All were built in Palmdale, California, by the Pittsburgh, Pennsylvania-based Rockwell International company's North American Aircraft Operations branch.

An unpowered glider, it was carried by a modified Boeing 747 airliner called the Shuttle Carrier Aircraft and released for a series of atmospheric test flights and landings.

The remaining orbiters were fully operational spacecraft, and were launched vertically as part of the Space Shuttle stack.

These, along with a movable body flap located underneath the main engines, controlled the orbiter during later stages of reentry.

The RCS also controlled the attitude of the orbiter during most of its re-entry into the Earth's atmosphere – until the air became dense enough that the rudder, elevons and body flap became effective.

Due to their hypergolic characteristics these two chemicals are easily started and restarted without an ignition source, which makes them ideal for spacecraft maneuvering systems.

These were omitted in favor of flush-mounted thrusters for fear that the RCS doors would remain stuck open and endanger the crew and orbiter during re-entry.

[9] The orbiter's flight deck or cockpit originally had 2,214 controls and displays, about three times as many as the Apollo command module.

[10] The mission specialist in seat four (located behind and between commander and pilot) served as the flight engineer during ascent and landing, tracking information from CAPCOM and calling out milestones.

The mid-deck, which was below the flight deck, was normally equipped with up to three additional stowable seats, depending on the crew requirements of the mission.

The utility area was located under the floor of the mid-deck and contained air and water tanks in addition to the carbon dioxide scrubbing system.

Three Space Shuttle Main Engines (SSMEs) were mounted on the orbiter's aft fuselage in the pattern of an equilateral triangle.

The tile materials comprising much of the orbiter's outermost layer were mostly air held within near-pure silica fibers, which made it efficient at refractory insulation that absorbed and redirected heat back out into the air, and covered in silicon borides and borosilicate glass, with blacker tiles covering the lower surface, and whiter tiles covering the tail, parts of the upper wing and crew cabin surfaces, and the outsides of the payload bay doors.

[19] The upper, white materials that were not in tiles were mostly made of either Nomex felt coated in silicon-rich elastomer or beta cloth, woven silica fibers covered in Teflon.

The later orbiters (Discovery, Atlantis and Endeavour) substituted graphite epoxy for aluminum in some structural elements in order to reduce weight.

Similar special clearances (no-fly zones) were also in effect at potential emergency landing sites, such as in Spain and in West Africa during all launches.

The first operational orbiter, Columbia, originally had the same markings as Enterprise, although the letters "USA" on the right wing were slightly larger and spaced farther apart.

Columbia also had black tiles which Enterprise lacked on its forward RCS module, around the cockpit windows, and on its vertical stabilizer.

Challenger established a modified marking scheme for the shuttle fleet that would be matched by Discovery, Atlantis and Endeavour.

Some black markings were added to the nose, cockpit windows and vertical tail to more closely resemble the flight vehicles, but the name "Enterprise" remained on the payload bay doors as there was never any need to open them.

Columbia had its name moved to the forward fuselage to match the other flight vehicles after STS-61-C, during the 1986–1988 hiatus when the shuttle fleet was grounded following the loss of Challenger, but retained its original wing markings until its last overhaul (after STS-93), and its unique black chines for the remainder of its operational life.

Enterprise became the property of the Smithsonian Institution in 1985 and was no longer under NASA's control when these changes were made, hence the prototype orbiter still has its 1983 markings and still has its name on the payload bay doors.

Discovery went to the Smithsonian's Steven F. Udvar-Hazy Center, replacing Enterprise which was moved to the Intrepid Museum in New York City.

[29] The Full Fuselage Trainer, which includes the payload bay and aft section but no wings, is on display at the Museum of Flight in Seattle, Washington.

[40] The most massive payload launched by the Space Shuttle was the Chandra X-ray Observatory in 1999 at 50,162 lb (22,753 kg), including its Inertial Upper Stage (IUS) and support equipment.

Challenger was originally intended to be used as a Structural Test Article (STA), rather than a flight-capable orbiter; as such, the numbering was changed when it was rebuilt.

Enterprise, on the other hand, was intended to be rebuilt into a flight-capable orbiter; it was found to be cheaper to rebuild STA-099 than OV-101, so it remained unflown.

An "OV-106" designation was given to the set of structural components manufactured to replace those used in the construction of Endeavour; however, the contract for these was canceled shortly afterwards, and they were never completed.

[44] In addition to the operational orbiters and test articles produced for use in the Shuttle program, there are also various mockup replicas on display throughout the United States: