probably not more than 15 mm (0.6”)

Performance:
Speed: 65 km/h (40 mph) maximum on the road
Climbing ability: 0.7 m (2.3′)
Maximum climb gradient: 30°
Trench crossing ability: 2.5 m (8.2′)
Fording depth: 1.0 m (3.3′)
Operational range: 500 km (310 mi)
Power/weight: 24 hp/t

Engine:
1× 2V-06-2S water-cooled multi-fuel diesel engine with 510 hp (380 kW)
1× auxiliary DGChM-1 single-shaft gas turbine engine with 70 hp at 6,000 rpm,
connected with a direct-current generator

Transmission:
Hydromechanical

Armament:
1× GSh-6-37 six-barreled 37mm (1.5 in) Gatling gun with 1.600 rounds,
plus 800 more in an optional, external auxiliary magazine

The kit and its assembly:
This fictional SPAAG was intended as a submission to the “Prototypes” group build at whatifmodellers.com in August 2020. Inspiration came from a Trumpeter 1:72 2P25/SA-6 launch platform which I had recently acquired with a kit lot – primarily because of the chassis, which would lend itself for a conversion into “something else”.

The idea to build an anti-aircraft tank with a gatling gun came when I did research for my recent YA-14 build and its armament. When checking the American GAU-8 cannon from the A-10 I found that there had been plans to use this weapon for a short-range SPAAG (as a replacement for the US Army’s M163), and there had been plans for even heavier weapons in this role. For instance, there had been the T249 “Vigilante” prototype: This experimental system consisted of a 37 mm T250 six-barrel Gatling gun, mounted on a lengthened M113 armored personnel carrier platform, even though with a very limited ammunition supply, good only for 5 sec. of fire – it was just a conceptual test bed. But: why not create a Soviet counterpart? Even more so, since there is/was the real-world GSh-6-30 gatling gun as a potential weapon, which had, beyond use in the MiG-27, also been used in naval defense systems. Why not use/create an uprated/bigger version, too?

From this idea, things evolved in a straightforward fashion. The Trumpeter 2P25 chassis and hull were basically taken OOB, just the front was modified for a single driver position. However, the upper hull had to be changed in order to accept the new, large turret instead of the triple SA-6 launch array.

The new turret is a parts combination: The basis comes from a Revell 1:72 M109 howitzer kit, the 155 mm barrel was replaced with a QuickBoost 1:48 resin GSh-6-30 gun for a MiG-27, and a co-axial laser rangefinder (a piece of styrene) was added on a separate mount. Unfortunately, the Revell kit does not feature a movable gun barrel, so I decided to implant a functional joint, so that the model’s weapon could be displayed in raised and low position – primarily for the “action pictures”. The mechanism was scratched from styrene tubes and a piece of foamed plastic as a “brake” that holds the weapon in place and blocks the view into the turret from the front when the weapon is raised high up. The hinge was placed behind the OOB gun mantle, which was cut into two pieces and now works as in real life.
Further mods include the dish antenna for the tracking radar (a former tank wheel), placed on a disc-shaped pedestal onto the turret front’s right side, and the retractable rotating search radar antenna, scratched from various bits and pieces and mounted onto the rear of the turret – its roof had to be cleaned up to make suitable space next to the commander’s cupola.

Another challenge was the adaptation of the new turret to the hull, because the original SA-6 launch array has only a relatively small turret ring, and it is placed relatively far ahead on the hull. The new, massive turret had to be mounted further backwards, and the raised engine cowling on the back of the hull did not make things easier.
As a consequence, I had to move the SA-6 launcher ring bearing backwards, through a major surgical intervention in the hull roof (a square section was cut out, shortened, reversed and glued back again into the opening). In order to save the M109’s turret ring for later, I gave it a completely new turret floor and transplanted the small adapter ring from the SA-6 launch array to it. Another problem arose from the bulged engine cover: it had to be replaced with something flat, otherwise the turret would not have fitted. I was lucky to find a suitable donor in the spares box, from a Leopard 1 kit. More complex mods than expected, and thankfully most of the uglier changes are hidden under the huge turret. However, Object 511 looks pretty conclusive and menacing with everything in place, and the weapon is now movable in two axis’. The only flaw is a relatively wide gap between the turret and the hull, due to a step between the combat and engine section and the relatively narrow turret ring.

Painting and markings:
AFAIK, most Soviet tank prototypes in the Seventies/Eighties received a simple, uniform olive green livery, but ,while authentic, I found this to look rather boring. Since my “Object 511” would have taken part in military maneuvers, I decided to give it an Eighties Soviet Army three-tone camouflage, which was introduced during the late Eighties. It consisted of a relatively bright olive green, a light and cold bluish grey and black-grey, applied in large patches.
This scheme was also adapted by the late GDR’s Volksarmee (called “Verzerrungsanstrich” = “Distortion scheme”) and maybe – even though I am not certain – this special paint scheme might only have been used by Soviet troops based on GDR soil? However, it’s pretty unique and looks good, so I adapted it for the model.

Based upon visual guesstimates from real life pictures and some background info concerning NVA tank paint schemes, the basic colors became Humbrol 86 (Light Olive Green; RAL 6003), Revell 57 (Grey; RAL 7000) and Revell 06 (Tar Black; RAL 9021). Each vehicle had an individual paint scheme, in this case it was based on a real world NVA lorry.

On top of the basic colors, a washing with a mix of red brown and black acrylic paint was applied, and immediately dried with a soft cotton cloth so that it only remained in recesses and around edges, simulating dirt and dust. Some additional post-shading with lighter/brighter versions of the basic tones followed.
Decals came next – the Red Stars were a rather dramatic addition and came from the Trumpeter kit’s OOB sheet. The white “511” code on the flanks was created with white 3 mm letters from TL Modellbau.

The model received a light overall dry brushing treatment with light grey (Revell 75). As a finishing touch I added some branches as additional camouflage. These are bits of dried moss (collected on the local street), colorized with simple watercolors and attached with white glue. Finally, everything was sealed and stabilized with a coat of acrylic matt varnish and some pigments (a greyish-brown mix of various artist mineral pigments) were dusted into the running gear and onto the lower hull surfaces with a soft brush.

An effective kitbashing, and while mounting the different turret to the hull looks simple, the integration of unrelated hull and turret so that they actually fit and “work” was a rather fiddly task, and it’s effectively not obvious at all (which is good but “hides” the labour pains related to the mods). However, the result looks IMHO good, like a beefed-up ZSU-23-4 “Schilka”, just what this fictional tank model is supposed to depict.

Posted by dizzyfugu on 2020-09-06 09:16:17

Tagged: , 1:72 , zsu-23-4 , zsu-37-6 , shilka , spaag , trumpeter , sa-6 , model , kit , conversion , modellbau , soviet , union , prototype , tank , object , 511 , gatling , gun , 37mm , radar , fictional , dizzyfugu , m109 , turret , GSh-6-37 , GSh-6-30 , Mig-27 , anti-aircraft , test , Donguzskiy , weapon , range , Orenburg