A couple weeks ago, Benn Tannenbaum invited Ted Postol to come down to Washington. Ted gave a fascinating talk, in which he argued that the second stage of the Unha may be a re-purposed SS-N-6.
This is a plausible answer to the BM-25 — the North Korean bought kits to use as a second stage of the Taepodong series.
David Wright and Ted have a provocative article in the Bulletin suggesting that the Unha-2 “second stage appears identical to the single-stage Soviet R-27 sea-launched ballistic missile, called the SS-N-6 in the United States, which the Soviet Union first deployed in 1968.”
First the bad news: An SS-N-6 second stage massively increases the range-payload curve (doing away with the golf ball of death), putting CONUS within range of a 1 ton payload from North Korea.
Now, the good news: North Korea can’t indigenously manufacture the second stage, so if we can secure the rest of the SS-N-6 kits components (and cut off external assistance), the North Korea ICBM program is at a technological dead-end:
Analysis of the Taepodong-1 and Unha-2 launchers strongly suggests that they may be designed and built around components of Soviet missiles. The apparent lack of testing of these components by North Korea suggests that they aren’t indigenously produced systems but are existing components that North Korea has been able to combine to build multistage launchers. The Taepodong-1 appears to have used a modified Nodong missile for the first stage; a modified engine from a Soviet surface-to-air missile for the second stage; and the engine from a solid-fueled Soviet SS-21 tactical missile for the third stage. As noted above, the second stage of the Unha-2 appears to be a modified SS-N-6 missile, which was produced by the Makeyev bureau in the 1960s.
It’s possible that North Korea learned, with significant Russian assistance, to manufacture Scuds and Nodongs and is therefore not limited in its number of these missiles, assuming it can acquire the necessary materials. But this is much less likely for the SS-N-6, which is a far more advanced system due to its use of highly optimized rocket motors, very energetic propellant, and a complex airframe fabricated from aluminum alloy.
None of this evidence is conclusive, but because it has important policy implications, it should be a high priority for the United States to assess it and work with Russia to determine what technical assistance and components North Korea may have received.