Apollo 8 yet ready to make its first flight. Astronaut Jim McDivitt's crew, who were training to fly the first lunar module flight in low Earth orbit, became the crew for the Apollo 9 mission, and Borman's crew were moved to the Apollo 8 mission. This left Borman's crew with two to three months' less training and preparation time than originally planned, and replaced the planned lunar module training with translunar navigation training. Apollo 8 took 68 hours (almost three days) to travel the distance to the Moon. The crew orbited the Moon ten times over the course of 20 hours, during
Canceled Apollo missions to Apollo 17 under pressure from the scientific community, replacing Joe Engle. Schmitt, a geologist, became the only professional scientist and the twelfth man to walk on the Moon. Slayton's intention for the Apollo 19 crew was the original (prior to cancellation) Apollo 16 backup crew: For Apollo 20 there is even more uncertainty. Based on normal crew rotation, the crew would likely have been: Another possibility would have been: One of the surplus CSMs, CSM-119, was modified to carry two additional crew and kept on standby for a potential rescue mission in case of issues on-board Skylab. During Skylab