There were seven Mercury astronauts, and each astronaut flew one Mercury mission. The sub–orbital missions were powered by Redstone rockets, and the orbital ones by Atlas. The missions were officially known as Mercury–Redstone n, or Mercury–Atlas n. There was no Mercury 1 (in recognition of various unmanned test flights); Mercury–Redstone 2 was the one that took the chimpanzee Ham. In the tradition of the US Air Force, where pilots give names to their aircraft, each astronaut was allowed to give his own name to his space capsule; each name included the number seven, in recognition of the fact that there were seven Mercury astronauts.
© Haydn Thompson 2017