South Korea is planning even bigger missile submarines, but they’re not going to be nuclear just yet

South Korea is ahead of the curve at flank speed with its plans to build a fleet of nine KSS-III ballistic missile (SSB) submarines equipped with powerful land attack and ballistic missiles.

On September 28th, Hyundai Heavy Industries launched the third and final KSS-III Batch-1 submarine Shin Chaeho. Meanwhile, Daewoo Shipbuilding and Marine Engineering (DSME) began building the lead boat of a larger, more durable, and heavily armed KSS-III Batch-2 model, named Lee Bong-chang, after a Korean independence activist who tried unsuccessfully to take over Japan on Aug. 13 Murder Emperor Hirohito with two hand grenades. As a good measure, DSME also received an additional 985.7 million won contract (approximately $ 850 million) on September 10 to build a second Batch 2 submarine.

In September there were two more dramatic milestones for South Korea’s missile submarine program. On September 7th and 15th, the first commissioned KSS-III, Dosan Ahn Changho, conducted two tests of a domestic Hyunmoo 4,4 submarine launched ballistic missile (SLBM). This makes South Korea only the eighth country to station SLBMs.

In fact, Seoul’s missile submarines are unique in that they do not use nuclear propulsion or missiles with nuclear warheads – at least so far. The only other non-nuclear powered SSBs in use are a single Chinese Qing-class missile test submarine and North Korea’s coarser Sinpo CU – but both launch nuclear missiles.

Bigger, better and more Korean

The KSS-III missile submarine was originally billed with a sub-launched variant of the surface-departing Hyunmoo-3 cruise missile called the Cheonryong. But after North Korea’s tests of a submarine launched ballistic missile in 2016, South Korean lawmakers were informed that KSS-III could also launch ballistic missiles.

Ballistic missiles are much faster and can potentially carry heavier warheads than cruise missiles, so they may have been seen as more effective at knocking out North Korean missiles before they can be launched as part of South Korea’s ultra-fast strategic target attack strategy (formerly known as chain kill).

At eighty-nine meters in length, the Batch 2 model will be six meters longer and around 300 tons heavier to accommodate ten instead of six vertical rocket tubes. According to Naval News, Batch 2 will also include a new retractable bow thruster to improve maneuverability, as well as changes to its sensors and combat system to improve submarine and surface attack capability, including a new suite of sonars from LIG Nex1. The design also swaps one of the two non-shell-piercing optronic masts built in France for a German fuselage-piercing attack periscope. Overall, the changes have increased the proportion of indigenous Korean components on the KSS-III from 76 percent to 80 percent.

The most dramatic change, however, will be the propulsion system: while maintaining a German-style air-independent fuel cell propulsion system that allows very long underwater endurance at slow speeds, Batch 2 submarines will also be able to store much more electricity by using their traditional lead – Replace acid batteries with lithium-ion battery (LIB) technology.

Japan was the first state to station a LIB submarine, but South Korea is not far behind. The supposedly cheaper LIBs developed by Hanwha reportedly allow 300 percent longer life at a maximum underwater speed of twenty knots and 160 percent longer battery life at sustainable cruising speeds. In total, KSS Batch-2 submarines can cruise underwater for twenty-one days before they have to surface. and if it were caught in a combat emergency, it could maintain high speeds for many more hours than a conventional diesel-electric submarine. The LIBs also last twice as many charge cycles as lead-acid batteries before they need to be replaced.

The LIB’s tendency to overheat and burn has prevented the popular commercial technology from being introduced to submarines until recently, but Hanwha’s senior research engineer told Naval News that the Korean batteries were made robust and responsive to “fire, saltwater, short-circuit, Shock and Heat “were tested. Hanwha’s system uses commercially available Samsung batteries, which are arranged in around two hundred modules, half in the bow of the submarine and the other half in the rear belly area of ​​the submarine. Each module has 192 batteries, which are divided into 8 compartments.

It is currently unclear what additional technologies could be incorporated into the final tranche of three even larger batch 3 submarines. Some speculate that Batch-3 could even incorporate a nuclear propulsion system with a slightly enriched Russian-style fuel reactor.

Nuclear propulsion would allow sustained high-speed cruising and virtually unlimited range and underwater endurance. However, these benefits are arguably exaggerated given South Korea’s significantly lower defense needs and the aging of the North Korean Navy – especially given the high financial and political costs that nuclear propulsion could bring.

Still, politicians could be drawn to the prestige of operating nuclear submarines, even if it only makes military sense if Seoul wants its navy to play a broader regional security role beyond the waters around the Korean peninsula.

South Korea’s missile paradox

In September, both North and South Korea tested their SSB skills. On September 7, the newly commissioned KSS-III Dosan Ahn Changho successfully performed a priming test on the Hyunmoo 4.4 missile’s “cold start” system, which uses pressurized gases to eject the missile from its launch tube underwater . According to the newspaper Chosun Ilbo, a previous ignition test had taken place in an underground water tank at the end of 2020 and later in July with a diving ship.

Then, on September 15, North Korea tested two of its newest anti-submarine missiles, the Pukkuksong-5. Just hours later, Dosan performed a second Hyunmoo 4.4 launch test off Taean on the northwest coast of South Korea, which you can view here.

This time, the solid rocket fired the rocket and sent it on a ballistic trajectory into space before it fell down at many times the speed of sound and allegedly landed exactly on a specified target 400 km away. According to reports, this final test finally cleared the K-SLBM for production and use.

While the test on the same day was a coincidence, the fact that South Korean President Moon Jae-in and Defense Minister Seo Wook were present to watch the launch underscored how Seoul is trying to show that it can rival Pyongyang.

The Hyunmoo-4,4 is reportedly a modification of the South Korean land missile Hyunmoo-2B that has a range of 500 km and carries a 1 ton warhead. But it is much more expensive to station a missile on a submarine than on a truck. So what benefits could South Korea expect from this?

First, a submarine has greater mobility at sea, which means it can target targets out of range of South Korea’s land-based missiles, as well as attacks from unexpected / less defended vectors. However, the range of these land-based missiles is likely to increase significantly as the new Hyunmoo-2C and D and Hyunmoo-4 missiles reach half a mile or more, diminishing the importance of this benefit.

Submarine-based missiles also provide a safe second strike, meaning that an enemy who relies on a preventive barrage that obliterates South Korea’s ability to retaliate must expect their inability to locate and target the patrolling missile submarines destroy.

In theory, this should give Seoul conventional deterrence against a North Korean attack, but there is good reason to be skeptical that more non-nuclear weapons will go a long way in deterring North Korea given the formidable firepower of the South Korean F-15K and F-35 fighters and ground-based missiles.

Conversely, some analysts fear that North Korea could falsely assume that a conventional Hyunmoo-4,4 launch could be a nuclear attack and take revenge with its “use or lose” nuclear weapons.

While conventionally armed, submarine-launched cruise missiles are the norm, other countries have only bothered to deploy nuclear-armed SLBMs on submarines, which are also believed to be more reliable for killing an opponent’s nuclear weapons.

This inevitably leads to the observation that, with the development of an SLBM and the submarines to fire them, South Korea means that should Seoul ever choose to build nuclear weapons – which could only take 18 months – the normally time consuming Have the prerequisites ready to use them at sea. That may not be South Korea’s intention right now, but regardless, it has created a quick path to sea-based nuclear deterrence in KS-III, if it ever wants to.

Sébastien Roblin holds a Masters Degree in Conflict Resolution from Georgetown University and has taught for the Peace Corps in China. He has also worked in education, editing, and refugee settlement in France and the United States. He is currently writing for War Is Boring on security and military history.

Image: Wikimedia Commons