Why scientists still don’t know how to intercept nuclear missiles

Amid the Russian invasion of Ukraine, the specter of nuclear war hovers in the public mind in a way not seen since the Cold War.

Indeed, as the international community slaps Russia with an array of restrictions and sanctions, it’s hard not to slip into a worst-case nuclear scenario, especially since Russia has the largest stockpile of nuclear weapons in the world. world. More alarmingly, Russian President Vladimir Putin recently put Russian deterrent forces on high alert, including nuclear weapons.

Many experts agree that this level of threat is unprecedented in the post-Cold War era. But given how far computers, drones, and laser technologies have come since the Cold War era, you’d think advanced technology could deter a nuclear threat. Indeed, in 1983, President Ronald Reagan announced the launch of a program – derisively called “Star Wars” by critics – by which America could protect itself from strategic ballistic nuclear weapons from space.

Yet 39 years have passed since that announcement. So, are we there already? In other words: if the army of a foreign country launched, for example, an intercontinental ballistic missile (ICBM) – that is, a missile with a minimum range of 5,500 kilometers – the United States Could United or another country block or intercept it?

Engineers have pondered this question for decades. Yet, curiously, and despite monumental advances in physics, computing and AI over the past four decades, the technical problem of missile interception has yet to be solved.

“There’s no law of physics against the prospect of intercepting them, but the laws of physics make it extremely difficult – and create all these constraints on how difficult it will be to intercept it,” physics professor James Wells at the University of Michigan, says Salon.

But Wells noted that such a thing is certainly physically possible. “There is no theorem that says ‘we cannot achieve missile defense’,” he added.


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Technically, the United States Is have a defense ICBM missile system. It’s called Ground-based Midcourse Defense (GMD), and it’s the only system currently deployed to defend the continental United States, with 44 interceptors based in Alaska and California. Unfortunately, that probably doesn’t work.

A recent study sponsored by the American Physical Society concluded that GMD cannot be relied upon to counter even a limited nuclear strike. The study specifically focused on North Korea’s ICBMs and determined that the US defense systems in place are unlikely to be reliable enough to guarantee mission success within the next 15 years.

Experts tell Salon that despite advances in technology, as Wells noted, there are several reasons why this is such a difficult problem to solve, scientifically speaking. The main reason is that it is simply extremely difficult to intercept something so small (about a meter long) moving so fast (15,000 miles per hour) in such a short time. Not to mention that part of the trajectory of these warheads takes place in space.

“It’s a really, really tough job,” Dr. Laura Grego, a Stanton nuclear security fellow at MIT’s Nuclear Security and Policy Laboratory, told Salon. “One of the reasons it’s so difficult is that the timelines for a nuclear armed ICBM attack are very short from launch to landing – it’s going to take 30 or 40 minutes – your defense has to be ready and effective on these deadlines.” Likewise, as Grego noted, “because the stakes are so high, it really has to work almost perfectly the first time.”

Indeed, the trajectory of an ICBM has three different phases: the acceleration phase, the mid-course phase and the terminal phase, all of which generally take place in less than an hour from launch to strike. Grego explained that engineers have long targeted the mid-course phase, when the ICBM is coasting after launch to its destination, as an optimal time to intercept.

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Grego said ICBMs are, by design, difficult to intercept. The warheads, which are multiple and emerge from the cone of the missile, are “relatively small”, making it difficult to attack. Some of these warheads could be decoys and contain nothing. Similarly, the ICBM’s journey takes it through the vacuum of space – where, as Grego puts it, “you have no air resistance or very little air resistance, so a light decoy is not slowed down compared to a heavy warhead.”

It is therefore difficult to decipher which is the real warhead and which is or are fake. Grego explained that this is called the “discrimination problem”.

“You’ll have to figure out what the real warhead is, what the real threat is, and what the decoys are,” Grego said, noting there’s about 30 minutes allotted to figure that out. Another option would be to intercept all decoys, but Grego said that might not be feasible in such a short period of time.

But what about trying to intercept the ICBM during the boost phase, before the warhead and decoys are deployed?

“This part of the trip is really only three to five minutes, depending on the type of launch missile,” Grego said. “It’s just active power stealing for three to five minutes.”

This window is extremely short and therefore incredibly difficult to figure out how to intercept, Grego noted. In order to intercept the missile during this phase, the defender would need to be very close to the launch site to arrive in time.

Wells added that there are concerns that interception during the boost phase could detonate the warhead in friendly territory.

“It’s a famous ‘missing problem’, as they call it – where you intercepted it, but the warhead continues,” Wells said. “There are some significant issues and you really need to make sure you’ve neutralized the ICBM’s ability to do damage, and that’s an additional issue in the storyline.”

Experts say it’s not impossible to create a robust and reliable ICBM shutdown system – but it is certainly very difficult.

“The stakes are so high that you want to rely on an almost foolproof system,” Grego said. “You would want a system that you can rely on that would eliminate the death and destruction that a nuclear attack would have, and that’s very hard to do reliably.”

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