Daydreamer99 wrote:

I'm not an expert. lets down scale this to model rocketry. If
the area where the O ring was compromise the leak or explosion could
have taken place anywhere.



The area where it failed at was the one that got a great deal of stress
put on it during the "twang"- when the shuttle makes the rest of the
launch stack bend as its engines are ignited before SRB ignition. The
area of the SRBs astern of the aft attachment point to the ET undergo
the most stress during this event; and indeed film of the Shuttle on the
pad showed a jet of smoke emerging from the the field joint that would
later burn through on SRB ignition and prior to lift-off. This was due
to the O-rings on that field joint being unseated by the "twang" and
unable to reseat themselves due to their low temperatures making them
inflexible.

Pat