North Korea’s SINPO-class Sub: New Evidence of Possible Vertical Missile Launch Tubes; Sinpo Shipyard Prepares for Significant Naval Construction Program
Recent commercial satellite imagery indicates that the conning tower of a new North Korean submarine first seen in July 2014 houses 1-2 possible vertical launch tubes for either ballistic or cruise missiles. The boat could serve as an experimental test bed for land-attack missile technology, which if successful, may be integrated into a new class of submarines. In addition, imagery over the past six months indicates that North Korea has been upgrading facilities at the Sinpo South Shipyard in preparation for a significant naval construction program, possibly related to submarine development.
North Korea’s development of a submarine-launched missile capability would eventually expand Pyongyang’s threat to South Korea, Japan and US bases in East Asia, also complicating regional missile defense planning, deployment and operations. Submarines carrying land-attack missiles would be challenging to locate and track, would be mobile assets able to attack from any direction, and could operate at significant distances from the Korean peninsula.
Nevertheless, such a threat is not present today. Moreover, an effort by Pyongyang to develop an operational missile-carrying submarine would be an expensive and time-consuming endeavor with no guarantee of success.
Possible Submarine Vertical Launch Tubes Spotted
Recent commercial satellite imagery provides additional details on North Korea’s new submarine and test stand at the Sinpo South Shipyard (Pongdae Boiler Plant) located on its east coast. Updating our October 19 and 28, 2014 articles, imagery now indicates that the conning tower houses 1-2 small possible vertical launch tubes for either ballistic or cruise missiles. The boat could serve as an experimental test bed for missile technology, which if successful, could be integrated into a new class of submarines.
In imagery from July 2014, the center section of the conning tower, which is approximately 10 meters long and 2.75 meters wide, was partially obscured by a large blue tarp. Imagery from December 18, 2014, indicates that the tarp is no longer present and reveals a rectangular opening approximately 4.25 meters long and 2.25 meters wide. While the current image is of insufficient resolution and quality to look down into the opening, its presence on the top of a large conning tower is unusual and suggests that a panel has been removed to access the interior. Taken in concert with a September South Korean Joint Chiefs of Staff statement that “…the possibility of a North Korean submarine equipped with an SLBM has been detected recently…,” the new imagery suggests the possibility of 1-2 small vertical missile launch tubes.
Figure 1. Newly identified submarine berthed with the secure boat basin at North Korea’s Sinpo South Shipyard (Pongdae Boiler Plant).
Figure 2. A close-up view of the SINPO-class submarine and the opening in the conning tower.
Exactly what missile system would be used in a ballistic missile submarine (SSB) is purely speculative at this point. Several possibilities are a shorter naval version of the Musudan intermediate-range ballistic missile, a Nodong medium-range ballistic missile, naval versions of the solid-fuelled KN-02 short-range ballistic missile or an entirely new system.
While it appears that North Korea’s current efforts are focused on developing a ballistic missile submarine, a less likely alternative would be a guided cruise missile submarine (SSG). This, however, would only be possible if North Korea could access foreign vertical-launched cruise missile technology. Such a route might present an easier, faster route to a submarine-launched missile system.
The presence of vertical launch tubes, if confirmed by additional evidence, would signal a significant advance in North Korean naval construction capabilities and could represent an embryotic step towards expanding Pyongyang’s missile threat to South Korea, Japan and US bases in East Asia. It would also complicate regional missile defense planning, deployment and operations. North Korean missile-carrying submarines could be challenging to locate and track, would be mobile assets with the capability to attack from any direction, and would be able to operate at significant distances from the Korean peninsula.
Such a threat, however, is not present today. Moreover, North Korea’s development of an operational missile-carrying submarine would be an expensive and time-consuming endeavor with no guarantee of success. Building a naval ballistic missile (or even a modified naval version of a surface-to-surface missile) would present new and unique engineering challenges. North Korean missile designers and naval architects have no technical experience with the requirements for installing and launching such a weapon from a submarine.
The December 18 image also shows workers moving around the area, mooring lines, equipment stored on the dock and a heavy-lift construction crane, with its outrigger supports extended on the dock opposite the submarine conning tower. The only reasonable explanation for the presence of this crane is continuing work on fitting-out the submarine.
As noted in previous 38 North articles, the origins of the new submarine design are unclear although it bares a close resemblance in size and shape to the former Yugoslavian SAVA and HEROJ-class boats. Based on analysis of the new image, the boat is approximately 65.5 meters in length, shorter than our previous estimate (see table).
|Table 1. Submarine Characteristics|
|SAVA Class||HEROJ Class||SINPO Class †|
Source: Captain John Moore, Jane’s Fighting Ships, 1980-1981 (London: Jane’s, 1980) 719; and Joseph S. Bermudez Jr., North Korean Special Forces—Second Edition (Annapolis: US Naval Institute Press, November 1997) 161-167.
The previously published drawing of the new boat has been revised as well to take into account this new evidence.
Figure 3. Updated provisional drawing of the SINPO-class submarine.
New Activity at the Vertical Launch Test Stand
The December 18 imagery also indicates new activity at the vertical missile launch test stand in the southern section of the shipyard. The vertical structure above the stand has been removed and there has been recent excavation activity in the adjacent test cell. The reasons for this activity are presently unclear.
Figure 4. Overview of the Sinpo South Shipyard.
Figure 5. A close-up view of the test stand facility.
Preparations for a Significant Naval Construction Program Underway
An examination of commercial satellite imagery over the past six months indicates that North Korea has also been upgrading facilities at the Sinpo South Shipyard in preparation for a significant naval construction program, possibly related to submarine development. Beginning in June 2014, shortly before the launch of the new submarine, North Korea began to update the construction halls at the shipyard. Work commenced on repairing and updating the roof of the 175-meter-long northeast construction hall (A) and was completed by the end of July. That same month, construction began on an expanded launching ramp (at least 85 meters long) for the 190-meter-long southeast construction hall (B). Between August and the end of September, a roof was added to the 140-meter-long northwest construction hall (C). (This building has not had a roof since at least 2002.) Also during September, work started on replacing the roof on the southeast construction hall and was three-quarters complete as of December 18.
Figure 6. Upgraded construction halls at Sinpo South Shipyard.
38 North will continue to monitor activity at the Sinpo South Shipyard in order to gather more data on possible North Korean missile-related activities
Joseph S. Bermudez Jr. is Chief Analytics Officer of AllSource Analysis, Inc.
 “North Korea Developing Vertical Launching System for SLBMs.” RIA Novosti, September 15, 2014, http://en.ria.ru/world/20140915/192959025/North-Korea-Developing-Vertical-Launching-System-for-SLBMs–.html; “S. Korea Spots Signs of N. Korea’s Submarine Rocket Development,” Yonhap, September 14, 2014, http://english.yonhapnews.co.kr/national/2014/09/14/65/0301000000AEN20140914000500315F.html; and Jun Kwan-woo. “Is North Korea Developing Submarine-Launched Missiles?” Wall Street Journal, September 14, 2014, http://blogs.wsj.com/korearealtime/2014/09/15/is-north-korea-developing-submarine-launched-missiles.
 Richard D. Fisher Jr.,“US, S Korean Sources Suggest North has SLBM ambitions,” Jane’s Defence Weekly, September 22, 2014, http://www.janes.com.
 It should be noted that, in the past, North Korea has produced prototype or experimental submarines of conventional design that have not been placed into service due to design flaws. The construction of a ballistic missile submarine presents a significantly higher challenge.
 As higher resolution imagery becomes available it is likely that the characteristics of the SINPO-class submarine will be further refined.