Bolt, Valve Problems Delay Shuttle Launch

NASA called off the launch of Discovery because of last-minute concerns about bolts on the external fuel tank. A valve problem found later in the space shuttle’s main propulsion system delayed liftoff from Cape Canaveral until at least Monday. The valve, which controls the flow of fuel, appeared to be sluggish during routine operations. The bolt problem occurred Sept. 8 during Atlantis’ launch but was discovered only Wednesday when engineers analyzing film from aboard Atlantis noticed that one of the three bolts between the shuttle and the external fuel tank did not retract properly after launch. At worst, a protruding bolt could cause the separated tank to slam into the shuttle.