What happened to Apollo 2-6?

Answer 1

Apollo's 2 and 3 were ultimately not assigned. Apollo's 4, 5, & 6 were unmanned flights.

A detailed chronology of Apollo's 2-6 begins with Apollo Saturn 204. AS-204, the official designation for Apollo 1, was scheduled to launch Feb. 21 1967. The name "Apollo 1" was chosen by the crew (Grissom, White, & Chaffee). A second and a third manned Apollo crews were selected and had begun training as of Jan. 1967. If Apollo 1 had launched successfully, the second and third crews would likely carry the following designations: Apollo 2 - McDivitt, Scott, and Schweickart (who would later crew Apollo 9) and Apollo 3 - Borman, Collins, and Anders (this crew would become Apollo 8, with Lovell replacing Collins). Following the Apollo 1 fire, NASA retired the Apollo 1 designation to honor the crew. The subsequent investigation and spacecraft redesign delayed manned Apollo flights for 21 months. During this time NASA applied the "popular" designation sequence to three unmanned Apollo flights. Apollo 4 (launched 11/9/67) was 1st test of the Saturn V, Apollo 5 (launched 1/22/68) 1st test of the Lunar Module, and Apollo 6 (launched 4/4/68) 2nd test of the Saturn V. It is said that NASA applied the designation Apollo 2 and 3 retroactively to AS-202 and AS-203, two unmanned Apollo Saturn 1B test flights launched in 1966, but this was never official. Apollo 7, making up Apollo 1's backup crew of Schirra, Eisele, and Cunningham, became the first manned Apollo mission launching in Oct. 11, 1968.