Acoustic Coating for Stealth Applied from Dosan Ahn Changho Submarine [Yang Nakgyu's Defence Club]

On-site Exploration at Hanwha Ocean's Okpo Shipyard
Building the Largest Number of Submarines in Korea: 23 Vessels

The South Korean Navy first began developing submarines in 1984. The development started with the small-scale Dolgorae-class submarine in 1984, and by the late 1980s, the Jangbogo-class (3,000-ton class) was introduced. Since then, Hanwha Ocean has secured orders for the largest number of submarines in South Korea, totaling 23 vessels (9 units of the 209 class, 3 units of the 214 class, 5 units of the 3,000-ton class, and 6 export submarines) since winning the contract for the first ship of the Jangbogo-I project, the "Jangbogo," in 1987. Out of these, 17 submarines have been successfully delivered, and 6 are currently under construction.

Hanwha Ocean has secured orders for the largest number of submarines in South Korea, totaling 23 vessels (9 units of the 209 class, 3 units of the 214 class, 5 units of the 3000-ton class, and 6 export submarines) since winning the contract for the first ship of the Jangbogo-I project, the "Jangbogo," in 1987.
(Photo by Hanwha Ocean)

At Special Ship Plant No. 3, the first ship of the Jangbogo-III class Batch-II was on display, revealing its massive structure. The term "batch" refers to a group of ships of the same type built together, and as the series progresses from Batch-I to II to III, the ships undergo performance upgrades. The Jangbogo-III Batch-II has a significantly larger displacement than the Dosan Ahn Changho-class submarine, which was the first 3,000-ton submarine designed and built entirely with domestic technology. The Jangbogo-III Batch-II, with a surface displacement of 3,600 tons, is an AIP-equipped diesel-electric propulsion submarine that incorporates advanced technologies in underwater operational capability, detection systems, and armaments. The most fundamental component in submarine construction is the ring frame, which is comparable to human ribs. Multiple ring frames are assembled to create components, several components are combined to form a section, and multiple sections are joined together to complete the submarine's hull. Each section has a diameter of 7.7 meters.

The core of submarine construction is welding. Unlike previous models, the Jangbogo-III uses high-carbon steel, which is a much tougher material. Welding is performed while the material is heated to between 55 and 95 degrees Celsius. On site, welders do not perform the welding directly; instead, they monitor the process as it is handled by machines. Automated machinery performs 90% of the submarine welding, resulting in a defect rate of only 0.006%.

Another feature of the Jangbogo-III class Batch-II submarine is an auxiliary propulsion unit installed on the bottom. This can be used as an emergency backup if the main propulsion system fails, and also allows for quicker maneuvering when the vessel is docking or departing. Factory workers each carry a tablet containing an electronic mock-up, which allows them to inspect the submarine’s internal structure in detail before starting work. These tablets are used for crew training and pre-maintenance inspections.

Kwon Ohjeong, head of the Special Ship Production Planning Team, explained, "The most critical aspect during submarine construction or maintenance is shaft alignment. This process is necessary to rotate the propeller blades underwater, and even a slight misalignment can lead to component wear, speed restrictions, and vibrations, all of which can hinder operational performance."

Hanwha Ocean is bidding for the Canadian submarine project valued at 60 to 70 trillion won. The Canadian Navy plans to acquire up to 12 new submarines, aiming for the first delivery in 2035. (Photo by Hanwha Ocean)

The painting process for submarines involves special treatment. A sponge-like acoustic coating is applied to the surface to absorb enemy radar waves, providing a stealth effect. This technology was first applied to the "Dosan Ahn Changho" (SS-083), the first 3,000-ton submarine independently designed and built with domestic technology. Paint is applied over the acoustic coating, and some toxic substances are included in the paint to prevent marine organisms from attaching to the submarine’s surface. The third ship of the Jangbogo-III class Batch-II was also undergoing this process. Hanwha Ocean is responsible for building all ships of the Jangbogo-III Batch-II series.

In addition to construction, employees were also busy with comprehensive overhauls of submarines. For the overhaul of an 1,800-ton class submarine, all internal components are removed and laid out, requiring a space of 1,000 pyeong (approximately 3,300 square meters). The components were covered in rust and salt, evidence of long periods at sea. Submarines undergo a comprehensive overhaul every eight years, and the manufacturer’s expertise is used to shorten the overhaul period.

The submarines being built and maintained at Hanwha Ocean’s Okpo Shipyard in Geoje, South Gyeongsang Province, are not only responsible for national security but are also regarded as key players in the "K-Defense" industry. Hanwha Ocean is bidding for the Canadian submarine project valued at 60 to 70 trillion won. The Canadian Navy plans to acquire up to 12 new submarines, aiming for the first delivery in 2035. Competitors include Germany’s ThyssenKrupp, Sweden’s Saab, France’s Naval Group, and Spain’s Navantia. The Canadian government is targeting a contract signing in 2028. There is also a high possibility that Hanwha Ocean will lead bids for submarine projects in Poland, the Philippines, and Saudi Arabia. In November last year, Hanwha Ocean signed a strategic partnership agreement with the UK defense company Babcock International Group to pursue submarine contracts in Canada and Poland, among others, and is making significant efforts to secure export deals.

At Hanwha Ocean’s Geoje site in Geoje, South Gyeongsang Province, new factory construction is in full swing. This is a measure to accommodate not only domestic but also overseas shipbuilding projects in the future. In December last year, Hanwha Ocean signed a contract for the construction of the next-generation Ulsan-class frigates Batch-IV ships 1 and 2, following the Batch-III ships 5 and 6. The Ulsan-class Batch-III, known as the "mini Aegis ship," is a project to build six 3,500-ton class frigates. Next, Batch-IV ships 1 and 2 will be constructed, marking the final phase of a four-stage project to replace the Ulsan-class frigates that have been in service since the 1980s, with a total of six ships to be built. This is significant as it will shape the future of frigates operated by the Republic of Korea Navy. The new fourth plant will be constructed at a cost of 110 billion won and will incorporate the latest shipbuilding technologies, including large cranes. It is scheduled to be fully operational in November this year.