By Michael Elleman, Consulting Senior Fellow for Missile Defence
North Korea has fired two intermediate-range ballistic missiles from its Wonsan base on the peninsula's eastern coast, violating United Nations resolutions that proscribe the use of ballistic-missile technology. The first launch attempt, in the early hours of 22 June local time, failed after flying only about 150km. The second test shot flew on a steep trajectory and landed in the East Sea roughly 400km from the launch site. Though it is too early to conclude definitively, the latter flight appears to be the first successful Musudan test, after five previous attempts ended in failure.
Additional test launches are needed to validate the Musudan's (Hwasong-10) performance and reliability, after which the missile could be deployed with confidence. An operational Musudan missile could strike targets throughout the region, though initial analysis casts doubt on its ability to reach the US island territory of Guam with a warhead weighing more than 500kg. Regardless, the success of the test, and the confirmation that North Korea does indeed possess engines more powerful and efficient than those used in the past for the Scud and Nodong missiles, poses a longer-term threat to the US. With the more powerful engines, North Korea could build a mobile, intercontinental-ballistic missile similar to the KN-08 and KN-14 mock-ups displayed previously. Both the KN-08 and KN-14 would, in principle, be capable of reaching the US mainland.
What do the flight tests reveal?
The Hwasong-10 is believed to be based on the R-27 (SS-N-6), a submarine-launched missile fielded by the Soviet Union and retired years ago. How and when North Korea acquired the R-27 remains a mystery, though the most thorough accounts of the history suggest that R-27 kits arrived before 2003. Mock-ups of the Hwasong-10 were seen during a military parade in Pyongyang in 2010, and several times since. The first known flight test occurred on 15 April 2016, with subsequent launch attempts on 28 April, when two missiles were fired, and again on 31 May. The two shots on 22 June were the fifth and sixth firings of the missile. The initial four launches reportedly failed soon after ignition, with the first test destroying the launcher. The fifth launch appears to have succeeded partially, though it only travelled approximately 150km. The second test, according to South Korean reports, impacted in the East Sea after 400km of flight, and reached an altitude of more than 1,000km. A North Korean news release verified the 400km range, and specified the missile reached an altitude of 1,413.6km. Pyongyang also published photographs of the Hwasong-10 missile for the first time.
The flight data and photographs offer a basis for characterising the Hwasong-10 more thoroughly than was previously possible. Photographs show a missile that is slightly longer than the mock-ups paraded in 2010, and about three metres longer than the Soviet R-27 missile. The additional length facilitates the extension of the propellant tanks, allowing the North Korean missile to carry an additional four tonnes of fuel. The extra propellant should lengthen the range of the missile.
The photographs also reveal the incorporation of grid fins at the aft base of the Hwasong-10. Previous versions of the missile did not have the grid fins. They were likely added to the design to provide greater aerodynamic stability during the boost phase of flight, which might have been necessary after North Korea stretched the length of the Hwasong-10. It is not possible to determine whether the grid fins were added after the first four flight failures, or have been in place since the start of testing.
The exhaust plume produced by the North Korean missiles provides solid evidence, provided the photographs are authentic, that the Hwasong-10 uses the 4D10 engine originally designed and built for the Soviet R-27. The propellant combination used by the 4D10 engine is more energetic than that employed in the Scud or Nodong missiles. The higher-energy combination means the 4D10 engine can generate more thrust per unit of propellant consumed, which in turn allows for a smaller missile, thus making it possible to build long-range missiles that can be mounted, carried and launch from road-mobile trucks.
The Hwasong-10’s flight trajectory was highly modified to shorten the range, while at the same time allowing the missile to consume its propellant load. Though not stated, the missile likely landed within North Korea’s territorial waters, which would deny foreign intelligence services the opportunity to recover the warhead or missile body. It also improved North Korea’s chances of recovering the warhead to determine whether it survived the thermal and aerodynamic loads experienced during high-speed re-entry into the atmosphere.
Lofting the missile on a steep, almost vertical path resulted in the warhead reaching an altitude of 1,413km, while travelling a distance of only 400km. These two data points, along with the photo evidence and technical information about the original R-17 missile, provide enough information to model the Hwasong-10's performance when an operational, or minimum-energy, rather than a highly lofted trajectory is assumed. The modelling results are illustrated in the graphic below. The R-27 carried a 650kg payload, so it is assumed the Hwasong-10 carries a warhead of similar size and mass. If true, the Hwasong-10 has a maximum range of about 3,150km, which falls 300–400km short of US territory and military facilities in Guam.
North Korea's first success with the Hwasong-10 shows that a prototype can work. However, the reliability of the missile remains highly uncertain. Pyongyang will need to repeatedly test fire the Hwasong-10, under a variety of conditions, using a range of trajectories before it can be deemed a reliable and viable strategic weapon. The process should take two or more years.
It comes as a surprise, however, that the Hwasong-10 does not appear to be capable of threatening Guam, unless the warhead mass is less than 600kg, and more probably 500kg. This would require North Korea to design and build a nuclear bomb that weighs less than 300kg.
The long-term implications of these latest tests lie beyond the development of the Hwasong-10. Rather, the confirmation that North Korea has access to the 4D10 engines means that road-mobile KN-08 or KN-14 inter-continental ballistic missiles (ICBMs) are possible.
North Korea has already ground tested a pair of 4D10 engines clustered together to demonstrate a possible first-stage propulsion system for a prospective ICBM. However, at least five to seven years of further design and testing are needed before North Korea could field a viable ocean-spanning missile. The time needed to develop an ICBM offers Washington a small window of opportunity to engage Pyongyang and work out a deal that prevents or deters it from flight testing a KN-08 or KN-14, or similar. Without flight tests, North Korea would not know if its ICBMs work. And without some measure of the missile’s reliability, Pyongyang would necessarily have to assume great risk if it attempted to launch it against an adversary. The history of first- and second-generation ICBM development elsewhere shows that missiles fail more often than not during initial testing, a fact that is consistent with North Korea’s experience with the Hwasong-10. The US must leverage this fact to reduce its vulnerability to a potential North Korean nuclear attack on its mainland.