You’ve heard of supersonic: 1.2 to five times the speed of sound. Hypersonic missiles, while not as fast as ballistic missiles, travels at five to 10 times the speed of sound. What exactly are they? At the Bulletin for Atomic Scientists, Mark Gubrud reports. (Emphasis added.)
Hypersonic missiles fall into two distinct categories. In what is known as a boost-glide weapon, the hypersonic vehicle is first “boosted” on a ballistic trajectory, using a conventional rocket. … it glides at hypersonic speed toward its final destination.
Hypersonic cruise missiles, on the other hand, typically are launched to high speed using a small rocket, and then, after dropping the rocket, are powered by a supersonic combustion ram jet, or scramjet, for flight at five times the speed of sound (some 3,800 miles per hour) or greater.
Their raison d’être?
In the US, hypersonic missiles have been billed as a method for quickly delivering conventional warheads when time is of the essence; one example often given is attacking a terrorist stronghold promptly when intelligence indicates the opportunity to kill a high-value target.
Though, in fact,
… the most successful attacks in counter-terrorism operations have been launched not from thousands of miles away but from nearby, using ground forces, manned aircraft, or drones.
More to the point, hypersonic missiles are viewed as a way of emulating a nuclear strike with conventional weapons. As Gubrud writes
Some proponents are more open in contending that hypersonic weapons should be developed to provide a capability for attacking strategic military targets within the territory of a major military power, including … key radars and associated systems, command and control nodes, long-range surveillance systems, and … ships in port.
Proponents also claim
… that the use of hypersonic weapons with conventional warheads (or pure kinetic energy) would permit such attacks to be carried out on the home territory of a nuclear power without the risk of a nuclear response.
Why do they believe that?
The vague reasoning is that the different flight profile of these weapons would distinguish them from nuclear ballistic missiles, and the Chinese (or Russians, in some other scenarios) would trust that American hypersonic missiles do not carry nuclear warheads.
In fact, though
US non-nuclear hypersonic weapons could well be targeting nuclear weapons and supporting facilities, possibly in preparation for a follow-on nuclear strike. Furthermore, there is no physical reason why hypersonic missiles could not deliver nuclear warheads.
Chinese and Russian officials have indicated they fear that US hypersonic weapons could be used to lead a nuclear first strike, and both those countries have begun hypersonic missile programs of their own, suggesting that, absent controls, a full-scale hypersonic arms race is just around the corner.
The United States maintains that hypersonic missiles can’t be mistaken for ballistic missiles (often armed with nuclear weapons). However, Gubrud writes:
The idea that they might be used to attack a nuclear power, because they would be easily distinguished from ballistic missiles and the enemy would be willing to believe that no hypersonic weapon carried a nuclear warhead, can hardly be considered stabilizing. Rather, it is a challenge to nuclear deterrence and a threat that potential adversaries have to take seriously. They will respond by seeking countermeasures, including symmetrical capabilities, as China and Russia are doing, via their own hypersonic missile programs.
The development of hypersonic missiles resembles the development of missile defense in that the United States thinks other countries make too big a deal out of it and refuses to see how it might be a threat to other states. But, Gubrud maintains
To imagine that a strategic attack could be carried out on military forces based in the homeland of a major nuclear power without the risk of a nuclear response is a dangerous fantasy. But the race to develop and deploy hypersonic weapons is serious.
Gubrud calls for an international ban on hypersonic missiles and proposes “that the United States suspend testing for a while, to show good faith as it seeks agreement on an international ban on hypersonic testing.” Demonstrating leadership on nonproliferation by substantively disarming? That would constitute a dramatic about-face for the United States, which seems intent on cracking the whip on a country such as Iran that has barely entertained the notion of developing nuclear weapons while it modernizes its own nuclear stockpile to ensure its existence in perpetuity.