What are hypersonic weapons and how can we limit their spread?

Nearly four years ago, Russia brandished one of its newest armaments during a Victory Day parade in Moscow: a hypersonic missile that was fastened to a fighter jet, and described as a “doomsday super weapon.”

About four days ago, Russia reportedly made the first use of a hypersonic weapon in combat, during an attack in western Ukraine.

They’ve been a source of growing anxiety and a secretive arms race for years – yet there haven’t been any broad, multilateral efforts made to limit their spread.

They can fly faster than five times the speed of sound, but that isn’t their only distinctly dangerous quality. They’re maneuverable, could be used to modernize nuclear arsenals, and may eventually be released from space in ways that evade missile-defense systems. US systems facing north in anticipation of an attack, for example, may now suddenly be useless against missiles approaching from the south.

Some experts have dismissed the strategic value of Russia’s hypersonic weapons used in Ukraine. Others downplay the significance of the weapons more generally. But most seem to agree that the escalating pursuit of their development presents a real risk. “There is probably less than a decade available to substantially hinder the potential proliferation of hypersonic missiles,” the RAND Corporation warned us. That was about five years ago.

A report published by the UN in 2019 suggested an outright ban – or at least restricting hypersonic weapons systems to those countries that already have them.

In addition to Russia, countries believed to have hypersonic weapons programmes include the US, China, Australia, India, France, Germany, and Japan.

Some or all of these countries have been parties to global efforts to govern the use of nuclear weapons over the years, ranging from the Antarctic Treaty to the Treaty on the Non-Proliferation of Nuclear Weapons. Collectively, these have spurred healthy engagement and led to the destruction of large numbers of arms.

However, there are fewer nuclear arms treaties in effect – so, fewer that could be expanded to address hypersonic weapons. None of the countries thought to have hypersonic weapons programmes have signed the Treaty on the Prohibition of Nuclear Weapons that entered into force last year, including the only country to ever experience the trauma of nuclear weapons firsthand.

The US decision to withdraw from the Anti-Ballistic Missile Treaty in 2002 has actually been cited as motivation for Russia to push forward with a hypersonic weapons programme.

New START, the only remaining nuclear arms-control agreement between the US and Russia, only indirectly addresses hypersonic weapons – which has been described as “better than nothing.”

Now, Russia’s invasion of Ukraine and growing isolation may be catastrophic for global arms-control efforts generally.

The broader context for the development of hypersonic weapons is a notable increase in overall global military spending. According to one measure, spending rose in 2020 by its sharpest annual rate since the financial crisis, even as global GDP contracted.

Another analysis found that spending edged even higher in 2021, at least in nominal terms (surging inflation resulted in a decline in real terms). It noted that hypersonic “boost-glide” vehicles that can cover long distances in unpredictable ways are often conflated with hypersonic cruise missiles, though both present challenges for missile defenses.

In the US, the Navy requested $1.4 billion for fiscal 2022, an amount larger than some countries’ annual GDP, for its Conventional Prompt Strike hypersonic weapon system.

The hypersonic arms race will likely outlast the fighting in Ukraine, and may draw more countries into a costly and unnerving game of one-upmanship.

“It’s a consequential weapon,” US President Joe Biden said recently of the hypersonic missiles apparently used by Russia. “It’s almost impossible to stop it.”

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