On Tuesday large pieces of foam fell off the shuttle Discovery's external fuel tank during launch, causing the agency to essentially ground the shuttle program for the immediate future.

It also appears that in 2003, says the Times report, NASA rejected efforts by outside experts who proposed comprehensive fixes to the foam problem, because the proposals required aggressive redesigns or advanced foam technology that might have required significant investments.

NASA instead chose to fix, at limited cost, an aging launch system that it planned to get rid of by the end of the decade, the Times reports.

Retired Navy Adm. Harold W. Gehman Jr., chairman of the Columbia Accident Investigation Board, acknowledged Thursday that the recommendations to NASA left open a window that would have allowed the same scenario of foam debris falling off and damaging the orbiter's thermal protection system.

"We had precious little faith that they could stop this stuff from coming off," Gehman said in an interview. "And lo and behold, they couldn't."

"We decided it was safe to fly as is,” Bill Parsons, manager of the shuttle program, said Wednesday. “Obviously, we were wrong."

John Pike, executive director of GlobalSecurity.org, a research group in Alexandria, Va., said that accident investigators and NASA regarded the shuttle as an old system unworthy of a major investment.

"Most people will not put a lot of money into a car they are planning to get rid of, and the shuttle is an old car we are getting ready to get rid of," Pike said. "They basically looked at the fixes and said, 'This is good enough for government work.'"

NASA officials say they do not know how long it will take to fix the new foam problems or how it could affect the future of the space program. Until those solutions are in hand, the shuttles are not supposed to fly, the Times reports.