China’s DF-17 is likely to be the first hypersonic boost-glide system to enter military service, but other hypersonic weapons will soon follow, both unpowered and powered.

If the proliferation of such systems and its impact are to be managed, arms-control measures will be needed. However, demanding enough within a stable security architecture, arms control is far more difficult when the supporting structures are already collapsing, as shown by the failure of the Intermediate-range Nuclear Forces Treaty; arguably it also becomes the more valuable.

For decades an expensive laboratory pastime, hypersonic glide vehicles and hypersonic cruise missiles are no longer tomorrow’s weaponry. For hypersonic glide systems that day is now, and in a period when major-power consensus on security has collapsed. The timing is not propitious.

From flash to bang

The military attraction of high-speed weaponry in compressing the time taken from flash to bang is easily grasped. It increases the survivability of the weapon and decreases the target’s ability to react. Even if the opponent can react, engaging a high-speed weapon that is manoeuvring in the upper atmosphere is demanding (though not impossible).

The hypersonic flight regime is considered to begin at Mach 5. The first generation of glide-vehicle weapons may be sub-Mach 10, while for cruise missiles, the first-generation systems in states’ inventories may be in the Mach 5–7 range.

The DF-17 was shown in mock-up form during China’s 70th anniversary parade on 1 October 2019, while the transporter-erector-launcher vehicle for what was called the CJ-100 missile was also displayed.

The CJ-100 appears to be comparatively high-speed, high-altitude land-attack cruise missile. It is not known whether this weapon has a high supersonic speed (around Mach 4) or whether it can achieve even higher speeds. The operational statuses of the DF-17 and the CJ-100 remain to be ascertained; however, China claims both are in service with the People’s Liberation Army.

Beijing’s ambitions are matched by those in Moscow and Washington, with glide-vehicle and air-breathing-propulsion approaches being vigorously pursued. Russia’s Avangard boost-glide system is nearing service entry and could enter the armed forces’ inventory in 2020. A Mach-5-plus cruise missile is also being tested by Moscow. The United States, meanwhile, has a slew of high-speed-weapons projects being pursued by the air force, navy and army, while France and India are also undertaking hypersonic-weapons design work.

Operational use

The roles envisaged for these systems are numerous, but this is also part of the problem from an arms-control perspective. The boost vehicle for Russia’s Avangard uses an intercontinental ballistic missile and would therefore seem to have a ‘strategic’ role in terms of Russia’s nuclear-weapons doctrine.

The Chinese DF-17, however, is based on a medium-range ballistic missile and would therefore have only a ‘theatre’-level role in any China–US military confrontation, although it would have a longer-range ‘strategic’-level capability against regional opponents such as India or Japan.

Ambiguity is a feature of deterrence. A lack of certainty should foster caution but could risk miscalculation or pre-emption

While the assumption is that the Avangard would be nuclear-armed, there is greater ambiguity concerning the DF-17. Statements coming from China suggest it is fitted with a conventional warhead. However, such a system invites a dual (conventional and nuclear) capability.

Deterrence

Ambiguity is a feature of deterrence. A lack of certainty should foster caution but could risk miscalculation or pre-emption. Present hypersonic developments compound this ambiguity, with nations pursuing both tactical and strategic roles for such weapons. Current development paths may invite worst-case scenario assumptions on the part of an opponent.

Faced with the compressed decision timelines created by an incoming hypersonic weapon and uncertainty regarding the nature of the payload and the scale of the attack, the intended target may assume the worst. Indeed, high-speed weaponry could bring about a return to a ‘launch on warning’ doctrine on the part of some of the major powers.

The Russian regime’s world view already includes the threat of a decapitating attack by the US through Prompt Global Strike using long-range precision weapons. The addition of hypersonic weapons to the United States’ inventory will only fuel these concerns, whether they are justified or not.

However, the proliferation of hypersonic weapons is unlikely to mirror that of current-generation subsonic cruise missiles, since the costs of entry and accords like the Missile Technology Control Regime (MTCR) will act as barriers to prospective operators. Nevertheless, given the current impetus behind developing hypersonic technology, its entry into the inventories of the major powers is inevitable.

From an arms-control perspective, there will likely only be a limited number of countries that will field hypersonic glide vehicles or hypersonic cruise missiles. While any arms-control agreements would eventually need to be multilateral to be fully effective, the number of signatories to a hypersonics treaty would be nowhere near as large as, for instance, the MTCR. And even a bilateral accord between the major powers would be good place to begin.

Unstable at speed: hypersonics and arms control, Douglas Barrie, the International Institute for Strategic Studies