On October 22, 2025, South Korea took a significant step in strengthening its naval capabilities with the launch of ROKS Jang Yeong-sil (SS-087), the first of the KSS-III Batch-II submarines. Built by Hanwha Ocean at its Geoje shipyard, this 3,600-ton vessel represents a significant leap in indigenous submarine technology, most notably as the world’s first diesel-electric submarine powered by lithium-ion batteries combined with a 10-cell vertical launch system.
Named after the celebrated 15th-century Korean scientist Jang Yeong-sil, the submarine is set to undergo comprehensive testing and trials before entering active service with the Republic of Korea Navy in 2027.
A New Class of Submarine: Key Advancements
The Jang Yeong-sil-class builds upon the foundation of the earlier Dosan Ahn Changho-class (Batch-I) but introduces several critical enhancements:
- Lithium-Ion Battery System: Provided by Samsung SDI, these batteries replace traditional lead-acid cells, offering higher power density, faster recharging, and extended underwater endurance, enabling submerged operations of more than 20 days.
- Increased Strike Capability: The submarine is equipped with ten Korean Vertical Launch System (K-VLS) cells, up from six in the previous class—capable of launching the Hyunmoo 4-4 submarine-launched ballistic missile (SLBM) and future cruise missiles.
- Advanced Stealth and Sensors: Enhanced acoustic damping, anechoic coating, and propeller design reduce noise signature, while upgraded sonar arrays and the Naval Shield combat management system improve detection and tracking capabilities.
Strategic Significance and Indigenous Development
The KSS-III Batch-II program underscores South Korea’s growing defense autonomy. With over 80% of components sourced domestically, up from 76% in Batch-I, the program solidifies the country’s position as the eighth nation capable of independently designing and building submarines exceeding 3,000 tons.
“This launch represents not only a tactical advancement but a strategic milestone in our national defense sovereignty,” a Hanwha Ocean representative stated during the ceremony.
Program Timeline and Future Projections
The Jang Yeong-sil is the first of three Batch-II submarines planned, with the second and third vessels scheduled for delivery in 2028 and 2031. Each submarine is expected to serve for approximately 20 years, with maintenance cycles adapted to support the new lithium-ion propulsion systems.
The broader KSS program, which includes 27 submarines across three classes, continues to evolve. A Batch-III design is already anticipated for the early 2030s, with plans to integrate unmanned undersea vehicles and advanced data-link systems such as Link 22.
Regional Impact and Naval Doctrine
With its extended endurance, advanced missile capability, and quiet operation, the Jang Yeong-sil-class enhances South Korea’s capacity for sustained maritime patrols, precision strike operations, and underwater deterrence. It also reinforces the Navy’s shift toward a more expeditionary, self-reliant submarine force capable of operating independently in contested waters.
