No they knew of O-ring burns before the catastrophe. They measured it, and determined that it was a tolerable amount, because it was less then 10% penetration.

No they knew of O-ring burns before the catastrophe. They measured it, and determined that it was a tolerable amount, because it was less then 10% penetration. Problem was the root cause of the burns was not adequately determined. When you don't know the o-rings are twisting due to internal stress and that those stresses have a dependence on temperature, you miss that catastrophic O-ring failure is a risk at near freezing temperatures. The second space shuttle crash was the same problem again. Falling chunks of ice and foam. Since nothing major had happened previously, it was assumed everything would be fine. These failure and problems were the warning signs that something was wrong. There was no design spec for acceptable o-ring burn through or a leading edge heat shield damage threshold spec. I bet we will find that Boeing and the FAA talked themselves into believing that