Apollo 9 to land on the Moon; when the crews for Apollo 8 and 9 were swapped, their backup crews were also swapped. Since the rule of thumb was for backup crews to fly as prime crew three missions later, this put Neil Armstrong's crew (Borman's backup) in position for the first landing mission Apollo 11 instead of Pete Conrad's crew, who made the second landing on Apollo 12. Apollo 9 was the first space test of the complete Apollo spacecraft, including the third critical piece of Apollo hardware besides the command and service module and the Saturn V launch vehicle—the lunar
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