Introduction

An August 28 analysis of recent commercial satellite imagery assessed that North Korea was building a new type of conventionally powered ballistic missile submarine (SSB). The report termed this a “significant advancement of the North Korean ballistic missile and nuclear threat,” showing the DPRK is “closer to a survivable nuclear force” and “making real progress in developing a second leg of the nuclear triad.”

American television reaction to the report verged on the hysterical, terming this “alarming new evidence” to be “a game changer” and a “very, very ominous development” regarding one of Kim Jong Un’s “most menacing weapons” that “can get pretty close” to the continental US, claiming that “he seems determined to deploy as soon as he can.”

This article will analyze five key contentions of the US television coverage of the SSB:

its advent is “new”; the DPRK is pursuing a “full steam ahead program” to deploy ballistic missile submarines; it will be survivable, unlike the North’s longstanding land-based missile systems; it presents a significant threat to the continental United States; and it represents an “ominous” and even novel addition to the DPRK missile threat to the US.

In fact, indications of the new-type SSB have been recognized for years. We do not know how many SSBs the DPRK intends to produce, or how quickly. The new SSB is almost certainly significantly more vulnerable than the North’s land-based missiles. Its vulnerability and operational limitations render it a marginal threat to the continental US. Overall, the new SSB would provide only a small addition to the threat posed by the DPRK’s much larger, increasingly longer range, and much more survivable land-based ballistic missile force.

How “New” Is a DPRK SSB?

The North’s construction of a new-type SSB is far from “new.” The possibility has been flagged since at least January 2015, when it was reported based on analysis of commercial imagery that North Korea began work in June 2014 on the infrastructure to build a new type of submarine—one that right away was noted as possibly being an SSB. By September 2016, indications of the movement of numerous components into the completed infrastructure suggested construction was under way. Press reports in October 2017 said US intelligence detected a new diesel-electric submarine under construction, and said the submarine is likely an SSB.

The imagery underlying the August 28 report only shows a continuation of the apparent submarine construction activity noted since September 2016—a continuation itself noted elsewhere as recently as June 2019. In fact, the newest information in the report came not from satellites, but from the photos the North Koreans released on July 23 of a new type of submarine on the building ways inside a construction hall.[1] That submarine almost certainly is the one whose construction has been indicated in open-source imagery since 2016; the photos were assessed within days to be of an SSB capable of carrying three submarine-launched ballistic missiles (SLBMs)—in a design remarkably similar to the September 2016 prediction of a submarine analyst.

Is the DPRK Pursuing an SSB Program, and at “Full Speed”?

The North has invested in significant infrastructure that would permit the construction of additional (and even larger) SSBs. It also has built between 2011 and 2014 two missile test stands used for SLBMs and a ground test facility for large solid-propellant rocket engines of the type used on the DPRK’s most recent KN-11 and larger future SLBMs. The construction of these SLBM-related facilities further presaged the advent of a new SSB to carry the related missile.

At this point, however, we do not know whether the new SSB is a political signal or a dictator’s vanity project, or if North Korea will build an SSB force of at least several boats (which would be required for a true “second triad leg”). There currently are no open-source indications of how many SSBs the DPRK intends to build, or how quickly. Nor is there any basis, either on the submarine side (where the new-type SSB has taken some three years to build and still has not been rolled out of the construction hall) or on the SLBM side (where there have been no apparent flight tests since August 2016[2]), to substantiate the US TV claim that Kim “seems determined to deploy it as soon as he can.”

Will the SSB Be Survivable, Unlike “Vulnerable” DPRK Land-Based Missiles?

The American TV coverage has overstated the survivability of a North Korean SSB and understated the survivability of the DPRK’s longstanding force of land-based ballistic missiles, claiming land-based missiles can be taken out (even “easily” so), while taking out subs is “much more difficult.”

The new SSB appears to be based on the 1950s-vintage Soviet ROMEO-class diesel-electric submarine, very noisy boats that are thus highly susceptible to acoustic detection while having only a limited ability to know that they are being tracked by Allied submarines. North Korean SSBs clearly would become priority targets for allied intelligence in peacetime and for allied anti-submarine warfare (ASW) forces in crisis and wartime, and the US has over 65 years of experience in detecting, tracking and combating Soviet-style diesel-electric subs. This is not to say that North Korean SSBs would be easy prey for the US and of no concern, especially if they remain in the Sea of Japan (East Sea), but they would be operating under conditions of allied air and naval superiority, and would face a substantial risk of destruction prior to or during launch operations.

North Korea’s road-mobile missiles, on the other hand, have a high probability of avoiding detection and attack once they have deployed from garrison (which they would almost certainly have done at the outset of a crisis and prior to war). Land-mobile missile survivability would further benefit from the DPRK’s long history of using camouflage, concealment and deception; its thousands of underground facilities;[3] and the ability to plug-in to landline communications networks unavailable to sea-based systems. As stated in a previous piece, Iraq’s ability during 1990-1991 to preserve most (if not all) of its mobile Scud launchers[4] in the face of coalition air superiority and a dedicated “Scud-hunting” effort—and in desert terrain, to boot—underscores the substantial survivability benefits competently operated DPRK land-mobile ballistic missiles enjoy compared to North Korean SSBs.

What Is the North Korean SSB Threat to the Continental United States?

American TV commentators have said that North Korean SSB’s “can get pretty close” to the continental US, wondering if they “would put everybody in the United States at risk.” But, in fact, the SSB’s vulnerability and operational limitations render it a marginal threat. (For what it is worth, North Korea has stated that the submarine it revealed in July 2019 is intended to operate in the Sea of Japan.[5])

It is possible for the new-type North Korean SSB to sail within missile range of the US West Coast. Assuming deployment with the DPRK’s most recently tested KN-11 SLBM (1,200 km range), an SSB would need to sail some 6,800 km to strike the West Coast; returning home would require another 6,800 km, not counting any loiter time off the US. The ROMEO-class submarine, the apparent basis for the new DPRK SSB, is assessed to have an endurance of about 7,000 km[6]—making a one-way mission striking the West Coast with KN-11s feasible.[7] (A similar attack against Hawaii would require a 5,700 km transit—still a one-way mission. Nor could Guam be targeted from within the Sea of Japan, which would require launching from the east side of the Japanese Islands.)

Putting aside whether the DPRK would mount such a mission, which would be operationally ambitious for the Korean People’s Navy, whose submarines rarely put out to sea and only operate on short exercises, the already substantial vulnerability of the new SSB noted above would be magnified greatly by the lengthy transit through the deeper Western Pacific, which would erode the SSB’s operational advantages compared to deploying in the shallower Sea of Japan. The need to cover such a large area would impose many more opportunities for detection as the SSB proceeded east, all the while coming within the coverage of successive US ASW systems. The SSB would have to either transit the whole way using its noisy diesel engines, or use them every 480 km or so when its batteries ran out and had to be recharged, which would render them more vulnerable to detection. (Recharging might be even more frequent if, as one submarine analyst suggests, the new SSB used some of the ROMEO’s battery space to house SLBM launch tubes.) Any requirement for the SSB to communicate with home would add further detection opportunities. The SSB is, therefore, unlikely to represent “a surprise first strike weapon, inching quietly towards its target undetected and then launching a barrage of missiles.”

How Significant an Addition to the DPRK Missile Threat Is the New SSB?

The new SSB is not an “existential threat,” “a major advance in its [DPRK’s] arsenal,” “an ominous weapon,” “a significant escalation of the North Korean ballistic missile threat,” or any of the other overwrought labels noted above. It will not expand the target coverage of DPRK land-mobile missiles, or add meaningfully to the number of warheads the DPRK can deliver (which can be done more cost-effectively by adding more land-mobile missile launchers than by adding more SSBs).

South Korea, Japan, and Okinawa already are covered by the DPRK’s existing Nodong land-based medium-range ballistic missiles with ranges up to 1,500 km.

The North has conducted three apparently successful tests of the 4,500 km range Hwasong-12 land-based intermediate-range ballistic missile, which is able to reach Guam, and may have deployed the 4,000 km range Musudan land-based IRBM in the early 2000s.[8]

The DPRK has conducted two apparently successful flight tests of its 10,000+ km range Hwasong-14 and one its 8,500-13,000 km range Hwasong-15 land-based intercontinental ballistic missiles, which could cover at least half of the continental US from North Korea. Based on its historic practices, the North could have already begun deploying these systems or could do so at any time.

The new-type SSB almost certainly is substantially less survivable than the DPRK’s land-mobile ballistic missile force, and would be even more vulnerable if it were to be forward-deployed against the US West Coast or Hawaii. (The DPRK’s flight testing of a road-mobile version of the KN-11, the KN-15 [Pukguksong-2], further underscores its understanding of the superior survivability and cost-effectiveness of its land-based missiles.)

Although some have contended that the allies will have to add new ASW assets to combat DPRK SSBs,[9] they have had to plan to devote substantial ASW resources since at least the mid-1970s against North Korea’s submarine fleet, currently one of the world’s largest, and may well instead just prioritize DPRK SSBs as targets for their existing ASW assets. (Even if new ASW assets are added, it is highly unlikely that “could provoke China and Russia into being more aggressive in the Pacific.”)

The SSB deployed off South Korea does offer the potential to strike ROK targets from different directions than DPRK land-based missiles, further complicating the task of missile defenses.[10] Doing so for Japan would require deploying to the east of that country, making the SSB more vulnerable than if in the Sea of Japan, and doing so for Guam or Hawaii would require much longer transits, meaning even greater vulnerability. But the SSB probably will only carry nuclear-armed SLBMs; these would not be used in the most probable, potentially lengthy, initial conventional stage of a conflict—in which the DPRK, heavily reliant on conventional ballistic missiles, would have an urgent need to suppress allied missile defenses well before the war went nuclear. Indeed, since May, the DPRK has been flight testing three or four new types of land-based, conventionally armed short-range ballistic missiles with unpredictable flight trajectories that will substantially complicate missile defenses throughout the ROK.

Much Ado About Very Little

North Korea’s new-type SSB (even a future SSB force) would provide only a marginal addition to the threat posed to South Korea, Japan and the US (including Guam and Hawaii) by the North’s much larger, increasingly longer range and much more survivable land-based ballistic missile force. While adding SSBs to the mix could “give US and allied war planners a headache,” it is an ASW headache they have been working to mitigate for many years, and an SLBM headache that pales in comparison to the North Korean land-based missile threat.