This  does not look like an indigenous “Juche” development. A missile is a fusion of diverse technologies into one goal. Even more than the recent 9/3/2011  “thermonuclear” device test, it demonstrates simultaneous deployment of too many new technologies at once, with a launch record that has in the same interval switched from pathetically bad to amazingly good.

Engineering in the advanced industrialized states doesn’t work that way. Improvements in the many systems that comprise a missile are phased in, one or  a few at a time. The Hwasong-15 demonstrates:

• Gimbal based thrust vectoring, which requires a new control system. In control characteristics, it is entirely dissimilar from vernier rockets.
• A new rocket motor on those gimbals.
• An improved guidance system, which interacts with the gimbal control system.
• A new rocket structure, with different, unknown vibrational modes.

Vibration is a problem with all rockets. Stressed to the limit, they tend to vibrate and shake to the point of destruction. See pogo oscillation, just one of the many kinds. All that vibration, combined with unstudied  “poles”, i.e., singularities of the complete control system, can make a rocket turn around and come right back at you.

So  how does one control the vibrational modes, which cannot be known with authority before flight, when a new guidance system is interacting with a new control system? This kind of challenge would normally be broken into digestible pieces.

If the 9/3 nuclear test is a bought design, the possible sellers are quite limited. One naturally suspects elderly Russian scientists, with other possibilities in the countries that combine nuclear weapons with mercenary opportunity.

The possible sellers of  the missile design are more numerous. Since criminal intent can be found in developed countries, Japan cannot be excluded.

Who makes a rocket with two motors, two gimbaled engines, and a diameter close to 2.4 meters?