Analysis - Sinpo Class Ballistic Missile Sub

North Korea's Polaris: Gorae Class ballistic missile submarine (SINPO Class)
Thank you to unnamed advisers. This work would not have been possible without substantial inputs from experts. Any errors or incorrect assumptions are purely the responsibility of the author however

sinpo Class ballistic missile submarine north korea
Flag North Korea DPRK A lot of things have changed since I first discovered the Gorae Class ballistic missile submarine (aka SINPO Class) in Google Earth imagery in October 2014. At the time, North Korea’s submarine launched ballistic missile (SLBM) program was only a rumor on the peripherals of the defense analysis community. Armed with these rumors the discovery of the submarine was not entirely a surprise, but it was an undeclared type as far as North Korea was concerned. Its existence had been kept a well-guarded secret. Perhaps under the previous ‘dear leader’ the project would have remained obscure, but in the new mood of bravado the type has been thrust into the limelight by the North Korean regime themselves. Along the way there have been plenty of questions about capabilities and some incredulity among observers. But with the latest August 2016 test launch been deemed successful it is now taken very seriously. As I have done all the long. This article tries to keep pace with developments and look behind the headlines at what it means in terms of capability ...

sinpo Class ballistic missile submarine north korea
Pukgeukseong-1 (NK-11) submarine launched ballistic missiles being paraded through Pyongyang, 15th April 2017. Image from

Original artwork in Cold War DIA (Defense Intelligence Agency) style - CLICK for HIGH-RESOLUTION image.

Key points
(On the balance of probabilities...)

Original artwork - CLICK for HIGH-RESOLUTION image.

Nuclear armed ballistic missile submarines are an exclusive club. Only US, UK, France, Russia, China and India have them. Now North Korea is poised to join the club, bringing more distant targets within range. While North Korea's first 'Boomer' is not technologically comparable to the other classes it is a game changer in the strategic sense. I am cautious to suggest that it will be conducting deterrence patrols off the West Coast of US any time soon, but it does present a launch platform which is not restricted to Korea's confined landmass. And whatever the submarine's sea-keeping and endurance relative to proper SSBNs, regional targets such as Japan, Guam and even Hawaii get a bit closer.

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The submarine has one launch silo mounted in the sail. This configuration is similar to the Russian GOLF and HOTEL Class submarines. This may be no coincidence as North Korea received a number of GOLF Class hulls as scrap in the 1990s. It also allows the submarine's hull to be much smaller which is a sensible consideration for a desperately poor country, and even more so if the design is only intended as test platform or limited operating capability.

sinpo Class ballistic missile submarine north korea

The submarine has single-hull construction and appears close in overall hull-form to the indigenous MS-29 Yono. However, being much larger it probably has three decks of just over 2m each. The bow is likely to contain a relatively modest circular sonar array like other North Korean boats, with the forward ballast tank directly behind it. Two or four torpedo tubes are likely carried above it (there could easily be up to ten in a boat this size but this is very unlikely given the need to conserve weight for the main missile). Behind the torpedo room would be the control room with access hatch in the forward portion of the sail. In the center of the sail, behind the control room, a single missile tube points skyward. The missile itself does not extend the whole length of the tube, but requires a compressed air launch system and compensation tanks (to take in extra seawater to balance the boat after the missile is fired). The second half of the boat is likely to be dominated by engines and machinery. There is no indication of Air Independent Power (AIP) being fitted. A large number of heavy duty lead-acid batteries are probably carried on the lowest deck. Crew space would be distributed around the above features, mostly in the forward half of the boat.

sinpo Class ballistic missile submarine north korea
This press image reveals that the Gorea Class submarine has a crew of around 70-80 men:
sinpo Class ballistic missile submarine north korea

Any suggestion that the Sinpo Class SSB is based on the Soviet GOLF, ZULU, ROMEO or KILO Class are plainly mistaken, as are recurring suggestions that North Korean submarines are based on Yugoslavian Heroj or Sava classes. They just aren't.

Gorae Class SSB Specifications (Provisional)
Displacement: 1,455 tons (surfaced), 1,650 tons (submerged)
Length: 68m
Waterline length: 65m
Beam: 6.5m
Speed: <20kts
Range: TBC
Endurance: Approximately 1 month or less
Operating depth: TBC
Propulsion: Diesel-electric
Armament: 1 x NK-11 “북극성-1” (Pukgeukseong-1) SLBMs, possible 2-4 torpedo tubes

sinpo Class ballistic missile submarine north korea

Gorae SSB / NK-11 timeline
The existence of the North Korean ballistic missile submarine was first revealed on this website on 17th October 2014 (days before other sites). It has since been labelled the "Sinpo Class" after the town where the secret shipyard is located.

Capability / Threat
The Sinpo Class is a small boat. It seems that she is built to the requirement of being the smallest possible boat to carry a NK-11 “북극성-1” (Pukgeukseong-1) missile. This reinforces the view that she is only a test boat with limited operational capability at most. Battery and crew provisions would be sorely limited giving an endurance of less than a month. Speed would be quite slow, especially in an operational setting. Although we can expect the boat to remain local, acting as a mobile TEL with her ballistic missiles targeting Japan and South Korea, we should at least ask the question of whether this boat could, in extreme circumstance, threaten countries much further afield. Using a possible ten-day voyage to the launch site and a mean rate of advance of 10kts (which is optimistic and can be considered a parameter) we find that the Sinpo Class can Just about reach a launch position off Hawaii. It's a close call. Darwin in Australia is closer, and most f South East Asia is well within possibilities.
Map drawn before newer solid fuel missile was tested. Revised estimate of missile range reduced to about 540nm (1,000km).

The photos of the sub and first test launch from submerged barge...
sinpo Class ballistic missile submarine north korea
sinpo Class ballistic missile submarine north korea
sinpo Class ballistic missile submarine north korea
sinpo Class ballistic missile submarine north korea


NK-11 “북극성-1” (Pukgeukseong-1 = 'North Star-1' = 'Polaris-1') Submarine launched Ballistic Missile (SLBM)
Length: 9.3m
Diameter: 1.5m
Weight: 14 metric tons
Warhead: Single nuclear weapon
Propulsion: Solid fueled rocket
Launch: Submerged, ignited (not ejected)
Range: TBC

The first missile test (left) appears to show a liquid fueled missile. However this images is believed to have been doctored with a fake plume. The April 2016 launch (right) shows the solid fueled rocket motor. The missile tube cap shown in TV coverage is also consistent with a solid fueled missile.

These images from the August 2016 test launch reveal the lattice control surfaces, similar to several other North Korean missiles.

Satellite Imagery
sinpo Class ballistic missile submarine north korea on google earth
The new submarine first appeared outside the shipyard at Sinpo between 30th April 2014 (when it was bot present in imagery) and 24th July 2014. The July imagery was not available on Google earth until later in the year. The new type was 65m (213ft) long and had a beam of ~6.5m (21ft), making it much larger than the existing Sang-O (Shark) and Yono Class submarines. The location was in fact associated with the manufacturer of the Sang-O Class small attack submarines and in particular with the enlarged 40m version. Initial assessment by this website (credit to unnamed individuals who assisted in the analysis) pointed to a ballistic missile submarine.

sinpo Class ballistic missile submarine north korea on google earth
In imagery from 18th December 2014 a raft is visible moored in front of the submarine. This is consistent with rafts used to test launch ballistic missiles from underwater before it is attempted from a crewed submarine. The layout of the raft is remarkably similar to those used by Russia. Together with a rocket engine test stand near the site this strongly reinforces the hypothesis that this submarine is a ballistic missile boat. The Raft was still present in the latest imagery available taken on a 2nd March 2015 overpass:

sinpo Class ballistic missile submarine north korea on google earth
We can now see what appears to be twin missile silo holes in the sail, resembling a Derringer 1866 pistol. This was mistaken and it is now confirmed that the boat only has one missile tube.

The missile test raft
The raft is a platform that can be anchored and sunk to a set depth. It can then be monitored remotely while the missile is launched from a vertical launch tube mounted centrally. We do not have close-up images of the North Korean Raft but it is remarkably similar to the ones used by the Soviet Union during the 1960s. According to defense sources the KN-11 missile was successfully tested from this raft in Jan 2015.
sinpo Class ballistic missile submarine north korea USSR raft
Submersible Stand PSD-4, Black Sea, 1961. Source: Russian website
sinpo Class ballistic missile submarine north korea USSR raft
Submersible Stand PSD-7. Source: Russian website

Media myths and mistakes
Warning: Inevitably he videos being used by news agencies include a mix of footage from different submarine classes and missile tests. In particular the Gorae Class boat should not be mistaken for the Sang-O 2 (40 meter variant) or ROMEO Classes. This is great footage but should not be confused with the new boat:
Sang-O II Class attack submarine north korea
Romeo Class attack submarine north korea
Similarly, the clips of missile launches often includes 'stock footage' from other countries' tests. These should be easier to spot.

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