Much publicity surrounded last weekend’s failed test of the Clinton administration’s national missile defense (NMD) system, but the results of that test are overrated--both technically and politically.

Charges by opponents of missile defense that the program is doomed to failure ignore testing glitches in the development histories of almost all successful weapons programs. Because the intercept test was only the third of 19 planned, there will be many other chances to perfect the technology. Moreover, President Clinton will not decide whether to deploy the system on the basis of the results of the third test. The administration has hinted at a more limited decision, namely calling the system merely “feasible.” That wiser decision will leave the hard choices to the next president.

The next president will have to decide whether to continue the limited land-based system now under development or move to consider sea-based and space-based options. Texas Gov. George W. Bush has hinted that he might be inclined toward the latter approach. Curiously, both conservatives and some members of the arms control community favor a sea-based approach; the arms controllers want to save the Anti-Ballistic Missile Treaty, and the conservatives want to destroy it to build more comprehensive missile defenses. But in the mad rush to embrace sea-based NMD systems for political reasons, the proponents of such systems brush aside important technical and operational concerns.

Both conservatives and arms controllers claim that the future Navy theater missile defense system on Aegis ships--designed to shoot down slower, shorter-range missiles--could be upgraded quickly and cheaply to defend against longer-range intercontinental missiles. They envision ships sitting off the coast of rogue states and intercepting missiles when first launched, during the “boost“ phase (reasoning that missiles are slower, larger and hotter targets than after the warhead and decoys separate from the booster in later phases).

Yet the Navy theater defense system is being designed to intercept missiles in the mid-course phase. Intercepting missiles in the boost phase requires large, fast interceptors that can differentiate between the rocket plume and the missile. Such interceptors would probably not fit in the vertical launch tubes of Aegis ships and would require years of development. Even if the missile could be made to fit into the launch tubes, the Navy would require more of the $1 billion ships to perform new missions. Also, because Aegis ships do not have radar sufficient for missile defense, a network of infrared satellites for tracking missiles--which will not be deployed until at least 2010--would be needed. Thus, the claim of the proponents of sea-based systems that they could be deployed faster and more cheaply than the administration’s land-based system is questionable.

Furthermore, for a boost-phase intercept, the window of opportunity is so small that even a fast interceptor may not be able to catch up to a launched missile. Even if a chasing intercept is possible in the boost phase, any sea-based missile defense would get only one shot at a missile. In contrast, the Clinton administration’s land-based system, designed to intercept in the mid-course phase, would allow more than one shot.

Sea-based systems also raise operational questions: A ship off the coast of a rogue state must try to shoot down every launched missile because in that early flight stage the missile’s ultimate destination is unknown. Such a provocative action might be unnecessary if the missile launch were only a test or for scientific research. By contrast, a land-based system would shoot down only missiles definitely on the way to the United States.

Also, ship-based defenses must be close to the launch point of the missile and positioned near the missile’s trajectory. Thus, those defenses may not be able to intercept missiles on certain trajectories from the Middle East or North Korea--the primary regional threats that missile defense is supposed to counter. Additionally, a ship off the coast of a rogue state would be more vulnerable to attack than would U.S.-based radars and interceptors.

Although the land-based system carries technical risks, sea-based systems are being promoted primarily for political reasons (to preserve or destroy the ABM treaty or to defend allies). The risks of a land-based system, which can be minimized by thorough testing, are lower than those of the theoretical sea-based system. The Clinton administration is already pursuing the least expensive and most rapidly deployable system for defending the U.S. homeland against missile attack. Development of only that missile defense system should be continued by the next president.