Continued from “A New ICBM for North Korea?”
Some commentators initially believed that the Mod 1 and Mod 2 missiles shared the same first stage. There are, in fact, a number of similarities, but a close examination of the missile reveals that the first stage of the KN-08 Mod 2 is significantly longer than that of the KN-08 Mod 1.
Each North Korean missile contains a number of externally visible elements that offer clues to the configuration. A careful examination of the location of features such as draining ports, structural markings, and apparent separation planes suggests that the new first stage is roughly 10.5 meters long, more than 3 meters longer than the first stage of the KN-08 Mod 1.
The base section, containing the engines, is largely unchanged. There is, in particular, no evidence to suggest that this is secretly the first stage from a Russian R-29 SLBM, as others have suggested. With a submerged engine design, the propellant drain port would have to be much lower on the missile. And there is no evidence that the DPRK has ever acquired the R-29 missile or the technology needed to build it. But while the engines may remain the same as in the Mod 1, the fuel and oxidizer tanks have been stretched. The elongated first stage is now nearly optimal for a two-stage missile, which is probably not a coincidence.