Almost unnoticed amidst the tidal wave of publicity around the events in Charlottesville, Virginia a fascinating report on the North Korean missile programme by the Bulletin of the Atomic Scientists has gone by practically unnoticed.
The report’s conclusions differ sharply from those made public recently in the US, and which have been attributed to the Defense Intelligence Agency.
They dispute the effectiveness of the North Korean ballistic missile programme and the extent to which the newly launched Hwasong-14 missile truly is an ICBM capable of launching nuclear missile strikes on the continental US.
They also make a circumstantial case that the Hwasong-14 missile has been created with rocket engines and technical expertise obtained from Ukraine, though it should be stressed that there is no definite proof of this and that this is not a claim that the report itself actually makes.
Something should first be said about the authors of the report. They are described in this way in an article about the report in Newsweek
Massachusetts Institute of Technology rocket expert Ted Postol and two German experts, Markus Schiller and Robert Schmucker of Schmucker Technologie, published their findings Friday in the Bulletin of the Atomic Scientists, in a paper they titled “North Korea’s ‘Not Quite’ ICBM Can’t Hit the Lower 48 States.”….
Postol is professor of science, technology and national security policy at MIT who has advised the Pentagon and Congress on missile-related defense projects. Schiller and Schmucker are missile engineers with the Munich-based company who have previously analyzed North Korean missiles, and in 2012 determined that the country’s supposed ICBMs were “fakes.” Schiller has worked on missile analyses for NATO, the EU, the German and Austrian armed forces and other institutions in Europe. Schmucker has worked at NASA and served as a U.N. weapons inspector in Iraq.
Professor Theodore Postol is a top US rocket scientist who has in recent years emerged as a trenchant critic of some of the claims made in the US and elsewhere of certain chemical weapons incidents, especially during the war in Syria, notably the chemical weapons attack on east Ghouta in Syria in August 2013 and the alleged chemical weapons attack on Khan Sheikhoun in Syria in April 2017.
I have discussed Professor Postol’s criticisms of the scenario claimed by the US government for the Khan Sheikhoun attack at length here.
In discussing the North Korean missile programme Postol as a rocket scientist is in his element as are his two co-authors, Markus Schiller and Robert Schmucker. This report should therefore be treated as more authoritative than any other report or comment which has appeared in public about the North Korean missile programme to date.
Postol and his two co-authors say that the Hwasong-14 missile does not have the range to reach the continental US carrying the sort of nuclear warhead the North Koreans are likely to have. They also say that the way the two launches of the Hwasong-14 were carried out was deliberately intended to convey a misleading impression that the missile has a greater range with a nuclear warhead than it actually does.
Postol and his two co-authors also describe the Hwasong-14 not as an entirely indigenous North Korean product, but rather as a skilful and very well worked out lash-up of former Soviet rocket engines that the North Koreans have somehow managed to get hold of after the USSR broke up.
The source of the most important and powerful of these rocket engines is identified as a manufacturing plant in Ukraine, though Postol and his co-authors do not say that it was Ukraine which supplied North Korea with these rocket engines.
Turning first to the capabilities and specifically the range of the Hwasong-14, this is what Postol and his co-authors have to say about it
On July 3, 2017, while Americans were preparing for the 241st celebration of the Declaration of Independence, a lone rocket rose from North Korea on a near-vertical trajectory. After five to six minutes of powered flight, the second stage of the missile shut down and coasted to an altitude of about 2,720 kilometers. It then fell back to Earth, reentering the atmosphere above the Sea of Japan some 900 kilometers to the east of where it had launched. The rocket’s upper stage coasted in freefall for about 32 minutes, and the overall time-of-flight, from launch to atmospheric reentry, was about 37 minutes. The launch occurred at 8:39 p.m., United States’ Eastern time. Within hours, the news of the launch was trumpeted by the US mainstream press: North Korea had flown an intercontinental ballistic missile (ICBM), a missile that could carry nuclear warheads to Anchorage, Alaska, and to the continental United States as well!
But the Western press apparently did not know one crucial fact: The rocket carried a reduced payload and, therefore, was able to reach a much higher altitude than would have been possible if it had instead carried the weight associated with the type of first-generation atomic bomb North Korea might possess. Experts quoted by the press apparently assumed that the rocket had carried a payload large enough to simulate the weight of such an atomic bomb, in the process incorrectly assigning a near-ICBM status to a rocket that was in reality far less capable.
Only three and a half weeks later, on July 28, there was a second launch of the same type of missile, this time at night, Korean time. The rocket flew approximately the same powered flight trajectory that it had on July 3 (or July 4 in North Korea), this time, however, reaching a higher altitude—a reported 3,725 kilometers. This longer flight path led to yet more unwarranted conclusions that the continental United States was now directly under threat of nuclear attack by North Korea. Actually, however, in this second case, by our calculations, the second stage of the so-called ICBM carried an even smaller payload and tumbled into the atmosphere at night over the Sea of Japan. The spectacular night-reentry of the rocket—what was almost certainly the heavy front-end of the nearly empty upper stage—created an impressive meteoric display that some experts mistook for the breakup of a failed warhead reentry vehicle.
From the point of view of North Korean political leadership, the general reaction to the July 4 and July 28 launches could not have been better. The world suddenly believed that the North Koreans had an ICBM that could reach the West Coast of the United States and beyond. But calculations we have made—based on detailed study of the type and size of the rocket motors used, the flight times of the stages of the rockets, the propellant likely used, and other technical factors—indicate that these rockets actually carried very small payloads that were nowhere near the weight of a nuclear warhead of the type North Korea could have, or could eventually have. These small payloads allowed the rockets to be lofted to far higher altitudes than they would have if loaded with a much-heavier warhead, creating the impression that North Korea was on the cusp of achieving ICBM capability.
In reality, the North Korean rocket fired twice last month—the Hwasong-14—is a “sub-level” ICBM that will not be able to deliver nuclear warheads to the continental United States. Our analysis shows that the current variant of the Hwasong-14 may not even be capable of delivering a first-generation nuclear warhead to Anchorage, Alaska, although such a possibility cannot be categorically ruled out. But even if North Korea is now capable of fabricating a relatively light-weight, “miniaturized” atomic bomb that can survive the extreme reentry environments of long-range rocket delivery, it will, with certainty, not be able to deliver such an atomic bomb to the lower 48 states of the United States with the rocket tested on July 3 and July 28.
The report is able to arrive at the firm conclusion that the missile carried during both its launches a very light payload by comparing the known parameters of the missile drawn from open sources (specifically its size and layout) and from what is known of the rocket engines which it uses – which it turns out is substantial – with the missile’s actual performance during the two tests.
Here is what the report says about the size, layout and performance of the Hwasong-14 missile
Like any missile system, the actual lifting and range capability of the Hwasong-14 depends on many technical details. Among these are the type of fuel burned by the missile, the efficiency of its rocket motors, the total amount of propellant carried in each stage, the weight of the missile’s airframe, and the weight of different components, including rocket motors, plumbing, guidance and control systems, and the like.
In the case of the Hwasong-14, almost all of the critical parameters that ultimately determine the rocket’s ability to carry a payload-weight to a given range can be deduced from photographs, videos of its initial powered flight, engineering knowledge of rocket systems, and specific other engineering information that can be determined by other observations of the missile and its motor components.
For example, the performance characteristics of the main rocket motor that powers the first stage are well known. This is in part because the rocket motor has been unambiguously identified as derived from components of a well-known family of Russian rocket motors. The type of propellant used by this family of motors is also known—unsymmetrical dimethylhydrazine (UDMH) and nitrogen tetroxide (NTO), a highly energetic propellant combination used extensively in Russian rocket systems.
The dimensions of the Hwasong-14 are readily determined from photographs of the missile and its length, as measured relative to the known length of the Chinese-made vehicle that carries it. Since the density of the propellant is known, and the dimensions of the rocket stages and the functions of the different sections of the rocket stages are easily identified, very good estimates of the weights of the stages, airframes and rocket motors can be deduced from simple volumetric analysis and knowledge of design features. Although many of the refined details of the rocket may not be known, the general information of the type described above provides quite good estimates of how well the rocket will perform.
These data lead to an overall weight estimate of roughly 37 metric tons for the Hwasong-14. The known characteristics of the main first-stage rocket motor, and the observed rate of acceleration of the rocket at launch, result in a highly constrained check on the missile model we created to estimate its overall range and payload performance.
One critical parameter of the Hwasong-14 is not yet known with certainty: the exact powered flight time of the second stage. This parameter is an important factor in determining the overall performance of the Hwasong-14, due to a phenomenon known among rocket engineers as “gravitational losses” during powered flight. To perhaps oversimplify the physics involved, the longer the rocket motor burns against the gravitational pull of the Earth, the less efficiently it accelerates its payload to a final speed. But two articles in The Diplomat magazine have included flight times for the second stages of the rockets that North Korea launched in July. Two independent sources have confirmed those times to us as accurate.
And here is what the report says about the performance of the missile during the two tests and the conclusions which can be drawn from this based on what is known about its dimensions, layout and engines
In each of the two North Korean tests in July, the rockets were fired on a trajectory that sent them to high altitudes; on these trajectories, the rockets travelled relatively short horizontal distances. But after the tests, analysts projected the maximum range the rockets could have traveled by assuming that they could have been placed on trajectories that would result in a maximum achievable range, rather than a maximum achievable altitude. For example, the 2,720-kilometer altitude achieved by the July 3 rocket was determined by its burnout speed. If it is assumed that the rocket could achieve roughly the same burnout speed on a trajectory that is shaped for maximum range, it would be sufficient to carry the payload to Anchorage, Alaska.
In the case of the July 28 test, the same rocket achieved a higher burnout speed and a higher altitude—about 3,725 kilometers. If it were again assumed that the rocket’s trajectory is shaped for maximum range instead of maximum altitude, the new higher burnout speed would be able to carry the payload to Seattle, Washington.
Figure 1 below shows the trajectories flown on July 4 and July 28 that were misinterpreted as tests of a North Korean rocket capable of delivering atomic bombs to the continental United States.
Figure 1. The highly lofted rocket trajectories for the burnout speeds achieved in the July 4 and the July 28 tests are shown on the left side of the figure. The center and right side of the figure show alternative rocket trajectories that could instead have been flown with loft angles optimized for maximum range instead of for maximum altitude.
One question is not answered by this basic kinematic study of the July 4 and July 28 tests: How did the rocket achieve its burnout speed? That’s to say, what kind of rocket motors did it need to achieve the resulting burnout speed, what was the rocket’s launch weight, and most, important, what was the payload-weight carried by the rocket?
Figure 2 shows a summary of our estimates of the range versus the weight of atomic bomb that might be carried by a Hwasong-14 missile, derived from our technical analysis of the Hwasong-14’s weight and propulsive capabilities and the likely weight of a North Korean nuclear warhead.
The analysis results summarized in the graph are for two different “designs” of the Hwasong-14.
The first design uses published information about the powered flight time of the second stages of the rockets and is reflected by the red curves in Figure 2. Those two curves correspond to reported second-stage flight times of 224 and 233 seconds for the two rocket tests. We have received two independent confirmations of these published flight times from sources that we believe to be reliable. As those curves show, if the North Koreans have achieved the capability of creating a missile warhead as light-weight as those used by the Chinese and Pakistani militaries—no small feat for a country with means as limited as North Korea’s—the two missiles fired in July could carry that missile roughly 6,000 kilometers, approximately the distance to Anchorage, Alaska. The missiles simply could not carry such a warhead to the lower 48 states.
The second design—reflected by the blue curves in Figure 2—assumes that the North Koreans actually use more efficient rocket motors than are indicated by the information published in major media about the powered flight trajectory of the second upper stage. In this second design, we assumed that the rocket’s upper stage would be powered by rocket motors similar to those with characteristics demonstrated in the top stages of the North Korean Unha-3 and the Iranian Safir Satellite Launch Vehicle (SLV). We believe North Korea is capable of building such a variant of the Hwasong-14, and that variant could have the capability to deliver a first-generation weaponized North Korean atomic bomb to Anchorage, Alaska, and slightly beyond.
But neither variant of the Hwasong-14 we have studied could carry a first-generation weaponized North Korean atomic bomb to any part of the continental United States beyond Alaska.
The report engages in an extensive discussion of the likely weight of the sort of nuclear warhead that North Korea might be likely to have.
Its conclusion based on information drawn from the Chinese and Pakistani nuclear programmes and from information provided by the North Koreans themselves are that a current North Korean nuclear warhead is unlikely to weigh less than 500 kg.
On that assumption the authors conclude that the Hwasong-14 cannot reach the continental US with a nuclear warhead of the weight North Korea is likely to have, and would not be able to reach most of the continental US even if North Korea were to develop a nuclear warhead with a lighter weight, which however they think unlikely in the short term.
In passing I should say that this assessment of the limited range of the Hwasong-14 missile accords with what the Russians are saying about the missile. They dispute some of the claims made about the alleged performance of the missile during its two test flights. They say that the Hwasong-14 is an intermediate range missile, not an intercontinental ballistic missile.
It is possible that one reason why the Russians have been able to come to a more accurate assessment of the Hwasong-14’s capabilities than have other observers is because the Russians are very familiar with its engines.
It turns out that these are not engines designed and built in North Korea but old Soviet rocket engines which the North Koreans have managed to get hold and have skilfully modified to build the Hwasong-14.
This leads into what is perhaps the most interesting part the report, which identifies the Soviet rocket engines the Hwasong-14 uses, and which discusses its capabilities.
Careful examination shows that the first stage of the Hwasong-14 is powered by a large single rocket motor supported by 4 small “vernier” motors that are used to change the direction of the rocket during powered flight and to maintain its vertical stability during its initial lift-off and vertical acceleration. North Korea has also released videos of tests of the Hwasong-14 rocket motor (shown firing on a test stand in Figure 4).
We have identified this rocket motor as a being derived from a family of Russian rocket motors known as the RD-250 or RD-251. The original motors used six thrust chambers fed by three turbo pumps to together generate roughly about 240 tons (about 530,000 pounds) of lift.
The North Koreans probably obtained this motor and many others as part of a vast shipment of rocket components to North Korea that occurred in the late 1980s and early 1990s during the simultaneous disintegration of the national economy and political system of the Soviet Union. Until recently, almost all of the liquid-propellant motors seen in North Korea’s rockets could be traced back to the Makayev Institute, a vast and highly capable organization that was responsible for the design of all types of Soviet ballistic missiles. Because of the prominent role of Makayev in Soviet ballistic missile production, this institute would have had large numbers of rocket motors in storage that were used to build various models of SCUDs and the SS-N-6 submarine-launched ballistic missile (aka R-27) used on Russian Yankee class submarines.
The newest Russian rocket motor we have identified in the North Korean arsenal, derived from the RD-250/251 and used in the Hwasong-14, is not from the Makayev Institute, but from an entirely different major rocket motor manufacturer, NPO Energomash, which supported the OKB-456 Design Bureau in the Soviet Union. This rocket motor was associated with rocket and space launch vehicles produced in Ukraine. The presence of RD-250/251 rocket components in a new North Korean rocket raises new and potentially ominous questions about the variety and extent to which Soviet rocket motors might have been obtained by North Korea during the collapse of the Soviet Union.
The adaptation that North Korean engineers have worked, using components from the powerful RD 250/251 rocket motor, can be appreciated by examining Figure 5. The original RD 250/251 was a rocket motor that consisted of six thrust chambers, driven by three powerful turbo pumps. This rocket engine can be seen in the image on the left in figure 5.
Each of the three turbo pumps in the original rocket engine was nested between two thrust chambers, at a height below the combustion chamber and above the gas exhaust nozzle of each thrust chamber. This clever design made it possible to shorten the length of the rocket motor compartment and to reduce the overall length of the first stage of a rocket.
The image on the right in figure 5 is an enlargement taken from Figure 4, a photo of the Hwasong-14 rocket motor firing on a test stand. The outline of the motor’s thrust chamber is shown in a silhouette overlay and the location of the turbopump next to the single thrust chamber is shown to be exactly at the height of the turbopump in the RD 250/251 motor complex. It is clear that the final rocket motor mounted in the Hwasong-14 has this single powerful turbopump feeding propellant to both the main rocket motor and the four smaller vernier motors used to control the direction of the missile.
(bold italics added)
In other words media reports that North Korea is using imported Ukrainian rocket engines are almost certainly true. The real question is not whether North Korea is using rocket engines that were built in Ukraine; it is when and how it got hold of these engines.
Postol and his co-authors wisely limit themselves to saying that this would have been after the USSR broke up, which is of course true. They do not say that the North Koreans obtained rocket engines from Ukraine recently. However that possibility cannot be excluded.
It seems North Korea did obtain old Soviet rocket engines from Egypt and the former USSR in the late 1980s and the early 1990s, and that these have been used in North Korean missiles for some time.
However some at least of the engines which are being used by the Hwasong-14 appear to be of a more powerful and more advanced design than the Soviet rocket engines the North Koreans have used previously, which may be a sign that they were obtained more recently.
It is important to stress that at the moment this is surmise. The Russian government has said it cannot confirm that North Korean obtained rocket engines recently from Ukraine. It is important not to jump conclusions, but the facts certainly suggest that an investigation is in order (see below).
Before discussing this, I would add that on the strength of what Professor Postol and his co-authors say in their report, it may not just have been just rocket engines that North Korea imported, but design skills as well
The design indicates a well-thought-out approach to a completely new missile that was not seen in public until the launch of the Hwasong-12, which was essentially a test aimed at proving the functionality of the first stage of the two-stage Hwasong-14. It is a remarkable achievement in itself that North Korea has been able to master the use of these components well enough to be able to adapt them to their special purposes.
To me this comment looks like a hint that the North Koreans have not only imported the rocket engines they used in the Hwasong-14, but that they have obtained help from scientists and engineers familiar with these engines.
If so then that once again points to Ukraine, though let me reiterate again that this is surmise not proof.
The report of Professor Postol and his co-authors explains some of the mysteries behind the sudden and unexpected appearance of the Hwasong-14.
Russian and Chinese rocket specialists had previously estimated that North Korea would not have a workable ICBM before 2040.
It seems that this assessment, which was based on the pace of North Korea’s indigenous ballistic missile programme, was factually true.
However the North Koreans have managed to shorten the time frame radically by somehow managing to import Soviet rocket engines and expertise from abroad, enabling them to produce far sooner than anyone expected the missile known as the Hwasong-14.
That presumably explains the truly remarkable fact that both Hwasong-14 launches were successful, something which is almost unprecedented in new rocket designs.
The reason for that is that in reality the Hwasong-14 is not properly speaking a new rocket design. Rather it is an extrapolation of already mature and reliable rocket technology, put together with the help of a team of engineers and designers who may have been already fully familiar with the technology.
In a separate article Markus Schiller, one of the co-authors of the report, sets out the implications
The North Korean Missile Threat Is Largely a Bluff
- North Korea has likely launched Soviet/Russian-made missiles (that are old but proven designs) to maximize the appearance of performance.
- North Korea may never have tested missiles from its own production, and any such indigenous missiles cannot have noteworthy reliability or accuracy.
- It cannot be ruled out that North Korea has nuclear warhead designs for its missiles, but without actual testing, the reliability of these warheads has to be assumed to be low.
- The main purpose of the program seems to be political — to create the impression of a serious missile threat and thereby gain strategic leverage, fortify the North Korean regime’s domestic power, and deter other countries, particularly the Republic of Korea and the United States, from military action.
- North Korea should be considered to possess no real long-range missile threat, but steps should be taken to defend against a conventional short-range threat.
- Concerns about North Korea’s missile launches are overblown: Every launch further depletes the limited North Korean arsenals, and North Korea gains no real experience from these events. Since the purpose of the launches seems to be political, the United States and other nations should downplay or even ignore them.
- A variety of avenues of investigation should be pursued to gain more information about the North Korean missile program
(bold italics added)
The overall conclusion of these studies can therefore be summed up by saying that the Hwasong-14 is not the culmination of a longstanding ballistic missile programme embarked on and pursued by North Korea over many years and as such represents only a limited threat to the US.
Rather the Hwasong-14 is essentially a propaganda weapon created by North Korea in order to convey the impression that it is now a major nuclear power. In effect it is a demonstration missile using a finite number of ex-Soviet rocket engines North Korea has somehow managed to acquire, and which North Korea launches from time to time for demonstration effect.
However with every launch the stock of imported rocket engines used by the Hwasong-14 is depleted, so that North Korea’s Hwasong-14 missile arsenal, far from getting bigger, is actually getting smaller.
This conclusion is not just surmise. The co-authors of the report – Professor Postol, Markus Schiller and Robert Schmuker – are top experts in this field and they must be presumed to know what they are talking about. Their study of the Hwasong-14 and their identification of the Soviet rocket engines it uses should be treated as definitive.
It is not in fact difficult to create a plausible scenario to explain all of this.
Whilst Kim Jong-il was North Korea’s Great Leader North Korea had a genuine ballistic missile programme albeit one which was initially based on reverse engineering of Soviet Scud missile technology imported in the 1980s from Egypt.
It was this programme which led to the Taepodong -2 missile and the Unha-3 space rocket, and whose steady incremental advance led Russian, Chinese and US scientists to assess that North Korea would not have a working ICBM capable of reaching the continental US before 2040.
However Kim Jong-il died in 2011 and was replaced by the young and impatient Kim Jong-un, who was not satisfied with the slow pace of this programme.
Possibly following the failure of the second Unha-3 launch test in April 2012, a decision was therefore made to put together in the shortest time possible a useable long range missile – if not an ICBM something which could be plausibly passed off as one – by importing expertise and rocket engines from abroad.
In April 2017 this bore fruit with the appearance of the Hwasong-12 during the “Day of the Sun” Parade in Pyongyang, and subsequently with the launches in July of the closely related Hwasong-14.
Meanwhile the main line of North Korean rocket development focused on the Taepodong-2 and the Unha-3 continues, albeit at a much slower and more incremental pace, with a fourth successful test launch of the Unha-3 in February 2016.
That it is Kim Jong-un who is the driving force behind the Hwasong-14 programme, and that it is his impatience and determination which has led to it, is strongly suggested by the extent to which he has publicly associated himself with it.
Here he is for example, clearly visible pacing impatiently near the Hwasong-14 and its associated Chinese built launch vehicle, in this video the North Koreans have published of the Hwasong-14’s first launch on 4th July 2017
Kim Jong-un can also be clearly seen closely examining the Hwasong-14 and its associated launch vehicle just before its first launch in the picture which accompanies this article.
This begs the question of the extent to which Kim Jong-un himself understands the nature of what the Hwasong-14 is – that it is a clever lash-up made up of old Soviet components rather than a fully indigenous North Korean design – and that contrary to North Korean boasts North Korea is not yet a fully capable nuclear power.
A plausible scenario might be that faced with urgent demands for an ICBM from their new young and hot-tempered Great Leader, the managers of the North Korean ballistic missile programme were too frightened to tell him that creating such an ICBM is beyond North Korea’s capabilities, and that they set out to appease him by cobbling together what they could pass off to him as an ICBM by getting foreign expertise and components to help them do it.
In that case the Hwasong-14 is first and foremost a bluff aimed at Kim Jong-un as it is a bluff aimed at the US.
The alternative scenario is that Kim Jong-un is fully informed about all aspects of the Hwasong-14 programme but nonetheless ordered the building of the Hwasong-14 using foreign expertise and technology even though doing so contradicts his grandfather’s Juche ideology, because he feels he needs to convey at least the impression that he has an ICBM so as to gain leverage over China and the US.
The extent to which Kim Jong-un knows the true position is crucial, since it largely determines what will happen next. If he does not know the limitations of the Hwasong-14 but genuinely believes that he has an actual ICBM capability greater than the one he has, than there is a greater risk that he might overplay his hand, in much the same way that Saddam Hussein did in 1990 when he invaded Kuwait under the impression that his nuclear weapons programme was far more advanced than it actually was.
Unfortunately we simply do not have the information necessary to answer this question, but for what it’s worth my opinion is that Kim Jong-un – who has proved very surefooted over the last few months – knows exactly what is going on and what he is doing, and that points to his understanding fully what the Hwasong-14 is.
The second big question is from where North Korea could have obtained the rocket engines and possibly the expertise needed to build the Hwasong-14?
There is a strong circumstantial case that it was Ukraine because it is not obvious what other source it could have been.
If the North Koreans had been in possession of the more powerful rocket engines used in the Hwasong-14 earlier, then presumably they would have used them previously in some way. That suggests that they acquired these rocket engines recently and not at the time the USSR broke up.
In that case, since it is hardly conceivable that they could have obtained these rocket engines from Russia – which not only does not build these rocket engines, but which carefully monitors what rocket technology it exports – the only plausible source for these engines does appear to be Ukraine.
Again it is possible to suggest a plausible scenario in which staff and engineers at Yuzhmash – the factory that builds rocket engines in Ukraine – becoming increasingly desperate as the factory’s orders dried up because of the conflict with Russia (Yuzhmash’s only serious customer), chose to sell their rocket engines and expertise to whatever other customers turned up without asking too many questions in order to stay in business. Probably they did not realise that the North Koreans were the ultimate customers, because the North Koreans probably acted through a chain of middlemen and cutouts to conceal their identity.
Again it should be stressed that this is supposition rather than fact, though it is supposition which is based on fact given that the Hwasong-14 missile uses Ukrainian made rocket engines.
Certainly there is a case to look into. Despite heated denials the Ukrainian authorities have apparently ordered an investigation, though given the political realities in Ukraine today one has to be skeptical how far that will go.
As previously reported by The Duran, US Defense Secretary General Mattis is due to visit Ukraine on 24th August 2017 in what looks like a hurriedly arranged visit for which no real explanation has been provided.
Could it be that the real reason for General Mattis going to Ukraine is that he intends to ask there some hard questions about the origin of the Ukrainian made engines used by the Hwasong-14?