YDH-26

YDH-26
Major variants of the YDH-26
Type	Anti-ship missile
Place of origin	Menghe
Service history
In service	2002-present
Production history
Manufacturer	Buksŏng Industries Group
Specifications
Weight	540 kg (YDH-26GJS) 450 kg (YDH-26G)
Length	401 cm (YDH-26GJS) 332 cm (YDH-26G)
Diameter	35 cm
Warhead	130 kg warhead
Detonation mechanism	Contact fuse
Propellant	kerosene
Operational range	110 km
Flight altitude	sea skimming (3 m)
Speed	Mach 0.8
Guidance system	inertial guidance, terminal active radar homing

The YDH-26 Mulchongsae (Formal designation: 26식 대함 유도탄 / 二六式對艦誘導彈, i-ryuk-sik daeham yudotan, "Type 26 anti-ship missile;" Short designation 유대함-26 Yudaeham-iryuk "YDH-26") is a type of subsonic anti-ship missile developed in Menghe during the late 1990s and early 2000s. With a mass of 450 kilograms and a 100-kilogram warhead, it is relatively lightweight and compact, serving as a smaller, cheaper complement to heavier Menghean anti-ship missiles like the YDH-23 and YDH-28.

A related feature of the YDH-26 is its versatility. The missile can be fired from angled launch boxes, vertical launch cells, submarine torpedo tubes, submarine vertical missile tubes, helicopters, fixed-wing aircraft, modified shipping containers, and a variety of land vehicles. All launch platforms use the same common missile fuselage, which can be modified in the field with a solid-fuel booster and two screw-on bomb lugs.

Development

The YDH-26 was developed by the Buksŏng Industries Group, formerly Institute 92, Menghe's main manufacturer of medium-range subsonic missiles. It was conceived as a lighter replacement for the YDH-24, able to be carried by helicopters and carrier-borne fighters. In this role, it would complement the larger YDH-28, which offered a longer range and heavier warhead at the cost of greater size and weight. Designers also emphasized minimizing production costs, to aid in mass-production and make the missile more attractive on the export market.

At-sea test firings of the YDH-26 took place in 2000, using a modified Plan 261 missile boat as the launch platform. The missile was found to perform well, and in 2002 it was introduced to service on the Sŏwicho-class corvette Hwŏncho, the second in her class.

Design

The subsonic YDH-26 follows a conventional cruciform wing design, with fixed stabilizers mounted halfway down the missile's length and similarly shaped steering fins mounted at the rear. An intake for the turbojet is slung underneath the missile's body. Prior to launch, these fins are folded against the missile's body, allowing it to be stored in more compact launch containers or in compact multiple carriage units on aircraft. Once the missile is launched, these fins spring open after a short delay, giving the missile time to exit its tube or fall away from the aircraft or helicopter firing it. It is also possible for a ground crew to manually unfold the fins before mounting the missile onto an aircraft.

The YDH-28 is relatively compact, even when compared with other subsonic anti-ship missiles. The air-launched YDH-26GBi has a mass of only 448 kilograms; the YDH-26NBi, with its underslung camera, masses out at 462 kg, and the booster adds 104 kg. Tradeoffs of this small size include a short range of 110 kilometers and a small 100-kilogram warhead. Buksŏng's promotional material states that the missile is recommended for use against warships displacing between 400 and 4,000 tonnes, i.e., frigates and corvettes, though it can also be used to damage larger ships and impair their effectiveness against a follow-up strike, or to saturate a large escort group.

By default, the YDH-26 uses inertial navigation to travel to an attack point designated upon launch. It makes its initial approach at an altitude of 15 meters to avoid striking friendly warships and rogue waves. Once it is 25 kilometers from the target position, the missile climbs in altitude, activates its radar seeker, and begins searching for targets. When a target in the designated area is detected, the missile updates its course and drops to a sea skimming altitude of 3 meters, where it makes its final approach. At a range of two kilometers, the missile performs a pop-up maneuver and descends on a quasi-ballistic arched trajectory, reducing the hit probability of enemy defenses and increasing the probability of a hit against a small or low target.

Due to its small size and relative simplicity, the YDH-26 is considered one of the most cost-efficient missiles in service in Septentrion. This is especially true of the basic "G" variants, which reportedly cost under $400,000 to manufacture. The missile is also designed for easy storage and maintenance, and can be stored fully-fueled for a period of up to 15 years.

Each major variant family (G, G1, N) describes a common missile fuselage. All such base fuselages have three recesses for bomb suspension lugs on top, and mounting points for a solid-fuel rocket booster on the rear. This means that a ground crew at a rear base, on a warship, or in the field can easily modify a missile for the appropriate launch platform. Missiles dropped from fixed-wing aircraft and helicopters use bomb suspension lugs, but these are omitted from canister-launched missiles to reduce the missile's vertical footprint. Variants dropped from helicopters or fired from canisters use the solid-fuel booster to accelerate the missile until its turbojet engine can take over, while variants dropped from fixed-wing aircraft already have forward velocity and omit this booster to save weight and space. Ground crew can also manually unfold the missile's fins before loading it onto an aircraft; this is said to reduce drag and strain on the missile airframe, though it is still possible for both helicopters and fixed-wing aicraft to carry the YDH-26 in a fins-folded configuration. On some aircraft, including the Songrim SR-8, reducing the footprint in this fashion allows more missiles to be carried.

Early angled launch boxes for the YDH-26 used a custom design, but from 2007 onward it was most often deployed in modified self-defense-length (4.1-meter) Mark 41 vertical launch canisters, with bolted-on stacking frames for mounting to a launch bracket or vehicle. This same Mk41 VLS cell conversion was also used for many Menghean surface-to-air missile TELs and TELARs, such as those of the Chŏlgung air defense system. This arrangement indicates that as early as 2007, the YDH-26 was able to be launched from a ship's vertical launch cells, though this was only confirmed with a test in 2013 and remained uncommon except on small ships.

When carried on aircraft and helicopters, the YDH-26 can be mounted directly to a hardpoint using its bomb suspension lugs, without the use of a rail adapter. The three suspension lug wells are spaced at 250mm and 355mm, to allow carriage by aircraft with foreign-standard bomb lug spacing as well as the Menghean standard. In this arrangement, the missile is first dropped from the hardpoint, at which point its booster (helicopter-fired) or turbojet (fixed-wing-fired) takes over and propels it forward. Intertial guidance coordinates, mid-course waypoints, and search start coordinates can be programmed on the ground or from the cockpit.

When carried on submarines, the YDH-26 is stored with its fins folded in a canister 533mm in diameter. This canister unit, designated ŎYY-26, can be fired from either horizontal torpedo tubes or vertical missile launch tubes of the type seen on the Daedam-class submarines. In either case, the canister is ejected from the torpedo tube by compressed water, at which point it rises to the surface, with a free-flooding section on the rear tilting the nose upward. Once the nose of the tube breaks the surface, its cap ejects and the missile's booster fires, ejecting it from the tube.

Variants

The YDH-26 has a large family tree, with air-launched, surface-launched, helicopter-launched, and submarine-launched variants. The missile body itself has also undergone change over time, with spinoff variants such as the SY-26.

YDH-26

YDH-26G

This is the standard baseline variant of the YDH-26, introduced in 2002. It has a simple active radar seeker and radio altimeter, and uses a low-cost turbojet engine to reach a range of 110 kilometers.

YDH-26N

This is the designation used for YDH-26G missiles which have undergone an incrmental software upgrade. The G1 variant possesses home-on-jam capability, slightly improved resistance to countermeasures, and terrain-following capability when cruising over land. It also performs pseudo-random maneuvers during its final 5-kilometer approach, to reduce the probability of interception by point-defense SAM systems and close-in weapon systems.

YDH-26D

This variant, introduced in 2015, features an infrared imaging seeker in a pod slung under the fuselage. The guidance control unit is also lengthened to support associated additional electronics. The imaging seeker provides a measure of redundancy against jamming, chaff, and decoys, while the active radar seeker provides redundancy against smoke and flares. Guidance improvements from the YDH-26N are also carried forward into this model.

YDH-26R

A new model introduced in 2023, with a higher-resolution but equally compact infrared camera. The guidance section reportedly uses an AI program to identify ships by their radar return and infrared silhouette: it can prioritize targets assigned by the operator, and will disengage from ships it identifies as neutral, friendly, or civilian.

YDH-90

This missile was unveiled at a defense expo in 2011, initially under the designation YDH-26N (which, confusingly, was later used for another YDH-26 variant). In 2014, Menghean sources officially confirmed that it bore the designation YDH-90, indicating that the Menghean Ministry of National Defense considered it a new missile. It nevertheless shares many components with the YDH-26, using the same seeker head, warhead, and control surfaces.

The primary difference with other YDH-26 models is a Donghae Gi-3-115 turbofan engine, which sits offset toward the bottom of the fuselage, with a larger intake and additional fuel tank space overhead. These changes extend the range of the missile to 280 kilometers, a target figure which the Menghean Navy requested in order to out-range MASURCA-V surface-to-air missiles in Sieuxerrian carrier battle groups. Aircraft armed with the "G" variant could operate from well outside the range of Aster missile coverage, but had to conduct risky below-horizon approaches to avoid engagement by long-range surface-to-air missiles.

Because of these changes, the YDH-26N is considerably larger in the vertical dimension, and also substantially heavier. As a result, it cannot be fired from standard YDH-26 surface launch boxes, which are derived from Mark 41 self-defense cells. Nor can it be fired from 533mm submarine torpedo tubes or submarine launch tubes. Only air-launched versions exist in Menghean service, though a model land-launch vehicle was displayed at an exhibition in 2018, with reshaped launch cells to support the deeper missile body.

All YDH-90 variants, starting with the YDH-90G, use an under-slung infrared imaging seeker, the same model carried on the later YDH-26D.

SY-26

The SY-26 is a land-attack cruise missile derived from the YDH-26, akin to the AGM-84E SLAM. It has a large electro-optical seeker in the nose and CSNS guidance for attacking stationary targets. The electro-optical seeker allows the missile to engage moving vehicles and targets with unknown exact coordinates, and provides resistance against CSNS jamming. Despite its cruise missile designation (SY, sunyang yudotan), the SY-26 can also engage surface ships by locking onto their infrared signatures.

The warhead module is also changed, with a 100kg programmable armor-penetrating warhead in place of the HE prefragmented warhead on the YDH-26. This warhead can be programmed to detonate on impact, for use against soft targets, or after a brief delay, for use against hardened targets.

In 2020, the Menghean Ministry of National Defense indicated that new SY-26 deliveries to the Menghean Army would cease, with the SY-55 Kkamagwi replacing it in Army Aviation units and Army SY-26s moved to Naval Aviation stockpiles. In terms of overall characteristics, the two missiles have similar capabilities. During the One-Month War, however, Menghean Army Aviation units did fire SY-26 missiles, indicating that by 2022 the Army's SY-26 stockpile had not been fully replaced.

SY-90

The SY-90 is to the YDH-90 as the SY-26 is to the YDH-26: a land-attack conversion with the SY-26's seeker and warhead on the YDH-90's body. It was introduced in 2017, and has only been delivered to Menghean Navy units.

By launch method

Fixed-wing air-launched variants

Variants of the YDH-26 fired from fixed-wing aircraft have designations starting with "Bi," which denotes bihaenggi or airplane. These variants retain the folding wings of the land-based models, allowing them to be packed closer together and carried closer to the aircraft's fuselage. They omit the solid-launch booster, which is unnecessary if the missile is launched with sufficient speed and altitude for the sustainer engine to operate.

The YDH-26Bi family has two standard bomb suspension lugs, which are spaced 250mm apart. This allows direct carriage on bomb racks and pylons compatible with Menghean 500-kilogram guided bombs, without the need for a launch rail or adapter pylon. Once released, the missile briefly enters free fall to clear the launch plane, then its fins snap open and its engine activates. Menghean training documents recommend a launch altitude of at least 100 meters above ground level so that the missile can gain lift before impacting the ground.

Helicopter-launched variants

Helicopter-launched variants have designations with the suffix "Jik," denoting jiksŭnggi or helicopter. Like the "Bi" variants, they have two overhead bomb suspension lugs at a 250mm interval, but they retain the solid-fuel booster, to allow launches from low speed and hover positions. When released, the missile first drops in free fall with its fins closed, then snaps open its fins and fires the solid-fuel booster, climbing and accelerating forward. After the booster is exhausted, it drops off, and the sustainer motor kicks in.

Submarine-launched variants

A submarine-launched variant was unveiled in 2006, though it was rumored to have been in development several years earlier. Submarine-launched missiles are derived from the booster-equipped land-launched variants, but are stored inside a watertight, pressure-resistant cylinder with the dimensions of a 533mm torpedo. This cylinder can be ejected from a submarine's torpedo tube at a depth shallower than 50 meters, at which point it tilts nose-up and rises to the surface. When it reaches the surface, its cap ejects, and the missile flies out under solid-fuel power.

Coastal defense system

In 2005, as part of the country's pivot to defensive warfare, the Coastal Defense Forces of the Menghean Army placed a request for a self-propelled, land-based launcher for the YDH-26 missile. The resulting system, which was publicly displayed in 2008 and bears the designation JYDH-26 (Jaju-Yudotan Dae-Ham, Self-Propelled Missile, Anti-Ship), consists of eight vehicles:

• 1x JYDH-26JS (Jungdae Salyŏngcha), Company/battery command vehicle with radio and wire connections. Crew of five.
• 1x JYDH-26SR (Susaek Reida), search radar vehicle with an elevating mast to detect ships within horizon range. Crew of three.
• 3x JYDH-26BG (Balsagi), launcher vehicle with eight missiles. Crew of four.
• 3x JYDH-26JCh (Jaejangjŏn-Cha), reload vehicle with eight missile boxes and a crane. Crew of two.

The original JYDH-26 system was designed around the Taekchŏn T512 heavy utility truck. It was later supplemented by a lighter system on the Samsan S915, which carries fewer missiles per truck (4 instead of 8) and has a shorter-range acquisition radar, but is cheaper to produce and maintain.

Byŏk container battery

The "Byŏk" ("wall") system is a version of the YDH-26 launch battery in which all components are installed in 20-foot ISO containers. A full-size battery is made up of fifteen 20' containers: three for the command post, two each for the radar and drone posts, and two for each of the four launch platoons. Other combinations are also possible, including a minimum battery with three command modules and one launch platoon. The modules can be linked with VHF radio, SHF radio (a modified MChGJ-0800), or cables running over the ground. The manned modules contain not only control equipment, but also basic living amenities: bunks, lockers, food and water storage, and an electric stovetop. Thus, once the unit is emplaced, the crew does not require separate accommodations.

The Byŏk battery can be arranged as a tightly packed installation, but it is also possible to disperse the individual platoons over an area as much as 20 kilometers in diameter. The modules within each platoon must be closer together - one brochure provides a figure of 50 meters - but otherwise there are no restrictions on their arrangement. They can also be painted in the liveries of private shipping companies, and shuttled between positions on civilian trucks. This allows a commander to disperse the modules across parking lots, construction sites, and shipping centers, making it virtually impossible for an adversary to distinguish battery elements from civilian containers using satellite and aerial imagery.

• Byŏkdul B1: Launch unit with four YDH-26 boxes and a rolling steel door on the roof. This module is uncrewed, and controlled by a B2 module.
• Byŏkdul B2: Launch control unit with control stations, radio antennas, and a generator, as well as bunks and basic amenities for two crew members.
• Byŏkdul S1: First half of the battery command post.
• Byŏkdul S2: Second half of the battery command post.
• Byŏkdul S3: Living spaces for the battery command crew.
• Byŏkdul J1: Long-range surface ducting radar and generator.
• Byŏkdul J2: Control and communications unit for the surface search radar, with four crew, bunks, and basic amenities.
• Byŏkdul M1: Contains two helicopter-type unmanned aerial vehicles with visual and IR cameras, which can visually identify radar contacts and assess post-strike damage.
• Byŏkdul M2: Control and communications unit for the unmanned aerial vehicle, with three crew, bunks, and basic amenities.

Variants

Variants without boosters

• YDH-26G: baseline model with radar guidance only
• YDH-26N: model with backup infrared seeker
• YDH-26D: model with backup infrared seeker and pseudorandom evasive maneuver profile

Variants with boosters

• YDH-26GH: baseline model with radar guidance only
• YDH-26NH: model with backup infrared seeker
• YDH-26DH: model with backup infrared seeker and pseudorandom evasive maneuver profile

Submarine launch variants

• YDH-26GJ: baseline model with radar guidance only
• YDH-26NJ: model with backup infrared seeker
• YDH-26DJ: model with backup infrared seeker and pseudorandom evasive maneuver profile

See also

• YDH-24
• YDH-28