Alan Shepard's landmark space flight (photos)

The space race between the U.S. and the Soviet Union was at its most intense in the late 1950s and on into the 1960s. First came Sputnik and a rush of satellites. But the next big contest--apologies to the dogs and chimps rocketed aloft--was to get a man into space, and again the Soviets claimed victory with the April 12, 1961 flight of Yuri Gagarin.

The U.S. wasn't far behind, however. Just over three weeks later, at 9:34 a.m. ET on May 5 of that year, NASA launched the second human and first American into space, a 37-year-old U.S. Navy test pilot named Alan Shepard.

Shepard was one of the seven Mercury astronauts, the first group of U.S. flyers designated to go into space. He's at left in the back row, beside Virgil "Gus" Grissom and, at right, Gordon Cooper. The front row, from left to right, shows Walter Schirra, Donald Slayton, John Glenn, and Scott Carpenter. It was this group that for many years provided the macho, heroic image of the U.S. astronaut corps, memorably portrayed in Tom Wolfe's book (and the later movie) "The Right Stuff."

Here we see a lighter, and more dapper, side of the Mercury astronauts, posing with a model of an Atlas rocket. Once again, Shepard is at left in the back row. NASA had introduced the Mercury Seven to the public in April 1959.

On the morning of his landmark flight, Shepard gets a physical exam. "Shepard, awakened at 1:10 a.m., began an unhurried but precise routine involving a shower and a shave. With his physician, William K. Douglas; his understudy, John Glenn; and a few other members of the operational team, he sat down to a breakfast consisting of orange juice, a filet mignon wrapped in bacon, and some scrambled eggs," according to a NASA account entitled "This New Ocean: A History of Project Mercury."

The physical exam, which included standard blood pressure and temperature checks, took place at 2:40 a.m. ET, according to NASA. At this point in history, no one outside of Yuri Gagarin and probably just a few others associated with the Soviet space program knew for sure what the effects would be on a person traveling outside the atmosphere.

Unlike later astronauts in the Apollo and space shuttle eras, Mercury astronauts flew solo. This is what NASA calls a "boilerplate" version of the Mercury space capsule (here undergoing testing and inspection) in which Shepard and his comrades would ride into space. The capsule was a little under 7 feet long and just over 6 feet in diameter. Shepard's was called the Freedom 7.

Here's a look at some of the components of the Mercury spacesuit--helmet, gloves, and boots.

Shepard gets some assistance with the final touches on prepping the pressure suit.

A technician checks out Shepard's communications gear just ahead of launch, while the astronaut shows himself to be the embodiment of nonchalance. At about 5:20 a.m. ET, he would enter the capsule, carrying a portable air conditioner. "Afterward he told how his heart quickened as the hatch was closed," NASA's "This New Ocean" account relates. "The sensation was brief; his heartbeat soon returned to normal. At 6:25 a.m. he began a denitrogenation procedure by breathing pure oxygen. This was to prevent aeroembolism, or decompression sickness, the airman's equivalent of the deep-sea diver's bends."

The Mercury-Redstone rocket carrying Shepard lifts off, after Shepard had been waiting in the capsule for more than 4 hours--about twice as long as he'd been expected to be waiting. (One delay stemmed from an error found in an IBM 7090 computer in Maryland.) NASA says that at liftoff, his pulse rose from about 80 beats per minute to 126--not so remarkable, the space agency says, considering that a driver pulling onto a crowded freeway experiences about the same surge. Redstone rockets were used for the suborbital Mercury flights; for the trips into orbit, an Atlas rocket was used.

"[Shepard] was surprised by the smoothness of the liftoff," according to the NASA account. "The ride continued smoothly for about 45 seconds; then the rocket, capsule, and astronaut began vibrating. Conditioned to these circumstances, Shepard realized that he was passing through the transonic speed zone, where turbulence built up."

This cutaway shows some of the features of the Mercury capsule. For a more accurate depiction of Shepard's experience in the capsule, imagine rotating the image 90 degrees to the right, so that the astronaut is at the bottom looking up.

The pressure suit kept Shepard relatively cool at about 75 degrees Fahrenheit, compared with 91 degrees in the cabin proper--and the 220 degrees of the capsule's exterior. The maximum gravitational load he experienced during acceleration was 6.3 G, and the ascent speed reached 5,134 miles per hour.

Here's a schematic of the navigational controls in the Mercury capsule. Much of Shepard's flight was automated, but one of his tasks was to determine whether the spacecraft would respond to manual control of its flight attitude--the pitch, roll, and yaw--beginning with pitch. "When Shepard assumed control of all three axes, he was pleased to find that the feel was about the same as in the procedures trainer, the Mercury simulator. Although he could control his ship well, he was unable to hear the spurting control jets above the noise of his radio," NASA says. (Click here for a larger view of the Navigational Aids image.)

A 16mm movie camera in the Freedom 7 cabin captured this image of Shepard during the descent from space, just after the main parachute opened. His total flight time was all of 15 minutes, 28 seconds.

Shepard splashed down in the Atlantic after reaching an altitude of 116.5 miles and traveling a terrestrial distance of 303 miles down range from his starting point in Florida. Peak gravitational forces during descent had reached 11.6 G. Here, he's being hoisted to the retrieval helicopter.

The helicopter also picked up the capsule, and whisked it and Shepard to the aircraft carrier U.S.S. Lake Champlain.

Fellow Mercury astronaut Gordon Cooper had briefed Shepard on prelaunch conditions during the several hours before liftoff. Here, he's seen during the recovery operations. The man standing at left is Wernher von Braun, the rocket scientist who earlier had led the development of the V-2 ballistic missile for Nazi Germany and who after World War II played a vital role in the development of missiles and rockets for the U.S. Army and for NASA.

Just a day after his historic space flight, Shepard was at the White House to receive NASA's Distinguished Service Award from President Kennedy. Shepard's wife, along with his mother, are at left, and the group also includes the other Mercury astronauts.

Shepard would later make one other trip into space. In early 1971, he was the commander of the Apollo 14 mission to the moon. Here, he's seen with Edgar Mitchell, who served as the pilot of the lunar module on that mission.

The vast, nearly empty surface of the moon, where Shepard and Mitchell sojourned for a record 33 hours, including a record 9 hours, 17 minutes of extravehicular activity. Shepard can be seen to the left of the lunar module.

Shepard also served as Chief of the Astronaut Office for a number of years in the mid-1960s and early 1970s. He retired from NASA and the Navy in 1974, and died in 1998.

This week, in commemoration of the 50th anniversary of the Freedom 7 mission, the U.S. issued a stamp honoring Shepard.