The Republic of Korea Navy (ROKN) and South Korea’s Defense Acquisition Program Administration (DAPA) held a launching ceremony for the fifth overall KSS-III diesel-electric submarine at Hanwha Ocean's Okpo shipyard in Geoje on Tuesday, November 3.
The future ROKS Seo Hui is also the second Batch-II boat under the KSS-III class, which is also known as the Dosan Ahn Changho-class.
The submarine is approximately 89 metres long and has a displacement of approximately 3,600 tonnes. Delivery to the ROKN is scheduled for 2028 following sea trials.
The future Seo Hui will enter operational service after an operational work-up period.
The vessel carries 70 equipment types developed domestically, 12 more than on the KSS-III Batch-I boats.
The ROKN and DAPA said the higher domestic content would help ensure dependable and prompt follow-on logistical support. They also expect it to improve the export competitiveness of South Korean submarines.
The locally developed equipment includes a lithium battery system. According to the two organisations, the batteries extend both submerged endurance and the time the submarine can operate at maximum speed.
Upgrades to the combat and sonar systems are intended to help the submarine identify multiple targets at long range. Its larger hull meanwhile provides greater capacity for weapons and onboard equipment than on the Batch-I boats.
Other features include noise-reduction technology, auxiliary propulsion to preserve manoeuvrability if the main propulsion system fails, and a hull-penetrating periscope for observing directly when electro-optical sensors are impaired.
The submarine is named after Seo Hui, a statesman of the Goryeo Dynasty.
Steel cutting for Seo Hui took place on December 30, 2021, and her keel was laid in 2024. She follows the lead Batch-II boat, the future ROKS Jang Yeong-sil, which was launched at Geoje on October 22, 2025 and is due for delivery at the end of 2027.
The third KSS-III Batch-II submarine is scheduled for delivery in 2031.
