Can Ukraine's Air Defense Upgrades Stop a Russian 'Killjoy' Attack?

Ukraine's air defense system would only be able to shoot down a small percentage of the Russian hypersonic AS-24 "Killjoy" missiles British intelligence believes have been delivered to Belarus.

The United Kingdom's Ministry of Defence said Tuesday that it believes Russian Killjoy missiles are being held at Belarus' Machulishchy Airfield. Satellite images showed Russian jets parked at the field alongside a canister "likely" associated with a Killjoy air-launched ballistic missile, the ministry wrote in its daily intelligence update.

Killjoy missiles have several advantages over other missiles the United States has provided Ukraine, including M142 High Mobility Artillery Rocket Systems (HIMARS). For instance, they can carry a nuclear payload and travel up to speeds of about 9,000 miles per hour.

Iain Boyd, director of the Center for National Security Initiatives at the University of Colorado, told Newsweek Tuesday that Ukraine's current air defense system would only be able to shoot down roughly 20 percent of hypersonic missiles due to their high speeds.

Because the missiles travel so quickly, the reaction time from Ukrainian troops operating defense systems is "compressed," Boyd said. S-300 systems used by Ukraine have a range of 10 to 100 kilometers, and the Killjoy missiles can travel 3 kilometers per second, leaving only a small reaction time. Furthermore, the hypersonic missiles travel higher than the S-300, which maxes out at roughly half the speed of the Killjoy, he said.

"Your probability of success is less. If it gets past you—there's no way it can get past you because it's going twice as fast as you are," he said. "So I think that these systems that Ukraine has—they could probably shoot down some of those Killjoy systems."

The U.S. Department of Defense pledged Monday to send Ukraine eight NASAMS and associated munitions. NASAMS are short-range air defense systems. Raytheon Technologies CEO Greg Hayes told CNBC the defense system can "knock down everything in the sky from drones to ballistic missiles to fighter jets."

Boyd noted the NASAMS, which have a slightly larger range, could help Ukraine from a capacity perspective but would struggle to knock out many more of the Killjoys.

He added the NASAMS could deter Russia from using the Killjoys, instead opting to store them for only essential missions.

U.S. Still Developing Technology to Knock Out Hypersonic Missiles: Boyd

The U.S. military is still working on technology that would be more successful at defeating hypersonic missiles, Boyd said. For instance, the Missile Defense Agency is working on sensors in space that would help detect them earlier and longer-range radars—both of which would give the military longer reaction times. However, these technologies remain in early development.

"We really don't have anything today that would give a much better protection against these weapons," he said. "Most of the hypersonic weapons fired against the Ukraine, or us, today—most of them would get through. Not all of them, but most of them would."

As Putin finds himself a pariah among his European counterparts, Belarus' Alexander Lukashenko has emerged as a key global ally who has defended the widely condemned Ukraine invasion.

The placement of the hypersonic missiles in Belarus could allow Moscow military leaders to more easily strike key targets in western and northern Ukraine, as Belarus shares its southern border with Ukraine. Notably, it allows Russia to store the missiles closer to the Ukrainian capital Kyiv.

Still, British intelligence noted the placement may be more symbolic to "portray Belarus as increasingly complicit in the war."

Ukrainian armed forces spokesperson Yevhen Silkin cast doubt that Russia would launch attacks from Belarus. He said the probability, however, would depend on whether Russia can provide at least 50,000 troops as reinforcements through ongoing mobilization efforts. He also said the threat of an attack could grow "significantly" in 2023 if Russia struggles to meet its goals.