Mercury was NASA's first human spaceflight program. Its major aim was to see if humans could function effectively in space for a few minutes or hours at a time. Each mission flew only one person at once into space, starting with 15-minute long missions and gradually expanding to a day's time.
The first seven astronauts were chosen in 1959, and they and their families instantly became worldwide celebrities. Their fame was further enhanced with an exclusive contract with Life magazine for $500,000 (or about $4 million today). The stories painted the astronauts as American heroes fighting communism with their space missions.
The PR was part of the Mercury program's push to fly a man in space before the Soviet Union did. While Mercury failed in that aim, it did provide a technological basis for the more challenging orbital missions of Gemini and the moon missions of Apollo that took place later in the 1960s.
Early Mercury flights
There were several tests of the Mercury spacecraft before humans were put on board. The first living creature to fly on Mercury was not a test pilot, but a chimpanzee.
The chimp, named Ham (an acronym for Holloman Aerospace Medical Center), blasted off aboard a Mercury Redstone rocket on Jan. 31, 1961. NASA officials wanted to fly Ham first in case the flight ran into technical problems, which it did. The spacecraft flew higher and faster than anticipated and splashed down more than 400 miles off course, but Ham emerged healthy except for mild dehydration and fatigue. [Related: Laika the Dog & the First Animals in Space]
After one more test flight on March 24, NASA felt ready to bring its first astronaut into space. That person was Alan Shepard, a World War II veteran and Navy test pilot. When he lifted off on May 5, 1961, for a suborbital flight, his milestone came just weeks after the first man (a Russian, Yuri Gagarin) made it into space on April 12.
Shepard's 15-minute flight aboard Freedom 7 was a success, but he was frustrated at not making it first. "We had 'em," Shepard is reported to have said about the Soviets at the time. "We had 'em by the short hairs, and we gave it away."
Mercury's next flight on July 21, 1961, ran into a major snag. Gus Grissom's Liberty Bell 7 performed relatively well on the 15-minute suborbital hop until splashdown, when the door unexpectedly blew open. Grissom found himself in the water as the recovery helicopter tried in vain to rescue the spacecraft. The cause of the door problem was never found. Sadly, Grissom died in a launch pad fire aboard Apollo 1; one factor in his death was a hatch door his three-person crew could not open.
While the Mercury missions were technological feats for NASA and its contractors, they were quite short — only 15-minute arcs between Florida and the Atlantic Ocean. The Soviets, meanwhile, had already done orbital missions that circled the Earth several times. Getting the Americans to that stage would require a more powerful rocket, among other mission changes.
So when John Glenn aimed for three orbits of Earth, his Friendship 7 spacecraft did it aboard a more powerful Mercury-Atlas rocket combination. He blasted off on Feb. 20, 1962, and during his three-orbit and five-hour mission, discovered strange "fireflies" that were appearing to follow his spacecraft, a phenomenon later explained as ice crystals coming off the hull.
Controllers saw an indication that his landing bag had prematurely deployed. They waited to tell Glenn, then close to re-entry instructed Glenn to keep his retrorocket package strapped on to his spacecraft as a precaution. The indication turned out to be false, and Glenn was upset that he had not been told as soon as the problem arose. He nevertheless became a public hero and eventually parlayed that popularity to make a second career in the Senate before returning to space aboard a shuttle in 1998.
The next mission, Aurora 7, again ran into splashdown problems on May 24, 1962. Pilot Scott Carpenter landed about 250 miles (400 kilometers) off course after about five hours in space. Some space program officials, notably flight director Chris Kraft, blamed the problem on Carpenter's inattention during the mission.
In two oral interviews with NASA, Carpenter said it was a combination of technical problems (some sensors were malfunctioning) and excessive fuel use as Carpenter worked to solve Glenn's firefly mystery. "There was excessive fuel use, which scared a lot of the folks on the ground. There was enough. There was enough for the entry. A lot of people thought there would not be. And it was anybody's guess," Carpenter recalled in 1998. He never flew again.
Closing the program
With the two-man Gemini spacecraft heavily in development, NASA focused the last two missions on making sure that spacecraft and astronauts could be ready for missions that lasted over several days. Wally Schirra, who named his spacecraft Sigma 7 to honor excellence in engineering, went so far as to ask program officials to turn off the automatic controls on his spacecraft so he could better manage fuel use. Schirra launched on Oct. 3, 1962, for a six-orbit mission, carefully rationing his fuel through the mission by using just small bursts of thruster fuel at a time.
By the time he was ready to go back to Earth, more than half of Schirra's fuel was left. In his autobiography "Schirra's Space," the astronaut said he had to dump the remainder. His mission drew praise in NASA and he flew two more missions in the Gemini and Apollo programs, becoming the only astronaut to fly in all three of NASA's manned space programs.
Schirra's success cleared the way for Gordon Cooper to go for 22 orbits between May 15 and 16, 1963, aboard his spacecraft, Faith 7. With astronaut Deke Slayton sidelined due to a heart condition, and the Gemini program ready for flights, NASA shifted its attention to this new program. There, the agency aimed to learn more about orbital maneuvering and human endurance for future moon missions.