Photo credit: Justin Ray/Spaceflight Now

"Rollback" is the term used when the Space Shuttle must be rolled back from the launch pad atop the Mobile Launcher Platform and Crawler-Transporter to the Vehicle Assembly Building (VAB). A variety of factors can necessitate a rollback, ranging from the threat of severe weather to the need for flight hardware repairs that cannot be performed at the launch pad. Shuttle rollbacks to date are listed in chronological order:

STS-9
Columbia
Oct. 19, 1983

Columbia was rolled back 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.

STS-41D
Discovery
July 11, 1984

Discovery was rolled back 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.

STS-51E/51B
Challenger
March 5, 1985

Challenger was rolled back 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, 51E, was cancelled and the orbiter re-manifested with 51B payloads.

STS-35
Columbia
June 12, 1990
1st rollback

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

STS-38
Atlantis
Aug. 9, 1990

Atlantis was rolled back 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.

STS-35
Columbia
Oct. 9, 1990
2nd rollback

Columbia was rolled back a second time due to the threat of severe weather from Tropical Storm Klaus.

STS-39
Discovery
March 7, 1991

Discovery rolled back 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 de-stacked.

STS-68
Endeavour
Aug. 24, 1994

Endeavour was rolled back 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.

STS-70
Discovery
June 8, 1995

Discovery was rolled back 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.

STS-69
Endeavour
Aug. 1, 1995

Endeavour was rolled back 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.

STS-79
Atlantis
July 10, 1996

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

STS-79
Atlantis
Sept. 4, 1996

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

STS-96
Discovery
May 16, 1999

Discovery was rolled back to the VAB to repair hail damage to the external tank foam insulation.

STS-98
Atlantis
Jan. 2, 2001
1st rollback

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.

STS-98
Atlantis
Jan. 19, 2001
2nd rollback

Atlantis was rolled back to the VAB due to uncertainty involving the integrity of the SRB cables.

STS-114
Discovery
May 26, 2005

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

STS-115
Atlantis
Aug. 29, 2006
Partial rollback

Atlantis began rolling back 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 pad 39B.

STS-117
Atlantis
March 4, 2007

After an intense hail storm hit launch pad 39A and damaged the foam insulation on the external fuel tank, Atlantis was returned to the VAB to undergo thorough inspections and repairs.

STS-125
Atlantis
October 20, 2008

Failure of a science instrument command and data handling unit aboard the Hubble Space Telescope and the need to prepare a replacement device delays Atlantis' mission to service the observatory. The shuttle was moved off launch pad 39A to allow other flights to proceed during its half-year postponement.