North Korea’s Sept. 15 Missile Launch over Japan

, co-director and senior scientist | September 14, 2017, 10:25 pm EDT
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North Korea conducted another missile test at 6:30 am September 15 Korean time (early evening on September 14 in the US). Like the August 28 test, this test appears to have been a Hwasong-12 missile launched from a site near the Pyongyang airport. The missile followed a standard trajectory—rather than the highly lofted trajectories North Korea used earlier this year—and it flew over part of the northern Japanese island of Hokkaido (Fig. 1).

Fig. 1. Approximate path of the launch.

The missile reportedly flew 3,700 kilometers (km) (2,300 miles) and reached a maximum altitude of 770 km (480 miles). It was at an altitude of 650 to 700 km (400 to 430 miles) when it passed over Hokkaido (Fig. 2).

Fig. 2. The parts of Hokkaido the missile flew over lie about 1,250 to 1,500 km (780-930 miles) from the missile launch point.

The range of this test was significant since North Korea demonstrated that it could reach Guam with this missile, although the payload the missile was carrying is not known. Guam lies 3,400 km from North Korea, and Pyongyang has talked about it as a target because of the presence of US forces at Anderson Air Force Base.

This missile very likely has low enough accuracy that it could be difficult for North Korea to use it to destroy this base, even if the missile was carrying a high-yield warhead. Two significant sources of inaccuracy of an early generation missile like the Hwasong-12 are guidance and control errors early in flight during boost phase, and reentry errors due to the warhead passing through the atmosphere late in flight. I estimate the inaccuracy of the Hwasong-12 flown to this range to be likely 5 to 10 km, although possibly larger.

Even assuming the missile carried a 150 kiloton warhead, which may be the yield of North Korea’s recent nuclear test, a missile of this inaccuracy would still have well under a 10% chance of destroying the air base. (For experts: This estimate assumes the air base would have to fall within the warhead’s 5 psi air blast radius, which is 3.7 km, and that the CEP is 5 to 10 km.)

Heating of the reentry vehicle

As I’ve done with some previous tests, I looked at how the heating experienced by the reentry vehicle (RV) on this test compares to what would be experienced by the same RV on a 10,000 km-range missile on a standard trajectory (MET). My previous calculations were done on North Korea’s highly lofted trajectories, which tended to give high heating rates but relatively short heating times.

Table 1 shows that in this case the duration of heating (τ) would be roughly the same in the two cases. However, not surprisingly because of the difference in ranges and therefore of reentry speeds, the maximum heating rate (q) and the total heat absorbed (Q) by the RV on this trajectory is only about half that of the 10,000 km trajectory.

Table 1. A comparison of RV heating on the September 15 missile test and on a 10,000 km-range trajectory, assuming both missiles have the same RV and payload. A discussion of these quantities can be found in the earlier post.

So while it seems likely that North Korea can develop a heat shield that would be sufficient for a 10,000 km range missile, this test does not demonstrate that.

Posted in: Missiles and Missile Defense Tags: , , ,

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  • Brian Walker

    Thank you for the straightforward assessment, very informative

  • Bad Penguin

    Next we need to find out who is financing all of this. Since January Korea has launched over 25 missiles and conducted 3 nuclear weapons tests. By anyones accounting the tab to do this has exceeded over $1B. There is a sugar daddy somewhere paying for all of this. Who is it.

  • David F. Johnson, Ph.D.

    Since they clearly have nukes, it is only prudent to assume the worst and that the North Koreans have developed a working re-entry warhead. Any other assumption should be considered wishful thinking. While it is true that a close hit might not cause significant large scale structural damage on Guam, one should assume that the EMP from a nuclear weapon in excess of 100 kilotons would fry a lot of the electronics with a close hit, especially at the right altitude, wrecking havoc on a lot of costly weapon systems, etc. It seems that would be enough to cause a lot of grief, but still the North Koreans would get annihilated for their efforts. It is highly likely that Kim and co-workers are yanking our chain for attention. The best attention we can give them is to shoot down one of their IRBMs. Otherwise, the best strategy is maximum highly enforced sanctions, and then just ignore them. Kim is like a child craving attention. Don’t give it to him.

    • Balázs Jávorszky

      “It is highly likely that Kim and co-workers are yanking our chain for attention.”
      No. The tests are demonstrations of the fact that the US is no longer invulnerable, and any adventurism (like “preemptive strikes”, “decapitation strikes”, whatever, you know the usual US bullsh.t lexicon) will be answered in kind.
      “The best attention we can give them is to shoot down one of their IRBMs. ”
      The most important reason they haven’t tried it so far that they know it wouldn’t work.

  • David K.
    POTUS gave Pentagon the command to shoot down any missiles launched by North Korea after the previous launch, so why didn’t the US do so?? Here is the real answer – ‘current US missile defense doesn’t work against an unpredicted, unscheduled, non-meticulously prepared for test target. The sad reality and dirty little secret is that our current guidance and control technology relies on Proportional Navigation, or an iteration of it (PN, APN, DG). PN CAN NOT intercept hypersonic maneuvering warheads utilitzed by North Korea, China, Russia and Iran. It’s the sobering and scary truth. Good news is the US government has available to it a technology called Hypersonic Intercept Technology or HIT that CAN defeat these threats at a very high hit-to-kill success rate. But there are detractors in the government stopping it, likely for the reason that once this tech is installed in our interceptor systems, the ‘gravy train’ of missile defense dollars will be greatly reduced, once the solution is applied, no more need for ALL these billions of dollars into R&D and upgrades etc. The Missile Defense Agency (MDA) gets a $10 Billion budget EACH YEAR to dole out to defense contractors for making missile defense stuff that doesn’t work. The US needs HIT Technology NOW! This video explains why, but you have to watch all 7 minutes of it to get to the end!

    • J_kies

      This is a marketing item that has been shown to be false. The Israeli individuals behind it coined it in a weekend after the first Gulfwar and were not funded by IMDO as they were known to be falsely marketing. The HIT is the new name previously it was coined as HAG (High Accuracy Guidance) and all the individuals on the tape represent paid representations. The BMDO evaluated all the claims and found them to be false in a general case. The BMDO did not choose to resource their 1 Billion dollar trade secrets request as we determined that we could replicate all the same capabilities as a trivial filter mod. The reason we did not implement that filter mod on systems like Patriot was due to the fact that real threat maneuvers were not suitable matches for the innate model of HAG (or HIT).