NASA - National Aeronautics and Space Administration

Columbia was rolled back from Pad 39A to the VAB, de-stacked, and the orbiter returned to the Orbiter Processing Facility because of a suspect exhaust nozzle on the right solid rocket booster.

Discovery was rolled back from Pad 39A to the VAB following a pad abort on June 26. The vehicle was returned to the VAB, de-stacked, and the orbiter returned to the Orbiter Processing Facility to remove and replace the number three main engine which caused the abort.

Challenger was rolled back from Pad 39A due to a timing problem with the primary payload, the Tracking and Data Relay Satellite-B. The vehicle was de-stacked in VAB and the orbiter returned to Orbiter Processing Facility. This mission, 51-E, was cancelled and the orbiter re-manifested with 51-B payloads.

Columbia was rolled back twice during preparations for mission STS-35. The first time was from Pad 39A after a hydrogen leak was detected in the external tank/orbiter 17-inch umbilical.

Atlantis was rolled back from Pad 39A to the VAB after tests confirmed a hydrogen fuel leak on the external tank side of the external tank/orbiter 17-inch quick disconnect umbilical. The vehicle was de-stacked.

Columbia was rolled back a second time due to the threat of severe weather from Tropical Storm Klaus. The second rollback was from Pad 39B

Discovery rolled back from Pad 39A to the VAB after significant cracks were found on all four lug hinges on the two external tank umbilical door drive mechanisms. The vehicle was destacked.

Endeavour was rolled back from Pad 39A to the VAB after a pad abort due to an unacceptably high discharge temperature in the high-pressure oxidizer turbo pump on main engine number three. All three engines were replaced in the VAB.

Discovery was rolled back from Pad 39B to the VAB after Yellow Flicker Woodpeckers drilled about 195 holes on the external tank foam insulation, many of which were too high up on the tank to be accessed at the pad for repairs.

Endeavour was rolled back from Pad 39A to the VAB due to the threat of severe weather from Hurricane Erin which passed through Brevard County where the Kennedy Space Center is located.

Atlantis was rolled back from Pad 39A to the VAB due to the threat of severe weather from Hurricane Bertha.

Atlantis was rolled back from Pad 39A to the VAB due to the threat of severe weather from Hurricane Fran.

Discovery was rolled back from Pad 39B to the VAB to repair hail damage to the external tank foam insulation.

Atlantis began rollout to Launch Pad 39A, but an hour later stopped on the crawler path so engineers could troubleshoot a failed computer processor on the crawler transporter. Troubleshooting efforts were unsuccessful, so managers decided to roll Atlantis back into VAB high bay 3 using a secondary computer processor.

Atlantis was rolled back from Pad 39A to the VAB due to uncertainty involving the integrity of the SRB cables.

Discovery was rolled back from Pad 39B in order to get a new, modified external fuel tank in preparation for the Return to Flight mission.

Atlantis began rolling back from Pad 39B to the VAB due to the threat of severe weather from Tropical Storm Ernesto, but weather advisories throughout the day showed that the storm was progressively weakening. Given the improvements in Ernesto's projected path and intensity, NASA chose to reverse the rollback decision and return the shuttle assembly to Launch Pad 39B.

Atlantis rolled back from Pad 39A to the VAB to allow time to troubleshoot a problem with the Hubble Space Telescope on orbit. Hardware to correct the problem will be added to the STS-125 mission payload.

Discovery rolled back to the VAB from Pad 39A for additional work related to its final scheduled mission. Technicians will scan below the foam insulation surrounding the intertank section of Discovery's external tank to look for any issues, such as cracks. They also will reapply foam after removing 89 sensors from the tank's aluminum skin following an instrumented tanking test on Dec. 17.