Space Shuttle Shuttle orbiter fleet. Sources: NASA launch manifest, NASA Space Shuttle archive On January 28, 1986, "Challenger" disintegrated 73 seconds after launch due to the failure of the right SRB, killing all seven astronauts on board. The disaster was caused by low-temperature impairment of an O-ring, a mission critical seal used between segments of the SRB casing. Failure of the O-ring allowed hot combustion gases to escape from between the booster sections and burn through the adjacent external tank, causing it to explode. Repeated warnings from design engineers voicing concerns about the lack of evidence of the O-rings' safety when the
Space Shuttle retirement Space Shuttle retirement The retirement of NASA's Space Shuttle fleet took place from March to July 2011. "Discovery" was the first of the three active space shuttles to be retired, completing its final mission on March 9, 2011; "Endeavour" did so on June 1. The final shuttle mission was completed with the landing of "Atlantis" on July 21, 2011, closing the 30-year Space Shuttle program. The Shuttle was presented to the public in 1972 as a "space truck" which would, among other things, be used to build a United States space station in low earth orbit in the early 1990s