What was identified as the main cause of the Challenger explosion?

The primary cause of the Challenger explosion was the failure of the pressure seal in the aft field joint of the right solid rocket motor. This failure occurred due to the O-rings, which were meant to provide a seal between the segments of the solid rocket motor, becoming compromised in cold weather conditions. On the day of the launch, temperatures were unusually low, which affected the flexibility and integrity of the O-rings, preventing them from sealing properly. As a result, hot gases escaped from the right solid rocket motor and ultimately led to the destruction of the Challenger during ascent.

This understanding underscores the importance of considering environmental factors and material performance in engineering designs, especially in aerospace applications where conditions can vary significantly. The investigation into the Challenger disaster highlighted the need for rigorous testing and evaluation under varying conditions to prevent similar failures in future missions.