A panel of safety experts has repeatedly warned NASA that the ambitious schedule of shuttle flights to begin this year posed potentially major organizational and safety hazards to the agency and its astronauts.

The Aerospace Safety Advisory Panel, a group of specialists who serve as consultants to the National Aeronautics and Space Administration, urged that, as the pace of shuttle launches increased, special steps be taken to guard against fatigue and lackadaisical performance by the crews that assemble and launch the complex vehicles.

Meanwhile, a member of the panel said in an interview today that six- and seven-day workweeks are common for the shuttle assembly and preparation teams at the Kennedy Space Center here. Norman Parmet, a retired Trans World Airlines executive and longtime member of the safety panel, said, "I hated to see seven-day workweeks in the aviation business. Quality and quantity suffer."

Possible fatigue of launch technicians and workers who assemble the shuttle orbiter, its main fuel tank and its complicated solid rocket boosters has surfaced as a prelaunch concern at pad 39B, where Challenger was launched Jan. 28 only to explode 74 seconds later, killing its seven crewmembers.

NASA officials have had little to say about this aspect of the events leading up to the disaster. And workers at the space center here have been cautioned not to talk to reporters.

Attempts to reach NASA officials today for comment were unsuccessful.

The concerns of the safety panel, set up after the 1967 Apollo capsule fire that killed three astronauts, began to emerge early in this decade, as the shuttle's first test flights approached.

While generally giving NASA high marks for its achievements, the panel began discussing the issue of safety versus flight scheduling as long ago as 1982, and with each annual report, its concerns have been stated more bluntly. The panel has expressed fear that an agency dedicated to space research and development could not easily transform itself into an effective manager of routine shuttle flights -- as NASA publicity claims.

"An effort to build a truly operational system within an organization structure dominated by the development centers is likely to fail," the panel cautioned in its 1982 report. "This is the core of NASA's present management dilemma.

"The development centers are not attuned by experience or philosophy to the management discipline essential to a successful commercial operation."

The centers referred to are the Marshall Spaceflight Center in Huntsville, Ala.; the Kennedy Space Center here, and the Houston Space Center, where Mission Control is located. NASA also operates other research and development facilities.

In 1983 the space agency hired Lockheed Space Operations Corp. as prime contractor for assembling, preparing and launching the shuttles. But NASA maintains overall management reponsibility, employing more than 2,000 of the approximately 15,000 workers at the launch facility here.

In its 1983 report, the safety panel expressed concern that "safe" rapid turnaround of the shuttle between missions might be jeopardized by NASA budget-cutters.

NASA officials have said that their ambitious 1986 launch schedule, which had been delayed several times before the Challenger flight, was not a factor in their decision to launch Challenger on the morning of Jan. 28 despite abnormally cold weather.

In its 1983 report, the panel criticized NASA management for a "continuing strong bias to spend limited resources on major performance changes and to relegate changes for reliability and safe reduction of turnaround time to a lower priority."

In its next annual report, the panel reminded NASA that "there must be no disruption in the operational . . . ability to safely launch and turn around" the shuttle.

In its 1983 oversight survey, the advisory group went into great detail in urging NASA to assure worker motivation and quality control. While noting that the majority of NASA employes are "conscientious, qualified . . . people who want to do a good job," it said "the worker should know why certain procedures are demanding if he is expected to produce a perfect product . . . . Worker motivation . . . is a difficult but rewarding task."

Parmet said he doubts that NASA will ever be able to meet its proposed schedule of a two-week turnaround between flights. "About a month . . . is as short a time as they are going to get," he said. NASA had scheduled 14 shuttle flights for 1986, 19 next year and 12 in the first eight months of 1988.

Thirteen of those flights were to be made by Challenger. Its explosion has called the entire schedule into question, just as NASA was promoting the shuttle as an operational reality.

Meanwhile, reports of fatigue and frayed nerves among workers at the space center here continue to emerge. "There's a common complaint of 75- to 80-hour workweeks," said Daniel Faherty, a lawyer whose practice includes workman's compensation cases. " . . . They work around the clock in the Orbiter Processing Facility. There's a lot of overtime pay for people who would like to see a little daylight outside the job and spend some of their overtime money."

While workers have been warned not to talk to reporters, at least one employe has given a detailed account of widespread fatigue on the assembly crews that put together the solid rocket boosters that help lift the shuttle into orbit. Challenger's right-hand booster is suspected of a malfunction that set off the explosion.