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Can the US Prevent North Korea from Testing an ICBM?

By
27 January 2017


According to the New York Times, Kim Jong Un proclaimed to the North Korean people, during his annual New Year’s address, that the military is in the “final stages in preparations to test-launch an intercontinental ballistic rocket.” A North Korean intercontinental ballistic missile, or ICBM, would be capable of threatening the continental United States. In response, President Donald Trump tweeted: “North Korea just stated that it is in the final stages of developing a nuclear weapon capable of reaching parts of the U.S. It won’t happen!”

Not to be outdone, the Wall Street Journal published an opinion piece advocating for the US to employ its sea-based, missile interceptors to knock down the North Korean ICBM should Pyongyang conduct a test launch. However, contrary to the hopes expressed by editors at the Wall Street Journal, the US does not have a proven capability to intercept an ICBM using sea-based assets. The Pentagon may nonetheless attempt to shoot down a North Korean ICBM with SM-3 interceptors based on Aegis destroyers, should Pyongyang elect to test one in the near future. However, the likelihood of success is limited, if not improbable. In fact, the probability that the North Korean ICBM test will fail on its own is significantly higher than the probability of success.

Plausible ICBM Flight Paths?

Drawing from an excellent description of how North Korea might test an ICBM by John Schilling, it is easy to see that the most politically and technically feasible flight-test option would be to use an Unha rocket—possibly one modified to include higher-thrust engines for the upper stages—to evaluate warhead re-entry technologies. The test would likely succeed because the Unha is a relatively proven system, though using the satellite-carrier rocket as a military missile would throw cold water on Pyongyang’s claims that its space program is a strictly civilian enterprise. Further, relying on Unha technology would do little to address the development challenges associated with the KN-08 or KN-14 missiles, which appear to be optimized for the delivery of a nuclear weapon. As such, if North Korea’s primary objective is to develop an operational ICBM, Pyongyang would want to begin by conducting flight trials of the KN-08, KN-14 or both notwithstanding the strong probability initial test flights would fail.

How the missiles are tested will also take into account geographic, political and diplomatic constraints. To avoid the risk of a simulated warhead landing on the territory of another country, North Korea would likely fly the missile to the east; however, an easterly trajectory would necessarily overfly Japan. A test of the two-stage KN-14 offers the greatest likelihood that the impact of the first stage would fall well short of Japan (Figure 1). Use of the three-stage KN-08 would leave little room for error in missing Japanese territory (Figure 2). It therefore seems reasonable that if North Korea decides to launch an ICBM toward the Pacific Ocean, the KN-14 would be the preferred missile.

Figure 1. The KN-14, which has only two stages, can safely be launched to various ranges without risk of the first stage striking foreign territory.

Annotation by Michael Elleman / 38 North.

Annotation by Michael Elleman / 38 North.

Figure 2. Launching the three-stage KN-08 to the east risks having the second stage land on Japanese territory. This would likely deter North Korea from choosing the KN-08 for its initial ICBM test launch.

Annotation by Michael Elleman / 38 North.

Annotation by Michael Elleman / 38 North.

Can a Test be Prevented by Military Means?

The United States and Japan operate Aegis ships armed with SM-3 Block 1A and 1B interceptors in the East Sea. These ships are capable of intercepting short, medium and intermediate range ballistic missiles in the mid-course and terminal phases of flight. Tests to validate the performance of the SM-3 Block 1 interceptors are ongoing and to date have been largely successful. SM-3 interceptors have never been tested against an ICBM, nor have they been tested against any missile in the boost or ascent phase of flight. In other words, boost- or ascent phase intercepts using SM-3 interceptors are an unproven, hypothetical capability.

An Aegis ship armed with SM-3 Block 1A or B interceptors could, in principle, intercept a North Korean KN-14 ICBM under a limited set of circumstances. If North Korea flies a KN-14 on a minimum-energy trajectory, and the Aegis ship is located 500 km from the launch site, intercepts are kinematically possible. If, however, Pyongyang launches the KN-14 on steeper trajectories, the possibilities are reduced. For lofted trajectories roughly 18 degrees steeper than minimum-energy ones, no intercept is possible. In other words, North Korea can defeat America’s current sea-based capabilities by flying the ICBM to higher altitudes and shorter distances, while still gaining the necessary engineering information to support missile development. Though it must be noted, as stated previously, the KN-14 (or KN-08) is more likely than not to fail on its own during initial flight tests.

But even if the US was improbably fortunate, and North Korea launched a KN-14 directly over an Aegis ship, and the trajectory is not sufficiently lofted, it is doubtful that a successful intercept would occur. There are multiple operational reasons why an intercept is beyond current capabilities.

First, it is doubtful that an Aegis ship would be close enough (500 km or less from the KN-14 launch location) at the right time. The US or Japan would be placing their Aegis boats at considerable risk if either attempted to move closer than 200 km off North Korea’s coast while waiting for a launch. At the very least, good fortune would be needed to have an Aegis ship in the right place, at the right time to support the narrow circumstances under which an intercept could occur.

Second, it is unclear if the necessary tracking data can be acquired with enough precision when relying solely upon the Aegis’s on-board SPY-1D radar. Would other high-precision sensors be available to aid in developing a KN-14 track at the earliest possible moment? The answer today is likely to be no.

Third, can a fire-control solution be developed in just the required 10 seconds after the SPY-1 radar detects the KN-14 missile? This is likely an overly optimistic assumption, as command, control and communication limitations would likely delay the transmission of critical data, the development of a fire-control solution by the Aegis SPY-1D radar and battle management system and finally the decision and command to fire the interceptor. If it turns out that 30 seconds are required, then an intercept using SM-3 Block 1 interceptors is not possible, even when only the kinematics are considered.

Fourth, to reduce the chances of a successful intercept, North Korea could decide not to fly the missile to maximum range and to put it on a trajectory that is off-line from the Aegis ship. But even in the unlikely event that the KN-14 flies directly over an Aegis ship, the KN-14 would have already passed over and be moving away from it because a fire-control solution for the interceptor will likely require too much time. While it is still kinematically possible for intercepts to occur when the target is moving away from the SM-3’s launch position, such intercepts are not considered feasible because the interceptor is ‘chasing’ the target from behind. Therefore, the last possible intercept point is defined to occur when the target is directly over the Aegis ship.

In sum, current capabilities to intercept a North Korean ICBM using sea-based assets are lacking. However, when the SM-3 Block 2A interceptor becomes operational, the calculus changes dramatically. The Block 2A interceptor is projected to have a burnout velocity of 4.5 km/second, which is 50 percent faster than the current Block 1 interceptors. The added speed facilitates much greater possibilities. With this in mind, the Pentagon should be developing concepts of operations, procuring enabling assets and planning to test the Block 2 interceptors against ICBMs in the boost and ascent phases.

Conclusion

Preventing Kim Jong Un from developing an operational ICBM can be achieved if North Korea never tests prototypes of the missile. Without flight tests, Pyongyang will not know if the ICBM’s performance and reliability are adequate. However, sea-based missile defenses available today are not capable of reliably interrupting a North Korean ICBM test.

Reader Feedback

17 Responses to “Can the US Prevent North Korea from Testing an ICBM?”

  1. Kostadinov says:

    All this AWACS,fighters,drones and flyuing saucers with powerfull and constantly working radars relatively close to the borders are perfect targets for all imaginable countermeasures.

  2. J_kies says:

    Mr Anonymous_wonk
    You misunderstand; the innate design and phenomenology of the satellite systems precludes reporting at lower altitudes, clear or cloudy days does not matter. So no; satellite data as presently obtained and reported is not useful for such BPI or ‘early’ intercept.

    As the missile defense problem is presently allocated to the US Missile Defense Agency, its pretty trivial to examine their public plans. It can be noted that no such efforts are planned or funded to add BMD modes to either AWACs or fighter engagement radars at this time.

    If you are suggesting that the appropriate response to the “8-star memo” to SECDEF would have been to reallocate mission and funding away from MDA to the services to develop such options, that would be a good discussion to hold with DOD leadership as no such options will be available otherwise.

  3. Anonymous_Wonk says:

    1) Cloud scatter/backscatter. It constrains DPRK to launch their surprise attack to days with mid to high level and IR thick overcast. It means that AWACS or CAP nose-cone radar painting can stand down on days when the weather is clear. That cuts the fuel and personnel cost.

    2) Keeping a special purpose EC-135 or a few classic combat fighters (with their smaller area radars) orbiting is pocket change to defend the world against a surprise ICBM attack. We could most likely mount the radars on drones and/or Aerostat style balloons so that we can save further on fuel and airborne personnel.

    In short, this DPRK ICBM boost phase BMD is a solvable problem with a very small amount of imagination using off the shelf hardware, bespoke software, and a little development time. It would be negligent for our armed forces not to be engaged in this right now. Fortunately, for the foreseeable future, they don’t have that many nuclear warheads and right now zero tested ICBM delivery vehicles. An appropriate policy could keep it that way if negotiation or persuasion doesn’t carry the day.

    I would much prefer a peaceful solution to this nuclear threat and I wish the best for the DPRK people. But just in case, we need a plan B to prevent nuclear blackmail by a determined or semi-rational opponent. This is the responsibility of our defense forces.

  4. J_kies says:

    Mr anonymous_wonk; too generous by far.
    Overhead data is constrained by ‘cloudbreak’ which is a misnomer. In the real world satellites are deliberately constrained to report on things that are rising above potential cloud levels via absorption bands to minimize solar-illuminated cloud clutter. Given that false-alarms that might start world war III are considered a bad thing; confirming data preventing false-alarms makes satellite reporting prior to radar horizon from the case discussed rather unlikely. So no; no magical satellite data to address early shot kinematics.

    As to close in AWACS – sorry they aren’t designed or tested to ID a missile rising to support CEC and airborne IR has to contend with cloud free line of sight and a detection process to ID a missile launch. Not impossible but prohibitively expensive to maintain a CAP and this concept would require a serious engineering development program that isn’t presently planned. So again no, no magical aircraft data to address early shot kinematics either.

  5. Anonymous_Wonk says:

    (Michael Elleman said)…
    “Finally, Kostadinov is correct. SM-6 would be ineffective against an ICBM launch. If NK launches from positions near its center, the ICBM will be at least 9km (~30,000 ft) before it is detected by the ship’s radar, and this assumes the ship is only 100km offshore.”

    Why does ship need to wait until the ICBM is over its radar horizon to see it and launch — the ICBM will be detected well in advance by spaced based infrared, and potentially orbiting aircraft radars and infrared sensors via “Cooperative Engagement Capability” networking, so that this sensor net can “look down” into the missile launch areas and provide relative range, azimuth and elevation data for 3D approximation of position, velocity, and acceleration. This data needs to be downlinked to the fire control computer system. Then a SM-[x] missile can “pre-positioned” as a first order approximation during boost phase to minimize the amount of distance and velocity that must be made up by the interceptor during launch. The Japanese are rumored (Wikipedia) to have this already in place.

  6. J_kies says:

    Dr. Elleman, a well considered article that is actually too generous to the presumptions. Unlike the other commentary, the key problem of boost phase is uncertainty on intended target causing significant errors in final velocity / burnout time. Tracking a boosting target does not provide the same constraints as a ballistic one and the AN/SPY was not designed or tested to support engagement quality data against a missile in boost.

    An SM-6 missile might be able to conduct boost phase engagements against an ICBM prior to the ICBM exceeding its kinetic envelope (maximum engagement altitude). The problem of placing a ready missile inside of one minute flight time from an ‘unknown’ launch point we leave as an exercise for the student.

  7. Michael Elleman says:

    Notionally positioning the Aegis ship 100km or less of North Korea’s coastline places it within range of anti-ship cruise missiles. Force protection would be priority one for Aegis. This would require the ship’s SPY-1D radar to scan for cruise missiles and ballistic missiles simultaneously. This is possible with the latest versions of Aegis, but not all versions. In all likelihood, Aegis ships would patrol on pairs to mitigate risk. And as we do not know when an ICBM launch might occur, two ships would necessarily be tied to this one mission. So it short, it is feasible to patrol closer than 200km off shore, but it is probably unlikely.

    But even if patrolling 100km off shore, lofting to higher angles will still defeat SM-3 Block 1 interceptors.

    On the time needed to develop a fire-control solution and launch the interceptor, ten seconds was the optimistic value adopted by the NAS study. Experts familiar with operations tell me that 10 seconds is optimistic. See: Making Sense of Ballistic Missile Defense: An Assessment of Concepts and Systems for U.S. Boost-Phase Missile Defense in Comparison to Other Alternatives,(Washington, DC: National Academy of Sciences, 2012)

    Finally, Kostadinov is correct. SM-6 would be ineffective against an ICBM launch. If NK launches from positions near its center, the ICBM will be at least 9km (~30,000 ft) before it is detected by the ship’s radar, and this assumes the ship is only 100km offshore.

  8. Kostadinov says:

    “I agree that stationing a US ship near the DPRK coast is feasible.”
    Stationing nk ships near the US ship is also feasible. The best outcome will be repetition of the Korean war.

  9. Kostadinov says:

    “Parked in international waters 50 miles offshore a SM-6 missile will take down a launched ICBM at 20,000 feet effortlessly, no matter what the launch angle is.”
    If the nk missile launching site is 100 miles inshore and SM-6 start is in the same moment with average speed of the inteceptor 1,5 km/s more than 3 minutes are needed simply to reach the target. 3 minutes after launch an ICBM is well above 20000 feet.

  10. Anonymous_Wonk says:

    “While i agree that a stage 2 deterrent is essential., we don’t want another ship incident in the East Sea like the USS Pueblo seizure in 1968. It is a trophy asset used for maximum political purposes by the DPRK.”

    What does this capture “worry” have to do with anything in the discussion. You comparing a virtually unarmed research vessel (Pueblo) to a U.S. guided missile cruiser or destroyer. Pueblo was captured by a sub-chaser that attacked it with a 57 mm cannon and machine guns. Pueblo was negligently left undefended with no air to surface armed supporting aircraft within two hours, and its only weapon, a 50 calibre M-2, stored below deck. Pueblo never had a chance.

    Note that the Iran Riverine boat officers in charge were punished for failure to defend their vessel against capture. They were crewed by relatively junior officers who were initially negligent, and then punished for dereliction of duty. Even that won’t happen again.

    The U.S. Navy is not negligent with its major combat vessels: it will never surrender an Aegis cruiser/destroyer after being approached to within visual range by (DPR) Korean “fishing trawlers”, sub-chasers, speed boats, destroyers or Migs, without a massive fight. The vessel commander will see the threats well in advance. Submarines and mines are another problem, but our surface vessels are prepared to defend themselves against those threats as well.

    Our combat ships can and will be prepared to defend themselves from capture. And such a weapons attack where actual hits are scored (as opposed to warning shots) on an major American combat naval vessel is an act of war, which should act as a deterrent for the DPRK. Rationally, the DPRK will only attack such a vessel when it is committed to a full scale war, which would only happen after its nuclear weapons delivery systems are fully tested.

  11. NorEastern says:

    The above article is incredibly over pessimistic. Parked in international waters 50 miles offshore a SM-6 missile will take down a launched ICBM at 20,000 feet effortlessly, no matter what the launch angle is. After all they can reliably destroy the supersonic Brahos missile.

  12. NorEastern says:

    Of course the US can prevent any such test. Just park an Arleigh Burke 60 miles off the coast of NK and shoot down anything that achieves an altitude of 15,000 feet. The diplomatic fallout of such an action is beyond calculation though.

  13. John Moore says:

    I agree that stationing a US ship near the DPRK coast is feasible. It is a risk, but the DPRK would put itself in great peril if it attacked such a capable vessel, especially with enough force to overwhelm its world class defensive assets. With a new President in office, one who is hard to predict due to his unusual style and history, the DPRK would be very foolish, or very desperate, to launch such an attack.

  14. John Kim says:

    How can you prevent North Korea from doing anything except by going a war?

    US is not all mighty.

  15. jack norris says:

    NK ICBM Response: It is now obvious that an effective response to a ICBM launch can no longer use the traditional command and control protocols as an instant response is necessary if we are to be successful in avoiding an attack.

    I don’t think that we’ve thought through this reality as yet; by default the decision has now been pushed down to the lowest common denominator – the guy or gal at (or close to) the console. I don’t know if that’s good or bad, but it is sobering.

  16. Mark Sommer says:

    There’s a lot of hypotheticals in the above argument. While i agree that a stage 2 deterrent is essential., we don’t want another ship incident in the East Sea like the USS Pueblo seizure in 1968. It is a trophy asset used for maximum political purposes by the DPRK. The best idea is to work with the contact nations and make sure Japan does not engage in any preemptive strikes as has been mentioned erroneously in some quarters. They want to talk and we have people who’ve met the man there. Any rash action preemptively could be counterproductive. The respected Chatam House said North Korea doesn’t have the missiles with range that reach anywhere in the continental US and probably won’t for the foreseeable future. IMO it’s a theater threat of which THAAD will hopefully serve for South Korea’s defense. We must keep the lines of communication open.

  17. Anonymous_Wonk says:

    “Third, can a fire-control solution be developed in just the required 10 seconds after the SPY-1 radar detects the KN-14 missile? This is likely an overly optimistic assumption, as command, control and communication limitations would likely delay the transmission of critical data, the development of a fire-control solution by the Aegis SPY-1D radar and battle management system and finally the decision and command to fire the interceptor.”

    You statement is overly pessimistic. 1) US, Japan, and Korea commenced a missile defense exercise on Jan 20th. The purpose was likely to solve and keep permanently linked the radar and fire control systems of multiple land and naval based radars. This is a feasible problem that can be solved in a week if a Presidential order was given by all three countries. 2) Given the above data, the solution to the intercept will take less than a few hundred milliseconds on a single thread in a single core processor. This is not a complex simulation problem, but simple intercept mechanics. Be real here. 3) If the President of the United States has placed a standing order to launch on sight any ICBM, there is no need for a human in the loop once the software has verified the target is a missile and not an aircraft.

    Your statements in the other paragraphs I largely agree with, although solving for an intercept network configuration that can target the DPRK missiles in boost phase is an engineering problem that can be solved with time.

    Further, stationing a guided missile destroyer less than 200 km off the DRPK coast is feasible with proper anti-mine and anti-submarine defenses, and further, an attack on a U.S. Naval ship (i.e. not on a drone or a missile, but on a manned vessel) is an act of war which would demand an immediate retaliation, thereby providing a deterrent to the DPRK.

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Credit for photo of young North Korean girl: T.M. All rights reserved, used with permission.