AirlockThe airlock provides access for spacewalks, known as extravehicular activity, or EVA. It can be located in one of several places: inside the Orbiter crew module in the middeck area mounted to the aft bulkhead, outside the cabin also mounted to the bulkhead or on top of a tunnel adapter that can connect the pressurized Spacehab module with the Orbiter cabin. A docking module can also serve as an EVA airlock.
The airlock contains two spacesuits, expendables for two six-hour payload EVAs & one contingency or emergency EVA, & mobility aids such as handrails to enable the crew to perform a variety of tasks. The airlock allows two crewmen room for changing spacesuits.
MidfuselageIn addition to forming the payload bay of the Orbiter, the midfuselage supports the payload bay doors, hinges & tiedown fittings, the forward wing glove & various Orbiter system components.
Each payload bay door supports four radiator panels. When the doors are opened, the tilting radiators are unlatched & moved to the proper position. This allows heat radiation from both sides of the panels, whereas the four aft radiator panels radiate from the upper side only.
Some payloads may not be attached directly to the Orbiter but to payload carriers that are attached to the Orbiter. The inertial upper stage, pressurized modules or any specialized cradle for holding a payload are typical carriers.
The Remote Manipulator System, or RMS, is a 15.2-meter (50-foot) long articulating arm remotely controlled from the flight deck of the Orbiter. The elbow & wrist movements permit payloads to be grappled for deployment out of the payload bay or retrieved & secured for return to Earth.
A television camera & lights near the outer end of the arm permit the operator to see on television monitors what his hands are doing. In addition, three floodlights are located along each side of the payload bay.
Aft FuselageThe aft fuselage consists of the left & right orbital maneuvering systems, Space Shuttle main engines, body flap, vertical tail & Orbiter/external tank rear attachments.
The forward bulkhead closes off the aft fuselage from the midfuselage. The upper portion of the bulkhead attaches to the vertical tail. The internal thrust structure supports the three Space Shuttle main engines, low pressure turbopumps & propellant lines.