Releasing its first set of recommendations, the investigation board also said NASA should make it a standard requirement to have pictures taken of orbiting shuttles to check for potential damage on every flight. NASA has already agreed to do so with the military's help.
The two preliminary recommendations come 2½ months after Columbia disintegrated over Texas, almost certainly because of a breach along the leading edge of the left wing that let in hot atmospheric gases. That deadly gap may have been caused by a chunk of foam insulation that broke off the shuttle's fuel tank shortly after liftoff and slammed into the wing.
Before shuttle flights resume, the board said, NASA should implement a comprehensive inspection plan for the reinforced carbon-fiber panels and seals that cover the leading edges of shuttle wings. This inspection plan should take advantage of advanced technology, the panel said.
NASA's current methods for inspecting these carbon pieces between flights — tapping on them to find hidden air pockets and conducting visual checks — are inadequate, the board said. Defects have since been found in these parts through nondestructive tests like X-rays or CAT scans, the board said.
The chairman of the Columbia Accident Investigation Board, retired Navy Adm. Harold Gehman Jr., has said repeatedly that age-related wear and tear may have weakened some of the wing parts enough to break when struck by launch debris.
The board plans to release its final report this summer and, at that time, include the probable cause of the accident as well as any contributing factors and additional recommendations.
Earlier this week, Gehman said other preliminary recommendations are "percolating up" and will be released as soon as they are formally reviewed.
"Not everything we find is going to make it up to the level of a recommendation," Gehman said. "But if it's going to be a recommendation in the final report, then we tell NASA about it now" so that the space agency can begin work.
Gehman said it's possible the board will not be able to pinpoint the exact cause of the Feb. 1 catastrophe. "That's why we're being so careful about the recommendations, to make sure they're generic enough to not fall in love with a specific scenario," he said.
NASA already is looking at ways to improve shuttle safety in the wake of the accident. Engineers are considering putting a lightweight metal cover over the area where the foam peeled off Columbia's fuel tank in January, to prevent future shedding, and are studying ways that spacewalking astronauts could repair damage to their ship's outer thermal layer.
The seven astronauts aboard Columbia had no such repair kit. NASA and contractor engineers concluded during the flight that the launch debris caused no severe damage and safety was not jeopardized; as a result, no photographs of the damaged area on the wing were ordered.