Some questions about the $100 billion (or so) 'star wars' defense

IT was a relief when the Challenger finally hooked onto Solar Max and plucked the ailing satellite into its cargo bay, proving that a shuttle could make service calls in space. But after our long, cosmic ''Whew!'' what can we earthlings, 300 miles below, learn from the failure of the first attempt to retrieve Solar Max, and indeed from the other small failures that have dotted the space program's record of general success?

One could begin with Solar Max itself, launched in 1980 to monitor solar flares and sunspots. Four out of seven monitoring instruments became inoperative after the satellite blew fuses.

When George D. (Pinky) Nelson space-walked out to latch onto the defective Solar Max, a second failure occurred - the jaws on the T-pad, the astronaut's docking device, refused to close.

On the previous shuttle mission in February, tiny flaws in the booster rocket nozzles caused two communications satellites to wander far off course.

In December, on the mission before that, bits of solder lodged in two computers, resulting in their breakdown.

At the present time, the $120 million satellite Landsat-4 has lost more than half its power because of cracked coating on its wires.

A blown fuse here. A spot of solder there. A cracked coating on the wires. A set of jaws that won't clamp. The impatient phrase for these minor vexations is ''glitches.''

To see the soaring glory of a space flight falter for such casual causes makes one think of the line, ''For want of a nail the shoe is lost, for want of a shoe the horse is lost, for want of a horse the rider is lost'' - leading to the anguished cry of Richard III on the battlefield of Bosworth: ''My kingdom for a horse!''

History hangs by linchpins. Which brings us to other kingdoms, other battlefields.

In the vast cold space where shuttles now fly, with some blown fuses, some errant blobs of solder - some glitches - the Reagan administration plans to orbit a ''total ballistic missile defense'' system, otherwise known as ''star wars.'' The plan is speculative - a war game, or rather the blueprint for a war game. Yet Secretary of Defense Caspar Weinberger has promised that ''star wars'' will constitute a ''thoroughly reliable and total defense.'' No glitches. No lost nails. Every last one of the 9,000 Soviet nuclear warheads could be intercepted, according to the ''star wars'' scenario, during the first phase of flight.

The Union of Concerned Scientists has doubts. That organization - including professors of physics from MIT and Cornell and former CIA analysts, among others - lists the articles of faith behind the laser interceptors of ''star wars'': ''Targets can be found instantly''; ''aiming is perfect''; ''software is never in error''; mirrors focusing the laser beams are ''optically perfect.''

The Union of Concerned Scientists sums up the projected hundreds of billions of dollars worth of ''star wars'' technology thus: ''A defense of stupefying complexity, under the total control of a computer program whose proportions defy description and whose performance will remain a deep mystery until the tragic moment when it would be called into action.''

Like any human organization floating in space on planet Earth, the Union of Concerned Scientists is not without its tilt - its own bias. But, thinking perhaps of a blown $2 fuse and the frozen jaws of a T-pad, they remind us of the obvious - that no system is, in Mr. Weinberger's too-confident phrase, ''thoroughly reliable.'' And the bigger the system and the more it is relied upon, the more devastating will be its breakdown when a glitch occurs.

The philosopher George Santayana coined the phrase ''wars of the imagination'' to suggest the ''passionately biased picture of advantages'' an adversary dreams of accruing from killing his enemy. But now the very act of killing has become a matter of the imagination too - employing weapons whose properties also remain a fantasy since they can never be tested.

In this ultimate ''war of the imagination'' the Earth, and its man-made satellites, lie on the gambling table for a single roll of the dice. And all we can be sure of is that somehow the dice will have a nick or a rounded edge. The dice will have glitches.

In the ancient tradition of warfare, should we try once again to perfect the dice - maybe under the name of ''Star Wars II''? Or should we try, at last, to find an alternative to gambling now that the stakes have become all or nothing?

As an alternative, a ''peace of the imagination'' would be a novel mission well worth its glitches.