17 December, 2004

Why Missile Defense is, and always will be, bunk

A few years ago I had the good fortune to attend a small lecture by Ted Postol, a professor in the MIT security studies program who has made something of a name for himself by trashing the Pentagon's claims about defensive missile systems. During the Gulf War he became notorious for demonstrating that the Patriot missile defense system that the U.S. deployed in Israel to stop Saddam Hussein's Scud missiles did not, in fact, have any successful intercepts. Postol blamed this on several factors, including the poor design of the Patriot and also the fact that Scuds frequently broke up while descending, making them difficult to hit. He reviewed video of many "successful" intercepts and showed that they were in fact, all of them, misses.*

More recently he has been one of the most prominent doubters of the proposed anti-ballistic missile shield (ABM). The basic technology of the ABM relies on an "exo-atmospheric kill vehicle" (EKV), or "interceptor". The reason why this technology is doomed to failure is simple and can easily be explained to your friends in a few sentences at a party: A ballistic missile is under thrust while it is in the atmosphere. While it is in the vaccuum of space, it is in free fall - a ballistic projectile (see any elementary physics text). The EKV works by identifying the path of the missile (through various technologies) and ramming into the warhead, detonating it in space. However, anyone who expects to run their missile through a defense system would be well-advised to attempt to foil this system, which can be done by dispersing decoys once you're in ballistic free-fall. The simplest possibility is balloons - metallic reflective spheres. You disperse a few dozen of these around your warhead, and now your EKV must select the correct target out of dozens of these, using some sort of image analysis technology.

Postol claims that it's easy to fool most of these by doing things like painting a stripe on your warhead or other simple visual tricks, and that even if the decoys are obviously different from the warhead the technology is unreliable. (Consider what a 5% failure rate implies.) But all of this is moot, since in the end, you can simply wrap your warhead in a balloon, making it literally impossible to pick it out.

Thus you should be properly outraged when next you read a news story discussing this technology that "fairly" but uncritically quotes both sides of the story, like the New York Times did this morning:

But a spokesman for Senator John Kyl, Republican of Arizona, a strong advocate of the program, said "one bum test" would not alter support for it.

Indeed, despite a series of delays in testing this year, Congress has embraced the deployment of a rudimentary system, which is favored by those who want to field even a limited system sooner rather than later.

Advocates say that fielding even a few interceptors of modest abilities, and improving them later, would help defend against potential threats that themselves are only just emerging, especially from North Korea's missile and nuclear weapons programs.

This is a scientific problem, and there is a reason ABM technology is derided by 99.9% of the physics community. A sensible debate should include explaining these simple facts to the public, which is, after all, bankrolling this assinine project.

* Not sure about "all of them", actually - one might have actually stopped its target.

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