The numbers seemed reassuring. The space shuttle, so the engineers had concluded, had a flight reliability of 96%. That meant that only 1 out of 25 flights faced a realistic risk of a serious problem. The January 1986 launch of the shuttle Challenger was the program’s 26th. There was a lot that happened that terrible morning that wasn’t supposed to happen. The temperature was not supposed to fall below freezing on the Atlantic coast of Florida. The flexible O-rings in the solid rocket boosters were not supposed to become brittle in the cold. Earlier in the program, when safety technicians reported that the O-rings indeed were subject to failure in extreme temperatures, the warnings were never, ever supposed to go unheeded. But it did get cold, and the warnings were ignored, and the rings did fail, and seven people—including a schoolteacher who was aboard as a demonstration of just how safe space travel had become—lost their lives when one of the solid rocket boosters burned through its housing and ignited the massive liquid fuel tank adjacent to it. The shuttle was a beautiful but ill-conceived machine from the start—one that was too complex to fly with anywhere near the frequency and affordability that the program’s original planners had promised, but too expensive for anyone to admit the error and pull the plug on the whole enterprise. So it flew until it killed—and then, incredibly, it flew some more.