Columbia mission this year, with just a few days in late September and a few days in November available for flights to the International Space Station. President George W. Bush has ordered the shuttle fleet to be retired in 2010. It would be replaced with a new space vehicle capable of returning Americans to the moon and taking humans to Mars. But the space station depends on the shuttle because it is the only spacecraft capable of carrying large components into space. Assembly of the 16-nation project was halted after the Columbia accident and may remain on hold a while longer. Despite a backlog of station components awaiting launch, NASA chief Michael Griffin said the agency will not be rushed. "We're going to go when we're ready," he said.
