Jang Yeongsil-class submarine

The KSS-III Batch-II (Korean Submarine-III Batch-II; Korean: 한국형 잠수함-III 배치-II; Hanja: 韓國型潛水艦-III 배치-II), officially called Jang Yeongsil class (Korean: 장영실급 잠수함; Hanja: 蔣英實級潛水艦; RR: Jang-yeongsil-geup Jamsuham) is a series of diesel-electric attack and ballistic missile submarines currently being built for the Republic of Korea Navy (ROKN), jointly by Hanwha Ocean.

Jang Yeongsil
Class overview
Name	Jang Yeongsil class
Builders	Hanwha Ocean
Operators	Republic of Korea Navy
Preceded by	Dosan Ahn Changho class
Built	2021–present
General characteristics
Type	Attack submarine with ballistic missile launching capabilities
Displacement	3,600 t (3,500 long tons) (surfaced)[1][2] 4,000 t (3,900 long tons) (submerged)
Length	89.3 m (293 ft 0 in)[3][4]
Beam	9.7 m (31 ft 10 in)

The KSS-III Batch-II initiative, which involves domestically building three new submarines, each 89 m (292 ft 0 in) long and displacing 3,600 tonnes (3,500 long tons), was implemented from 2016 to 2029 with an investment of approximately KRW 3.41 trillion.^[5]

History

KSS-III is a 3,000-tonne (3,000-long-ton) submarine acquisition program confirmed at the 16th Defense Acquisition Program Promotion Meeting in 2007. Batch-I was the Dosan Ahn Changho class, 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.^[6] 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.^[7]

It was named after Jang Yeongsil, a Silhak scholar who led science and technology in the Joseon Dynasty, with the symbolic meaning of protecting the country with the excellent technology of South Korea's defense industry. Jang Yeongsil is considered the greatest scientist of the Joseon Dynasty who created the armillary sphere and the water clock Borugak Jagyeongnu (혼천의), and he is the first scientist to be included in the name of a submarine.^[7]

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.^[8]

Design

Graphic image of Jang Yeongsil class

Compared to Batch-I, the Batch-II has a larger overall length and width due to its increased displacement.^{[citation needed]} Batch-I had a total length of 83.5 m (273 ft 11 in) and a displacement of 3,000 tons, but Batch-2 was expanded to 89.4 m (293 ft 4 in) and a displacement of 3,600 t (3,500 long tons), and as a result, the number of vertical launch tubes increased from 6 to 10.^[9][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.^[11] 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 7,000 nautical miles (13,000 km; 8,100 mi), the submerged speed is 20 knots (37 km/h; 23 mph), and the submerged depth is over 400 m (1,300 ft).^[10]

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.^[10]

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.^[9]

Ships in the class

Name	Pennant Number	Builder	Laid Down	Launched	Commissioned	Status
ROKS Jang Yeong-sil	SS-087[12]	Hanwha Ocean	30 March 2023[13]	22 October 2025[14]	Scheduled for 2026[12]	Launched[14]
TBA[15]		Hanwha Ocean	12 July 2024[15]		Scheduled for 2028[15]	Under construction[15]
TBA[16]		Hanwha Ocean	30 Oct 2024[16]		Scheduled for 2031[16]	Under construction[16]

Operators

Future operators

South Korea (3)

See also

• List of active Republic of Korea Navy ships