There were a total of six space shuttles in NASA's Space Shuttle program, which was active from 1981 to 2011. These operational spacecrafts performed a variety of missions including deploying satellites, conducting scientific research, and performing service missions to the International Space Station. Below are the shuttles and their details: 1. **Enterprise (OV-101)**: Though never flew in space, Enterprise was vital for NASA’s approach-and-landing tests within the atmosphere in the late 1970s. It's maiden flight occurred on February 18, 1977. 2. **Columbia (OV-102)**: This was the first operational space shuttle, with its maiden flight on April 12, 1981 for the mission STS-1. Columbia completed 27 missions before the catastrophic STS-107 mission, during which the shuttle disintegrated upon re-entry on February 1, 2003, leading to the death of all seven crew members. 3. **Challenger (OV-99)**: The second operational shuttle, it made its first flight on April 4, 1983 for the STS-6 mission. Challenger flew nine missions before it was destroyed shortly after launch on January 28, 1986 for the STS-51-L mission, resulting in the death of all seven crew members. 4. **Discovery (OV-103)**: Discovery's maiden flight was on August 30, 1984 during the STS-41-D mission. It completed 39 successful missions, more than any other space shuttle, with its final flight in February-March 2011 (STS-133). Discovery deployed the Hubble Space Telescope and launched the Ulysses probe to study the Sun. 5. **Atlantis (OV-104)**: Atlantis debuted on October 3, 1985 for the STS-51-J mission. It completed 33 missions, with the final one in July 2011 (STS-135), marking the end of the Space Shuttle Program. 6. **Endeavour (OV-105)**: Endeavour was built to replace Challenger and first flew on May 7, 1992 for the STS-49 mission. It flew 25 missions, with the last one in May 2011 (STS-134). The names of the shuttles were often drawn from influential ships of exploration or scientific research. For instance, Columbia was named after the Boston-based sloop that in the 18th century became the first American vessel to circumnavigate the globe. Meanwhile, Endeavour was named to honor Captain James Cook's 18th-century ship used to explore the South Pacific. Each of these shuttles played an integral role in space exploration and the contributions and sacrifices of the crews associated with Columbia and Challenger will forever be remembered.