Setting the Record Straight on Hypersonic Weapons

, | February 3, 2020, 11:56 am EST
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Recent reports would have you believe that hypersonic weapons—an emerging class of low-altitude, high-speed missiles—are poised to revolutionize modern military strategy. A recent op-ed in the New York Times characterized these “game-changing” missiles as the “apotheosis” of airborne weaponry, capable of feats that “no missile can currently achieve.” This fantastical depiction, which underpins a race among the major military powers to develop these weapons, is part of a long pattern of media hype.

But are these weapons really so revolutionary? Will they upend the global security environment? And does their arrival make conflict between United States, Russia, and China inevitable?

Probably not. To determine what effects hypersonic weaponry might have on national and global security, and what advantages it might offer over existing missile technologies, it is necessary to first take a step back and assess precisely what these weapons can—or cannot—do. This means starting not from bombastic media reports, but from the fundamental physics of hypersonic flight. Recent work by Ivan Oelrich, for example, points out serious physical limitations to the performance of hypersonic missiles. After all, the United States has a history of pouring money into flashy weapons systems only to later find that the technology does not live up to the hype.

Looking at the problem in this way, hypersonic weapons lose much of their luster. They offer few advantages over existing missile technology, and many claims of their purported capabilities are distorted, exaggerated, or simply untrue. Below, I set the record straight on several of these claims.

Hypersonic weapons are not uniquely fast

“Hypersonic” refers to velocities greater than five times the speed of sound. This is many times faster than commercial airplanes. Some mistakenly claim that this speed allows hypersonic missiles to travel intercontinental distances—between Russia and the United States, for example—“within minutes.” This would purportedly halve the time a targeted nation would have to respond to an attack. This perceived threat has given rise to bizarre proposals for countermeasures, like the relinquishment of control over US missiles to an artificial intelligence.

This anxiety over missile delivery time represents a fundamental misunderstanding of not only hypersonic flight, but of missile technology in general. To be sure, hypersonic weapons are fast. But this is nothing new. Even the first modern missile, the German V-2, achieved near-hypersonic speeds in the 1940s. Intercontinental-range ballistic missiles, which the United States and Russia have fielded since the 1960s, travel much faster—more than 20 times the speed of sound.

Moreover, existing ballistic missiles possess a distinct advantage in terms of their flight paths. They are lofted high above the atmosphere before careening back to Earth. This means that they travel primarily through the vacuum of space, where they are unimpeded by air resistance. Hypersonic weapons, on the other hand, follow low-altitude flight paths through the atmosphere. Drag from the surrounding air robs these missiles of much of their speed by the time they reach a distant target, giving them an average speed lower than that of ballistic missiles. Just as ballistic missiles do today, hypersonic weapons would take a few tens of minutes to make the journey between Russia and the United States.

Hypersonic weapons do not strike without warning

With speed off the table, promoters have concocted other ostensible advantages of hypersonic weapons. For example, it is often argued that these weapons are “nearly invisible” in flight, and thus arrive “before any…meaningful warning.”

This concern over the detection of hypersonic weapons arises from their low-altitude flight paths, which can block line-of-sight from radar systems placed on the ground. Due to Earth’s curvature, these systems will not see a hypersonic missile until it is within a few hundred kilometers.

But again, there is much more to the story. Total reliance on ground-based radar for early warning of missile attacks is a relic of the past for technologically-advanced nations like the United States and Russia. Both have operated early warning satellites since the 1970s. These space-based sensors, which watch for the infrared light emitted by a missile launch, would detect a hypersonic attack just as easily as they would an attack with existing ballistic missiles. Even after launch hypersonic weapons emit a great deal of infrared light due to aerodynamic heating, enabling detection and tracking by a modern satellite system.

Hypersonic weapons will not render the United States more vulnerable to attack

Finally, there is the claim that hypersonic weapons are “virtually impossible to block,” such that “no existing defenses can stop such weapons.” Again, the reality is more complicated.

Hypersonic weapons may bypass some missile defenses, but not others. Local defenses protecting individual, high-value targets could be more effective against hypersonic weapons than they are against ballistic missiles, because hypersonic weapons travel more slowly by the time they reach their targets. Then there are area defenses, which instead seek to protect a large region, like the United States, by shooting down incoming missiles at long distances. Since these defenses are designed to intercept missiles above the atmosphere, they would be unable to stop hypersonic weapons travelling at lower altitudes.

But even these mixed results matter little, because many defenses already fare poorly against existing missiles. Modern defenses can be overcome through a variety of countermeasures, ranging from decoys to simply firing more missiles than the system can intercept. Furthermore, current US defenses are not designed to defend against Russia and China, the nations currently deploying hypersonic weapons. The United States will therefore remain vulnerable to missile attack regardless of whether or not hypersonic weapons are deployed.

Takeaways

Much of the hype behind hypersonic weapons does not hold up to the physics. These weapons will not reach the United States more quickly than existing missiles, will not strike without warning, and will not alter the fundamental balance between missile offense and defense. Alarmist rhetoric that casts these missile as revolutionary, and their acquisition as a national imperative, will do little more than enrich weapons manufacturers, for whom they represent a cash cow.

Despite the prevalence of misinformation, a few rightly point out the superfluous nature of these new missiles. If policymakers can be convinced of this, these weapons could easily be incorporated into existing arms limitation treaties, and a harmful, expensive arms race might be halted before it is too late.

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