Houston, We Have A Problem: The True Story Of Apollo 13
The Apollo 13 mission was supposed to be NASA's third lunar landing, but it was plagued with misfortune from the very beginning. In fact, the crew that wound up going, consisting of James Lovell, Jack Swigert, and Fred Haise, wasn't even the original crew. Only days before takeoff, it was discovered that several of the training Apollo astronauts had been exposed to the measles thanks to an outbreak at one of their kids' schools, so Jack Swigert had to replace Ken Mattingly as the command module pilot only two days before liftoff.
Still, everything seemed fine at liftoff, usually the most dangerous time for such missions. Things were smooth sailing until hour 56, when the electricity suddenly went haywire and the astronauts were startled by a loud bang. They quickly learned, to their horror, that an oxygen tank on board had exploded. It turned out that during construction of the spaceship, the liquid oxygen tank had been dropped on the factory floor, damaging the delicate interior plumbing. Though it worked once in the equipment test days prior to launch, by refilling the damaged tank with liquid oxygen, they had inadvertently turned it "into a bomb waiting to go off."