Revolutionary Velocity:

In early May, Iran unveiled what it described as the country’s first domestically produced hypersonic ballistic missile. Iranian state media published pictures of the Fattah missile at a ceremony attended by President Ebrahim Raisi along with members of Iran’s elite Islamic Revolutionary Guards Corps. Amir Ali Hajizadeh, the commander of the Islamic Revolutionary Guard Corps’ Aerospace Force, was quoted by state media as claiming that the Fattah had a range of 1,400 kilometers and could penetrate any missile defense shield, even Israel’s Iron Dome.

In parading its new missile, Tehran sought to score a public relations victory by tapping into international interest in this seemingly futuristic new missile technology. But does the hypersonic missile really represent a game-changing new capability for Iran?  

Hypersonic missiles travel through the air at least five times faster than the speed of sound (above Mach 5). Moreover, they travel on a complex trajectory that makes them difficult to intercept. The term "hypersonic weapons" generally refers to one of two different technologies.

First, there are hypersonic cruise missiles, which are similar to existing cruise missiles. Like airplanes, they sustain themselves in flight using aerodynamic lift and are powered by turbine engines throughout the journey. Second, there are maneuverable reentry vehicles, which are launched like ballistic missiles, with some differences. Whereas conventional ballistic missiles arc high above the atmosphere, maneuverable reentry vehicles are put on a trajectory that enables them to reenter the atmosphere fairly quickly and glide without engine power. These reentry vehicles can then glide through the air for hundreds or even thousands of miles, and are therefore also known as boost-glide vehicles. Both hypersonic cruise missiles and maneuverable reentry vehicles can potentially carry either nuclear or non-nuclear warheads.

Counterintuitively, it is perhaps boost-glide weapons with non-nuclear warheads that offer the most significant new capabilities for their possessors. Such weapons would allow Russia, which has put considerable time and money into developing its hypersonic capabilities, to threaten targets in Europe and even the continental United States with non-nuclear warheads. In the past, Russia could only have threatened such targets with nuclear weapons. The new generation of weapons are particularly potent because of their speed, range, and (especially in the case of cruise missile variants) maneuverability. But do hypersonic weapons live up to all the attention they are currently receiving?

Significant technical prowess was clearly necessary in order to design a weapon that could achieve speeds above Mach 5. This technology required a major leap forward in the development of low-friction surfaces to dissipate heat produced by air friction, as well as the invention of new materials that can handle high temperatures and high force on flight control surfaces.

A weapon’s usefulness also depends upon whether or not adversaries possess the means to blunt, deflect, or repel that weapon. In recent months, Ukraine has reportedly intercepted several Russian Kinzhal missiles, which travel at hypersonic speeds, using its US-supplied Patriot missile defense system.

It was widely believed that the Patriot and other existing missile defenses could not stop hypersonic weapons because of the latter’s speed. However, this turned out not to be true. Point-defense systems, especially the Patriot defense system and Terminal High-Altitude Area Defense (THAAD), are already capable of defending small areas against ballistic missiles. Ballistic missiles can actually travel faster than hypersonic weapons, but the former have no ability to maneuver. However, these defense systems can only protect small areas. "Area defenses" for hypersonic weapons across wider expanses of territory are more or less impossible.

Given the difficulties of defending against hypersonic weapons, it is not surprising that the world’s major powers are trying to outpace each other in this field. Many feel that the US is falling behind in hypersonic weapons technology since Russia and China have a much more active and visible testing regime.

In October 2021, the revelation that China had tested a nuclear-capable hypersonic glide vehicle sent shockwaves through the US defense community. But by that point, China already had developed the ability to attack targets belonging to the US and its allies with nuclear weapons. The new nuclear-armed boost-glide weapons merely reinforced the status quo.

In any case, the US is likely headed in a different direction than Russia and China, which appear to be primarily focused on the delivery of nuclear warheads. In the case of nuclear weapons delivery, accuracy is largely irrelevant. Meanwhile, Washington is more interested in the delivery of non-nuclear warheads, a field in which accuracy is the most important metric. In the latter case, weapons need to land within a few meters of their target in order to be militarily effective.

In many respects, the emergence of accurate non-nuclear boost-glide weapons, especially those capable of traveling vast distances, presents a new and very real technical and military threat to their potential targets. The prospect of proliferation given this deadly combination of speed, accuracy, range, and maneuverability poses a significant danger to international stability in the decades to come.