North Korea's newest nuclear "Hwasong-14" ICBM (HS-14)
(a widened two-stage variant of HS-12)

Norbert Brügge, Germany

Update: 03.09.2017

First what annoys me:

North Korea’s “not quite” ICBM can’t hit the lower 48 states
Bulletin of the Atomic Scientists,
Theodore A. Postol, Markus Schiller & Robert Schmucker, August 11, 2017
"We have identified this rocket motor as a being derived from a family of Russian rocket motors known as the RD-250 or RD-251. The original motors used six thrust chambers fed by three turbo pumps to together generate roughly about 240 tons of lift........This rocket motor was associated with rocket and space launch vehicles produced in Ukraine.........It is clear that the final rocket motor mounted in the Hwasong-14 has this single powerful turbopump feeding propellant to both the main rocket motor and the four smaller vernier motors used to control the direction of the missile".

The secret to Kim’s success? Some experts see Russian echoes in North Korea’s missile advances

The Washington Post, July 10, 2017
Article by Joby Warrick
Mike Elleman, a missile expert at the International Institute for Strategic Studies, is preparing to publish an analysis comparing the engine used in the Hwasong-12 and Hwasong-14 with the Soviet-era RD-250, using photos that highlight nearly identical features, including cooling tubes, exhaust nozzles and the four auxiliary engines that steer the rocket. (Now published, see next)

The secret to North Korea's ICBM success
IISS Voices,
Michael Ellemann, August 14, 2017
"Available evidence clearly indicates that the LPE is based on the Soviet RD-250 family of engines, and has been modified to operate as the boosting force for the Hwasong-12 and -14. An unknown number of these engines were probably acquired though illicit channels operating in Russia and/or Ukraine."

Here will "sold" results without adding any words to who is the actual author of the first fundamental analysis of this topic in September 2016 and March 2017 (
"Pektusan" engine tests ). They have needed months to accept the analysis of an alleged "nobody". Michael Elleman and the others only are thieves. And, the suspicion is wrong that it gave a current deal and the Ukrainian government or Pivdenmash (Yuzhmash) could be involved.
There were many unguarded depots and museums in the time of the collapsing Soviet Union, in which missiles and engines could be acquired.
 
                                                                                                                                                                                                                                                                                                                                                                                                                            

 2017, July 28 -- A further HS-14 launch

 

No words !

 2017, July 04 -- North Korea has tested its new HS-14 ICBM in flight. It seems to be a widened two-stage variant of HS-12.

 

HS-14 on a HS-13 TEL

Second stage

Again a free standing launch

Diameter

 Engine details

 

Second stage engine test ?


          

Analysis:

The HS-14 is a widened variant of the HS-12 with an added second stage. In this design, North Korea now has a real operational ICBM. It replaces the HS-13 project, which was probably discontinued due to problems with the Soviet 4D10 main engines.

So the speculation that the HS-14 is related to the HS-10 is nonsense. On the other hand, it is now sure  that the HS-14 has a larger diameter than the HS-12 (1.70m). The diameter of the second stage is 1.25m. Also sure is that it is a lightweight missile with tank framework.

The assumption, the first stage of the missile uses the recently tested engine (one combustor of RD-250) is probably true. The added steering engines comes from the HS-13 (R-27 origin). The takeoff thrust is approximately 464 kN. The first stage has reached an altitude of 585 km after 145sec burn time.

It was reported that the first stage of the HS-14 during a further launch in July had a longer burn time of 151 seconds due to increased fuel loading, and reached an altitude of 703 km.

The second stage is probably equipped with an engine of low thrust (4D10V?). The burn time of the stage varies between 225 and 235 sec depending on fuel loading.
 

 

Diameter 1.70 m

 

Stage

Engines

Thrust s.l.

Isp s.l.

Thrust vac

Isp vac

Propellant

Burn time

Flow rate

Total Imp

kN

N*s/kg

kN

N*s/kg

-

tons

s

t/s

MN*s (vac)

1

 RD-250

394.1

2644

440.6

2956

UDMH/N204

28.95

150

0.1491

77.8

Verniers (4)

70.0

2452

78.4

2746

150

0.0286

2

4D10V (2)

    35.4 2844 UDMH/N2O4 2.86 230 0.0124 8.1