Seven or More Layers of Space Arms Favored

WASHINGTON —  Scientists and Pentagon officials, completing the second phase of research and design work on what has come to be called the “Star Wars” anti-missile system, are leaning toward a network of seven or more layers of defensive weapons intended to intercept Soviet warheads before they strike the United States.

And, experts say, there are indications that greater emphasis is being placed on ground-based weapons systems, which could be just as exotic as weapons floating permanently in space and perhaps even more complex but are likely to be less expensive to maintain and repair.

Continuing Scrutiny

The accelerated program, which took on a high profile after President Reagan’s March, 1983, speech shifting the United States’ overall strategic emphasis toward an undeveloped network of defensive weapons, faces continuing scrutiny--and a certain degree of skepticism--in Congress. Reagan’s $3.7-billion funding request for the “Star Wars” program in the current fiscal year has been trimmed by about $1 billion.

In addition, the Strategic Defense Initiative program, as it is formally known, is proving to be an increasing irritant in U.S.-Soviet relations. This has become particularly so in the period leading up to the summit conference that Reagan and Soviet leader Mikhail S. Gorbachev plan to hold Nov. 19 and 20 in Geneva.

In the current round of arms control talks, the Soviets are probing for ways to halt the program or limit the system’s deployment if it is developed. However, Administration officials, under Reagan’s guidance, are refusing to let strategic defense become an arms control bargaining chip.

Lt. Gen. James A. Abrahamson, director of the Strategic Defense Initiative Office, said in a telephone interview Sunday that “it is very clear that the right concept is a multilayered concept.”

Previous Research

Previous research has pointed up the need for a system intended to intercept attacking missiles and their warheads in at least four phases: the relatively brief boost and post-boost phases occurring upon launch and during the climbing period just after launch; the mid-course phase, as the warheads--and the decoys intended to draw the fire of defending weapons--coast through space; and the terminal phase, when the warheads penetrate the atmosphere over their targets.

But, Abrahamson said, “in some cases, you may divide the mid-course into several layers, and divide the terminal layers” too.

“You could go up to seven; you could go beyond that,” he said.

Different Weapons

Each layer would require different weapons, employing a variety of technologies and basing systems. Abrahamson said that, if a certain percentage of missiles and warheads could be destroyed at each layer, Soviet missile targeters would face uncertainties about striking specific targets and achieving their military objectives. Thus, he argued, each layer would strip away more confidence that an enemy could have that an attack could succeed.

Ground-Based Lasers

The director of the missile defense program said that extremely powerful ground-based lasers, bouncing their beams off giant, orbiting mirrors, are “attractive to us.” The laser beams, moving through the atmosphere and space at the speed of light, would be intended to destroy the attacking weapons.

Less attractive, at the current stage of research, he said, is a shotgun-like system in which pellets or an aerosol-like gas cloud would be shot into the path of the incoming warheads to destroy them on impact and, in the case of the gas, to slow down balloon-like decoys and separate them from the warheads.

“That concept has been looked at,” Abrahamson said. “It’s not the best.”

Goal Questioned

Hugh DeWitt, a physicist on the staff of the Lawrence Livermore National Laboratory, questioned whether it is possible to attain a goal of letting only 20% of the attacking missiles pass through each layer--a figure used by physicists working on the program, non-government experts said.

“I’ve never thought very highly of this. If you can get 80% with each layer . . . this is fine arithmetic on paper. In practice, I’m very doubtful,” DeWitt said.

Abrahamson’s disclosure that more than seven layers could be involved indicates that “the number of layers required keeps on going up,” said John Pike, associate director for space policy of the Federation of American Scientists, an organization that has frequently questioned the feasibility of developing certain advanced weapons.

“I think it is a recognition that each individual layer is going to be a lot leakier than they originally hoped,” Pike said. “They’re talking about putting more layers of shingles on the roof.”

Pike also said he has seen indications that “Star Wars” planners are leaning increasingly toward ground-based systems, rather than systems in which lasers and rockets would be launched into space to be aimed and fired upon the launch of enemy weapons.

‘Dollars to Doughnuts’

“I’ll bet you dollars to doughnuts that, at the end of Reagan’s term, it will be all on the ground. They won’t have anything in space because of the survivability problem” posed by the need to maintain and defend floating, highly sensitive weapons systems, he said.

Abrahamson said that, if weapons are based on orbiting satellites, “it is not clear how many and what kind are useful.” Some systems involve “kinetic kill” weapons--”rockets in the sky” that would be intended to destroy warheads by colliding with them in space.

One satellite with many rockets would lower costs but increase vulnerability; multiple satellites with fewer rockets would be more expensive but offer greater chances of survivability.

A proposed ground-based system would attempt to employ interceptor rockets and laser beams after existing, orbiting satellites flash initial reports of an enemy missile launching within moments after it occurs.