Apollo 15 to Apollo 12, and since Apollo 11's backup crew had been designated for Apollo 13 (which did not land on the Moon), they were the first Apollo crew for a successful lunar landing mission to have backed up another such mission. Having had the opportunity to familiarize themselves with the Apollo spacecraft, they could devote more of their training time as prime crew for Apollo 15 to geology and sampling techniques. The astronauts at NASA who were scientists, such as geologist Harrison Schmitt, pushed though the early Apollo missions for a greater place for science as part of the mission,
Apollo 4 NASA in the Apollo spacecraft, also built by North American. The mission was the first Apollo flight after the stand-down imposed after the Apollo 1 fire which killed the first Apollo crew. It was the first to use NASA's official Apollo numbering scheme established in April 1967, designated Apollo 4 because there had been three previous unmanned Apollo/Saturn flights in 1966, using the Saturn IB launch vehicle. The mission lasted almost nine hours, splashing down in the Pacific Ocean, achieving all mission goals. NASA deemed the mission a complete success, because it proved the Saturn V worked, an important step