As Missile Defense Technology Improves, So Do Odds of an Arms Race in the Pacific

In early March, U.S. troops began setting up Terminal High Altitude Area Defense, or THAAD, anti-missile batteries in South Korea, shortly after a quartet of North Korean missile launches. Though THAAD's deployment will help protect Seoul against North Korean missiles, it's far from a perfect solution; it antagonizes China while leaving allies like Japan still vulnerable. Next year, a new shipboard interceptor is slated to arrive in the region, promising more protection — and more controversy.  

 The deployment of THAAD, announced last year and sped up by several months after North Korea's most recent tests, brings to the Korean peninsula land-based missile launchers and sophisticated radars. China views the move as hostile because the radars could allow the U.S. to better track some Chinese missiles.

“It’s a classic case of a security trilemma, where actions taken by one country in response to the actions of another—here the deployment of enhanced U.S. [missile defense] capabilities to offset North Korea’s growing missile capabilities—complicate relations with a third player,” Rod Lyon explained in The National Interest.

Beijing’s worry is rooted in a Cold War-ish anxiety about deterrence. A nuclear-armed adversary that can destroy your ability to wage war has more incentive to launch a first strike against you. By no means would THAAD’s deployment give the United States any sort of serious advantage if World War III were to break out. But it might give the U.S. a smidge of extra early-detection capability. And nuclear deterrence is an area where superpowers are disinclined to surrender even an inch.

What THAAD does not do is offer protection from North Korean missiles much beyond the Korean peninsula.  

“THAAD would improve defense of South Korea, and U.S. forces deployed there, but would not have sufficient range to defend Japan,” Heritage Foundation senior researcher Bruce Klingner writes.

So the United States, with Japan, is looking to deploy a new interceptor system. It would use Raytheon’s Standard Missile-Three, or SM-3, to offer a defense against North Korean mid-range missiles, working with an radar system common to many ships called the Aegis (after the shield of Zeus in Greek mythology). The U.S. currently has Aegis deployed on 33 ships, 16 of which are in the Pacific. By 2020, Aegis will be aboard four Japanese destroyers as well.

The Space Bullet

The SM-3 differs from the THAAD missile in worldly ambition and physical reach. Whereas THAAD is designed to take out missiles as they descend through the endoatmosphere — that is, less than 100 kilometers up — the SM-3s are designed to intercept missiles beyond the Earth’s atmosphere, the so called exoatmosphere. So while THAAD’s missiles are intended to hit missiles as they are rocketing back to Earth, SM-3s are designed to hit them in space. That allows a warship firing the SM-3 to protect a larger area.

This is one reason why the Obama Administration was bullish on SM-3s as a means to curb North Korea’s missile ambitions, at least those ambitions related to short- and mid-range missiles. It was to be a kind of silver bullet. The military soon found that while hitting a bullet with a bullet is hard enough beneath the 100-kilometer ceiling, it is harder in space. SM-3s missed what they were supposed to be hitting during tests in 2012 and 2015.

But the continual miniaturization of electronics, enabling ever-smaller processors to crunch more data, eventually allowed engineers to approach the challenge of exoatmospheric missile interception from a new angle.

Today, the eyes and brains of the newest SM-3s function very differently than those of its predecessors. Lenses and mirrors that would narrowly focus on an object at a great distance, like a telescope, gave way to one that was more broad but did not see as far, like a panoramic lens. Better onboard processors, and more data from external satellites, radars, and other sensors, allowed the system to better differentiate targets with less detailed visual data.

Mitch Stevison, vice president of Raytheon missile systems, described it as the difference between looking through a soda straw and using full peripheral vision.

“You have one picture and then you start looking at object, object, object, picking out the objects, and then correlating the objects to say, ‘not a threat, threat, potential threat, not a threat.’ Then you make decisions on what to do with that much more efficiently than you could with the old systems,” said Stevison. “Certainly the advancing [computer] capabilities gives us the ability to process more data...The advanced processing and advanced algorithms, with the advanced discrimination capabilities, all of those things put together gives us a confidence.”

In February, the Pentagon announced that the newest version of the missile, the SM-3 IIA, had launched from a warship off Hawaii and intercepted a target in the exoatmosphere. Combined with THAAD, the U.S. now had a defense against intermediate-range missiles at multiple altitudes.

In theory, that sort of deterrent should convince North Korea to stop its missile tests. Since North Korean test missiles can be destroyed well above the Earth’s atmosphere, why waste money on them?

Its potential effects on Pyongyang notwithstanding, the new weapon is unlikely to calm international fears, according to other experts.

“Everybody's going to complain that that's a bad thing to do,” said RAND analyst Bruce Bennett, regarding shooting down North Korean test missiles with Aegis warships. “It is aggressive. It is risky. But these missile launches have been sanctioned by multiple UN Security Council resolutions. They're illegal.”

Physicist and arms control watcher Mark Gubrud said SM-3-equipped warships would not be welcomed by China or Russia.

“Deployment of more Aegis systems to this area is a major irritant to both China and Russia, which see these systems as building toward a future capability that could threaten their ability to respond to a US first strike,” Gubrud said. “One can argue that it is better to have some chance of stopping a nuclear missile than none. But this must be balanced against the risk that pursuing an arms race makes the eventual launch of that missile more likely. With or without missile defense, we are stuck with the same need to avoid a major war which could lead to nuclear weapons use.”

For evidence of that, look to Poland. In the wake of its successful tests, the Aegis/SM-3 system will proliferate to land-based Aegis launchers in Europe, part of an expanded missile defense agenda championed by the Obama Administration. “All of these milestones were riding on the success of this test,” said Stevison.

Adversaries aren’t likely to stop innovating simply because the U.S. has a new missile. In the future, “it is also possible for North Korea to add countermeasures that would drastically reduce the system's effectiveness,” Gubrud said.

The Pentagon is already worried about how North Korea and other actors might adapt to the new development by fitting future missiles with multiple heads, or decoys, that diverge after launch. The military is eyeing the development of new so-called multi-object kill vehicles in response. “I'm really careful about talking about threats because those immediately go into areas that we can't really talk about,” said Stevison. “I would characterize it like this. The pace that we see the potential adversaries testing should tell us something.”

Today’s THAAD is tomorrow’s SM-3 IIA, which shall beget more sons and daughters not yet fully conceived. The lesson, if there is one: technology does not end arms races. Unaccompanied by policy, it is merely an accelerant.