With much of what will be in the Columbia Accident Investigation Board (searchreport already publicly announced, NASA administrator Sean O'Keefe said the space shuttle fleet should be able to safely return to orbit no later than next April.

O'Keefe, meeting Tuesday with reporters, said that most of the issues to be addressed in the report have been openly reviewed by the board and that NASA (search) is already taking action on the items.

"There is nothing that we have seen so far that will preclude" a return to space in six to nine months, O'Keefe said.

The administrator said the agency is already looking at ways to make repairs in orbit if a space shuttle is damaged during launch. He said the agency also is redesigning part of the space shuttle external fuel tank to assure that a large chunk of insulation will not fly off and hit the shuttle during launch.

The Columbia Accident Investigation Board has announced that its "working scenario" on the cause of the accident is that a suitcase-sized piece of foam, used to insulate a bipod fixture on the external fuel tank, peeled off during launch and struck Columbia's left wing.

The collision is thought to have punched a hole in the heat shield. When Columbia later returned to Earth, the 3,000 degrees of re-entry heat entered and destroyed the wing. The spacecraft came apart, scattering pieces over East Texas and Louisiana.

"There will not be bipod insulation on the next shuttle that flies, or on the ones after that," O'Keefe said. "That is a guarantee."

The bipod insulation was to prevent the build up of ice caused by the chill of the liquid hydrogen and oxygen propellant. O'Keefe said that insulation will be replaced by heaters that will prevent formation of ice.

During experiments on a mock up of the shuttle wing last week, CAIB investigators showed that a 16-inch hole could be punched through the heat shield by the collision of foam insulation.

O'Keefe said that a hole that big in the wing "probably could not be repaired" in orbit by spacewalking astronauts. However, the administrator said that if the Columbia wing breach had been that large there would have been indication from sensors in the wing.

NASA engineers are now "looking at what is a reasonable amount of damage that could be repaired" in orbit, said O'Keefe.

O'Keefe acknowledged that more than half of the CAIB report will deal with management changes needed at NASA to assure the safety of the space shuttle.

He said a major change that will comply with the CAIB recommendations is the establishment of an independent engineering safety center at NASA's Langley Research Center (searchin Hampton, Va.

The administrator said the center will have independent safety experts who will evaluate problems with the space shuttle and other NASA spacecraft and determine when it is unsafe to fly.

The safety watchdogs will be separate from the engineers who are part of specific programs in NASA and will, thus, be removed from the schedule and launch pressures of those programs. Yet, the safety experts will actively participate in key management meetings where launch decisions are made, said O'Keefe.

"Having them there continuously assures we will have a removed, objective view on those activities," he said.

O'Keefe said that one of the problems uncovered in the Columbia investigation was that safety engineers were included as part of the space shuttle team and did not have the objectivity of distance from the program goals.

This can lead, he said, to engineers tending to accept the abnormal as normal, and prevent them from noticing problem trends that could lead to disaster.

For instance, space shuttle engineers had known for some time that foam insulation was peeling off the propellant tank during launch, but when nothing happened this abnormal event eventually was accepted as not threatening.

The new safety organization, O'Keefe said, will have an independent objectivity that should spot unsafe trends. Plus, the safety engineers will have the authority to halt launches if problems are not solved to their satisfaction.

"Theirs will be an independent look that is not just persuasive, but directive," he said.

To encourage engineers throughout NASA to raise safety concerns, O'Keefe said the new organization will receive e-mail comments from "anybody who thinks something is off." He said the safety organization "will make this a really easy thing to do."