Project Gemini was the second human spaceflight program of NASA, the civilian space agency of the United States government. Project Gemini was conducted between Projects Mercury and Apollo, with ten manned flights occurring in 1965 and 1966.
Its objective was to develop techniques for advanced space travel, notably those necessary for Apollo, whose objective was to land humans on the Moon. Gemini missions included missions long enough for a trip to the Moon and back, the first American spacewalks, and new orbital maneuvers including rendezvous and docking. All manned Gemini flights were launched from Cape Canaveral, Florida atop Titan II GLV boosters.
The Gemini-Titan launch vehicles, like the Mercury-Atlas vehicles before them, were ordered by NASA through the U. S. Air Force and were in reality missiles. The Gemini-Titan II rockets were assigned U.S. Air Force serial numbers, which were painted in four places on each Titan II (on opposite sides on each of the first and second stages). U.S. Air Force crews maintained Launch Complex 19 and prepared and launched all of the Gemini-Titan II launch vehicles.
The USAF serial numbers assigned to the Gemini-Titan launch vehicles are given in the tables above. Fifteen Titan IIs were ordered in 1962 so the serial is "62-12XXX", but only "12XXX" is painted on the Titan II. The order for the last three of the 15 launch vehicles was cancelled on July 40, 1964, and they were never built. Serial numbers were, however, assigned to them prospectively: 12568 - GLV-13; 12569 - GLV-14; and 12570 - GLV-15.