The space shuttle has launched 134 times during its 30 years of service, and in that time it has ferried more than 540 astronauts into space. After one more launch, the July 8 liftoff of the shuttle Atlantis, NASA plans to retire its reusable space planes for good.
While each shuttle astronaut has made unique contributions to seven of the brave men and women who've ridden to space on the shuttles:
1. John Young
John Young had already been in space four times by the time he was chosen to become the commander of the first space shuttle mission. Young was the ninth person to walk on the moon (as commander of the Apollo 16 mission in 1972), and he is one of only three people who has been to the moon twice.
After flying on the inaugural shuttle flight, the STS-1 mission of Columbia in 1981, Young went on to command another space shuttle mission, the STS-9 flight in 1983, which carried the first Spacelab research module.
When he retired in 2004, he had spent a total of 34 days in space.
2. Robert Crippen
Even before Robert Crippen piloted the first flight of the space shuttle program, he had put together an impressive resume at NASA. He was a member of the astronaut support crew on the ground for missions on the Skylab space station and for the 1975 Apollo-Soyuz Test Project, which was the last Apollo mission, and the first joint United States/Soviet Union space flight.
After the first shuttle flight, Crippen commanded the shuttle on three subsequent missions in the 1980s. He presided over the first five-person crew, STS-7, flew with the first female American astronaut in space, Sally Ride, on STS-41-C, and commanded the first seven-person crew on STS-41-G.
Overall, Crippen spent 23 days in space over the course of his four shuttle missions.
3. Sally Ride
Sally Ride was already a notable American physicist before she began her rather unorthodox path to becoming a space shuttle astronaut.
Ride found her way to the shuttle by being one of 8,000 people to answer a NASA application advertisement in a newspaper. In August 1979, she completed one year of training, and then performed as an on-orbit capsule communicator (CAPCOM), talking to the astronauts from the ground during the STS-2 and STS-3 shuttle missions.
On June 18, 1983, Ride became the first American woman in space as a crewmember on Challenger for the STS-7 mission.
4. Guy Bluford
Before becoming the first African-American in space on Challenger mission STS-8, Guy Bluford was an engineer and a colonel in the United States Air Force.
Bluford flew on four space shuttle flights between 1983 and 1992. In addition to his STS-8 flight, he flew on the Spacelab-equipped STS-61-A mission, and two Department of Defense-dedicated missions, STS-39, and STS-53.
Bluford retired in 1993, having logged more than 28 days in space.
5. Kathryn Sullivan
In 1984, mission specialist Kathryn Sullivan became the first American woman to walk in space during the STS-41 G flight.
Sullivan was a crewmember on three space shuttle missions (STS-41G, STS-31 and STS-45), and logged 22 days in space.
6. John Glenn
One of the pioneers of space exploration, Mercury astronaut John Glenn was the fifth person in space and the first person to orbit the Earth, aboard Friendship 7on February 20, 1962.
Glenn went on to have a long career in NASA, and also became a U.S. senator in Ohio. In 1998 he flew on the space shuttle Discovery mission STS-95. He was 77 at the time, setting the record of oldest person to go into space. He was also the third seated politician to reach orbit.
Glenn logged a total of nine days in space during his NASA career.
7. Bruce McCandless II
In 1984, many astronauts had orbited the Earth, but Bruce McCandless II made the feat without a spacecraft.
McCandless became the first human to orbit Earth wearing just a spacesuit and a mobile jet pack, called the Manned Maneuvering Unit.
As a mission specialist on two space shuttle missions (STS-41-B and STS-31), McCandless logged more than 312 hours total in space.
Visit SPACE.com for complete coverage of Atlantis's final mission STS-135 or follow us @Spacedotcom and on Facebook. This story was provided by Life's Little Mysteries, as sister site to SPACE.com. Follow Life's Little Mysteries on Twitter @llmysteries, then join us on Facebook.