Thursday, 31 August 2017

North Korea's 29 August Hwasong-12 test with Japan fly-over: did it go as planned?

image: KCNA
It are hectic times for those (like this author) interested in the North Korean rocketry program. The past months have seen a steady series of increasingly bold missile tests (along with a threath of test-firing missiles towards Guam), that have been the subject of three earlier posts on this blog the past months.

And now a new one has occurred, and it is perhaps the boldest of these test flights so far. Last Thursday, 29 August 2017, at 20:57 UT, North Korea launched a Hwasong-12 MRBM on a trajectory over Japan: a politically bold move that caused air-raid sirens to go off in Northern Japan.

images: KCNA

Western military sources say that the missile was fired from Pyongyang Sunan airfield. It reportedly travelled 2700 km, crossing over Hokkaido, coming down in the Pacific Ocean about 1180 km from Cape Erimo in southeast Hokkaido, Japan. Apogee of the trajectory is quoted as 550 km.

This allows us to produce the trajectory reconstruction below (with some leeway as the quoted ranges are probably balpark figures). It shows that the missile crossed Japan over the southern tip of Hokkaido, a trajectory that seems designed to minimize Japanese landmass overflown, mitigating risk levels. The two red circles on the second map are depicting a 2700 km range around Pyongyang Sunan and 1180 km range around Cape Erimo. Where they are closest, is the resulting impact point (near 41.92 N, 157.56 E). Using STK I get a flight-time of ~14 minutes.

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That odd-looking second of the two maps above is based on an interesting photograph published by the North Korean State News Agency KCNA. It shows an exuberant Kim Jong Un sitting on a desk with a map in front of him:
image: KCNA

We have recently seen more of this kind of shots from KCNA published after previous tests, and they often yield interesting information. In this case, the interesting detail is that a trajectory appears to be depicted on the map, as a thin line (the arc above it ending at the same point likely is a 3D representation):

If the sketched line indeed is the intended trajectory, then the interesting point of it is that it does not match the observed trajectory according to Western military sources.

I used my GIS skills to georeference the map on the image (with QGIS). Like in the case of the 'Guam map', the low resolution of the image and very oblique angle of te map on it make this a challenge, and the georeferencing obviously is not perfect - but good enough for some conclusions. This is the result (look for the vague line that possibly represents a trajectory on the image):

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Here is the same map but with annotations added, and with the trajectory sketched on the map (white line) and the actual observed trajectory (black dashed line):

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It is immediately obvious that the two trajectories do not match well. The trajectory (if it is one) sketched on the Kim Jong Un map is located more to the south, and indicates a larger range, about 3300 km (interestingly, it does conform to a real ballistic trajectory with earth rotation and curvature taken into account, unlike the straight line drawn on the infamous "Guam map").

(the second map shows exactly the same map area, but with a DEM and country shapefile as background. It shows you how the topography matches that on the georectified map from the photograph)

The difference between the two trajectories amounts to a range difference of 600 km and a 45 km difference in apogee. It represents a difference in launch azimuth of 6 degrees and of 3.7 degrees in launch elevation. It points to an underperformance of around 0.4 km/s in the missile's burnout speed.

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It is interesting to note that while North Korea for some previous tests (and their proposed Guam shot) published very accurate figures for range, flight time and apogee, they did not do that this time. It is also interesting to note that some Western military sources report that the missile "broke into three pieces".

So there are multiple indications that the test did perhaps not go entirely as planned, with an underperformance of the rocket engine and an error in launch direction, and perhaps structural failure. This would imply that the targetting of the Hwasong-12 is not quite fail-safe yet, which has implications for Kim Jong Un's proposed Guam enveloping missile demonstration.

This was the first test of the Hwasong-12 on a "normal" trajectory and it shows why it is important for North Korea to test its missiles on such a normal operational, rather than a 'lofted' trajectory: it is a different regime of stress on the missile and has the engines perform under more realistic conditions than on a 'lofted' trajectory. Errors in targetting and missile performance become more apparent.

For North Korea to do such tests on a "normal" trajectory for its MRBM's and ICBM's, they have to fly it over Japan. We are going to see more of this kind of tests the coming months is my prediction.

Update 31 Aug 2017:

(1) The 38 North blog has an interesting post suggesting the possible failure of a post-boost vehicle.
(2) South Korean and US military analysts appear to come to the same analytical conclusions as I did, according to this Korean news bulletin
(3) As Ankit Panda rightfully remarked, the situation drawn on Kim Jong Un's map need not comply to reality. It could be merely meant as a propaganda message (3300 km is roughly the distance from the launch site to Guam).

Update 1 Sep 2017:

A further follow-on post is here, discussing how the map contains two veiled threaths, to Guam and to Pearl Harbour.

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