Apollo 8 was a major milestone for manned spaceflight. It was the first human spaceflight to leave Earth's orbit. The space race was still on and the Apollo program was slipping behind. To counter this, the Apollo 8 mission was changed to a more expansive mission that including going to the moon, orbiting the moon and returning, instead of the one originally planned of just orbiting the Earth.
Apollo 8 proved that it was possible for men to reach a lunar orbit and return. This was big. Now we knew that the landing on the moon was possible and just a few more test flights would pave the way to actually stepping foot on the moon.
This was also the first manned test of the massive Saturn V Rocket. This was no small mission. The previous unmanned Saturn V tests had failed. Severe cyclic oscillation during liftoff put extreme pressure on the rocket's structure. This oscillation became known as POGO because of the similarity to the bounce occurring in a child's pogo stick.
POGO was the result of the liquid fuel cells sloshing up and down during liftoff. As the rocket accelerated the slosh created excess pressure in the fuel pump which caused too much fuel reaching the thrusters. This then created a wildly increasing effect that would eventually lead to catastrophic event.
Problems were also detected in the upper stages. Research determined that when the rocket reached the vacuum state of the upper atmosphere, the fuel lines ruptured causing the engines to shutdown.
These problems were corrected by improving the fuel lines and putting shock absorbers on the rocket engines to dampen the POGO effect.
December 21, 1968 / Launch Complex 39-A
Frank Borman, Commander
James A. Lovell, Jr.
William A. Anders
Demonstrate crew/space vehicle/mission support facilities during manned Saturn V/CSM mission. Demonstrate translunar injection, CSM navigation, communications, and mid course corrections. Assess CSM consumables and passive thermal control. Demonstrate CSM performance in cislunar and lunar orbit environment. Demonstrate communications and tracking at lunar distances. Return high-resolution photographs of proposed Apollo landing sites and locations of scientific interest. All mission objectives were achieved.