So, What Would Happen If The Norks Did Fire An ICBM At The U.S.?

The intercontinental ballistic missile Hwasong-14 is allegedly seen during its test in this undated photo released by North Korea’s Korean Central News Agency (KCNA) in Pyongyang, July, 4 2017. [KCNA/via REUTERS]

This past July, North Korea conducted a pair of test launches of a new intercontinental ballistic missile (ICBM), which it calls the Hwasong-14 (“Mars”). While North Korean leader Kim Jong-Un claimed the vehicle can strike “any region and place any time,” skeptical Western military analysts concede it likely has the range to reach much of the United States. (There is disagreement as to whether the Hawsong-14 can actually deliver a nuclear warhead to targets in the Eastern U.S., but analysts concur that it can strike Hawaii, Alaska, and the Western U.S.)

According to a recent Defense Intelligence Agency assessment, the North Koreans have developed nuclear warheads small enough to be mounted on its ballistic missiles, including the Hwasong-14. The DIA estimate also credited the North Koreans with a stockpile of up to 60 nuclear weapons, though some outside analysts believe it to be fewer.

Earlier this week, North Korean Foreign Minister Ri Yong Ho vowed that, “Should the U.S. pounce upon the DPRK (Democratic People’s Republic of Korea) with military force at last, the DPRK is ready to teach the U.S. a severe lesson with its strategic nuclear force.”

What real capability does a functional ICBM with nuclear warheads provide the North Koreans? What would happen if they did attempt a nuclear attack on the U.S.? The answer is that no one, including the North Koreans, knows with any certainty.

Hitting A Bullet With A Bullet: Ballistic Missile Defense

Shooting down an incoming ICBM has been likened to “hitting a bullet with a bullet”; however IBCMs travel at speeds eight times faster than a bullet. The only current ballistic missile defense (BMD) system the U.S. possesses capable of intercepting ICBMs is the Ground-Based Midcourse Defense (GMD), a combination of Ground Based Interceptors (GBIs), long-range radars, and a distributed fire control system. There are only two existing GMD emplacements, one at Ft. Greely, Alaska, and the other at Vandenberg Air Force Base in California. The Ft. Greely site houses 30 GBIs, though ten more are scheduled for deployment there, and four are based at Vandenberg, for a total of 44 by the end of 2017.

GMD has demonstrated a mixed track record in tests, achieving 10 intercepts in 18 attempts (55%). U.S. Air Force General Lori Robinson, commander of the U.S. Northern Command, nevertheless told the Senate Armed Services Committee in April that “Today we have exactly what we need to defend the United States of America against North Korea.”

This conclusion has been questioned by the Government Accountability Office, National Academy of Sciences, and the Union of Concerned Scientists, who have all sharply criticized GMD’s technical viability and accuracy. GMD’s advocates claim that using a “shoot-look-shoot” tactic, which would target an incoming ICBM with successive GBIs raises the odds of success. However, the Union of Concerned Scientists have calculated that if the North Koreans were to fire a volley of five ICBMs and each GBI had a 50% chance of a successful interception, there would be a 28% chance that one of the North Korean missiles would get through.

The U.S. fields three regional or theater BMDs, Aegis, Patriot, and Terminal High Altitude Area Defense (THAAD). These were developed to engage short- to intermediate-range ballistic missile threats, however, not ICBMs, which travel much faster and higher. They are, however, a key component in defending South Korea, Japan, and other countries in the region from North Korean ballistic missile attack.

Another potential ICBM defense would be to interdict the missiles before they are launched. Liquid-fueled missiles such as the Hwasong-14 require hours to fuel with highly volatile propellants, rendering them vulnerable to conventional air or missile attack. While the U.S. and the South Koreans are able to detect test preparations ahead of time, they have not been able to pinpoint launch sites in real time before firing. The North Koreans have developed mobile launchers and capabilities for quickly firing missiles from remote areas of the country far from existing infrastructure. (As the U.S. and its Coalition allies discovered in the 1991 Gulf War, interdicting mobile ballistic missile launchers is a difficult task even with complete air superiority.) Successfully interdicting a North Korean ICBM launch would require far better U.S./South Korean intelligence/surveillance/reconnaissance capabilities than those currently available.

“If he says they can’t hit Nevada on a clear day, you better believe it”

Should a North Korean ICBM successfully evade U.S. missile defenses, what would happen next? This is also a very good question with no clear answer. Conducting a successful ICBM attack with a nuclear weapon is an extraordinarily challenging technical task, which requires a lot of sophisticated technology to function flawlessly under rigorous conditions. The U.S. has tested an ICBM/nuclear warhead under operational conditions only once, with Shot FRIGATE BIRD during Operation DOMINIC in 1962. The submarine U.S.S. Ethan Allen fired a Polaris A2 ballistic missile armed with a 600-kiloton W-47 thermonuclear warhead, which detonated successfully in the air 2,000 meters from target over Johnston Island, 120 miles away in the Pacific Ocean.

Some analysts believe that the re-entry vehicle (RV) from the 28 July Hwasong-14 test broke up before landing. It is unlikely a real warhead would have survived such a failure. RV’s house a ballistic missile’s warhead, protecting it from the stresses of flight and atmospheric reentry and provide the terminal guidance onto the target. The U.S. required years of extensive, expensive testing before it perfected an ICBM RV. While North Korea has developed effective RVs for its shorter range ballistic missiles, the lack of a durable one for the Hwasong-14 will degrade its potential effectiveness and accuracy for the time being.

If a Hwasong-14 RV did manage to survive reentry, what then? On target is a relative term, even with nuclear weapons. North Korea is believed to have developed only kiloton-range fission-type nuclear devices, not megaton-range thermonuclear warheads. Size imposes limits on the yield of fission devices. The Hwasong-14 is estimated to be capable of delivering a payload of only 500 kg or less at intercontinental ranges, which would have to include the RV and the warhead. To date, the North Koreans have tested devices yielding  10-15 kilotons. With the addition of fission-boosting using deuterium, lithium-6, or tritium, the total yield might be significantly enhanced. Some analysts credit the North Koreans with the capability for building a boosted, composite pit device yielding somewhere in the 30-kiloton range. For comparison’s sake, the Fat Man fission bomb dropped on Nagasaki in 1945 had a yield of approximately 21 kilotons.

There is no firm estimate of the Hwasong-14’s circular error of probability (CEP) or the radius within which 50% of missile impacts would theoretically be expected to land, a standard measure of ballistic missile accuracy. By scaling up the accuracy of the Hwasong-14’s SCUD missile antecedent to intercontinental range, one analysis estimated a CEP of 30 kilometers. A blunt-body shaped RV and hasty launches from remote sites would hamper accuracy as well. It is also plausibly arguable that North Korea might be capable of matching the 3-5 kilometer CEP of the first Soviet ICBM, the R-7.

With a CEP of 30 kilometers, it would be entirely possible for a Hwasong-14 to fly successfully, evade U.S. BMDs, detonate effectively, and still completely miss a target as large as Los Angeles.

Map of a hypothetical strike on Los Angeles with a 30-kiloton nuclear airburst, delivered by a ballistic missile with a 30 kilometer CEP. The red cross represents the designated ground zero, the blue lines indicate the CEP radius, and the red dot represents the radius of 5-psi overpressure effects from the nuclear explosion. [MISSILEMAP by Alex Wellerstein, RESTRICTED DATA: The Nuclear Secrecy Blog ]

A CEP of 3-5 kilometers would greatly increase the probability of even a near-miss hitting a densely populated section of the city, killing and injuring tens or hundreds of thousands, if not more.

Map of a hypothetical strike on Los Angeles with a 30-kiloton nuclear airburst, delivered by a ballistic missile with a 3-5 kilometer CEP. The red cross represents the designated ground zero, the blue lines indicate the CEP radius, and the red dot represents the radius of 5-psi overpressure effects from the nuclear explosion. [MISSILEMAP by Alex Wellerstein, RESTRICTED DATA: The Nuclear Secrecy Blog ]

A Catastrophe Of Unimaginable Consequences

Close observers of the North Korean nuclear and missile programs understand that the July missile tests represent a nominal, but real, capability for delivering a nuclear ballistic missile strike against the U.S. The challenges in improving this capability are formidable, but they are technical in nature and there is no reason to believe the North Koreans cannot solve them in time. A true game changer would be the ability to deliver a thermonuclear warhead yielding hundreds of kilotons or more. Some analysts see this development as inevitable.

Regardless of the scenario, the launch of any North Korean nuclear-armed ICBMs toward the United States could only be regarded as a catastrophic failure of American foreign and military policy. The consequences of even a limited nuclear strike on U.S. soil would be effectively unimaginable, far beyond the death, destruction, and inevitable reality of retaliation-in-kind against the North Korean regime.

It would also represent a failure of any rational North Korean defense policy as well, since the only value ICBMs have to North Korea is in deterring foreign attack. They are militarily useless to prevent a counterattack that would invariably destroy Kim Jong-Un’s government. Their only value lies in the political threat to use them.

It would seem then that the U.S. and North Korea share a common interest in seeing that North Korea’s ICBMs are never used. The only sensible means to that end lie in deterrence and negotiation.

3 thoughts on “So, What Would Happen If The Norks Did Fire An ICBM At The U.S.?

  1. Los Angeles would be the best target for a grossly inaccurate ICBM. A large, well-distributed population across a wide area. You could miss downtown L.A. by 20 miles and still kill many thousands.

    That being said, the current Nork ICBM requires lengthy prep time for liquid fueling on an above-ground launch pad. Their shorter-range rockets are mobile, but not the big ones. To exploit that weakness, it’s a sure bet there’s Navy subs on station 24/7 off the Nork coast with Tomahawks at the ready.

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