CAPE CANAVERAL, Fla. -- The long-delayed launching of the shuttle Columbia was put off once again yesterday morning when a critical component of the spacecraft's navigation system failed less than a hour before the scheduled liftoff.
"We're very disappointed this happened," said Bryan D. O'Connor, Columbia's commander. "We came back here thinking the orbiter was ready to go. I think we all realize that there are millions of parts involved in this vehicle and that it's a miracle when we do launch."
"Disappointment is something we have to deal with," launch director Robert Sieck said after halting the countdown. It is the second time the liftoff has been canceled in as many weeks.
Columbia, which will carry seven astronauts on the first medical research mission in shuttle history, is now tentatively set to blast off Wednesday.
From a political standpoint, the delay could not have come at a worse time. The National Aeronautics and Space Administration's proposal to build a permanently manned space station is in serious jeopardy in Congress, and key hearings will begin Tuesday in Washington and continue throughout the week. Many critics believe that the shuttle, which would have to make at least 24 flights to build the space station, is not up to the task, and the delay means that the Columbia will be on the ground instead of in orbit when Congress takes up the issue.
"It would be more positive to be flying" as Congress debates the fate of the space station, said Robert Crippen, director of the space shuttle program. But he said that "we could stand up to six months without a launch" during the construction phase of the station, so a few more days now does not mean the shuttle could not perform satisfactorily.
The latest delay in the launch of the aging Columbia, a veteran of 10 other missions, came when one of three inertial measurement units began behaving erratically during pre-launch testing, Mr. Crippen said.