Regarding crew rotation, the backup crew for Apollo 8 is listed as Armstrong (CDR), Aldrin (CMP, sic) and Haise (LMP). Given the standard crew rotation schedule that would seem to settle the issue of how Armstrong became CDR of Apollo 11, but I know occasional changes were made as missions (including Apollo 8 ) were shuffled and repurposed and individual crew members (e.g., Collins) were taken out and reinstated for medical reasons. So can it still be said that Armstrong's position as backup CDR for Apollo 8 definitely put him in position to be CDR of Apollo 11?
Another argument that Armstrong could not have been picked very far in advance to be the first man on the moon is that he was assigned to command Apollo 11 well before Apollo 10 (and probably Apollo 9, if not 8 ) had been successful. If an earlier flight had failed a major objective, Apollo 11 would probably have been another test flight and Pete Conrad or even Jim Lovell would have become the first man on the moon.
It's interesting that Aldrin was backup CMP on Apollo 8 but became prime LMP on Apollo 11. I wonder why. All the astronauts were given an area of Apollo systems in which to specialize, and Collins' was pressure suits. That would seem to make him a candidate for LMP. On the other hand, Aldrin had done an exceptional job in preparing for his EVA on Gemini XII, and as Dr. Rendezvous he was an obvious choice for a LM crew. Does anyone know for sure how Aldrin moved from the CMP role to LMP? And does his earlier position as backup Apollo 8 CMP explain why he rode in the center seat during the Apollo 11 launch?
