Haeju-class destroyer

File:DDG Haeju.png 4-view of DDG Haeju as built
Class overview
Name:	Haeju class
Operators:	Menghe
Preceded by:	Pyŏng'an-class destroyer
Succeeded by:	Insŏng-class destroyer
Built:	2003-2017
In service:	2006-present
Planned:	16
Completed:	16
Active:	16
General characteristics Haeju, as built
Type:	Guided missile destroyer
Displacement:	7,700 tonnes full load
Length:	155.7 m overall 145 m waterline
Beam:	19.8 m o/a 18.2 m w/l
Draught:	6.08 m to keel, full load
Propulsion:	COGAG 4 × LM2500 gas turbine, 33,600 shp 2 shafts
Speed:	33 knots
Range:	4,600 nm (8,500 km) at 20 knots
Boats & landing craft carried:	2 × RHIB
Complement:	24 officers 294 crew
Sensors and processing systems:	AN/SPY-1D radar HR-44 radar AN/SQS-53C hull-mounted sonar AN/SQR-19 towed array sonar
Electronic warfare & decoys:	2 × JJ-8 ESM antenna 6 × JJ-7 ECM antenna 2 × Baram-1 chaff/smoke launcher 2 × D-105 datalink
Armament:	1 × HP-130/1 Type 102 130mm gun Mark 41 Vertical Launching System (96 cells) 8 × YDH-26 anti-ship missile 2 × Subisu CIWS 2 × HBDJ-21/12 depth-charge projector 2 × 2 350mm tube for YŎ-35/2 torpedo
Aircraft carried:	2 × GH-28 helicopter
Aviation facilities:	hangar landing area with hauldown device

The Haeju-class are a group of guided missile destroyers built in Menghe during the 2000s and 2010s. Modeled after the Dayashinese Yamazaki-class guided missile cruisers, they incorporate a number of features licensed from Dayashina, including the Suijin Combat System, the Mark 41 Vertical Launching System, and a COGAG powerplant using four Glasic General Electric LM2500 turbines. The ship design, however, is Menghean in origin, and it incorporates a number of Menghean weapons, including the Type 102 130mm gun turret and two Subisu combined gun-and-missile defense systems.

Under the Menghean Navy's hull classification scheme, the Haeju-class are classified as "main escort ships" (주력 호위함 / 主力護衛艦, Juryŏk Howiham). They are primarily tasked with protecting surface formations against air, sub-surface, and surface threats, with a focus on the former two. The multipurpose Mark 41 VLS, however, allows greater flexibility in the range of possible missions, including land attack and anti-shipping attack. The Haeju class also incorporate a small Brigade command facility to direct the operation of two to four smaller ships, such as frigates or anti-surface destroyers.

The last four ships in the class were built to a modified design with a more advanced sonar system, a larger superstructure, and a different hangar arrangement. They are known as the Onju class.

Development

Menghe commissioned its first "modern" guided missile destroyer, the HJ Pyŏng'an, in 1999. While the ship represented a major improvement over previous Menghean naval air defense capabilities, it was still hindered by a number of shortcomings, including poor RCS reduction, inadequate radar systems, and an inflexible vertical launch system which did not allow the loading of different missile types. To correct these issues, the Menghean Navy reduced the original eight-hull order to four hulls and commissioned a series of design studies on a family of next-generation warships. The resulting "21st Century Fleet" resulted in the Haeju-class destroyer, the Yechŏn-class frigate, and, after a longer delay, the Mirun-class corvette.

With the resolution of the Renkaku Islands dispute in 2001, Menghe improved its relations with Dayashina, which agreed to loosen export restrictions on a range of military technologies including the Suijin Combat System and AN/SPY-1 radar family. The Menghean Navy's design team proceeded to incorporate a number of these technologies into the developing 21st-century destroyer, resulting in development delays. The first ship, HJ Haeju, was laid down on 7 December 2003 at the Gyŏngsan Songsu-do shipyard.

Design

Vertical launch system

The main armament of the Haeju-class destroyers is a Mark 41 Vertical Launching System with twelve 8-cell modules, eight forward at deck level and four aft between the hangars. All use strike-length modules, and can accept a wide variety of missile types. The use of a multi-mission hot-launch vertical launch system grants the Haeju-class increased flexibility over the Pyŏng'an-class, which could only carry long-range anti-air missiles in their rotary launch cylinders.

A typical escort loadout in the mid-to-late 2010s might consist of:

• 12 × HŎ-3 Ryongorŭm anti-submarine rocket
• 48 × YDG-60 long-range anti-air missile
• 16 × YDH-28 anti-ship missile
• 8 × SY-28 or SY-52 land-attack cruise missile
• 48 × YDG-64 medium-range anti-air missile (quadpacked, 12 cells)

Other armament

Gun armament consists of a single Type 102 130mm turret forward. While capable of firing timed-fuse anti-air shells, it is most useful in the coastal bombardment role.

Close-range defensive armament consists of two Subisu CIWS mounts, one at each end of the superstructure. Each mount combines two rotary 5-barrel 23mm autocannons with eight YDG-61 infrared-guided missiles, with 24 missile reloads in a below-deck magazine. The Subisu system is also capable of targeting surface ships with its electro-optical camera system, eliminating the need for dedicated anti-surface autocannon armament.

In place of the heavy 533mm torpedo tubes present on the Pyŏng'an-class, the Haeju-class carry two twin 350mm torpedo launchers, one on each side. These are located behind metal roll-down doors to protect them from the elements and reduce the ship's radar cross-section. A magazine at the waterline contains 48 YŎ-35/2 torpedoes as reloads. A centerline elevator lifts individual reload torpedoes to deck level on a cart, which the crew can then manuever behind the launchers to reload. Torpedoes from this magazine can also be used to re-arm the helicopters.

Additional anti-submarine armament comes in the form of two HBDJ-21/12 mounts on the forward deck, flanking the pedestal for the Subisu CIWS. Each of these can launch twelve 21cm rocket-propelled depth charges to a range of 4000 or 6000 meters, depending on ammunition type. Both programmed-depth and terminal-homing anti-submarine projectiles can be carried, and later development introduced softkill and hardkill anti-torpedo countermeasures. As the 350mm torpedo tubes and vertically launched anti-submarine missiles are more effective, by the mid-2010s most Haeju-class destroyers only carried torpedo countermeasure ammunition in their HBDJ-21/12 launchers.

Powerplant

For propulsion, the Haeju-class destroyers rely on four LM2500 gas turbines in a COGAG arrangement. Two turbines are connected to each propeller shaft, allowing the ship to run power options that range from a single turbine on one shaft for efficient cruising or all four turbines at once for maximum speed. The paired turbines are located in separate engine rooms forward and aft of a central auxiliary machinery space, and the ship's hull is divided by seven watertight bulkheads consisting of spaced hardened steel plates with flame retardant material in between. These help contain flooding in the event of damage below the waterline, limit the spread of fire through the ship, and reduce the damage to other compartments from shrapnel resulting from a missile impact.

Auxiliary power comes from five Taesan T1SJ diesel generators, each producing 1600 kilowatts of electricity. One auxiliary generator is located in each main engine compartment, one is located far astern under the helicopter hangar, and two are located side-by-side under the bridge area forward of the forward engine room. Like the distribution of the gas turbines, the distribution of the diesel generators across four separate watertight sections limits the probability that a single missile impact will cut power to all areas of the ship. The electrical equipment is also divided across two rooms, each of which can manage all the ship's systems if the other is damaged.

Aircraft facilities

The aft hangar structure can accommodate two GH-28 helicopters. Typically, each ship carries one GH-28R anti-submarine helicopter and one GH-28B airborne early warning helicopter, or even two GH-28Bs with anti-submarine helicopter duties falling to other ships in the formation.

Onju subclass

The last four ships in the class, starting with HJ-380 Onju, were built to a modified design, and the Menghean Navy treats them as a separate ship class. The most prominent change is the rebuilding of the quarterdeck to support the Ŭ-100 variable-depth sonar, also used on the Chunchŏn-class frigates. Because the Ŭ-100 is a variable-depth sonar set with a large finned section, it required the addition of an extra deck in the stern of the ship, as well as more sonar processing equipment.

This, in turn, raised the helicopter landing area by a single deck. Raising the hangars by one deck would have blocked the two aft-facing AN/SPY-1 arrays, and changes to the arrangement of AN/SPY-1 panels, though considered, were deemed too extensive to be feasible within the same class. Instead, the designers revived a solution used on the Ginam-class frigates and Hyŏngnam-class destroyers: a helicopter hangar recessed one deck into the ship, with a retractable roof and an internal ramp leading to the flight deck. Though cramped and inconvenient, this semi-recessed hangar allowed the hangar roof to stay at the same level, and maintained adequate clearance aft of the phased array panels.

The designers also expanded the superstructure to enclose the rigid-hulled boats inside hangar structures. The starboard RHIB bay opens directly over the water, while the port bay has deck rails to move the crane the extra two and a half meters to the edge of the deck. These changes added 600 tonnes to the ship's displacement, so to compensate, the designers added a lipped structure on the rear of the hull to reduce drag. Similar structures were later retrofitted to the other Haeju-class destroyers during scheduled maintenance periods.

Other changes were applied to the ship's electronics mast. In place of the previous JJ-6/7 electronic warfare suite, the designers installed two JJ-9 combined ESM/ECM modules, one on each side. The D-105 datalinks were retained, but relocated. Two JJ-7 ECM antennas were also retained, seemingly confirming that the JJ-7 is compatible with the JJ-9 as well as the JJ-6 ESM dome.

Amidships, the Baram-1 chaff and smoke pods were replaced by Baram-2 modules, which use small pyrotechnic charges rather than solid-fuel rockets to deploy their payloads. This change was also applied to the existing Haejus during refits, though the Baram launchers were kept at their original locations on the smaller asymmetric superstructure.

See also

• Yamazaki-class guided missile cruiser