Horizontal-launch torpedoes and vertical-launch SLBMs aboard

3,600-ton Pyeongtaek: 'You could get lost walking alone'

The Jangbogo-III Batch-II second vessel Seo-hui moored at Hanwha Ocean's special-vessel quay [Hanwha Ocean]
The Jangbogo-III Batch-II second vessel Seo-hui moored at Hanwha Ocean's special-vessel quay [Hanwha Ocean]

The interior of the Seo-hui — the second vessel of the Jangbogo-III Batch-II class, set for a launch ceremony in the second half of this year — was a hive of activity as workers pressed ahead with final construction. Climbing down a vertical ladder, a reporter found interior finishing panels still wrapped in plastic sheeting, narrow corridors, and Hanwha employees moving briskly through the passageways.

Displacing roughly 3,600 tons and stretching about 89 meters — larger in profile than the Dosan Ahn Chang-ho class — the submarine packs its interior tightly with everything essential: crew operating spaces and bunks, horizontal-launch torpedoes, and vertically launched submarine-launched ballistic missiles (SLBMs). The galley and mess hall at least claimed a generous share of the space, and the toilet fixtures were reassuringly full-sized, much like those found ashore.

The Jangbogo-III Batch-II program saw its first vessel, the Jang Yeong-sil, launched in late October last year. Compared with the Dosan Ahn Chang-ho class — the most capable submarines in the South Korean Navy — the Batch-II boats represent across-the-board improvements in detection, strike capability, stealth and survivability.

Particularly notable are upgrades to the combat management system — the submarine's brain — and the sonar suite, its eyes and ears, which together sharpen information processing, target detection and the ability to strike land targets. The domestic content rate reaches 80 percent, yet the platform can also be tailored to a buyer's specifications through customized localization.

The Seo-hui was built as a hybrid submarine combining an air-independent propulsion (AIP) system developed by Hanwha Ocean with a lithium-ion battery system supplied by Hanwha Aerospace. The pairing of AIP with lithium-ion batteries is a world first, giving the vessel the longest submerged endurance of any diesel-electric submarine in the world.

The Ulsan-class Batch-III fifth vessel Pyeongtaek after launch at Hanwha Ocean's special-vessel construction zone [Hanwha Ocean]
The Ulsan-class Batch-III fifth vessel Pyeongtaek after launch at Hanwha Ocean's special-vessel construction zone [Hanwha Ocean]

The next vessel visited, the Pyeongtaek — fifth ship of the Ulsan-class Batch-III — was deep into systems and equipment operational testing. Cylindrical ventilation ducts ran along the ceiling of its passageways to distribute air-conditioning throughout the ship. The guide's warning that "you could get lost walking around alone" felt entirely credible aboard the massive 3,600-ton frigate, which stretches roughly 130 meters in length, 15 meters in beam and 40 meters in height. The ship carries a five-inch naval gun, the Korean Vertical Launch System (KVLS), surface-to-air missiles, surface-to-surface missiles, tactical land-attack missiles and long-range anti-submarine torpedoes. Its integrated sensor mast (ISM) is fitted with infrared search-and-track equipment alongside a domestically developed multi-function phased-array radar (MFR).

The Pyeongtaek was launched in mid-August and is scheduled to begin harbor acceptance trials next month. The sixth vessel is on the slipway, with a launch targeted for early next year. After their respective launch ceremonies, the Pyeongtaek is slated for delivery to the Navy in December 2027 and the sixth vessel in around June 2028, after which both will undergo operational testing before being commissioned.

During the Pyeongtaek's construction, Hanwha Ocean enlarged the hull blocks loaded onto the slipway, cutting the number of lifts by roughly half and trimming the build schedule by one to two months. The company plans to apply the same technique to the first and second vessels of the Ulsan-class Batch-IV, as well as to the Korean next-generation destroyer (KDDX), whose timely delivery is a key operational priority.

The No. 4 special-vessel factory at Hanwha Ocean's Geoje shipyard, where the Seo-hui and the Pyeongtaek were berthed, operates an AI-based smart integrated control system covering more than 12,000 square meters. Smart cranes equipped with automatic obstacle avoidance, anti-sway and intelligent load-alignment functions have been installed to prevent accidents and maximize factory efficiency. In the pipe-fabrication shop, cutting and bending processes have been fully automated.

Kim Gyu-baek, executive vice president of Hanwha Ocean's special-vessel division, said the company would "continue to secure an overwhelming edge in defense solutions through large-scale investment and research and development, carrying on the tradition of a leading warship builder." He added that Hanwha Ocean would "proactively expand production facilities and strengthen technological competitiveness to keep pace with the rapidly changing maritime security environment."


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