This Is (Still) Our Best Shot At Taking Down A Nuclear Warhead

The guided-missile destroyer USS Fitzgerald (DDG 62) launches a Standard Missile-3 (SM-3)

Politech

Yesterday, an extremely important development seemed to get lost in the now typical daily chaos. For the first time, the United States attempted to intercept a real intercontinental ballistic missile fired from the Kwajalein Atoll with another missile launched from the coast of California. While that test was successful, it was met with the usual pessimistic responses quick to point out the mixed record of previous demonstrators and bring up possible countermeasures an enemy with nuclear warheads might deploy.

Should you take the articles at their word, you might conclude that trying to defend yourself against ICBMs is an impossible fool’s errand and a massive waste of money to boot. But while many experts keep scoffing at programs like this, it’s really important to keep in mind that intercepting an ICBM is really difficult and requires an incredible degree of precision. Of course the demonstrators have a mixed record. They’re prototypes trying to fight math and the laws of physics with brand new technology.

Failed tests have been caused by the slightest miscalculations and vibrations of the engines propelling the kill vehicles. ICBMs move at over 15,000 miles per hour and their apogee, or the highest altitude they can achieve, is 750 miles. For reference, the apogee of the International Space Station is roughly 250 miles. Pretty much the only thing that can stop it is another missile, and deviations amounting to no more than rounding errors in angle or speed can mean that the kill vehicle misses its target by the width of a small town.

On top of that, there are American and Russian experiments with building hypersonic warheads, which would be far too fast for anything but lasers to intercept. Plus, creating a missile able to hit another missile is quite literally rocket science, and given our current technology this approach might never be totally reliable. We seem to be making advances in reducing vibrations and calculating trajectories faster, but ultimately, we’ll hit limits imposed on us by friction and material science.

But hold on, if lobbing missiles at missiles is so error prone, why don’t we simply use lasers? After all, nothing with mass can move faster than light according to the laws of physics, and lasers are so accurate we literally use them for precision targeting. And wouldn’t lasers also eliminate many of the criticisms facing current missile defense efforts because they simply don’t have the same physical limitations as ballistic projectiles with mass?

All we need to do is increase their energy and suddenly, a means to track incoming doomsday weapons becomes a way to easily swat them out of the sky, right? Theoretically that’s perfectly plausible, practically it’s very, very difficult. You see, laser beams get exponentially wider with distance due to scattering as they move through a medium like water or air. This is known as decohesion and it can only be overcome by adding enough energy to keep scattering to a minimum and fight the inverse square law.

Unlike you see in sci-fi movies, lasers don’t instantly cut through anything in their range. Instead, they operate more like a blowtorch, burning through a target until it catches on fire or breaks apart. You could use a relatively small amount of power for an extended amount of time or an immense amount of energy over just milliseconds to achieve the same result; it ultimately comes down to what you’re trying to shoot down. Would the laser in question be able to keep up with it? What is it made of? Does it have armor?

Slower moving drones, mortar rounds, and even conventional missiles can be roasted over several seconds along their trajectory. An ICBM shielded to dive through the atmosphere just like a reentering spacecraft and capable of splitting into multiple independent warheads to cover a wide area is going to withstand a more or less conventional laser just fine. A beam that can bring it down would have to have an effective range of hundreds of miles, doing its damage within a second or two.

This has actually been tried during the 1980s under Project Excalibur, which was also mocked as Star Wars. It was an extremely ambitious design using a constellation of orbiting X-ray lasers no one was sure how to build. This idea would be streamlined into DARPA’s space based laser, or SBL. While we had a basic clue how to create an orbiting multi-megawatt laser by then, actually aiming it at incoming ICBMs proved to be a problem, even conceptually. In 2002, it was cancelled as well for something more practical.

The airborne laser initiative was supposed to be the more practical way of using lasers for missile defense, but even though it could burn up missiles, it could only do so as they were taking off, couldn’t do so reliably, and if it did, would require a whole fleet of Boeing 747s to patrol the skies non-stop for a chance to shoot down an ICBM at takeoff. The whole project was put out of its misery in 2009 and focus shifted back on the far more practical, though less reliable interceptors which are slowly being fine tuned for action.

But the moral of the story here isn’t to give up. All branches of the armed forces are working on powerful new lasers, or as they prefer to call them, directed energy weapons. Missile technology is getting better and ever more streamlined to help avoid the feedback from minor defects that will affect their real world accuracy. If just half of all incoming nuclear weapons in an actual bombardment are stopped, that’s millions of deaths prevented, so it’s more than worth the time and effort to keep at it.

Instead of looking at the mixed track record and cancelled projects with an acid pen, we should consider all these failures as stepping stones towards a very necessary task. While we rule out technology that doesn’t work and experimenting to find what does, we’re getting closer and closer to reliably shooting down incoming nuclear warheads from hostile nations. Right now, the most practical weapons may be interceptor missiles. When we figure out how to build practical long-range lasers, we could switch to them instead, giving the world a potential reprieve from a doomsday scenario.

This should not be an engineering program we dismiss as a pipe dream. It’s an imperative for our security in the future and rather than attempt our best Eeyore impressions when broaching the topic, we should be asking how to move it along and make it a top priority. Considering the stakes involved, we should really be talking about this a lot more than we are, and with a much more forgiving tone towards scientists and engineers battling nature to save millions of lives should nuclear powers ever decide to go to war.