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North Korea’s Submarines are not yet a Threat

In nuclear deterrence, the delivery system is just as important as the bombs themselves. Of the three primary systems, intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs), and air-dropped bombs, a submarine ballistic missile force is the best card to have due to their stealth, survivability, and endurance. While North Korea has made great strides with their most recent missile test, they are still a long way from possessing a robust submarine deterrent. Even so, the US should recognize that this will pose a threat if development accelerates, and thus should be prepared to address North Korea’s submarine program as part of any denuclearization talks.

Image courtesy of Darz Mol~commonswik, © 2006.

All of the five major nuclear powers (the US, United Kingdom, Russia, China, and France,) possess a force of nuclear-powered ballistic missile submarines, or SSBNs[1]. For the United States, SSBNs play a vital role as one of the three legs of the nuclear triad, alongside ICMBs and bombers. There is a logic behind each leg of the triad: ICMBs have the quickest response time; bombers are the most visible and can be recalled; and SSBNs are the stealthiest and most survivable, making them ideal for either a second, retaliatory nuclear strike or even a preemptive nuclear first strike. During the Cold War, both the United States and the Soviet Union kept fleets of SSBNs on constant patrol in case things went hot.

Aside from stealth and survivability, endurance is the other major benefit of an SSBN. Since they do not need to refuel often, they can remain at sea for extended patrols, and with adequate oxygen supplies they do not need to surface often either. Nuclear powered submarines, however, are expensive and complex machines. Reactor fuel is not cheap. Most navies do not field exclusively nuclear-powered submarines; diesel-electric submarines are far more common.

In this regard, North Korea is no exception. Their fleet consists of exclusively of diesel-electric submarines. Most of the larger submarines are Soviet surplus Romeo-class attack submarines. As North Korea continues to pursue a fully functional nuclear deterrent, it is only logical that it would look to a ballistic missile submarine as a part of that deterrent. The recent test of an underwater launched ballistic missile confirms that North Korea has been developing an SLBM. But what about an SSBN to carry it?

As mentioned, SSBNs are expensive, and most of that expense comes from the “N” in “SSBN” – the nuclear reactor. The United States Navy, for example, currently estimates it will spend $115 billion on 12 new Columbia-class SSBNs, while Russia is spending and estimated $731 million per boat on its new Borei-class SSBNs. Naval reactors must be smaller than land-based power reactors, and as a result are more complex to build. Typically, naval reactors run on highly enriched uranium, as opposed to the low enriched uranium that land reactors run on. A cash-strapped state such as North Korea cannot afford to build such a vessel, at least not yet.

Instead, North Korea is relying on cheaper diesel-electric technology. Its first homegrown ballistic missile submarine, the Gorae-class (sometimes called the Sinpo-class, named after the Sinpo Shipyards), can carry one or two SLMBs, and uses conventional diesel-electric power. As such, it must surface every few days to recharge its batteries. Recently posted photos of Kim Jong-un inspecting a “new” ballistic missile submarine under construction. Open source analysts believe that this submarine may be a refurbished Romeo-class, with a new sail that carries around three SLBMs. By comparison, the United States Navy’s current SSBN, the Ohio-class, can carry 24 SLBMs.

As North Korea continues to make progress on its nuclear deterrent, it is only a matter of time before Pyongyang makes the leap to more capable ballistic missile submarines. With the advances made in air independent propulsion (AIP), diesel-electric submarines are becoming stealthier and achieving longer endurance times. While the endurance of nuclear submarines will still be superior due to the lack of a need to refuel, AIP technology would drastically increase the potency of North Korea’s submarine deterrent.

Furthermore, North Korea has already made substantial progress on the warhead and missile portions of their deterrent; it is not unreasonable to infer that Pyongyang is already working on the next level for their submarine deterrent. As the United States and the West continue to seek an agreement with North Korea regarding denuclearization, the latter regime’s nascent ballistic missile submarine program should be remembered and accounted for. Limitations on the types and number of SSBs that North Korea can deploy would increase security in northeast Asia and support denuclearization by limiting the number of potential delivery platforms available to Pyongyang.


[1] US Navy and NATO designation for such vessels – “SS” for submarine, “B” for ballistic missile, “N” for nuclear powered.

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John Ashley

John Ashley was the 2017 YPFP Nuclear Security Fellow; he holds a Master of International Policy degree from the University of Georgia, where his studies concentrated in CBRN nonproliferation, export controls, and international security. John also holds a B.A. in History from the University of Georgia, and wrote his thesis on the Great War in Africa. His career goal is to work on the committee staff for the Senate Foreign Relations Committee.

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