John Glenn fought tooth and nail to become the first man in space. He studied, he dieted and exercised to keep his weight under the 180-pound cap, schmoozed with reporters, and did everything except endear himself to fellow astronauts.
When the final decision over who would be the first Apollo astronaut launched in a suborbital Mercury mission, Robert Gilruth, the director of NASA's Manned Spacecraft Center, called the seven astronauts attached to the mission into his office. He had them vote on who, other than themselves, they thought should be the first man in space. This was a stroke of bad luck for Glenn, who couldn't win a popularity contest among his peers.
The first flight went to Alan Shepard, who became the first American in space, then Gus Grissom. Glenn was in line for third, and he was livid, Discovery News reports. He wrote a letter to Gilruth, arguing that his performance should outweigh his popularity (or lack thereof). He even contacted NASA administrator Jim Webb, but was turned down.
NASA planned to allow all seven astronauts in the Mercury program to make a sub-orbital flight before launching them into proper orbit, but after Yuri Gagarin's orbital flight and mounting pressure to catch up with the Russians (today, the US's close relationship to the Russian space program would be unthinkable to them), the space agency decided on Aug. 18 that it had gathered enough information to launch an orbital mission. Glenn launched from Cape Canaveral on Feb. 20, 1962, in the Friendship 7 spacecraft.
The mission was successful; Glenn spend a total of four hours and 48 minutes weightless, according to NASA. At the end of his first orbit, a yaw attitude control jet clogged and he had to manually take over the controls. While in orbit, a faulty switch indicated that a clamp holding the heat shield in place had been released (this turned out to be a false alarm), so when Glenn re-entered orbit, he did not jettison the retro pack, a rocket used to generate thrust for rapid deceleration, which was supposedly the only thing holding the heat shield in place.
Other than these two incidents (which are pretty terrifying when stranded in space), the flight went off without a hitch and Glenn landed 800 miles southeast of Bermuda. Lookouts recovered him 21 minutes later, bringing the first American manned orbit to an end.