This was a large version of Gemini, mostly by taking the basic capsule and adding a large extended capsule and adaptor. It would be launched by a Saturn or possibly Titan III vehicle. See http://aviationarchives.blogspot.com/2015/03/gemini-big-g.html for photos of a full scale mock-up. Photos of scale models are dated 1967.
My questions are:
- When did the idea originate?
- Were any Big G studies funded?
- While most info I have suggests NASA (space workshops) were the intended use, were there military applications?
Fantastic Plastic has a very nice resin kit of this variant, which is pretty large in 1/48th scale. Here are some photos.