MX commission study

President Reagan's special commission on the MX missile (whether and what kind to build) today delivers its report, which goes well beyond the original assignment.

The question put to a select committee of 11 bipartisan experts and political leaders was whether to build and how to base the highly controversial MX missile or, if not, what to build in its place to balance the presumed superiority of Moscow in ''first strike capability.''

When the panel members first sat down together to dig into the problem, they decided that it needed more time. They were supposed to report back to the President by March 1. They then decided that what was really needed most was not just a workable model (method of basing) for the MX, but a whole new approach to the problem of limiting, if possible, nuclear weapons.

Back when SALT I was launched during the Nixon administration, the United States enjoyed a world monopoly on the technology of mounting more than one targetable warhead on a ballistic missile. As a result, the US went in for limits on the number of launchers or vehicles, but not on warheads. It was assumed that the US could keep ahead of the Soviets in the technology of the warheads.

As a result, the US today has fewer launchers than the Soviets, but more warheads.

Meanwhile, the Soviets have caught up in the technology of the warheads and presumably will soon be up to or even ahead in numbers of warheads.

In other words, the assumption under the US position in negotiating both the SALT I and SALT II agreements has run out. The Soviets can build just as many independently targetable warheads as can the US. They can put even more warheads on a given vehicle because they have gone in for bigger vehicles. The Soviet's accuracy rating is not yet quite up to the American's, but getting close.

At present the Institute for Strategic Studies, a recognized world authority in such matters, rates the latest US nuclear weapons as being able to come within 22 meters of the target, half of the time. The best Soviet rating is within 400 meters of the target, half the time. But Soviet accuracy has been advancing and may be better than 400 meters now.

The commission, headed by General Brent Scowcroft, National Security Council adviser to President Gerald R. Ford, concluded from the above that there is no longer much point in thinking in terms of the present SALT II context. What is needed, if there is to be any meaningful arms control in the future, is a new context.

The main thrust of the commission's report, therefore, is that the MX in any form is only an interim matter. The real need is for a new context in which the US should seek an agreement with the Soviets, based on limiting warheads rather than launchers.

The commission does propose that the US build 100 of the big MX missiles as a temporary measure. They would be housed in existing Minuteman silos, as proposed by the Reagan administration after the ''dense pack'' idea was brought down in Congress on the grounds of implausibility.

But the commission also recommends immediate research and development aimed at perfecting a new, smaller and mobile launcher to carry a single warhead. It would be called armadillo. The commission hopes that the US government then would seek new negotiations with the Soviets. The purpose would be to get away from the old SALT concept which presumed US superiority in warheads, giving the US an advantage over Soviet superiority in numbers of launchers.

The new concept would be aimed at equality in numbers of weights of warheads, each to be mounted singly on its own vehicle. Since these new launchers would be small and mobile, so the argument goes, both the US and Soviets would escape from the so-called ''first-strike danger.'' Mobility supposedly gives invulnerability. A ground-based, mobile launcher would be even safer from attack than a missile mounted in a moving submarine, say experts.

The commission report included input from former Secretary of the Air Force Thomas Reed, former director of the CIA Richard Helms, former Texas Gov. William Clements, former NATO commander and Secretary of State Alexander M. Haig, former New Jersey Sen. Nicholas Brady, and former Defense Secretary Harold Brown.

The commission took testimony from scores of experts in foreign and defense policy. Among them was former Secretary of State Henry A. Kissinger, who wrote the original SALT agreements. In a recent magazine article, Dr. Kissinger stated that the original idea of going for MIRVs was a mistake. He said at the time it seemed like a good idea to build weapons which would give the US a new monopoly.

The ''new monopoly'' ran out years ago. As many predicted at the time, the Soviets caught up in the new technology. Hence, the commission concludes, MX at best represents the tail end of an unfortunate and regrettable chapter in US arms thinking.

The text of the report does not spell out the long-term purpose in quite the detail stated in this report. This report is based on additional detail and appraisal given to the writer by a member of the commission.