South Korea has launched its biggest and most ambitious submarine yet, the Jang Yeong-sil, as the first of the second batch of its locally designed and built KSS-III program. The boat, first of three in this sub-class, is notable for its expanded vertical launch cell arrangement, but also boasts a host of other advanced features.
In a ceremony yesterday, the Republic of Korea Navy and South Korea’s Defense Acquisition Program Administration (DAPA) held a launching ceremony for the ROKS Jang Yeong-sil at Hanwha Ocean’s Geoje shipyard, in the southern part of the country.
A construction contract for the submarine was signed in 2019, followed by the steel-cutting ceremony in 2021, while the keel-laying ceremony took place in 2023.
The Jang Yeong-sil, as the first of the Batch II submarines, follows on from KSS-III Batch I, also known as the Dosan Ahn Chang-ho class.
There are some significant differences between the two sub-classes.
The Batch II boats have a surfaced displacement of around 3,500 tons, compared to 3,300 tons for the Batch I submarines. The Batch II is also longer, at 293 feet, compared to just under 274 feet for the Batch I.
More importantly, Batch II brings new capabilities, which the Republic of Korea Navy and DAPA summarize as “enhanced detection, strike capability, stealth, and survivability.”
In terms of detection, Batch II incorporates an updated combat system and sonar system, which are said to offer enhanced information processing and target detection capabilities.
The expanded strike potential of the new submarine is centered around its land-attack capability.
In its Batch I form, the KSS-III already had provisions for six vertical launch system (VLS) cells that are able to accommodate cruise missiles or even submarine-launched ballistic missiles (SLBMs). The Batch II, meanwhile, increases the capacity to 10 VLS cells.
The KSS-III submarines put South Korea in a select group of countries that operate submarines with an SLBM capability. Unusually for a weapon of this type, the South Korean weapon has a conventional warhead.
Successful underwater ejection tests of an SLBM from the first of these submarines were reportedly first conducted around September last year.
Few details are known about the SLBM itself, which is variously named Hyunmoo-IV-4 or K-SLBM. Early reports suggested the missile has a range of 311 miles and that it could be a naval variant of the Hyunmoo 2B ballistic missile. More recently, it has been attributed to a range of 497 miles.
A land-based launch of a Republic of Korea Army Hyunmoo 2B ballistic missile:
Beyond SLBMs, the VLS cells could be used to eventually accommodate hypersonic cruise missiles, a type of weapon that Seoul is currently exploring via the Hycore demonstrator program. A submarine-launched hypersonic cruise missile would give South Korea considerable advantages when it comes to conducting short-notice standoff strikes, especially against highly defended and time-sensitive targets.
Other armament on the Batch II comprises six 533mm torpedo tubes that can be loaded with Tiger Shark torpedoes or C-Star-III anti-ship cruise missiles, or alternatively, Submarine Launched Mobile Mines (SLMM).
Stealth and mission endurance are enhanced by the Batch II’s advanced new lithium-ion battery-based submerged propulsion system. This enables it to “operate underwater for longer durations and sustain high-speed maneuvers, thereby reducing the risk of exposure during operations.” While it is still a diesel-electric submarine at its core, with diesel generators and batteries that charge from those generators, the advanced battery tech can take the place of air-independent propulsion (AIP) technology while offering similar, and in some cases superior, capabilities. Even more interesting, is this new boat also has a fuel-cell-based ‘auxiliary’ AIP capability, so it can presumably charge its batteries or even provide propulsion aside from them, while submerged.
Back in early 2017, The War Zone’s Tyler Rogoway looked at the benefits of lithium-ion batteries, which not only offer advantages over traditional lead-acid cells but could challenge AIP technology for use in new-build submarines overall. This prediction now seems to be playing out.
Other stealth features introduced on the Batch II include various noise and vibration reduction technologies, among them a rubber acoustic coating, which combines to ensure the boats produce less underwater radiated noise.
No less importantly, as a domestically designed and produced submarine, the KSS-III Batch II incorporates a greater proportion of locally developed and manufactured components. This reduces South Korea’s reliance on foreign manufacturers and, very importantly, makes it easier to export the design. The KSS-III is already in the running for Canada’s new submarine requirement, with up to 12 boats planned, and there are growing opportunities for selling advanced diesel-electric subs in the Indo-Pacific region and elsewhere.
The ROKS Jang Yeong-sil will soon embark on a series of sea trials and evaluations, and it’s scheduled to be delivered to the Republic of Korea Navy at the end of 2027. Another two Batch II boats, so far unnamed, are now under construction.
The importance of Seoul’s submarine program has increased in recent years, including the decision to abandon plans to build its first aircraft carrier and instead focus on its underwater fleet, which has received more funding.
In particular, the KSS-III program has emerged as a cornerstone of the Korea Massive Punishment and Retaliation program, or KMPR, also known as Overwhelming Response, an effort to develop ways to retaliate against North Korea, using conventional weapons, should Pyongyang launch a first strike. In particular, submarines are valuable here for bringing the survivable conventional strike capability that the KMPR plan calls for.
The combination of the KSS-III and SLBMs is part of Seoul’s broader focus on missile programs that are being developed and fielded in response to North Korea’s expanding missile capabilities. These also include more powerful land-based weapons, but the SLBM is a much more survivable option, which is of particular importance, bearing in mind the threat of a preemptive strike from the North.
Should the North launch a nuclear attack, the survivability of the submarines should allow a conventional response, even if land-based missiles may have been taken out already. In this way, the SLBMs could be fired against regime targets and command and control facilities, hitting them with much less notice and more kinetic power than a cruise missile barrage. The fact that this quasi-second-strike capability exists should also help dissuade North Korean aggression in the first place.
These submarines and their SLBMs also carry a political dimension, reducing South Korea’s dependence on the United States when it comes to deterrence.
At the same time, the submarines can also take on many other roles in a potential conflict with North Korea, including surgical strikes using cruise missiles, minelaying, insertion of special forces, and, not least, hunting down North Korea’s submarines and new heavily-armed (but questionable) surface combatants.
Potentially, South Korea’s experience with the KSS-III program could lead to even bigger and more ambitious submarines.
In the past, there has been discussion of a potential follow-on nuclear-powered submarine design. With previous missile restrictions on South Korea having been removed, these submarines could potentially be armed with new and bigger SLBMs offering much greater range.
Until the Biden administration scrapped missile restrictions that had been in place since 1979, South Korea was limited to developing missiles with a maximum range of 500 miles. This change could open the door to South Korea developing SLBMs with a range greater than 500 miles, in excess of the Hyunmoo-IV-4.
As it now stands, the KMPR initiative is based around conventional weapons only, but there has been growing speculation that Seoul might eventually commit to developing nuclear warheads, too. SLBMs would be the obvious candidate to deliver these and having this option already integrated into existing submarines would allow for Seoul to move rapidly to fielding a second-strike strategic deterrent if the choice was ever made to do so, which still seems very unlikely at this time.
For now, the Republic of Korea Navy can look forward to starting operations with its most capable submarine so far, providing a powerful and versatile bulwark to fast-paced missile and nuclear developments in North Korea.
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