It was the third preliminary recommendation issued by the investigation board in advance of its final report, due out in a month. NASA Administrator Sean O'Keefe said Thursday he hopes to resume shuttle flights by April.
Astronauts should inspect their spaceship's vulnerable thermal shell early in every mission, the investigators said. They noted that at present there is no proven way to inspect for damage or conduct repairs in orbit to either the insulating panels on the leading edge of the wings or tiles elsewhere.
During Columbia's final flight, "the lack of repair capability was cited repeatedly and may have been a factor in decisions made" while the shuttle was in orbit, the board said. That includes decisions by shuttle managers not to seek satellite images that may have helped engineers assess the damage from a foam strike to the left wing, the panel said.
Investigators believe a 1½-pound chunk of foam insulation that broke off the fuel tank during liftoff breached Columbia's left wing and doomed the spaceship. The shuttle shattered over Texas on re-entry Feb. 1 after hot air penetrated the hole and melted the wing. All seven astronauts were killed.
In a written statement, the investigators stressed that the recommendation "does not reduce the urgency or importance of aggressively reducing all sources of potential damage to the orbiter." Maximum safety can be realized only by reducing the likelihood of damage to the shuttle, as well as coming up with the ability to detect and repair any problems, they said.
On Thursday, O'Keefe said the space agency will meet and even exceed the safety recommendations of the Columbia investigators, doing everything "humanly possible" to prevent another disaster.
"The effort we need to go through, the high bar we need to set for ourselves, ought to be higher than anything else anybody else would levy on us," O'Keefe said during a visit to Kennedy Space Center to announce its new director, James Kennedy.
His statements came two days after the Columbia investigators outlined what NASA should do before launching another shuttle. Among the suggestions that will be in the board's final report: eliminate as much fuel-tank foam loss as possible and strengthen the shuttle's exterior so it can withstand debris, and improve astronauts' ability to repair damage from such blows.
NASA likely will put a robot arm and spacewalker jetpacks on every mission for wing inspections, O'Keefe said. Columbia's crew was equipped with neither.
O'Keefe agreed with the chief investigator's assessment that NASA should be able to make all the necessary repairs in time for a launch six to nine months from now.
"We're roughly in the same pew, as it were," he said.
In April, the investigators recommended that NASA improve its preflight inspection of wing panels and require shuttle imaging by spy satellites on every mission to check for potential damage.
Based on what the board has indicated so far, shuttle Atlantis could fly anywhere from December to April, O'Keefe said. He suggested that December is unlikely, given that there are only a few days in December that Atlantis, the next ship in line, could be launched to the international space station.
NASA's new requirement for daylight liftoffs, in order to photograph any shedding foam and other debris, severely limits the number of potential launch days, O'Keefe noted.
"We want to make sure every square inch of this is photographed," he said.
The shuttle fleet was grounded nearly three years after the 1986 Challenger explosion. If flights resume in April, the fleet will have been grounded for 14 months this time.
NASA's top spaceflight official, former astronaut Bill Readdy, said foam almost certainly will be eliminated from the section of the tank where it broke loose during Columbia's launch in January and on at least six previous flights. Heaters will be attached to the surface there to prevent ice from forming once super-cold fuel is pumped into the tank.