A new focus on hypersonic glider weapons, after a reportedly successful Chinese test, is helping drive an arms race that is eclipsing hopes of a return to disarmament by the world’s major powers.
The Chinese test on 27 July, first reported by the Financial Times, involved putting into orbit a nuclear-capable glider, travelling at five times the speed of sound, which then re-entered the atmosphere and performed some turns on its way to a target.
The test suggested that China was further ahead with the technology than was previously known, and despite Chinese denials that it had tested such a weapon, the Biden administration has said it is concerned with the development.
Russia, which has already deployed its version of a nuclear-capable hypersonic glide vehicle, the Avantgard, announced it had conducted exercises in recent days to defend against hypersonic weapons.
The US has stepped up spending on its own hypersonic programme which, unlike its Chinese and Russian counterparts, is designed for conventional warheads only and is still in its testing phase. The Pentagon announced on Thursday that the latest test was called off after the failure of the rocket booster used to accelerate the weapon to hypersonic speeds.
The cluster of news stories about hypersonic gliders has added to the impression that the world is facing a totally new type of weapon with new capabilities. But all intercontinental ballistic missiles (ICBMs) travel at multiples of the speed of sound, and so the capability is almost as old as nuclear weapons themselves.
What makes hypersonic glide vehicles distinctive is that they are more manoeuvrable than the warheads on an ICBM, and therefore potentially more likely to defeat ballistic missile defence (BMD) systems. Some ballistic missile warheads have fins and can manoeuvre to a limited extent, but a glider can perform more pronounced turns, banking against the atmosphere. Jeffrey Lewis, a professor at the Middlebury Institute of International Studies at Monterey, likens gliders to an unmanned space shuttle with a nuclear bomb on board and no landing gear.
Lewis pointed out that making such turns also slows the glider down, making it considerably slower as it approaches its target than an ICBM.
“[The US] looked at gliding re-entry vehicles for our nuclear weapons and decided it wasn’t worth it because they slow down and we thought they’d be easier to shoot down,” he said.
What was most remarkable about the reported Chinese test was that it put a glider into orbit before bringing it down through the atmosphere. Such a weapon could in theory be used to attack the US from an unexpected and unpredictable direction, from over the South Pole for example, evading American BMD interceptors facing north.
It is thought likely that China is working on this technology to ensure that the US military never reaches the position of thinking it could launch a nuclear attack on China and then destroy all the missiles China fired back in response before they landed.
“In the last couple years China woke up and realized the risk of a conventional war with the US was higher than it’s probably been since the 1950s or 60s, and the US had a massive nuclear advantage it can use to prevent China from conventionally escalating a conflict,” said Vipin Narang, a professor of political science and expert on proliferation at the Massachusetts Institute of Technology.
“China realised it needed to compete with the US in order to stalemate us at the strategic nuclear level, to have a capability that could give the US pause before the US used nuclear weapons first in a conventional conflict.”
China has also built a lot more silos for ICBMs with the same goal in mind. While hypersonic gliders are receiving a lot of the attention recently, because of their relative novelty, many nuclear weapons experts argue that ICBMs equipped with multiple warheads in their own re-entry vehicles are a more effective way of countering missile defence.
“People tend to freak out about these weapons, but in certain ways these kind of gliders are not necessarily much more difficult to intercept than regular ballistic missile warheads,” Pavel Podvig, a senior research fellow at the UN Institute for Disarmament Research.
“If your goal is to defeat missile defence, then building these kind of gliders is not necessarily the way to do that. You could be better off, or at least not worse off, just by putting more warheads and decoys on your missile.”
Proliferation experts say there is pressure from the military establishment of all the major powers to hype the threat from adversaries and spend more on all the new weapons systems available. The US leaked reports about the Chinese test have come while the Biden administration is preparing its nuclear posture review and there is pressure building from the Pentagon to maintain the ambitious modernisation programmes started by the Obama and Trump administrations.
“It empowers those who are looking for continuity and/or expansion of missile defence or nuclear forces,” Narang said. “It’s hard to make the argument, when Russia and China are expanding, that the US should roll anything back.”