Yeager gets up before daybreak on Tuesday morning—which is supposed to be the day he tries to break the sound barrier—and his ribs still hurt like a sonofabitch. He gets his wife to drive him over to the field, and he has to keep his right arm pinned down to his side to keep his ribs from hurting so much. At dawn, on the day of a flight, you could hear the X–I screaming long before you got there. The fuel for the X–I was alcohol and liquid oxygen, oxygen converted from a gas to a liquid by lowering its temperature to 297 degrees below zero. And when the lox, as it was called, rolled out of the
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