North Korea's New Missile Submarine: Hero Kim Gun-Ok
North Korea is known for its large fleet of outdated submarines. The backbone of its patrol submarine force are approximately 15-20 ROMEO class boats. They have poor stealth, weak sensors and limited endurance. Yet when competently commanded they still represent a serious threat to shipping. What is more, North Korea has begun re building them into more more dangerous submarines.
Original artwork. CLICK to Enlarge.
North Korea launched its first rebuilt ROMEO-Mod submarine, Hero Kim Gun-Ok, on September 8, 2023. The boat is armed with ten missiles in vertical launch tubes, likely four ballistic and six cruise. These are carried under a distinctive turtle-back extending out behind the sail. The missiles themselves can be considered modern and generally reliable. And they can potentially carry nuclear warheads.
The new role is likely strategic strike against South Korean or Japanese cities and key bases. The exact types of missiles have not been confirmed. But we can deduce that the ballistic missile is the KN-23 Hwasong-11S. This short-range ballistic missile (SRBM) flies on a quasi-ballistic trajectory. The family is generally reported to have a maximum range of 690 km, although specifications for the submarine launched variant are not available.
The cruise missiles are possibly “Pulhwasal-3-31” or “Hwasal-2” (or possibly both types are closely related). Broadly Tomahawk or Kalibr-like, these have been test fired repeatedly. The observed launches of the Pulhwasal-3-31 from a submarine appeared to be from the torpedo tube however.
KN-23 Hwasong-11S (left) and Pulhwasal-3-31 (right).
In order to add the missiles, an extra hull section has been inserted behind the sail. Overall length is barely changed however because a large part of the bow has been lopped off. The cut appears to be immoderately in front of the existing pressure hull, suggesting that the inner hull is unchanged (which seems sensible).
The removed part includes most of the length of the torpedo tubes. So the torpedo tubes are either shorter now, or the torpedo room has been reworked to accommodate the tubes. Maybe the forward torpedoes have been done away with, relying on the aft torpedo room only. One suggestion would be that the heavyweight 533mm (21”) tubes have been replaced by lightweight torpedoes. These could be carried within the shortened tubes. North Korea already uses lightweight torpedoes in the anti-ship role. Whatever the case, the torpedo room is a compromise.
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Hero Kim Gun-Ok is almost certainly a different submarine to the modified Romeo Class boat, Sinpo-C, reported in 2019. That submarine appears to have been modified to carry two or three larger SLBMs. The existence of both modifications suggests a mixed fleet of missile submarines going forward. Some, the Sinpo-C class, would carry the Pukguksong family of strategic missiles, and the Hero Kim Gun-Ok class would be the 'tactical' type.
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