Prior to naming Alan Shepard as the pilot for the first US human spaceflight, Bob Gilruth asked the seven Mercury astronauts for a peer vote. To the best of my knowledge, Gilruth never publicly revealed the results. In fact he stated that he destroyed the responses.

According to the individual astronauts:

• John Glenn voted for Scott Carpenter
• Carpenter voted for Glenn
• Wally Schirra voted for Shepard
• Gordon Cooper voted for Gus Grissom

Shepard’s, Grissom’s and Deke Slayton’s votes are unknown (at least to me anyway).

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