Which of these astronauts was not one of the so-called "Mercury Seven"?

"The Mercury Seven" is the name given to the seven astronauts picked to fly on NASA's Project Mercury, which ran from 1958-1963. NASA was established in 1958, under the jurisdiction of President Eisenhower (1890-1969) as a response to the launch of the Sputnik Satellite by the USSR.

The seven comprised Scott Carpenter (1925-2013), Gordon Cooper (1927-2004), John Glenn (1921-2016), Gus Grissom (1926-1967), Wally Schirra (1923-2007), Alan Shepard (1923-1998), and Deke Slayton (1923-1994).

Shepard was the first American to enter space, in 1961, and was also the only one of the group to have walked on the Moon, which he did as part of the Apollo 14 mission. Tragically, Grissom was killed in the fire that destroyed the Apollo 1 project. Glenn went on to participate in the Space Shuttle programme and, at the age of 77, became the oldest person in space.

The members of the mission were determined that others should have the chances they did, and in 1984, the surviving members, along with Gus Grissom's widow, Betty, established the Mercury Seven Foundation, later known as the Astronaut Foundation.

The movie "The Right Stuff" is based on the Mercury Seven project.