Jang Yeongsil-class submarine

KSS-III is a submarine acquisition program confirmed at the 16th Defense Acquisition Program Promotion Meeting in 2007. Batch-I was the , and Jang Yeongsil is the first vessel of Batch-II. The Jang Yeongsil class is a significantly improved successor to Dosan Ahn Changho class. It is equipped with a larger vertical launcher, capable of firing submarine-launched ballistic missiles (SLBMs), a penetrating periscope, an auxiliary propulsion system, and an independently developed lithium battery system. It is the third submarine in the world to be equipped with lithium-ion batteries, enabling it to remain submerged for up to three weeks without nuclear propulsion. On October 22, 2025, the Republic of Korea Navy and the Defense Acquisition Program Administration held a launching ceremony for the class, the first ship of the KSS-III Batch-II, at Hanwha Ocean's Geoje Shipyard in Geoje, South Gyeongsang Province. == Design ==

Compared to Batch-I, the Batch-II has a larger overall length and width due to its increased displacement. Batch-I had a total length of and a displacement of 3,000 tons, but Batch-2 was expanded to and a displacement of , and as a result, the number of vertical launch tubes increased from 6 to 10. This is the first submarine in the ROKN to be equipped with lithium batteries and an air-independent propulsion (AIP) system at the same time, which has extended its submerged time. The Batch-I, which was the first batch, used a propulsion system that combined lead-acid batteries and AIP, but the second batch used a propulsion system that combined lithium-ion batteries and AIP. Lead-acid batteries have low energy density, a short lifespan, and the risk of overheating or explosion, whereas lithium-ion batteries have a high energy density, more than twice that of existing lead-acid batteries, and a short charging time. This has improved underwater operation time and stealth, with a 160% increase in submerged range and 300% increase in submerged time compared to lead-acid batteries, enabling submerged operation for approximately three weeks. The operating range is , the submerged speed is , and the submerged depth is over . == Armaments ==

The weapon system has also been strengthened compared to the Dosan Ahn Chang-ho class. The vertical launch system (VLS), capable of carrying submarine-launched ballistic missiles (SLBMs), has been expanded from the original six cells to ten. The combat and sonar systems have also been enhanced compared to existing vessels, with enhanced information processing, target detection, and land-based target strike capabilities. The vessel is equipped with a curved array sonar developed using domestic technology for submarines. While existing cylindrical array sonar requires the submarine to change course to pinpoint the target, the curved array sonar has three times more detection elements than cylindrical sonar, enabling enhanced detection without the submarine having to change course. Like Batch-1, it features an anechoic coating and dual-elastic mount, and small fins attached to the center cap of the propeller, like wings, reduce noise. ==Ships in the class==

Future operators ; (3) Potential operators (4-12) — Competition with the TKMS Type 212CD ongoing under the Canadian Patrol Submarine Project. == See also ==