Why `star wars' bothers the Russians

QUITE obviously, the Russians do not like President Reagan's ``star wars'' (Strategic Defense Initiative). They have for months now been maneuvering and propagandizing toward the end either of heading off or of delaying development and deployment of any of the various components of the project.

Why does it matter so much to them?

The answer lies in one great big difference between the Soviet and the American nuclear arsenals.

Not quite two-thirds of the nuclear warheads in the American long-range arsenal are mounted in the world's most silent submarines, capable of being launched at any time from places unknown to the Soviets.

Not quite two-thirds of the nuclear warheads in the Soviet long-range arsenal are mounted on land in fixed places, each one of which has been located by American satellite reconnaissance and each one of which is marked down as a target for an American warhead.

Add that the remaining portion of the Soviet long-range warhead arsenal is based on submarines that are seldom at sea and so noisy when they do go to sea that NATO detection devices pick them up when they head out into the oceans and are able to track them wherever they go.

The Soviets have about 60 submarines equipped to handle long-range nuclear weapons, but usually only about 13 are at sea at any time. The Russians have not developed high sea-keeping capability. The United States has 35 such submarines, with about 18 usually at sea at any time. The US Navy learned in World War II to go to sea and stay there, almost indefinitely. It still can, and does.

The actual figures on land-based vs. sea-based long-range nuclear warheads, taken from the latest annual report of the International Institute for Strategic Studies, is as follows: (See CHART above.)

Almost everyone, except Mr. Reagan himself, now recognizes that the prime purpose of star wars is ``the defense of America's capacity to retaliate.'' That is quoted from Assistant Secretary of Defense Richard Perle on June 3.

The Pentagon has long worried about its own land-based deterrent. The Soviets' land-based missiles have been gaining in accuracy. Their latest and best are believed to have achieved an accuracy rating of 200 meters (meaning that half of the warheads aimed at a given target would come within 200 meters, or 220 yards, of hitting it).

Since the Soviets could, in theory, throw 6,420 of their warheads at America's 2,118 land-based warheads, it would follow that they could have an excellent chance of knocking out most of the US land-based warheads. That is what worries the American nuclear strategists, and that is why they want some better way than they have now of protecting America's land-based deterrent.

But the other side of the coin is that success in making American land-based missiles secure would cancel out the strategic value of nearly two-thirds of the Soviet nuclear arsenal.

Suppose that star wars turns into a highly successful protection for many, not necessarily all, of the 1,018 silos that contain the missiles and warheads that make up the American land-based deterrent. If that happened when the Soviets had not yet developed an equivalent protection for their own land-based deterrent, the US would have an enormous advantage in nuclear power.

The Soviets have put nearly two-thirds of their nuclear strength into their land-based missiles. If star wars works, then that huge Soviet investment is neutralized. The Soviets' land-based deterrent is canceled out and their sea-based deterrent is worth little.

The men in Moscow in such an event would be talking among themselves about their own ``window of vulnerability.'' There has never been any real ``window of vulnerability'' for the US, because of those silent submarines on their undetected vigils under the seas. But there could be a disastrous (from the Soviet point of view) ``window of vulnerability'' from star wars.

It is hardly surprising under these circumstances that the men in Moscow want at the very least to slow star wars down so as to gain for themselves time either to catch up or to find out whether it does or does not work.