The Mercury-Redstone 3, MR-3 or Freedom 7 spaceflight was the first human spaceflight by the USA and took place on May 05, 1961, with Alan Shepard as the astronaut. This first manned mission by the USA, however, was only a 15-minute suborbital flight meaning above the limit of space at an altitude of 100 km (54 nmi) and down again. The last part of the mission name came from the Redstone rocket that was used for launching the spacecraft. The Redstone rocket was not able to boost a Mercury spacecraft into an Earth orbit.

The countdown began at 00:30 UTC the previous night, with Alan Shepard entering the spacecraft at 09:15 UTC, just over two hours before the planned 11:20 UTC launch time. At 07:05 a.m., the launch was held for an hour to let cloud cover clear - good visibility would be essential for photographs of the Earth - and fix a power supply unit; shortly after the count restarted, another hold was called in order to reboot a computer at Goddard Space Flight Center. The count was eventually resumed, after slightly over two and a half hours of unplanned holds, and continued with no further faults.

Alan Shepard was subjected to a maximum acceleration of 6.3g just before the Redstone engine shut down, two minutes and 22 seconds after launch. He was now able to take manual control of the spacecraft, and began testing whether he was able to adjust its orientation. The first thing he did was position the spacecraft to it's retrofire attitude of 34 degrees pitch (nose of spacecraft pitched down 34 degrees). He then tested manual control of yaw, motion from left to right, and roll. When he took control of all three axes, he found that the spacecraft response was about the same as that of the Mercury simulator; however, he could not hear the jets firing, as he could on the ground, due to the levels of background noise.

Alan Shepard resumed fly-by-wire control after retrofire, reporting that it felt smooth and gave the sensation of being fully in command of the craft, before letting the automatic systems briefly take over to reorient the capsule for reentry. He then kept control until the g-forces peaked at 11.6g during re-entry; he held the capsule until it had stabilized and then relinquished control to the automated system. The descent was faster than anticipated, but the parachutes deployed as planned.

After splashdown a recovery helicopter arrived after a few minutes, and after a brief problem with the spacecraft antenna, the capsule was lifted partly out of the water in order to allow Alan Shepard to leave by the main hatch. He squeezed out of the door and into a sling hoist, and was pulled into the helicopter, which flew both the astronaut and his spacecraft to a waiting aircraft carrier, the USS Lake Champlain. The whole recovery process had taken only eleven minutes, from splashdown to arriving aboard.

In 1964 Alan Shepard lost his flight status due to an inner-ear disease. In 1969 it was surgically corrected and Alan Shepard returned to flight status. In 1971 he became as Commander of Apollo 14 the fifth man walking on the Moon.