Apollo 13

Read about Apollo 12

After the success of Apollo 12, the lunar landing missions continued with Apollo 13 next on the list.  Originally, Alan Shepherd was supposed to act as commander for this mission, but NASA didn't feel he was ready for the job, so they pushed him back one mission.  The crew that took his place was James Lovell, Fred Haise, and Jack Swigert.  They had been preparing to man Apollo 14.  Originally, Ken Mattingly was supposed to be the Command Module Pilot, but he was grounded after being exposed to German measles.  The mission was meant to land on the moon and explore the Fro Mauro formation, named after an 80-km wide crater in it.

However, two days into the flight, Swigert stirred an oxygen tank as was standard procedure which was soon followed by a loud noise.  As they would soon learn, one of their two oxygen tanks exploded, and the command module were leaking oxygen.  The explosion also resulted in fuel cells 1 and 3 shutting down in three minutes, and fuel cell number 2 was slowly drained over the next 130 minutes.  To survive, the lunar module was used as a lifeboat, but the return flight would be dangerous, cold, and full of ingenious problem solving.

Because the Apollo 13 crew was so close to the moon (approximately 200,000 miles from Earth), they orbited the moon instead of turning around to save fuel and construct a plan.  However, landing on the moon was now out of the question,so that plan was aborted.  Honestly, what follows is nothing short of amazing, and I can't do the story the justice that it deserves.  So, I'm going to recommend seeing the movie if you haven't.  Also, I recommend reading A Man on the Moon by Andrew Chaikin and watching the mini-series, From the Earth to the Moon.