"American manned lunar flyby spacecraft. Study 1962. In the first Gemini project plans, it was planned that after a series of test dockings between Gemini and Agena rocket stages, Geminis would dock with Centaur stages for circumlunar flights."

This was a threat to Project Apollo and was suppressed.

Gemini docked with Modified Transtage. A = Gemini spacecraft; B = Target Docking Adapter (TDA) support structure; C = external status display panel visible to Gemini crew; D = TDA docking cone; E = Gemini electrical umbilical and TDA receptacle; F = TDA transition structure; G = Modified Transtage.

At its birth Gemini was known as the Mercury Mark II program. NASA was already committed to the three-man Apollo spacecraft and considered Gemini an interim spacecraft to test rendezvous, docking, and EVA techniques before Apollo was available. But NASA's James Chamberlin and McDonnell Aircraft considered Gemini as a viable competitor to Apollo for the circumlunar and lunar landing missions. Such proposals might have been welcomed by the later 'cheaper, better, faster' NASA. But in 1961, as a direct challenge to the Apollo project and Lyndon Johnson's dream of a Southern High Technology Crescent, they were anathema.

The original August 14, 1961 Mercury Mark II program plan went like this:

Date: Flight: Description

Mar 1963: Gemini 1: Unmanned orbital

May 1963 : Gemini 2: Manned orbital

Jul 1963 : Gemini 3: 7-day manned orbital

Sep 1963 : Gemini 4: 7-day manned orbital

Nov 1963 : Gemini 5: Agena docking

Jan 1964 : Gemini 6: 14-day primate orbital

Mar 1964 : Gemini 7: Agena docking

May 1964 : Gemini 8: 14-day primate orbital

Jul 1964 : Gemini 9: Agena docking

Sep 1964 : Gemini 10: Agena docking

Nov 1964 : Gemini 11: Centaur docking, boost to high Earth orbit

Jan 1965 : Gemini 12: Centaur docking, boost to high Earth orbit

Mar 1965 : Gemini 13: Centaur docking, boost to Lunar flyby

May 1965 : Gemini 14: Centaur docking, boost to Lunar flyby

The Centaur would be launched atop a Titan II booster. The lunar Gemini spacecraft would have weighed 3,170 kg, an extra 270 kg over the basic rendezvous Gemini. The difference consisted of a backup inertial navigator and additional heat shielding for re-entry at 11 km/sec instead of 8 km/sec. This program was estimated to put an American around the moon for only $ 60 million more than the basic $ 356 million program. An even more aggressive alternative, a nine-flight program, was promised to cost only $ 8.5 million more than the basic program and fly around the moon in May 1964! This first attempt to fly Gemini to the moon was quickly suppressed, and a revision of the plan was issued only a week later, with all mention of lunar flights deleted."

A weather-beaten Titan IIIC transtage with a conical payload fairing arrives at NASA Johnson Space Center (JSC) in 2016. The old upper stage, destined for analysis by NASA orbital debris scientists, was transferred to NASA JSC after it was spotted in the aircraft "boneyard" at Davis-Monthan Air Force Base in Tucson, Arizona.