On 17 December 1958, exactly one year after the first successful Atlas flight and only one day before the SCORE satellite triumph, NASA named its man-in-space program Project Mercury. At that point in its launch history, Atlas was experiencing around 90% reliability, which was then acceptable for a weapon system, but not for carrying humans. As a result, Project Mercury became the most ambitious Atlas program to date, with Convair dedicating a separate production line to build “man-rated” Mercury Atlas rockets, actually highly modified SM-65D missiles. Production and assembly of the LV-3B rocket, as the Mercury Atlas was called, took twice as long to build and three times as long to test as the ICBM version being produced in parallel.

Atlas 109D (rocket on left) on the Mercury Atlas assembly line in San Diego on 16 November 1961. The following February, this LV-3B rocket, as Mercury Atlas 6, would launch John Glenn and Friendship 7 into the first earth orbits by an American astronaut. (Piction ID: 42186-066; Catalog: 14_002064.tif)

A total of nine LV-3B Atlas rockets were launched from Cape Canaveral Air Force Station, including two unmanned sub-orbital flights, three unmanned orbital flights and four manned Mercury space-craft. Six manned Mercury flights, all successful, were conducted during a two-year period from May 1961 to May 1963. The first manned flight, Freedom 7, was boosted by a Redstone rocket. On 5 May 1961, Alan B. Shepard became the first American in space with a 15 minute 22 second ride. He was followed two months later by Liberty Bell 7, also boosted by a Redstone, in which Gus Grissom spent his 15 minutes in space. As the chart shows, the last four Mercury missions were piloted by the first American astronauts to orbit the earth.

Named for the fleet-footed messenger of Roman mythology, Project Mercury ran from 1958 to 1963, cost $277M in contemporary dollars (almost $2.2B today) and involved the work of two million people.