How Would the U.S. Defend Against a North Korean Nuclear Attack?
By Chloe WhiteakerChloe Whiteaker, Jeremy Scott DiamondJeremy Scott Diamond and Tony CapaccioTony Capaccio
After successfully testing two intercontinental ballistic missiles and a bomb with far more destructive power than those dropped on Hiroshima and Nagasaki, the North Korean nuclear threat has never been more credible. When asked on Wednesday about possible military action, President Donald Trump said, “We’ll see what happens.” That did little to reassure those still shaken by his remarks last month that the U.S. military was “locked and loaded” and that further threats from Pyongyang would be met with “fire and fury.” Secretary of State Rex Tillerson, for his part, is still pushing for a diplomatic solution and hoping to calm fears of nuclear war, saying “Americans should sleep well at night.” But should we?
The U.S. missile defense system is a global network with 24-hour surveillance by land-, sea- and space-based sensors, all of which are constantly looking for signs of anything amiss in North Korea. Regional missile interceptors are deployed in Japan, South Korea, Guam and on U.S. Navy ships, while military bases in Alaska and California are equipped to intercept a missile headed toward the United States. So what would that response look like? It’s impossible to say exactly, with so many variables in play and almost as many failures as successes in tests, but this is theoretically how the system should work.
U.S. Missile Defense System
If North Korea were to launch a missile, U.S. satellites would detect it almost instantaneously through infrared signals. In less than a minute, the satellite would raise the alarm, and the command and control center at Schriever Air Force Base near Colorado Springs, Colorado would spring into action.
The command center in Colorado would direct the radars in the region to track the missile as it climbed toward outer space. During that five- to seven-minute stretch, the TPY-2 and SPY-1 radar systems would be gathering data like trajectory, velocity and altitude to send back to the command center so they can figure out what type of missile was launched and whether it could reach the U.S. This “boost phase” is actually the ideal time to intercept a missile, but the current defense system isn’t equipped to do so yet.
The officers at the command center would consult with U.S. Northern Command (Northcom), based nearby at Peterson Air Force Base, where a round-the-clock watch officer would be responsible for approving an interceptor launch. If there was time, they might notify the Secretary of Defense in Washington, too.
The command center would send launch orders after determining whether Fort Greely or Vandenberg Air Force Base was better-positioned to intercept. By the time of launch, about eight to ten minutes may have passed since the North Korean missile was first detected.
Ground-Based Interceptors (GBI) are the only weapon capable of destroying an intercontinental ballistic missile (ICBM), and they’ve only been tested against such a missile once—with success. The U.S. only has 36 GBIs in the field—four in California and 32 in Alaska—and would likely launch a few per incoming missile to improve the odds of success during an attack. That stockpile is expected to expand to 44 by the end of the year, but it’s not hard to imagine how the U.S. defense could theoretically be overpowered if North Korea were to fire multiple missiles. The Pentagon said in June that it can protect the nation from “a small number” of missiles—not a barrage.
Once in space, the interceptor would release an Exoatmospheric Kill Vehicle (EKV)—a device that uses kinetic force to destroy missiles outside the Earth’s atmosphere.
Radars would track both the EKV and the missile, looking out for countermeasures like decoys that some missiles use to confuse the defense. The TPY-2 and sea-based X-band radars are best at picking out a warhead from other flying objects in a so-called “threat cloud.” Real-time updates would flow through the command center and be relayed to the EKV to guide it toward the incoming warhead.
Still flying through space, a North Korean warhead might be about three-quarters of the way through its roughly 30-minute journey to the U.S. at this point.
Using sensors, rocket thrusters and guidance from the command center, the EKV may fly for roughly six to 12 minutes before hurtling itself into the warhead at incredible speed—completely destroying it and avoiding nuclear catastrophe.
To be sure, the whole process could happen quicker, but without history to reference, estimates are the best information available. Experts say there are countless variables that could shift the clock one way or the other—trajectory, altitude and targets to name a few.
Intercepting a missile is commonly compared to hitting a bullet with another bullet. How often does that actually work? In 18 tests since 1999, ten have been successful. Only one—on May 30—was against an ICBM. None included multiple missile threats. Critics lambast the tests for being unrealistic and scripted to ensure success—they’re conducted with few decoys and in daylight with advanced warning.
“The tests are reflective of what we’re seeing in the threat,” according to Ian Williams at the Center for Strategic and International Studies. More recent tests have included some decoys and dodging maneuvers. Next year the Pentagon will launch two interceptors at one target for the first time.
Testing interceptors to make sure the $36 billion system works in a realistic scenario is understandably difficult—not least of all because the Pentagon must ensure the interception occurs in a carefully crafted location that is clear of populated areas or ships beneath it, should debris fall down to Earth. It’s costly too—the May 30 test cost $244 million. That said, “they’re on the right track in the fixes” but haven't yet proven a "realistic capability," according to Laura Grego, senior scientist for the Global Security Program at the Union of Concerned Scientists.
A successful interceptor test on May 30. Video courtesy of the Missile Defense Agency
More improvements are on the way. A redesigned kill vehicle is expected by 2020, which promises easier and cheaper production while also improving reliability. A multi-object kill vehicle is in development, with talks of accelerating the program, which would allow sending more than one kill vehicle on a single GBI. Congress is also pushing to increase the number of GBIs in deployment. An amendment to the defense policy bill for fiscal 2018, proposed by Senator Dan Sullivan (R-Alaska), would add another 28 GBIs—to bring the total up to 72—and explore options for increasing the reserves to 100. That bill also calls for a new space-based sensor layer that would provide precision-tracking of missiles and more advanced discrimination between warheads and debris.
On the ground, a new high-resolution, long-range discrimination radar (LRDR) is scheduled to be deployed by the end of 2020 and would have a much wider, clearer view for tracking missiles to improve the accuracy of the GBIs we have. There’s been support in Congress for a third missile defense site in the eastern U.S. as well, though top officials at the Missile Defense Agency and the Pentagon have said it’s not really necessary because the current sites already protect all 50 states.
What's more, some experts believe North Korea is still a ways off from being able to back up its threats. "It is clear North Korea has the capability to build a missile that can range the distance to the United States, but North Korea has yet to demonstrate it has the requisite technology and capability to actually target and strike the United States with a nuclear weapon," according to General Paul Selva, the No. 2 U.S. military official, who offered his thoughts in a statement to Bloomberg on Aug. 29. In the end, all sides would like to see that the missile defense system never needs to be used at all.
So should Americans sleep well at night? Yes, for now.