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Sunday, May 23, 2010

North Korean Submarine Fleet

Note: Some submarines are assigned to reconnaissance and infiltration, for details of this mission and equipment see separate section.

22 x Type 031 (‘Romeo’) diesel-electric attack subs
4 x ‘Whiskey’ class attack/training subs (probably inactive)
20+ x ‘Yugo’ type midget subs
1 x ‘41m SSK’ diesel electric attack sub (probably inactive)
20 + x ‘Sang-O’ type midget subs
10+ x ‘P-4’ type midget subs
??+ x Other midget submarines and wet submarines

Type 031 (‘Romeo’) attack sub

Dimensions: L 76m, W 6.7m, Displacement 1,700t submerged
Armament : 8 x 533mm (21’’) torpedo tubes (6 forward, 2 aft) with up to 14 SEAT-60 heavyweight torpedoes or 28 mines

North Korea received some of these boats from China and subsequently locally produced some. Although they are relatively capable they are somewhat dated and ill suited to open ocean operations. There is no evidence to suggest upgrades.

’Yugo’ type midget sub

Dimensions: L 20m, W 2m, Displacement 90t (submerged)
Speed : 10kts surfaced, 4 kts submerged
Armament: 2 x533-mm externally-mounted torpedoes in drop gear in some variants, possibly torpedo tubes in some and none in infiltration variants.

The Yugo class is so named because it was built to plans supplied by Yugoslavia in 1965. North Korea had started an indigenous midget-submarine programme prior to that but had been somewhat unsuccessful, with a crude submarine being captured by the South in 1965 after its crew abandoned it when it was beached on a mudflat during a receding tide on the Han River:

Dimensions: L 5.7m, W 1.1m, Displacement: 3t (submerged)
Speed : 7kts (surfaces), 3kts (submerged).

Although the indigenous midget submarine appears to have been functional, it was very small and extremely limited for infiltration purposes which appears to be the primary peace-time operation for North Korean Navy.

The Yugo boats however are much larger and have room for 4-6 infiltrators and can carry torpedoes or mines for the attack role. They are relatively short ranged though so for infiltration (or attack in wartime) operations in the far south, off Japan or further away, they require transportation and launch from a mother ship.

The ships were built at Yukdaeso-ri shipyard on the west coast from the late 1960s through to the early 1980s at which time they were superceded by the generally more capable Sang-O type. Contrary to some sources, the North Korean Yugo submarine was not very similar to Yugoslavian operated midget submarines such as the impressive Velebit type.

In the early 1980s North Korea developed a much larger coastal submarine known, rather imaginatively, as the “41m boat”. No prizes for guessing the length of this submarine. It is not clear exactly what the boat looked like except that its sail is not unlike the Yugo’s in profile and that it was not a “teardrop” hull. The type does not appear to have been successful and only one is reported and it is unlikely to still be operable.

’Sang-O’ type midget sub

Dimensions: L 34m, W 3.8m, Displacement: 370t (submerged)
Power: 1 diesel, 1 electric motor, 1 shaft
Speed 7.2kts surfaced, 8.8kts submerged
Range: 1500nm
Max Depth: 150 meters
Crew: 15
Armament (attack sub): 4 x 533-mm torpedoes with no reloads (Inc Russian 53-65 ASW torpedoes)
Armament (recce/infiltration version): None. 5 infiltrators and 6 KWP Reconnaissance Bureau Cadre as passengers

Developed as a much improved follow-on to the Yugo type, the Sang-O is well known because one was captured by the South during a botched infiltration mission in September 1997. The Sang-O is much larger and longer ranged than its predecessor.

Some boats have the torpedo tubes replaced by a passenger space and diver swim-out door for infiltration and sabotage missions. The 1500nm range is useful enough to allow the boats to operate without a mother ship in most cases making them much less susceptible to detection.

Hypothetically these subs could be modified to carry anti-ship missiles or Shkval rocket-torpedoes but neither capabilities are reported. 

’P-4’ type midget sub

Dimensions: L 29m, Displacement: 190t
Armament: 2 x 533mm (21’’) torpedo tubes (not fitted in infiltration version)

Another improved midget submarine design, the P-4 is smaller than the Sang-O but also seemingly more advanced. It features an unusual co-axle twin propeller consisting of a large skewed propeller and a much smaller conventional propeller; this arrangement is believed to be an attempt to reduce the submarine’s noise signature.

An example of this type of submarine was captured during an infiltration mission in 1998 and subsequently put into service with the South Korean Navy emphasizing the build quality of the boat. Interestingly the sensors of the captured boat, including the sonar, were of Japanese origin.