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
Journey of Apollo 15 to the Moon so that there was even heat distribution. Nearly 15 hours after launch, the crew switched off the lights in the cabin and went to sleep. The second day of Apollo 15 centered around the second planned midcourse correction and a preliminary check of the Lunar Module, "Falcon". Mission Control first got the crew to perform a 0.7 second burn of the SPS engine before the planned second course correction. This was designed to isolate the location of the short in the Delta-V Thrust switch. The burn allowed Mission Control to confirm that the SPS would only be ignited accidentally if