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"I refused to sign it," McDonald said. "I just thought we were taking risks we shouldn't be taking."
Along with the O-ring problem, McDonald also raised concerns about ice on the launchpad that could damage the spacecraft and rough seas at the location where the booster rocket was supposed to be recovered.
"I said, 'Let me tell you something. I sure hope nothing happens tomorrow, but if it does, I am not going to be the person to stand in front of a board of inquiry and explain why I gave you permission to fly my rocket boosters in an environment I knew they would never qualify to fly in,'" McDonald recalled telling officials ahead of the ill-fated flight.