Insŏng-class destroyer

Side, fore, and aft views of HJ-384 Insŏng as built.
Class overview
Name:	Insŏng class
Builders:	Gyŏngsan Songsu-do Shipyard Chŏndu New Naval Facility
Operators:	Menghe
Preceded by:	Haeju-class destroyer
Built:	2015-present
In service:	2020-present
Planned:	16
Building:	5
Cancelled:	3
Active:	7
Laid up:	1
General characteristics Insŏng, as built
Type:	Guided missile destroyer
Displacement:	13,930 tonnes full load
Length:	178.6 m overall 165.6 m waterline
Beam:	20.5 m o/a 19.5 m w/l
Draught:	7.32 m to keel, full load
Propulsion:	COGLAG 2 × LM2500+G4 gas turbine generator, 33,600 kWe each 2 × LM2500+G4 gas turbine engine, 35,000 kW each 4 × Samsan 6EY26LW diesel generator, 2,300 kWe each 1 × Samsan 6NY16L-EW diesel generator, 400 kWe 2 × Samsan S2328N electric motor, 32,000 kW each
Speed:	36 knots
Range:	7,500 nm (14,000 km) at 20 knots
Boats & landing craft carried:	2 × RHIB
Complement:	36 officers 274 crew
Sensors and processing systems:	4 × AN/SPY-6(V)4 phased array 4 × S-band surface search radar 1 × Thales NS50 radar 3 × Dyura-D illumination radar 4 × Haegi PKHK9082 LPI navigation radar 2 × Hongmoja electro-optical sensor 1 × Nun-14 electro-optical sensor 1 × low-frequency hull-mounted sonar 1 × Ŭ-100D variable-depth sonar 1 × AN/SQR-19 towed array sonar
Electronic warfare & decoys:	4 × Metturi ESM/ECM suite 4 × Chasip ESM/ECM suite 4 × Baram-2 chaff/smoke launcher 2 × Manhwagyŏng-H 2 × Type 120 datalink
Armament:	1 × HP-76/1Y 76mm gun Mark 41 Vertical Launching System (128 cells) 1 × GBM-35/2 2 × 2 350mm tube for YŎ-35/2 torpedo 4 × GCh-96 machine gun
Aircraft carried:	2 × GH-36N compound helicopter
Aviation facilities:	hangar landing area with hauldown device

The Insŏng-class destroyers are the newest class of large guided-missile destroyer built in Menghe. They are large, multi-mission warships designed to provide long-range area air defense for Menghean carrier battle groups and anti-submarine task groups. For this purpose, they sport a powerful radar and electronic warfare suite and a large magazine of surface-to-air missiles, including the long-range YDG-67. They also possess substantial anti-submarine warfare capabilities, and a high level of stealth, quieting, and infrared signature reduction.

The Menghean Navy categorizes the Insŏng-class vessels as "main-force escort ships" (juryŏk howiham), the same type as the preceding Haeju-class destroyers and Pyŏng'an-class destroyers. This role indicates that, in addition to serving as multi-role escorts for a large task force, they also possess the ability to serve as flagships for a small surface squadron. Official Anglian-language literature produced by the Menghean government describes them as destroyers or guided-missile destroyers. Due to their size and displacement, as well as the fact that they carry substantial onboard command facilities, some countries instead regard them as cruisers, and in any case they represent a substantial advance in capability over preceding classes.

Development

MoND requirement

The Menghean Ministry of National Defense formally issued a design requirement for a new class of guided missile destroyer in 2010, though independent design work on next-generation DDGs had already been ongoing for several years by that point. Though satisfied with the overall quality of the Haeju class, the MoND was interested in a larger surface combatant which could more effectively protect a wider area. Central to this design would be a new type of active electronically scanned array, superior in range and tracking capability to the PESA AN/SPY-1 of the Haeju class. A new design would also offer an opportunity for a wide range of more incremental improvements, such as improvements to electromagnetic and acoustic signature reduction.

The initial MoND design requirement included mid-range ballistic missile defense as one of the desired missions of the future destroyer class. From patrol boxes in the South Menghe Sea, this would allow them to intercept intermediate-range ballistic missiles fired from Khalistan or Maracaibo, as well as medium-range ballistic missiles fired from Innominada. This role declined in importance after the EIA assessed in 2012 that no major EC member states had ongoing IRBM development projects, and the Innominadan Crisis of late 2014 removed the possibility of Menghean DDGs intercepting MRBMs from off the coast of Innominada. As such, the final iteration of the design entirely omitted BMD capability, though a future upgrade could make these ships BMD-capable.

Plan 1242 and 1244

4-view of Plan 1242, the first proposal for the Insŏng-class destroyer project.

4-view of the Plan 1244 design in its final iteration.

The first design draft for the new guided missile destroyer project, designated Plan 1242, was a "maximum" design which aimed to satisfy all requirements with minimal regard for cost or size. It would have displaced roughly 15,000 tonnes at full load, and would have carried the 37-RMA SPY-6(V)1 phased array radar in a four-face arrangement. A scale model of Plan 1242 was unveiled at a military press event in 2012, and several computer-generated models circulated on the internet in the years to follow.

In addition to Plan 1242, the Navy also requested medium-size and minimum-size entries for comparison. The medium-size slot was filled by the 13,800-ton Plan 1244, which incorporated most of the same core features as Plan 1242, but tried to fit them on a smaller hull by omitting features not essential to the mission requirements. The differences between Plan 1242 and Plan 1244 included the following:

• The 130mm main gun was replaced by a single 76mm gun atop a deckhouse.
• The two single 76mm guns forward of the bridge were replaced by countermeasure launchers.
• The 37-RMA SPY-6(V)1 arrays were reduced to 24-module SPY-6(V)4 arrays, resulting in a smaller and narrower upper superstructure.
• Both 64-cell Mk41 VLS groups were rotated 90 degrees, and the crew spaces alongside them were reconfigured.
• The underwater hullform was made finer, which also increased stability.
• The aft 23mm CIWs was replaced by a twin 35mm CIWS using the DGP-35-2 anti-air gun.

The reduction of the gun armament was a particularly contentious move, and the Menghean Navy justified it on the following rationale:

• A ship as large and expensive as Plan 1242 should not put itself at risk by closing to shore bombardment range against a parity opponent.
• The new guided missile destroyers would mostly be assigned to escort carrier battle groups and anti-submarine patrol groups, which, within Menghe's geostrategic environment, would mostly operate in the open ocean against other sea forces, giving the destroyers few opportunities to directly support land operations.
• In addition to the legacy Haeju-class destroyers, the Chunchŏn-class frigates and Saebyŏk-class corvettes also carried 130mm guns, allowing them to undertake naval gun fire support missions instead.
• The forward 76mm gun is able to double as a close-in weapon system firing guided ammunition, removing the need for a second CIWS mount forward.
• The use of smaller ammunition, and the reduction in the number of stored rounds, both reduced the necessary internal volume for magazines and ammunition handling gear.

The smaller radar array space was particularly important in reducing the amount of mass high above the waterline. Though the number of RMA modules on each face reduced from 37 to 24, Dayashinese engineers promised that the 24-module array would still be able to detect and track a Rafale-sized target at cruise altitude out to the radar horizon, with the main reduction in capability affecting ballistic missile tracking capability at extreme ranges and altitudes. With the MoND already rolling back the BMD requirement for these ships, the design team regarded these tradeoffs as acceptable.

Radar procurement

As early as 2012, Menghean naval designers began regular information exchanges with Dayashina, which was then beginning early work on the AN/SPY-6 radar family. Though still in development, the AN/SPY-6 was forecast to reach operational status by 2020, which was also the deadline for the commissioning of the first new destroyer. Menghe ultimately did not contribute to the AN/SPY-6's development, but it did secure a guarantee that Dayashina would make the AN/SPY-6 available for export to Menghe simultaneous with its availability to the Dayashinese Navy, along with information on the projected dimensions and power requirements of the antenna arrays and their supporting systems.

Simultaneously, Samsan Defense began work on a long-range AESA radar which would serve as a domestic competitor. While Dayashina had opted for the E/F band as a compromise, the Menghean Navy favored a D-band AESA for long-range search, as this would improve sensitivity against reduced-RCS fighter-sized targets like the Sieuxerrian Rafale. An I-band sector search and illumination radar would then convert these low-resolution D-band tracks into more precise tracks and provide missile guidance. In 2013, this program received the internal Samsan designation HR-2000.

The HR-2000 program had a promising start, but as development progressed it ran into a number of serious delays and barriers, especially surrounding the high-end electronics in the antenna elements. As late as early 2015, Samsan had yet to produce a working full-scale prototype array, and it was becoming clear that the HR-2000 would not be ready for delivery to shipyards by 2018. Rather than postpone orders and gamble on future breakthroughs, the MoND awarded Raytheon the contract for the SPY-6 units on the Plan 1244 destroyers in March 2015, and in June of that year, the keel segment for HJ-384 was laid at the Gyŏngsan Naval Yard with plans for a final design incorporating the SPY-6(V)4. The HR-2000 program was cancelled entirely the following year, though Samsan continued independent work on large L-band phased array radars.

Early construction

A mock-up of the Plan 1244 superstructure was first spotted at a coastal missile testing range in Ryangnam Province in 2014. This structure was likely used to test the new ship's electronics equipment, as final test work was still underway. Official state media at first suggested that the mock superstructure was intended for the Onju-class destroyer group, but based on clear differences in the superstructure and estimated measurements of the ship's size, independent analysts quickly concluded that it was part of a new class. This information was officially confirmed in May 2015.

The location of the test site stirred a great deal of discussion. The Menghean Navy had built test sites on land for decades, but usually in the blocked-off zone of the North Donghae Missile Range or at secret test areas in the northwest. The new test site, by contrast, was not only a short distance from Altagracia, but also clearly visible from the G76 expressway leading to the Juman Container Terminal and from civilian shipping lanes in Hwangsa Bay. Ostensibly, the Hwangsa Bay location was chosen to test the surface search radar's performance in an environment cluttered with civilian surface targets, but its proximity to Altagracia may have been a signal of strength to the Entente Cordiale states.

In 2017, the hull mockup fired surface-to-air missiles at a target drone over Hwangsa Bay, confirming that it was equipped not only with a full sensor suite but also with a fully operational vertical launch system. This suggested a further rationale for the chosen location: it allows the test site to provide air defense for Sunju, Tongju, Juman, and Dongchŏn, and guide long-range surface-to-air missiles into Altagracian airspace.

Design

Structure and survivability

Full internal deck plan of an Insŏng-class destroyer.

The Insŏng-class destroyers are the first Menghean surface combatant class (i.e., excluding carriers, auxiliaries, and the hybrid Hasŏ-class cruisers) to surpass 10,000 tonnes displacement at full load, and their size alone made them a substantial source of national pride when they were introduced. As built, HJ-384 Insŏng had a full-load displacement of 13,930 metric tonnes, making her one of the largest destroyer classes in the world.

For the structure of these ships, the Menghean Navy opted for an all-steel construction, rather than using lighter and potentially stealthier composites. The primary consideration was cost: Menghe's military shipbuilding sector is more experienced working with steel, and introducing other materials could have delayed construction or harmed implementation. Steel construction also resulted in somewhat greater durability and damage resistance, especially when compared to aluminium, which is more prone to cracking under strain and which can disintegrate catastrophically in a large fire. Navy engineers also worried that more exotic composites, particularly untested ones, might degrade under prolonged exposure to the elements, and regarded steel as a lower-risk option for an already major ship project.

Many other design choices around the hull are intended to bolster survivability. Almost all of the decks and compartments below the waterline incorporate some form of double hull, with either void spaces or fuel tanks between the outer steel plating and the internal compartments. For the steel thicknesses used, this provides negligible protection against direct shell, missile, and torpedo impacts, but it does limit flooding from shrapnel damage and minor collisions.

Nine watertight bulkheads separate the ship's hull into ten major sections, with some of these bulkheads extending as much as two decks above the waterline. These major bulkheads consist of two steel plates separated by a half-meter gap, which consists of void space lined with Kevlar. In the event of a shell or missile impact, these bulkheads can protect the adjacent hull sections against spalling and shrapnel, and help damage control teams limit fire to one particular area. The bulkheads are also fully watertight at least up to one deck above the waterline, and can limit flooding from a nearby mine or torpedo detonation to the breached hull section. In addition to these major bulkheads, most of the individual doors and hatches throughout the ship can be firmly sealed to contain fire or flooding.

The configuration of the ship's propulsion system is also intended to increase survivability. The main machinery components are split across four compartments, reducing the likelihood that any single impact could completely immobilize the ship. The sprinting gas turbines are in the aft hull below the waterline, a fairly conventional location, but the main gas turbine generators are located one deck above the waterline, embedded in the superstructure under the forward funnel. This fully isolates them from flooding damage, and also reduces their acoustic signature. Directly beneath them are the main direct-drive electrical engines and two of the diesel generators. These paired propulsion units are located at the very sides of the hull, but they are separated by centerline compartments which can be sealed off, potentially limiting damage to one side of the ship. The aft diesel generators are under the aft half of the helicopter hangar, and are slightly above the waterline, which also isolates them from flooding and noise. In the event of catastrophic damage to all four amidships compartments, the aft diesel generators can still power the maneuvering thruster forward, allowing the ship to limp to safety at a speed of 6 knots. This capability proved vital in the recovery of HJ-388 Chilsan.

All major ammunition magazines, including the magazine for helicopter armament, are stored below the waterline, reducing the risk of secondary explosions from missile impacts. The aft bomb and torpedo magazine is connected to the hangar by a single ammunition elevator with blast doors at both ends, an innovation introduced on the Chunchŏn-class frigates. The only exceptions are small arms and ammunition lockers throughout the ship; 35mm shells in the aft CIWS mount; the ready ammunition carousel of the 76mm gun; and the two VLS missile farms, all of which are entirely above the waterline.

Sensors

The Insŏng-class destroyers are among the first operational warships to carry the AN/SPY-6 air search radar system, alongside the Dayashinese destroyer Maya. Specifically, they use the AN/SPY-6(V)4 variant, with four faces each comprised of 24 antenna modules in an octagonal array roughly 3.8 meters across. This radar uses gallium nitride (GaN) transmitters with greater output and state-of-the-art computers with greater processing power, resulting in a reported thirtyfold increase in sensitivity over the already capable AN/SPY-1D. The radar's exact parameters remain classified, but official Menghean Navy sources report that it is capable of detecting and tracking a Dassault Rafale out to its maximum cruising altitude limited only by the radar horizon, implying a range of perhaps 500 kilometers against a reduced-RCS fighter-sized target.

Because the AN/SPY-6 uses AESA technology, with nimbler beamforming capabilities, it can also augment its effectiveness by increasing its dwell time on small targets or distributing search time according to a set program. Furthermore, the AN/SPY-6 can divert some or all of its output to electronic warfare, either jamming I-band radar within a wide area or focusing a narrow beam of high-powered jamming energy at a particular target.

As designed in Dayashina, the AN/SPY-6(V)4 does possess the ability to detect and track ballistic missiles, though it is less sensitive than the 37-RMA AN/SPY-6(V)1 or the proposed 69-RMA maximum variant. The Menghean Navy cut ballistic missile defense from the Insŏng-class destroyers during the switch from Plan 1242 to Plan 1244, but the ships' onboard hardware and software are likely still capable of detecting and tracking intermediate-range ballistic missiles, even if the ships currently lack anti-ballistic missiles capable of intercepting them.

In addition to the high-power phased arrays, there is a Thales NS50 radome mounted high atop the main sensor mast. This radar spins at 15 or 60 RPM, though its AESA construction also allows it to dwell on possible contacts in the course of each spin to generate confirmed target tracks. It has a range of only 180 kilometers, inferior to the AN/SPY-6, but it is mounted a full 37 meters above the waterline, allowing it to detect sea-skimming missiles at ranges in excess of 30 kilometers. The AN/SPY-6 arrays have a radar horizon of about 20-25 kilometers against a sea-skimming target. The NS50 also operates in the I/J band, as opposed to the E/F band, complementing the main search radar.

Above the four AN/SPY-6 panels are four long phased array antennas. These are reportedly optimized for surface search. There is some speculation that they may be designed to exploit atmospheric duct effects in the active and passive mode to detect surface ships well beyond the normal radar horizon, much like the HR-280 carried by older Menghean warships. As of 2022, this has not been confirmed, and some sources report that these antennas may instead be long-range IFF interrogator antennas supporting the AN/SPY-6 system.

In the infrared band, the Insŏngs carry two Hongmoja electro-optical scanners, which rotate at 10 or 30 RPM. Each unit contains two cameras which can be set to different elevations. From 32 meters above the waterline, they can detect a sea-skimming target at roughly 25 kilometers and a small surface target at roughly 20, detecting incoming missiles even when the ship is operating under radio silence. The exact sensitivity of the Hongmoja system is classified, and given the characteristics of infrared sensors, it likely varies greatly depending on atmospheric conditions, but under ideal conditions the Hongmoja scanner is reportedly able to detect high-altitude fighter aircraft at short to medium ranges.

The anti-submarine sensor suite is modeled after the suite carried by the Hasŏ-class cruisers, with a Ŭ-100D variable-depth sonar and a Ŭ-109 towed array cable. These systems can be used independently or in combination, and the Ŭ-100D has both active and passive modes. The hull sonar is a large low-frequency active-passive spherical array, but it lacks the extended side-scan panels of the Hasŏ class. This gives the Insŏngs very capable submarine detection capabilities.

Electronic warfare and countermeasures

In addition to the secondary jamming function of the search radar, these ships carry two other electronic warfare systems. The first is the Chasip electronic warfare suite, which is made up of two passive ESM arrays and one active ECM array. Little public knowledge about this system is available, and it only appears on the Insŏng-class destroyers. Some analysts speculate that it may be optimized for matching lower-frequency radar bands, allowing it to jam certain airborne early warning platforms more effectively. Other sources believe it may instead be intended for jamming communications. The square Chasip antennas are located on the front, rear, and sides of the superstructure pyramid, in stacks of three.

The Metturi electronic warfare suite, on the upper mast, works in the E/F and I bands, and is primarily meant to defend against anti-ship missiles. In automatic mode, it autonomously identifies the emissions of missile seekers, categorizes them by type based on their emissions and other sensor input, and blinds them with a directed radio beam in the same wavelength and frequency, without the need for crew input. Because the Metturi system is high up on the ship's superstructure, missiles with home-on-jam capability may be seduced into overshooting the hull and superstructure, or would at least strike the upper sensor mast.

Four Bakjŏlgi countermeasure launchers, part of the Baram-2 family, are distributed around the superstructure to provide a final line of defense against anti-ship missiles. Each launcher consists of twelve 135mm tubes in a low-RCS composite shell shaped like a truncated pyramid. When deployed, these can fire chaff and smoke screens, infrared flares, and parachuting active radar jammers, which can further seduce home-on-jam missiles. THe number of external stowage bins suggests that at least 144 reload projectiles can be stored in ready lockers, not counting the 48 projectiles in the launchers themselves and any additional projectiles stored within the hull.

The ships also carry four Ori decoy launchers, which are located behind doors slightly forward of the aft VLS array. The Ori system fires a fast-inflating buoy with radar reflectors and heat emitters, which can seduce incoming anti-ship missiles or create a temporary false target for enemy surveillance radar. In addition to the four ready decoys, 16 reload canisters are stored within the hull near the launchers. The launch tubes themselves are locked in position to fire, but pivot 45 degrees away from the adjacent bulkhead to allow easier reloading.

The two Manhwagyŏng-H launchers are located on either side of the forward funnel, just above the RHIB bays. Each one can fire twelve active sonar jammers, which can seduce incoming torpedoes by creating an array of false targets and blocking out the noise from the ship's own engines. The Manhwagyŏng countermeasure is also reported to be effective against wake-following torpedoes which rely on active sonar.

Armament

The primary armament of the Insŏng-class destroyer is its Mark 41 Vertical Launching System, with 64 cells forward of the bridge and 64 cells between the two funnels. All cells are strike-length. A state news report in 2020 listed the following "typical loadout," though actual loadouts may vary based on the mission in question:

• 64 × YDG-67 long-range surface-to-air missile
• 64 × YDG-64 medium-range surface-to-air missile (16 cells, quadpacked)
• 32 × YDG-66 short-range surface-to-air missile (8 cells, quadpacked)
• 12 × HŎ-3 Ryongorŭm anti-submarine rocket
• 12 × YDH-28 long-range anti-ship missile
• 10 × SY-28 land-attack cruise missile

The HP-76/1Y gun turret (top) used by the Insŏng class.

Gun armament consists of a single HP-76/1Y turret mounted on a deckhouse forward. The deckhouse contains the turret's below-deck cylindrical magazine, and also increases its elevation above the sides of the deck, making it easier to fire at surface targets near the ship's hull. In addition to radio-proximity-fused shells, this turret can fire smart-fused shells which detonate ahead of the target and spread a wall of fragments. In the late 2010s, Menghe was rumored to be working on radar-guided shells for the HP-76/1, and the "Y" model mount on the Insŏng class features a pronounced block on the left turret cheek which houses a target tracking and illumination radar. These ammunition types allow the 76mm gun turret to function as the ship's forward CIWS, making up for the reduction in both gun and missile CIWS armament over the Haeju class.

In 2016, Menghe announced that the Chŏnggong Missile Design Bureau was working on a guided 76mm round for the HP-76/1 mount, and this weapon was slated for installation on HJ-384 Insŏng in 2020. Due to roadblocks in developing an effective guided 76mm shell, Menghe eventually opted to import and later produce modified 75mm DART projectiles from Banbha. Due to delays in modifying the existing radar and guidance system to support the foreign round, HJ-384 Insŏng was commissioned with only a partially operational HP-76/1Y mount: the turret could still fire unguided 76mm rounds, but the radome housing was empty, and would be completed during subsequent maintenance. HJ-389 Jinyi was the first Insŏng-class destroyer to be commissioned with a fully operational HP-76/1Y system.

The aft CIWS mount was a GBM-23/5 Bulkkot during early development, but with the final version of Plan 1244 it was changed to the GBM-35/2, a navalized version of the DGP-35-2. Although it has a lower rate of fire than the GBM-23/5, this mount can fire the 35mm AHEAD projectile, which uses a programmable smart fuse to detonate ahead of the target and scatter 152 Tungsten submunitions. On this basis, the GBM-35/2 has a higher kill probability and a higher number of stowed kills than the GBM-23/5. Like the 23mm CIWS mounts on other Menghean ships, the GBM-35/2 is usually loaded with a certain share of contact-fused 35mm rounds, and it can be used against surface targets as well as missiles and aircraft.

HJ-390 Saekgu, one of two Insŏng-class destroyers commissioned with the Taeil laser CIWS in the aft position.

Because the GBM-35/2 does not require below-deck magazine or drive equipment, it is possible to install other types of close-in weapon systems on its platform mount, though these could only be swapped out in a major refit. HJ-390 Saekgu and HJ-391 Sunchang were commissioned in late 2022 and early 2023, respectively, with laser weapons in this location, though HJ-392 Hwasŏng was commissioned in late 2023 with the GBM-35/2. Analysts regard the Insŏng class as a prime candidate for the installation of directed energy weapons, because their gas turbine generators can produce a large amount of electricity to power such weapons.

In addition to the HŎ-3 anti-submarine rocket, the Insŏng-class destroyers are armed with two twin 350mm torpedo launchers. These are located on the ship's flanks just forward of the hangar, behind protective covers which shield them from the elements and help reduce the ship's radar signature. These torpedo launchers are reloaded from the same magazine as the ship's helicopters, and can fire the same YŎ-35/2 torpedoes. Normally, two ready torpedoes are stored on the wall of one hangar, so that either one launcher or one helicopter can be reloaded at short notice without having to use the munitions elevator.

To defend against small boats in a restricted environment, there are four pintle mounts around the superstructure for GCh-96 machine guns. Carbines of the JS-103 family are also stored in two onboard arms lockers for use when repelling boarders.

Machinery

The propulsion system of the Insŏng-class destroyers uses a COGLAG configuration, or Combined Gas-Electric and Gas, with integrated electric propulsion linking the gas turbine generators and auxiliary diesel generators to the electric motors and the ship's electrical systems. Specifically, each shaft is directly coupled to an electric motor at its end, and midway down the shaft, a clutch connects to a gearing reduction unit which connects to a gas turbine. The table below summarizes the type and power of the different powerplants and generators distributed throughout the ship.

Designation	Type	Designer	Output	Number
LM2500+G4	Gas turbine generator	GGE	35,000 kW	2
LM2500+G4	Gas turbine (geared)	GGE	33,600 kWe	2
6EY26LW	Diesel generator	Samsan	2,300 kWe	4

The two gas turbine generators in the superstructure, as well as the auxiliary generators throughout the ship, are connected to the propeller shafts by two Samsan S2328N electric motors, which are rated for 32,000 kW of shaft power each. These motors showed serious reliability issues when they were first trialed on the cruiser Chanjok Jachido in 2012, and despite Samsan's efforts to address the problem with the "N" model, the first batch of Insŏng-class destroyers also suffered frequent electric motor failures. Because of the hybrid layout of the combined propulsion system, even with both electric motors inactive it is possible to propel the ship at up to 31 knots on the geared-drive turbines alone, or cruise by powering one shaft on gas turbine power and trailing the other; but this configuration is much less fuel-efficient, especially for low-speed cruising, and it is also louder. As of 2023, the Ministry of National Defense has postponed construction on hulls currently in drydock, and Samsan is under contract to produce a fully reliable model of the S2328 by 2027. The MoND reports that it will be possible to replace the electric motors on existing ships by cutting through the hull side plating while the ship is in drydock, a procedure already permitted for the diesel engines--note on ship side views the white corner marks outlining the plate over the forward diesel generator compartment. Even so, MoND estimates project that a full replacement of the electric motors on the entire Insŏng fleet will not be complete until the late 2030s.

When running at full output, with both the geared gas turbines and the electric motors active, the powerplant generates a total propulsive shaft power of 134,000 kilowatts. This is enough to reach a speed of over 36 knots even at full load. During cold-weather shakedown trials off the west coast of Polvokia, and with a light load of fuel and supplies and no ammunition, HJ-386 Hyangchun reportedly reached 39 knots, though these ideal conditions are unlikely to apply in service. In particular, the ratings in the table and text assume standard ISO atmospheric conditions, with cold intake temperatures. In the tropical South Menghe Sea, where the Menghean Navy typically operates, ambient temperatures often climb as high as 40 degrees Celsius. Under these conditions, the shaft power of the LM2500+G4 turbine at full output can degrade as far as 25,000 kW, with the output of the gas turbine generators falling proportionally. Because the LM2500 is a proven platform based on mature technology, the Insŏngs are not known to suffer from powerplant reliability issues in tropical conditions, but a report compiled by the Ministry of National Defense in 2024 reported that they struggle to reach their top speed in hot weather.

For typical cruising, standard practice is to run a single gas turbine generator at 60-80% power and couple it to both electric motors as well as the ship's own electric circuits. The resulting power is sufficient to cruise at speeds of up to 22 knots, while also powering all of the ship's onboard sensors, electronics, and amenities, negating the need to run any of the diesel generators. This cruising mode is not only quiet, but also fuel-efficient, as only one turbine is running and it is running at its most efficient output range. Due to issues with the electric motors, however, this cruising mode is not always available, and when running on a single shaft, failure of that motor would leave the ship immobilized until one of the geared-drive turbines can be started.

Each propeller shaft is approximately 70 meters long and connects to a five-bladed variabe-pitch propeller with a diameter of 5.4 meters. The variable-pitch blades allow the ship to apply power more efficiently at different output levels, and by reversing the blades, it is possible to rapidly brake or create reverse thrust. In addition to these main shafts, there is a single retractable maneuvering thruster in the forward hull, just underneath the forward VLS array. This propeller has a shaft power of 200 kilowatts, which is sufficient to propel the entire ship to safety at a speed of 5-6 knots in the event of total engine failure to both propeller shafts. Its primary purpose, however, is to assist with docking operations and maneuvering in confined harbors.

Stealth

As stealth ships, the Insŏng-class destroyers incorporate a number of design features which are intended to reduce their radar cross-sections. In most areas, their hull side and superstructure are angled at plus or minus 9.5 degrees from horizontal, to consistently reflect radar waves away from an emitter at most angles. They also enclose a larger proportion of their equipment: nearly all mooring gear, for example, is located in compartments within the forecastle or under the helicopter deck, and many of the wire lifelines retract into the hull sides when personnel are not on deck. Even the life raft canisters are replaced by inflatable slides behind ejectable panels on the main deck.

To reduce the infrared signature of the ship, the gas turbine exhaust uptakes incorporate a mix of passive cool air mixture and active water sleeting. The diesel exhaust uptakes also incorporate air mixing sections, and they exhaust through the tops of the funnels, rather than the side of the hull, to reduce heating of the ship's outer plating.

The design of the Insŏngs also pays attention to reducing the underwater acoustic signature. The Samsan S2328N electric motors driving the propeller shafts in cruising mode are brushless DC electric motors directly coupled to the propeller shafts, with neither wire brushes nor transmission gearboxes contributing to noise. Combined with the fact that the gas turbine generators are located above the waterline, this results in very quiet operation while under electric power. Both the cruising turbines and the sprint turbines feed bleed air to a Prairie-Masker system, further muffling the ship's hull noise and reducing cavitation from the propellers.

Official Menghean government sources state that the ship's radar signature is comparable to that of a small fishing boat, making it harder to detect at long ranges and harder to distinguish from civilian shipping. Because the typical mission profile of an Insŏng-class destroyer would mostly keep it in the open waters of the South Menghe Sea, and away from coastal areas, the ship is also unlikely to be subject to visual tracking from shore. Activating the powerful air search radars and jamming arrays, however, would reveal the ship's approximate location to enemy units over a wide area.

Crew accommodations

The six- and eight-bunk cabins for lower enlisted ranks represent a major improvement over previous Menghean warship classes.

In a bid to maintain crew morale over longer patrols, the Insŏng-class destroyers feature some of the most generous crew accommodations of any Menghean warship class to date. According to an official info sheet published by the Menghean Military Publicity Agency, each Insŏng-class destroyer has bunks for 40 officers, 58 upper enlisted ranks, 232 lower enlisted ranks, and 21 austerity or overflow bunks, as well as 58 showers and 51 toilets. This is more bunks than the ship's actual crew, which consists of 36 officers and 274 enlisted ranks. The extra accommodations, totaling 4 officer bunks, 16 enlisted bunks, and 21 austerity bunks, would be used by a flag officer and their staff when the ship is serving as a formation flagship, and by any additional intelligence analysts, visiting observers, trainees, evacuees, and media teams on board for a particular mission.

All officers enjoy their own private cabins, and the ship's captain and flag officer also have their own private toilets, showers, and staterooms. Upper enlisted personnel are housed in double cabins with two occupants. Lower enlisted personnel are housed in cabins with four to eight occupants. In addition to equipment lockers, all cabins offer access to a desk and chair for paperwork and leisure. Male and female personnel use different heads and shower blocks, and officers and enlisted personnel use different mess halls and lounges.

Aviation and boat facilities

Apart from the Hasŏ-class cruiser, the Insŏngs are the only Menghean warship class to support the Gyundoan-Han GH-36 Mulsuri in the anti-submarine role. The aft hangar has space for two GH-36 helicopters, typically the GH-36N, which has anti-submarine sensors and armament pylons on larger stub wings. Compared to the GH-28 seen on most other Menghean warships, the GH-36 has a longer range, a heavier payload, and moderately improved sensors, at the cost of greater length and mass. As a compound helicopter, the GH-36 can also cruise at 400 km/h and sprint at 450 km/h, allowing it to cover a larger patrol box in the same time frame as the GH-28 and respond more quickly to distant sonar contacts.

The munitions elevator and the aft magazine room are large enough to hold YDH-26 missile assemblies and their boosters. This allows the ship's helicopters to be fitted out for anti-shipping missions. The GH-36N is capable of carrying two YDH-26 missiles, one on each outermost pylon, not enough to overwhelm a warship with a modern surface-to-air missile system but enough to engage naval auxiliaries or missile boats. To attack small surface craft, the ship's helicopter can be loaded with YDJ-48 Salmusa guided missiles, unguided rocket pods, or 30mm gunpods.

On a more typical mission, the ship's GH-36N would be loaded with two to four YŎ-35/2 torpedoes and 42 sonobuoys. This is a comparable loadout to the DY-11DJ fixed-wing carrier-borne ASW aircraft, and double what the GH-28 ASW variants can carry.

To support landing operations in heavy seas, the Insŏng-class destroyers have two hauldown devices that run along tracks on the helipad. Once a helicopter has landed, the recovery plate slides forward along its tracks into the hangar, bringing the helicopter along with it.

Two rigid inflatable boats are stored in enclosed bays aft of the main radar tower, flanking the forward funnel. These are mainly used for moving small numbers of personnel and supplies between ships or between ship and shore. The RHIBs typically embarked by the Insŏng class possess neither the speed nor the capacity to deploy special forces or commando teams, which is not part of the class's typical mission profile.

Operational service

Chŏngdo's world tour

HJ-385 Chŏngdo as she appeared during her arrival in Avallone. Note the Banbhan flag flying from her starboard yardarm.

The second ship in the class, HJ-385 Chŏngdo, embarked on a special world tour shortly after being commissioned into the fleet. As part of this voyage, she circumnavigated the globe traveling east, conducting pre-scheduled courtesy calls at a number of friendly ports along the way. She was accompanied by the underway replenishment ship Yŏngjŏng, but otherwise traveled alone, without a larger battlegroup.

Chŏngdo's voyage started in her namesake port city of Chŏngdo, which she departed on 30 October 2020 three days, after her commissioning ceremony. From there, she made stops in Donggyŏng, Nakazara, the Aijuku Islands, Inishmore, Avallone, Sayamota, Inisheer, Guacara, Kopanes, Selkiö, Satamansuu, Lappo, Puerto Alegre, Ao Mangkon, and Quẚng Phẚ, Sunju, and Chanam, before finally docking in Gyŏngsan for a thorough post-voyage maintenance check. During most of these port visits, Chŏngdo was partially opened to the general public for tours of her deck and some non-sensitive areas. At Nakazara, Avalonne, and Selkiö, Dayashinese, Glasic, and Hallian naval officers were given exclusive guided tours of the ship's interior and allowed to inspect onboard electronic systems.

The voyage also included a number of naval exercises, particularly with Dayashina and Tír Glas. En route from Inishmore to Avalonne, she conducted a rendezvous with the guided missile cruiser Banbha. At several points on her voyage, she also conducted more aggressive exercises, sailing near Sieuxerrian naval bases in Scintillement and Anglian naval bases in the St. George Islands. On the long voyage from Impor to Kopanes, she also sailed close off the coast of Anglia and Lechernt, Sieuxerr, and Sylva, staying outside of EC territorial waters but claiming innocent passage through the EEZ. This was the first time an armed Menghean surface warship had passed through any of these areas, or for that matter through the Maw south of Inisheer. In addition to signaling Menghe's resolve, these maneuvers also provided an opportunity for the Chŏngdo to test her sensor suite against Entente aircraft, surface ships, and submarines.

Itinerary of the Chŏngdo's world tour
2020-11-05	Departs from the city of Chŏngdo
2020-11-07 to 2020-11-10	Nakazara, Dayashina
2020-11-14 to 2020-11-16	Aijuku Islands, Dayashina
2020-11-29 to 2020-12-04	Inishmore, Tír Glas
2020-12-06 to 2020-12-13	Avallone, Tír Glas
2020-12-17 to 2020-12-20	Sayamota, Macchia
2020-12-21 to 2020-12-27	Inisheer, Tír Glas
2021-01-02 to 2021-01-04	San Janos, Federiko
2021-01-08 to 2021-01-15	Guacara, Idacua
2021-01-31 to 2021-02-06	Kopanes, Ostland
2021-02-09 to 2021-02-17	Selkiö, Hallia
2021-02-21 to 2021-02-25	Satamansuu, Uusimaa
2021-03-02 to 2021-03-06	Lappo, Hallia
2021-03-13 to 2021-03-20	Puerto Alegre, Republic of Innominada
2021-03-22 to 2021-03-23	Ao Mangkon, Argentstan
2021-03-25 to 2021-03-28	Quẚng Phẚ, Menghe
2021-03-30 to 2021-04-04	Sunju, Menghe
2021-04-08 to 2021-04-14	Chanam, Menghe
2021-04-17	Arrives at Songsu-do Naval Base

Loss of the Chilsan

Map of SAG Chilsan's sortie during the Second Pan-Septentrion War.
1. 0830 hrs, 11 April: position at the outset of fighting.
2. 1811 hrs: HJ-366 Dongchŏn damaged by torpedo.
3. 2155 hrs: HJ-376 Pungsu sunk by torpedo.
4. 2235 hrs: SAG Chilsan fires cruise missiles.
5. 2304-2320 hrs: GY-224 sunk, GY-226 damaged.
6. 0113 hrs, 12 April: HJ-388 sustains two hits.
7. 0208-0215 hrs: HJ-388 Chilsan sustains a third hit.
8. 0825 hrs: HJ-388 switches to emergency power.
9. 0930 hrs: Rendezvous with firefighting tug.

At the outset of the Second Pan-Septentrion War, Menghe dispatched a surface action group under Rear Admiral Ho Gyŏng-sŏk consisting of the Insŏng-class destroyer Chilsan, two Haeju-class destroyers, and four Chŏndong-class destroyers to conduct a raid on the island of Portcullia. This proved to be one of the Menghean Navy's most ill-fated operations of the war, resulting in the sinking of two ships and severe damage to three more. Chilsan herself made it back to Puerto Alegre with the help of a tugboat, but subsequent evaluations concluded that she was damaged beyond repair.

Composition of SAG Chilsan, 11-12 April 2022

Hull no.	Name	Class	Role	Fate
HJ-388	Chilsan	Insŏng	Leader SAG Chilsan	Struck by missiles; damaged beyond repair
HJ-379	Pungsu	Haeju	Leader 2nd DD Brigade	Sunk by torpedo
GY-224	Josu	Chŏndong-IIa		Sunk by missiles
GY-228	Dolpung	Chŏndong-III		Undamaged
HJ-366	Dongchŏn	Haeju	Leader 9th DD Brigade	Damaged by torpedo; returned to service
GY-227	Ho-u	Chŏndong-III		Undamaged
GY-226	Ilchul	Chŏndong-IIa		Damaged by missiles; returned to service

The Chilsan first came under attack at 2245 hrs local time on April 11th, when a coastal defense battery on Portcullia fired 32 MM.90 missiles at her formation. Against this attack, Chilsan managed to shoot down all incoming missiles, though GY-224 Josu sustained minor damage from missile debris. A second wave of missiles arrived at 2303 hrs local time, severely damaging the Josu and the Ilchul but inflicting no damage on Chilsan.

A third wave of land-launched missiles arrived at 2313 hrs local time. This time, Chilsan survived by a narrow margin: she shot down all but one oncoming missile, against which she deployed an infrared smokescreen from her port forward Baram-2 launcher. The missile passed narrowly over her hull; crew members manning the wheelhouse at the time described seeing its rocket flare pass just a few meters in front of the bridge. Other missiles targeted the Ilchul, which shot them down, and the Josu, which sustained three hits and began breaking apart amidships.

SAG Chilsan came under attack again at 0009 hrs local time on April 12th, when a Typhoon strike unit from Amritsar airbase released a fourth wave of MM.90 missiles from outside of range. Concerned about dwindling stockpiles of shorter-ranged missiles, Captain Yi Yu-sŏk broke with doctrine and engaged with YDG-67 missiles. At 0016 hrs, one missile approached the Chilsan at close range, and was engaged by the ship's GBM-35/2 CIWS mount. The missile was shot down, but its shrapnel and debris continued forward at supersonic speed, peppering the upper section of the aft funnel and disabling the aft fire control radar.

Diagram showing hits sustained by HJ-388 Chilsan during the night of April 11-12 2022.

The fifth wave of MM.90 missiles, launched by Typhoons based at RAF Takata, arrived at 0113 hrs local time. Running low on missiles and firing conservatively, HJ-388 Chilsan was unable to intercept many missiles this time, and suffered two direct hits. One struck the starboard side hull under the helipad forward of the propellers, detonating inside the Section 2-10 lower enlisted crew cabins. The steering gear compartments were ruptured through the roof, but the steering machinery survived; the variable-depth sonar assembly sustained only minor damage, but the aft VDS and TASS operator rooms were completely destroyed. The other missile impacted the hull side under the front corner of the superstructure, continued into the ship, and detonated inside the forward VLS compartment, setting off a large explosion which shattered the windows on the bridge and blinded several of the crew members standing watch there. The interior double bulkheads and outer bulkheads of the VLS array managed to contain the explosion and force it upward, and the crew were able to continue navigating the ship from within the CIC using onboard EO cameras, but damage control teams had to rush to contain the fire, and Insŏng lost half of her remaining missile stores.

At 0215 hours local time, the sixth wave of air-launched MM.90 missiles arrived at Chilsan's position. Using her CIWS, countermeasures, and remaining missiles, Chilsan managed to shoot down or redirect 15 out of 16 missiles, but the 16th struck her aft VLS block, setting off another explosion. Commodore Tran Tan Ali, who had transferred onboard from the Dongchŏn, was in his quarters adjacent to the aft VLS, and died instantly. The aft damage control center was damaged as well, hindering subsequent firefighting operations. Shrapnel from the secondary explosions ruptured the starboard sprinting gas turbine uptake, flooding the aft crew and maintenance compartments with hot smoke from the turbine exhaust. The combination of turbine exhaust and missile cookoffs set off a large fire around the base of the aft funnel.

In the following hours, Chilsan's crew fought to contain the fire, which was spreading aft toward the hangars. The crew shut off the sprinting gas turbines at 0220, thereby limiting the flow of exhaust into the ship's interior, and at 0418 they shut off the aft diesel generators as well. Damage control teams managed to contain the forward half of the fire, protecting the main gas turbine generators and electric motors, but the fire rapidly spread aft, fully engulfing the hangar by 0500 and then creeping into the decks below. There, fed by the fuel bunkers, the fire began creeping forward again. At 0825 Captain Yi ordered the shutdown of the forward gas turbine generators, leaving the ship on emergency electric power from the aft diesel generators alone. With the main electric motors shut down, Chilsan crept forward under power from her maneuvering thruster until 0930, when she met up with firefighting tugboats which helped fully extinguish the flames.

From there, Chilsan was towed to the Namhae Front base in Puerto Alegre and moored in the harbor. Immediate inspections quickly concluded that it would be impossible to restore her to fighting condition within any reasonable timeframe, and her crew were taken ashore, leaving behind only a small security detachment. After the end of the war, the Ministry of National Defense commissioned a more thorough investigation of the damaged Chilsan, attempting to determine whether it would be possible to restore her to service in peacetime. After several months, they determined that both the extensive fire damage to the ship's fitted systems, and the underlying structural damage from two ammunition cookoffs and extensive heating, would make any repair operation comparable in time and expense to the construction of a new ship. This inspection did, however, confirm that most of the Chilsan's forward sensor systems were still in good condition.

On 29 August 2022, the hull of the Chilsan was formally decommissioned and towed out of Puerto Alegre. Rather than arriving at a civilian shipyard for scrapping, however, she was seen moored at Songsu-do Naval Base in October. There, workers at the Gyŏngsan Naval Yard stripped away her usable electronics, propulsion units, and other fittings, and then drydocked her hull. Her undamaged sections were then cut away and used to assist in the construction of one of her sister ships in the adjacent slipway.

Ships in the class

As of April 2023, a total of 11 Insŏng-class destroyers have been commissioned, but one, HJ-388 Chilsan, has been decommissioned. Two more are under construction: HJ-395 Wŏnsan, and HJ-396 Changgi. This rapid rate of construction was the result of simultaneous building work at two sites: the Gyŏngsan Songsu-do Shipyard and the Chŏndu New Naval Facility.

The Insŏng-class destroyers, like their predecessors, are named for Menghean prefecture-level cities. Not coincidentally, a number of them share names with planned or operational battleships of the Greater Menghean Empire. Insŏng and Hwasŏng were the names given to two cancelled super-heavy battleships, and Chŏngdo and Sunju were the names of the two Chŏngdo-class battleships. With the announcement of Wŏnsan as the name of the twelfth planned destroyer in 2020, some observers noted that there are only a few remaining municipalities that do not yet have an active destroyer named for them, raising speculation that the Menghean Navy might alter its naming scheme at some point before the middle of the century.

The initial contract issued by the Ministry of National Defense authorized a production run of 12 ships: one for each carrier battle group, one for each anti-submarine patrol group, and one for extra duties. A 2020 press release mentioned a total production run of 16, with the additional four serving as the core of reorganized amphibious battle groups. In September 2022, a spokesperson for the Ministry of National Defense stated that only one additional Insŏng-class destroyer (HJ-396 Changgi) would be constructed, bringing the total in service to 12 and the total production run to 13. This would be consistent with the MoND's broader announcement the following December that it would scale back the Menghean Navy's long-range amphibious assault capabilities.

Number	Name	Mengja	Builder	Laid Down	Launched	Commissioned	Status (2023-04-10)
HJ-384	Insŏng	仁城	Gyŏngsan	2015-06-24	2017-05-11	2020-09-03	In service
HJ-385	Chŏngdo	青島	Chŏndu	2015-09-07	2017-08-14	2020-10-27	In service
HJ-386	Hyangchun	香春	Chŏndu	2016-12-10	2018-11-11	2021-02-06	In service
HJ-387	Chanam	叉南	Gyŏngsan	2017-05-17	2019-02-20	2021-03-08	In service
HJ-388	Chilsan	漆山	Chŏndu	2017-08-19	2019-05-31	2021-03-27	Damaged in battle; decommissioned 2022-08-29, scrapped, components reused on HJ-396 Changgi.
HJ-389	Jinyi	晉義	Gyŏngsan	2018-09-27	2020-08-17	2022-07-18	In service
HJ-390	Saekgu	塞口	Chŏndu	2018-11-15	2020-08-20	2022-10-04	In service
HJ-391	Sunchang	淳昌	Chŏndu	2019-06-04	2021-03-26	2023-03-31	In service
HJ-392	Hwasŏng	華城	Gyŏngsan	2020-05-26	2022-05-16	2023	Fitting out
HJ-393	Taean	泰安	Chŏndu	2020-08-22	2022-05-16	2024	Fitting out
HJ-394	Gŭmchŏn	錦川	Gyŏngsan	2020-10-26	2022-09-27	2024	Fitting out
HJ-395	Wŏnsan	遠山	Chŏndu	2022-06-21	2024	2025	Under construction
HJ-396	Changgi	蒼旗	Gyŏngsan	2022-06-26	2024	2026	Under construction

See also

• Yamazaki-class guided missile cruiser