The Reagan campaign pledge to unleash military science spells new difficulties for American manufacturers who are being walloped by foreign high-technology products.

The reason is that defense -- which now takes more than half of all federal spending on research and development -- is already hogging the market for scarce computer scientists and other technical specialists. Military projects, with ample payrolls and professionally challenging goals, have regularly skimmed so much talent from the nation's technical work force that some of our leading technocrats have warned of an ensuing anemia on civilian areas.

Among them, for example, is National Academy of Sciences President Philip Handler, who, though a Sakharov-supporting hard-liner on Soviet-American relations, has several times publicly expressed concern about the domestic impact of high military research spending. Newly added to the long-existing talent stretch is the fledgling synfuels industry; as it joins the scramble for many of the same people sought by defense and consumer industries, the pickings become increasingly poor for firms that compete with West German and Japanese goods. Even when supply and demand are in balance -- as is the case in many fields -- it's the military that draws off the heavy hitters of research.

The demand for engineers is so strong that almost all job-seekers in last spring's record-size graduating class were employed by mid-summer -- with starting pay generally over $20,000 a year, according to the Engineering Manpower Commission. Unemployment among engineers is down to 1 or 2 percent. And industrial job opportunities are so rewarding and diverse that faculty slots at scores of major engineering schools are vacant.

Meanwhile, though engineering grows more complex, American students are increasingly shunning graduate study in engineering in favor of lucrative jobs for bachelor-degree holders. Of 3,800 engineering doctorates awarded last year in the United States, half went to foreign students, many from developing countries that are pursuing industrial leap-frog strategies in aiming for high-technology export markets. India and South Korea, for example, now export many sophisticated products of domestic design and manufacture.

In response to Germany's and Japan's parsimonious involvement in military research, it's traditionally been argued here that military discoveries and applications have done double duty for this country by enhancing national security and invigorating industry. The spinoff thesis is accorded some validity by Simon Ramo, a retired electronics industrialist who is one of Reagan's senior science advisors.

But in a newly published book, "America's Technology Slip," Ramo -- a longtime veteran of Washington's high-technology councils -- also invites recognition of the economic toll exacted by military research. "Probably our relative productivity increases and our net rating in technology vis-a-vis other nations," Ramo states, "have on the whole been hurt rather than helped by our heavier involvement in military technology as compared with other nations."

And he adds: "In the past 30 years, had the total dollars we spent on military R&D have been expended instead in those areas of science and technology promising the most economic progress, we probably would be today where we are going to find ourselves arriving technologically in the year 2000. . . . The employment of a large fraction of the best scientists and engineers on military projects means they are not available to advance the store of knowledge and innovate along non-military lines. Our disproportionate share of the military weapons requirements of the non-communist world has accordingly handicapped us by comparison with our industrialized allies."

Ramo's observations are complemented by a recent report by one of Britain's leading scholars of industrial innovation, Keith Pavitt, of the Science Policy Research Unit at the University of Sussex. "Defense programs," he states, "creates habits, skills and attitudes in research and development, production and marketing that are sometimes positively harmful when competing on civilian markets; and unsuccessful competition on civilian markets reinforces the incentive to concentrate on defense markets."

"Such a vicious circle has been observable in the U.K. in such diverse sectors as aircraft, heavey engineering, electronics and shipbuilding," Pavitt observes. And he goes on to ask whether the same process may affect the United States, "given the divergence of the requirements of civilian and military markets."

In the wake of Voyager's billion-mile bull's-eye, it's easy to believe that American science and technology are omnipotent. They are strong and versatile, but not so much so that we can open wide the throttle on military research without doing serious harm to the civilian economy.