THE CHALLENGER DISASTER
Supposed to be a day of "firsts" for the space shuttle, 28 January 1986 is, instead, one of the American space program's darkest. Challenger lifted off with seven crew members, including its first civilian, Christa McAuliffe, a schoolteacher. Less than two minutes into the flight, the huge external tank exploded. The two solid rocket boosters went spiraling away from the blast, and Challenger broke into pieces. Minutes later, its cabin and crew fell into the sea.
A team of scientists and engineers determined that because of the extremely cold weather (the temperature had dipped below freezing the night before), a rubber O-ring seal in one of the solid
rocket boosters was less pliable than it should have been. Instead, of expanding to fill the joint in the booster, it remained stiff. Hot gases ruptured the joint and flames shot out, igniting the thin-skinned external tank, which was filled with liquid, oxygen and liquid hydrogen.
Engineers labored for two years, not only to redesign the joints of the boosters, but to rethink all critical items that went into a shuttle launch. By the time Discovery lifted off on 29 September 1988, safety was the number-one priority, making the shuttle a reliable, but complex and expensive way into orbit.