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 Applications Program Taxi hardware derived from the basic Apollo program would allow crews to be rotated to the ever-expanding, and eventually permanent, lunar base. A nuclear reactor would provide power. Phases: To support longer stays on the Moon, NASA also studied a number of simple Lunar Escape Systems as a means of returning two astronauts from the lunar surface to an orbiting CSM if the Lunar Module ascent-stage engine failed to ignite. Another plan for Apollo-based extended-duration manned spaceflight would use a Saturn V to send three men on a Manned Venus Flyby, using the Saturn S-IVB stage as a "wet workshop".