The U.S. Navy plans to begin deploying interceptors that can shoot down hypersonic missiles aboard some Arleigh Burke-class guided missile destroyers in just a few years. Though some critics counter that the Navy's timeline seems awfully optimistic, as no existing missile defense system has proven capable of intercepting an inbound hypersonic weapon.
Hypersonic missiles fly in excess of Mach 5, and potentially much faster than that, making them so much faster than the ballistic and cruise missiles previously employed by national militaries that even advanced air defense systems like America's destroyer-based Aegis Combat Systems can't find and shoot down hypersonic missiles in flight. This has raised the alarm among many within the Defense Department, both in order to field America's own hypersonic weapons and, of course, to find ways to defend against those employed by foreign militaries.
There are different methods of achieving hypersonic velocities with a missile, including scramjet propulsion that often requires either a rocket-assist at launch or deployment from fast moving aircraft, as scramjet motors require a high volume of airflow in order to effectively operate. Conversely there are also hypersonic "glide vehicles," which are traditionally carried to a high altitude using a rocket motor similar to those employed on intercontinental ballistic missiles. The hypersonic glide vehicle then separates from the booster and travels back to earth at exceedingly high speeds. In fact, some of these missiles travel so fast that the kinetic transfer of their impact is enough to sink a vessel without the need for an explosive warhead.
The United States has been fairly public about its efforts to begin fielding its own suite of hypersonic missiles in the coming years, but until recently, America's Defense Department has echoed the popular consensus that hypersonic weapons can't be stopped. Now, however, America's Regional Glide Phase Weapon System (RGPWS) is seeing rapid development for the purposes of deployment specifically (at least initially) aboard America's advanced destroyers.
America already relies heavily on its fleet of Arleigh Burke-class guided missile destroyers for missile defense, which some critics have called a waste of destroyer bandwidth. When serving in an air defense role, U.S. Navy destroyers are left criss-crossing specific areas of ocean to maximize their ability to intercept inbound missiles, which, some argue, is a waste of a platform that's capable of supporting a wide variety of defense operations. However, it seems the U.S. Navy's plan for hypersonic defense will also leverage the multiple launch tubes available on America's destroyers, effectively guaranteeing the continued use of destroyers for missiles defense for years to come.
The RGPWS system has apparently been designed specifically for use in the Mk. 41 vertical launch tubes utilized by America's destroyers and other vessels, which will allow this hypersonic-intercept capability to be rapidly deployed and adopted aboard existing vessels with little need for modifications. According to the Navy, this will allow America to "proliferate the capability" across the force very rapidly.
This system is specifically tailored toward the glide-vehicle method of hypersonic weapon propulsion, designed to engage an inbound hypersonic glide vehicle (HGV) during its un-powered glide phase, which despite its extraordinary speed, is the point I which these platforms are most vulnerable to intercept.
Of course, in order to effectively intercept HGVs, the Navy will need advanced warning of their launch. In order to do so, the Navy is working with the Missile Defense Agency and the Space Development Agency to field a new space-based sensor system that is expected to be operational within the next three years. Using the early warning provided by this new sensor array, the RGPWS will theoretically be capable of projecting the trajectory of HGVs and intercept them before they're able to reach their target.
While the RGPWS system will be limited to destroyers initially, these systems will likely find their way into a variety of platforms, including ground and air-launched varieties. If the U.S. is able to find a way to reliably intercept inbound hypersonic weapons, America's naval stature, and many defense official's position on the future of aircraft carriers, will both likely shift. Currently, many law makers and defense officials are looking to de-emphasize the role of carriers in near-peer conflicts over fear of losing them to indefensible hypersonic weapons.
As for exactly how the RGPWS system will work–that much remains a secret for now.