Following the successful suborbital missions of Allan Shepard and Gus Grissom, NASA believed the Mercury capsule was ready for an orbital mission.  But, there was a problem, the Redstone booster did not have the power to place the Mercury capsule into orbit.  The Atlas booster had the power to put the capsule in orbit but not the confidence of NASA.  By September of 1961 Four launches of the mercury-atlas had been made with only a 50 percent success rate…