For several years, regular as clockwork, Capitol Hill's annual fight to cut the budget has spawned alarms that the proposed space station, Freedom, is about to be murdered by Congress. These reports have always proved to be exaggerated.

This season, some of the manned space program's staunchest advocates have changed sides, in a sense, and are suggesting that a mercy killing might be in order. A variety of experts inside and outside of NASA have warned that the space station project is beset by technical and management problems, confused purposes and soaring costs.

In order to save Freedom, they are urging NASA to step aggressively back to the drawing board for yet another major reassessment of the 300-ton orbital laboratory, with a view to reducing its size and complexity, and sharpening its focus. Prospective budget cuts and the Bush administration's interest in exploring Mars, they say, provide the perfect excuse.

William P. Lenoir, who heads NASA's office of space flight, told a House subcommittee last week that the agency will have to rethink the station in any case if the project's 1991 budget is cut to the level set by the Senate. But maneuvers are underway to provide the project with enough money to keep it on its present track.

NASA and contractor engineers are working on ways to simplify the design, officials said, possibly by shortening its 500-foot support structure, for instance. But top NASA managers insist they are committed to the existing design in its general form.

"It's rather frustrating," Lenoir said in an interview. In discussions with critics, "I can refute their concerns on a factual basis. But it doesn't seem to allay the ill feeling or the malaise about the viability of the space station. I don't know how to cope with that."

The country can't "step back 10 years and start over with a fresh piece of paper," he said. "If we could, I might organize it differently . . . but I'm convinced {the basic design} wouldn't look a lot different."

Even the critics acknowledge that any cure, at this point, could well be as painful, and expensive, as the current program. "This issue is dynamite," said one aerospace industry expert.

U.S. prestige and NASA's credibility are at stake, not to mention tens of billions of dollars over coming decades. The European Space Agency, the Japanese and the Canadians, who are to pay 20 percent of the costs, have signed agreements and invested millions in the project, which has already gone through five redesigns or reviews and six top managers since it was approved by President Ronald Reagan in 1983.

"It is generally believed . . . that the U.S. will not be welcomed in future international space ventures if we back out of our space station agreements" with other nations, according to a critic of the station design. "Domestically, terminating long-term contracts with an aerospace industry already in decline would be economically and politically damaging."

NASA officials are said to be keenly sensitive to the need to include all these players, as well as Congress, in discussions of major changes.

Delays due to lack of funding, as well as technical concerns, have driven estimates of the space station's total cost from $16 billion to almost $40 billion by the time it is to be completed late in this decade.

The space station project is nearing a critical phase in which, late this year, its design details are to be locked into place in preparation for the first actual cutting of metal.

The project's new managers have spent the summer wrestling with serious problems -- excessive weight and impossible workloads for space-walking astronauts, for example -- attributed by many to a loss of management control over the project in the late 1980s.

"We have come a long way toward a complete solution of all those issues," Lenoir said.

The main point of agreement among critics and station supporters alike is concern about the project's sole reliance on the unexpectedly fragile space shuttle fleet to build it and maintain it in orbit. That concern has been aggravated by NASA's inability to launch a shuttle since April because of hydrogen leaks.

"The general consensus here was that we needed to examine options which reduced the heavy dependence on {shuttle} capability," engineer and former astronaut Owen Garriott of Teledyne Brown Engineering said at a workshop last month on alternatives to the space station design.

Basing the station's deployment and operation "on the space shuttle alone is of considerable concern," said John Fabian, another engineer and former astronaut, now with the Anser Corp. Among the alternatives discussed, he said, were development of large new American unmanned vehicles and the use of the Soviet Energia booster.

Fabian pointed out that while the development of any new vehicle would be costly, continued reliance on the shuttle could prove equally costly.

"This is still our Achilles' heel," J.R. Thompson, NASA's deputy administrator, acknowledged in an interview.

Over their 10-year lifetime, he noted, the shuttles have made a total of 35 flights, for an average of 3.5 flights per year. "That's incompatible with NASA's mission in the 1990s . . . . Over the next decade, we've got to launch 120." The current space station design would require about 28 flights for assembly.

It has been two years and 10 missions since the shuttles began flying again after management and design overhauls of their own because of the 1986 Challenger disaster. A fourth orbiter is almost completed.

"NASA must either fix its problems of management, inspections and quality control" and fly the shuttle three times as often, Thompson said, or "stop dreaming" and reduce its mission accordingly.

Another reason to rethink the space station, some critics say, is that national goals have changed since the space station was designed. President Bush and his top lieutenants have made a political commitment to the exploration of Mars.

Congress, however, has refused to fund the Mars initiative on grounds that "if NASA is having so much trouble with the space station, don't bother requesting support for things beyond that," said planetary scientist Bruce Murray of the California Institute of Technology, vice president of the Planetary Society, at the Sept. 21 workshop.

The workshop, hosted by the Planetary Society, presented a number of options but avoided making formal recommendations.The options included a major restructuring of the space station, perhaps building it in stages as the Soviets have done; or breaking up the station's functions and dividing them among the shuttle and the Soviet Mir space station.

The space station/shuttle system "encompasses almost all that has gone wrong with the U.S. space program over the past two decades," space policy analyst John Logsdon of George Washington University said. But with the administration's new long-range goals, "We have been given a really unprecedented opportunity to set things right."