Ipchun-class minehunter

4-view diagram of Ipchun in 2014.
Class overview
Operators:	Menghe
Planned:	24
General characteristics (Ipchun, as built)
Type:	Minehunter
Displacement:	1,600 tons
Length:	67.9 m overall 61.8 m at waterline
Beam:	10 m
Draught:	3.3 m to keel
Propulsion:	2 × diesel engine, 1,200 kW each 2 Voith Schneider propellers
Speed:	15 knots
Range:	1,900 nautical miles (3,500 km) at 10 knots
Complement:	6 officers 43 enlisted crew
Sensors and processing systems:	Ŭ-101 minehunting sonar Ŭ-98 towed minehunting sonar
Electronic warfare & decoys:	1 × D-107 datalink 2 × Manhwagyŏng-H torpedo countermeasure
Armament:	1 × 2 35mm autocannon 2 × 1 12.7mm heavy machine gun

The Ipchun class are a group of oceangoing minehunters produced by the Onju Specialty Shipyard in Menghe. They are the first class of true minehunters built in Menghe; previously, the Menghean Navy relied on minesweepers which would tow wire sweeps through the minefield. Ipchun-class ships do carry remotely operated minesweeping boats for time-sensitive mine clearance operations, but the ships themselves are designed to operate on the edges of known minefields, hunting for individual mines with the help of hull-mounted and towed sonar equipment.

Design and development

The Menghean Navy issued a design requirement for a new class of oceangoing mine countermeasures ship in the mid-2000s. The design requirement called for a ship which could accompany amphibious battle groups in medium-range landing operations against Innominada, clearing mines along the transit route and ahead of the landing zone. During development, this ship class was known as Plan 754.

Previous Menghean oceangoing minesweeper classes used hulls made from low-magnetic steel. The Ipchun design would use a fiberglass composite hull for even greater magnetic signature reduction, and would feature improved shock resistance to withstand nearby mine detonations. These features posed a technical challenge to Menghean shipyards, few of which had experience working with composite materials. The initial contract for 12 ships was awarded to the Onju Specialty Shipyard, which had produced fiberglas-hulled coastal minesweepers in the past. Later, the Ministry of National Defense financed the construction of a new shipyard in Pungsu for the purpose of speeding up minesweeper production.

Apart from the new hull materials, the Ipchun-class minehunters use rafted machinery mounts to dampen vibration from the diesel engines, which are themselves specially-engineered low-noise and low-magnetic-signature models. The diesel engines are connected to generators, which in turn power two electrically-driven Voith Schneider Propellers aft and two electrically-driven tunnel thrusters forward. This propulsion system further reduces engine noise, protecting the vessel from acoustically activated mines, and allows for more precise maneuvers, useful when holding position while operating ROVs and navigating through minefields.

As a final defense against homing mines, all ships in the class are fitted with two Manhwagyŏng torpedo countermeasure launchers, one on each side. Defensive anti-air and anti-surface armament consists of a twin 35mm gun turret forward and two 12.7mm heavy machine guns on the superstructure, the latter added during construction in response to the threat of Innominadan light craft. Because the Ipchun-class ships have neither air-search nor fire-control radar, the 35mm turret relies on manual spotting and electro-optical fire control, using a visual and infrared camera station with a laser rangefinder. This weapon system is able to engage aircraft, helicopters, and missiles, but with less accuracy than a radar-aimed gun system.

Minehunting equipment

Apart from a single minehunting sonar mounted on the hull, all mine countermeasure equipment is fitted on the unusually spacious quarterdeck, one of the distinct features of the Ipchun class and the driving cause of its relatively large size compared with other minehunters. As of 2020, most ships in the class are equipped with the following equipment, though the mountings allow different payload combinations to be fitted.

• Two "Ori" remote-operated surface boats
• Three or more "SeaFox" remote-operated underwater vehicles
• One Ŭ-98 towed minehunting sonar

"Ori" remote-operated boat

These diesel-powered vessels measure 8.2 meters long by 2.6 meters wide, and are made of sturdy fiberglass. They have a small onboard cabin for manual piloting, but are designed for remote operation in hazardous areas. Each one can be fitted with either two magnetic-cable sweeps, a single SeaFox ROV, or a single towed minehunting sonar. A single 90-ton-capacity crane aft of the funnel lifts these boats into the water and recovers them after a mine clearance operation is finished.

In the minehunting role, one "Ori" scouts ahead with its minehunting sonar, and another accompanies it with a SeaFox ROV to disable any mines it encounters. This is the safest approach, as it allows the Ipchun mothership to remain well outside the suspected boundaries of the minefield, but also the most time-consuming.

Alternatively, one or both Ori-class boats can be fitted with sweeping equipment and dispatched directly through the minefield. In addition to their electrically-charged towed cables, these boats are also reportedly fitted with undersea speakers which can mimic the acoustic signature of a minesweeper, warship, or cargo ship, providing an additional means of triggering seabed mines. The small, light, and sturdy boat is able to withstand nearby mine detonations, and remote piloting prevents loss of life if it is sunk. This method, while riskier, allows for faster mine clearance, and would be employed in time-sensitive operations.

SeaFox ROV

The SeaFox ROV was introduced in 2013. It is a tombstone-shaped, plastic-bodied submersible measuring roughly 3.3 m long, 1.2 m wide, and 0.7 m tall. It is fitted with a camera, spotlight, and short-range sonar, and controlled by means of an umbilical cable linking it to the minehunter or a remote-operated boat. The original SeaFox 1 model has three methods for disabling mines: a high-strength wire cutter for breaking anchor cables, a remote arm with a clamp for planting small explosive charges, and a remote arm with a drill for disabling sensors.

The SeaFox 2 model, unveiled at a defense expo in 2018, has mounting equipment on the right side to allow the fitting of an underwater assault rifle with special cavitating ammunition. The trigger is actuated by a waterproof solenoid piston. While theoretically capable of disabling or triggering mines, this weapon would most likely be used to engage frogmen, trained marine animals, and hostile ROVs, and would be fitted to the SeaFox 2 when defending friendly minefields.

Ŭ-98 minehunting sonar

The Ŭ-98 is a towed system resembling a torpedo or cruise missile. It is 4.8 meters long with a diameter of roughly 90 centimeters and a wingspan of roughly 3 meters. It is fitted with side-facing sonar arrays to identify mines lying on the seabed, and also carries a forward-facing camera and spotlight to help the operator visually identify suspected mines. While it lacks its own means of propulsion, the Ŭ-98 can be trimmed up and down to maintain the desired distance above the seabed, and can be steered port and starboard to investigate areas to the side of the mothership.

Naming

Unlike previous Menghean minesweepers, which were only given hull numbers, the Ipchun class were given names as well. Specifically, they are named for the solar terms, part of the traditional Menghean calendar. Although early press releases mentioned only twelve ships in the contract, the choice of the solar terms for ship nomenclature implied a production run of as many as twenty-four ships, and additional orders unveiled in 2019 lent further credence to this speculation.