What Are Hypersonic Weapons And What Threat Do They Pose?

As 2018 was on the way out, Russia successfully tested its ‘Avangard’ hypersonic glide vehicle, demonstrating how far it had come in developing hypersonic weapons. The test was conducted at the Dombarovsky missile base in the southern Urals and hit its target some 6000 kilometres away in Kamchatka. Russia joins China, the U.S. and India in a global shift towards developing such weapons because of the strategic advantages that they come with, though fielding such a weapon is no easy engineering feat, especially thanks to the high speeds and propulsion systems required. So what are hypersonic weapons, what strategic advantages and dangers do they bring, why are more states pursuing this technology and will it threaten global peace?

A hypersonic weapon, be it a glide vehicle, cruise missile or other aircraft is defined by its ability to travel at speeds in excess of Mach 5, or at least 5 times the speed of sound. Considering that jet airliners travel just below the speed of sound and that fighter jets travel at around Mach 2, the prospect of sustained flight above Mach 5 poses unique engineering challenges, namely a thrust system that can maintain above Mach 5 flight, heat resistant materials, and fitting a weapons system including guidance and warheads into a working and coherent weapon. In terms of propulsion for non-glide vehicles, so called ‘scramjets’ are used to sustain flight at hypersonic speeds. These systems differ from other jet engine types in that they utilise supersonic combustion (i.e. supersonic air flows through the inlet, is compressed, combusted and then exhausted at supersonic speeds) making them highly efficient at very high speeds. Another element to consider in the design of such weapons is material composition since it is travelling through the air at such high speeds, with Senior Engineer Rich Moore from the RAND corporation in a recent video stating “you can think of it as flying through [a] blowtorch.”

The obvious advantages of a hypersonic weapons system at the strategic level relate to speed, not only of the weapon itself but also of the time it would take to effectively respond if launched into another state. The two emerging types of hypersonic vehicle being tested the most include the hypersonic cruise missile and the hypersonic glide vehicle. For a cruise missile to travel at hypersonic speeds it requires a scramjet to maintain above Mach 5. Conventional cruise missiles utilise engines allowing for a maintainable supersonic flight along a low trajectory. Most that are deployed across countries today can travel between 300 and 5,000 km to their target using guidance systems on board, and it is this autonomy that makes them so effective. A hypersonic cruise missile would grant the capability to travel further, faster, and travelling at Mach 5 could allow a transit time of 50 minutes for a target 5000 km away. Hypersonic glide vehicles work similarly to nuclear warheads on an inter-continental ballistic missile (ICBM), in that they are mounted onto a rocket and re-enter the atmosphere. The key difference lies in the fact that it can glide and manoeuvre above the atmosphere for thousands of kilometres before reaching its target, meaning that, unlike nuclear missiles designed during the Cold War, which utilised ballistic trajectories (determined by calculating velocity, air resistance and gravity), the true target of the glide vehicle can remain unknown until the very last moment. Capitalising on this strategic unpredictability is the primary goal of any hypersonic system, especially since it takes time to determine what an object is and what its intentions may be before deciding on an appropriate response.

Moving away from the technical aspects, it is very evident that these weapons systems have the capability to strike a target with extreme speed and with very little warning. Conventional methods of nuclear missile defence utilise complicated guidance systems and must hit the target as it ascends to space. Whilst very much possible, missile interception is still an extremely difficult feat limited primarily by range, with the American THAAD system fielding a range of up to 200 km. Hypersonic weapons with current technology would be virtually unchallenged on their trajectories due to their combination of sustained speed and manoeuvrability and would also provide minimal warning time.

Strategic time has demonstrated itself an essential component in nuclear deterrence. During the Cold War, there were many times where either side detected rocket launches and perceived their foe as having hostile intentions. A notable example occurred post-Cold War in 1995 after the Norwegian Black Brant XII research rocket was launched, prompting then Russian President Boris Yeltsin to activate a nuclear briefcase and ready nuclear submarines for a strategic launch. Thankfully, following a period of time, the true nature of the rocket’s launch became clear and Russian nuclear forces were stood down. Any transparency or predictability shared at this strategic level is destroyed with the use of a hypersonic weapon, and similarly to how cyber weapons are used, they can be plausibly denied and can strike without warning. Additionally, given the compressed time frame a hypersonic weapon would provide national commanders and leaders to respond, command authority may be forced to divulge to senior military leaders as opposed to political ones, speeding up the decision-making process but also increasing the probability for a misunderstanding to be met with a forceful counter-attack.

Currently, the three most powerful states in terms of military power possess the potential to deploy these hypersonic weapons within a matter of years. Russia’s Avangard system has already entered service with the Russian nuclear forces in March 2018, with China’s DF-ZF and the American HTV-2 remaining in the experimental phases, though the U.S. claims it has maintained the capability to field these systems for many years, with a U.S. Defense Department official, Lieutenant Colonel Michelle Baldanza claiming, “While the United States has been the world leader in hypersonic system research for many decades, we did not choose to weaponize it.”

Given the unstable climate in terms of nuclear non-proliferation following the U.S.’s withdrawal from the INF treaty unless Russia destroys all of its violating missile launchers and equipment, the prospect of an even more uncertain future given the rapid destructive capabilities posed by hypersonic weapons is of considerable concern. States should explore the prospect of non-proliferation treaties to the end of greater transparency since a treaty’s obligations may offer some of the only predictable measures surrounding the use of such weapons systems. Numbers deployed, stockpile size and platform types would be important factors should a treaty ever be devised. Richard Speier, a political scientist with the RAND corporation attests that “it is in [Russia, the US and China’s] interests to do this,” in relation to the conception of such a treaty, and would also legitimise and control the exportation of such technologies to more unstable actors to prevent any rogue misuse.

In the current climate of strategic uncertainty that comes as a product of highly sophisticated weapons technologies, the need for states to recognise and create a degree of transparency is paramount. Though in the Cold War age of ballistic nuclear trajectories and slower delivery systems time was more plentiful, allowing for greater discretion, the weapons of the future may eradicate time as a factor in deciding how to respond altogether, increasing the potential for accidental retaliations and conflicts to brew as a result.

Sam Raleigh