Primer: North Korea's New Nuclear Submarine
North Korea’s first nuclear submarine was initially revealed to the public in March 2025. At the time only partial images of the hull were shared. Now new images, published on December 25, show the largely complete submarine. A much larger boat than previous indigenous designs, it bears some stylist similarities to South Korea’s KSS-III class, yet retains some of the peculiarities of the Hermit Kingdom’s unique submarine heritage.
CLICK to Enlarge.
The red paint is likely primer and appears to have been freshly painted for the inspection of the ‘great supreme leader’. No scaffolding is present, and yet many details do not appear to have yet been added, not least the sonars. This illustrates the importance of the appearance of completion under the authoritarian regime, and geopolitical motovations behind the timing of the event, so the fresh paint may mask some outstanding details. Having said that, North Korea is not known for wholesale fakery in military equipment and what is shown is likely the real thing.It is likely that the boat will be painted black, and/or receive anechoic tiles (if so, likely a defence technology transfer from Russia) before it is launched.
Although the photos may have been retouched by North Korean state media, they are overall credible and likely reflect the overall form, plus many details, of the submarine. Note that there are six torpedo tubes arranged in a two-over-four layout. North Korea produces a range of 533mm (21”) heavyweight torpedoes which, in the context of an SSBN, will be used primarily for self-defence.
The boat will be vastly larger than the boats north Korean submariners are used to. Reports indicate that it has a displacement of 8,700 tons. Analysis of the images using reference points methods suggests a hull diameter of around 11 meters (36 ft), which is slightly less than my previous estimate of 12.5 meters (41 ft). Length is approximately 100 meters, possibly more. Overall this makes the boat around the same size as the Royal Navy’s Astute class SSN. The main difference of course is in armament.
The submarine is clearly, and as expected, a ballistic missile boat (SSBN). It appears to have a single row of 8 or 9 missiles mounted in a very large fin (sail). This arrangement is typical of early Cold War Soviet SSB/SSBNs but it is not clear why, with such a large hull diameter, it is still needed. The missile silos are likely to be extremely long, up to almost 18 meters (59 ft) tall. This is much taller than the largest observed North Korean submarine launched ballistic missile, the Pukguksong-6 which is around 13 meters (43 ft). North Korea received ex-Soviet Pr.629 GOLF Class ballistic missile submarines, which had the launch tubes in the fin, and also used this arrangement in its Gorae Class test boat. There has been speculation in South Korean sources that the extra large sail is to accommodate the even larger Hwasong-18 ground-based missile, mounted in slanted tubes.
Pukguksong-6 missile paraded in 2022.
The boat, probably made necessary by the increasing size of North Korea’s strategic missiles which can no longer fit into the legacy ROMEO class hull, has been under construction for years. A ballistic missile conversion of a ROMEO appears to have been shelved c2019 although a tactical version, the Hero-Kim-Gun-Ok class, has been launched in 2023. Reports that all of North Koreas ROMEOs would be so modified have not borne fruit and the focus has instead shifted to the nuclear-powered design.
The fairing added to the lower hull is typical of flank-array sonars. It is comparatively large however and, oddly, there is no indication of the forward sonar dome under the bow.
There have been credible reports that North Korea received assistance, likely including a reactor and propulsion elements, from Russia as part payment for the former’s participation in the invasion of Ukraine. These reports have been added to in the past day by rumours that the Ursa Major, a ‘gun runner’ sunk by limpet mines in the Mediterranean on December 23 2024, was also carrying submarine reactors for North Korea. These latest reports should be treated with caution, but the wider story is that this submarine is likely built with some degree of Russian assistance.
The inlet scoop for the cooling system for the nuclear reactor. This reinforces that it is nuclear powered, and that there has been a technology transfer from Russia.
Kim Jong Un, the leader of North Korea, inspecting the submarine. He is seen walking beside the port-side of the fin with one of the missile silo doors above. Note the gap between this and the hydroplanes, indicating a single row of missiles with alternating port-starboard doors.
Initial analysis suggests that the missile silos may be arranged in a slightly uneven way, with the gap between the first and second tubes being greater than the subsequent ones. Additionally, both the first two tubes appear to have doors which hinge from the starboard side. If this turns out to be correct, the reason is probably to do with needing space for other systems, either in the fin or in the hull.
One of the first images shown in March 2025, which only shows a portion of the hull.
Related articles (Full index of popular Covert Shores articles)
North Korean Hero Kim Gun-Ok Class ballistic missile submarine w/Cutaway
