North Korea’s HS-15: Gestation of a Nuclear ICBM

Erik Nolan Analysis Leave a Comment

The DPRK’s latest missile test demonstrated the increasing capabilities of the regime’s nuclear program with the latest, but likely not the last, iteration of its ICBM in the Hwasong-15. The test, which is still being analyzed by security experts, had the trademark fanfare and saber-rattling from Pyongyang that is commensurate with its nuclear development and culminated in the statement that the entire continental United States is now in range of North Korean missiles. However, the information that is available contests the DPRK’s narrative and shows that challenges to an effective nuclear deterrent still remain for the regime.

What is immediately apparent is that the HS-15 is a completely different missile from the previous HS-14 launched earlier this summer. The first and second stages of the HS-15 are wider than its predecessor, allowing for a higher fuel capacity and ultimately greater range.

Additionally, the HS-15’s boost stage is powered by just one engine (which appears to use liquid fuel and oxidizer), whereas the HS-14’s boost phase incorporated a cluster of four engines which led analysts to suspect that the engines were smuggled Soviet RD-250s. The single engine used in the HS-15’s boost phase indicates a gimbaling engine that can vector the thrust and navigate without the need for fins or vernier thrusters.

The HS-15’s launch suggests that the DPRK may have developed a proprietary engine that can effectively boost the second stage and reentry vehicle far enough to be a true ICBM. A proprietary engine would also mean that international efforts to stop the illicit acquisition of foreign missile technologies and components, on which North Korea has relied heavily, are failing or becoming obsolete as North Korea refines its missile program.

Speculation still surrounds the transportation and deployment of both the HS-14 and the HS-15. Both launches broadcasted by KCNA state media showed the missiles being deployed on a TEL vehicle (Transporter Erector Launcher); but, the viability of this method of deployment for the DPRK’s nascent nuclear arsenal is questionable. While it may be strategically advantageous for North Korea to have a road-mobile ICBM that is more elusive and difficult to target, their domestic infrastructure as well as historical instances of TEL-deployed ICBMs by the United States and former Soviet Union offer little credibility to this notion.

Having an estimated 450 miles of paved and navigable roads on which to trundle their TEL and HS-15, the existing road conditions in the DPRK would have to be nothing short of immaculate to allow the vulnerable missile to reach its launching point undamaged. Even if North Korea were to invest its nuclear stockpile in road-mobile ICBMs, the roads themselves would present a security vulnerability that could be exploited to prevent their full deployment. Analysts have suggested it is more likely that the TEL-deployed missiles are serving as a propaganda tool and also acting as a veil to guise the more probable scenario of silo-based missiles secretly installed throughout the country.

Undoubtedly, however, the largest challenges the DPRK faces to establishing a credible nuclear deterrent concerns the second stage and reentry vehicles, which rely on precise and robust engineering to deliver a payload to a target accurately and in one piece. This was notably not demonstrated in the HS-15 launch or subsequent media broadcast by the KCNA, and is indicative of the biggest hurdle that North Korea has yet to overcome. While the HS-15 may have an extended range, capable of covering the entire United States, there is speculation that the missile’s second stage, which contains the reentry vehicle, warhead, and booster, broke up on reentry.

Concerning the ballistics of nuclear warheads, the second stage of an ICBM is extremely complicated and incorporates the most technologies present in a nuclear weapon. For instance, North Korea has thus far not shown that they have been able to effectively miniaturize a nuclear warhead (despite their proclamation that the dummy warhead used in the HS-15 maiden launch was a “super-heavy” analogue), and until that is achieved the DPRK is essentially limited to tipping their missiles with conventional chemical explosives.

Also absent in an overview of the HS-15’s second stage is any mention of the guidance systems. This is perhaps the most important aspect of any ICBM, as the nature of launching a projectile and striking a target thousands of miles away necessitates incredible accuracy. For a nuclear warhead to be launched from North Korea and deliver a hypothetical decapitation strike on Washington, D.C. for instance, the Circular Error Probable (CEP)—which measures the relative accuracy of 50% of potential warheads landing in a given area—exceeds 3000 kilometers without an adequate guidance system.

Finally, any ICBM developed by the DPRK must include adequate heat shielding on the reentry vehicle to survive the immense heat as the warhead screams through the atmosphere in its terminal phase. Developing the correct ablative materials and integrating it with a small enough warhead while still possessing a sizeable yield is yet another aspect not demonstrated in Pyongyang’s latest missile test.

This all suggests that while the HS-15 is range-capable, Pyongyang’s nuclear capability is still severely limited and subsequent iterations of their ICBMs will seek to improve aspects where a credible deterrent is still lacking. Miniaturization, guidance, and reentry survivability are the remaining obstacles in North Korea’s nuclear missile program, and also present opportunities for international actors to control and possibly delay the completion of a North Korean nuclear missile. Additionally, states like the U.S. could make a solid investment in ballistic missile defence, especially in boost phase and midcourse interceptors, to undermine the DPRK’s deterrent while also containing notions of proliferation in states like Japan and South Korea as the situation continues.

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