Explainer: What Are Hypersonic Weapons and Why Do They Matter?

The U.S. Defence Advanced Research Projects Agency’s Falcon Hypersonic Test Vehicle emerges from its rocket nose cone and prepares to re-enter the Earth’s atmosphere, in this illustration. Courtesy of DARPA

News Analysis

Talk of a new arms race between the United States and China has rapidly increased since a recent report by the Financial Times asserted that China had tested a nuclear-capable hypersonic weapon.

But what are hypersonic weapons? How do they work? Who has them? And why does it matter?

What are Hypersonic Weapons?

Technically, hypersonic weapons are missiles that travel faster than five times the speed of sound, or Mach 5. This speed is roughly 3,800 miles per hour, but fluctuates with the object, altitude, and temperature, as these interact with the physics of sound.

But speed is not the key defining feature of hypersonic missiles as traditional intercontinental ballistic missiles (ICBMs) also reach hypersonic speeds upon re-entry into the atmosphere.

Instead, the term has come to encompass a new type of weapon that is both fast and maneuverable. With a maneuverable trajectory not confined to a fixed parabolic arc of a ballistic missile, they can evade current missile defense systems.

The two main hypersonic weapon systems currently being tested around the world are hypersonic cruise missiles and hypersonic glide vehicles (HGVs).

Hypersonic cruise missiles are simply ultra-fast missiles powered by special jets, and which stay in the atmosphere for the duration of their use.

HGVs, meanwhile, are launched into low orbit by rockets in a similar manner to traditional ICBMs. Upon reaching orbit, however, the HGV and its warhead detach from the rocket and fly through the atmosphere using their own momentum.

HGVs are generally much faster than ICBMs while they are in low orbit, but become much slower upon hitting the dense air of the atmosphere as they have no jets to power them. At the height of their speed, however, they can fly up to 20 times the speed of sound (Mach 20), or roughly 15,000 miles per hour.

A primary disadvantage of HGVs is the significantly more costly research and construction processes required to build and field them.

Who Has Hypersonic Weapons?

China, North Korea, Russia, and the United States have all tested hypersonic missiles.

Additionally, Australia, India, Japan, Pakistan, and South Korea are all investing in hypersonic weapons research.

The only nations known to have working HGVs are China and Russia, whose respective DF-17 and Avangard systems entered service in 2019.

The United States is in the prototyping phase of several different HGV projects that are taking place across its service branches. Most notable among them is the Lockheed Martin Air-Launched Rapid Response Weapon (ARRW), which has been in development for the Air Force since 2018. Two of the three tests of the ARRW in 2021 resulted in system failures.

What is the United States’ Stance on Hypersonic Weapons?

Since the end of the Cold War, the United States has favored a policy of minimal deterrence, meaning that it has sought to maintain the fewest missiles and missile defenses possible while still effectively deterring adversaries from developing more weapons or attacking.

For a time, this strategy was effective as the United States held the most technologically advanced weaponry. With the advent of hypersonic weapons, however, the United States lost a critical ability to effectively deter Chinese and Russian aggression, and a report by the Congressional Research Service reiterated in 2021 that the nation lacked the means to defend against hypersonic weapons platforms.

Similarly, Robert Wood, the U.S. envoy to the U.N. Conference on Disarmament, delivered remarks in Geneva on Oct. 18, saying that the United States had “held back” from pursuing HGV technology for fear of inflaming an arms race.

As such, U.S. leadership largely regards the adoption of hypersonic weaponry by China and Russia as a destabilizing global event, that upsets the balance of power, and that will likely require a long-term rethink of established strategy to address.

What are the Implications for US National Defense?

The increasing development and use of hypersonic weapons, particularly HGVs, present several implications for the future of national defense.

None is more important, however, than the fact that the United States, its allies, and its enemies have no credible defense against most HGVs.

In the case of the United States, this is largely because the policy of minimal deterrence prevented the military from building many new, non-ballistic, capabilities.

For a time, this was strategically beneficial for the United States as the nation was effectively a unilateral weapons policymaker with the ability to intercept or prevent attack from any known ICBM. As such, virtually all current U.S. missile defense systems are designed to intercept ballistic missiles, and are located in the northern hemisphere, as previous ballistic technologies required missiles from China and Russia to arc over the north pole. And virtually all such systems are incapable of tracking or intercepting HGVs once they have detached from their rocket boosters.

This U.S. dominance in missile defense is a driving cause of Chinese and Russian hypersonic development, as neither nation is interested in continuing to develop weapons that they know the United States can defend against at will.

To that end, the race for superior hypersonic weaponry before the advent of technologies that can adequately defend against it serves to increase the potential risk to all nations.

“We just don’t know how we can defend against that technology,” Wood said on Oct. 18 about the issue. “Neither does China, neither does Russia.”

“This type of technology is worrisome, because we just haven’t had to face it before,” he added.

Correction: A previous version of this article misstated one variety of hypersonic missile. The Epoch Times regrets the error.