I was seven years old when this happened, and I remember when I first saw the video I was absolutely horrified.
Watching it again, I still get a catch in my throat.
On January 28th, 1986, the Space Shuttle Challenger exploded 73 seconds after liftoff. During deceleration, the O-rings used to seal the solid-fuel rocket boosters, which had frozen in the cold weather by the time of launch and could not be extruded in time to seal the joints, disintegrated. This caused the catastrophic failure of the structural integrity of the shuttle under its extreme acceleration, tearing it apart. The shuttle capsule then went into freefall. Three of the astronauts managed to get their emergency air turned on before they passed out. All aboard died when it hit the surface of the water at 333km/h. The crash caused a deceleration of 200 g — well beyond the momentary survivable crash impact of 100 g, and also well beyond the “likely death or injury” level of 50 g.
Richard Feynman famously took NASA to task over their wagon-circling during the blame game that ensued. He performed a modicum of science in a courtroom showing that the O-rings when frozen didn’t have the resiliency to seal the rocket boosters, exposing their internal self-perpetuating blindness to proper safety protocols. Like the parable of the man who wills himself into believing the boat he just sold to some emigrants will make one more voyage across the Atlantic despite knowing it cannot — the scientists within NASA were intentionally blinding themselves to the possibility that they had done something wrong. And in so doing, they were endangering the very new practice of reaching out and discovering the universe.
Thank science for men like Feynman.