The report of the presidential commisssion on the Challenger accident concludes that the disaster was a product of eight years of failures by NASA solid rocket engineers and other space agency official who did not correct known design flaws while continuing to let the shuttle fly, sources said yesterday day.

The report, described by one sources as the story of an accident "that need never have happened," recommends a reorganization of the National Aeronautics and Space Administration's management structure to get the space program back on a safe track.

The main report, more than 200 pages long, was sent to the printers yesterday and is scheduled to be president to President Reagan on Friday. Commission members and sources close to the investigation described some of the findings to The Washington Post yesterday, saying they were harshly critical of NASA officials for failing to prevent the Jan. 28 accident that destroyed the shuttle and killed all seven crew memebers.

"The families will probably think it doesn't go far enough," said one source, but "NASA is going to scream bloody murder."

The recommendations of the panel, headed by former secretary of state William P. Rogers, are designed to correct management and technical flaws revealed during more than four months of hearings and on-site detective work at NASA centers and contractor facilities. But it will contain no "bombshells," sources said.

Among the recommendations, according to the sources:

*An enhanced role for astronauts, engineers and contractors in approving launches. Warnings from engineers and contractors in disussions the night before the Jan. 28 Challenger launch failed to reach top NASA officials who made the decision to launch.

*Consideration of an escape system that would allow astronauts to "bail out" from the shuttle and make emergency wate landings at moderate altitudes and under certain conditions, although sources said such a system would not have saved the crew of the Challenger. NASA has said it is studying such a system.

*A change in space agency procedures to prevent NASA managers from signing waivers clearing shuttles for flight when there are cocumented problems affecting flight safety. The panel discovered late in its investigation that solid rocket officials at Marshall Space Fight Center had repeatedly signed such waivers allowing the shuttle to fly despite the fact that the booster gints were officially designated a launch constraint," meaning that to flights should take place until the problem was fixed.

A more centralized structure for NASA manegement, with its Washington headquarters keeping closer tabs on the agency's centers around the country. The centers, particularly the Marshall center in Huntsville, Ala., had been allowed to create individual "fiefdoms" operating increasingly independently of headquarters over the years, sources said.

*Touhened criteria for redesign of the joints on the booster rockets but with many specifics left to NASA, contractor Morton Thiokol and the expert safety panel -- the National Research Council of the National Academy of Sciences brought in by the commission to supervise their work. "We are not in the redesign business," one commission sources said.

The solid-rocket booster joints failed eight out of eight times in tests conducted after the accident as part of the investigation. The tests attempted to simulate conditions of cold at the time of the Challenger launch. Panel members have been critical of NASA for not conducting such tests before the accident. The joints "never has been right from the day they were designed," a panel source said.

The report will restate earlier conclusions that the accident was caused by design flaws in the joints connecting the segments of the right solid-rocket booster, aggravated by the effect of cold temperature on O-ring seals that are suposed to keep the joints from leaking hot gases.

The 13-member commission was appointed by President Reagan six days after the accident. During its first days of work, it was perceived as being protective of NASA. But it quickly assumed an aggressive and at times adversarial posture toward the space agency when it learned that engineers had repeatedly warned against launching Challenger the night before the flight. Rogers recently charged that NASA "almost covered up" evidence of design flaws that caused the disater.

NASA engineers at Marshall who supervised the design and development of the bossters, and those at Morton Thiokol, the contractor who manufactured them, "never really understood how the joint sea worked," said a member of the commission describing the panel's findings. Those engineers "were technically weak."

One the most dramatic chapters of the report, according to commission sources, traces the history of the joints. It describes a long series of written warnings about the joints. "It goes through all the 'I told you sos' dating back to 1978," a commission source said."When you read that," he said, "you feel not so much shock as great disappointment. How could they have seen all those things coming and continued to fly."

The panel will not recommend an outside safety panel, as widely predicted, sources said, but an "internal" arrangement for improved safety checks.

One of the few remaining mysteries the report is expected to resolve is what happened inside the Challenger's crew cabin in the final seconds of flight. Dr. Marvin Resnik, father of astronaut Judith A. Resnik, said yesterday he has been told by NASA that the crew was unconscious "within 10 or 20 seconds" after the fireball engulfed the shuttle. "None of them were aware of what happened," he said.