The Republic of Korea Navy held a launching ceremony for Seo Hui, the second Jang Bogo(KSS)-III Batch-II submarine, at Hanwha Ocean’s shipyard in Geoje on November 3. The submarine features 70 types of domestically developed equipment to support follow-on logistics and strengthen the foundation for defense exports.
ROK Navy and Defense Acquisition Program Administration(DAPA) joint press release translated by Naval News
The Republic of Korea (ROK) Navy and the Defense Acquisition Program Administration (DAPA) held a launching ceremony for ROKS Seo Hui (SS-088), the second Jang Bogo(KSS)-III Batch-II submarine, at Hanwha Ocean’s Okpo shipyard in Geoje on the afternoon of November 3.
ROKS Seo Hui is the second vessel in the Batch-II program, following the lead submarine, ROKS Jang Yeong-sil (SS-087).
The Jang Bogo-III Batch-I program comprises three 3,000-ton-class submarines: Dosan Ahn Chang-ho (SS-083), Ahn Mu (SS-085) and Shin Chae-ho (SS-086). The 3,600-ton-class Batch-II program includes the lead submarine Jang Yeong-sil (SS-087) and the second vessel, Seo Hui (SS-088).
ROK Navy submarines are named after respected figures who contributed to the development of military power, maritime power, and science and technology, or who fought against foreign forces and participated in the independence movement. The Navy named the second Jang Bogo-III Batch-II submarine after Seo Hui, a distinguished statesman of the Goryeo Dynasty, recognizing that his outstanding military and diplomatic achievements and spirit of overcoming national crises reflect the stature of a state-of-the-art submarine that serves as a key asset for defending the nation’s waters.
Indigenously designed and built in South Korea, ROKS Seo Hui was launched following the award of a construction contract in 2021, a steel-cutting ceremony later that year, and a keel-laying ceremony in 2024.
The steel-cutting ceremony marks the first stage of ship construction, while the keel-laying ceremony marks the placement of the vessel’s first block on the building berth.
Approximately 200 guests attended the launching ceremony, with National Assembly Speaker Cho Jung-sik serving as the guest of honor. Attendees included senior representatives from government agencies, the National Assembly, the Ministry of National Defense, the Navy and DAPA, as well as defense industry officials.
The ceremony included national honors, a report on the program’s progress, the formal announcement of the vessel’s name, commemorative remarks, awards recognizing contributions to the program, congratulatory speeches, and the launch and safe-voyage ceremonies.
during the launch ceremony for ROKS Seo Hui (ROK Navy Photo)
In accordance with naval tradition, Cho Mi-seon, the wife of the National Assembly Speaker, cut the launching line attached to the submarine. The act symbolizes bringing the newly built vessel to life, much like cutting a newborn’s umbilical cord. The Speaker, his wife and other distinguished guests then cut a five-colored ribbon, releasing a champagne bottle to break against the hull in a ceremony wishing the submarine safe voyages.
ROKS Seo Hui (SS-088)
The Navy’s second 3,600-ton-class submarine, ROKS Seo Hui is a world-class diesel submarine and a key strategic asset for deterring maritime security threats around the Korean Peninsula and maintaining a robust strategic response posture in a contingency.
Incorporating the latest shipbuilding technologies, ROKS Seo Hui offers enhanced detection and strike capabilities, stealth and survivability compared with the Jang Bogo-III Batch-I Dosan Ahn Chang-ho-class submarines.
With a displacement of approximately 3,600 tons and a length of approximately 89 meters, ROKS Seo Hui has a larger hull than the Dosan Ahn Chang-ho class, providing ample capacity to accommodate a range of weapons and onboard equipment.
Upgrades to the combat system and sonar suite, which serve as the submarine’s brain and its eyes and ears, respectively, have improved its ability to identify multiple targets at long range and engage them with precision.
The submarine is also equipped with a domestically developed lithium battery system whose safety has been validated. The system extends submerged endurance and the duration of operations at maximum speed, further enhancing operational capability. Its reliability has been established through multiple safety features, validation at a dedicated land-based test facility, and safety assessments.
Advanced noise-reduction technologies minimize onboard noise and vibration, providing a high degree of stealth. Survivability has also been enhanced through an auxiliary propulsion system that preserves maneuverability in the event of a main propulsion failure, and a hull-penetrating periscope that enables direct observation if the electro-optical sensors’ functionality is impaired.
Compared with the Dosan Ahn Chang-ho class, an additional 12 types of equipment, including the lithium battery system, have been developed domestically, bringing the total aboard ROKS Seo Hui to 70. This is expected to ensure reliable and timely follow-on logistics support while further strengthening the export competitiveness of South Korean submarines.
ROKS Seo Hui is a world-class diesel submarine that brings together cutting-edge technologies and represents a significant achievement demonstrating the excellence of South Korea’s submarine design and construction capabilities. Building on the increased use of domestically developed equipment, it is expected to make a major contribution not only to strengthening the Navy’s capabilities, but also to establishing an advanced defense-industrial base and supporting submarine exports.
Lee Sang-woo, head of DAPA’s Nuclear-Powered Submarine Program Group
ROKS Seo Hui is a state-of-the-art national strategic asset capable of responding effectively to security threats through its powerful underwater warfare capabilities. We will continue to build naval capabilities based on advanced science and technology and fulfill our assigned missions as an elite Navy dedicated to protecting the people.
Rear Adm. Lee Gu-seong, head of the Planning and Management Staff at ROK Navy Headquarters
Following sea trials, ROKS Seo Hui is scheduled to be delivered to the Navy in 2028. It will subsequently enter operational service after completing the operational work-up process.
