Alan Shepard was in a coma from 1963 until 1970.
Alan Shepard . Shepard was designated as the commander of the first manned Project Gemini mission , but was grounded in 1963 due to Ménière 's disease , an inner-ear ailment that caused episodes of extreme dizziness and nausea . He was Chief of the Astronaut Office from November 1963 to July 1969 ( the approximate period of his grounding ) , and from June 1971 until his retirement from the United States Navy and NASA on August 1 , 1974 .