Apollo 15 went unused, due to the explosion that damaged the Apollo 13 spacecraft. Apollo 14's CMP, Stu Roosa, was enthusiastic about geology, but the mission commander, Alan Shepard, less so. Scott, once assigned as Apollo 15 commander, was determined that his crew bring back the maximum amount of scientific data possible, and met with Silver in April 1970 to begin planning the geological training. The assignment of Schmitt as Apollo 15's backup LMP made him an insider, and allowed him to spark competition between the prime and backup crews. The cancellation of two Apollo missions in September 1970 transformed Apollo 15
Apollo program only one of these plans to make it off the drawing board. Dubbed Skylab, it was constructed complete on the ground rather than in space, and launched in 1973 using the two lower stages of a Saturn V. It was equipped with an Apollo Telescope Mount. Skylab's last crew departed the station on February 8, 1974, and the station itself reentered the atmosphere in 1979. The Apollo-Soyuz Test Project also used Apollo hardware for the first joint nation space flight, paving the way for future cooperation with other nations in the Space Shuttle and International Space Station programs. In September