Washington — Important questions are being raised about the arms control and economic implications of President Reagan's strategic defense initiative. Aside from whether the ''star wars'' program is technologically feasible - a very large question in itself - these other issues may determine whether the United States proceeds with space-based ballistic missile defenses.
Within the administration, there seem to be differences of opinion about whether any US gains in advanced missile defenses might be traded away for reductions in Soviet nuclear missiles.
Asked recently whether the US might demonstrate the technical feasibility of some aspect of ''star wars,'' then offer to not deploy it, in return for Soviet offensive reductions, chief US arms negotiator Edward L. Rowny said, ''That's certainly one option.''
''It opens up a whole new regime for leverage with negotiations,'' Lt. Gen. James Abrahamson, head of the strategic defense initiative (SDI) organization at the Pentagon, said in a recent Monitor interview. ''We may even do some trading. We might say, 'OK, we won't put something up for three years if you take out 500 warheads.' ''
Defense Secretary Caspar W. Weinberger, on the other hand, says the US should push for strategic defenses in any case.
''It's not a bargaining chip,'' he told the Monitor earlier this month. ''If we can get it, we would want to have it, and we're working very hard to get it. It's not a chimerical thing out there on the margins to try to influence them to make reductions in offensive systems.''
How vigorously the US pursues a revolutionary strategic defense system depends on Congress. Lawmakers recently trimmed the administration's $1.8 billion request for SDI in fiscal year 1985 by about $400 million.
The debate undoubtedly will grow louder and sharper next year, when spending for missile defenses is to rise sharply under administration plans. The figure is scheduled to nearly double for 1986 to $3.6 billion, then continue climbing steadily to $6.3 billion in 1989. This cumulative total for research and development only - before anything is deployed - is some $26 billion, a figure approximating what will be spent on full deployment of the MX missile or the B-1 bomber, two of the Pentagon's largest weapons programs.
Some critics now warn that - as has happened with the B-1 bomber - the SDI program may develop a built-in constitutency based on jobs and other regional economic benefits, which will overwhelm questions about military utility and nuclear stability. ''It will undoubtedly set off an arms race of a kind we've never seen before,'' said Herbert Scoville Jr., a former senior intelligence and arms control official.
Other critics add that R&D for space-based ballistic missile defenses may ''crowd out'' research and development in other parts of federal scientific spending, as well as the private sector, as happened with the Apollo space program.
In a report released over the weekend, the Council on Economic Priorities (CEP) examined the economic impact of the strategic defense initiative and concluded that ''Congress should significantly slow the SDI's funding growth rate unless and until a more complete analysis indicates that the goal is technologically and economically feasible.''
The private New York-based (and generally liberal) organization found that ''based on the general historical relationship between pre-full-scale development expenditures and total procurement cost,'' the cost of space-based missile defenses as envisioned by the President ''could range from $400 billion to $800 billion.''
Among other things, the CEP found that strategic defense will consume nearly 30 percent of all new R&D funding in the US next year, and about half of all growth in Defense Department R&D over the next five years. Between now and 1978, the report states, the Defense Department will absorb one-third of all new engineers in the US, about 12 percent of them for SDI.
The crowding out of research funding for other purposes may be offset by economic spinoffs in some areas, particularly high-speed computers. But it is unclear how great this will be, especially since so much of the work affects national security and is highly classified.
''The private utility of high-energy lasers, particle beams, large optics, and infrared sensors are not immediately obvious,'' states the CEP report. ''While the techniques developed for producing these systems may have broader applications, commercial benefits from the bulk of SDI research are at best speculative.''
''There is an economic price that has to be considered in deciding whether we should go ahead with this program or not,'' said Robert DeGrasse, director of the 125-page CEP study. ''Certainly there will be economic benefits. ... But our conclusion is that the President's accelerated program involves substantial economic costs.''