A scant five months after Apollo 17 splashed down in the Pacific Ocean in December of 1972, NASA launched Skylab to begin a new phase of American manned spaceflight – space station operations.
Max Faget’s position was that considering the difficulty of the job, if each mission was successful half the time, it would be well worth the effort. But Gilruth thought that was too low. He want a 90% mission success ratio and a 99% ratio for Astronaut safety. Walt Williams who was currently running the Mercury program believed that astronaut safety needed to be limited to only 1 failure in a million which was 99.9999%.
…From the information they gathered on the existing technical problems, Disher and Tischler concluded that prospects were only one in ten that Apollo would land on the moon before the end of the decade….