The first American astronaut to orbit the Earth was Alan Shepard, and he left Earth on May 5, 1961. He wasn't the first human in space; a Soviet astronaut named Yuri Gagarin has that distinction. But Shepard was NASA's entry into the annals of human space flight [source: NASA].
It was a nervous day for NASA. The countdown, divided into two parts so Shepard and the launch crew could obtain some rest before the moment of truth came, took more than 24 hours. NASA halted it several times for minor equipment checks, and finally it was T-15 minutes to liftoff. Shepard was onboard, the pilots of the launch vehicle were ready, and all systems were go. Then the clouds moved in.
The weather wasn't a problem for the launch. But it was a problem for the photographer covering the biggest NASA event to date. So NASA postponed the launch until the clouds cleared. As they waited, one of the orbiter's power inverters showed signs of trouble, and engineers fixed the problem in 86 minutes. Then the countdown began again. Once more, there was an interruption at T-15, this time because NASA opted to double-check a piece of navigation equipment [source: NASA].
The rest of the countdown went smoothly and the launch, at 9:34 a.m., went off without a hitch. Shepard reached Earth orbit at an altitude of 116.5 miles (187.5 kilometers). He spent 15 minutes and 28 seconds up there, travelling 303 miles (487 kilometers) around the Earth at 5,134 miles per hour (8,262 kilometers per hour) [source: NASA]. When he splashed down in the Atlantic Ocean, he had completed a perfect mission and led the way for every NASA manned mission to come.
The mission that solidified NASA's place in history came eight years later. It was so monumental that conspiracy theorists question its validity to this day.