The 99% fallacy.

• Author: Evans, David
• Position: Strategic Defense Initiative

THE 99% FALLACY

Will the Star Wars defense against Russian ballistic missiles work? Secretary of Defense Caspar Weinberger has announced the goal of deploying a "99 percent effective' system by the mid-1990s. But this laudable hope is unrealistic, for the simple reason that none of our existing complex military systems come anywhere close to this standard for reliability and lethality.

Consider a few examples, going up the scale from relatively simple to extremely high technology:

None of the Army's existing inventory of anti-tank missiles is 99 percent effective. In various practice shoots, the TOW missile has hit its targets anywhere from 80 to 90 percent of the time--stationary targets, not tanks maneuvering at 20 miles per hour. And even these results were obtained only under benign, near-laboratory firing conditions.

Not one of our fleets of high-performance tactical jets meets its stated "full mission-capable' goal, that is, the percentage of aircraft with all systems "full up' and ready to fly. After massive infusions of spare parts, and the careful ministerings of hundreds of flight technicians, our jets have higher "mission capable' rates than they did four years ago. But they still don't meet the Pentagon's reliablity goals, which are not nearly as demanding as 99 percent.

Defending our Navy carrier battle groups is a much less challenging task than fending off waves of Soviet ballistic missiles. Yet we have never achieved a 99 percent effective defense for our patrolling ships. The Navy relies on a combination of three defensive "layers'--F-14 fighters, AEGIS missile cruisers, and close-in rapid-fire cannon--each of which is thought to provide an 80 percent effective shield against air or sea attack. On the drawing boards at the Pentagon, the Navy calculates that the carrier group defenses achieve an overall theoretical effectiveness of 99 percent. But in their honest moments, off the official record, many naval officers concede that their mathematical figuring does not translate into invincible ships. These officers have commented to me that in battle the individual defensive layers would be ineffective, especially if subjected to saturation attack.

Moreover, this is all military hardware with a "man in the loop,' enjoying almost daily maintenance and frequent field exercises to validate its performance. We have a reverse situation with Star Wars, which would consist of highly complex, unmanned armed satellites, floating for...