North Korea’s December 13 Static Hot Test of a Liquid Propelled Engine at Sohae

On December 13 North Korea announced that it had conducted a second test at the Sohae Satellite Ground, hot on the heels of the December 7 test. I had put up two posts on the first, and what we know of the second is not inconsistent with their themes. The first post is available here and the second here.

As with the first there were hints of a second, this time from analysts associated with 38North. Their analysis (December 12) was not presented in an arrangement with CNN, so it did not garner quite the same attention as the indications visible just prior to the first. In particular the analysts at 38North observed that “a 10-meter-long truck is present adjacent to one of the newer fuel/oxidizer bunkers that may be the same vehicle as seen before in this area, although moved to a new position.”

A 10-metre truck is no small thing.

Then come the test. The test was again announced by a spokesman for the Academy of Defence Science. According to the statement

Another crucial test was successfully conducted at the Sohae Satellite Launching Ground from 22:41 to 22:48 on December 13, 2019.

This statement left us with no doubt about the test’s relation to North Korea’s strategic nuclear programme

The research successes being registered by us in defence science one after another recently will be applied to further bolstering up the reliable strategic nuclear deterrent of the Democratic People’s Republic of Korea.

Many provided instant analysis on Twitter parsing this statement as saying the test was a reliability test of a liquid propelled missile engine. But notice that’s not what the statement says. It clearly states that the test further bolsters a strategic nuclear deterrent already considered reliable.

This time KCNA gave us a clue into the technical side of things, that is how long the test took. 7 minutes or 420 seconds. That’s important. Firstly, it strongly indicates that once again North Korea has static hot tested a liquid propelled engine at Sohae. The time, and the size of the truck observed prior, suggests something big. That is a high thrust engine. There was instant Twitter analysis about stopping and starting upper stage engines for a post boost vehicle, however North Korea has a number of facilities for testing lower thrust engines than the large test stand at Sohae. The test facilities at Sohae are for testing big engines.

I’ve argued in both my posts that the little we know does not rule out North Korea having tested a new high thrust engine for the booster stage of a new heavy ICBM with a throw weight sufficient for a megatonne class hydrogen bomb. This is where the 420 seconds gets interesting. Long time readers will know I’ve got a soft spot for static hot testing of the RS-25 engine, essentially upgraded Space Shuttle Main Engines, for NASA’s Space Launch System.

The RS-25 engines of the SLS will have a burn time of 500 seconds. Burn times of this ball park are associated with space launch vehicles hauling heavy payloads to high orbits (and in the case of the SLS beyond). The Titan II was America’s heavy LPE ICBM during the Cold War. It also doubled as a space launch vehicle. North Korea has plans to orbit a 1,000kg+ payload to a GEO orbit. We know that what typically happens is that ICBM advances get translated into space launch vehicle advances, not the other way around as we’ve been led to believe with regard to North Korea and Iran. In my previous post I suggested that, like the Titan II, North Korea might well have static hot tested a LPE for a new heavy ICBM that could also double up as a SLV this time for placing satellites into GEO orbit (not project Mercury).

That’s not to say that it did, only that’s it’s reasonable to have this hypothesis in our hypothesis space. Mostly, however, it has been a priori excluded. I don’t think this can be ruled out pending observation. The second, December 13 test, by no means compels its elimination. The main technical specification, the burn time of the December 13 static hot test, does not preclude this even though the burn time was greater than the nominal burn time of a LPE for an ICBM.

Now this is where things get a bit juicy. The December 13 test was accompanied by a statement from the Chief of the General Staff of the Korean Peoples Army. These are the key parts of that statement

The priceless data, experience and new technologies gained in the recent tests of defense science research will be fully applied to the development of another strategic weapon of the DPRK for definitely and reliably restraining and overpowering the nuclear threat of the U.S.

And

Genuine peace can be safeguarded and our development and future be guaranteed only when the balance of power is completely ensured.

We have stored up tremendous power.

This strongly suggests we are seeing here the development of a new ICBM, one more powerful than those we have observed hitherto. Notice that the statement announces a policy of strategic parity. This can be interpreted in two ways. Either we are seeing work toward developing a MIRV or MaRV capability with ballistic missile defence firmly in mind or work toward delivering megatonne class hydrogen bombs to the continental United States. The volume of the Hwasong-15 RV does enable MIRVing, should North Korea seek to go down this road, and the bit about “we have stored up tremendous power” sounds rather ominous.

In between the Academy of Defence Science announcement and the release of the statement by the Chief of the General Staff those who told us not to engage in instant Twitter analysis after the first static hot test on December 7 did precisely that, instant Twitter analysis precluding a new weapon system, and got it badly wrong.

We do not have sufficient information to be firm about any of this, but the information we do have, to repeat, should not lead us to rule out a new heavy ICBM, powered by new booster engines, for delivering a high mass hydrogen bomb to the continental United States. This new ICBM could double up as a space launch vehicle for delivering 1000kg+ payloads to GEO orbit.

As stated previously a new liquid propelled ICBM should lead us to examine why the prevailing assumption regarding North Korea’s next big move, an ICBM propelled by solid fuel motors, proved to be wrong. But that can only happen, to be proper, should we see a new liquid propelled ICBM.

Finally, one might recall the US special envoy for North Korea, Stephen Biegun, say after the Hanoi Summit say that the marginal utility for the US to be gained for dismantling Yongbyon is less than the marginal utility to be gained by North Korea for sanctions relief. It would appear that the Marxists of Pyongyang are about to school the capitalists of Washington in neoclassical marginal utility economics.

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