On Jan. 27, 1986, the former engineer for shuttle contractor Morton Thiokol had joined four colleagues in trying to keep Challenger grounded. They argued for hours that the launch the next morning would be the coldest ever. Freezing temperatures, their data showed, stiffened rubber O-rings that keep burning rocket fuel from leaking out of the joints in the shuttle’s boosters. But NASA officials rejected that data, and Thiokol executives overruled Ebeling and the other engineers. “It’s going to blow up,” a distraught and defeated Ebeling told his wife, Darlene, when he arrived home that night. And it did, 73 seconds after liftoff. Seven astronauts died. Cold weather and an O-ring failure were blamed, and Ebeling carried three decades of guilt. —NPR