The U.K. has carried out a “major” test in its hypersonic weapons program in “close collaboration” with the U.S. government, the British Defense Ministry said on Sunday.

Why It Matters

Hypersonic weapons travel at speeds upward` of five times the speed of sound, also referred to as Mach 5 and roughly equivalent to over 3,800 miles per hour. The missiles are able to maneuver mid-flight, making them extremely hard to track or intercept.

They can be land-, sea- or air-launched, and are particularly suited to long-range strikes.

Russia has invested heavily in developing hypersonic missiles, storming ahead with its costly programs before hammering Ukraine with missiles like the Kinzhal and Tsirkon. Both were among the “super weapons” unveiled by Russian President Vladimir Putin in 2018.

While the Kremlin has flaunted its hypersonic weapons, Western experts have suggested the term is problematic—analysts often veer toward calling the Kinzhal an air-launched ballistic missile. Ukraine has said several times that it has intercepted Russia’s hypersonic weapons using U.S.-made Patriot systems.

What To Know

The British government said on Sunday that scientists had completed testing on an engine for an in-development “cutting-edge” hypersonic cruise missile, able to travel thousands of miles per hour.

The engine “successfully” showed how a high-speed, air-breathing propulsion system would work, the U.K. ministry said, unlocking a greater range than a conventional rocket.

The scientists carried out more than 200 tests at various hypersonic speeds at the NASA Langley Research Center in Hampton, Virginia, the defense ministry said.

The U.S. Air Force Research Laboratory, a scientific research arm of the military, was involved in the “extensive” tests over six weeks, London said.

Britain’s Defense Secretary John Healey said these tests were a “milestone moment on hypersonics research,” adding it was a “crucial area where we are working in lockstep with the United States.”

The U.K. said in November that it was accelerating “crucial” hypersonic missile development as part of AUKUS, the trilateral security agreement between the U.S., U.K. and Australia.

What People Are Saying

British Defense Secretary John Healey said it has “never been more important for us to innovate and stay ahead of our adversaries, equipping our forces with the technologies of the future.”

Paul Hollinshead, the chief executive of the U.K.’s Defence Science and Technology Laboratory, said: “This milestone represents a critical advancement in the UK’s defense capabilities and reinforces our standing in the AUKUS hypersonic weapon development collaboration.”

What Happens Next

The British Defense Ministry said it hopes to have a demonstrator missile ready by the end of the decade.