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Military


MSH-571 Yang Yang

Through the 1990s the navy remained a small force primarily dedicated to protecting the nation's territorial waters and islands. Now it has started to take on the features of an "Ocean-Going Navy" of the 21st century by building and commissioning Korean versions of a destroyer (KDX), a heavy landing ship (LST), a mine laying ship (MLS), and a mine hunting ship (MSH).

The Republic of Korea Navy mine hunter Yang Yang was operational at the beginning of 2000, and at that time seven more of the 730-ton ships were on order. By 2005 South Korea had a large mine countermeasures project under way, with up to 11 Yang Yang-class mine hunters expected to enter service in the next decade. By 2006 the navy was pushing forward with mine-clearing helicopter program by cutting back on mine-hunter acquisition, and it appeared this would mark the end of Yang Yang class construction. Indeed, by 2008, a total of only three were operational.

The Yang Yang class design is an enlarged version of the earlier Kang Keong / Swallow Chebi] Class MHC class using the same construction technology and layout as the earlier vessels. They are designed and built in accordance with most-up graded naval standard for anti-shock, anti-magnetic, minimum under water accoustic and electro magnetic interference. Newly introduced facilities ensures perfect quality assurance for the single skin G.R.P. hull structure.

The minehunting capabilities consist of: the Thomson Marconi SAS TSM 2061 Mk 3 combat system integrating a Thomson Marconi 2093 variable depth minehunting sonar; Raytheon I-band navigation radar; and two Italian Gaymarine Pluto Gigas ROVs. The ships are also fitted with the BAE Systems Wire Sweep Mk 9 deep wire sweep system and CIS combined influence sweep. Self-defence is provided by a Sea Vulcan Gatling 20 mm light AA gun and two 7.62 mm machine guns.

A Kongsberg Simrad integrated navigation and dynamic positioning system is fitted to aid in precise manoeuvring during minehunting and route survey operations. The machinery system comprises two MTU 2,000 bhp diesels driving two independent vertical Voith-Schneider cycloidal propellers through a gearbox and universal joint shaft. It is said that it is possible to move sideways and rotate 360 ??degrees by using a vertical cycloidal propeller called a point Schneider propeller. In addition, it is said that unlike other ships, this vertical propeller does not have a directional rudder because it functions as a propeller and a rudder at the same time.

Marine cycloidal propellers were originally developed in the early 1920's and are commonly known as Voith-Schneider propulsion systems. The cycloidal propeller derives its name from the cycloidal path that individual propeller blades on its propeller hub circumscribe as the propeller moves through the water. These unique propellers have blades which extend parallel to the rotational axis of the propeller hub and are pivotal about discrete blade axes parallel to the propeller rotational axis. In propulsion systems of this type, the direction and magnitude of thrust may be varied along any line normal to the rotational axis of the hub, thereby obviating the need for directional rudders. In contrast, traditional helical-screw propellers have blades which are perpendicular to the rotational axis and can only vary the magnitude of thrust along their axis, thereby requiring rudders to change the direction of thrust.

In a cycloidal propeller assembly, the propeller blades operate as lifting surfaces. The angles of attack of these blades continuously varies from zero to a maximum in the desired direction of travel, then back to zero during each forward and aft half-cycle or half propeller rotation. The lift force varies as each blade circumscribes the orbital path and the time average of this force vector, for all blades over a complete revolution, is equal to the direction and magnitude of the propeller thrust. The blades which normally project downward into the water flow ape usually mounted in a recessed rotating propeller hub which orbits about an axis normal to the hull.

Cycloidal propellers generally include an offset control mechanism, a power drive and gear reduction system, and a rotating propeller hub which includes the variable-pitch propeller blades. In existing cycloidal propellers, the offset control mechanism is on top of the drive system and consists of two orthogonal hydraulic servo motors that pivot a vertical control rod-end off its concentric axis with the rotating propeller, and levers the lower control rod-end in the rotating propeller hub, in a direction perpendicular to the direction of thrust and at a selected magnitude offset. This action, in turn, causes an offset ring in the lower rotating hub to continuously adjust the various blade bell-cranks and/or crank-type kinematics to cyclically vary each variable-pitch blade angle. The offset control mechanism, the mechanical kinematics blade-pitch linkage systems and the propeller hub are large, complex and mechanically inefficient.

A 134 hp thruster is transversely mounted in the bow for precise manoeuvring. Machinery control is exercised through an Integrated Platform Management System (IPMS) supplied by CAE of Canada and sited in the machinery control room. The digital IPMS monitors and controls the ship's entire hull electrical and mechanical systems as well as the propulsion, electrical distribution, steering, damage control and navigation system. A microprocessor-based semi-automatic manoeuvring system co-ordinates the movements of the cycloidal propellers. In addition the engines can be controlled from the wheelhouse or from a local position in the engine room.

Yangyang-class minesweeping is capable of complex-sensitive minesweeping, but the cost is high because it is said to cost 100 billion won. Initially, 8 or 10 vessels were considered for construction, but due to financial reasons, the construction was discontinued at 3 vessels. Later, in the 2010s, additional equipment for an equivalent minesweeper began to be considered, but as of 2019, it had not been realized.

The minesweeper acquisition program, once thought abandoned, was recently revived with news of additional ships being built. Republic of Korea Navy's 4th Yangyang-class minesweeper ROKS Namhae (MSH-575) recently launched in april 2020 by Kangnam Corporation. ROKS Namhae was launched 16 years after the last ship of her class, ROKS Haenam (MHS-573), was commissioned in 2005. Like almost all recent military acquisition, the launching ceremony was kept "low key" and the press embargo doesn't seem to have been lifted. The names of these minesweepers are taken from the names of counties and towns adjacent to a naval base.[4] For example, Yangyang is the name of Yangyang County, Gangwon Province.

ROKN's mine warfare fleet is currently composed of 1 Nampo-class minelayer, 1 Wonsan-class minelayer, 9 Ganggyeong-class minehunters, and 3 Yangyang-class minesweeper. This rather modest mine warfare fleet will continue to grow through acquisition of minesweeping helicopters, additional Nampo-class minelayers, additional Yangyang-class minesweepers, UUVs, and USVs.


 
Page last modified: 13-09-2021 14:44:21 ZULU