An SDI ‘Hamlet’ Without the Prince : THE CARDINAL OF THE KREMLIN<i> by Tom Clancy (G.P. Putnam’s Sons: $19.95; 543 pp.) </i>

If the Strategic Defense Initiative is so full of holes, then why are the Soviets so eager to stop it? Do they know something we don’t know?

This leading question was for a long while the best defense of SDI against its many scientific and political attackers. An answer to that leading question is the premise of Tom Clancy’s new novel.

Yes, the premise goes, the Soviets do indeed know something we don’t know. Bright Star, their version of Star Wars, has just been tested in the field, and the damn thing works. The test took place when a laser beam from a secret installation at Dushanbe in the Tadzhik S.S.R. near the Afghan border scored a direct hit on an orbiting satellite.

In Moscow, Bright Star’s backers are using the field test to urge a go-for-broke development program: “Comrade Minister, I have been a professional soldier for 20 years. I have served on battalion and divisional staffs, and I have seen close combat. Always I have served the Red Army, only the Red Army. Bright Star belongs to another service branch. Despite this, I tell you that if necessary we should deny funds for tanks, and ships, and airplanes in order to bring Bright Star to completion.”

Fortunately for the good guys, one Moscow insider who has seen the key report is secretly working for the Americans. Unfortunately for the good guys, Misha Filitov’s cover has just been blown, and so it is up to Jack Ryan, Clancy’s hero in earlier novels, to get Filitov, code-named “Cardinal,” out of the Soviet Union for the debriefings that will close the laser gap. It takes several hundred pages, but he succeeds.

In “The Cardinal of the Kremlin,” Clancy is surprisingly good at what he has previously been poor at, and unavoidably poor at what he has previously been good at. Characterization and dialogue were wooden in his earlier books. Here they are often convincing. On the other hand, his forte in “The Hunt for Red October” and “Red Storm Rising” was mastery of the technological and administrative systems of superpower war making. Those systems--submarine and tank warfare--were there in their maturity for anyone with the brains and energy to master them. Clancy mastered them, made them the true protagonists in his books and turned millions of Americans into enthralled students in his classroom.

He does nothing of the sort this time out, and no one could: Star Wars, Bright Star--these “systems” have not yet reached even their infancy. In the memorable phrase of Roy Woodruff, former head of nuclear weapons development at Lawrence Livermore National Laboratory, they are “notional weapons.” And so, in place of the stunningly detailed descriptions in “Red October” of, for example, a meltdown in the reactor of a nuclear submarine, we have sentences like the following from a U.S expert telling the President how the Russians did it: “As you draw energy into the laser beam, the electrons become less energetic, okay? That means you have to taper the magnetic field that contains them--and remember that at the same time you have to continue the wiggling action of the field, too. We haven’t figured that out yet. Probably they have, and that probably came from their research into fusion power. . . . They’re ahead of us because they’ve spent more time and money in the most important place.” “The Hunt for Red October” has been credited in some quarters with building support for the naval budget. This time, Clancy has built the SDI research budget into his plot. Unfortunately, research and budgets are less exciting in fiction than tanks and submarines.

To some extent, “The Cardinal of the Kremlin” has also been overtaken by political events that occurred during its writing. Thus, we read: “Things were going well for the mudjaheddin. There was talk that the Russians might actually withdraw.” Or again: “The Soviets had hinted at reneging on the verification section of the proposal that had already been settled in principle, hoping this would shake the Americans loose, even a little, on the SDI question.”

The principal objection to the premise of the book--a Soviet SDI breakthrough--is, of course, that the Soviet Union lags far behind in the indispensable computer technology. But the principal objection against the SDI itself, the objection that won’t go away, is that technically ingenious and (above all) cheap countermeasures exist to foil it. Of these, Clancy says nothing. And the silence is regrettable. His book would have been more exciting had there been a real hi-tech war at the heart of it: our SDI versus their counter-SDI. But to write such a book Clancy would have to do more than follow the research, he would have to lead it.

Instead, the most he can give his readers this time out is a conventional hunter-and-hunted spy novel, well enough told but without the patented Clancy excitement of a real-life video game. Ten years from now, if the SDI system has been built and if the Soviet countersystem is also in place, then Clancy may be able to give us another of the weapons-system novels that, clearly, he was born to write. In the meantime, “The Cardinal of the Kremlin” belongs not with spy fiction but with science fiction. It is, in other words, not a book about actual weapons in imaginary hands but a book about imaginary weapons.