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The space shuttle Challenger disaster occurred on occurred on January 28, 1986. The shuttle broke apart over the Atlantic Ocean just 73 seconds after lifting off from its launch pad in Florida. All seven crew members were lost. The disaster was precipitated by the failure of an o-ring assembly in the right solid rocket booster.
The o-ring failure caused a breach in a solid rocket booster(SRB) joint that it sealed. The failure allowed pressurized hot gas from the solid rocket motor to reach the outside and interfere with the adjacent SRB attachment hardware and external fuel tank. The interference was significant enough to cause the separation of the right-hand SRB’s aft attachment and then the structural failure of the external tank. Active aerodynamic forces quickly broke the orbiter apart.
The Challenger space shuttle never actually exploded. The enormous fireball that many people saw was the fuel and oxidizer that was released when the external tank disintegrated. It is impossible to know at which exact moment the crew members died, but it is known that some survived the initial break up and died when the crew compartment impacted with the ocean. There was no escape plan in place for such an emergency. The shuttle program was halted for 32 months while the Rogers Commission, which was formed by the Reagan administration, looked into the causes of the accident and possible counter measures to prevent another similar incident in the future.
The investigation of the Rogers Commission led to several conclusions. The most important being that NASA’s organizational culture and decision-making processes had been key contributors to the accident. Managers had known that the SRB design contained a potentially catastrophic flaw in the o-rings since 1977. They failed to address it properly for a decade. The same managers had disregarded warnings from engineers about the dangers of launching because of the cold temperatures that morning. After ignoring the engineers, they had failed to adequately report these technical concerns to their superiors.
Several times NASA had considered building an escape system into the space shuttle design. Each time the idea was dismissed after the costs were found to be too high and the limitations it would put on crew size too limiting. Escape from the a space shuttle is only possible as the shuttle is gliding just before landing.
We’ve recorded an episode of Astronomy Cast all about the space shuttle. Listen here, Episode 127: The US Space Shuttle.