Naval Warfare

PREMIUM: South Korea plumbs the ocean depths

10th February 2021 - 06:31 GMT | by Gordon Arthur in Christchurch

South Korea is becoming prolific in its development of indigenous vessels for tasks performed on the surface or under the water, and many of these designs are unmanned.

South Korea is ploughing forward into unmanned technologies for surface and underwater craft. Indeed, its most ambitious dream yet is to create an uncrewed nuclear-powered submarine as part of its embrace of the Fourth Industrial Revolution.

The Agency for Defense Development (ADD) released its Novel Weapon Systems Yearbook on 20 January, and one of the 21 conceptual projects mentioned in it was an unmanned nuclear depot submarine.

The stealthy vessel could dive to depths of 1,000m and move at a top speed of 60km/h. The yearbook stated the ‘submarine depot ship can operate without personnel through the use of a next-generation nuclear system that runs on low-enriched uranium and a next-generation concept of intrinsically safe nuclear power’.

The description added: ‘This would be deployed on reconnaissance and search and rescue operations, as well as on anti-submarine and mine-laying operations. In an emergency, its missions would be to launch torpedoes and lay mines capable of quickly striking enemy submarines and surface ships, and to carry out surveillance and reconnaissance in specific areas and identify danger signals.’

This description indicated that the concept would have pretty much the same duties as existing crewed submarines. It is described as a depot submarine because it could release its own UAVs, USVs and AUVs to widen its ISR reach.

Seoul certainly has aspirations to develop a nuclear-powered submarine, feeling the need to do so because of North Korea’s pursuit of boats that carry submarine-launched ballistic missiles (SLBM), some fitted with nuclear warheads. Kim Jong-un declared recently that a submarine design had now entered its final review stage.

The future KS-III submarine ROKS Ahn Mu was recently launched. (ROKN)

However, the topic of nuclear-powered submarines is controversial in South Korea. This was evident when the ADD swiftly reversed course and said the same day that the conceptual submarine’s future power source had not been determined, and that it was supposed to be called a ‘multipurpose unmanned submersible’.

An ADD spokesperson said: ‘The almanac that was initially posted was an interim draft rather than the final approved version, leading to this misunderstanding. Nuclear power is one of the options for the propulsion of the multipurpose unmanned submersible, but no decision has been made yet.’

An unmanned but armed nuclear-powered submarine is ambitious. It raises all sorts of questions about security too. What happens if it has an accident or is targeted by a hostile country, for instance?

Whilst on the topic of submarines, Daewoo Shipbuilding and Marine Engineering (DSME) launched the Republic of Korea Navy’s (ROKN) latest 3,000t KSS-III submarine, Ahn Mu, on 10 November 2020. ROKS Ahn Mu (SS-085) is expected to enter service next year.

It is the second of three submarines in this 83.5m-long class. The first-of-class ROKS Dosan Ahn Chang-ho, was launched in 2018. With an underwater endurance of 20 days, this submarine type has six vertical-launch tubes for missiles. The first KSS-III claimed a world record last December for the longest continuous operation underwater of a diesel-electric submarine.

The ROKN Submarine Force Command already has nine 1,200t Chang Bobo-class and nine 1,800t Song Won Il-class submarines in service. It also possesses an unknown number of mini-submarines.

Three of the Chang Bobo class had been upgraded by the end of 2019 (SS-063, SS-069 and SS-071), and on 11 December 2020, it was announced that DSME had received a KRW165 billion ($151 million) contract to upgrade another three of this class. The modernisation includes a new combat management system, enhanced target detection/tracking, and a new towed array sonar.

South Korea is also developing a new SLBM based on the 500km-range Hyunmoo-2B missile. Ejection tests on land were completed last year, and first underwater tests should occur in 2021. This new SLBM will arm KSS-III submarines.

A scale model of the original Sea Sword USV from LIG Nex1. (Gordon Arthur)

USVs are also a fertile area of R&D in South Korea. LIG Nex1 has been developing its Sea Sword (Hae Gun in Korean) USV that has a high-speed monohull made of fibre-reinforced plastic. A first Sea Sword II prototype was unveiled in 2019; it displaces 11t and measures 12m long. This is 3m longer than the original Sea Sword USV.

Two diesel engines and two Kamewa waterjets offer a top speed above 35kt. A more sedate 20kt speed allows a maximum range of 180nm. It can carry swappable mission modules.

Main tasks envisaged for the Sea Sword are ISR in high-threat areas such as near the border with North Korea, checking radar blind zones such as coves, and tracking suspicious contacts like illegal fishing boats. The Sea Sword can also be armed with a K6 12.7mm machine gun in a Hyundai Wia RWS, eight-cell 70mm Poniard rockets or Raybolt missiles.

Last November, LIG Nex1 revealed its Sea Sword III USV. Its specifications are similar to those of the Sea Sword II, but a key difference is that the newer craft can carry up to eight personnel instead of just two for the preceding design. It is targeted at the Republic of Korea Army as a replacement for smaller patrol boats used for coastal patrol.

An artist's depiction of the mine-detecting AUV from LIG Nex1. (DAPA)

On 9 December 2020, DAPA announced an $11 million contract with LIG Nex1 for an AUV mine detector to be developed by 2023. The camera- and sonar-equipped vehicle will be able to swim for 20h when searching for mines, detecting intruders, supporting rescue missions or collecting topographic data.

The ROKN’s mine countermeasures fleet currently relies on Swallow-class and Yang Yang-class vessels. The new AUV will be deployed aboard Mine Sweeper Hunter-2 mine countermeasures vessels to be constructed from 2024 onwards.

In other underwater news, Hanwha Defense is developing a large-displacement UUV designed for anti-submarine warfare. Unimaginatively it is called the ASWUUV, and it was unveiled in October 2019. The programme commenced in 2017 under the auspices of the Defense Acquisition Program Administration (DAPA). It should be finished by next year after.

The ASWUUV would be part of a more comprehensive surveillance network of sensors such as harbour facilities, unmanned buoys, surface vessels and UUVs. It would be powered by fuel cells and feature three sonars (one forward-looking and two flank arrays).

In 2018, the ROKN fielded a new remote-controlled underwater mine disposal vehicle manufactured by Daeyang Electric Company. Ten such vehicles are now in service. It can dive 400m, and it is 3.65m long and weighs 437kg. Top speed is 7kt via lithium polymer batteries. A fibre-optic cable permits a control range of 2km.


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