North Korea Tests Missile With IRBM Range Capabilitiy: Don’t Forget the Reentry Vehicle.

On Sunday May 14 North Korea tested a ballistic missile that flew 700km, for 30 minutes, and on a lofted trajectory of approximately 2000km altitude.

David Wright, a leading analyst of North Korea’s missile programme from way back (you haven’t lived unless you’ve read Wright and Kadyshev on the Nodong missile), has a nice computer model of North Korea’s missiles and his analysis of the May 14 test at The Union of Concerned Scientists is a must read.

The missile was launched from near Kusong, which is pretty close to the same place that the KN-15, a road mobile solid fuelled MRBM, was successfully tested in February 2017. A 2000km apogee with a range of 700km suggests an MET trejectory of 4500km. It is unclear at this stage what missile was tested, however the 4500km range (if tested on a MET trajectory) suggests a new type. If this missile is a 4500km solid fuelled missile then this is big news.

Therefore, assuming that the data reported by the media is correct, North Korea now is moving toward a demonstrated Intermediate Range Ballistic Missile capability. An IRBM is defined as a ballistic missile with a range of 3000 to 4500km. This would put US military bases in Guam within range of North Korean ballistic missile attack, an important development from a strategic deterrence perspective.

An IRBM aimed at Guam adds to the “use them or lose them” dynamic that makes the developing nuclear standoff on the Korean peninsula potentially destabilising, especially in a crisis.

The other thing about an IRBM, especially a solid fuelled one with a 4500km range, is that it’s a step toward an ICBM. One interesting thing about the 2000km lofted trajectory apogee is the velocity of entry of the Reentry Vehicle. The heating rate of the RV increases with the velocity of reentry. Wright has modelled this for the Musudan MRBM comparing a 3000km MET with a 1,400km lofted trajectory apogee (the parabola in red; 400km range at 1,400km altitude). The peak heating on the RV is higher for the lofted trajectory, however the total heating that the RV is subjected to is not much higher as the heating occurs over a shorter time.

North Korea is credited with not having the ability to develop a Reentry Vehicle to reliably deliver a nuclear warhead to ICBM ranges. This point was just reinforced in Senate Testimony by the Director of National Intelligence, Dan Coats. One issue that the North Koreans have here is developing an RV able to withstand the heat of reentry for an ICBM.

The rate of heat transfer on an RV is determined by pV^3, where p is the atmospheric density and V the velocity of the RV. The value of V increases significantly with missile range.

What interests me, in addition to the range of the missile tested if fired on an MET, is the reentry vehicle dynamics of an RV descending from an apogee of 2000km. This could have important implications for North Korea’s ICBM programme, given that RV dynamics is one of Pyongyang’s most oft cited limitations. The peak heat transfer on the IRBM tested today would be higher than the 1,400km lofted trajectory for the 2016 Musudan MRBM launch, however we should be mindful of the 700km range. Today’s test gives North Korea just that little bit more confidence and capability in the RV sphere too.

North Korea’s missile capabilities are growing, and diplomatic options to freeze those capabilities are narrowing. It is well past time that we took seriously the opening up diplomatic talks with North Korea without preconditions.