Length: 91 m.
Width: 10.5 m.
Displacement: 5,946 tonnes surfaced, 6,312 tonnes submerged
Propulsion:
- 1 S1WA Pressurized Water Reactor.
- 1 Diesel Electric Engine (10 MW, 13,410.22 hp).
- 6 Pump-jet intakes.
- 1 Propulsor.
Speed: Up to 51 km/h.
Range: Theoretically unlimited, 95 days on supplies.
Complement: 80 crew + 12 special operators.
Electronics:
- Eisen-Schloss Combat Networking (MEER Command & Control).
- MultiSensor Observation Mast (EO/FLIR, HD Camera, HRR InGaAs Laser Diode Pumped Laser Rangefinder).
- Ka-band SATCOM.
- Underwater Communications Reel (tether).
- IFF ES/A/N/F (friend-or-foe/transponder system).
- NET-S System (CESM/COMINT).
- GPS Navigation System.
- Inertial Navigation System.
- JSSN-S X-band (FMCW) LPI Navigation Radar.
- UISS (Underwater Integrated Sonar System).
- USS-1B TSA15 (towed array sonar).
- WA-PFASS (passive long range sonar).
- USCS (submarine countermeasure system).
- 6 533mm Torpedo Tubes (35 munitions, including torpedoes, missiles, and mines).
- 4 Underwater Submarine Modules (8-6 cruise missiles, 1 ballistic missile, 12-8 surface-to-air missiles, 1 special operations team, and 1 unmanned underwater vehicle per module).
- 18 CT-12 Decoys (anti-torpedo decoys).
Emergency Systems:
- Emergency Submarine Rescue System (ESRS).
- Emergency Dual High/Low Frequency Sonar Beacon.
- Emergency Radio Beacon.
- Submarine Escape Immersion Equipment Mk. X.
Background
The Katzenhai SSN (Dogfish) is a class of advanced nuclear powered multipurpose attack submarines designed by Wolf Armaments in conjunction with the TECT Imperial Navy's Naval Design Committee. INS Irmtrud Kistler, the honorary class leader (named in honor of Cpt. Irmtrud Kistler, a forty year careered submarine captain who passed away in 2008), first set sail with the Imperial Navy on January 1st, 2017 on its first deployment to the Royals Eastern Sea. Katzenhai, or "dogfish" in english, are small bottom feeding sharks that inhabit coastal regions surrounding TECT; although species are often named 'catfish' and 'dogfish', they all come from the same Scyliorhinidae family and are commonly referred to as simply "dogfish" by Commoners - dogfish, as a result, has become a common alternative term for sharks or more specifically "small sharks" within TECT. Dogfish/Catfish, like most bottom feeders/hunters, prey on a wide variety of fellow bottom dwellers, including crustaceans, cephalopods, fish, and even other sharks. Their stealthy exterior and swift speed make them ideal hunters in their environment and thus are aggressive and fiercely territorial - a worthy namesake for any submarine class. Although often caught by accident by bottom trawlers in the past, dogfish have more recently become a source of fish meat and leather for seaside communities; they have become popular coastal dishes in restaurants around TECT and beautiful leather products sold in many shops. These two factors combined have done serious harm to Dogfish populations to the point that the Internal Affairs Ministry has enacted policies to protect Dogfish, among other underwater creatures, from overtly harmful practices outside of legal fishing industries, and have instituted fishing quotas to protect populations from over-fishing.
In an effort to domesticate naval production, Emperor Charles II demanded that Wolf Armaments begin focusing on developing shipyard operations; he specifically wanted to domestically produce native designed warships and cut reliance on foreign companies. The Emperor convinced Congress to ease business regulations and he also approved many buyouts to boost Wolf Armaments' push into the shipyard industry; these actions greatly assisted Wolf Armaments by creating less restrictions on purchasing property, acquiring materials, and acquiring research grants. Wolf Armaments boosted its development by taking over small shipyard companies and other marine manufacturing facilities - which helped it acquire shipyards to use and learn from as well as new employees with years of experience in the field of marine construction. At the same time, Colonial Shipyards Inc. agreed to a merger into Wolf Armaments - the deal brought the Empire's largest warship manufacturing company, which produced the vast majority of domestically constructed military vessels that licenses had been purchased from overseas companies, into the much larger Arms manufacturing corporation. This huge industry merger immediately made Wolf Armaments the number one company in the shipyard industry for military vessels, allowing it to finally begin work on designing native military vessels, naval warfare technology, and begin competing with similar shipyard businesses around the world.
The Emperor greatly wanted to replace Triumvirate Enterprises, a longtime supplier to the Empire in naval vessels and technologies, as his country's supplier of naval ships and technology; his idea being that producing domestic vessels would eliminate dependency on foreign suppliers/designs, enrich naval and technological innovation, and secure manufacturing jobs for Commoners which before relied on the country paying license fees to build foreign designs - the benefit of exports in the naval sector would boost the country's GDP along with the combating of the Empire's unemployment rate. The country's military budget would also see savings due to the cheaper price tag of the ships and other expenses that had to be paid for construction and delivery. By 2004 Wolf Armaments was well established in ship manufacturing with shipyards, research facilities, and manufacturing plants around the country; it had taken over domestic production of military shipping and had even formed a powerful design committee for inventing new native warships. The same year Wolf Armament's Naval Design Committee began work on multiple designs. Initially, Wolf Armaments set out to design replacements for already ailing classes and required warship types. Destroyers, cruisers, frigates, and a variable amount of other smaller ships were becoming obsolete or were not designed with TECT preferences in mind. The already outdated battleships and stale variety of warships were beginning to threaten Commoner naval supremacy.
Katzenhai would become the first ship class designed by both the Imperial Navy's "Naval Design Committee" and Wolf Armaments' Shipyard Division after the initial rush to design domestic warships for the Imperial Navy (2004 to 2016). Even as it bought new submarines abroad, the Imperial Navy was beginning a new age of revitalization and domestication of submarine technology with the intention to domestically produce submarines. Although Wolf Armaments had been experimenting with leftover submarine technology from its absorbed predecessors nearly a decade prior, no working prototypes or even design models had been produced; this was a consequence of the Imperial Navy's urgent demand for surface vessels alone and not enough available resources to pour into submarine development. Surface ships were in far more need of modernizing than subsurface ships and in fact most submarines within the Imperial Navy were already fairly modern, leading to the conclusion that surface ships were a larger national security risk while submarines weren't. After the decade long rush to complete needed surface classes was over, however, these submarines had found themselves in a dangerous state of inefficiencies when compared to overseas rivals. Losing their cutting edge, too few in number, and under performing, many of the classes used by the Imperial Navy had been greatly overestimated before the rush had even began to the point they were now seen as burdensome. To help alleviate the problem during the "Surface Rush" as many would call it, the Imperial Navy purchased a number of LA-602 Kukri submarines from the Free Republic of Lamoni while the Imperial Government acquired a domestic production agreement to manufacture these submarines domestically; since Wolf Armaments had a lucrative manufacturing and distribution contract from the Lamonian Government, Wolf Armaments could produce these ships domestically for the Imperial Navy at a cheaper price and sell them to export customers to make a profit - a "win-win" scenario according to Imperial officials. But putting a band-aid on a wound is only a temporary solution that the Imperial Navy knew all too well. A more permanent solution to the Imperial Navy's submarine predicament had to be found.
Even as other surface projects rolled on, the Imperial Navy's Naval Design Committee reached out to Wolf Armaments in an effort to launch joint projects to develop submarine technology and eventually produce working submarine models; this joint effort eventually went on to be called "Projekt-Dreizack", or "Project Trident" in English. Projekt-Dreizack, according to unclassified Congressional reports authored by the Armed Forces Committee, is an "ongoing underwater naval research & development, acquisition, and production program spearheaded by the Imperial Navy with partnered armaments/technology companies. It's stated mission is the development of underwater technology for use with submarine platforms (including submersible weapons and vehicles), the acquisition of such technology/platforms from partners for use within the Armed Forces, the furthering of research for military related underwater subjects, and the eventual green lighting of product models for eventual foreign export." While many prototype technologies and concept designs were drawn for future development, Projekt-Dreizack's first priority continued to be the development and production of working submarine models and their internal systems/armaments. "Concept Katzenhai", as it would soon be known by, would become the first submarine design concept made into a working prototype and eventually launched as the Project's first successful creation.
Projekt-Dreizack leadership had authored an analytical study early-on to explain what it believed should be the strategy used when developing the Empire's future submarine fleet. Known as the "Three Tier Study", Projekt-Dreizack leaders arranged submarine warfare into tiers of three modern engagement theaters that would define the tasks any submarine in that respective theater of expertise be expected to accomplish; submarines would be designed to fulfill a tier's many expectations and would have their hull, armaments, equipment, range, and capabilities catered to their tier/theater requirements while still maintaining Wolf Armaments/TECT's modularity design focus. These theaters include tier one, "Domestic", which is described as operations conducted within the waters of the Empire or near it (within six thousand kilometers or less) that classify as domestic naval operations; tier two, "Expeditionary", are theaters outside home waters or operations with set expeditionary missions (beyond six thousand kilometers or submarines deployed in offensive/expeditionary operations overseas); and tier three, "Strategic", is any theater around the globe with strategically valuable assets or goals in mind (ballistic missiles and TECT's nuclear umbrella). Utilizing tiers of responsibility would essentially establish a goalpost for project designers to build submarines with the appropriate features and specializations tiers/theaters would require. Katzenhai would go on to be designed to fulfill the Project's first tier role, a role envisioned mostly as defensive in nature; marketing-wise, both parties (Wolf Armaments & the Imperial Navy) believed Katzenhai to be profitable as an export due to its size, cost, and modularity. Such duties would entail standard maritime patrols, counter-submarine operations, convoy/fleet protection, and intelligence gathering operations. In the worst case scenario, Katzenhai submarines are still suitable for expeditionary operations, thus improving their value within the Imperial Navy.
Development on the first model (INS Irmtrud Kistler) took place slowly near the end of the Surface Rush with prototype miniature test models undergoing experimentation in late 2014. While Katzenhai's components were experimented with in outside conditions, these test models were used for layout configuration, brainstorming, and basic seafaring tests to gauge performance in sea conditions. Development was bolstered in 2016 with the last of the required surface vessels being developed and launched, leaving Wolf Armaments (and the Imperial Navy plus its other partners) the necessary resources for Projekt-Dreizack. Each section of INS Irmtrud Kistler was designed and built in portions with some sections finishing early or even needing reconfiguration later into development due to related changes in the design; everything from components, to interior, and even equipment was developed in differing stages where applicable. Although not entirely the desired product in the end, the INS Irmtrud Kistler ceremoniously launched on the first day of the year, January 1st, 2017, as the Imperial Navy's first domestically developed submarine in several decades; INS Irmtrud Kistler was quickly brought back to the dry dock after serving two months at sea so it could receive some of the upgrades that its sibling vessels would be equipped with during construction. Many components and fixes couldn't be included with the INS Irmtrud Kistler and even to this day the INS Irmtrud Kistler lacks similar features and other standard equipment it helped to hammer out during its development. Since launch, the Imperial Navy's order for Katzenhai class submarines is quietly being fulfilled in mass in order to fully succeed the LA-602 Kukri submarines in service with the Imperial Navy. Although it's difficult to estimate when the Katzenhai will entirely replace the Kukri, most Imperial Navy officials believe (with current funding) that the Imperial Navy will fully retire the Kukri by 2025 or 2030. The Secretary of the Imperial Navy (ADM Kaleb Fishman) as of March 2019 proposed an increase to the Imperial Navy's budget for "the expansion and upgrade to fleets, including the acceleration of submarine acquisition." His request was accepted and in the recently passed Armed Forces Budget included additional funding to the Imperial Navy estimated to speed up submarine acquisition by "months or even years" according to Imperial Navy officials.
Design
Katzenhai was designed to fulfill a role the Imperial Navy believed was vital to the protection of waterways in and around Imperial waters. According to most naval warfare experts, the greatest weapon against a submarine is another submarine. Thus the Imperial Navy required a submarine suitable for killing other submarines while also highly capable in other fields a submarine should be equipped for; this would include targeting surface and above surface threats for elimination, collecting as much valuable intelligence as possible through any means necessary, and performing strategic, often secretive, operations excluded from normal operating parameters. Katzenhai had to be the most quiet, well armed, and technologically advanced vessel possible in order to achieve the extensive expectations placed upon it. In the vast majority of the design, moderation was needed, however. In order to kill another submarine, you didn't need to have the largest hull, posses the most weapons, or even have the highest of endurance. Designing the Katzenhai to be economically mindful was as important as making it deadly and versatile a warship could be. Thus in the end, the Katzenhai was designed as the smallest submarine in Wolf Armaments' inventory, but in exchange for its size and endurance it obtained greater speed, stealth, and even didn't lose any modularity that all Wolf Armaments warships are known for.
Construction for a submarine is vitally important because it determines the submarine's maximum depth, its longevity in ocean conditions, and is the first line of defense against enemy detection tools. A weak hull means poor depth range, higher maintenance cost, and abysmal stealth. Thus when designing the hull of the Katzenhai, both the Imperial Navy and Wolf Armaments set upon achieving the following standards: (A) A hull made from affordable material, but did not compromise strength or safety requirements; (B) internal layout design that brought direct benefit to the Katzenhai's hull strength; and (C) exterior protection that provided both safety benefits and a considerable boost to the vessel's overall stealth performance. Of the many options presented to Wolf Armaments and the Imperial Navy's Naval Design Committee by materials manufacturers, HSLA-100 Steel was chosen after a lengthy bidding process. This steel alloy was chosen in particular after other alloys of the same variety were passed over and titanium was eliminated from the selection early on; although some titanium alloys met the requirements required by the Katzenhai Project, it was deemed too expensive per vessel to manufacture and when compared to other steel options, titanium was more difficult to handle during the sculpting/welding process. Such inconveniences risked production speed and would drive the cost of production higher if titanium was chosen - two consequences designers specifically wished to avoid.
Katzenhai's HSLA-100 Steel is characterized as having greater resistance to atmospheric corrosion than conventional carbon steels and having superior strength/toughness than other alloys within it the HSLA-100 Steel family. There is a complicated process to achieve these results and part of said process is the inclusion of copper. Steel alloy bearing Copper (Cu) is austenite (a solid solution of carbon in a nonmagnetic form of iron, stable at high temperatures, which is a constituent of some forms of steel) at nine hundred degrees Celsius and aged at six hundred and forty degrees Celsius. It is then held around eight hundred MPa while aged for one hour in six hundred and forty Celsius; appropriate toughness is reached around around eighty-five joules & negative seventy-five degrees Celsius. Copper as an addition is vital during this aging process because it retards the softening process that reduces the alloy's toughness. This process is entirely required to reduce the carbon count in the alloy. The less carbon there is the better, and if no carbon is left, all the better; this is because carbon reduces the toughness of the alloy and makes it more difficult to weld. Six hundred and forty degrees Celsius is crucial for the development of Cu clusters, where higher or lower temps produced lower yield clusters or formed mismatched rod-like shapes – six hundred and forty degrees is the best combination of strength and toughness (although alloys aged at four hundred and fifty to six hundred and fifty produce similar results). This temperature is also superior because the base temperature is around six hundred and thirty-five, allowing for better recrystallization and recovered dislocation density of Cu clusters. This lengthy process, when performed correctly, produces a superior HSLA-100 Steel alloy that results in superior toughness, strength, flexibility, and anti-corrosion properties.
The high performance of Katzenhai's hull is attributed to both the material(s) used and its overall careful design. The exterior is supported by spaced-out ribbing throughout the entirety of the vessel and further strengthened using compartmentalization. Three major compartment sections supported by heavy structural ribs separates the submarine into three major compartments: the bow (past the conning tower section), amidship (center of the vessel featuring the conning tower), and the stern (rear half of the vessel containing most propulsion systems); beyond these three major compartments are several smaller compartments and standard hull-sized ribbing that is located throughout the rest of the submarine. In order to counter magnetic anomaly detection (MAD) equipment, Katzenhai incorporates specialized deperming facilities to erase or even blend into operating theaters. Heavy gauge copper cables encircle the hull and sail, acting as a resetting tool once an ample amount of electrical current is pulsed through them. This has the effect of "resetting" the ship's magnetic signature, erasing the abnormalities that MAD equipment detect when spotting submarines. It is also possible to assign a specific signature that is best suited to particular areas of the world in which the submarine will operate. Over time the deperming affect will wear off, thus the procedure must be redone periodically to maintain the desired effect.
To further protect and improve the Katzenhai's hull, anechoic tiles (CTBN synthesized with a rubber-polymer epoxy resin) were added to the exterior hull using standard thirty kilogram, six hundred millimeter by three hundred millimeter by eighty-eight millimeter molded tile-blocks. These smooth rubber-like tiles posses sound and vibration dampening properties but are also used in order to protect the hull from small collisions; so while dampering sound/vibration energy, the tiles essentially act as rubber padded armor to protect the submarine from collisions. These tiles rely on a synthesized two-material substance that's rubbertoughened and possesses an epoxy material, thus allowing it to be energy absorbent and sound dampening. The higher-damping, lower-modulus component is a carboxy-terminated butadiene nitrile (CTBN) with a Tg (glass transition temperature) at or near the intended use temperature, and the lower-damping, higher-modulus component is an epoxy resin. It is well established that such a material dissipates vibrations more effectively at Tg than at higher or lower temperature but also tends to be relatively soft (to have low E or Elasticity) at Tg, thus said material can damper sound/vibrations but lacks the the elasticity to protect the hull or absorb acoustic energy. To note, the rate at which acoustic energy enters the material is proportional to E1/2. Hence, if a material instead has low elasticity, it may not absorb acoustic energy at a high enough rate to be considered an efficient damper, even at Tg. Thus the conclusion that one material tiles were an impossibility if they were to retain strong elasticity and have proper sound/vibration dampering. With that in mind, now came the inclusion of the polymer epoxy resin. The epoxy resin is a binding material used to effectively synthesize the CTBN and epoxy mixture (a part rubber, part dampening agent) into forming a single, adhesive lain, anechoic tile.
Step one of the synthesis of the material, the CTBN is mixed into an epoxy resin (a proportion of one part CTBN to ten parts of epoxy by weight) at a temperature of about one hundred and fifty degrees Celsius - although a lower temperature can be used if there is ample time available. Once the epoxy resin has become modified by reaction with the CTBN, it is cooled then mixed with the epoxy-curing agent. The curing reaction involves both cross-linking and gelling of the resin molecules. During the curing reaction, the CTBN component becomes segregated into a separate phase comprising of approximate spherical rubbery domains, between one and ten μm (micrometer) in diameter, and is dispersed throughout the epoxy resin. Because most of the volume of the material is occupied by the relatively high-modulus epoxy and the Tg of the rubbery domains occupying part of the volume is at or near the intended use temperature, the material can have the desired combination of sufficient stiffness and sufficient dampening. This process makes it possible to build tiles in molds that then can be applied onto the surface of the submarine (or any boat really). Smooth and rubbertough in consistency, tiles refrain from creating any surface drag and accurate pristine molds can create a clean/smooth surface-hull for submarines.
Contrary to the likeness movies offer audiences, the inside of modern submarine is narrow, dangerous, and even busier than depicted on film. Although decoratively floored with tile and steel, and walled with treated wood and steel, it would be wise to remember that the typical hallway inside the Katzenhai is about as wide as your foot is long. Entrances into the submarine include a primary top-hatch for sailors located rear of the sail, two cargo hatches for pallet sized supplies (used for quicker/easier resupplying), and the top-hatch located atop the sail used primarily for observation and equipment maintenance. Additional entrances include the torpedo tubes which are used for restocking torpedoes and submarine-launched cruise missiles, and the Underwater Submarine Modules (USM) which offer multiple uses for submarine crews. Starting from the bow of the ship is the torpedo room, the Underwater Submarine Modules, and the hull's frontal sonar sonar window (which will be covered later on). The torpedo room is home to the submarine's six torpedo tubes, the magazine rails which store additional torpedoes/cruise missiles, and the stations where crewman control the submarine's weapon systems. Of the exceptionally tight conditions, the torpedo room is considered especially cramped with even assigned crewman forced to bunk on eight bunks located next to their stored torpedoes/missile canisters (four per side of the hull). Work stations using multi-function consoles on hardpoints are located on each side of the room and control every action within the torpedo room; in case of damage or other emergency failures, each console can control the functions of every other console like it in the torpedo room. Next, the Underwater Submarine Modules or USM, is section of contained silo magazines adjacent to the torpedo room and command center. A narrow hallway splits the four modules in two with two modules per-side. Amidship contains two floors and hosts most of the crew work/living areas on the ship; this includes the command center, kitchen & mess hall, all eight bunk rooms, and the submarine's only storage room (for equipment/supplies lacking special storage space on the submarine). The command center controls all aspects of the submarine, including having both steering wheels for steering the ship, multi-function consoles for most ship-based operations, and communications consoles to manage related systems; similar to the torpedo room's multi-function consoles, the command center's multi-function consoles are located on hardpoints and can control other command center consoles in the event that one or more is damaged/suffers a failure. Katzenhai's mess hall and kitchen share the same space in the ship but are separated by a thin wall that's waist high in one section; this section is where the serving trays are located for sailors to retrieve their meals from. The exceptionally narrow kitchen includes a large freezer, three liquid storage tanks for soft drinks and water, and a walk-in fridge aside from the ship's standard cooking stations (flat-tops, stoves and stove-tops, etc.); although connected, the mess hall also doubles as an activity area where crew can relax in their free time when not eating meals. Mess hall activities include reading, board and card games, or using personal devices for non-internet activities (unable to retrieve such services deep underwater after all). Narrow and small, the mess hall has enough table space for over thirty people, enough to serve one of three crew shifts at a time. Finally, the bunk area includes eight rooms for bunks and the CO's Suite (a small room for the commanding officer's bunk). Three bunks per side of the room equals 6 bunks per room, thus eight rooms equal forty-eight bunks; although not enough to house every sailor/combat team comfortably, the number of hot-racks (bed spaces that are shared to save space) is considerably diminished compared to most modern submarines which often have an excess of forty sailors sharing hot-racking - the Katzenhai has thirty-two sailors hot-racking, technically. Since Katzenhai also has an additional eight bunks in the torpedo room, this means only twenty-four sailors need to hot-rack. Also, two toilets on either end of the bunk section for personal use are available when crew members need to do their business. Lastly, the stern section of the ship contains all propulsion, water management, and power systems. This section includes water flow management (including control over the ballast tanks), the nuclear reactor, emergency diesel engine, and other propulsion systems plus their control consoles. While the reactor powers the ship normally, the emergency diesel engine is used in the event the reactor fails so that the submarine may limp to safety; the engine can also be used to pump air out of sections of the submarine in order to plug or remove leaks that have compromised a section of the ship. The reactor itself is only operated on by select members of the crew and is protected behind a layer of walling designed to contain the section in the event a leak occurs.
Command, Control, Communications, and Sensors
Command, control, and communication are vital components for a submarine to operate effectively, but not in the way most people believe. Unlike the most glamorous of war films, being a submarine crewman is often times a lonely endeavor because communication with the outside world is a rarity while at operating depths. This is why submarine crews are typically taught strict discipline and trained to operate independently from even their highest of ranking commanders at home. Everyday command and control is conducted in the command center, a central facility to the submarine where command and control staff are posted. From here the staff, including the Captain, make key decisions, control the ship's every action, and where all gathered data is coalesced or disseminated. Stations include a parascope station (enough room to fully rotate), two pilot stations that are side-by-side, multi-function consoles for everyday operation (data collection and management devices, equipment controls, communications, navigation, etc.), and the STDS, or 'Smart Table Display System'. These consoles are located on hardpoints and can control other command center consoles in the event that one or more is damaged/suffers a failure. The STDS is a large multi-function display unit that displays a model of the ship, allies and other units near and at range, other ships including hostile contacts, and key mission/operational information; it is entirely interacted with using both controls and the screen itself depending on the user's choice (the entire surface is touch enabled). Such a device comes is useful for commanders looking to posses a better read on their operational situation and posses an easier flow in their command chain. Katzenhai uses high capacity digital communication switchboards, which interconnects voice and data communication channels providing a high level of international communications from room-to-room or an open conference line for ship-wide broadcasts; this ease of communication can be received via text, sound, video, or all the above, making international communications better if not improved. STDS and work consoles are linked with a redundant Ethernet system that interconnects them with the remaining consoles/devices located throughout the submarine - this connection then leads to the radio over fiber system that leads to the sensor suite located in the sail. Similarly, an intercom and landline system connects all rooms/compartments for fast and direct communication.
Communication aboard the Katzenhai, as noted, is primarily conducted through direct phone lines (often either by hand-held devices or wired headsets), an intercom system, and through digital means via consoles located in every workstation on the submarine. But communication with the outside world is a whole other ballpark. To communicate with the outside world, the Katzenhai has to be close to the surface or surfaced enough for an antenna to penetrate the water. Communication being defined as being able to reply back if spoken to. Katzenhai has two methods to conduct direct communications with the outside world: the traditional method of surfacing and extending its antenna (Katzenhai could also surface just enough for the antenna to poke above the wake, aka parascope depth), or use the Underwater Communications Reel, a one hundred and fifty meter tether line with an antenna buoy on the end, to reach the necessary depth required while the submarine remained in safer depths; said buoy could either rest just bellow the surface to receive communications or on the surface for to actually reply back. However, submarines will hardly reply to communications sent their way because the only way they can reply is by radio/electronically; emitting emissions (sending radio or satellite communications) is an easy way to be spotted by electronic warfare systems looking to track warships. So if/when the Katzenhai deemed it necessary or safe to emit, it can communicate via standard radio and satellite communications. Standard external communication packages include link 11, link 16, link 22, Joint Tactical Information Distribution System (JTIDS), and JSAT tactical data links, allowing full interoperability throughout the fleet the vessel is with as well as any allied forces in the area if radio communication is vital.
But as noted, submarines rarely take such risks by emitting traceable electromagnetic emissions. One mite ask how a modern submarine, such as the Katzenhai class, communicate if it can't emit/reply? The answer is one-way communication and procedures crew must follow. If the situation suddenly changes, requiring command at home to notify the locally patrolling Katzenhai to change mission for example, command has two options to make contact with the Katzenhai class: Very Low Frequency (VLF) or Extremely Low Frequency (ELF). Technically most well-equipped navies operate using both systems rather than just one if they can help it, but both will be explained anyways. Standard VLF communications operate at about ten kilohertz while nations operating submarine communications operate up to thirty kilohertz systems; at this energy level, the radio waves should be able to penetrate about twenty meters bellow seawater. To answer why a submarine wouldn't operate such a device itself to send replies is because the transmitter for such a device are kilometers long (often a few square kilometers wide in fact), thus a submarine like the Katzenhai is only capable of using a receiver to pickup VLF communications. Additionally, VLF has a low bandwith and even worse bit rate that's only capable of sending text at about four hundred and fifty words per minute - though some systems can transmit as much as seven hundred depending on power output bit-code used. Of course you'd have to be within twenty meters of the surface to receive this transmission (such as antenna or tether being at correct depth). So the next step in this equation is how would you know to be at the correct depth at the right time to receive the transmission? ELF, or extremely low frequency, is a much more powerful radio wave used to communicate with submarines at standard operating depths. Such transmitters can operate at about three hundred hertz and penetrate hundreds of meters of seawater, thus reaching submarines at their standard operating depths. The catch is that transmitters for ELF stations must be installed into areas with very low ground conductivity, have to be kilometers long (ranging from twenty to a hundred kilometers in length), and their bandwith/bit rate is far worse than VLF bandwith/bit rate; ELF messages are often either very short or are instructions to prepare for a VLF transmission at higher depths - messages use symbols/codes rather than actual text messages. Katzenhai, equipped with both VLF and ELF receivers, can receive both types of communications.
Regarding sensors, Katzenhai is equipped with two types of sensor packages: Above sea (sensors deployed above the sea's surface) and bellow sea (sensors used while fully submerged at operational depths). Sensor equipment for above sea use are mounted inside of the sail and extend upwards for maximum elevation when deployed, when they're not deployed they retract into the sail/hull of the ship. Thanks to the use of telescopic technology and optimally designed sail, the electronic's mounts inside the sail do not penetrate the pressure hull; all information, such as periscope video feed/control, is transmitted to a work console in the command center instead. These above sea electronics include the MultiSensor Observation Mast, and JSSN-S X-band (FMCW) LPI Navigation Radar, NET-S System (CESM/COMINT). To start with, Katzenhai's observation mast is a telescopic, twenty meter long periscope system equipped with a compact suite of observation equipment. Including standard high definition video, Katzenhai's MultiSensor Observation Mast includes an EO/FLIR (electro-optical night vision and thermal vision) camera and a High Repetition Rate InGaAs Laser Diode Pumped Rangefinder (for accurately ranging targets up to twenty-five kilometers away above sea). Next is the Joint Sub-Surface Navigation-System X-band (Frequency-Modulated Continuous-Wave, aka FMCW) Low Possibility Intercept Navigation Radar. Mounted on a non-penetrating mast, JSSN-S provides both active and passive radar detection modes; a third mode is used primarily for detecting/tracking weather patterns/cells and flocks of birds. Active setting utilizes low transmission power in order to make JSSN-S virtually undetectable while sending continuous waves with large bandwidth to cover large operational areas with minimum peak transmission power. The system also has frequency agility and utilizes solid-state technology to provide high range resolution and peak performance. Thus JSSN-S's active mode has an extremely low probability of interception, even against modern ESM systems, and strong durability against external interference. While on passive mode, JSSN-S instead pours its power output into detecting and tracking radar emissions generated by emitters on enemy warplanes and warships; rather than emit radar waves itself, JSSN-S can simply listen and track targets if they themselves are emitting radar energy, thus providing everything from enemy identification to ship data with higher detail than the submarine's C-ESM/COMINT equipment (thus leading to more accurate and quicker targeting solutions). In conclusion, JSSN-S can detect and track low radar cross section surface and above surface targets even in dense cluttered environments with incredibly low chances of its radar energy being intercepted, and being able to track over two hundred surface and above surface targets at a range of about forty-five kilometers away.
Next, the NET-Submarine System (NET-S), is the submarine designed variant of the NET-B system, which adapts the system for submarine use, including using similar work consoles but different sensor equipment mounted in the sail. Said system is found on the Barrakuda FS, among other warships designed by Wolf Armaments. Included in the package is Katzenhai's IFF system, which is a dual identification and interrogator device that is both a transponder and interrogator; this device works with an associated antenna and displays the vessel in multiple modes as its international identification credentials - this includes the ship's name, class type, nation of origin, and other source identification information. As an interrogator the IFF uses the vessel's radar to seek out transponder information on various modes that sea/aircraft use. Usually, if the transponder is switched on, the ship will see transponder data associated with the radar return - if the transponder is switched off, however, only the radar return information will be received if at all. Hostile ships or aircraft may turn off their transponders (not counting their military's) so that they will go unnoticed and will not be able to be tracked easily by long range and medium ranged radars, which is usually outside the ranges of most warships or airborne radars - or the vessel in question is jamming the radar signal using an electronic warfare device, skirting the identification and possibly the radar return. Of course this IFF system has different mode settings that allow the user(s) to only reply back to their military's interrogator systems, to both, or to none at all; until recently, such aircraft/warships operated civilian systems for the purpose of identification to civil traffic authorities, but Wolf Armament designed systems use a single multifunction system.
NET-S, named after fishing nets, is an upgraded and downsized model of the previously mentioned NET-B System, which is a Cryptologic Electronic Warfare Support Measures and Communications Intelligence (C-ESM & COMINT) device that serves as part of the Katzenhai's electronic warfare suite. C-ESM systems essentially listen and/or probe for all forms of electromagnetic energy, intercepting said transmissions for intelligence gathering; the 'C' in 'C-ESM', cryptologic, refers to the cataloging and analyzing of said collected data for use by the submarine and its allies. Additionally, NET-C also gathers COMINT (SIGINT), radar transferred signals, and other data intercepts which are recorded and analyzed by command center crewman. NET-C also utilizes this information to identify, catalog, and track contacts it discovers. Radio emissions, for example, can be traced to their direction and if detailed/observed enough, isolated to their exact location; once said source is put under observation, its other emissions (such as radar) are tracked and analyzed to the point that radio alone will provide the Katzenhai the source's identity/classification, its travel information (such as bearing and speed), and a rough estimation of its exact location at all times. In the ideal scenario, a Katzenhai submarine could detect, identify, and track an aircraft carrier at sea, providing its plethora of gathered data to allies, and can even begin isolating classification through multi-frequency emissions tracking - aka frequency hopping. NET-C utilizes a powerful yet sensitive sensor node (which is made up of multiple smaller pieces of equipment, including small antennas) mounted onto a mast coupled with three work consoles in the command center where crew perform their never ending mission of analyzing and cataloging collected data.
Finally, onto the sub-surface sensors, there is the Underwater Integrated Sonar System, the Under-Sea Sonar-Towed System Array, and the Planar Flank Array Sonar System. Starting off with the Underwater Integrated Sonar System (UISS), Katzenhai's primary active and passive sonar systems fall under the UISS. UISS consists of the bow mounted parabolic shaped active/passive (low frequency) sonar, the (high frequency) passive intercept sonar array atop the bow, and the mine avoidance/mapping sonar's conformal arrays located on/along the bow (includes the first set of sonar windows adjacent to the bow); the parabolic shaped active/passive (high frequency) sonar arrays located at the bow and stern sections of the sail; both planar flank arrays on each side of the submarine's hull; and the conformal sonar arrays found at the stern acting as a rear set of active/passive (low frequency) sonar arrays. The bow set of sonar arrays are tasked with the majority of the submarine's underwater detection, housing the most powerful of active on passive arrays on the vessel. Paired with the remaining arrays on the sail and stern, the Katzenhai possesses an extensively wide angle of coverage that allows the vessel to surveil targets no matter their position in regard to the Katzenhai. This also means that the Katzenhai need not rely on one array alone if the primary bow mounted systems suddenly failed due to unexpected reasons. But most importantly, having such excellent coverage allows the Katzenhai to take up position anywhere along targets it wishes to without encountering hindrances to target detection/tracking. The goal of all active/passive sonars on the Katzenhai is to detect, classify, and track targets that have been spotted. UISS is optimized in target discrimination, variable pulse types and waveforms, target tracking, and target analysis. Thanks to the Imperial Navy and other Wolf Armaments partners, Katzenhai's encyclopedia of sonar contacts is vastly more extensive than previous Imperial Navy submarines; our catalogue of warships, civilian ships, underwater drones, and other sound origins include thousands of ship designs, hundreds of aircraft, thousands of sea life, and all known submarine craft, including most commercially/military operated drones. Although partially omitted to future customers due to security reasons, Katzenhai's libraries of sonar contacts is largely unaltered and can always be upgraded/updated with customer libraries at any time. Such data is incredibly valuable to submarines because classifying sonar targets often means life or death situations, or mission important details required for optimal mission results.
Added benefit of such excellent coverage includes scanning abilities that can map out the world around the Katzenhai. Both sets of high frequency sonars (sail mounted and the standard mine avoidance arrays) are used to map the sea floor, surface features (such as ice), and underwater obstacles over a kilometer plus of the Katzenhai in high definition 3D picture. This is notably useful for mapping unknown waters and following known undersea routes, avoiding sea mines of various design, evading other undersea obstacles, and finding a location where ice is weakest on the surface in order to make a breach (which the Katzenhai can do but is warned to do so carefully as the rear fin is higher than the actual sail - operator's care is advised). Outside of the 3D interior view is the 2D mapping that maps up to ten or so kilometers, or referred to as the "local area." While not as detailed in picture form, scanning out to this range helps to spot targets of interest early on without using long range low frequency sonar (which low frequency is not used for in the first place) - especially anchored mines. In total, both sets of sonars can track dozens of targets, distinguishing what they are and warning crew of their presence long before they become a threat.
In order to ensure acoustic transparency for the Katzenhai's sonar systems, a carbon nanotube window is installed as a replacement for each hull-section a sonar system is found on the Katzenhai. Sonar windows are designed to be acoustically transparent, meaning acoustic energy can more freely travel through said material; the better acoustic energy can travel through a material, the greater the transmission essentially becomes. Reflection and attenuation cause acoustic energy to dampen, reducing said transmission and thus inhibiting sonars from properly functioning. The key to sonar windows, however, is utilizing a material that dampens/minimizes radiated energy without affecting sound transmissions - a task that requires specific materials and a special epoxy solution to produce desired results. Thus Wolf Armaments designed a sonar window that incorporates specially selected materials for peek performance, materials including Carboxyl-Terminated Acrylonitrile-Butadiene Rubber (CTBN), phenolic micro-balloons, glass fibers, nano-clay, and oxidized multi-wall carbon nanotubes (o-MWCNTs). The resulting mixture produces a composite material that has both increased the strength and reinforcement of Wolf Armaments' sonar window, and doing so without affecting the longitudinal wave speed of sonar.
To make use of the largely available flanks of the submarine, Wolf Armaments has installed a Planar Flank Array Sonar system. PFAS is a long range passive sonar system that utilizes smaller parabolic arrays installed on the exterior of the hull to capture acoustic energy around the submarine's maximum aperture (length x height). Each panel/array is only seventy millimeters thick and about twenty-eight meters long in total, although the modular design allows for as many panels as desired, thus reducing length. The entire system is easily maintained within its baffle, making the cost of operating the system for any navy nearly dirt cheap. PFAS has an exceptional performance record as a long range passive sonar system due to its adaptive beamforming technology; thanks to adaptive beamforming, PFAS easily rejects any signature produced by the submarine or the water flow noise it may create. This strong inherent focus allows PFAS to detect and classify signatures at extreme distances, even at peak operational speeds. Signatures are then tracked and annualized under PFAS' enhanced "Target Motion Analysis" software, which is capable of producing a signature's bearing solution, classification, and other important input data PFAS detects while actively tracking the signature. Although stand-alone in design, PFAS can also be integrated into existing sonar suites on submarines if so desired.
Katzenhai's final sonar system, the USS-1B TSA15, is a towed multi-function sonar array. Stored above the rear fins in a large bulb, it is released and gradually unspooled for a maximum length of twelve kilometers. The system is a collection of acoustic hydrophones towed behind the submarine on a cable several centimeters thick. Traditionally deployed several kilometers behind the vessel, towed arrays were designed to keep the hydrophones away from their own-ship's-noise sources, greatly improving its signal-to-noise ratio and effectiveness in detecting and tracking faint contacts - such as quiet, low noise-emitting submarine threats. A towed array offers superior resolution and range compared to hull mounted sonar that often has some level of interference to deal with. It also covers the baffles, the blind spot of hull mounted sonar. Katzenhai's towed array was designed specifically for submarines with the intention of making the towed array a key component for anti-submarine warfare and torpedo defense. Key features include depth control functions, improved hydrophones, upgraded countermeasure systems including decoy noise generation, and reduced equipment size.
Lastly, MEER links detection and countermeasure systems to each other, which allows Katzenhai's sensors, weapons, and countermeasures to engage incoming threats much faster at an automatic rate; this connection also allows weapons to be assigned targets according to perceived danger in order of most dangerous to targets that can wait, lets weapons and ship systems work together to protect the ship, and is capable of eliminating hostile targets above sea, on sea, or bellow the sea. For a submarine, however, MEER also acts as strategic tool that pools together all information gathering devices, crewen, and equipment for increased efficiency and world perception. This action process is completed using the submarine's many sensors that gather information, track the situation, and engages actions to solve problems. For example, a faint contact is detected in the distance and that contact's information is pooled together using existing catalogs and all gathered information; although your crew is shown a list of possible sources and ways to narrow down the culprit, the bearing plus background noise from the contact is enough for identification of this contact. Another example would be the detection of torpedo that is homing in on the submarine's area. MEER has already figured out where the threat is coming from, knows the type of torpedo it is, and is ready to make adjustments/fire countermeasures when given the prompt command to - or it could do some of those actions on its own. Most importantly, MEER better connects crew who even in the worst case scenario have to reduce their noise production while working quicker; digital interfaces and other hardwired linked communications equipment has evolved how the submarine operates on a day-to-day basis. The connection with the weapons systems also allows MEER to assist in taking out threats with high accuracy and lighting fast speeds more so than crew can in certain high stress situations.