The Physical Cause

Insulating foam separates from external tank 81 seconds after lift-off

Foam strikes underside of left wing, breaches thermal protection system (TPS) tiles

Superheated air enters wing during re-entry, melting aluminum struts

Aerodynamic stresses destroy weakened wing

A Flawed Decision Process

Foam strike detected in launch videos on Day 2

Engineers requested inspection by crew or remote photo imagery to check for damage

Mission managers discounted foam strike significance

No actions were taken to confirm shuttle integrity or prepare contingency plans

January 28, 1986, the shuttle Challenger explodes 73 seconds into its launch, killing all seven crew members

Investigation reveals that a solid rocket booster (SRB) joint failed, allowing flames to impinge on the external fuel tank

The Commission also determined that:

SRB experts had expressed concerns about the safety of the Challenger launch
NASA’s culture prevented these concerns from reaching top decision-makers
Past successes had created an environment of over-confidence within NASA
Extreme pressures to maintain launch schedules may have prompted flawed decision-making
The Commission’s recommendations addressed an number of organizational, communications, and safety oversight issues

NASA’s successes (Apollo program, et al) had created a “can do” attitude that minimized the consideration of failure
Near-misses were regarded as successes of a robust system rather than near-failures
No disasters had resulted from prior foam strikes, so strikes were no longer a safety-of-flight issue
Challenger parallel… failure of the primary o-ring demonstrated the adequacy of the secondary o-ring to seal the joint
A weak sense of vulnerability can lead to taking future success for granted… and to taking greater risks