by: Nicola Saggini [ ]
Originally published on:
The Submarine Interceptor
MikroMir 1/350 Project 705/705k [NATO Alfa class] SSN
Introduction – Fact file
Design and Development…
Following the terrible years of the Great Patriotic War, in the 1950’s Soviet society was finally on the rise, opening up new areas of research and development with the protection of the Rodina always as an important national priority. It was a time when designers of the defense industry clearly felt that there were ways to create the best examples of military equipment. Imagination and creativity were at their highest.
In the offices of the Special Design Bureau SKB-143 (later to become known as "Malakhit"), where the first Soviet nuclear submarine, project 627 (NATO November class) was born, and the first submarine with nuclear reactors cooled with liquid metal, the ill-fated project 645, had its keel just laid down, a team of bright and talented engineers, led by Anatoly Petrov, decided to challenge all the design rules adopted thus far and started to work on a submarine interceptor that was supposed to have a full speed of 45 knots submerged, diving depth of 500 m, a displacement of 1,500 tons (the almost contemporary USS Nautilus, by comparison, was around 3000 tons) and a crew of only 15.
Remember that these were the years when speed and diving depths were still considered as the paramount parameters to gain an edge in the war beneath the waves.
In order to achieve these ambitious goals, simplicity and automation were key and the submarine was to have a single hull of lightweight material (i.e. titanium alloy), two-three compartments only (propulsion, conn and living quarters), a single nuclear reactor (preferably with liquid metal coolant), driving a single turbine and a single shaft.
In the minds of the designers, the boat would have had to be used in much the same way that a jet fighter is: while moored in port the submarine interceptor would have been maintained in a continuous state of readiness by a shore crew, that would then hand over the boat to the actual crew of highly trained “pilots” for the mission. These would head out to sea at high speed, complete the mission (attack on a convoy or an aircraft carrier group) and then head back home to rest, while the shore crew took care of the ammunition replenishment and standard boat maintenance.
From March 1960, MG Rusanov was appointed chief designer, and in May of the same year the project received its official designation and endorsement by the Navy and the Government with the number 705, by virtue of a decree formally signed on June 23. The preliminary design was completed on December 31, 1960 and reviewed at a meeting in Moscow with top representative from the Navy and the Ministry of Industry and received strong support since it embodied the latest achievements of science and technology.
All the key elements originally envisioned by Petrov were now to become a reality.
The harshest “fight” was that for a small displacement. Soviet doctrine in submarine design had always been resting on two pillars: double hull and high reserve buoyancy (greater than 30%) to ensure the highest possible survivability of the ship with flooding in an internal compartment next to a blown-empty ballast tank. The original design by Petrov’s team was instead proposing a boat with a single hull and a 10% percent reserve buoyancy, arguing on the fact that the boat would only have three compartments and even a 30% reserve buoyancy does not make a submarine “unsinkable” (as an example for comparison, the Los Angeles class boats have a 11-12% reserve buoyancy). Furthermore, the small crew would be comprised of highly trained officers only, thus reducing to a minimum the possibility of an accident due to human error.
This position was deemed too radical even within the design bureau itself and therefore a first modification was introduced in that reserve buoyancy was brought to 16%. Then, in order to ensure maximum safety in case of flooding of internal compartments, a system of 20 inflatable soft emergency tanks were engineered. They were to surround the single hull and inflate in 60-80 seconds upon triggering of the safety, raising the reserve buoyancy to 54% to bring the boat to the surface and maintain floating.
the same time, even more strongly emphasizing the analogy with an aircraft, it was envisioned to provide the submarine with a pressurized emergency escape module capable of rescuing the entire crew to the surface in case of a sinking, crippled boat.
In both instances, the two systems underwent parallel development and both were eventually built and tested, but only the latter was retained in the final design: in his new role, project leader Rusanov eventually decided to come to terms with the stiff resistance of the Navy for the double hull and an entire re-design of the boat was undertaken during 1963. The “new” project 705 was to have an increase of 15-16% in displacement, a transition from the original 3 compartments to 6 (with 3 compartments only the increase in displacement to keep the reserve buoyancy requirement would have been more than 50%), with a elongation of 8m and a beam increase of 1.3m than the original design, at the price of an expected reduction of 2-3knots in top submerged speed. The inflatable system was at this point useless.
Main contribution to the streamlined hull shape and underwater performance was provided by the R&D work undertaken in parallel by Krylov Shipbuilding Research Institute for a similar type of boat. The Institute was also called to evaluate SKB-143 proposals, which it eventually recommended to the Navy as the next-generation ASW submarine.
Even more after having moved to a double-hull design, it was clear that only the extensive use of titanium alloys for the pressure hull would have kept the displacement low enough to still call it “small”, while ensuring to meet (or at least come close) to the desired diving depth. Indeed, by using titanium compared to steel, an expected 600 tons could be “saved” on the displacement, while setting for a realistic operational depth of 400m.
Unfortunately, the use of titanium posed significant issues. The first being the cost of the material (14 rubles for 1kg plus 20-30 rubles for the machining/rolling at a time when a loaf of bread was 0.02 rubles) but the second and most important was the necessary re-organization of the entire hull production in shipyards normally used to working with steel. Also, in seawater, titanium is extremely aggressive towards all other metals it is in contact with (steel, bronze, etc.), so all equipments that were to be put in contact with the hull had also to be made of titanium, this in the end included the screw, the propeller shaft, pumps, fittings, devices, etc.
But it was the choice of nuclear reactor type that doomed the faith of the project.
Ever since the very beginning, the best solution in terms of power to weight ratio and compactness was identified in the LMC reactor type, that is a reactor using liquid metal in the primary coolant loop vs. pressurized water as it is more customary not only in submarine power plants. One has to consider that these were the early 1960’s, were none of the issues later found with these type of coolants had been identified: the experience on USS Seawolf was not known to the Soviets for obvious reasons, and problems on K-27 did not appear until 1968, before then the design was considered as a success. On paper, the pros were far outweighing the cons: aside for the afore mentioned reduction in volume and mass, the liquid metal coolant did not need very high pressures to operate, thus increasing the inherent safety, and also the reactor did not need to enter different “stages” in order to deliver additional power, as it is the case for the pressurized water type (the Alfa was capable to achieve “full throttle” power output in about one minute, another striking similarity with an airplane). The biggest disadvantage was the need to develop the necessary infrastructure ashore to keep the lead-bismuth eutectic coolant in its liquid state (melting point is around 1700°C) and the removal of oxides in the mixture while the submarine was moored at pier. In the minds of the designers, this would have made it possible to switch off the reactor while not at sea, leading to a much longer life for a single fuelling, de-facto classifying these as “life-of-the-boat” power plants. Reality was much harsher and these projects never fully materialized (see below).
Eventually, two reactor designs were developed simultaneously, both with a thermal power of 155 MW: OK-550 - (three steam generators and three circulation pumps) mounted on a conventional, beam-type foundation by OKBM in the city of Gorky, and VM-40A (two steam generators, two circulating pumps) at OKB "Gidropress" in Podolsk. This latter unit had, for the first time in USSR submarines, the noisiest equipment installed on pneumatic shock absorbers to isolate it from the rest of the hull.
Boats with the latter type of reactor are classified as pr. 750k.
Another innovation was introduced in the generation of electrical power: up until then, all Soviet submarines used the standard 380V, AC current with a frequency of 50Hz. This required large, slow turning generators, transformers and converters. The proposal was then made to switch to a three-phase 380V AC current with a frequency of 400Hz. Perhaps the determining factor in the choice of such frequency was the fact that stand-alone turbine generators of 400 Hz were significantly smaller in diameter, which allowed reducing the displacement of the ship of 400 tons when compared to the standard means.
In the end, all the ships system had to be redesigned to work with this radically new electrical power supply.
This included all the foreseen means of automation that would have enabled the ship to work with a crew of only 15, although eventually the Navy and the government asked to increase this figure to 26 and – in the end – 31. Some sources suggest that the initial number of 15 could not be met as the intended automation to safely operate the boat was not reached and a “traveling” watch across some compartments had to be introduced.
The structure of the automation system can be arbitrarily divided in two multifunctional parts.
The first was a combat information management system (CICS), dubbed "Accord", developed by CDB Kulakov (Chief Designer - A. Turner), able to collect and display information about the position of submarines in the area, the external environmental conditions (including ice), conditions in the internal compartments, radiation environment, boat heel, trim, speed, etc. as well as providing remote control of all mast arrays and management of the torpedo tubes (automatically reloaded).
The second part was a multifunctional complex control system hardware (KSUTS), dubbed "Rhythm" (chief designer - O. Demchenko), developed by the 5th branch of CRI-45 (from 1967 - CRI "Aurora"). It was composed of subsystems for the automated remote control of the reactor ("Gamma"), electric power system ("Voice"), general ship systems ("Beat T") and a centralized control and dislpay of parameters and events ("Melody"). For the pr.705k boats with the VM-40 type reactor, the system was adapted by MA "Sextant" (chief designer - VN Soloviev) and identified by the suffix -200 (thus “Rhythm-220”, “Gamma-200”, etc.).
The two systems were integrated in a U-shaped long console on three sides of the conn, enabling the commander of the submarine to cast a glance to all the crew and, if necessary, in a few seconds decide the appropriate settings, immediately reflected in the remote control stations by the operators via the automated systems.
Due to the complexity in operating all of these systems, for the first time, Soviet submariners had to undergo extensive training both in classrooms for their different skills and specialties, as well as operationally in a newly developed facility that simulated the whole boat and all the different tactical and emergency situations that the crew could face in real life. This approach was later extended to the crews of all other classes of submarines and its founding principles are still valid today.
Another interesting and little known aspect of the ship automation was also that of the galley. In order to keep the crew to a minimum, it was thought possible not to assign a sailor to the specific duty of cook, nor to foresee normal cooking equipment taking up valuable space. It was then decided that all provisions had to be frozen and/or freeze-dried and re-heated and hydrated at the time of eating in the sub in a way later so commonly employed by astronauts and cosmonauts. This in turn required the necessary technology to prepare these foods ashore, which was non-existent at the time.
The keel of the first boat, K-64, was supposed to be laid down in 1964-1965 with a readiness expected by 1968. Two shipyards were tasked with the construction of the foreseen three dozen boats of the class: CVD “Sudomech” – Later CVD Admiralty – in Leningrad and SMP in Severodvinsk.
Delays in the delivery of equipment, poor quality of them and of the raw materials, eventually lead to completion of K-64 only in 1970. In 1971, while undergoing sea trials, one of the primary liquid metal coolant loops broke and later, in early 1972, also the other coolant loop broke. Issues were found in the welding of the titanium piping. Tests pressed on but in April 1972 everything came to a sudden end: coolant in the primary loop froze and the reactor had to be sealed. K-64 was left for two years at pier and in 1974 she was chopped up in three pieces: the nose section was used in Leningrad for training, the reactor compartment was put in isolation on an island near Severodvinsk, while the stern section remained in Severodvinsk, thus earning the submarine the ironic title of “the longest boat in the world”. She was officially decommissioned in 1978 and its crew disbanded.
At the time of the latter failure, construction on the remaining boats was halted and a special commission summoned to investigate the cause of the failure. In 1974, chief designer Rusanov was removed from office, his place taken by his deputy, and construction was resumed. At this point it shall be noted that the submarine force was already fielding other capable submarines, such as those of the Victor class and the emphasis on speed and diving depth was slowly transitioning to stealth and reduction of radiated noise. As a consequence, the government decided to cut production of the Alfa class to 6 boats only, three for each of the shipyards, with those in Severodvinsk fitted with the VM-40A reactor and thus being all 705k.
The last boat was completed only in 1981.
The LMC reactors nevertheless kept proving very troublesome to operate, with another accident occurring in 1982 to K-123 that resulted in coolant spill-over in the stern compartments and radiation activity increase in the whole boat.
Most of the reasons for these and other issues in operating these boats must be traced to the fact that its design was far too ahead of the necessary logistic and maintenance infrastructure ashore, simply not suited to keep up with the complexities of the reactor coolant nor with those of the electronics for the automation of systems.
All boats were retired from service in the 1990’s.
Anyhow it is worth mentioning that the appearance of the boat in the early Seventies did cause major concern in the West for its alleged performances in terms of underwater speed and diving depth (most indeed met by the actual submarine). This is due to the fact that, at the time, ASW weapons in the NATO arsenal were simply not capable of keeping up with such a threat in terms of speed advantage and diving capabilities, not to mention maneuverability (most sources indicate that the Alfa was capable of performing a 180° turn in 42 seconds), even though the US Navy had just started introducing the lightweight Mk.46 and the heavyweight Mk.48 torpedoes.
It is thanks to the Alfa (though the real threat failed to materialize) that improvements in these weapons were introduced and led to the Mk.48 ADCAP and Mk.46–5 NEARTIP and, later, the Mk.50.
For the USSR, despite the superficial bad impression, the Alfa represented a “giant leap” for their submarine design and construction industry. Most of the solutions have indeed been retained by later boats: rescue capsule in the sail, efficient hydrodynamic hull shapes, automation and crew reduction, use of titanium (though this last proved economically unsustainable in the long run). This is clearly testified by the fact that no less than 42 “Hero of the Soviet Union” and “Hero of Socialist Labor” titles were awarded to different designers involved in the project, as well as three Lenin and State prizes and a thousand medals.
Pr. 705 boats are 81.4m long and 10m wide boats. According to some sources, for the “k” type boats length is reduced to 79.4m. Surface displacement is 2300 t for the former and 2280 t for the latter. Submerged displacement is the same, 3180 t.
The Alfa is a double hull boat made of titanium alloy, with the internal pressure hull divided in 6 compartments. The outer hull has a very streamlined contour with the sail gently bending into the overall shape (the Russians call this “limousine” type). The boat has forward retractable diving planes and a classic cruciform tail, culminating in a 5-bladed fixed pitch propeller of very simple shape.
Speed is 14 knots surfaced and 40 knots submerged (up to 43 for pr.705k), with a reported maximum safe dive depth of 500m. To assist the boat during maneuvers, two 100kW DC motors housed in the horizontal tail planes drive each a small diameter, twin-bladed propeller..
Main power plant is rated at 155MW and is either made of a OKB-500 or a VM-40A reactor, both cooled by a liquid lead-bismuth eutectic metal alloy driving a UC-7 turbine rated at 40000hp.
The electric power system consists of two 1500kW autonomous turbo-generators, producing an alternating current of 380V, 400 Hz. Alternatively, an auxiliary diesel generator rated at 500kW is available as an emergency back-up.
The submarine carries sufficient supplies for an endurance of 50 days and is operated by a crew of up to 32, all officers except one petty officer.
Weapons are “limited” to six 533mm torpedo tubes, capable of launching torpedo types SAET-60 and SET-65 (according to some sources also the rocket-torpedo type 82-P, i.e. SS-N-15) with a reserve of 20 weapons. These could be exchanged for mines type PMR-1 or PMR-2.
In the box…
The kit is built by MikroMir, apparently a company founded on the ashes of AMP and that has lately ventured into the 1/350 styrene submarine market with at least another three boats: WWII USSR K-21 boat and US Navy Permit and Sturgeon classes, not to mention bigger scale “special projects” boats like the Neger human torpedo or the Russian “Pirahna”.
sample arrived directly from Ukraine after a four week trip. A little cardboard box displaying an art work of the submarine on the surface in the arctic protects the contents of this little kit. Inside come the two hull halves split at the boat middle line (i.e. no waterline readily available), with the top one carrying integrally the sail, and one sprue with the remaining of the parts all in a large zip-lock bag. Inside a separate, smaller bag are the decals and a tiny photetched sheet.
The single sprue carries all details: top rudder, bow and stern horizontal dive planes, reactor water intakes, the propeller hub and four parts that make up the very simple stand. No masts are provided (see below).
There is a fair amount of flash on most parts which make me think of other eastern short run kits, and in some areas the plastic is marred by other colours, maybe a result of the moulding extraction process.
Total styrene part count is 18.
The little bag contains the decal sheet mostly comprised of white draft markings, four different hull numbers (generally not seen on operational boats except for parades or inspections) and the emergency buoy markings. The tiny photo-etched set consists of the cockpit windscreen (finally a touch that most larger manufacturer ignore) and the blades for the main screw as well as those for the two creeper motors and, again something of a first for a styrene kit, the four small arms of the cruciform vortex attenuator downstream of the main propeller.
Unfortunately the instruction sheet (if any) didn’t make it to my doorstep. Thanks to the endless resources of the world wide web I was able to find scan copies of the instructions. It is a folded little poster that starts with an introduction on the boat history and operations in Russian and English, the boat specifications (where length is specified as 79.6m – see above) and decal placement and color guide. On the back side the part layout is presented (and shows I did not get the little transparent windscreen to be inserted in-between the PE fret either!) and then a 7-step straightforward assembly guide: cockpit floor assembly, mating of the hull halves and reactor water intake scoops, windscreen assembly, screw sub assembly, cruciform tail construction, stand.
Given the very small part count though, the kit looks fairly straightforward to build and nothing that should scare even an average model (indeed I was able to source the instruction only after I had started working on the model).
Dimensions: the model measures 224mm in length with an additional 6mm of the hub, for a total of 230 mm coming pretty close to the 232.5mm that would translate to the 81.4m of the real boat. If the 79.6m length is considered, this would translate in 227.4mm
Beam is 27mm vs. the “nominal” 28.5mm.
Sail placement appears to be perfectly in line with my references. All hatch outlines are very finely engraved and also appear numerous and very much in line with available reference profiles and pictures.
The safety line rail that runs along the entire length of the hull is represented as a finely raised feature and the track matches almost perfectly my references: it correctly interrupts at the sail but the stern part should start approximately at the same height of the crew access hatch on the sail port side.
Bow to Stern look at the details:
Torpedo tubes are correct in number and placement but perhaps they should be just a tiny bit larger in diameter.
Forward retractable depth planes/stabilizers are correctly placed and present a swept appearance as the real ones. The modeller can leave them out as their outline is anyhow present on the hull.
Limber holes in the outer hull (the openings that are used to flood the space between the outer and inner hull, typical of Russian submarines) are 100% correctly located when compared to my references. As usual with Russian/Soviet submarine kit, there is always the added challenge should the modeller wish to represent them open as they can be seen on most pictures, but given the size of the kit I would (and will) personally not bother.
o Shape is overall correct and in line with pictures and profiles I have when looking at it from all angles. It does blend very gently into the hull and really conveys the sense of the “limousine” type hull (see above). The only very slight issue is on the aft part: here there is less of a gentle blend and this is similar to the real boat, except that perhaps the noticeable separation line should extend more forward in the kit representation. This is perhaps the only, very very small defect that I can find.
o Forward crew access hatch and Yenisey passive hydro-acoustic sensor suite outlines are correctly represented.
o Moving atop of the sail, the first area encountered is the little tiny hatch of the forward navigation light correctly represented. Just aft and immediately forward of the cockpit are the two hatches of the communication masts. As all the other masts on the sail, these are all very well represented but only in the closed position, giving no choice to represent the masts raised unless some serious scratchbuilding is undertaken (mast hatches must be drilled out and some have very complex contours, inside the sail some base must be glued and the masts themselves scratched or sources elsewhere). This is the second shortcoming of the kit and IMHO perhaps the most significant one.
o Just a bit aft is the the cockpit: it sports an overall correct appearance in shape and position. Its floor must be built using three parts on the sprue (this is my guess as otherwise there would just be a through hole, but bear in mind that I have no instructions!). Looking at the parts, I think it might end up being too deep within the sail (scaled to reality it would amount to almost 2m in depth). It is nevertheless missing all the interior details: the crew access hatch on the port side and the communication/navigation equipment in front. As already mentioned, kudos to MikroMir for providing a very nice windscreen in PE (note that this on the real boat folded down flush with the sail: not sure if this can be done with the PE and it would anyhow need an additional hatch to cover the remaining part of the cockpit).
o Outline of the crew escape module is correctly represented.
o Location of all remaining masts is perfectly outlined (shape, dimension, position) but, as already mentioned, only the “closed” option is provided.
o Crew access hatches are correctly represented on port and starboard sides of the aft part of the sail at the junction with the hull.
Moving aft back on the hull, the emergency buoy is correctly represented, perhaps just a little too prominently: should be raised but not as a “dome” as it is in the kit.
Reactor water intakes are provided as separate parts to be glued on their outline provided on the hull. No grid in front of them is provided and will have to be scratched.
Rudders and aft depth planes are all correctly represented and their “roots” are molded integrally on the hull for a very gentle blending. Only small fix: the top rudder as a v-shape cutout (on the real boat it houses the stern navigation light) and this must be carved out by the modeller, although the outline is there.
Creeper motors on the Alfa are in pods which are an integral part of the stern dive planes and are correctly represented.
As already mentioned, the “screw” is made up of a styrene hub and PE blades and cruciform attenuator arms (a total of 10 parts!!) for I think a very convincing look once properly assembled.
A final word for the stand which is very simple (on the verge of being crude), made of two beams that connect two little concave webs.
Building the kit…
Preface: I am no expert modeller so most of what I will be reporting here can be biased by my very own set of skills. I will nevertheless try to keep it as factual as possible, also with the help of pictures.
I started by assembling the cockpit floor which is very basic and also gluing of the reactor water intakes to the bottom hull. Some pressure is required to make them conform to the hull contour as they have a flat bottom surface coming off the sprues. Their location is provided in the form of an outline on the hull, no reference pins or recess is provided.
Then attention turned to mating of the hull halves: at dry-fit, parts appear a tad warped, the bow section in particular, failing to meet at the centreline, unless very generous pressure is applied. No reference pins or other form of mating references are provided. I chose to carefully start the assembly from the stern and proceeded forward one little step at a time. In the end I managed to get an average joint all throughout not requiring an enormous amount of putty.
The stern section was tackled next. Again no guiding pins or other form of mating references are provided on either part, so I started with careful dry fitting to spot any issues. In an effort to vary a bit the look of the boat I decided to show the stern dive planes in the dropped position (as it is common when the boat is in drydock) and so I cut them out. I then joined first the horizontal planes and then the vertical (rudder).
Moving further astern, I then started the propeller attenuator and then decided to join the hub to the hull as the fit did not look the best (again no guiding “peg-in-a-hole” type is provided) and wanted to avoid doing it with all the PE blades installed for fear of damaging them.
Finally I installed the bow diving planes (on one of the two there is a small pin, though no hole on the hull) and the PE screw blades for the main and auxiliary motors. A comment on these parts: although a rather simple propeller compared to more recent submarines, the Alfa screw did have a bit of “skewing” (rotation between the root of each lobe at the attachment on the hub and the tip). I would have liked to replicate this but given the thickness of the fret it is next to impossible (at least for me).
The PE windscreen is very last but I will install it only after painting.
Despite coming from a somewhat obscure manufacturer, this is a great representation of a little gem of a submarine and a must have for any modern submarine collector.
It is light years ahead in accuracy of its only other current competitor in styrene.
Assembly is eased by the very small part count, yet is not super straightforward due to the absence of any reference when mating surfaces. Careful dry-fit of parts is strongly encouraged.
My personal advice: get it before they stop making it!