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Astela class SSP (SA903)
Specifications:
Name: Astela
Developers: Fleet Naval Development Directorate (Arsenal Moldonei)
Builders: Imperial Naval Yards of Anemos Major
Operators: Imperial Fleet of Anemos Major et al
Built: 2010-
In commission: 2012-
Type: SSP - Attack Submarine (Diesel Air-Independent Power)
Displacement: 2,958t (surfaced) / 3,283t (submerged)
Length: 81m
Beam: 8.7m
Draught: 8.0m
Propulsion: 2x FA.50 V12 2,200hp (1.64MW) Diesel-Electric
10x TA.750/U 85kW Hydrogen-Oxygen PEM Fuel Cell
Potassium-Ion Battery Bank
Driving Single-Shafted Skewback Seven-Bladed Propeller
Speed: 12 kn (surfaced) / 20 kn (submerged)
Range: Up to 9,500nm at 8kn (est.)
4 weeks submerged
Complement: 42 men
Sensors:
Observation/Attack Optronic Mast (3CCD/FLIR, CO2 laser rangefinder)
Eletyr SDS.10 Acoustic Detection Suite (1x bow array (passive LF), 4x flank array (passive LMF), 1x towed array (passive/active LF), 1x intercept array, 1x mine detection array (active HF), 1x hydro-ranging array.
Eletyr OR.22 Navigation and Surface-Air Search Radar System
Electronic warfare and decoys:
ETAR Electronic Warfare Suite
6x 80mm acoustic countermeasure launcher tubes
Armament:
6x 533mm torpedo tubes
- 533mm Advanced Capability Torpedo
- SLTCM Anti Ship Cruise Missile
- SLAE Infra-Red Imaging Multipurpose Missile
- 533mm Model 10 Propelled Naval Mine
Overview
The Astela is a class of modern attack submarines developed to provide the Imperial Fleet of Anemos Major and associated navies with a modern force of submarines capable of engaging in effective, low-observability underwater warfare directed against enemy surface and sub-surface assets, supplementing and complementing the nuclear hunter/killer submarine fleets of these navies in open water duties as well as providing littoral operational capabilities. Developed by the Fleet Naval Development Directorate, otherwise known as Arsenal Moldonei, and produced cooperatively by a number of Anemonian shipbuilding concerns as a technological endeavour aimed at expanding the capabilities of the state's submarine fleets, the Astela is designed to stand at the forefront of modern conventional submarine technology and provide overwhelming technological superiority to its users in its intended fields of battle.
Initial testing was performed in 2009 utilising a pre-production testing hull constructed by Sailiei Fleet Production Yards, which would be passed subsequently to the Anemonian Amalgamated Special Operations Command for covert troop insertion, making full use of the vessel's long range transit capabilities. Constructed by the Imperial Naval Yards in Duchy Sailiei, the lead ship of the class in Anemonian service was launched in early 2010 and subsequently commissioned some two years later as the IFAM Astela (SM201-SA9031). Additional vessels were launched in quick succession, bringing a full twenty vessels into service with the Imperial Fleet and more with allied navies by May 2012. The total initial order placed by the Anemonian Armed Forces stands at a full 250 submarines with options for a total of 800 more, bringing the maximum potential initial order to 1050 vessels of the class within the IFAM alone.
Hull and Signature Reduction
The basic hull shape of the Astela follows the teardrop layout favoured on most modern submarines for effective hydrodynamic flow control and thus underwater performance, as well as maintaining a lower acoustic signature. This teardrop configuration is further enhanced by the use of a fillet construction on the submarine's sail; this helps to direct hydrodynamic flow around one of the submarine's primary sources of drag, and further decreases the vessel's acoustic signature by partly tapering the sail's progression into the main hull.
The Astela employs an X-rudder configuration. Compared to conventional vessels, this provides the submarine with an additional two control surfaces; this provides it with far greater potential mobility and allows it to operate in close proximity to the seabed, allowing for both operations in shallow waters and submerged operations at greater depths.
The hulls are primarily constructed of UHTSS (Ultra High Tensile Strength Steel). As submarines are designed to submerge to depths where the pressure exerted by the surrounding body of water exceeded the compressive strength of conventional steel alloys, the Astela's basic design was developed to ensure that it was capable of submerging to greater depths than equivalent submarines and increase its protection against shock based anti-submarine ordnance. UHTSS employs over 10 separate elements, including silicon, manganese, vanadium, chromium and titanium, some in 0.0001% total composition content, together with a relatively high carbon content to bring the tensile strength of the steel up to nearly 261,000psi (~1,800MPa). This incredibly high increase in hull material strength has been used to both increase hull strength and decrease the total volume taken up by the materials used, providing the Astela with a twofold advantage over other similar application vessels.
The displacement of the vessel is 2,958t surfaced and 3,283t submerged.
To decrease its observability and detectability across a number of spectra, the Astela employs a number of innovative signature reduction techniques. The first and foremost design objective in the Astela was to minimise acoustic detectability. This was achieved in a number of fashions. The hydrodynamic hull decreased drag and thus flow sound. The submarine's machinery was decoupled and dampened using sound-attenuating mountings to control both vibrations and noise emissions. Externally, the submarine utilises two primary sound-absorbing layers to greatly limit its acoustic signature, beyond levels achieved by legacy and current generation vessels. The first of these is a conventional spray-on anechoic coating composed primarily of viscoelastic urethane polymers. The anechoic tiles employed by the Astela, however, follow a highly unconventional layout. Instead of utilising the synthetic polymer and void tiles used by many modern submarines, the Astela relies upon an alternate tile composition. Taking advantage of the Mie solution properties of high density lead spheres, the Astela's unique anechoic tile composition utilises lattices of two-component CTBN/Epoxy dampening material-coated high density lead spheres organised to form phononic crystals (i.e. a synthetic acoustic metamaterial) in bi-layer slabs of coated spheres. Research has shown that phononic crystal anechoic slabs with optimal properties have the potential to absorb almost all the incident energy in desired frequency bands. In order to achieve this, an initial data set of ~750,000 potential differently structured coatings were provided to design teams. Utilising Markov-chain Monte Carlo sampling algorithm techniques to characterize and identify near-optimal property anechoic coatings, differential evolution algorithms were used to select an optimal coating from this narrowed data set. In addition to these methods, the innovative propulsion system and hull geometry used by the Astela also contribute greatly to the minimisation of its acoustic signature.
An additional area of concern is the vessel's electromagnetic signature. This is minimised through two primary methods. The first of these is a series of internally mounted (36 are used aboard Astela-class submarines) individually controlled coiled electromagnets generating counteracting electromagnetic fields in three perpendicular planes that ultimately provide a degaussing effect upon the ship while removing the need for heavy externally mounted cables that both add weight and acoustic signature to submerged vessels. However, a secondary cable-based degaussing option has nonetheless been developed for use by the Astela-class; this consists of a high temperature superconducting ceramic cable constructed from yttrium-barium copper-oxide (YBCO) installed around the circumference of the Astela's hull to provide external degaussing that takes full advantage of YBCO's greater electrical conductivity when compared to equivalent dimension copper wires (up to 150 times the electrical current) to minimise the degaussing cabling dimensions, both width and length-wise.
Finally, the Astela's design also considers the direct currents inherent to the hull and surrounding water. These direct currents can generate potentials which lead to the radiation of extremely low frequency electrical fields into the water from the submarine; this is prevented by short circuiting the direct currents, achieved by simply earthing the relevant components of the vessel.
Propulsion
Like many current generation submarines, the Astela utilises a diesel-AIP multiple powerplant with an electric transmission to provide the ship with surface dependent and independent powerplants for use in different environments.
The conventional powerplant used by the Astela consists of a pair of twin parallel turbocharged V12 marine diesels. The V12 engine layout provides a high level of power alongside perfect balancing and low vibration not found in equivalent displacement engines using a smaller number of cylinders; though maintenance costs are higher, the associated advantages are considered enough to warrant the engine's use. The parallel turbochargers serve to provide the engines with a higher power rating than that usually achievable by non-turbocharged engine of similar dimensions. Each engine provides 2,200hp (1.64MW) of energy. The engines are used to drive an electric propulsion motor feeding into a single shaft skewed seven blade propeller designed to minimise vibration and cavitation, as well as recharging the potassium-ion battery bank employed by the Astela (which provides significant efficiency and capacity gains over traditional lead acid batteries). This layout further serves to decrease the vessel's acoustic signature by decoupling the noise-producing diesel powerplants from the outer hull.
However, in lieu of the pure-diesel powerplants employed by many SSKs that previously limited the submerged duration of conventional submarines due to their diesel powerplants' reliance upon air from the surface, an important portion of the Astela's complete propulsion system consists of its highly capable and efficient fuel-cell based Air Independent Propulsion system. The heart of the AIP lies in the 10 80kW rated hydrogen-oxygen PEM fuel cells employed to provide the vessel with air independent power. The PEM fuel cell operates through the use of an electrically insulating polymer membrane; hydrogen gas is fed through one side of the fuel cell into the anode to separate the gas into its components protons and electrons. The protons travel directly through the membrane to the cathode. However, the electrically insulating qualities of the polymer drives the electrons through an external circuit towards the cathode, creating a current in the process. At the cathode, the electrons and protons react with oxygen to create water, which is subsequently disposed from the cell. Isomolded bipolar graphite plates backed by closed circuit PAO fluid are used to cool individual fuel cell modules.
The ten fuel cells are fed by a combination of hydrogen storage canisters and tank-stored climate controlled liquid oxygen. The ability to store fluid fuel sources within the submarine to power an energy source that produces water as its primary waste product provides the fuel-cell power plant employed by the Astela with the ability to operate independently of surface-provided air, increasing the low-speed submerged operating duration of the Astela to about 4 weeks. This long submerged operating time is achieved in a number of ways. The first is a relatively large H2 and O2 storage capacity which gives the vessel extended operating capabilities in itself. However, this storage capacity is augmented by a combination distillation/electrolysing system feeding into both the crew and power compartments, an innovative solution intended to provide the engine with additional fuel if so desired. This system acts as a form of indirect power conversion from diesel to API propulsion. Water is drawn directly from the ocean, removing the need for independent freshwater stocks. From there, it is passed through the vessel's distillation apparatus; this is performed to ensure the clean separation of water into its component hydrogen and oxygen, as opposed to the hydrogen and chlorine obtained through the electrolysis of brine (as well as providing crewmen and electronics cooling systems with fresh water). The desalinated water is then passed through a high pressure electrolysis unit drawing power from the battery banks, which separates the water into its component fluid hydrogen and oxygen; this can be passed into the crew compartment to replenish oxygen (in conjunction with soda lime scrubbers and mechanical air filtering to control the crew air environment), or into the fuel cell powerplant to continue replenishing the fuel supply of the air-independent propulsion unit.
Electronics and Sensors
The electronics suite employed by the Astela, a central component of the vessel's offensive and defensive capabilities, constitute a high performance electronics array standing at the forefront of modern military technology, designed to combine high performance capabilities with low observability characteristics in a fashion that maximises the utility of its components subsystems in the context of a diesel-electric attack submarine.
In lieu of the relatively obtrusive hull-penetrating periscopes employed by many submarines, the Astela is designed to use a non mechanical, NLOS viewing optronic mast employing digital visual data inputs to great reduce the area taken up by the visual sighting assembly within the vessel. Combining the traditional roles filled by both surveillance and attack periscopes, the optronic viewing array consists of a high definition 3CCD camera array capable of low light, black and white imaging, a forward looking infra-red sighting system and a pulsed eye-safe CO2 rangefinding laser, providing the commander with a comprehensive array of optronic navigation and targeting aids.
The Astela is equipped with a comprehensive sensor detection suite for surface and underwater operations. The vessel's fire control sonar suite consists of a passive cylindrical medium-frequency detection bow array, a passive flank array for low-to-medium frequency detection, a combined active/passive towed low-frequency array and intercept array. In addition to this, the Astela is equipped with a high frequency active sonar for mine detection and a long range hydro-ranging sonar for navigation purposes.
Astela utilises a combination of satellite, inertial and radar navigation when in conventional oceanic transit. Additionally, it possesses the capacity to employ coastal radio navigation for redundancy purposes and littoral operations.
For submarine radar surveillance and detection purposes, the Astela is equipped with a comprehensive modular threat detection and analysis suite. Providing radar interception across a wide frequency band, the fully automated electronic warfare suite is capable of threat analysis, classification, direction finding and display. With signals interception performed via a retractable sensor mast (also fitted with VH/UH frequency communications array, GPS interaction systems and ESM modules), radar signals are both displayed in a tactical context (utilising ranging and direction finding to locate sources) as well as analysing radar emissions in conjunction with stored data to identify threat types and intent (i.e. determining radar emission source nature, whether the signal is searching or tracking etc).
Acoustic threat detection and analysis is also provided. The Astela is equipped with four upwards-diagonally and two forward launching tubes loaded with powered acoustic decoy units. These units, equipped with active sonar arrays and pre-programmed paths of travel, act as acoustic decoys by both jamming enemy sonar arrays and mimicking the acoustic signature of the Astela. Enemy wire-guided torpedoes, directed from within vessels, are less susceptible to decoy units as the hostile crew are able to differentiate between decoy and main sub movement; in order to account for this, the forward launching tube decoys follow shallow turning paths similar to those taken by the submarine itself.
Drawing from the data provided by its acoustic and electronic detection and analysis suites, all of which feed into centralised combat systems, the Astela's fire control and combat management suite draws from a multitude of sensory inputs to provide its weapons systems with a comprehensive firing solution. The fire control software draws upon target analysis software developed from the many fire control systems developed for a range of aerial, ground and naval assets by corporations like Eletyr during the latter half of the 2010s; previous experience in producing such software gives the Astela's FCS the benefit of experience. Highly automated and able to collate data from a number of sources, it is capable of analysing detected targets, their projected location against projectile travel time, and provide the submarine with accurate targeting solutions within seconds for rapid responses to target detection.
Armament
The Astela-class SSP's armament suite consists of six 533mm torpedo tubes utilised to fire a number of ammunition types to perform a number of duties, providing the submarine with a highly effective and flexible selection of weapons. The loading system used by the torpedo tubes consists of a semi-automatic hydraulic loader cued by the weapons control officer, allowing individual ordnance types to be selected via the computer control system and loaded at higher speeds than manual loading schemes. The hydraulic loader is both decoupled and two-component CTBN/Epoxy-dampened to allow it to operate in low acoustic emission conditions, allowing it to be utilised while the submarine is running silently. Additionally, the reload system can be utilised manually if necessary, providing the vessel's armament with important mechanical redundancy. The tube employs a water-pressure based hydro-ram expulsion system to provide the benefits of ram expulsion with a low acoustic signature, though swim-out ordnance deployment can also be used.
The 533mm ACT (Advanced Capability Torpedo), developed for use aboard the Astela, is a weapon designed to complement the low observability and high performance of the vessel aboard which it is deployed. The torpedo is propelled by a hybrid turbine-electric propulsion system driving a single shaft propulsor; the propulsion system, compared to conventional alternatives, generates a much smaller acoustic signature that allows it to be launched and operated with a much lower possibility of detection by hostile targets. The sonar array employed is a broadband multi-beam passive/active capable seeker head, providing the weapon with both higher accuracy imaging when compared to legacy systems as well as the ability to be operated with a relatively low possibility of intercept and detection if so desired; together with the microprocessor housed in the weapon, the torpedo is capable of identifying and rejecting countermeasures and making autonomous decisions to some degree based on the data obtained via the FCS and its own sensor suite. Communications and guidance can be maintained by the submarine using fibre-optic cable guidance, though autonomous search, guidance and interception can be performed by the weapon; the warhead is composed of 300kg of polymer-bonded HNIW that can be pre-programmed to detonate upon contact or at a set proximity to the target.
As well as the 533mm ACT, Astela is provided with torpedo-tube launched folding fin anti-ship cruise missiles, short range multiple threat engagement missiles and inertially guided torpedo-mines for added mission flexibility.
Enquiries concerning exports and comments should be made via telegram or to the Anemonian State Arms Export Authority.