The Reagan administration is coming under increasing attack for what critics say is its failure to decide on an affordable long-term policy to ensure the nation's continued preeminence in space.

While the grounded space program struggles to return to flight in the aftermath of last year's Challenger disaster, members of Congress, scientists, managers and other space experts complain with new urgency that the White House has failed to give the program adequate support and that NASA Administrator James C. Fletcher and other top agency officials called in to guide the recovery have not provided vigorous leadership.

Space policy is mired in a swamp of committees, reviews and interagency battles, they say, while the Soviets and other nations are moving forward with many of the options still being studied here.

Some space advocates had hoped that an 11-month study directed by astronaut Sally K. Ride would serve as a galvanizing blueprint for the space program. But NASA officials now are billing the Ride report, scheduled for release this week, as an "interim" report that will provide the basis for further study.

Criticism of the space program's leadership has come from a variety of sources in recent weeks:

Using uncharacteristically strong language, editor Donald E. Fink wrote in the July 27 trade magazine Aviation Week and Space Technology that "the U.S. space program, most notably the NASA portion, is foundering under the worst management crisis" in its history. The White House has provided "little guidance, direction or support," Fink said, and Fletcher has failed to "lead NASA or surround himself with a vigorous upper-level management team that can."

Reginald Turnill, editor of the British space and defense publication Jane's Spaceflight Directory, declared that NASA is in thrall to bureaucrats concerned mainly with safety and has "lost the will to fly men in space."

Ride told a congressional panel that even the modest dates being considered for going to the moon or Mars are jeopardized by the administration's failure to support basic research to develop the necessary technology. "We need to be starting the technology development at a serious pace, within the next year or two," or it will be well beyond the year 2000 before the U.S. can send astronauts to either destination, she said.

Members of Congress and others have complained that the administration has made no response to the recommendations of the congressionally mandated National Commission on Space, first submitted early last year, shortly after the Challenger disaster, and resubmitted by commission head Dr. Thomas O. Paine last March to White House chief of staff Howard H. Baker Jr. Many were looking to Ride's report to provide an official response to the commission recommendations.

Decisions over a period of nearly two decades, punctuated catastrophically by Challenger and a series of other rocket accidents, have left the U.S. space program in a difficult position.

Most of the rocket fleet is grounded and new vehicles on order are months or years away from flight. The military has had to rely on old satellites for electronic surveillance and other national security functions. The shuttles will not fly again before at least mid-1988, and when they do, their flight schedule and carrying capacity will be curtailed because of increased safety measures. The space sciences have withered under a decade of neglect. And money is scarce even for projects already under way, such as the space station.

Underlying all the problems, according to many, has been the lack of a long-term strategy that builds methodically toward a goal or series of goals.

The available options have changed little over the decades. To set priorities, most experts say, will require a president who will make the tough choices and stand behind them. Below Reagan, they say, is a perpetual flux of bureaucratic infighting.

Some insiders say Fletcher is intimidated by the Office of Management and Budget, which has the space agency on such a tight leash that it reviews in advance planned speeches by NASA officials to make sure they don't advocate anything that requires more money.

Fletcher acknowledges that he lacks charisma and has made some errors, but points to varied signs of progress at NASA in the 14 months since he took the top post. He also held the job from 1971 to 1977, and those who know him well, including some admirers, say he is predictably exhibiting the same strengths and weaknesses as during his first stint.

Shirley Green, a spokesman for Fletcher, described as "naive" some of the critics who complain that Fletcher has failed to stand up to others in the administration. It is, Green said, "as if they expect the leader of an agency to go out and argue anything he wants in a vacuum. That's not how this town works."

Many blame the White House's inaction on its preoccupation with the Iran-contra hearings and on a new staff. They predict improvement in coming weeks as space issues are moved off the back burner. The pace of meetings between top White House officials and NASA representatives and members of Congress has picked up in recent days. Many within NASA were heartened simply by the fact that Fletcher managed to get a meeting with Reagan recently.

Frank C. Carlucci, the president's national security adviser, is leading a review of space policy. He met recently with Rep. Bill Nelson (D-Fla.), head of a key space subcommittee, who voiced his concerns about the drift in space policy.

But sources on Capitol Hill say the review has been described to them as nothing more than an effort by the new White House staff to go back through past documents on space policy and see which are still relevant, where there are holes and "put them all in a bunch and tie a ribbon around them."

White House science adviser William R. Graham said, "When we aren't conducting a review of space policy, we are asked why we are not and when we are conducting a review of space policy we are asked why we are."

Graham, who was acting head of NASA at the time of the Challenger accident, is regarded with hostility by many NASA and congressional advocates of civilian space ventures, who say he favors military space programs and has tried to block Fletcher initiatives.

"I'm interested in the national space program, which has a major component in national security and a major component in civil activities," Graham said.

"All of us are distressed," he said. "Not in our darkest nightmares would any of us have imagined we would have an accident with the shuttle, two accidents with the Titan and one with the Delta and Atlas-Centaur in a period of a year and a half."

Some predict that there will be no major decisions about the nation's future in space for a year or more and some say it won't be until a new administration is sworn in.

"It's my belief that the nation will not want to decide on a goal until we are flying the shuttle again," said Philip E. Culbertson, NASA's associate administrator for policy and planning. "I believe NASA has to demonstrate it's back on its feet . . . . There's a lot of work yet to take place before we can package a major new initiative in a way that can be well understood."

The simmering debate over space policy seems to be less about where to go in space than when, and how, and, especially, why.

Ride says her report parallels earlier recommendations by the National Commission on Space. It assesses four major options: an enhanced earth observation program, robotic planetary exploration, the development of a moon base and a manned mission to Mars in the near future.

Sources familiar with the report say it does not support undertaking a Mars mission as soon as possible, a recommendation for which Fletcher and others had hoped

"The assumption we were given {for study} on the Mars program is get there as fast as possible," said Alan Ladwig, NASA's director of special projects, who has worked closely with Ride on the study. "We decided the fast way is not the best way."

Such decisions are much more complex than people realize, he said. "This is not the Sixties." But he added, "How can Mars not be the ultimate goal?"

Clearly, one reason for the continuing indecision is the high cost of doing anything in space while the country struggles with a historic federal budget deficit.

A number of authoritative sources -- including the American Institute of Aeronautics and Astronautics, made up of scientists, engineers, government officials and aerospace officials -- have estimated that at "current and projected budget levels," the nation cannot maintain preeminence in space as mandated in the 1958 space act.

"The nation has a clear choice: provide the necessary funding or redefine our goals," the AIAA cautioned in a recent analysis.

Some say the urgency of the situation has not been conveyed to the public.

"There is a real difference between using the public's sentiments in favor of the space program in a speech and challenging them to make sacrifices," said Rep. Robert G. Torricelli (D-N.J.). "Nobody is telling them {that the U.S. is losing its leadership in space}, because they are listening to the speeches rather than reading the numbers."

Ride told Nelson's House Science, Space and Technology subcommittee recently that any of the options in her report would require "significant investment" on top of the existing NASA budget. Current expenditures on the space program by all agencies are about 1 percent of the gross national product, or about $40 billion a year, according to congressional figures.

"Leadership does not require that the United States be preeminent in all areas and disciplines of space enterprise," she said. But the nation "must move promptly to devise a coherent strategy to retain leadership in those areas we deem important."