Redundant pressure window panes are provided in the six forward windshields, the two overhead viewing windows, the two aft viewing windows and the side hatch windows; they are described in the window section. Approximately 300 penetrations in the pressure shell are sealed with plates and fittings. A large removable panel in the aft bulkhead provides access to the interior of the crew compartment during initial fabrication and assembly and provides for airlock installation and removal. The compartment supports the environmental control and life support system; avionics; guidance, navigation and control equipment; inertial measurement units; displays and controls; star trackers; and crew accommodations for sleeping, waste management, seats and an optional galley.

The crew compartment is supported within the forward fuselage at only four attach points to minimize the thermal conductivity between them. The two major attach points are located at the aft end of the crew compartment at the flight deck floor level. The vertical load reaction link is on the centerline of the forward bulkhead. The lateral load reaction is on the lower segment of the aft bulkhead.

The compartment is configured to accommodate a crew of four on the flight deck and three in the middeck. In OV-102, four can be accommodated in the middeck. The crew cabin arrangement consists of a flight deck, middeck and lower level equipment bay.

The crew compartment is pressurized to 14.7 psia, plus or minus 0.2 psia, and is maintained at an 80-percent nitrogen and 20-percent oxygen composition by the ECLSS, which provides a shirt-sleeve environment for the flight crew. The crew compartment is designed for 16 psia.

The crew compartment's volume with the airlock in the middeck is 2,325 cubic feet. If the airlock is in the payload bay, the crew compartment's cabin volume is 2,625 cubic feet.

The flight deck is the uppermost compartment of the cabin. The commander's and pilot's work stations are positioned side by side in the forward portion of the flight deck. These stations have controls and displays for maintaining autonomous control of the vehicle throughout all mission phases. Directly behind and to the sides of the commander and pilot centerline are the mission specialist seats.

The commander's and pilot's seats have two shoulder harnesses and a lap belt for restraints. The shoulder harnesses have an inertia reel lock/unlock feature. The unlocked position allows the shoulder harness to move. The commander and pilot can move their seats along the orbiter's Z (vertical) and X (longitudinal) axes so they can reach and see controls better during the ascent and entry phases of flight. Seat movement for each axis is provided by a single ac motor. The total travel distance for the Z and X axes is 10 and 5 inches, respectively. Seat adjustment controls are located on the left side of the seat pan and consist of a three-position toggle switch for power bus selection and one spring-loaded, three-position toggle switch each to control horizontal and vertical seat movement.

To operate the seat, the commander and pilot position the pwr buss sel switch to AC2 or AC3 for power; to move the seat along the horizontal axis, the commander and pilot position the horiz contr switch to fwd to move the seat forward and to aft to move the seat aft. Similarly, to move the seat along the vertical axis, the commander and pilot position the vert contr switch to up to move the seat upward and to down to move the seat down. The commander and pilot can position the pwr buss sel switch to off, removing power from the seat.

If the seat motors fail, the seat can be adjusted manually. However, manual seat adjustment can only take place on orbit and is accomplished with a special seat adjustment tool provided in the in-flight maintenance tool kit. Manual horizontal and vertical seat adjustment controls are located under the seat pan cushion and on the aft side of the fixed seat structure. The seat adjustment tool is a ratchet-driven, 3/16-inch allen wrench, which is inserted into the vertical or horizontal manual adjustment to move the seat along the Z or X axis. The seats accommodate stowage of in-flight equipment and have removable seat cushions and mounting provisions for oxygen and communications connections to the crew altitude protection system.

Each mission and payload specialist's seat has two shoulder harnesses and a lap belt for restraints. The specialists' seats have controls to manually lock and unlock the tilt of the seat back. Each seat has removable seat cushions and mounting provisions for oxygen and communications connections to the CAPS. The specialists' seats are removed and stowed in the middeck on orbit. No tools are required since the legs of each seat have quick-disconnect fittings. Each seat is 25.5 inches long, 15.5 inches wide and 11 inches high when folded for stowage.

The aft flight deck has two overhead and aft viewing windows for viewing orbital operations. The aft flight deck station also contains displays and controls for executing attitude or translational maneuvers for rendezvous, stationkeeping, docking, payload deployment and retrieval, payload monitoring, remote manipulator system controls and displays, payload bay door operations and closed-circuit television operations.

The forward flight deck, which includes the center console and seats, is approximately 24 square feet. However, the side console controls and displays add approximately 3.5 square feet more. If the center console is subtracted from the 24 square feet, this would amount to approximately 5.2 square feet.

The aft flight deck is approximately 40 square feet.

Directly beneath the flight deck is the middeck. Access to the middeck is through two interdeck openings, which measure 26 by 28 inches. Normally, the right interdeck opening is closed and the left is open. A ladder attached to the left interdeck access allows easy passage in 1-g conditions. The middeck provides crew accommodations and contains three avionics equipment bays. The two forward avionics bays utilize the complete width of the cabin and extend into the middeck 39 inches from the forward bulkhead. The aft bay extends into the middeck 39 inches from the aft bulkhead on the right side of the airlock. Just forward of the waste management system is the side hatch. The completely stripped middeck is approximately 160 square feet; the gross mobility area is approximately 100 square feet.

The side hatch in the middeck is used for normal crew entrance/exit and may be operated from within the crew cabin middeck or externally. It can be jettisoned for emergencies, as discussed in the escape system section. It is attached to the crew cabin tunnel by hinges, a torque tube and support fittings. The hatch opens outwardly 90 degrees down with the orbiter horizontal or 90 degrees sideways with the orbiter vertical. It is 40 inches in diameter and has a 10-inch clear-view window in the center of the hatch. The window consists of three panes of glass. The side hatch has a pressure seal that is compressed by the side hatch latch mechanisms when the hatch is locked closed. A thermal barrier of Inconel wire mesh spring with a ceramic fiber braided sleeve is installed between the reusable surface insulation tiles on the forward fuselage and the side hatch. The total weight of the side hatch is 294 pounds.

Depending on the mission requirements, bunk sleep stations and a galley can be installed in the middeck. In addition, three or four seats of the same type as the mission specialists' seats on the flight deck can be installed in the middeck. Three seats over the normal three could be installed in the middeck for rescue missions if the bunk sleep stations were removed.

The waste management system, located in the middeck, can also accommodate payloads in the pressurized crew compartment environment.

The middeck also provides a stowage volume of 140 cubic feet. Accommodations are included for dining, sleeping, maintenance, exercising and data management. On the orbiter centerline, just aft of the forward avionics equipment bay, an opening in the ceiling provides access to the inertial measurement units.

The middeck floor contains removable panels that provide access to the ECLSS equipment. The middeck equipment bay below the middeck floor houses the major components of the waste management and air revitalization systems, such as pumps, fans, lithium hydroxide, absorbers, heat exchangers and ducting. This compartment has space for stowing lithium hydroxide canisters and five separate spaces for crew equipment stowage with a volume of 29.92 cubic feet.

Modular stowage lockers are used to store the flight crew's personal gear, mission-necessary equipment, personal hygiene equipment and experiments. The modular lockers are made of sandwich panels of Kevlar/epoxy and a non-metallic core. This reduced the lockers' weight by 83 percent compared to all-aluminum lockers, a reduction of approximately 150 pounds. There are 42 identical boxes, which are 11 by 18 by 21 inches.

An airlock, located in the middeck, is composed of machined aluminum sections welded together to form a cylinder with hatch mounting flanges. The upper cylindrical section and bulkheads are constructed of aluminum honeycomb. Two semicylindrical aluminum sections are welded to the airlock's primary structure to house the ECLSS and electrical support equipment. Each semicylindrical section has three feedthrough plates for plumbing and cable routings from the orbiter to the airlock.

Normally, two extravehicular mobility units are stowed in the airlock. The EMU is an integrated space suit assembly and life support system that enables flight crew members to leave the pressurized orbiter crew cabin and work outside the cabin in space.