Project 941 Akula / TYPHOON - Design
In the early 1980s, nuclear strategic missile submarines of the project 941 “Shark” began to be introduced into the structure of the Navy of the USSR. These were the largest submarines in the world - their size is recorded in the Guinness Book of Records. The "sharks" were also the only submarines of the catamaran type in the world - they had two independent hulls, between which there were missile launchers. This design significantly increased the survivability of the submarine cruiser, but it was also his main curse.
The Project 941 boats were by far the largest submarines in the world to use Titanium for their primary pressure hull. While Western intelligence quickly suspected the use of Titanium in high-speed attack submarines such as the Project 661 - Anchar / Papa, the Project 685 - Plavnik / Mike , the Project 705 - Lira / Alfa , and the Project 971 - Shuka-B / Akula, there was no indication in the open literature that the TYPHOON might also feature this material. Whether the intelligence community realized this at the time of their construction awaits further declassifications.
The architectural scheme chosen for the Project 941 submarine was a forced solution. The boat was required to surface through the Artic ice under any circumstances, and this required enornormous reserve bouyancy to force a hole throught the overlying ice. Further, the missiles, designed to become the "main caliber" of the submarine cruiser, turned out to be long and heavy. This led to an increase in ship displacement, which in the submerged position reached 48,000 tons. But even with this displacement, as well as a length of 172.8 meters and a width of more than 23 meters, the ships of this project were among the lowest noise among Soviet submarines. Two pop-up rescue chambers, designed for the entire crew, are located at the base of the cabin under the sail.
The Soviet Typhoon-class, nuclear-powered, ballistic missile submarines (SSBNs) were the world's largest submarines. Its surfaced displacement was over 24,000 tons, about one and a quarter times that of the US Ohio-class SSBN. Surfaced displacement is an indicator of the pressure-hull internal volume of a submarine and is used most often as a representation of submarine size. The height from the keel to the top of the cabin fence is 25 m, which corresponds to a seven-story house, and, by the way, with high ceilings. And with the pull-out devices raised, a nine-story house is already being made. Such dimensions were determined by the dimensions of the new three-stage solid-fuel intercontinental ballistic missiles, which were planned to arm the boat.
However, another characteristic, full submerged displacement, which is the weight of seawater equivalent of the envelope: volume (the total volume within the submarine's outer skin), better illustrates Typhoon's overall size. Typhoon had a full submerged displacement of about 48,000 tons, two and one-half times that of an Ohio-class submarine and about the same as the displacement of a Wolr War II battleship. Although Typhoon and Ohio were similar in length, Typhoon had a greater beam and hull depth, which resulted in its larger envelope volume. When diving, the entire space between the sides is filled with seawater, and the boat accelerates and drags all this mass of water along with it. Water is the total moving mass, which determines the inertia of the boat, and hence its maneuverability. Of the boat's full underwater displacement, exactly half of the weight is ballast water, which is why the boat is sarcastically dubbed the "water carrier".
The submarines of this series (Project 941, or Typhoon, according to NATO's classification) are considered the biggest in the world. Their length of 124 meters is comparable to two football fields, while the height of this naval predator is that of a nine-story building. All six Akula submarines (the name means “shark” in English) have been included in the Guinness Book of World Records. The impressive dimensions of the vessel were necessary in order for it to be equipped with non-standard sized ballistic missiles, which normal submarines were unable to carry.
Typhoon was more than just big; it was very different in concept. Typhoon was an unusually arranged submarine. It had two main pressure hulls in a "catamaran" configuration. Analysis of external features indicated that it also had a small pressure hull above the main hulls for submarine control functions and a small pressure hull at the bow for defensive (torpedo) armament. Its main missile armament was carried within the outer hull between the main pressure hulls, forward of amidships.
They were the first class of submarines to be built using a radically different design concept, that of the very large submarine (VLSS). In contrast, the US Ohio-class SSBNs, though large, were designed with a more traditional arrangement. The VLSS was as major a design innovation as the VLCC [Very Large Crude Carrier], thc super tanker, was in surface ships. Both exceeded established size barriers, using innovative approaches in design.
The design of the Typhoon submarine is multi-hulled and bears resemblance to a catamaran. The outer contours of the boat resemble a flat bread stub, but this is only the shape of the outer thin and light body. Its purpose is to reduce the resistance when moving under water. Inside it is a robust housing with machines, mechanisms and people living among them. This inner durable case " Typhoona ”is unique: no one has ever done such a thing. It consists of two parallel cigar-shaped cylinders with a diameter of 10 meters each with three transitions through intermediate compartments: in the bow, in the center and in the stern. Thus, it turns out that two boats are placed in one general light hull. They are commonly referred to as “starboard” and “starboard”, meaning in this case the entire left and right cylindrical cigar. Everything is duplicated in these strong sides: reactors, turbines, all mechanisms and even cabins, so that there are two in the rocket carrier. And if in one half everything refuses, the other will allow you to fully complete the combat mission and return to the base.
In order to distinguish between the left and right sides, it is customary to number everything on the left with even numbers, and everything on the right, to be odd. By the way, all the specialists in the team also have exactly a pair, and they are called specialists of the right and left sides. Between the light external and durable inner hulls there is a fairly large space where diving tanks are placed, all kinds of tanks and in general everything that can not be protected from high pressure and the action of sea water. And the containers with missiles are also located at the Typhoon A in this space: between the sides - in front of the boat, before chopping. By the way, this is the only rocket boat whose missiles are located in front of the wheelhouse. Other boats, as it were, “drag” the missiles behind them, and “ Typhoon»Their rockets" pushes "ahead of themselves.
The submarine has two separate pressure hulls with five inner habitable hulls and 19 compartments. The pressure hulls are arranged parallel to each other and symmetrical to a centerplane. The missile compartment is arranged in the upper part of the bow between the pressure hulls. Both hulls and all compartments are connected by transitions. The pressure hulls, the centerplane and the torpedo compartment are made of titanium and the outer light hull is made of steel. A protected module, comprising the main control room and electronic equipment compartment, is arranged behind the missile silos above the main hulls in a centerplane under the guard of retractable devices.
The submarine's design included features to enable it to both travel under ice and for ice-breaking. It has an advanced stern fin with horizontal hydroplane fitted after the screws. The nose horizontal hydroplanes are in the bow section and are retractable into the hull. The retractable systems include two periscopes (one for the commander and one for general use), radio sextant, radar, radio communications, navigation and direction-finder masts. They are housed within the sail guard. The sail and sail guard have a reinforced rounded cover for ice-breaking.
The submarine is equipped with the D-19 launch system with 20 solid-fuel propellant R-39 missiles which have a range of up to 10,000 km. They are arranged in silos in two rows in front of the sail between the main hulls. The Typhoon has an automated torpedo and missile loading system including 6 torpedo tubes with calibres of 650 and 533 mm.
The main machinery consists of two OK-650VV reactors each and two steam turbines of 190 MW that provide a maximum speed of 25-27 knots. Compared to the first and second generation of SSBNs the Typhoon enjoys far greater maneuverability Despite of its larger displacement the Typhoons are less noisy than their predecessors. To reduce the acoustic signature a two-spool system of rubber-cord pneumatic shock-absorption is employed as well as a block layout of gears and equipment, a new sound isolation and andrihydroacoustic coating.
The Typhoons are equipped with the "Slope" hydroacoustic system that consists of four hydroacoustic stations. The "Slope" system allows to track 10-12 vessels simultaneously. It also employs two floating antenna buoys to receive radio messages, target designation data and satellite navigation signals at great depth and under an ice cover.The high freeboard meant relatively dry decks when surfaced in rough seas, minimum icing in Arctic operations, and a good "height of eye" for its conning officer. The latter is of particular advantage when operating in areas of broken ice. By spreading Typhoon's buoyancy transversely with parallel pressure hulls the Soviet designers have attained a high value of surfaced stability. The analogy of a floating log illustrates this point. One floating log has little stability in roll: however two logs fastened together to form a raft, have much greater stability. So it is with Typhoon.
One disadvanteges was high hydrododynamic resistance. The major resistance component of a submerged submarine is frictional drag. This varies approximately with the submarine's surface area. Typhoon's immense outer envelope implies high drag and, thus, high propulsion power requirements, There is an economy of scale, however, which favors a larger submarine. As hull volume becomes larger, surface area increases at a lesser rate.
The submarine's large mass is a disadvantage for which there seemed to be no compensating hydrodynamic advantage, A submarine travelling submerged at neutral buoyancy has a mass equivalent to the mass of seawater of its outer envelope. When the submarine changes speed, the entire mass must be accelerated. The "battleship size" mass of Typhoon implies that it is a very sluggish submarine. This is especially important when accelerating the submarine from rest, because marine propellers arc inefficient at low speeds.
Ship handling problems resulling from unusual size are not new. When the very large crude carrier (VLCC) came into being, experienced merchant masters assigned to them had great difficulty in ship handling. Spccial training facilities were established using miniature ship models capable of carrying one man. These models were "scale powered," using very low powered propulsion systems. The models were ballasted and their control systems were arranged to simulate as closely as possible the sluggish behavior of the VLCCs. Training with these models increased master confidence and provided hands-on experience in miniature before the masters faced the real world of VLCC operation.
Almost as soon as marine nuclear power became practical. there wcre design proposals for non-military submarines with deadweight cargo capabilies too large to be built with simple circular pressure hulls and still have surfaced drafts compatible wilh normal channel depths. In 1958 the US Maritime Adminislration contracted with General Dynamics Company to study submarine tankers. General Dynamics developed several designs with deadweights ranging from 20,000 to 40,000 tons. In Japan, Mitsubishi, Ltd, developed a design for a 30,OOO ton tanker; and in England. Mitchell Engineering/Saunders-Roe advanced the possibility of a submarine tanker of 80,000 to 100,000 deadweight tons. None of these designs were ever built because of economic and nuclear safety considerations. Nevertheless, the design philosophy of these large submarines, with unusual hull arrangements, became well known and was recognized early by the Soviets.
In 1964 Sudostroyeniy (Shipbuilding) Publishing House in Leningrad published a book on nuclear powered submarine design. The authors discussed the very large submarine in detail. They commented on both potential military and nonmilitary uses including ballistic missile carriers, aircraft carriers, transports, and oiler/supply ships, as well as merchant tankers and dry cargo ships, They commented on the economic infeasibility of the VLSS for merchant use, but they stated that "in wartime only submarine cargo carriers, possessing so important an advantage as secrecy, will be able to effectively supply bases, operating forces, and individual combat ships with fuel, combat supplies, provisions, etc."
Typhoon had design characteristics difficult to attain in combination in a more conventionally designed submarine. Among these were extremely large volumes inside its outer envelope and very large, pressure-tight internal volume, with reasonable and variable surfaced operating drafts. It had the potential to carry both offensive (missile) and defensive (torpedo) armament totally within the submarine's outer hull envelope but external to its main pressure hulls. This allowed the design to be developed for other purposes without disrupting the pressure hulls and with little or no change to the submarine's hydrodynamic characteristics.
By using the VLSS concept in Typhoon, the Soviets produced a design with unusual potential for future development. Soviet open-source literature described a number of unusual military applications for very large submarines. Included were oiler/supply ships and troop transports. The Soviets saw such ships as particularly useful in the far north where port facilities are minimal and are iced in much of the year. CIA believed that the Typhoon design could also be developed into a naval staff command ship or a mother ship for mini submarines.
The missile carrier is equipped with emergency surfacing chambers that are designed to rescue the entire crew in case of disaster. The light body is covered with a sound-absorbent rubber material, whose total weight is 800 tons. This special covering, which helps the submarine to avoid being detected, gives the vessel the appearance of a gigantic rubber toy.
In order for the boats to be able to keep watch at high latitudes, the cabin fence is very strong, able to break through ice 2-2.5 m thick (in winter the ice thickness in the Arctic Ocean varies from 1.2 to 2 m, and in some places reaches 2.5 m). Below the surface of the ice is covered with growths in the form of icicles or stalactites of considerable size. When ascending, the submarine cruiser, removing the nose rudders, slowly presses against the ice ceiling with a specially adapted nose and fencing for cutting, after which tanks of the main ballast are drastically blown through. The main command center is where all the vessel's systems are controlled: the helms, missiles and radio-technical weapons. In essence this is the submarine's brain. The submariner initiation ritual also takes place here. The submariner initiation ceremony is performed for everyone who is about to submerge, regardless of rank or position. While underwater, the sailor must drink a flacon of seawater. Then he must kiss a swinging sledgehammer, which on the Akula is a club ("bulava" in Russian), a reference to the homonymous missiles that were tested on the vessel. The most important thing in this procedure is not to be hit on the teeth. Whoever performs the ritual successfully receives a submariner certificate and, depending on the crew's mood, a present in the form of a roach, and sometimes even a "commemorative stamp" on his derrière.
The program envisaged an unprecedented schedule for the service and operation of submarines. In the Moscow region, in the city of Obninsk, a special training center was built under this program with housing, kindergartens, schools, hospitals. In it, replacing each other, the crews of submariners were to be trained on a completely new technique. For each submarine cruiser was supposed to have three crews: two combat - for combat service at sea and one technical - for troubleshooting, inter-repair repair and preparation for a new march in the database. The mode of operation of the crew was supposed to be.
The first combat crew is on the alert for two or three months at sea, during which some malfunctions inevitably accumulate on board. Upon arrival at the base, the ship is handed over to the technical crew, and the combat ship - right on the pier, with personal belongings, loaded into comfortable buses and sent to the airport - straight to a specially ordered aircraft. Next - a flight on the route Murmansk - Moscow, after which, taking their families, everyone goes on vacation to different parts of the country. Meanwhile, the second combat crew, tanned, rested and tired of family comfort, flies with families from all over the country in the Moscow region, to Obninsk. Here, submariners - to refresh their memory and skills - are driven through all the simulators, they take tests and, confirming, finally, their high combat capability, they fly with Moscow-Murmansk return flight. Then the crew goes back to their cruiser, already fully prepared for a new combat campaign. A boat is taken from a technical crew, a ladder is taken away, and the ship leaves for military service, managed by a second combat crew. In the same way, the whole process is repeated over and over.
The Project 941 submarines are unique not only for their size and power, but also for the comfortable living and working conditions on board. For this the project has been named the “floating Hilton.” They were the most comfortable for the crew. When designing " Typhoon”, apparently, did not particularly strive to save weight and dimensions, and the team was placed in 2, 4 and 6-berth cabinets that were sheathed with wood, with desks, bookshelves, clothes lockers, washbasins and TVs. Typhoon had a special complex for recreation: a gymnasium with a swedish wall, a crossbar, a punching bag, cycling and rowing machines, treadmills. The exercise equipment to the left was developed by a leading nuclear submarine designer, the Rubin Design Bureau, while the one on the right was donated by patron organizations. True, some of this - in a purely Soviet way - did not work already from the very beginning. There are four showers on it, as well as nine whole locks, which is also quite significant. The sauna sheathed with oak boards, generally speaking, was designed for five people, but it could accommodate ten. And there was also a small pool on the boat: 4 meters in length, two in width and two in depth. It can be filled with fresh water as well as seawater and can be heated.
The main external enemy of submarines is noise. It unmasks the boat, that for an underwater missile carrier in general is a matter of life and death. It turned out that in " Typhoon e" the interaction between simple, lightweight and complex rugged housings made it possible to achieve unprecedentedly low noise levels. It turned out at " Typhoona ”and one more - quite unexpected - the result. It is said that once somewhere in the Spitsbergen area, a blue whale female took our cruiser as a male whale and circled around for several hours, apparently trying to mate with him. She made a roar, turning into a whistle, and the acoustics even managed to record this love serenade on a magnetic tape. They also say that orcas sometimes rub against the hull of a ship and crack and whistle at the same time like birds to the whole ocean. For whom they take the cruiser, is not completely clear, but clearly for someone of their own. And in any case, it is obvious that the noise characteristics of the " Typhoon A " sea creatures are not deterred, but even vice versa. The achievement is very curious, although it is hardly planned in advance.
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