Jeffrey LewisSchmucker & Schiller on the SS-N-6

One of the discussions that Markus Schiller and I have about North Korea’s ballistic missile program centers on the SS-N-6 aka BM-25 aka Musudan ballistic missile.  I was skeptical of the missile at first — although we’ve subsequently seen a larger version on parade, a second stage on the Unha that looks like an SS-N-6, and NASIC has reported that North Korea has deployed the missile.  There are also reports of static engine tests.

Markus and Robert Schmucker, however, still have their doubts.  I am posting a paper, Explaining the Musudan: New Insights on the North Korean SS-N-6,  in which they argue that North Korea’s SS-N-6 capabilities are rather less than we commonly believe.

I am not so sure, but I am happy to host that discussion in the comments.


  1. John Schilling (History)

    The Safir second stage is pretty clearly based on the SS-N-6/R-27 verniers, and I don’t think anyone has found evidence of a direct Iran/Russia link in ballistic missile technology. So there’s pretty compelling evidence that the North Koreans got their hands on at least enough SS-N-6 technology to pass useful parts of the kit on to Iran. Which is not the same as proof of North Korea having complete working missiles, but I am inclined to dismiss the scenarios where the Nork R-27s are a complete hoax.

    Misdirection is a definite possibility, or more precisely a wide range of possibilities. I want to think on this some more.

  2. Tal Inbar (History)

    So, just to check if I understood correctly – according to the article, the “BM-25 is a mockup, it has NO actual connection to the R-27 (other than trying to look similar), NK has NO actual R-27 (let alone a working, enlarged copy) and if there IS a real BM-25 it is an enlarged Nodong.


  3. Markus Schiller (History)

    It seems that there is some confusion on our findings. So please let me try to clarify some things. (There is a summary at the end of this long post)

    The general consensus in open source literature is: There is SS-N-6 technology in NK, and the Musudan is based on it.

    With the paper, Robert and I tried to figure out

    1) why “everyone knows it”,
    2) if this general consensus is consistent with what we really know,
    3) and what our findings might mean.

    If you start looking into 1), your first impression by reading open source literature is either that the Musudan is based on the SS-N-6 because everybody knows that NK mastered SS-N-6 technology, or that NK mastered SS-N-6 technology because everybody knows that the Musudan is based on the SS-N-6. This is not a good starting point for further analysis. Remember: In assessments, it is way too easy for the author to confuse “we know” with “we think we know”!

    If you dig deeper, you will find reports of the BM-25 transfer to Iran, of the SS-N-6 parts in the Safir, of static engine tests, of the Musudan being deployed in NK, and so on.

    But what does this tell us about the Musudan itself?

    Static engine tests could be done for any rocket, with any rocket engine. We do not know for sure that the Musudan was involved, or that they tested SS-N-6 engines. It might well be that the Unha second stage was tested at these static engine tests, for example.

    That SS-N-6 parts showed up in Iran is interesting, and this detail fits into the “NK sells SS-N-6” hypothesis. But we can just as easily assume that the parts were sold on the Russian black market in the 1990s, for example (@John: there were links between Russia and Iran at that time – see “The Dead Hand” by David E. Hoffman). Therefore, that the Safir uses SS-N-6 elements tells us nothing about the Musudan.

    Then there are reports of Musudan deployment. This makes it more likely that a Musudan missile really exists, but it tells us nothing about what the missile looks like.

    This leaves us with the three mentioned pieces of information: The SS-N-6 related Unha stage, the BM-25 transfer to Iran, and the Musudan at the parades.

    – The Unha second stage turned out not to be related to the SS-N-6.
    – The Musudan at the parades were mock-ups, with details that were different from the SS-N-6.
    – The knowledge on the transfer of the so-called BM-25 is very poor.

    This is all that we really know (others might know more). So, to proceed to 2), is this consistent with a SS-N-6 based Musudan, produced in NK?

    The answer is: Yes. None of the three insights is a showstopper for the SS-N-6-based Musudan. But: If you assume that NK does not possess SS-N-6 technology, the three insights are also consistent.

    This leads us to 3), which is the meaning of our findings.

    With that knowledge, it cannot be excluded that the Musudan uses SS-N-6 technology. For an engineer, it just seems incredible how NK should have managed to do this, and if they did, it makes no sense to stick to Scud technology for the Unha.

    But everything we know is even more plausible assuming that NK has not used SS-N-6 technology in their missiles.

    According to Occam’s Razor, the latter hypothesis should be preferred for now.


    The evidence for SS-N-6 technology in NK is poor. The use of SS-N-6 technology in NK missiles is still consistent with what we know. But even if there really is a Musudan missile in NK, right now it seems more plausible to assume that NK is still limited to Scud technology.

    In no way does that mean that NK is harmless. But we should be aware of what we really know, and always dare to revisit well-known truths and question them.

    • John Schilling (History)

      Briefly, I do not consider the hypothesis of a Safir using black-market rocket parts from the 1990s to be very credible. Rocketry is more than just parts, but knowing how to use them – and much of that is “tribal knowledge” that you can really only get by talking to someone from the right tribe at the righ time. Barring active Russo-Iranian collaboration in the past five years or so, that argues strongly for a North Korean link in the Safir/SS-N-6 chain.

      As you note, this does not mean that the Musudan is an SS-N-6.

  4. George William Herbert (History)

    I have a nonzero hope that someone with a good submarine and ROV was hanging out in the various Unha third stage splashdown zones, and at least got photos…

    Barring that, the only seriously disambiguating factors are very sketchy visuals, and leaks from intelligence agencies (who are not leaking enough details to know the quality level of the source material).

    John’s observation that it would be hard for SS-N-6 verniers to have showed up in Iran flight vehicles without tech transfer from someone who “got them” is good. Just buying a missile on the black market does not equal being able to produce them, by any means.

    • George William Herbert (History)

      Look for some offline emails this afternoon, but…

      For the moment, consider a R-27 derived Unha-3 upper stage, which was redesigned to avoid a common bulkhead (for not yet clear reasons), but otherwise structurally similar other than adding one tank bulkhead and a short interstage.

      I also have an alternate structural explanation that retains a common bulkhead but explains the stringers, but it’s weird.