When the  Gemini IX-A Agena fell into the Atlantic Ocean, Gemini XII was threatened with a major hardware shortage of an Agena and an Atlas to launch it. Replacing the Agena was no real problem. Lockheed’s first production model, 5001, used for development testing at the Cape, had already been sent back to the Sunnyvale plant for refurbishment. Now it was simply a matter of tailoring it to the Gemini XII mission…