[Report] The Secret Behind Hanwha Ocean's 'Covert' Submarine Weaponry... An Acoustic Tank Larger Than a Tennis Court

Visiting the Jungang Research Institute Siheung R&D Campus

On the rainy autumn day of the 15th, Hanwha Ocean’s Central Research Institute at the Siheung R&D Campus was serene. Hanwha Ocean, which had been quietly operating until then, revealed to the media its research institute that integrates shipbuilding and defense technologies about five months after shedding the name 'Daewoo Shipbuilding & Marine Engineering' and rebranding as ‘Hanwha’.

Upon entering the second floor of the building known as the Tank Building, a massive tank larger than a tennis court caught the eye. The smell of calcium chloride disinfectant, typical of swimming pools, stung the nose. This tank is an acoustic tank. Lee Won-byeong, head of the Ship Performance Research Team met on site, said, “Hanwha Ocean is the only domestic shipbuilding company that owns an acoustic tank,” adding, “We study how to build the quietest possible warships.”

Hanwha Ocean Central Research Institute Siheung R&D Campus Acoustic Tank
Photo by Hanwha Ocean

The acoustic tank measures 25 meters in length, 15 meters in width, and 10 meters in depth, holding about 3,100 tons of water, equivalent to 10,000 household bathtubs. Filling and draining the water takes 3 to 4 days. To block external noise and vibrations, it is surrounded by a thick 1-meter double wall. When touched, the inner wall felt rough and bumpy. The team leader explained, “It is designed so that sound waves scatter when they hit the wall.”

When the Masker Air System, a noise reduction technology for radiated noise, was activated, a tremendous amount of air bubbles surrounded the model ship along with the noise. Various noises are reduced as they pass through the air bubbles. Noise reduction is a survival technology for special vessels. The team leader said, “The biggest features of submarines are ‘stealth’ and ‘quietness,’” adding, “If it’s noisy, the enemy detects it first, and it cannot perform its function.”

For Hanwha Ocean, which has structured its business portfolio mainly around defense, this acoustic tank is the ‘ultimate weapon.’ Hanwha Ocean announced that it will invest 900 billion KRW, which is 45% of the 2 trillion KRW raised in a recent capital increase, to secure defense technology capabilities. Park Jin-won, head of the Ship Performance Research Team, said, “The global warship market that Hanwha Ocean can enter is worth 320 trillion KRW.”

Hanwha Ocean developed the Parametric Array System, which artificially generates low-frequency sounds using the acoustic tank. They are also developing a fluid noise suppressor that reduces noise generated by fluid flow inside submarine piping. In June, they established an automated system that automatically adjusts the distance between model ships and measures it precisely.

The world's largest commercial communal tank
[Photo by Hanwha Ocean]

The world’s largest commercial cavitation tank is also located at the Siheung R&D Center. Lee Jang-hwi, head of the Research Planning Team, said, “It is about 62 meters long and the building is about four stories high (21 meters),” adding, “The tank has a square donut shape where water circulates.” It circulates a total of 3,600 tons of water and can generate flow speeds up to 15 m/s.

Research to reduce cavitation is conducted here. Cavitation is a phenomenon where bubbles form around a ship’s propeller when it spins rapidly underwater. This causes noise and vibration and reduces propulsion power. In the case of submarines, it can also lead to detection by the enemy.

An experiment on the phenomenon of ship interaction in a communal water tank Photo by Hanwha Ocean

In the model production workshop, yellow model ships about 10 meters long lined up, each marked with serial numbers and various marks all over their bodies. All ordered ships are scaled down to the exact shape to predict, test, and evaluate various performances. Until now, hulls were made of wood and propellers of aluminum, but from next year, they plan to introduce 3D printing to produce models using plastic ABS material. Applying 3D printing techniques can reduce the model ship production period, which used to take three weeks, by up to 40%, allowing more rapid and flexible responses to sudden experimental requests from shipowners.

Passing the model ships leads to the Towing Water Tank. Model ships are floated in the water and pulled by a towing carriage to test resistance, self-propulsion, motion, and steering performance. It was under construction on this day, so it could not be seen directly. The towing tank boasts the world’s largest scale, measuring 300 meters in length, 16 meters in width, and holding 33,600 tons of freshwater. Built simultaneously with the opening of the Siheung R&D Campus in 2018, this tank is equipped with the latest industry facilities. The water depth can be adjusted up to 7 meters, enabling customized tests for various vessels ranging from merchant ships to warships.

The world's largest towing tank
[Photo by Hanwha Ocean]

At the Autonomous Navigation Control Center, equipment for remotely controlling Hanwha Ocean’s autonomous navigation test ship ‘Han-V’ was on display. Three large screens showed recorded footage from last year’s test at Jebu Marina in Siheung, Gyeonggi Province. The central screen displayed the sea view from the ship during navigation.

Yoo Dong-hoon, head of the Autonomous Navigation Research Team, said, “We use augmented reality (AR) technology on the incoming camera footage to overlay navigation and safety-related information,” adding, “The screen colors change according to risk levels to warn users.” The left screen showed ship control devices such as engine RPM adjustment and route optimization information.

Autonomous Navigation Ship Control Center
Photo by Hanwha Ocean

The right screen displayed Hanwha Ocean’s visualization program based on digital twin technology. This screen physically replicates the actual port and terrain, allowing remote control of ships from land. Yoo said, “Our autonomous navigation technology is on par with competitors,” adding, “Having a dedicated autonomous navigation test ship and a digital twin system differentiates us from competitors.”

Hanwha Ocean 'HS4' Media Lab
Photo by Hanwha Ocean

Opposite is the HS4 Media Lab. HS4 stands for ‘Hanwha SmartShip Solution & Service,’ developed in-house by Hanwha. The service began in 2021 after securing orders for three vessels from domestic shipping companies and has provided services to a total of 18 vessels to date. They are currently conducting conceptual design for the fourth-generation combat unmanned submarine.

Kang Jung-gyu, director of the Central Research Institute, said, “Our dream is to create unmanned, fully autonomous ships powered without carbon emissions,” adding, “We aim to realize this dream as the industry’s first around 2030.”