YDH-28

YDH-28
YDH-28YN with cross-section
Type	Anti-ship missile
Place of origin	Menghe
Service history
In service	2007-present
Production history
Manufacturer	Navy Development Arsenal
Specifications
Weight	1,320 kg with booster
Length	5.64 m (missile alone) 6.27 m (with booster)
Diameter	52 cm
Warhead	750 kg warhead
Detonation mechanism	Contact fuse
Propellant	liquid fuel
Operational range	700 km
Flight altitude	sea skimming (5 m)
Speed	Mach 0.8
Guidance system	inertial guidance, satellite navigation, terminal active radar homing and infrared homing

The YDH-28 (Formal designation: 28식 대함 유도탄 / 二八式對艦誘導彈, i-pal-sik daeham yudotan, "Type 28 anti-ship missile;" Short designation 유대함-28 Yudaeham-ipal "YDH-28") is a type of subsonic anti-ship missile developed in Menghe during the early 2000s. It is intended as a heavier, longer-range counterpart to the YDH-26, and it can be fired from the Mark 41 Vertical Launching System or from specialized vertical launch tubes on submarines. The SY-28 is its land-attack cruise missile variant. The YDH-28 has been marketed abroad under the name Mangchi (망치), meaning "Hammer."

Development

In 1996, the Menghean Navy commissioned a study evaluating the advantages of supersonic and subsonic missiles for anti-ship missions. Previous development work under the Democratic People's Republic of Menghe had focused on heavy supersonic missiles like the YDH-23, and while the subsonic YDH-24 represented a major improvement over the YDH-22, it was still regarded as a disappointing weapon. Though the MoND's naval doctrine staff still favored heavy supersonic missiles, the theoretical study concluded that intermediate-range subsonic missiles could deliver the same warhead at a greater range on a smaller airframe, with similar resistance to jamming and more difficult detection. Contemporary experience supported these findings: The YDH-25, licensed from Letnia, had a range of 120 kilometers in a lo-lo trajectory, only slightly more than the small YDH-26 was projected to achieve. Another deciding factor came in 1999, when Menghe and Tír Glas began negotiations on a production license for the Mark 41 Vertical Launching System. Though the license was not approved until 2001, and the first Menghean ships carrying Mk 41 modules did not go to sea until 2005, the possibility of a domestic or foreign vertical launch system revealed the need for a compact, vertically-launched, long-range anti-ship missile.

The YDH-28 was developed in parallel with the lighter, shorter-ranged YDH-26, and was intended to complement it, not replace it. While the YDH-26 was designed by the Buksŏng Industries Group, formerly Institute 92, the YDH-28 was designed by the Navy Development Arsenal. It incorporated some components and experience from Buksŏng, but most development was conducted by the Menghean Navy as an in-house endeavor. The missile entered production in 2007, first for surface ship VLS, with deliveries of the submarine-launched variant beginning in 2009.

Design

For easier manufacture, upgrading, and modification, the YDH-28 is composed of four modular sections: the guidance unit, the warhead, the fuel and wing section, and the propulsion section. On variants of the missile not launched from fixed-wing aircraft, there is also a thrust-vectoring solid-fuel booster on the rear of the missile which propels it to flight speed and angles it onto the correct trajectory. Each section can be replaced with a section of the same type in an armory, and new variants of the missile with a modified module of any type can be easily introduced.

On anti-ship models of the missile, the main guidance unit consists of a high-powered active radar seeker in the nose. This is complemented by an advanced infrared homing camera in a streamlined pod which hangs below the fuselage. On air-launched missiles this pod is permanently fixed in place, while on all other variants it is stored inside the guidance head and extends downward after launch. This allows the missile to be fired out of 533mm torpedo tubes and vertical launch canisters. All variants have a fold-out blade antenna on top of the guidance unit, for transmitting targeting information between missiles or between the missile and a ship or aircraft.

The next segment contains the missile's warhead. Anti-ship models use a cylindrical 750 kg warhead with recessed metal grooves cut into the outer sides; when the warhead detonates, these radiate outward as explosively formed penetrators, increasing the probability of damage to fuel lines, electrical wiring, engines, electronics, and weapon systems beyond the impact point. A variant with a single 500mm forward-facing shaped charge was tested, but never deployed.

The body of the missile contains liquid fuel for the turbojet engine. It also houses the main wing surfaces, both of which fold into the missile body in an overlapping layout before launch. Hinged, spring-loaded panels hold covers over the wing storage slots before launch, and after the wings extend these covers fold back over the empty slots, reducing air resistance. All anti-ship models of the missile have a range of 700 kilometers, though extended-range versions of the SY-28 land-attack missile exist.

Cruise propulsion is provided by a turbojet engine in the rear fuselage module. Air is drawn in through a recessed intake in the bottom of the missile body. A fold-down scoop-type intake was considered in development, but tests found that the current design achieved adequate airflow with fewer moving parts. In storage the intake is covered by a watertight plate, which blows off with the help of exploding bolts when the missile transitions from the solid-fuel booster to the cruising engine.

Flight trajectory

One of the interesting features of the YDH-28 is its smart programming. Each missile can be programmed to follow a custom trajectory after launch, approaching the target on a different axis from the launch platform to avoid detection or evading the locations of known screen ships. The shipboard user interface, also present on bombers (though not strike aircraft) assists in setting up trajectories so that missiles on different courses arrive on target at the same time, overwhelming the enemy's missile interception capabilities. By default, the YDH-28 follows a sea skimming trajectory for the entire flight, and if it passes over land it can enter a terrain-following radar mode to fly low over hills and mountains. The terrain-following radar also reduces the probability of colliding with rogue waves and aids navigation in rough seas.

Once a group of missiles is 50 kilometers from the designated target area, one missile climbs to an altitude of 100 meters and begins scanning for targets. Using its onboard datalink, it transmits the number and location of targets to the other missiles in the area, a useful feature when engaging ships which were detected in an area of uncertainty or which moved after the launch coordinates were generated. If the "spotting" missile is destroyed, another climbs to take its place. In a jamming-free environment, the networked missiles allocate targets among themselves, assigning multiple missiles to large radar contacts (carriers, cargo ships). The launch platform can also pre-program target selection parameters. In a high-jamming or high-EMCON environment, each missile randomly selects a target, with selection weighted toward large targets.

With targets allocated, the "spotting" missile drops to sea-skimming altitude, and groups of missiles fan out to approach from multiple angles at the same time. During the final approach, the missiles carry out pseudo-random evasive maneuvers to avoid gunfire and surface-to-air missiles. The high-powered radar seekers are designed to burn through jamming by ship-based antennas and jamming decoys, and the imaging-infrared seeker cross-references targets to further improve jamming resistance. If a missile does overshoot its target due to countermeasures, it circles back to re-engage from the other side.

Variants (YDH-28)

YDH-28G

YDH-28G is the first generation or production batch of YDH-28 missiles. These had a simpler networking and guidance system, with preprogrammed trajectories but no inter-missile coordination on approach. Introduced in 2007.

YDH-28YG

Surface-launched variant fired from 264-inch (6.7-meter) strike-length vertical launch canisters. Used by surface ships, land-based TELs, and a launch system disguised as a shipping container.

YDH-28ŎG

Submarine-launched variant fired from 533mm torpedo tubes. Stored in a watertight container for handling and launch.

YDH-28BG

Variant fired from fixed-wing aircraft. The solid-fuel booster is omitted and the infrared seeker is permanently extended.

YDH-28N

The YDH-28N is an improved version of the YDH-28 with a new guidance module. These missiles have the full networking and guidance system described above, and are better at distinguishing surface ships from floating or airborne radar countermeasures. Because the missile design is modular, the guidance module can be retrofitted to G-type missiles in an arsenal or warehouse. Introduced in 2012.

YDH-28YN

Surface-launched variant fired from 264-inch (6.7-meter) strike-length vertical launch canisters. Used by surface ships, land-based TELs, and a launch system disguised as a shipping container.

YDH-28ŎN

Submarine-launched variant fired from 533mm torpedo tubes. Stored in a watertight container for handling and launch.

YDH-28JN

Variant fired from underwater 533mm VLS tubes on certain submarines, such as the Daedam and modified Chungsŏng-III classes.

YDH-28BN

Variant fired from fixed-wing aircraft. The solid-fuel booster is omitted and the infrared seeker is permanently extended.

SY-28

The SY-28 (Formal designation: 28식 순항 유도탄 / 二八式巡航誘導彈, i-pal-sik sunhang yudotan, "Type 28 cruise missile;" Short designation 순유-28 Sunyu-ipal "SY-28") is a land-attack cruise missile based on the YDH-28 airframe. It uses the same missile body, turbojet engine, and launch interface as the YDH-28, but with a different warhead module and guidance system. While the YDH-28 has a rounded radar-transparent nose, the SY-28 has an electro-optical camera in the center of its nose, with no underslung optics blister. During its terminal approach, the SY-28 uses this camera to correct its navigation based on images of the target area; identify its target relative to other landmarks in the target area; and home in on that target. As a result, the missile is able to accurately home in on targets even when the enemy is spoofing or jamming CSNS signals.

A disadvantage of this guidance mode is that the SY-28 can only be used against large, fixed structures, and it can only be targeted at areas which are part of a virtual target database uploaded to the launch platform. Independent defense analysts believe that the SY-28 most likely retains the YDH-28's ability to re-allocate individual targets between missiles as a swarm approaches its target area, but speculate that it may not be possible to re-target a missile after launch. As on the YDH-28, the missile's datalink can also transmit targeting information to a nearby friendly ship or aircraft, useful for assessing strike damage from preceding missiles.

The SY-28 uses a different warhead module than the YDH-28. Initial reports indicated the existence of three warhead types: a 500kg penetrator warhead for attacking bunkers and hardened structures; a top-attack submunition warhead for attacking parked aircraft and grouped vehicles; and a runway-cratering submunition warhead for disabling airfields. Typically, warships only carry the ground-penetrating variant, and it is not known whether submarine-launched versions of the other two types exist. A new warhead type was unveiled in 2019; this is a programmable-effects warhead with an after-impact penetration mode and an overhead airbursting mode. This allows for a single missile to serve the same function as the SY-28G and SY-28N. The SY-28D is also believed to incorporate improved artificial intelligence technology, resulting in a higher probability of correct target identification.

SY-28G(Y)

Surface-launched variant fired from 264-inch (6.7-meter) strike-length vertical launch canisters, using the 500kg penetrator warhead. Has a range of 1000 kilometers, longer than the YDH-28, because of the lighter warhead and guidance unit.

SY-28N(Y)

Surface-launched variant fired from 264-inch (6.7-meter) strike-length vertical launch canisters, using Buŏng-i smart-fused top-attack submunitions. Can be used against grouped vehicles, supply depots, or parked aircraft. The missile can dispense all of its submunitions at once, or spread them out over up to five points, useful when engaging aircraft parked at different locations around an airfield.

SY-28G(Ŏ)

Submarine-launched variant using the 500kg penetrator warhead, fired from 533mm torpedo tubes.

SY-28G(J)

Submarine-launched variant using the 500kg penetrator warhead, fired from submerged verical launch tubes.

SY-28D(J)

Suspected submarine-launched variant using rocket-propelled runway-cratering submunitions. Later revealed to be a prototype designation for the SY-56 Ho-u. The designation SY-28D(J) was actually applied to the submarine-launched variant of the SY-28D, with a programmable-effects warhead.

SY-28G(B)

Air-launched variant using the 500kg penetrator warhead.

SY-28N(B)

Air-launched variant using Buŏng-i smart-fused top-attack submunitions.

BJJ-28

The BJJ-28 is an airborne jamming platform based on the YDH-28 missile body. In place of a radar seeker and warhead, it contains a powerful radar jamming antenna and a high-output battery. The rest of the guidance system - namely, the CSNS and inertial navigation units, the sea-following radar, and the networking antenna - is carried over from the YDH-28.

In a typical massed missile attack, one or more BJJ-28 jammers would trail at the back of the missile group at a slightly higher altitude, jamming air-search radar, mid-course missile command, missile guidance, and active radar homing channels. The presence of BJJ-28 jammers is intended to delay positive acquisition of incoming missile tracks, reduce the hit probability of enemy surface-to-air missiles, and delay confirmation of successful intercepts. While an enemy force could burn through the BJJ-28's jamming noise by switching missiles to semi-active radar homing mode and using shipboard radar illuminators, this would impose a cap on the rate at which the enemy force is able to engage incoming missiles. Some unofficial Menghean sources claim that the BJJ-28 is also able to jam ship-to-missile datalinks and ship-to-ship datalinks, which would further restrict interception rates.

The onboard jammer has three pre-programmable activity profiles. In the first, it remains silent until the first missiles in the strike package perform their terminal pop-up maneuver to acquire the target, removing the risk that radio emissions could alert enemy passive sensors. In the second, the missile remains silent until a radar warning receiver indicates that the missile group has been detected. In the third, the onboard jammer activates at a pre-programmed waypoint. This mode could be used to protect a missile attack against over-the-horizon SAM fire directed by airborne early warning radar. It could also be used to generate a false cloud of radar contacts, disguising a single decoy missile as a massed cruise missile strike.

Though originally developed to support anti-ship missile strikes, the BJJ-28 can also support land-attack strikes consisting of SY-28 cruise missiles. SAMP/T, one of the EC's main land-based surface-to-air missile systems, is derived from the naval Aster system, against which the BJJ-28 is believed to specialize.

See also

• YDH-24
• YDH-26