Apollo 9 in early 1969. However, LM problems again prevented it from being ready for the D mission by December, so NASA officials created another mission for Apollo 8 using the Saturn V to launch only the CSM on the first crewed flight to orbit the Moon, and the E mission was cancelled as unnecessary. Slayton asked McDivitt and Borman which mission they preferred to fly; McDivitt wanted to fly the LM, while Borman volunteered for the pioneering lunar flight. Therefore, Slayton swapped the crews, and McDivitt's crew flew Apollo 9. The crew swap also affected who would be the first crew
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