Engineers at Thiokol also were increasingly concerned about the problem. On July 22, 1985, Roger Boisjoly of the structures section wrote a memorandum predicting NASA might give the motor contract to a competitor or there might be a flight failure if Thiokol did not come up with a timely solution.

Nine days later (July 31) Boisjoly wrote another memorandum titled "O-ring Erosion/Potential Failure Criticality" to R. K. Lund, Thiokol's Vice President of Engineering:

"The mistakenly accepted position on the joint problem was to fly without fear of failure and to run a series of design evaluations which would ultimately lead to a solution or at least a significant reduction of the erosion problem. This position is now changed as a result of the [51-B] nozzle joint erosion which eroded a secondary O-ring with the primary O-ring never sealing. If the same scenario should occur in a field joint (and it could), then it is a jump ball whether as to the success or failure of the joint because the secondary O-ring cannot respond to the clevis opening rate and may not be capable of pressurization. The result would be a catastrophe of the highest order-loss of human life."

Boisjoly recommended setting up a team to solve the O-ring problem, and concluded by stating:

"It is my honest and very real fear that if we do not take immediate action to dedicate a team to solve the problem, with the field joint having the number one priority, then we stand in jeopardy of losing a flight along with all the launch pad facilities."

[1] http://history.nasa.gov/rogersrep/v1ch6.htm