Is North Korea’s Hwasong-14 ICBM Really Powered by the Soviet RD-250 Engine? Beware the Theory Ladenness of Observation

When North Korea statically tested the Pektusan or March 18 Revolution engine, which forms the main engine of the Hwasong-12 IRBM and the main engine of the first booster stage of the Hwasong-14 ICBM, Kim Jong Un stated that its successful development followed the dispensing of conservatism, dogmatism and formalism in North Korea’s missile programme.

I believe this statement to be the key to explaining North Korea’s ICBM success, a point to which I return. Michael Elleman, in a very careful and analytically precise exposition, argues that the key to North Korea’s success can be found in the Soviet RD-250 engine, which when clustered into three twin engine chambers, a configuration known as the RD-251, formed the basis of the Soviet SS-9 ICBM.

North Korea, through espionage and collusion with rougue elements in the former Soviet military-industrial complex, came to acquire key parts and know how regarding the RD-250 and that is how North Korea managed to develop an ICBM.

Elleman’s thesis on the RD-250 is one of three hypotheses regarding the Hwasong-14 to have been developed by analysts.
Those three are (a) North Korea has an ICBM capability, or still needs some more work but nonetheless the foundational pillars are there, and that ICBM capability was largely developed through espionage (b) North Korea doesn’t, yet, really have an ICBM able to deliver a nuclear payload and so the Hwasong-12 and the Hwasong-14 does not undermine “the bluff hypothesis” namely that North Korea is exaggerating its capabilities for political effect and (c) North Korea has an ICBM capability, or still needs a little bit more time but essentially the finish line fast approaches, and that ICBM capability was largely indigenously developed.

I think that, from what I have seen (and I am open to the other alternatives if presented with sufficient evidence), hypothesis (c) is more apt to be correct.

I would like to discuss Elleman’s thesis here.

I have had an interest in the philosophy of science, and I have always maintained that scientists need to be mindful of the philosophy of science lest they become too concerned with their own technical problems so missing the bigger picture, as it were. Richard Feynman famously stated that scientists need philosophy of science like birds need ornithology, but I think he was mistaken about that and I don’t subscribe to the view that Feynman was a good example of someone who ignored the issues.

Take a look at Feynman’s position on string theory, for example. Notice, as a quick aside, that in Feynman hagiography within the particle physics community, and beyond, his early and very strong disavowal of string theory is kind of out of the historical record.

I submit that the Elleman analysis on the RD-250 and the Hwasong-14 ICBM is a type of “theory ladenness of observation.” This is, roughly, the idea that the theoretical presuppositions of the observer influence the direction of inquiry, frequently leading to error especially of observation.///

The Elleman analysis proceeds like so

No other country has transitioned from a medium-range capability to an ICBM in such a short time. What explains this rapid progression? The answer is simple. North Korea has acquired a high-performance liquid-propellant engine (LPE) from a foreign source

This is a presupposition that influences the inquiry. There had to be a foreign source, and the key to unlocking the Hwasong-14 ICBM is to find that foreign source, which he proceeds to do so through, as stated in the paper, a process of elimination. It cannot be an engine produced in, or historically developed in, the US, France, China, Japan, India, or Iran because the Pektusan engine does not resemble any of their engines and “nor do any of these countries produce an engine that uses storable propellants and generates the thrust delivered by the Hwasong-12 and -14 LPE.”

So therefore it must be of Soviet prominence, and the Soviet engine that most resembles the Pektusan engine is the RD-250 so therefore it must be, through elimination, basically a variant of the RD-250.

Notice how powerfully the theoretical presupposition, that the Hwasong-14 has to be based on a foreign source, shapes observation?
Elleman does make an empirical error, in that the thrust of the Pektusan engine is much like a single engine chamber of China’s CZ-2 space launch vehicle, the first stage of which basically is the main booster of the DF-5 ICBM. The CZ-2 uses a four-chambered cluster, and when you divide the total thrust of the CZ-2 by four you get a single engine thrust not far off from what North Korea cites to be the thrust of the Hwasong-14 (which is not the same as the figure cited by Elleman).

The DF-5 ICBM does employ storable liquid propellant and, what’s more, those propellants are UDMH for the fuel and N2O4 for the oxidiser, the same, it would appear, as with the Hwasong-14.

It should be clear, as Elleman points out, that the RD-250 is a Glushko (the main rival to Sergei Korolev “the chief designer”) design consisting of two chambers feed by a single turbopump (when the Soyuz SLV goes “bang” prior to lift off that’s when the main booster configuration turbopump reaches a flight speed of 8000rpm).

But that’s not what you see with the Hwasong-14, that is no twin-chambers fed by a single turbopump.

How to explain this? Elleman states,

Having no demonstrated experience modifying or developing large LPE turbopumps, Pyongyang’s engineers would have been hard pressed to make the modifications themselves. Rather, the technical skills needed to modify the existing RD-250 turbopump, or fashioning a new one capable of feeding propellant to a single chamber would reside with experts with a rich history of working with the RD-250

You can see here how the underlying theoretical presupposition is driving inquiry, when, Occam’s Razor, the simplest explanation is that the Pektusan engine is pretty much indigenous. Notice that North Korea cites a thrust for the Pektusan of 80 tonnes, much the same as the twin chambered RD-250, but Elleman in the paper cites a figure for the Pektusan of half the RD-250.

You can see that figure comes from assuming flight data taken from the YouTube video of the Hwasong-12 launch, but that’s not a terribly precise way to garner key data such as this.

Now there are resemblance between the RD-250 and the Pektusan, which Elleman discusses, but the YF-20A engine that powers China’s 1st stage for the CZ-2 SLV and DF-5 ICBM, in a four engine cluster, isn’t a Glushko style twin chambered engine configuration (2 by 2 as compared to 3 by 2 for the SS-9 ICBM) fed by a single turbopump (see the header image above). Don’t forget the YF-20A does employ storable liquid propellants and that UDMH and N2O4 to boot.

In short, I am not persuaded by the Elleman analysis. When the reports on this first came out, at The Washington Post, I argued that just as likely resemblances between the RD-250 and the Pektusan engine can be explained through convergent evolution; engineers confronted with similar design problems for reaching similar performance characteristics using the same propellants likely might hit upon some similar solutions.

That’s how nature works, as Feynman would doubtless have put it.

To return to the point with which I began. Kim Jong Un’s statement is the key to understanding the success that underpins the Hwasong-14, I submit. Decipher that and you have unlocked the secret behind the Hwasong-14 ICBM.

The United States did rapidly develop an ICBM after the decision was made to do so, indeed work on the Thor IRBM and the Atlas ICBM occurred kinda in tandem. At the time the US developed what was called “concurrency,” that is using a less risk averse, dare I say it less conservative and dogmatic, approach to ICBM Research and Development which saw it test major system components concurrently rather than discretely. That carries greater risk but it offered the reward of more rapid development.

It wouldn’t surprise me that the secret to America’s rapid development of the ICBM also underpins North Korea’s surprisingly rapid development.

Just quickly, there has been a definite tendency to assume, from Joe 1, Sputnik, to Lop Nor and now North Korea that authoritarian states are not up to the scientific and engineering challenges of nuclear, rocket and space technology. The recent, rather pathetic, flops in Iraq and Libya, but also difficulties faced by North Korea previously, tended to, unjustifiably, revive this prevailing thought pattern.

I suspect that the Hwasong-14, like Joe 1 and so on, further demonstrates to us some presuppositions we have about the scientific enterprise and the way it relates to society.