Ra Ji-yun-class missile boat

KY Ra Ji-yun as commissioned.
Class overview
Operators:	Menghe
Preceded by:	Meng Dae-wŏn-class missile boat
Built:	2004-present
In commission:	2017-present
General characteristics
Type:	Missile boat
Displacement:	290 tons full load
Length:	46.6 m
Beam:	14.3 m
Draught:	1.82 m
Propulsion:	2 Samsan S407 diesel engines (7,200 kW each) 2 pump-jet propulsors
Speed:	45 knots
Range:	550 nautical miles (1000 km)
Complement:	3 officers 13 enlisted crew
Electronic warfare & decoys:	1 × D-104 datalink
Armament:	2 × GBM-30/6 CIWS Modified Mk 41 VLS (16 cells)

The Ra Ji-yun-class is a class of advanced missile boat or light corvette in service with the Menghean Navy. They are built with a wave-piercing catamaran hull design and a highly stealthy superstructure, and can reach high speeds without being detected. They carry a heavy but versatile armament of sixteen self-defense-length Mark 41 VLS cells, which can be loaded with a combination of anti-ship missiles, land-attack missiles, and anti-tank missiles, allowing the ship to conduct stealthy strikes on land targets. Originally, as many as sixty-four units may have been planned, but actual production was cut to twenty-four.

Development

The Ra Ji-yun class missile boats, designed under the designation Plan 100, were developed as successors to the widely produced Meng Dae-wŏn-class missile boats. In all areas, they were designed as improved successors to the Meng Dae-wŏn class, with greater stealth, greater speed, and a more versatile range of armament options. Gun armament was downgraded from a 76mm turret to two 30mm rotary cannons in order to save weight, and because the Ra Ji-yun class was designed to rely more heavily on stealth than armed defense, avoiding enemy surface units rather than pursuing and engaging them. Due to this lighter gun armament, and due to their smaller size, the Menghean Navy classifies the Ra Ji-yun class as "missile boats" (KY-type) rather than "large missile boats" (KYD-type).

Design

Construction

The most distinctive feature of the Ra Ji-yun class missile boats is their pyramid-shaped construction, with the upper hull blending neatly into the superstructure at 60-degree angles all around. This planform alignment concentrates radar reflections in a specific direction rather than diffusing them toward radar receivers, reducing the probability of detection from most likely directions. Hatches, including missile launch hatches, are also flush with the surrounding surfaces, and the design has very few right angles. According to different sources, the ship is either coated in radar-absorbent cladding or built from radar-absorbent materials.

Missiles

The main armament of the Ra Ji-yun class ships consists of sixteen self-defense-length vertical launch cells. These were specially developed during the design process, and are not technically part of the standard Mark 41 family, though they are capable of using Mark 41 self-defense-length canisters. While standard Mark 41 VLS modules vent missile exhaust through a top hatch, the VLS modules on the Ra Ji-yun class vent missile exhaust directly out the bottom of the launch canister into the space between the catamaran hulls. This allows for a lighter and more compact design. The upper hatches of the missile launch cells were also redesigned to sit flush with the upper deck.

For anti-shipping missions, these cells can be loaded with the vertically launched variant of the YDH-26 anti-ship missile, matching the sixteen-missile armament of the Meng Dae-wŏn class. Because the standard self-defense cells are compatible with other missile loads, however, the Ra Ji-yun class can also carry other missile types, including SY-26 cruise missiles, YGJ-82 anti-tank or anti-boat missiles, and TY-100 short-range ballistic missiles. All of these options allow the Ra Ji-yun class to stealthily approach enemy coastal areas and launch precision strikes on land targets.

Gun armament

Gun armament is limited to two GBM-30/6 close-in weapon systems. Both are aimed by a combined radar and electro-optical fire-control unit on the superstructure. Compared with the baseline GBM-30/6, these models of the turret have more compact below-deck equipment and a radar-absorbent fiberglass turret cover shaped to match the 60-degree angles on the hull. Like the baseline GBM-30/6, they can also be used to target surface ships, but are less effective than the 76mm gun used on the Meng Dae-wŏn class.

Aft modular section

The large quarterdeck on the Ra Ji-yun class missile boats has recessed mounting points under flush panels. According to advertisements displays at arms expos, these can be used to fit mine rails or 20-foot container modules, as well as a fiberglass or other radar-absorbent cover that shields this added equipment from the elements and preserves stealth. Menghean ships have rarely been seen in this configuration, as minelaying, mine clearance, and modular ASW duties mainly fall to the Muran-class corvettes.

Propulsion

The ships' powerplant consists of two CODAD units. These compact diesel engines consist of two seven-bank multi-row radial diesel engines with 56 cylinders per side, coupled to a common transmission. They are believed to be derived from the Zvezda M503 engines on Menghe's Plan 261 missile boats. The drive shafts power two waterjets, one at the rear of each catamaran hull. At full power, the ships can reportedly reach speeds of over 50 knots in calm seas, and speeds of over 30 knots in sea state 5.

To further maintain stealth, the diesel engine exhausts vent into the space between the hulls, masking the exhaust's immediate infrared signature and diffusing heat over a hidden part of the hull.

Evaluation

Initially, the Menghean Navy was very impressed with the Ra Ji-yun design, and planned to build a large number of these craft to replace the remaining Plan 261 missile boats. This changed fllowing an assessment of the Innominadan Crisis, and especially Operation Mist Lake, the Menghean Navy's opening offensive which aimed to incapacitate Innominada's Eastern Fleet. Evaluation of this operation revealed three key conclusions with regard to fast attack craft:

1. Innominadan fast attack craft were extremely vulnerable to air attack, as they lacked any means of defending themselves.
2. Menghean multirole aircraft were extremely effective at delivering anti-ship missiles in short-range sorties, the traditional role of FACs.
3. Even high-speed Meng Dae-wŏn class FACs were too slow to be decisive; by the time they arrived in range of a target area, most of their targets had been destroyed by long-range missiles or multirole aircraft.

Based on these conclusions, the Navy decided to reduce its orders for new fast attack craft, directing the same funds toward procurement of more land-based multirole squadrons. Production of new Ra Ji-yun class craft would still continue, but at a reduced rate, and some existing Meng Dae-wŏn class craft would be removed from Menghean service and exported.