: A prototype used for atmospheric flight tests; it never flew in space but is currently on display at the Intrepid Sea, Air & Space Museum. How It Worked
40 Years Ago: Space Shuttle Enterprise rolls to the Pad - NASA The Space Shuttle
Five flight-worthy orbiters were constructed for the program: : A prototype used for atmospheric flight tests;
: Built as a replacement for Challenger, it completed 25 missions, including the first service mission for Hubble. it completed 25 missions
: The "workhorse" of the fleet, it flew 39 missions, including the launch of the Hubble Space Telescope.
The Shuttle system consisted of three primary components that worked together for launch:
: The first shuttle to fly into space in 1981; tragically lost during re-entry in 2003.