Will South Korea get a Virginia-class nuclear submarine?

• Trump said the US will allow South Korea to build nuclear-powered attack submarines, potentially boosting US shipbuilding
• South Korea could convert its KSS-III design into an SSN to gain strategic nuclear submarine capability
• Alternatively, the US Navy’s Virginia SSN design could be an external consideration for the ROKN

US President Donald Trump’s claim that South Korea would build a nuclear-powered attack submarine (SSN) at the Philadelphia Shipyards shocked defense observers while providing a stunning contrast to the carefully developed AUKUS program with Britain and Australia.

Writing on his Truth Social platform on October 29, President Trump revealed that South Korea’s permission to build an SSN using American technology would see shipbuilding make a “major comeback” in the United States.

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It is well known that South Korea has been pursuing SSN capability as a top target, given the clear capability advantages of such platforms compared to conventionally powered alternatives and the vast size of its maritime domain in the Western Pacific.

GlobalData’s analysis show that South Korea operates a sizable fleet of 21 conventionally powered submarines (SSK) across three classes: the Type 209-1200 (nine boats introduced from 1993-2001), the Type 214 (nine boats introduced from 2007-2020) and three of the latest KSS-III hulls delivered from 2021 to present.

A further six in the Batch 2 KSS-III class are planned, providing the Republic of Korea Navy with a modern, capable SSK fleet.

Crucially, Philly Shipyards was acquired in 2024 from Hanwha Groupconsidered at the time as a way to leverage the South Korean shipyard’s expertise to revive the American industry, which is in significant slump.

The announcement can be seen in contrast to the carefully developed AUKUS program between the US, Britain and Australia, which aims to develop Canberra’s nuclear submarine ambitions.

A nuclear-powered KSS-III Batch 3?

With an offer from President Trump to share nuclear propulsion technology with South Korea, Seoul could soon have all the technological elements needed to design and manufacture an SSN.

Potentially this could be done through a modification of the KSS-III design, which, although it displaces 4,000 tons underwater, could almost certainly be redesigned for nuclear propulsion. France Ruby-class SSNs displaced only 2,600 tons underwater, and were much shorter at 74 meters in length compared to the 89-meter form of the Batch 2 KSS.

A nuclear-powered KSS variant would be similar in size and displacement to the former in Britain Trafalgar class, which is admittedly far from as large as that of the US Virginia-class SSNs would still provide a platform that can operate at a strategic level.

The KSS-III Batch 2 design also features a 10-cell VLS system for launching cruise missiles and (non-nuclear) ballistic missiles, a capability that is Britain’s newest. Astute SSNs cannot perform the same way.

What about a South Korean Virginia lesson?

This would be a gamble, but because the US is in desperate need to increase its own pace Virginia-class SSN Block V/VI structures, creating an industrial capacity at Philly Shipyards to add production capacity could provide a solution.

Currently the US is building its own country Virginia-class SSNs at the General Dynamics Electric Boat site in Groton and the HII Newport News Shipbuilding facility in Virginia.

Australia has its own claim to a later model Virginia-class SSNs, newly built or already in service with the US Navy, via the AUKUS program leasing method, which could become permanent if the chosen British design (SSN AUKUS) is delayed.

Clearly, it would be difficult to adopt the US Virginia design into ROKN service, which would present a host of unique supply chain, training and maintenance challenges. However, this would be somewhat offset by the potential to tie into the Australian Sustainability Hub being developed at HMAS Stirling, or alternatively utilize the US’s own sustainability sites.

More likely would be a nuclear-powered KSS-III variant, making the design common to the submarine fleets. South Korea has a significant civilian nuclear energy program and has many of the skills required to exploit and sustain naval nuclear propulsion.

It is possible that the nuclear propulsion facility could be centered around the S9G pressurized water reactor used by the US Virginia SSNs, which can operate for more than 30 years without refueling.

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