A minor snag popped up in the first two flight tests of the proposed antimissile defense system. The weapon that will save the world can’t tell the difference between an incoming nuclear warhead and a medium-sized striped balloon. The Pentagon’s remedy is ingenious, at once both obvious and cunning. Keep the balloon, lose the stripes.

This would seem a small thing if it weren’t for this — in the electronic eyes (infrared sensors) of the Exoatmospheric Kill Vehicle (EKVs are the 120-pound homing devices that will intercept and destroy hostile nukes in, presumably, the exoatmosphere), medium-sized striped balloons are dead ringers for warheads.

It has to do with decoys. One of the toughest challenges facing the antimissile system is distinguishing between the actual warhead and the dozens, even hundreds, of decoys that an enemy would pack aboard the same missile. The twinkling light and faint, fluctuating heat emissions reflected from that medium-sized striped balloon so closely resembled the twinkling of a tumbling warhead that it stumped the EKV. So did the reflections from inflatable warhead replicas. The EKV was, however, able to distinguish between the emission of a warhead and of a large striped balloon six or more times brighter or of a small unstriped balloon only one-third as bright.

With two flight tests done and 14 to go, at a cost of $1.6 billion, and with the decision on whether to build the whole $60-billion enchilada hanging in the balance, one might assume that the Pentagon would refine the technology and measure its success with tests of ever-increasing difficulty.

Yet according to a leaked copy of the Pentagon’s testing plan, the tests actually get easier. Future tests won’t include those troublesome medium-sized striped balloons and inflatable warhead replicas. From now until actual deployment in 2005 (if all goes well), it’s nothing but balloons six times brighter or one-third as bright. (Brightness is the appropriately key factor in this dumbing down of antimissile systems tests.) If EKV still has trouble, they’ll no doubt add in some of those cartoon-character balloons from the Macy Thanksgiving parade.

This revised testing plan was leaked to and analyzed by Dr. Theodore Postol, MIT professor and former top Navy science advisor in the Reagan Administration. This is the same Dr. Postol who challenged the military’s exaggerated claims of success for the Patriot missiles in the Gulf War. The Pentagon at first denied his assertion that Patriots shot down no Iraqi missiles, then conceded he was correct.

Now, the Pentagon concedes that the antimissile test plan has been altered, but vigorously denies Dr. Postol’s assertion that it has been made so easy that even the most indolent and inattentive EKV could pass. The Pentagon says the testing actually gets more difficult. Lt. Gen. Ronald Kadish, director of the antimissile program, said those who say the testing does not get more difficult with decoys that increasingly do not resemble warheads make “a valid techical argument.” He cleared up any confusion that statement caused by adding that simply because a decoy seemed effective “doesn’t mean it’s credible.”

By that second statement, the general seems to imply that a nation, even a “rogue” nation like North Korea or Iraq, that could build and launch an intercontinental ballistic missile might find the manufacture of medium-sized striped balloons beyond its technological powers. By the first, he seems to be conceeding that, with luck and $60 billion, the United States just might end up with an antimissile system that can tell the difference between an incoming nuclear warhead and Snoopy hovering over Manhattan.