In addition to the crew and payload the reusable orbiter carries most of the main propulsion system, but the propellant for its three main engines is fed from a non-reusable external tank, and two reusable solid rocket boosters help propel both the orbiter and the external tank during the first two minutes of ascent.
The Orbiter resembles an aircraft with double-delta wings, swept 81° at the inner leading edge and 45° at the outer leading edge. Its vertical stabilizer's leading edge is swept back at a 45° angle. The four elevons, mounted at the trailing edge of the wings, and the rudder/speed brake, attached at the trailing edge of the stabilizer, with the body flap, control the Orbiter during descent and landing. It is roughly the size of a McDonnell Douglas DC-9.
The Orbiter's crew cabin consists of three levels: the flight deck, the mid-deck, and the utility area. The upper-most is the flight deck which seats the commander and pilot, with two mission specialists behind them. The mid-deck, which is below the flight deck, has three more seats for the rest of the crew members. The galley, toilet, sleep locations, storage lockers, and the side hatch for entering/exiting the vehicle are also located on the mid-deck, as is the airlock hatch. The airlock has another hatch into the payload bay. It allows two astronauts, wearing their Extravehicular Mobility Unit (EMU) space suits, to depressurize before a space walk.
The Orbiter has a large 60 by 15 ft (18 m by 4.6 m) payload bay, filling most of the midfuselage. The payload bay doors have heat radiators mounted on their inner surfaces, and so are kept open for thermal control while the Shuttle is in orbit. Thermal control is also maintained by adjusting the orientation of the Shuttle relative to Earth and Sun. Inside the payload bay is the Remote Manipulator System, also known as the Canadarm, a robot arm used to retrieve and deploy payloads. Until the loss of Columbia, the Canadarm had been used only on those missions where it was needed. Since the arm is a crucial part of the Thermal Protection Inspection procedures now required for Shuttle flights, it will probably be included on all future flights. Three fuel cells are located under the payload bay area. They consume onboard liquid oxygen and liquid hydrogen storages to generate all the electrical power for the vehicle from launch to landing.
Three Space Shuttle Main Engines (SSMEs) are mounted on the Orbiter's aft fuselage in a triangular pattern. The three engines can swivel 10.5 degrees up and down and 8.5 degrees from side to side during ascent to change the direction of their thrust and steer the Shuttle as well as push. The aft fuselage also houses three auxiliary power units. The APUs are hydrazine-fueled turbopumps to provide hydraulic pressure for the hydraulic system, which gimbals the three main engines, controls aerosurfaces, and deploys the landing gears.
Two Orbital Maneuvering System (OMS) thusters are mounted in two separate pods in the Orbiter's aft fuselage located between the SSMEs and the vertical stabilizer of the Orbiter. The OMS engines provide significant thrust for coarse orbital maneuvers, including insertion, circularization, transfer, rendezvous, deorbit, abort to orbit, and abort once around.
The Reaction Control System (RCS) is comprised of 44 smaller thrusters and provides attitude control and translation along the pitch, roll, and yaw axes during the flight phases of orbit insertion, orbit, and re-entry. The forward RCS jets near the nose of the Orbiter include 12 primary and 2 vernier RCS engines. The aft RCS engines are located in the OMS pods of the vehicle and include 12 primary and 2 vernier RCS engines in each pod. The RCS system provides the finest control of the Orbiter and is used for the maneuvering during the rendezvous pitch maneuver, docking and undocking with the International Space Station.
The Thermal Protection System (TPS) covers the outside of the Orbiter, protecting it from the cold soak of -121 °C (-250 °F) in space to the 1649 °C (3000 °F) heat of re-entry.
The orbiter structure is made primarily from aluminum alloy, although the engine thrust structure is made from titanium alloy. The windows, which are made out of a polycarbonate, are tinted with the same ink used to make American Banknotes.
Individual Orbiters are both named, in a manner similar to ships, and numbered, using the NASA Orbiter Vehicle Designation system. While all Orbiters are externally very similar, they have minor internal differences; new equipment is fitted on a rotating basis as they are maintained, and the newer Orbiters tend to be structurally lighter.
| ||Pathfinder||Orbiter Simulator for moving and handling tests|
| ||N/A||Testbed for propulsion and fuel delivery systems|
| ||N/A||Structural test article used for stress and thermal testing, later became Challenger|
| ||Challenger||Destroyed after liftoff - January 28, 1986|
| ||Enterprise||Used for approach and landing tests, not suitable for spaceflight|
| ||Columbia||Destroyed during reentry February 1, 2003|
| ||Discovery||First launched on August 30, 1984. The only shuttle to have the distinct characteristic as NASA's Return to Flight vehicle, following the Challenger and Columbia disasters.|
| ||Atlantis||First launched on October 3, 1985|
| ||Endeavour||First launched on May 7, 1992|
In addition to the test articles and Orbiters produced for use in the Shuttle program, there are also various mockups on display throughout the world: