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 Atlantis Space Shuttle Atlantis Space Shuttle "Atlantis" (Orbiter Vehicle Designation: OV‑104) is a Space Shuttle orbiter vehicle belonging to the National Aeronautics and Space Administration (NASA), the spaceflight and space exploration agency of the United States. Constructed by the Rockwell International company in Southern California and delivered to the Kennedy Space Center in Eastern Florida in April 1985, "Atlantis" is the fourth operational and the second-to-last Space Shuttle built. Its maiden flight was STS-51-J from 3 to 7 October 1985. "Atlantis" embarked on its 33rd and final mission, also the final mission of a space shuttle, STS-135, on 8 July 2011.