Test ban for hypersonic missiles?

If relationships between weaker and stronger nuclear weapon states are to remain stable, mutual assured destruction must be maintained in a robust, credible way. But nations' faith in the survivability of their nuclear deterrents could be seriously undermined by hypersonic missiles—either boost-glide systems or hypersonic cruise missiles—armed with conventional warheads. Some analysts in China suspect that the United States is seeking the ability to eliminate Beijing's nuclear deterrent in a first strike—and if Washington successfully develops hypersonic missiles, Beijing’s confidence in the credibility of its nuclear deterrent would only erode. (In a similar vein, Delhi might someday grow concerned about a Chinese hypersonic strike against India’s small nuclear arsenal.)

Already, some in China are discussing whether Beijing should, in the face of new conventional threats to its nuclear arsenal, alter its unconditional no-first-use policy. And a lack of understanding regarding future hypersonic missile policy has already begun to complicate strategic security dialogue between China and the United States—and between the United States and Russia. These countries' deeply-rooted mutual mistrust makes it inevitable that, if one nation deploys hypersonic missiles, another nation will perceive the threat in an exaggerated manner. Nations concerned about the survivability of their deterrents might build additional nuclear facilities deep underground—or begin to demonstrate less transparency about their nuclear policies. Such developments would hobble efforts to build confidence between national military establishments. Dialogue may help allay concerns—but only to a limited extent.

The greatest advantage of hypersonic missiles is their promptness, but promptness is also the technology's greatest source of risk. Decision makers in a crisis, if they wish to take advantage of hypersonic missiles' speed, will have to decide whether to launch preemptive strikes before fleeting windows of opportunity close. Risky decision making would be encouraged. And because hypersonic missiles would likely be intended for use against strategic targets—command and control centers, long-range surveillance systems, and even missile launch vehicles—conflicts could easily escalate if hypersonic missiles were used.

Tough obstacles. But can nations avoid a costly, technology-driven, hypersonic arms race by embracing preventive arms control? The prospects don't look very encouraging.

First, imposing technical limits on programs for hypersonic missile development would be difficult. No clear technical distinction can be made between hypersonic missiles and other conventional capabilities that are less prompt, have shorter ranges, and also have the potential to undermine nuclear deterrence. Nations would find it quite difficult to draw lines controlling the different technologies. Moreover, one possible US objective in developing hypersonic missiles is to gain the ability to preemptively strike small nuclear arsenals such as North Korea's—as opposed to, say, China's. But North Korea's nuclear and missile capabilities have been advancing quickly. By the time hypersonic technology is deployed, it may not be possible to structure US hypersonic capabilities in such a way that North Korea's nuclear weapons could be threatened but China's could not. And even if it were possible—through diplomatic arrangements or unilateral restraint—to keep US hypersonic capabilities limited to a small scale, Russia and China would remain concerned about the chance of future expansion.

Second, hypersonic systems are not necessarily intended only for delivering conventional weapons. Some nuclear weapon states, concerned about future advances in missile defense, are retaining the option of mounting nuclear warheads on boost-glide vehicles or hypersonic cruise missiles. Highly maneuverable systems such as these could significantly increase nuclear warheads' ability to penetrate midcourse missile defense. The stakes in developing hypersonic missiles are therefore high—higher than would surround the development of a new, purely conventional capability. So nations may be very reluctant to renounce hypersonic missiles.

Third, even though Washington may not be developing hypersonic missiles in order to target the nuclear arsenals of other major nuclear powers, some US analysts express interest in targeting such countries' non-nuclear strategic targets. Hypersonic missiles could become part of so-called "defense suppression" operations that would seek to counter the "anti-access/area denial" capabilities of China and others. Antisatellite assets could also become targets.

At a time such as this, when tensions between some of the major investors in hypersonic technologies appear to be rising, severe challenges face efforts to control such technologies. Increasing friction in the South China Sea is just one example of US-Chinese military tension in the Asia-Pacific region. In Eastern Europe, NATO and Russia appear headed toward a more hostile conventional military relationship. In such circumstances, national leaders are usually more interested in investing in new military technologies than in controlling them—especially technologies that may hold the key to prevailing on future battlefields.

Achievable steps. Given all this, banning research and development programs for hypersonic missiles will be difficult. Limited transparency measures, such as data exchanges and notifications, might be within reach—but even these mechanisms will require persistent effort and engagement from the major players.

In the short term, the best that can realistically be achieved might be unilateral risk reduction measures (backed up by diplomatic efforts that build confidence in these measures). For example, nuclear weapon states should for their own benefit refrain from developing strategies that involve using hypersonic missiles against nuclear targets. The 2013 US National Defense Authorization Act required the Defense Department to conduct a study on Washington's capability to "neutralize" Chinese underground networks, where some nuclear weapons are deployed, with "conventional and nuclear forces." Such a study suggests an actual interest in targeting nuclear weapons through conventional means—but anything of this nature should be scrupulously avoided.

Likewise, strategies that might exacerbate the "fog of war" should be carefully scrutinized. For instance, though preemptive strikes with hypersonic missiles against command, control, and communication centers might be a useful way to counter "anti-access/area denial" capabilities, they also risk "blinding" and confusing an adversary's leadership—to the extent that decision makers mistakenly believe a nuclear strike is under way. This would represent a serious risk of inadvertent escalation. Any strategy that blurs the line between conventional and nuclear warfare should be rejected. Nations deploying hypersonic weapons should vigorously pursue unilateral steps that will forestall destabilization—if in fact these technologies are going to be deployed at all.

Hypersonic missiles, if successfully developed, will cover long distances in a short time. Some observers argue that these missiles, in the hands of a nation that intended to overwhelm an adversary's early warning and missile defense systems, would pose a serious threat to global security and therefore should be banned. This is a contestable idea. The technology surrounding hypersonic missiles is still very much under development—but even if it is perfected, it will not add much to the security threats already posed by deployed weapons systems such as ballistic missiles.

Indeed, ballistic missile re-entry vehicles already operate at hypersonic velocities for a considerable part of their flight trajectory. For example, the re-entry vehicle of an intermediate-range ballistic missile whose range is, say, 3,000 kilometers travels at hypersonic speeds until it descends to an altitude of 30 kilometers (about 30 seconds from impact). But the threat that these weapons pose is generally accepted and accounted for. Sensors are capable of tracking ballistic missiles' flight. Missile defense systems are growing more robust.

The differentiation problem. Missiles travelling at hypersonic speeds—that is, at or above five times the speed of sound—offer the advantages of long range, high speed, and short flight times. No country has yet deployed a hypersonic system, but several are carrying out research and development. The main avenues of research are hypersonic cruise missiles and hypersonic glide vehicles. In nations pursuing hypersonic technology, glide vehicles appear to be the primary focus of development.

They can be used in combination with existing ballistic missiles (whether intercontinental, intermediate-range, or submarine-launched). The ballistic missiles would boost the glide vehicles to their release altitude, and the glide vehicles would then be allowed to glide downward at hypersonic speeds. Hypersonic cruise missiles, on the other hand, are boosted to operating altitude and velocity with an appropriate (non-ballistic) missile stage and are then powered by supersonic combustion ramjet (or scramjet) propulsion. The range of these missiles depends on the amount of fuel they can carry.

One potential problem that hypersonic missiles present is how to differentiate the launch of a conventionally-armed hypersonic glide vehicle or cruise missile from a strategic weapon launch. How are other nations to be certain what type of warhead a missile carries? Hypersonic missiles are also designed to be maneuverable—so it is possible to misunderstand a missile's intended destination. A nation might conclude, for example, that its nuclear forces were under attack when in fact its conventional forces were the intended target.

Impractical approach. The United States is the leader and trendsetter in hypersonic technology. Other countries are playing catch-up. China is now making investments in hypersonic missile technology, and more countries are bound to follow suit.

Whenever nations conduct tests that demonstrate the speed, range, precision, and accuracy of a weapons system, questions arise regarding that nation's intentions (as well as regarding the implications of the weapons system itself). Where hypersonic weapons are concerned, ambiguity surrounding national intentions is real. The result of this could be destabilization and perhaps even an escalatory conflict scenario. The solution to these problems, however, does not lie in banning hypersonic missile tests. Rather, it lies in understanding threats, managing them, and enacting confidence-building measures.

Even in the current scheme of things, with no hypersonic missiles deployed, ambiguity exists—when, for example, a nation's conventional and strategic missiles fall under a common command and control structure. And the missile launches of nations that carry out "anti-access/area denial" strategies can be ambiguous both in terms of warhead type and target.

Putting a moratorium on hypersonic testing is not the practical approach to solving such problems. The fact is that nations will make decisions about the deployment and testing of hypersonic weapons on the basis of relative power and competition. If the United States successfully develops hypersonic technology, one can be sure that Russia and China will do the same. Other countries, such as India, may follow. Nations at the early stages of hypersonic technology development won't wish to place themselves at a disadvantage to countries whose technology is more advanced. In fact, some nations would consider a moratorium on testing discriminatory.

And importantly, hypersonic technology has applications in the civilian space domain—in the areas of space transportation systems, re-entry capsules, and landing and reuse. Technological advancement in the civilian space realm requires testing, and nations with a stake in these civilian applications would oppose any mechanism that denied them the freedom to carry out tests.

Building confidence. Yes, hypersonic technology carries the risk that missile launches could be misidentified—but re-entry vehicles that are launched by ballistic missiles and re-enter at hypersonic speeds are not new. Understanding the re-entry trajectory of hypersonic missiles is complicated by maneuverable re-entry vehicles, but that is also true of existing ballistic missiles. The international community has responded to the ambiguity and escalatory risks of ballistic missiles with risk mitigation measures, detection and defense systems, and an effort to maintain a balance between deterrence and retaliation capabilities. This approach will need to be replicated for hypersonic missiles.

The United States has said it will use hypersonic missiles to supplement its conventional capabilities—not to deliver nuclear warheads. This is a welcome approach. Such a policy, from the very beginning of a conflict, could help keep the nuclear option at a remove. It is important for other nations developing hypersonic missile technology to adopt similar policies.

Another important step is to put in place confidence-building measures. These measures cannot involve only the United States and Russia, as often happened in the past; other countries that test hypersonic technologies, for either civilian or military applications, must be included as well. One important confidence-building measure would be to specify that hypersonic missiles will be used only with non-nuclear warheads. Other useful measures would include providing advance notice of tests; choosing separate, distinctive launch locations for tests of hypersonic missiles; and placing restraints on sea-based tests.

Technology for hypersonic missiles is still in the development stage. Production and deployment are not imminent. It is premature at this point to consider banning weapons tests—especially when hypersonic technology also has applications in the civilian realm. The best path forward is to use the time before deployment to debate the risks of hypersonic missiles and develop deterrents to their use—and to work out necessary confidence-building measures.

Hypersonic flight may sound like screaming good fun—but it’s not meant for you. It’s meant for weapons that would probably be used only in the opening salvos of a nuclear war.

No nation has yet succeeded in developing non-ballistic missiles that fly long distances at or above Mach 5 (five times the speed of sound), but the United States and China are conducting tests. Russia and India say they are jointly developing a hypersonic missile. Pakistan, of course, must do whatever India does. France will find that it cannot be France without hypersonic missiles, while Britain must never falter… and on and on it will go, in a new round of an old arms race that still leads only to stalemate or oblivion. Fortunately, there is a simple, risk-free, and highly verifiable way to avoid this dismal prospect: ban tests of hypersonic missiles.

Why does anyone want hypersonic missiles anyway? For more than half a century, ballistic missiles have provided the capability to hurl warheads above the atmosphere and hit any spot on the globe within minutes. The concept of hypersonic missiles, which would plow through the atmosphere at a fraction of the speed, has been around almost as long—but the extreme stresses, high temperatures, and corrosive effects of hypersonic flight have frustrated efforts to develop practical weapons. Ballistic missiles are simpler, cheaper, faster, and can reliably defeat missile defenses with lightweight decoys and other simple countermeasures.

With their high costs and small payloads, hypersonic missiles would be ill-suited to a sustained military campaign, but could be useful as tip-of-the-spear weapons. Armed with conventional warheads and their own kinetic energy, they could attack ships, radar and communications antennas, command and weapons bunkers, airfields, missile launchers, and other strategic assets. They could also carry nuclear warheads, and could fly in under the radars that watch for ballistic missiles. US strategists propose that hypersonic weapons could be used for “conventional prompt global strike” without the risk of being mistaken for a nuclear attack—yet Washington alleges that China intends its hypersonics for nuclear delivery.

Testing so far. Hypersonic missiles come in two main flavors: boost-glide vehicles and powered-flight cruise missiles.

For boost-glide vehicles, a rocket is used to launch a glider on a high trajectory into space. When it re-enters the atmosphere, the glider pulls up to fly horizontally, unpowered, for up to thousands of miles at initial speeds in the high hypersonic range, Mach 10 to 20 (about 7,000 to 14,000 miles per hour).

The United States tested a boost glide vehicle at the high end of this speed range in 2010 and 2011, but the tests ended in failure. Another program, the Advanced Hypersonic Weapon, aimed at lower speeds (around Mach 12) and reportedly experienced success in November 2011. But in a second test in August 2014, the same weapon blew up over the launch pad. China, meanwhile, conducted three tests of its own hypersonic glide vehicle, known as the WU-14, in 2014. China’s second test, in August, was a spectacular failure; the January and December tests are widely assumed to have been at least partial successes. A fourth test, also apparently successful, was reported just weeks ago.

Hypersonic cruise missiles, on the other hand, would be boosted initially by a small rocket and then powered by a supersonic combustion ramjet (or scramjet) for flight in the low hypersonic range—Mach 5 to 10, or around 3,000 to 7,000 miles per hour. They would cover distances up to about 600 miles. Such weapons would be ideally suited for naval strikes, land strikes from air or naval platforms, or cross-border surprise attacks between neighboring countries.

In May 2013, the United States became the only nation known to have successfully tested such a missile, the X-51A, a prototype for the planned High Speed Strike Weapon, which would cruise at about Mach 5. But China is reportedly working on similar technology and studying concepts for its use. Russia and India, meanwhile, jointly market a ramjet-powered supersonic cruise missile known as BrahMos, based on a Soviet-era design. They have announced a project to produce a hypersonic follow-on, the BrahMos 2, which they say will fly at Mach 7.

Testing no more. In the tests conducted so far, successes have demonstrated that it's possible to build functional hypersonic weapons—indeed, if work continues, hypersonics are likely to become reality over the next decade. Failures, meanwhile, show that developing reliable and militarily useful hypersonic weapons is impossible without testing.

A hypersonic test ban would be strong arms control. No nation would base preemptive strategic attack plans on weapons that have not been thoroughly tested, debugged, and proven reliable.

A ban would also be verifiable. While development of hypersonic missiles can be conducted in laboratories and wind tunnels to some extent, the kind of full-up tests needed to confirm performance and debug problems can only be carried out in the open air—in full view of sensors based in space, at sea, on land, and even in the hands of ordinary people.

It could begin with an informal moratorium. The United States, China, Russia, or India could initiate a moratorium by announcing that it was putting on hold plans for future hypersonic testing—while inviting other nations to postpone their own tests and to seek a permanent ban. In time, a convention could be organized where the precise parameters of a global ban could be negotiated and a formal treaty could be drafted.

Initiating or joining a test moratorium and adhering to a ban would involve little risk. Hypersonic missiles represent an escalation of strategic threat but are hardly sufficient to ensure a successful disarming first strike. And no nation would be able to secretly perfect and then mass-produce the weapons so quickly that rivals would have no chance to catch on and catch up.

Babies and bathwater. Some will argue that banning hypersonic missiles would prevent the development of hypersonic “space planes” that could cross oceans in an hour, or fly to orbit. In reality, the economics of such concepts are highly dubious. But a hypersonic missile test ban need not stand in their way. Missiles are easy to distinguish from the much larger vehicles that might make sense as space planes. A treaty could specify the technical criteria needed to make that distinction, as well as express the intent not to block peaceful activities.

Hypersonic missiles are just one aspect of a renewed strategic arms race among the world’s major nuclear-armed powers. Sources of this resurgent danger include smoldering geopolitical rivalries, shifts in economic power, and new weapons made possible by emerging technology. The world has failed so far to put the nuclear genie back in the bottle, and new genies are now getting loose: space weapons, cyber warfare, drones, and autonomous weapons. Weapons based on synthetic biology and nanotechnology loom on the horizon.

Seen in this context, a test ban for hypersonic weapons stands out as an easy and highly significant opportunity to resist an onslaught of destabilizing weapons technology. Let's just say no to hypersonic weapons.