KENNEDY SPACE CENTER, Fla. — The shuttle Discovery, already delayed three times by technical problems and bad weather, was grounded again Friday, this time by a potentially dangerous gaseous hydrogen leak in a vent line attached to the ship's external tank.
The shuttle was initially scheduled to make its 39th and final flight last Monday, bearing fresh supplies and an intelligent robot for the International Space Station. Complications delayed the flight from Monday to Friday, though, when the hydrogen leak led NASA to conclude that the shuttle would not be ready to launch before its flight window closed this Monday.
Almost at the same time that NASA managers were deciding to delay another attempt until Nov. 30, the opening of the next available launching window, engineers spotted a 7-inch-long crack in protective foam insulation on the side of the giant tank.
The crack, on the side of the tank facing the Discovery, represented a possible source of debris that could have posed a threat to the shuttle's fragile heat shield during the climb out of the dense lower atmosphere.
Officials said the crack would have been spotted during normal pre-launching inspections and most likely would have prompted a delay even if the hydrogen leak had not developed. In the end, senior NASA managers decided to take the time needed to make sure the problems were well understood and repaired before making another attempt.
"We will come back in late November and give it another shot," said Michael Leinbach, the launching director. "We're going to fly when we're ready, and clearly we were not ready to fly today."
The Discovery's six-member crew — Cmdr. Steven W. Lindsey; Col. Eric A. Boe of the Air Force, the shuttle pilot; Col. Benjamin A. Drew Jr., also of the Air Force; Col. Timothy L. Kopra of the Army; Nicole P. Stott; and Dr. Michael R. Barratt, a physician-astronaut — flew back to Houston after the launching scrub was announced.
The Discovery is attempting an 11-day mission. It will be loaded with a new cargo module, more than 6,000 pounds of supplies and equipment and a spare set of cooling system radiators that will be stored outside the lab complex.
Because of temperature issues related to the space station's orbit, NASA will have only about one week, from Nov. 30 through Dec. 5 or 6, to get the Discovery off the ground this year. Otherwise, the flight could be delayed until late February, throwing a wrench into NASA's plans for carrying out a final three missions and retiring the shuttle fleet by next summer.