ASBM Defense Isn’t Easy

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I was taken aback by one of the questions that came my and Toshi Yoshihara’s way last week at the Center for the National Interest: isn’t China’s much-discussed DF-21D anti-ship ballistic missile (ASBM), an “easy” problem for U.S. Navy surface warships, which boast high-tech shipboard defenses like the Close-In Weapons System (CIWS)?

The gentleman who posed the question appeared especially taken with CIWS, a super-fast Gatling gun installed on board American and many allied combatants. And it’s certainly a nifty piece of technology, disgorging radar-guided projectiles at a rate of 4,500 rounds per minute. But impressive technology isn’t always superior. A CIWS magazine only holds enough rounds to sustain that rate of fire for about 20 seconds. More importantly, the system is aptly named. “Close-in” means an effective firing range of “a couple of miles” according to one open-source estimate. This is truly a last-ditch defense considering the hypersonic speed of the threat.

Think about the scope of the problem. Terminal velocity for the DF-21 family of missiles is estimated at Mach 10 to Mach 12, on the order of 8,000 to 9,000 miles per hour. That means the missile covers up to 150 miles each minute, or 2.5 miles per second. At such speeds, CIWS gets around a second to engage a maneuvering target, correct its stream of projectiles onto the target, and make the kill. That’s tough even for a computer-controlled weapon system. And even if the engagement succeeds, detonating the warhead, the debris from the explosion keeps coming along roughly the same trajectory. In all likelihood, some of the debris peppers the ship. Metal shards traveling at hypersonic velocities retain enormous kinetic energy, more than enough to penetrate the lightly armored hulls of modern warships and inflict all manner of havoc within. That’s why CIWS was the subject of much gallows humor when I was a weapons officer—and that was during the pre-ASBM days when the threat consisted “only” of manned aircraft and anti-ship cruise missiles.

That such a question came from such a distinguished group of policy and academic experts suggests that knowledge about naval technology and tactics remains rudimentary among even learned audiences in Washington. By no means do I mean to counsel despair about challenges like the ASBM. There are no permanent victories in peacetime strategic competitions like the one unfolding in the Western Pacific. I fully expect our navy to prosecute the strategic competition with China vigorously, and indeed certain promising hardware is already in the works.

Extended-range missiles like the ‘Long-Range Anti-Ship Missile’ currently under development would let the U.S. Pacific Fleet hold the Chinese surface fleet at risk at distances that would attenuate the missile threat to U.S. vessels. CIWS itself is undergoing improvements, including an extended-range “SeaRAM” destined for use aboard the navy’s new Littoral Combat Ships. And exotic technologies like electromagnetic “railguns” and high-energy lasers hold considerable promise over the longer haul, both as self-defense systems and for offensive functions.

But no, the ASBM threat will be far from easy to counteract if the technology pans out. True, the ASBM or its associated sensors may not live up to their hype. The Soviet Union tried—and conspicuously failed—to field such a system. I remain agnostic myself. If Chinese rocketeers can loft ASBMs toward U.S. carrier or amphibious groups, though, the laws of physics will be on their side—and decidedly against shipboard defenders.

 

James Holmes is an associate professor of strategy at the U.S. Naval War College. The views voiced here are his alone.

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