The head of the U.S. space agency NASA says returning the space shuttle fleet to orbit is proving more challenging than expected. His comments raise the prospect that the first shuttle mission after last year's Columbia accident will be delayed again.
Officially, NASA still says it hopes to return a shuttle to orbit by March or April. Until it does, expansion of the international space station is suspended.
The shuttle fleet was grounded when the orbiter Columbia disintegrated upon re-entry last year. The space agency has been developing new ways of operating shuttles more safely based on 29 recommendations by an expert team that investigated the Columbia disaster.
NASA Administrator Sean O'Keefe says 15 of those recommendations must be carried out before a shuttle can return to the air, but he notes that the agency has completed only three so far.
Mr. O'Keefe says engineers are having a difficult time designing techniques to comply with two of the most important recommendations -- inspecting shuttle damage in orbit and repairing damage of any significant size.
"They are representative of the technical challenges we are encountering to find a solution that we believe comports with the Columbia Accident Investigation Board recommendations," he says. "There may be others that pop up. I have every confidence that come this fall, it will be something else entirely!"
The Columbia accident investigators said the shuttle might have been saved if NASA had possessed in-orbit diagnosis and repair capabilities.
One of the difficulties is outfitting the shuttle's robot arm with a camera that can take steady, sharp pictures at more than 29,000 kilometers per hour of the shuttle's hidden recesses that are impossible to view by other means. Mr. O'Keefe says a bigger problem is working out orbital methods to patch a hole in the shuttle's wing larger than 10 centimeters, such as the big deadly gap in Columbia's wing. The NASA chief says engineers are not even at the stage of testing such repair techniques, and he is not yet confident that they will.
"I am not convinced of anything of what it is going to take to return to flight until I see the evidence as we move forward," he says.
Mr. O'Keefe was speaking to panel of independent experts whom he asked to review his January decision not to launch a shuttle crew to repair the Hubble Space Telescope next year. NASA expects the observatory to last only through 2007 because its batteries and stabilizing gyroscopes are failing. A U.S. public outcry forced him to seek the panel's advice on whether to reinstate the shuttle mission or develop a robotic repair capability.
He says the problem of developing in-orbit inspection techniques has bearing on this because without a robot arm camera, it would be difficult to see shuttle damage when docked to the telescope. At the space station however, astronauts might be able to observe it from inside the outpost. In addition, the station could provide safe haven for a shuttle crew.