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The Rhiannon-II-class Guided Missile Frigate is a design of a multi-role patrol frigate, incorporating capabilities against sub-surface, surface and air threats. They are constructed to act as the workhorse of a navy. In their secondary function, the Rhiannon-II-class Guided Missile Frigate is to serve as an escort vessel for larger units.

Rhiannon is the Goddess of Horses and Fertility in the Selkie-Pantheon. The name Rhiannon for a vessel has a long-standing tradition within the SDF-Navy, beginning with the first SDFS Rhiannon, a light cruiser in the 20s. Ships named Rhiannon have a place in the annals of Selkie-History, beginning long before the light cruiser

Design

The Rhiannon-II-class Guided Missile Frigate is a classical steel monohull design, 4,800 tons on normal load, 140.8 meters long, with a beam of 16.9 meters and with an average draught of 4.9 meters, enabling it to operate closer to shores then many compareable designs. However, the Rhiannon-II-class Guided Missile Frigate is not a brown-water vessel, but a green-water vessel, capable of operating close to shores and on open seas.

As many of SDY's newer designs, the Rhiannon-II-class Guided Missile Frigate was designed with stealth-measures in mind, but is not a fully dedicated stealth-vessel. This is mainly achieved by simple measures in the construction, inclined flanks, few vertical lines and very clean lines in general. This makes the Rhiannon-II-class Guided Missile Frigate appear on a radar to be around the size of a medium-sized fisherboat. The use of radar absorbing synthetic materials while building the superstructure adds to that effect.

Although radar is one of the most common ways of detecting surface combattants, it isn't by far the only way. The thermal signature is reduced by funneling the exhaust gases of the engines through a series of small pipes instead of one large stack, exiting the ship at a lower temperature to the vessels sides instead of directly above it like a large signal.

Speaking of the engines, this major provider of an acoustic signature is silenced by being settled on noise absorbers, mainly vibration absorbers, which absorb the engines' vibrations and nullify them.

The Rhiannon-II-class Guided Missile Frigate has a helipad, rated to handle VTOLs with vectored thrust as well, and a fully-equipped hangar for one medium-sized helicopter. The Rhiannon-II-class Guided Missile Frigate can carry a second helicopter on the pad.

Propulsion

The Rhiannon-II-class Guided Missile Frigate's power is provided by four diesel generators, each capable of providing 9,500 kW of power. Being a derivative of the engines used on the Faolchu-I-class FAC, these high-power engines consume less fuel at the same performance, powering all of the ship's systems, including the electrical engines driving the two propellers. This system, called Integrated Electrical Propulsion, or IEP for short, saves fuel and maintenance costs while freeing valueable space aboard the vessel. For enhanced maneuvreability and more economic energy consumption, the Rhiannon-II-class Guided Missile Frigate is equipped with controllable pitch propellers, which can be put into reverse pitch as well. As such, the vessel can reach a maximum speed of 32 knots and has a maximum range of 10,000 nautical miles at cruising speed.

Decoys

Centre of the decoy-suite is the Multi-Ammunition Softkill System, MASS for short. The system is connected to the radar and uses the data from these systems to launch radar decoys operating on the relevant wavelengths of the electromagnetic spectrum. This serves to confuse advanced, sensor-guided missiles. It can either be operated by a sailor or operate autonomously.

Additionally, the Rhiannon-II-class Guided Missile Frigate is equipped with a torpedo-decoy dispenser, namely a three-part system: A towed array, integrated into the VDS, for the detection and identification of torpedoes and their heading, a towed countermeasure, and two launchers for expendable decoys, one on port and one on starboard, which generate a more tempting acoustic signature, which in turn lure the torpedo away. This system is known as the Baoite Mark III.

Electronic Warfare

The Rhiannon-II-class Guided Missile Frigate is equipped with a large suite for electronic warfare, composed of a suite for Electronic Countermeasures, Electronic Protection and Electronic Support Measures.

Electronic Countermeasures, or ECM for short, are used to deceive and trick enemy means of detection and ultimately not having a guided missile slam into the ship's side. Be they sonar decoys or radar jammers (Rasberry Jammers is the system we usually use), active ECM measures confuse the enemy's sensors, while passive measures include for example the jamming of the guidance systems of enemy missiles.

Electronic Support Measures meanwhile detect, intercept, identify, locate, record and analyze sources of radiated electromagnetic energy (for example radar) for threat recognition and other purposes, amongst them intelligence information. With these information, a commander can make the tactical and, if necessary, strategic decisions needed. It also provides the means necessary to gather information about the Electronic Warfare Systems of the enemy either in order to avoid an attack or to attack more effectively.

With Electronic Protection (EP), or Electronic counter-countermeasures (ECCM), the vessel is hardened against every kind of electronic attack, for example against scrambling and jamming. This allows to attack the enemy even when he feels safe with his jammers in place and activated.

Sensors and Processing Systems

Rhiannon-II-class Guided Missile Frigate is fitted with an extensive sensor suite, core being two Nuacht N-13 Mark III Air/Surface Search Radars. These multifunction radars can also be used for weather forecasts, as navigation radars and for secondary fire control, but find their true calling in the detection and identification of threats on the surface and far above it, be they missile or aircraft or any type of ship. The data collected by the N-13 Radars is then transferred to the operations centre via the Type 900, where the crew can act based on this data.

Specialized in air search, the N-41 Mark III 3D Long Range Air Search Radar provides information about any given target, especially elevation, range and azimuth, while being capable of tracking 150 targets at once. It is a passive electronically scanned array radar. Besides its primary function as an air-defense and surveillance radar, the N-41 can also be used as a weather radar, but is not built for such a function and should be used in such a capacity only in emergencies.

The radar suite is completed by two N-38 Fire Control Radars, which are used to guide semi-active radar homing missiles, illuminating targets for the own missiles. As the guns aboard the Rhiannon-II-class Frigates possess their own fire control radars, the N38s are not needed in that function, but could theoretically be used in such a manner.

Additionally, the Rhiannon-II-class Guided Missile Frigate is equipped all around with infrared search and track sensors (or IRST Sensors for short), providing detection against everything emitting infrared radiation such as for example jet aircraft, helicopters or missiles, at a distance of up to 100 kilometres, depending on weather condition. This is especially useful in combatting stealth aircraft or in defending the own ship when the radar is not capable of operating due to jamming or similar measures. As the IRST is an array of passive sensors, it is hard to detect them operating.

For the detection of targets beneath the surface, and ultimately combatting them, the Rhiannon-II-class Guided Missile Frigate is equipped with a bow-mounted active sonar system and a Variable Depth Sonar, a Nuacht N-81 Mark II VDS. The latter system is capable of detecting submarines at a distance of up to 150 kilometres at an accuracy of less then 100 metres at maximum range, operating in very rough seas as a system for passive and active surveillance 360 degrees around the Rhiannon-II-class Guided Missile Frigate, analysis of any received signal (and keeping apart, if it is a whale or a submarine), audio output and a torpedo alert. Hanging at a single tow line, the Nuacht N-81 Mark II VDS can actively send out pulses while passively detecting sounds made underneath the surface as well in every direction.

The Rhiannon-II-class Frigate is equipped with a Type 900 Datalink and an Artio Battlescape Network.

Armament

The Rhiannon-II-class Guided Missile Frigate is armed with a weapon's suite for both offensive and defensive purposes, both against targets in the air, on the surface and beneath the waves, emphasizing the versatility of these Guided Missile Frigates.

Placed on the foredeck, the heaviest gun aboard the Rhiannon-II-class Guided Missile Frigate is the Túirín T-12 Mark II, a double-barrel 76mm gun, capable of acting as an auxillary AA-gun and CIWS, for shore bombardements and as a general deterrent against an enemy, which is less armed. Multiple kinds of ammunition, like fragmentation or HE-rounds, can be flung over a distance of 27.5 kilometers with this gun.

Solely defensive in nature are the two Ceantar C-84 Mark II 30mm CIWS, which aim with their own little radar, capable of operating fully autonomously against any incoming missile, be it aimed at the Rhiannon-II-class Guided Missile Frigate itself or at one of the vessels under her watch. They are placed on either side of the superstructure.

Main armament of the Rhiannon-II-class Guided Missile Frigate are its six Feadán Fe-12 Mark II 8-cell VLS-modules, capable of being loaded with basically every hot-launched missile, which fits into the 2.5x2.6x8 metre cell (we recommend reading the manual). The SDF-Navy plans to equip the Rhiannon-II-class Guided Missile Frigates with a combination of quad-packed Surface-to-Air Missiles, ASROC and AShMs, as well as a module free for mission-specific armament.

Core of the weapons suite optimized against submarines are the two triple packs of 533mm torpedo tubes, two Feadán Fe-32 Mark I on either side of the vessel, which, as the name suggests, are capable of launching 533 millimetre torpedos at any given target with compressed air. The Rhiannon-II-class Frigate is capable of carrying 18 torpedoes with her safely, six in the barrels and twelve on stock, and up to 24, but on the cost of ammunition for the 76mm gun.

Additionally, the Rhiannon-II-class Guided Missile Frigate has four balconies, positions on the superstructure designed for mounting heavy machine guns, autocannons like the SDY-Gabha SG-1 Mark III, remote weapons stations or serving as positions for riflemen and marksmen to operate from.

History

The Rhiannon-II-class Guided Missile Frigate began their life as the Rhiannon-IB-class Frigate, an upgrade to the already existing six Rhiannon-class Frigates of the SDF-Navy, in 2010. Soon, both the SDF-Navy and SDY realized, that the Rhiannon-I-class, despite being excellent vessels, was not really capable of handling major updates like the one the SDF-Navy had in mind without major yard stays or costs involved.

So, Rhiannon-IB died before it even lived and was replaced by an entirely new design, the Rhiannon-II-class. Originally planned as a Multi-Purpose Frigate, the Rhiannon-II-class Frigate slowly evolved into a Guided Missile Frigate, capable of acting as an active surface combattant as well as an escort for other vessels, who's main armament were its guided missiles.

The SDF-Navy showed great interest in these vessels, both due to the need to replace the Rhiannon-class Frigates, and due to the new threats faced by the SDF-Navy in the near future. As soon as the first design studies were finished, the SDF-Navy financed a first batch of six Rhiannon-II-class Frigates to be named after the Six of the Selkie-Pantheon (Rhiannon, Carman Fea, Abhcan, Gavida, Lodan Lir and Ladra) and to replace the frigates of the same names currently in service.

The first vessel, SDFS Rhiannon, was commissioned in 2017 during Silverport's Spring Festival, after, during the night before, the Envoy of Lodan Lir, Mona Beag of the Tribe of Louth, baptised and blessed the vessel.

Vessels

In service with the SDF-Navy

In foreign Services

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