Canceled Apollo missions planning their own circumlunar flight for December to upstage the Americans once again (see Zond program). McDivitt's crew—who had grown accustomed to working with LM-3 and preparing for its flight—was kept on the D mission which now became Apollo 9, while Borman's crew would fly the CSM lunar orbit mission on Apollo 8, and the E mission was canceled. The swap of crews was also decisive in who would be the first man to walk on the Moon. Pete Conrad was backup Commander for McDivitt's crew, and by the process of crew rotation, would have been in line for Commander
Apollo 15 Slayton, and after breakfast and suiting up, had been taken to Pad 39A, launch site of all seven attempts at manned lunar landing, and entered the spacecraft about three hours before launch. There were no unplanned delays in the countdown. At 000:11:36 into the mission, the S-IVB engine shut down, leaving Apollo 15 in its planned parking orbit in Low Earth Orbit. The mission remained there for some 2 hours and 40 minutes, allowing the crew (and Houston, via telemetry) to check the spacecraft's systems. At 002:50.02.6 into the mission, the S-IVB was restarted, for trans-lunar injection (TLI), placing the