There are at least three major types of hypersonic weapons, some of them already deployed by Russia and China, and others under development in the United States.
The first is known as a hypersonic glide vehicle. The Russians have already deployed one of these, called the Avangard. This is a weapon that carries six or more nuclear warheads and is launched from an Intercontinental Ballistic Missile. For Russia, the missile of first choice is the newly introduced RS-28 Sarmat, a liquid-fueled, heavy thermonuclear intercontinental ballistic missile. As the missile reaches near the end of its trajectory it launches a hypersonic glide vehicle (Avangard) that can maneuver to evade missile defenses.
Current day strategic missile defense systems are not optimized to go after maneuvering threats – these are optimized against predictable warhead reentry ballistic trajectories.
The second threat is a long-range maneuvering scramjet powered vehicle – essentially a cruise missile that operates in the upper atmosphere. To get intercontinental range, using oxidizing fuels (such as liquid hydrogen and liquid oxygen) is excluded; Russia is now testing a hypersonic nuclear fueled weapon called Burevestnik, part of the 9M730 project. This weapon uses air as its fuel that is highly compressed and fed into a hot unshielded nuclear reactor that burns the fuel and powers the weapon. If this weapon continues in development (there have been three failures with dangerous results), Burevestnik will have unlimited flight range and the ability to penetrate existing air defense systems.
The third threat are tactical cruise missiles, such as the Russian Kinzhal (Dagger) that can be launched from a MiG-31 BM or another platform, and the Zircon (3M22) which is ship launched and will soon be operational on two Russian warships including the Admiral Grigorovich class and Admiral Gorshkov-class frigates. These tactical weapons probably use conventional explosives but could be equipped with nuclear warheads. The range is around 1,000 km.
Even without the hypersonic cruise missile threat, US strategic missile defenses are very limited, and there is no missile defense system protecting the northern, eastern or southern United States.
For example, THAAD (Terminal High Altitude Area Defense) has been deployed in Guam, the United Arab Emirates, Israel, Romania, and South Korea, but the Israel and Romania deployments were only temporary. THAAD might be able to hit a hypersonic glide vehicle, but it can’t deal with a hypersonic vessel that maneuvers. THAAD’s radar also might not be able to track a cruise-type hypersonic vehicle at lower altitudes.
The Ground-Based Mid-Course Interceptor (GBI) is deployed at Fort Greely, Alaska and Vandenburg Air Force Base, California. Currently, there are 44 interceptors deployed. GBI is America’s primary ballistic missile defense of the homeland system. The Pentagon has been aware that GBI’s current interceptor missiles won’t work against hypersonic threats. In late August DOD canceled work on an updated interceptor, surprising the industry. The reason was the inadequacy of the system (based on DOD supplied requirements) to address the hypersonic threat, particularly hypersonic glide vehicles.
Neither THAAD nor GBI are what can be called effective systems. While they sometimes hit a target in tests, they also miss many, even when the target trajectory is known and to a degree optimized for intercept. And in these tests the assumption is always that there is no surprise and that everything works perfectly (no one asleep at the switch).
THAAD, GBI and SM-3 II-A/II-B, the Navy’s strategic ballistic missile defense system all use so-called kinetic warheads to intercept an incoming missile. A kinetic warhead must actually hit the incoming missile with perfect accuracy.
Kinetic warheads were adopted to make missile defenses more acceptable for military and civil reasons. A kinetic warhead absolutely destroys an incoming threat or misses it altogether. An explosive warhead, by contrast, may damage but not always destroy an incoming threat. When Iraq fired Scud missiles at Israel, the Patriot air defense system often damaged them but did not destroy all of them, so the missiles still hit the ground and exploded, though not necessarily where they were aimed. One reason the Patriot had a hard time knocking out the Scuds was that its explosive warhead was too small; another was that the Scud missiles tumbled as they descended, probably because they were out of fuel and had questionable aerodynamics. This made a kill against these missiles challenging.
A kinetic interceptor used against hypersonic weapons has been called using a bullet against a bullet – a difficult trick. New technology and new approaches are needed if the United States wants to support a credible defense against strategic and tactical threats.
Brilliant Pebbles Revisited
Brilliant Pebbles was part of the Strategic Defense Initiative (SDI) announced by President Ronald Reagan in 1983 and canceled in 1994. The basic idea was to put in space a non-nuclear system of satellite-based interceptors designed to use high-velocity, watermelon-sized, teardrop-shaped projectiles made of tungsten as kinetic warheads. While the system was never deployed, it was extensively studied and, among the many different SDI proposals, Brilliant Pebbles was the best of the lot. The advantage of Brilliant Pebbles satellites was that they were designed to destroy incoming ICBMs once they lifted into space and before they unleashed their warheads. No existing ballistic missile defense system deployed by the United States can do this.
Because brilliant pebbles would destroy an incoming missile this early in its flight path, there would not be a chance to launch a hypersonic glide vehicle, and the glide vehicle along with the missile carrying it, would be destroyed.
The US should revisit Brilliant Pebbles. Much of the R&D needed for such a project has already been carried out and it would not take a huge budget to start actual testing of a complete system.
The real objection to Brilliant Pebbles is the same as the real objection to the SDI program, that we should rely on Mutually Assured Destruction (MAD) as the best way to avoid an all-out nuclear war. If MAD were true, the Russians and Chinese would not keep looking for ways to achieve a First Strike capability. Avangard is exactly that kind of system. MAD is the fundamental reason the United States has such a feeble and sparse anti-ballistic missile capability. But does it make sense to keep investing in poor systems such as THAAD and GBI which are not capable of protecting US territory? Especially so, where the US does not even deploy the systems it spends billion on to protect most of its home territory. The time has come to either fish or cut bait. Spending more money on a new interceptor for GBI is a waste of resources when far better solutions, particularly Brilliant Pebbles could replace them.
Tactical Hypersonic Defenses
An even bigger problem looms with protecting US assets from conventional hypersonic weapons. This includes land, air and ship-launched hypersonic cruise missiles. The Russians have demonstrated rather conclusively that they already have a generation of cruise missiles that are proven to work under real combat conditions (as shown in Russian sea and submarine launches against targets in Syria).
The Russians are now claiming that their new air defense system, the S-500 Prometey (Prometheus, the successor to current S-400 system) will be able to intercept and destroy hypersonic cruise missiles. The S-500 system is in final development, and the missile it will rely on is called the 77N6-N1. According to Russian sources, the 77N6-N1 will have a kinetic warhead (like US systems and Israel’s Arrow 3) and intercept at a speed of 7 km/s (or above 15,656 mph or Mach 20).
There are many doubts about Russia’s S-500 system and even more about its ability to produce the 77N6-N1 even if the interceptor works. The Russians make many claims, and very often they are inflated. Sometimes systems they claim that work fail under test, like the recent three disasters with the Burevestnik nuclear-fueled scramjet cruise long-range loitering cruise missile.
Russia reports that it plans to deploy the S-500 around Moscow, essentially as an ABM system. But to work the system needs to also be tied to existing S-400s, meaning that the system will have to be tightly integrated to work, if it, in fact, functions as advertised.
Furthermore, it is not just the interceptor missile that has to be optimized against tactical hypersonic cruise missiles. The sensors also have to pick up the hypersonic cruise missile quickly enough so that an interceptor has time to launch and get to the target (forgetting about maneuverability for the moment). The Russians say it will take about four seconds to detect and launch, an improvement over the S-400 which took eight to 10 seconds to detect and launch. Then it takes some seconds to reach hypersonic intercept speed. All of this means that the window to intercept is limited by the mechanics and energetics of the interceptor launch and by the ability of the sensors to identify the threat early enough, as hypersonic intercept missiles are, because of their small size, relatively short range.
Existing sensors are far from adequate to deal with hypersonic cruise missiles, and if the hypersonic cruise missiles have stealth coatings, the problem is even greater.
This is an area DARPA (the Defense Advanced Research Project Agency) in the United States should be keenly focused on today, but isn’t. Because China and Russia will deploy tactical cruise missiles and could also start exporting these systems (for example, selling to Iran to give them an ability go after the US fleet and bases in the Middle East and the Persian Gulf or selling to North Korea to attack US bases and navy assets), the US need for capable hypersonic cruise missile defenses is urgent. But it does not appear presently to be a US priority. While it may be true that the US could attack Russian warships with hypersonic cruise missiles as a way of neutralizing them in a war, as hypersonic weapons proliferate, that option is not enough to protect our bases and our ships. The proverb “He who strikes first wins” is worth keeping in mind.