The Economist explains

What are the “hypersonic” missiles Russia has used in Ukraine?

Vladimir Putin calls the weapons invincible, but they may change little in the war

MOSCOW, RUSSIA - JUNE 24: MIG-31k fighter jet, with Kinzhal missile system, performs during Victory Day in Red Square in Moscow, Russia on June 24, 2020. Victory Day parades, commemorating the 75th anniversary of the victory in World War II, have been postponed from 9 May to 24 June due to restrictions imposed to prevent the spread of the coronavirus (Covid-19) in the country. (Photo by Sefa Karacan/Anadolu Agency via Getty Images)

Editor’s note (March 10th 2023): This piece has been updated after a Russian strike with hypersonic missiles on March 9th.

WHEN VLADIMIR PUTIN, Russia’s president, unveiled the Kinzhal ballistic missile in 2018, he called it an “invincible” weapon and lauded its “hypersonic” capabilities. Before the invasion of Ukraine there was no way to test that claim: hypersonic weapons had never been used in a war. But on March 9th, when Russia unleashed its biggest aerial assault in recent weeks, it struck with Kinzhal missiles. At least nine people have died, and the attack briefly cut off power to the Zaporizhia nuclear power plant. Russia had used Kinzhals before, in late January 2023. It also claimed to have used them in 2022, in the early weeks of the conflict, though those reports were not confirmed by Ukraine or its Western allies. Now there is no doubt. What are hypersonic weapons, and what effect might they have on the war?

Hypersonic weapons travel at around 1.6km per second, or more than five times the speed of sound. But it is not their maximum speed that separates them from other weapons. Long-range ballistic missiles, which fly in a high arc, reach similar velocities as they re-enter the atmosphere. Hypersonic missiles are distinguished by their ability to sustain those speeds at lower altitudes, and to manoeuvre while they do so (see chart).

They come in two types. Hypersonic cruise missiles are powered by rockets or jets throughout their flight. They are simply faster versions of existing cruise missiles, like the Tomahawk used primarily by America and Britain. Another kind, hypersonic boost-glide weapons, are different. They are launched into the upper atmosphere atop ballistic missiles, but then release unpowered hypersonic glide vehicles (HGVs) which fly lower, faster and—to an adversary—much less predictably than old-fashioned re-entry vehicles.

Both kinds pose a serious challenge to missile defences. Their speed gives adversaries less time to respond. Their manoeuvrability makes them harder to intercept. And the unpredictable trajectory for most of their flight allows them to hold a huge area at risk. They can even switch target mid-course. It could be mere seconds between the time the target is known for certain and the moment of impact. As well as the Kinzhal, Russia has tested a hypersonic boost-glide weapon called Avangard, which entered service in December. And it is not the only country experimenting with HGVs. China has been testing prototypes for years; America hopes to declare its own hypersonic cruise missile as ready for combat this year (though testing setbacks have delayed this). Australia, France, India and Japan are all working on hypersonic technologies of their own.

There is some dispute as to whether the Kinzhal is as revolutionary as Mr Putin would have the West think. Granted, it has a range of around 2,000km and a maximum speed of up to ten times the speed of sound. But when it was revealed to the world in 2018, many analysts pointed out its apparent similarity to an existing Russian short-range ballistic missile, the Iskander. The Kinzhal appears to be a modified version adapted to launch from a fighter jet. The Iskander, which has been used heavily in Ukraine, can reach hypersonic speeds, but not through a low, flat flight path, as a cruise missile can.

Even if the missiles are as advanced as Mr Putin says, they are unlikely to change the course of the war. Many of Russia’s conventional cruise and ballistic missiles are already finding their targets. American defence officials suggest that hypersonic boasts are mere propaganda, intended to send a message to the West about Russia’s capability and superiority. But they may also suggest a Russian weakness. As the war grinds on, Russia may be turning to the Kinzhal because it is running low on other precision-guided munitions. But, as British intelligence noted in November, stocks of the Kinzhal itself are “likely very limited”.

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