Apollo 8 initially intended to stay close to home, testing crucial equipment in Earth’s orbit and helping to ensure everything would be ready when the time came to put a man on the Moon. But just four months before launch, the mission was drastically changed and a crew already in training was given a new assignment. They were now tasked with going farther than anyone in history, on a journey that could, with one wrong calculation, leave them stranded in the vastness of space.
With a new mission came a new crew. Astronauts Frank Borman and James Lovell, two Gemini veterans and William Anders, who had never been to space before, were reassigned to Apollo 8 in August of 1968. They were given new objectives, mainly involving testing the crew, command module and equipment between Earth and lunar orbit, as well as in lunar orbit. On the morning of December 21st, 1968 the three man crew squeezed into the command module on top of the Saturn V rocket. Three hours after launch, a fuel boost would increase the spacecraft’s velocity by over 35,000 feet per second, taking astronauts outside of Earth’s orbit for the first time.
After Apollo 8 made the journey from the Earth to the Moon, it needed to enter lunar orbit, a task that had to be done in radio silence on the far side of the Moon--out of communication with the NASA team back on Earth. In order to slow down enough to be captured by the moon’s gravity, Apollo 8’s propulsion system would be fired in reverse for a precise amount of time. If it burned too long, the craft would slow down too much and crash. Too little and it would be traveling too fast, missing the moon altogether, drifting into space without hope of ever returning to Earth.
The maneuver was a success and the module would orbit the Moon ten times before entering the next dangerous phase of the mission. In order to exit lunar orbit, they once again had to rely on their propulsion system. If it failed at this point, the crew would be stranded in the moon’s orbit and most likely would suffocate and perish by New Year’s Eve. Not only was the propulsion system successful, the crew returned to Earth and splashed down less than three miles from their rescue ship.