The Buzz

Can U.S. Missile Defenses in Asia Stop a North Korean Nuclear Attack?

The recent test of a North Korean intercontinental ballistic missile has thrust America’s ballistic-missile defenses in the spotlight. The new missile, known as Hwasong-14, can theoretically reach Alaska or Hawaii. At the same time, there are several U.S. military bases abroad, especially in the Asia-Pacific, vulnerable to North Korean missiles. How does the Pentagon plan to defend American territory and installations abroad?

The Hwasong-14 missile is a new intercontinental ballistic missile (ICBM). Being a new design, it is likely hobbled by many factors, including a lack of reliability and a warhead that cannot survive reentry. Still, as the small country has repeatedly demonstrated, North Korea’s talented scientists and engineers can overcome engineering obstacles and make missiles that work. It is only a matter of time before Pyongyang fields a reliable ICBM capable of targeting the continental United States.

ICBMs are challenging missiles to shoot down. The long distances ICBM must travel dictate that their warheads come in high and fast. The most practical phase of flight to shoot them down is in the so-called midcourse phase, after the missiles have boosted their warhead payloads into space. The warheads spend several minutes traveling through space, hurtling towards their target, before streaking back down through the atmosphere in the so-called terminal phase.

The United States is currently protected from ICBM attack by the so-called Ground-Based Midcourse Defense system, or GMD. GMD is not just the interceptor missile, but a whole system of sensors and weapons designed to detect and neutralize incoming warheads in a matter of minutes.

The front line of GMD is the worldwide network of X-band ballistic-missile defense radars, including the AN/TPY-2 and the Sea-Based X-Band radar, also known as the “Giant Golf Ball.” These radars would detect, identify and provide tracking data to the GMD’s battle management command, control and communications operators of the 100th Missile Defense Brigade, based in Colorado Springs.

Once a picture of the threat has been developed, along with tracking data for the incoming missiles, the United States would launch Ground-Based Interceptor missiles at the incoming warheads. GBI consists of a multistage missile, itself much like an ICBM, with an exoatmospheric kill vehicle (EKV) instead of a warhead. Once in space, the EKV steers itself into the path of the incoming warhead, destroying it.

The United States currently has thirty-six Ground-Based Interceptors, with thirty-two at Fort Greely, Alaska, and another four at Vandenberg Air Force Base in California. Based on testing, outside analysts believe each GBI has a 50/50 chance of destroying an incoming warhead. The Pentagon’s plan, as plan as understood by outsiders, is to allocate five GBIs per incoming warhead—according to the law of averages, five GBIs should cumulatively have a 100 percent chance of destroying an incoming warhead. Given the number of GBIs, the U.S. defense shield has enough to reliably intercept about seven enemy missiles. More missiles can be added to the system as needed.

In addition to the homeland, a number of U.S. military bases sprinkled throughout the Asia-Pacific would also become targets in wartime. Many of these bases are located in South Korea itself, in Japan, or along the lifeline that stretches all the way back to the United States. These include Osan and Kunsan air bases in South Korea, U.S. Army bases in South Korea, the THAAD missile base in South Korea, U.S. bases in Okinawa and mainland Japan, and U.S. air and naval installations on the island of Guam.

The main defensive system to shoot down North Korean missiles in this area would be the Navy’s fleet of sixteen ballistic-missile defense cruisers and destroyers based in the Asia-Pacific, with five forward based at Yokosuka, Japan. These ships (of which the USS Fitzgerald, recently damaged in a collision with a civilian container ship, was one) use the Aegis Ballistic Missile Defense System, including the giant SPY-1 phased array radar, to detect and track incoming short-, medium- and intermediate-range missiles. Navy BMD ships can also take tracking cues from the Army’s AN/TPY-2 long-range antimissile radars, which are typically deployed with THAAD missile units.

Once the incoming threats are identified, a properly equipped destroyer and cruiser, of which there are about six in the Asia-Pacific, can launch the latest operational variant of the SM-3 ballistic-missile interceptor. Like GBI, the SM-3 intercepts incoming warheads in space. The latest operational version is the SM-3 Block 1B. Developed in cooperation with Japan, the SM-3 is continually improving; the new SM-3 Block 2A has been tested twice, succeeding once in intercepting its target.

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