Apollo astronauts and engineers tell the inside story of Apollo 8, the first manned mission to the moon. The U.S. space program suffered a bitter setback when Apollo 1 ended in a deadly fire during a pre-launch run-through. In disarray, and threatened by the prospect of a Soviet Union victory in the space race, NASA decided upon a radical and risky change of plan: turn Apollo 8 from an earth-orbit mission into a daring sprint to the moon while relying on untried new technologies. Fifty years after the historic mission, the Apollo 8 astronauts and engineers recount the feats of engineering that paved the way to the moon. Airs December 26 at 9 pm on PBS