The Republic of Korea Navy (ROKN) is planning on nine boats to make up its new Dosan Ahn Chang-ho-class attack submarine. The four boats - SS-083, SS-085, SS-086, and SS-087 - are being constructed through the efforts of Daewoo Shipbuilding & Marine Engineering (DSME) and Hyundai Heavy Industries (HHI). Building began in 2016 and continues as of this writing (2020).
The lead-ship of the class is ROKS Dosan Ahn Chang-ho (SS-083) which was built by DSME and laid down on May 17th, 2016. She was launched to sea on September 14th, 2018 and remains in active testing (2020). The vessel will be followed by ROKS Son Byong-hi (SS-085), ROKS Yi Dong-nyeong (SS-086), and ROKS Lee Bong-chang (SS-087). The former two are under construction with the latter planned. ROKS Dosan Ahn Chang-ho is expected to be commissioned sometime in 2020.
The class is the culmination of an initiative by the South Korean navy service to produce some twenty-seven attack boats over the course of 35 years beginning in the mid-1990s. With each successive design, more and more locally-sourced technology solutions are being implemented to make a more wholly South Korean product. The boats are also the largest ever undertaken by local industry making them a point of pride for the nation.
As designed, the class has a surfaced displacement of 3,358 tons and a submerged displacement of 3,705 tons. Dimensions include a running length of 83.5 meters, a beam of 9.6 meters, and a draught of 7.62 meters. Power is a diesel-electric arrangement involving 4 x Bumhan Industry PH1 PEM fuel cell systems developing 150 kW each driving a single, low-noise propeller at the rear in typical fashion. Acoustic dampening is used where possible to maintain stealthiness for the boat.
Performance figures include a maximum underwater speed of 20 knots and a top-side speed of 12 knots. Range is 10,000 nautical miles which will help the service maintain protection of the vast South Korean coastline.
The boat's profile is conventional with a blunt, rounded nose, tubular hull, and tapered aft section. the hull sides are noticeably bulged and the conning tower sits ahead of midships. The tower is home to the dive planes as well as the required collection of periscopes, sensors, and communications masts. The tail section of the boat incorporates the multi-bladed propeller unit as well as a cruciform tailplane arrangement.
Aboard is a complement of fifty personnel - making for one relatively compact attack submarine.
Armament includes 6 x 533mm bow-facing torpedo tubes supporting the "Tiger Shark" torpedo fasmily as well as the submarine-launched "Harpoon" anti-ship missile. Beyond this is are six Vertical Launching Systems (VLSs) embedded aft of the conning tower and these house land-attack cruise missiles as well as ballistic missiles as needed.
The series is being constructed across two distinct "batches" known simply as "Batch-I" and "Batch-II". ROKS Dosan Ahn Chang-ho is covered by the former while the remaining three boats are expected to include several improvements to broaden their tactical capabilities - namely in ballistic missile defense and anti-submarine systems to counter the North Korean threat. The result will be a lengthening of the hull by six meters as well as an increase to the VLS cell count from six to ten tubes as well as greater implementation of South Korean technology.