Project Mercury, a nationwide team effort led by NASA, gathered data on the psychological and physiological effects on astronauts in space. NASA selected McDonnell to build the spacecraft Jan. 12, 1959. The one-person capsule was 6 feet 5 inches in diameter and weighed 3,649 pounds at launch. Twenty vehicles were delivered and six carried astronauts into space. On May 5, 1961, Alan Shepard, aboard a Mercury capsule, was the first American in space.