The dream of a shield against nuclear bombs has been around since the earliest days of the nuclear age. The idea has always been deceptively simple: Build missiles that can shoot down nuclear-tipped intercontinental ballistic missiles as they come across the ocean from the Soviet Union toward the United States (or vice-versa). Although this would be the equivalent of trying to hit a bullet with a bullet or an arrow with an arrow, there have always been political and military leaders who feel sure it can be done.

The dream of a shield against nuclear bombs has been around since the earliest days of the nuclear age. The idea has always been deceptively simple: Build missiles that can shoot down nuclear-tipped intercontinental ballistic missiles as they come across the ocean from the Soviet Union toward the United States (or vice-versa). Although this would be the equivalent of trying to hit a bullet with a bullet or an arrow with an arrow, there have always been political and military leaders who feel sure it can be done. The most recent efforts began 27 years ago with the Strategic Defense Initiative of the Reagan administration — and have been pursued by missile defense agencies ever since.

Independent scientists and engineers in the United States and Russia have consistently judged past efforts to be failures, and they have written detailed reviews showing why the plans for such missile defenses are not technically feasible. Yet, in spite of these technical critiques and negative results, the US government has persisted in its claims of success. Until now.

A little-noticed report released in September 2011 by the Defense Science Board, an independent advisory committee to the US Defense Department, found three major problems with the Early Intercept Ballistic Missile Defense now being developed. Apparently, (1) none of the necessary radars in the European Phased Adaptive Approach defense system are powerful enough to work, (2) none of the existing missile defense sensors can reliably distinguish among warheads, decoys, and other debris, and (3) US intelligence already has observed foreign ballistic missile launches that can deploy decoys and other countermeasures. So, after 27 years of development and $150 billion spent, there still is no effective missile shield — it is still a dream.

From news of this report, we might conclude that the missile defense that we’ve all heard about for many years is now defunct. The system that Russia views as a threat to its security does not work, and, even if the problems could be remedied — a big if — the system would still not be operable for many years to come.

But a funny thing happened on the way to the NATO Summit. In the run-up to the May 20 conclave in Chicago, NATO officials are still talking about missile defense as if it were already a reality; in fact, later this month, they are expected to announce new plans for cooperation to deploy it in Europe. Furthermore, these same officials are actually angry at Russia for suggesting that it would preemptively strike the new system if it is deployed. Russia, apparently, still has the nerve to view the proposed system as a threat to its own missiles. Alas, this kind of thinking earned Russia a rebuke from the head of NATO, who called the Russians’ position “unjustified.”

Just to be perfectly clear: NATO is trying to cram down the throats of the Russians an imaginary ballistic missile system that, if it worked — which it doesn’t — could be used against Russian intercontinental ballistic missiles. Since NATO is treating the system as if it were a reality, Russia must as well. And so Russia insists it will take out the missile defense system by force if it is deployed, even though the system can’t possibly do what it’s supposed to do. So NATO and Russia are at each other’s throats over a weapons system that doesn’t work as intended and, if it did, could reasonably appear to threaten Russian interests, though NATO denies the claim. This is indeed “a riddle wrapped in a mystery inside an enigma.” But instead of Russia being the riddle, as Winston Churchill proclaimed in 1939, it is NATO’s plans for a missile defense that are the mysterious and enigmatic riddle.

There is hope, however, that this riddle can be solved. I’ve learned from ballistic missile expert Ted Postol of MIT that informal discussions among engineers and missile defense experts from the United States and Russia are taking place to bring clarity to missile defense plans. A meeting of Stanford University’s Center for International Security and Cooperation and the Russia Academy of Sciences’ Committee of Scientists for Global Security in September 2011 resulted in a joint statement on missile defense cooperation that recognized Russia’s concerns about the proposed US phased adaptive approach with its deployed interceptors and radars in close proximity to the Russian border.

The statement also set out four principles to guide ballistic missile cooperation: (1) missile defense should contribute, together with Russia, to the security of the Euro-Atlantic area; (2) NATO needs to take account of the possible impact of missile deployment on Russia, and Russia needs to take account of NATO’s concern about possible missile threats from Iran; (3) plans for ballistic missile defense should not place obstacles in the way of strategic cooperation between the United States and Russia; and (4) missile defense cooperation should be founded on principles of transparency and openness.

The most promising outcome of a subsequent meeting of the two groups in March was a proposal for American and Russian missile experts to collaborate on research and development of a “forward active defense” system that would replace the current phased adaptive approach — the one that doesn’t work. Collaborating on the newly proposed system would have at least two advantages: It would promote strategic cooperation between the United States and Russia as they collaborate to develop a joint ballistic missile defense system; and the proposed system just might work. We hope word of this proposed collaboration reaches NATO officials before the summit later this month. It would be a shame if NATO and Russia came to metaphoric blows over a defense system that turns out to be a mirage.