The National Science Foundation has been conducting an exercise that is providing a look at what American scientists and engineers are planning for the future. Outside of the agency, however, the effort is seen as something more political -- a promise of wonders to come if the NSF is expanded into something resembling a federal Department of Science and Technology.

Washington science-watchers are suggesting that the exercise foreshadows an attempt by NSF to assert hegemony over all government science except the medical sciences. (They would remain with the National Institutes of Health.)

The speculation began when NSF director Erich Bloch asked his division heads to come up with two five-year plans for guiding the growth of American science and engineering.

Under what was called Scenario 1, funding would grow at a steady 10 percent a year, yielding a real increase at the end of five years of 46 percent over current budgets. Under Scenario 2, funding would grow much faster, yielding a budget five times bigger than Scenario 1's after five years.

Scenario 2 was perceived by some in other federal science agencies as so grandiose and unrealistic in light of the budget deficit that they wondered if the NSF was trying to capture the territory of some other agencies. The idea of a Cabinet-level superagency for science has been around for decades.

There is language in several parts of the five-year plans that suggests taking over the facilities and responsibilities now entrusted to other agencies. Those mentioned most frequently are the Energy Department, which operates many of the large national laboratories, and the Commerce Department, which includes the National Bureau of Standards.

In what he called a "strategic planning statement," Bloch said that under Scenario 2, "NSF continues with the majority of its present activities, but in addition increasingly assumes a more prominent position in science policy and in the support of science and engineering research and education." Bloch also suggests that other countries will come to view the NSF as the "U.S. Ministry of Science."

Despite the language, NSF officials insist that the plans are strictly hypothetical, only an "intellectual exercise" intended to stimulate better thinking about the future of American science.

"Most of us are always constrained by the status quo -- trying to squeeze blood out of a stone," said Joseph F. Kull, NSF's chief of budget analysis. "This gave us a chance to break out and do some thinking of a more far-reaching nature."

"It was not off bounds to think about what other agencies are doing that we might share in, but that wasn't the intent of this," said Margaret Windus, executive secretary of the National Science Board, the policy-making body that guides NSF.

While any thoughts of massive budget increases or major mergers are probably only wishful thinking, some of the ideas offer a fascinating glimpse of where U.S. science and technology may be headed.

Nam Suh, the head of NSF's Directorate for Engineering, wrote in his Scenario 2 plan (the faster-growing budget) of a major new push to develop genetically engineered microbes that can break down contaminants in municipal sewage and industrial wastewater, along with new facilities that would use such organisms to treat water.

Under the more modest Scenario 1, Suh proposed creating a new Earthquake Engineering Center to study ways of making buldings, bridges and roads more damage-resistant.

Whatever the future budget realities, Suh warned that by the year 2000, today's underdeveloped countries will be more industrialized and competing more effectively for petroleum, scarce metals and other minerals. There is a need, he said, to develop alternative materials and fuels, recycling methods and energy conversion and conservation.

At the softer end of NSF's spectrum of scientific specialties, David Kingsbury, assistant director for biological, behavioral and social sciences, foresees an effort to link new ideas about how the human mind thinks with advances in logic, computers and information science. The goal would be to develop what he called "advanced intelligent information systems," or computers that think more like humans and humans that can reason more like computers. Kingsbury said such a goal would be possible only under Scenario 2.

PROMOTION . . . Richard F. Nicholson, a chemist who has served at NSF for 15 years, has been named assistant director in charge of the Division of Mathematical and Physical Sciences. Nicholson has been acting deputy director and staff director of NSF. He has won seven awards for administrative excellence, including, in 1982, the Presidential Distinguished Rank, the government's highest civil service honor.