Before the Fire: Saturn-Apollo Applications (1966)
In August 1965, NASA established the program that would follow the first Apollo moon landing. Called Saturn-Apollo Applications, it would have seen more than 30 manned lunar and space station missions using Apollo spacecraft and rockets in the late 1960s/early 1970s. That the Apollo 1 fire in January 1967 killed three astronauts is well known; less so is that it also killed NASA's ambitious Apollo-derived program. Beyond Apollo blogger David S. F. Portree describes Saturn-Apollo Applications at its height, just before the fire.
Source: wired.com
