"Clearly, this could lead to a shedding of foam debris, along with this heavier weight SLA, which we now know could have a debris transport path to the underside of the orbiter," Hale said. "Therefore, we've decided that this is an unacceptable situation."

While a change to the brackets was already in progress on tanks now in production, the problem on the tank being used for STS-120 will be remedied by using different foam on the brackets. According to NASA workers will travel to the Kennedy Space Center from the Michoud Assembly Facility in New Orleans to replace the existing foam and underlying thermal protective agent on the brackets with lightweight foam. The process is expected to take approximately nine days.

Wayne Hale said that even with the work planned on the next shuttle's external tank, the STS-120 launch remains targeted for Oct. 23.

"We have looked at the launch schedule and that will still allow us, with a number of days of reserve, to launch the next shuttle mission on October the 23rd. We're looking at downstream schedules, but at first review of those schedules it appears that we can still launch the subsequent mission by the end of the December launch window ... with very little to no contingency time."

Hale pointed out that the safety of Discovery is more important then the liftoff schedule. "The point is, we will take the amount of time that we need to to get this repair done properly," he said. "We will not rush and if we happen to fall a day or two after the 23rd, that is not a huge impact to our schedule. The schedules for the following flights obviously are more fluid and we'll be reviewing those as the work goes forward."

Set for launch on October 23, STS-120 will be the twenty-third mission to the International Space Station and will deliver the U.S. Node 2 Harmony module expanding the space station's capability for future international laboratories.

Air Force Col. Pamela A. Melroy will command the STS-120 mission to take the Node 2 connecting module to the station. Melroy is the second woman to command a shuttle.

“STS-120 is such a cool mission,” says Commander Pam Melroy. “Node 2 is the expansion of the space station’s capability to bring international laboratories up. It’s the expansion of our capability to carry additional people. "It has additional life support equipment that will allow us to expand out beyond a three-person crew. It’s this big boost in the capability which is really exciting,” she said.

Built in Italy for the United States, Harmony is a high-tech hallway and Tinkertoy-like hub. It is a 23- by 14-foot passageway that will connect the U.S. segment of the station to the European and Japanese modules, to be installed later this year and early next year, respectively.

Harmony will be the first new U.S. pressurized component to be added to the station since the Quest Airlock was attached to one of Unity's six berthing ports in 2001.

Expedition 15/16 Flight Engineer Clayton Anderson will return to Earth from the space station aboard shuttle mission STS-120. That flight will carry his replacement, Daniel Tani, to the station. Tani will return on shuttle mission STS-122.

On August 8, one minute after Endeavour’s launch, the debris, which likely had some SLA or ice attached, ricocheted off a metal strut to carve a gouge on space shuttle’s heat shield.

After Endeavour’s astronauts conducted a video inspection it was revealed that the gouge, located near the ship's right wheel well, was 30.5 x 25.5 millimeters (1.2 x 1.0 inches) large (smaller than initially reported) and 28.5 millimeters (1.12 inches) deep.

Though, NASA mission managers in Houston decided not to repair the space shuttle Endeavour’s heat shield. NASA said the damage was not enough to risk a catastrophic failure of the shuttle's heat shield, like the one that destroyed the shuttle Columbia on re-entry in February 2002, but the process of underside repairs during a spacewalk would have entailed risks for the astronauts.

NASA has been grappling with the problem since undetected damage to the ceramic tiles was blamed for the disintegration of Columbia during re-entry in February 2003 that led to the deaths of seven astronauts.

On August 21, after twelve days spend in space, the space shuttle Endeavour landed safely at the Kennedy Space Centre in Florida, a day earlier than planned because of the hurricane Dean.