Along with invading Ukraine, Russian President Vladimir Putin has put his country’s nuclear arsenal on high alert. He hopes by this measure to prevent the US or its allies from interfering militarily with his exploits, but by doing so he has provided an unpleasant reminder that Russia has more nuclear weapons than any other country in the world.  

According to Wikipedia, the Russians, with about 5,900 nuclear warheads, have a slight edge over the US with about 5,400. But considering that just one nuclear weapon can spoil your whole day, this is a distinction without a difference.

What if we could erect something like Israel’s Iron Dome system used against Palestinian rockets, a system that shoots down the vast majority, or even all, of a rival state’s intercontinental ballistic missiles (ICBMs)? Besides being able to cross that off our worry list, we could then unilaterally disarm ourselves from nuclear weapons, at least in principle.

There are several problems with that idea. One of the biggest, according to a recent article at Salon, is that we’ve tried building an ICBM defense system, and it probably doesn’t work.

I say “probably” because, thank God, it’s never been subjected to a real-life test. Termed the Ground-based Midcourse Defense system (GMD), it was designed primarily to guard against potential nuclear launches from North Korea. GMD consists of some 44 interceptor rockets stationed in Alaska and California. It’s been tested with dummy targets dozens of times since it was first deployed around 1999, and while its record would look pretty good as a baseball batting average, even one strike with a nuclear missile is too many.

Scientists consulted by Salon say there is no fundamental theoretical barrier that prevents us from developing a 100 percent effective anti-ICBM defense. But it’s a very hard technical problem.

An ICBM undergoes powered flight (the “booster phase”) for only its first three or four minutes. After that it goes ballistic, literally — meaning that it’s moving like a thrown rock in space, subject only to Newton’s laws and without any steering. This is the phase in which it is easiest to get a radar handle on where it is and where it’s going, and steer any prospective anti-missile weapons toward it. Once it gets close to its target and slows down in the atmosphere, it’s too late to do much about it, because blowing it up a few thousand feet above a populated area and scattering the radioactive residue all over would not be much better than just letting it do its job.

Also, modern ICBMs launch multiple warheads at the same time, some of which are decoys. This makes hitting all the real ones much harder, especially considering that each one is only about a meter long, according to one source. Against a single ICBM consisting of a single nuclear warhead, our GMD stands a good chance of whacking it out of the air. But a massive full-scale ICBM attack such as Russia would be able to do is far beyond GMD’s capabilities, and probably beyond the capability of any conceivable system we could put in place at a reasonable cost.

Suppose, however, the political will was there to mount an Apollo-space-program-style effort to design the ultimate ICBM-deflector, a US version of Israel’s Iron Dome that would really make us free from any concern about nuclear attacks by ICBMs. Would we want to deploy it?

For those of us with long enough memories, this was the ultimate goal of Ronald Reagan’s so-called Star Wars program, which never got very far. But if scaring the old USSR to pieces was the goal, Star Wars achieved its aims without even being built. Historians will argue till doomsday about the true causes of the USSR’s collapse, but Star Wars was certainly a factor.

The political prospects of the present US administration announcing something like Star Wars for the 21st century are about the same as the prospects of a snowball in a volcano. But if we built such a thing, would it be wise to scrap our nuclear arsenal and say that now we don’t have to worry about nuclear attack, we don’t need to threaten anyone else with it either?

That would certainly be an option, and if we did so it would be a sign that we really trusted our ICBM defenses. But I note that even with the Iron Dome, Israel has not divested itself of conventional rockets, and they hammer back at their enemies who throw rockets at them whether or not they land on Israeli territory.

Realistically, there are always going to be some regimes that won’t feel safe until they have nuclear weapons. North Korea is one such place, and currently Russia is another one. A major nuclear war anywhere in the world would probably be a global disaster, with dangerous levels of radiation rising into the stratosphere and coming down gradually everywhere.

While it would be nice to think that the world would follow our example and get rid of its nuclear weapons after the US did, all it would take is one holdout to spoil the game. And so it looks like the path to nuclear disarmament doesn’t lie along the lines of developing a really good ICBM defense system first and then getting rid of our own nuclear weapons.

As in other aspects of war, you never know for sure whether you’ve prepared adequately for the next war until you lose it. If you win, you might have gotten by with considerably less preparation than you did. So war is always a wasteful proposition, among its many other disadvantages.

The current war in Ukraine is tragic enough without pulling us closer to the brink of what has become for many the secular Armageddon, the nuclear end of the world. Let’s hope that the prospect of mutually assured destruction, which has kept us free from nuclear war for seven decades or so, will continue to convince Putin and others that the nuclear option is really no option at all.

This article has been republished from Engineering Ethics with permission.

Karl D. Stephan received the B. S. in Engineering from the California Institute of Technology in 1976. Following a year of graduate study at Cornell, he received the Master of Engineering degree in 1977...