You can say that the Apollo 11 moon mission was a triumph of teamwork and technology. And you'd be right. But there was also a lot of luck involved, because quite a few things went wrong. Some of those things were overcome by cool decision-making and backup plans. The close brush with catastrophe on re-entry was not even known until after the landing. A new book by Nancy Atkinson, Eight Years to the Moon: The History of the Apollo Missions, details many of those unexpecteded dangers. The worst was when Apollo 11 was coming home, and discarded the service module, which was no longer needed.
About 15 minutes before the astronauts splashed into the Pacific Ocean, the CSM fully separated into its two parts. This was necessary because only the command module (which held the crew) had a heat shield. The heat shield protected the astronauts by deflecting and absorbing the scorching energies created by plowing through Earth's atmosphere at about 25,000 mph — more than a dozen times as fast as a speeding bullet.
The service module became useless and posed a collision risk after the two parts separated, so it was supposed to skip off Earth's atmosphere like a stone thrown across a pond.
But it did not.
The discarded module fell on the same trajectory as the command module. If the service module, or the parts it broke into, had collided with the command module, the three astronauts would not have survived. Read about the near-miss at the last leg of Apollo 11, and why it was kept secret afterward, at Insider. -via Damn Interesting
(Image credit: NASA)