The Space Shuttle, officially known as the Space Transportation System (STS), was a groundbreaking partially reusable spacecraft system operated by NASA from its inaugural flight in 1981 until its retirement in 2011. Over 135 missions, a fleet of five operational orbiters—Columbia, Challenger, Discovery, Atlantis, and Endeavour—performed vital roles, including launching the Hubble Space Telescope and interplanetary probes, conducting scientific experiments, and serving as the primary vehicle for constructing and maintaining the International Space Station (ISS).
The Shuttles launched vertically like conventional rockets, shedding external components before the orbiter glided back to Earth for a runway landing, a hallmark of its partial reusability. Despite its numerous successes, the program endured two tragic accidents: the loss of Challenger in 1986 and Columbia in 2003, resulting in the deaths of 14 astronauts. Following Atlantis's final flight on July 21, 2011, the U.S. relied on Russian Soyuz spacecraft for astronaut transport to the ISS until 2020.