The avalanche of American nuclear weapons

YOU have by now heard a lot about ``star wars'' and must have some sort of an idea of what it is all about. But have you heard of D-5? You should know about D-5 because it is just as important, perhaps more important, a factor behind the arms control debate and the present and prospective balance of power between the United States and the Soviet Union. D-5 is the designation of the new US missile being readied for the new Trident submarines. The Tridents now on duty with the US Navy are armed with a missile called C-4. The C-4 has a range of about 6,000 miles and a CEP rating of 450 meters (495 yards).

The CEP (circular error probable) rating means that if, for example, 10 American C-4 warheads are aimed at a particular enemy target, half will land within 450 meters, or roughly a quarter of a mile from that target. That is getting close for nuclear warheads. The closer a nuclear weapon gets to its target the greater the damage.

The CEP rating for the prospective D-5 is not officially stated, but it is expected in informed quarters to be well under 200 meters, which would mean it was better than anything now deployed by either the US or the Soviet Union in the long-range nuclear category.

The D-5 is a big improvement over the C-4, because of its targeting technology. All existing American submarine missiles are targeted on navigational calculations. Since a submarine is in constant motion at sea, its exact position is difficult to determine. With all modern methods there is still some margin for error, because of such variables as ocean currents.

But the D-5 does not depend on navigational calculations. It is targeted from the stars. It can adjust its trajectory in flight from a fix on some particular star. It will, at least in theory, be just as accurate as any fixed land-based intercontinental missile. It will be a long step forward in US strategic nuclear power.

The D-5 is supposed to be ready for deployment three years from now, or much sooner than anything to be expected from star wars. The enthusiasts for star wars talk of having parts of the system ready in perhaps 10 years. Critics think 20 is more likely.

We know from the fuss the Russians have been making that they are unhappy about star wars, even though it will probably be at least 10 years before we, and they, will know whether it works. But perhaps the fuss they make over star wars is because it must seem to them like the ultimate piece of bad news on top of a lengthening list of things the US is doing which give them cause for concern.

The new MX missile is not yet deployed, but it's on its way. The MX is supposedly more survivable than the existing Minuteman missiles. The US Air Force is working ahead on the ``stealth'' bomber, a plane designed to be virtually invisible to enemy radar, hence able to approach its target without being detected or attacked.

The new American cruise missiles are already deployed by aircraft in the European theater. There will be a sea-based version. The US cruise missile has a range of 2,000 miles beyond the range of its carrier. It can be launched from a B-52 bomber, which has a range of over 12,000 miles, or from seagoing vessels.

We in the West do not know what the Soviets have on their drawing boards. But satellite reconnaissance gives us a fairly good idea of what they have in development. The best available information is that in all these categories of new weapons the US is well in the lead. The Russians have cruise missiles, but with only about half the range of American cruise missiles, and not with an equivalent targeting system. The latest US cruise missile has a possible CEP rating as low as 20 meters.

There is no evidence that the Russians have a stealth-type bomber coming, or anything as accurate as D-5 will be.

From Moscow they can see looming up over them in the future the MX, stealth bombers, cruise missiles, the D-5 -- and, over the horizon, star wars. Their technology may be good, but it isn't enough to produce anything like this prospective avalanche of new US nuclear weapons capable of smashing their land-based missile silos on which they have pinned their reliance, with star wars denying them retaliation.

It is not surprising that Mr. Gorbachev sounds like a man who wants to talk.