A missile interceptor test was a failure today. It followed several previously successful tests. This is a little misleading, however.

“We do not have an intercept,” said Air Force Lt. Col. Rick Lehner of the Pentagon’s Missile Defense Agency.

He said it was “frustrating and disappointing” that a glitch that had little to do with advanced missile technology had doomed the eighth, $100 million, flight test of a key part of a planned U.S. layered defense against ballistic missiles.

The problem was a failure of the payload to separate from the booster. This is a surprisingly common problem with space launch, and the failure means nothing with regard to the viability of missile defense per se. In a real situation, there would almost certainly be redundancy (multiple interceptors would be fired at a single target), and the failure of one to separate wouldn’t affect the ability of the system to kill the oncoming missile.

It also highlights the continuing failure of not just NASA, but the Air Force and Pentagon, to adopt a new space-launch paradigm. One of the reasons that these tests are so expensive and unreliable is that they are performed with expendable launchers, which are intrinsically expensive and unreliable.

While it’s unlikely that reusable launch platforms would be used for actual missile defense (the response time on them would probably be too slow), and the unreliability of expendables would be acceptable for the actual mission, for reasons stated above, it would be nice to have a cheaper, more reliable launcher for testing. At least one company is working on reusable suborbital systems that could do this, but they’ve received very little government support or encouragement.

But until we have a more reliable way of getting the interceptor to the target, it will continue to be difficult to separate out the real technical issues of missile defense from the more mundane ones of the reliability of expendable rockets. And many, intrinsically opposed to defending ourselves against missiles, will continue to point to such incidents as failures intrinsic to the concept itself, with the help of a scientifically-illiterate media.