Inside the Seo Hui: A look at Korea's newest submarine

Hanwha Ocean opened the Seo Hui, a 3,600-ton submarine under construction at its Geoje shipyard in South Gyeongsang Province, to reporters on Tuesday. The second Jangbogo-III Batch-II submarine is tentatively set for launch in November and delivery in December 2027. The vessel has upgraded combat and sonar systems, a roughly 80 percent localization rate and a propulsion setup combining air-independent propulsion with lithium-ion batteries. Crew living conditions have also improved, with each of the about 50 crew members assigned a bed.

The Seo Hui is about 89 meters long and is larger than the Dosan Ahn Chang-ho-class submarines of Batch-I.

Its torpedo room has more horizontal and vertical launch tubes than the Dosan Ahn Chang-ho-class submarines, allowing it to carry torpedoes, guided missiles and submarine-launched ballistic missiles.

Hanwha Ocean said the Seo Hui is the world’s first submarine to combine its air-independent propulsion system with lithium-ion batteries and claimed it has the longest underwater endurance of any diesel-electric submarine.

Hanwha Ocean has built 17 of the 24 submarines ordered by the Navy since winning an order for the first Jangbogo-I submarine in 1983.

The nearby Pyeongtaek, the fifth Ulsan-class Batch-III frigate, launched in August and is scheduled for dockside trials in mid-October before sea trials through next August.

Published Sep 20, 2026 2:00 pm KST

Hanwha Ocean's sub combines 2 propulsion technologies, extends underwater endurance

The Seo Hui, the second Jangbogo-III Batch-II submarine, is moored at Hanwha Ocean’s naval ship quay in Geoje, South Gyeongsang Province. Courtesy of Hanwha Ocean

GEOJE, South Gyeongsang Province — Wearing gloves, reporters ducked beneath a canvas cover and descended a ladder into the Seo Hui, a 3,600-ton submarine under construction at Hanwha Ocean’s Geoje shipyard.

At the bottom was a narrow passage, barely wide enough for two adults. Pipes and equipment remained exposed, while stickers reading “painting inspection completed” showed that work was still underway.

Hanwha Ocean opened the interior of the Seo Hui, the second Jangbogo-III Batch-II submarine, to the media for the first time Tuesday. Its launch ceremony is tentatively planned for November, although the timing could change depending on the Navy’s schedule. The contract stipulates that delivery is set for December 2027.

Measuring about 89 meters long, the Seo Hui is larger than the Dosan Ahn Chang-ho-class submarines of Batch-I. Its combat management and sonar systems have been upgraded to improve data processing, target detection and land attack capabilities. Its overall localization rate is about 80 percent.

In the torpedo room in the bow, horizontal launch tubes were arranged on both sides of a central aisle. The Seo Hui has more horizontal and vertical launch tubes than the Dosan Ahn Chang-ho-class submarines, allowing it to carry torpedoes, guided missiles and submarine-launched ballistic missiles.

In the Combat Command Center, multifunction consoles bring together information collected by the submarine’s sonar and other sensors, allowing the crew to track nearby vessels and operate the weapons systems.

Another major change is its propulsion system, which combines an air-independent propulsion system developed by Hanwha Ocean with lithium-ion batteries supplied by Hanwha Aerospace.

The Pyeongtaek, the fifth Ulsan-class Batch-III frigate, is prepared for launch at Hanwha Ocean’s naval shipbuilding facility in Geoje, South Gyeongsang Province. Courtesy of Hanwha Ocean

Diesel-electric submarines normally run their propellers on battery power. To recharge, they must raise a snorkel above the water and draw in air to operate the diesel generators, increasing their risk of detection.

The Air independent propulsion system developed by Hanwha Ocean generates power underwater without outside air, while lithium-ion batteries offer greater efficiency than conventional lead-acid batteries. Hanwha Ocean said the Seo Hui is the world’s first submarine to combine the two technologies and has the longest underwater endurance of any diesel-electric submarine.

The larger hull has also changed living conditions for its approximately 50 crew members. On earlier submarines, some sailors had to share bunks in shifts. Every crew member aboard the Seo Hui will have an assigned bed.

Officers and other crew members have separate sleeping quarters. Bunk beds still filled many of the rooms, but the submarine also has larger washroom areas and separate showers.

“On the earlier Jangbogo and Son Won-il-class submarines, crew members had to take turns using the beds,” said Kim Hak-soo, a general manager in Hanwha Ocean’s Naval Ship PM Department, who guided reporters through the vessel. “Here, each crew member can use their own bed, so living conditions have improved significantly.”

Reporters then moved to a submarine construction hall, where massive cylindrical hull sections for the third Jangbogo-III Batch-II submarine were lined up. Equipment and piping are installed inside each section before the sections are aligned, welded together and formed into a complete hull.

Since winning an order for the first Jangbogo-I submarine in 1983, Hanwha Ocean has built 17 of the 24 submarines ordered by the Navy. It is building all three Batch-II submarines.

Nearby, the company’s 12,000-square-meter fourth special ship plant, completed in October last year, was being used to assemble blocks for both submarines and surface ships. Indoor production allows welding to continue regardless of rain or wind while maintaining consistent quality, the company said.

A smart logistics robot transports materials at Hanwha Ocean’s Naval Ship Plant 4 in Geoje, South Gyeongsang Province. Courtesy of Hanwha Ocean

At an automated storage facility, an autonomous mobile robot carried materials requested by workers to their workstations. Barcodes track the materials as they enter and leave storage, while smart cranes are designed to avoid obstacles and stabilize suspended loads.

Also moored at the shipyard was the Pyeongtaek, the fifth Ulsan-class Batch-III frigate, which launched in August. The 4,100-ton frigate is undergoing checks of its onboard equipment and systems.

“Dockside trials are scheduled to begin in mid-October, followed by sea trials through next August,” said Song Seung-hyun, an associate on Hanwha Ocean’s Surface Vessel PM Team. “The frigate is due to be delivered to the Navy in December 2027.”

韩华海洋公司周二在其位于庆尚南道巨济造船厂向记者展示了正在建造中的3600吨级潜艇“徐熙”号。这艘潜艇是第二艘长保皋-III型二批次潜艇，暂定于2027年11月下水，12月交付。该潜艇升级了作战和声呐系统，定位率达到约80%，并采用了不依赖空气推进系统与锂离子电池相结合的动力装置。艇员的生活条件也得到了改善，约50名艇员每人都拥有自己的床位。

“徐辉”号潜艇长约 89 米，比第一批次的“岛山安昌浩”级潜艇要大。

它的鱼雷舱拥有比岛山安昌浩级潜艇更多的水平和垂直发射管，使其能够携带鱼雷、导弹和潜射弹道导弹。

韩华海洋公司表示，“徐辉”号是世界上第一艘将不依赖空气推进系统与锂离子电池相结合的潜艇，并声称它是所有柴电潜艇中水下续航时间最长的。

自 1983 年赢得第一艘长保皋-I 型潜艇的订单以来，韩华海洋已经建造了海军订购的 24 艘潜艇中的 17 艘。

附近的平泽号是蔚山级第三批次的第五艘护卫舰，于8月下水，计划于10月中旬进行码头试验，然后一直到明年8月进行海上试验。

发布于2026年9月20日下午2:00（韩国标准时间）

韩华海洋的潜艇结合了两种推进技术，延长了水下续航时间。

“徐熙”号是第二艘长保皋-III型二批次潜艇，停泊在庆尚南道巨济市韩华海洋公司的海军舰艇码头。图片由韩华海洋公司提供。

庆尚南道巨济——记者们戴着手套，从帆布罩下钻过梯子，进入了“徐熙”号潜艇。这艘3600吨级的潜艇正在韩华海洋巨济造船厂建造中。

底部是一条狭窄的通道，仅够两个成年人勉强通过。管道和设备裸露在外，而“油漆检查完成”的标签表明施工仍在进行中。

韩华海洋公司周二首次向媒体开放了第二艘长保皋-III型二批次潜艇“徐熙”号的内部结构。该潜艇的下水仪式暂定于11月举行，但具体时间可能会根据海军的计划而有所调整。合同规定，该潜艇将于2027年12月交付。

“徐辉”号潜艇全长约89米，比第一批次的“岛山安昌浩”级潜艇更大。其作战管理系统和声呐系统均已升级，提高了数据处理能力、目标探测能力和对陆攻击能力。其整体定位准确率约为80%。

艏部鱼雷舱内，水平发射管沿中央通道两侧排列。“徐熙”号的水平和垂直发射管数量均多于“岛山”级安昌浩级潜艇，使其能够携带鱼雷、导弹和潜射弹道导弹。

在作战指挥中心，多功能控制台将潜艇声呐和其他传感器收集的信息集中在一起，使船员能够跟踪附近的船只并操作武器系统。

另一个重大变化是其推进系统，该系统结合了韩华海洋开发的空气非依赖型推进系统和韩华航空航天提供的锂离子电池。

“平泽”号是蔚山级第三批次的第五艘护卫舰，目前正在韩国庆尚南道巨济市韩华海洋造船厂进行下水前的准备工作。图片由韩华海洋提供。

柴电潜艇通常依靠电池驱动螺旋桨。充电时，它们必须将通气管升出水面，吸入空气来启动柴油发电机，这增加了它们被发现的风险。

韩华海洋公司开发的无空气推进系统（Air Independent Progressive System）无需外部空气即可在水下产生动力，而锂离子电池的效率也高于传统的铅酸电池。韩华海洋公司表示，“徐熙”号是世界上首艘结合了这两种技术的潜艇，也是目前所有柴电潜艇中水下续航时间最长的。

更大的船体也改变了船上约50名船员的生活条件。在早期的潜艇上，一些水兵需要轮流共用铺位。而“徐熙”号上的每位船员都将拥有固定的床位。

军官和其他船员有独立的睡眠区。虽然许多房间仍然摆放着上下铺​​，但潜艇也设有更大的盥洗室和独立的淋浴间。

“在早期的长保皋级和孙元日级潜艇上，艇员们必须轮流使用床铺，”韩华海洋公司海军舰艇项目管理部门总经理金学洙（音译）带领记者参观潜艇时说道，“而在这里，每位艇员都可以使用自己的床铺，因此生活条件得到了显著改善。”

随后，记者们来到潜艇建造车间，那里整齐地排列着第三艘“长保皋-III”型二批次潜艇的大型圆柱形艇体段。在各艇体段对齐、焊接并组装成完整艇体之前，所有设备和管道都已安装在艇体段内部。

自1983年赢得首艘长保皋-I型潜艇订单以来，韩华海洋已建造了海军订购的24艘潜艇中的17艘。该公司正在建造全部三艘第二批次潜艇。

附近，该公司占地12000平方米的第四座特种船舶工厂于去年10月竣工，目前正用于组装潜艇和水面舰艇的模块。该公司表示，室内生产使得焊接作业不受风雨影响，能够持续进行并保持产品质量的稳定性。

在庆尚南道巨济市韩华海洋公司第四海军船舶制造厂，一台智能物流机器人正在运输物料。图片由韩华海洋公司提供。

在一个自动化仓库中，一台自主移动机器人将工人所需的物料运送到他们的工作站。条形码追踪物料进出仓库的过程，而智能起重机则被设计成可以避开障碍物并稳定悬挂的货物。

同时停泊在船厂的还有第五艘蔚山级第三批次护卫舰“平泽”号，该舰于8月下水。这艘4100吨级的护卫舰正在接受舰载设备和系统的检查。

韩华海洋水面舰艇项目管理团队的宋承铉表示：“码头试验计划于10月中旬开始，随后将进行海上试验，直至明年8月。这艘护卫舰预计将于2027年12月交付海军。”