Manhwagyŏng torpedo countermeasure

Manhwagyŏng ("Kaleidoscope") is a family of acoustic anti-torpedo countermeasure devices developed in Menghe. Manhwagyŏng-H is a compressed-air launcher mounted on surface ships, and Manhwagyŏng-J is a self-contained launch tube system mounted in the outer hulls of submarines. Each system can fire a variety of projectiles, which have a different tail section depending on the launch system and can use different acoustic heads. Both systems entered service in 2012 and now see use on a large number of Menghean warships. It is capable of countering active and passive acoustic homing torpdoes, including wire-guided ones, as well as wake homing torpedoes which rely on active sonar to detect bubble trails.

Interface

The Manhwagyŏng system is controlled from a ship-based console and has a variety of readiness modes. It receives information directly from the ship's sonar systems, including an optional dedicated high-frequency torpedo detection sonar developed for the system. In standard engagement mode, the system alerts the operator to an incoming torpedo, and the operator decides whether to alter course and launch countermeasures. There is also a high-readiness mode, in which the system automatically launches decoys at an incoming torpedo without the delay of operator input.

Once the decoys are deployed, an onboard computer determines the optimal evasive course to follow, based on the torpedo's speed, its guidance type, and its angle of approach. As with the launch system, the helmsman can either manually steer and accelerate onto the recommended course or allow the Manhwahyŏng system to directly input speed and bearing commands to the ship's autopilot.

Manhwagyŏng-H

Manhwagyŏng-H is the version of the system designed for use by surface ships. Each mount has twelve launch tubes in two groups of six, and a typical system includes two mounts per ship. The launch tubes are fixed in elevation at 45 degrees, but the mount can pivot automatically to place the projectiles in the path of the torpedo. The projectiles are launched with compressed air, eliminating the rocket backblast issues present on ships with HBDJ-21 series derived systems. Once in the water, they float a small distance (<10 meters) below the surface to simulate the depth of a surface ship.

Manhwagyŏng-J

Manhwagyŏng-J is the version of the system designed for use by submarines. Each module consists of four launch tubes, and as many as twelve modules can be installed on a single submarine, for a total of 48 decoys, jammers, and communications buoys. The entire module is designed to be installed in the space between the inner and outer hulls, meaning that it does not require any launch holes in the pressure hull - a potential source of structural weakness and leakage in the event of a nearby blast. The projectiles used by this mount are longer, with a propeller module to drive them clear of the submarine.

Manhwagyŏng-J launch modules and projectiles are able to operate at depths of up to 1,200 meters (3,900 feet), beyond the crush depth of any existing Menghean submarine class. The projectile maintains a constant depth after its release.

Payload types

The Manhwagyŏng projectile is modular, meaning that while there are different tail sections for the sub-launched and ship-launched versions, they share the same set of payload types. Three payload options are available for both launch systems.

• Chŏnghwa is an acoustic decoy which imitates the ship's (or submarine's) acoustic signature, generating a field of false targets for the torpedo to follow. If the torpedo is using active homing, the projectile detects the frequency of its sonar and mimics it, referencing an onboard database of known hostile torpedoes. The torpedo repeatedly engages these false targets until it runs out of fuel or battery power, allowing the ship or submarine to escape.
• Honghwa is an acoustic jammer which generates a high level of acoustic noise across different frequencies, blocking out the acoustic signature of the submarine or surface ship behind it. It is less common than Chŏnghwa, partly because a decoy leaves open the possibility that the submarine was a false target, but it is reportedly capable of interfering in the wake-finding sonar of wake-homing torpedoes.
• Bulbit is a communications buoy based on the Manhwagyŏng-J system. It rises to the surface and repeatedly broadcasts a pre-recorded message. The broadcast can be picked up by satellites, patrol aircraft, and surface ships. After the programmed broadcast duration ends, the buoy floods its ballast tanks and sinks to the bottom, allowing the submarine to minimize exposure to enemy surface-search radar and ESM assets. While mainly intended for brief broadcasts, Bulbit can also be used to send a distress signal if the submarine sinks, broadcasting its status and location to all friendly assets in the area. If the emergency alert button is pressed, Bulbit automatically launches on this broadcast mode.
• Silhŏm-Ch is a test version of the Chŏnghwa projectile. It shares the same functionality but rises to the surface after running out of power instead of sinking to the seafloor. It is rechargeable and reusable, and its shell is painted orange for easy visual spotting.
• Silhŏm-H is a test version of the Honghwa projectile, with the same modifications applied to Silhŏm-Ch.

All projectiles have a diameter of 140mm. Length ranges from 850mm on the submarine-launched system to 1015mm on the surface-launched system.