The Orbiter is as large as a mid-size airline transport and has a structure like that of an aircraft: an aluminum alloy skin stiffened with stringers to form a shell over frames and bulkheads of aluminum or aluminum alloy. The major structural sections of the Orbiter are the forward fuselage, which contains the pressurized crew compartment; the mid fuselage, which contains the payload bay; the aft fuselage, from which the main engine nozzles project; and the vertical tail, which splits open along the trailing edge to provide a speed brake used during entry and landing.

The crew compartment is divided into two levels - the flight deck on top and the middeck below. The flight deck includes all flight controls used for launch, orbital trajectory corrections, rendezvous operations, and landing. The middeck provides the crew's working, eating, and sleeping environment. It also houses the electronic, guidance, and navigation systems. When installed, the airlock to the payload bay or adapter tunnel is on the middeck. A normal mission includes up to 7 crewmen and women, although up to 10 can be accommodated under emergency circumstances.

The payload bay is 15 feet in diameter and 60 feet long. The Orbiter has payload capacity of up to 65,000 pounds depending on the altitude and inclination desired. In addition, the Orbiter can also return up to 32,000 pounds of payload from space. "Clamshell" doors on top of the payload bay are opened once the Shuttle attains earth orbit and are closed again prior to deorbit and entry.

The Orbiter has four types of external insulation designed to keep ascent and entry temperatures within design specifications.

1. The nose cap and wing leading edges are protected with a reinforced carbon-carbon alloy.
2. The underside, nose, and the areas surronding the wing leading edges use high-temperature black ceramic tiles that are approximately 6 inches square and 1 to 5 inches deep.
3. Other "low temperature" (white) tiles are spaced across other portions of the Orbiter.
4. Thermal "blankets" (also white) cover the remaining surfaces.

There are approximately 30,000 tiles on each Shuttle Orbiter. Each has their own unique shape and serial number.

The two engine pods on the aft fuselage of the Orbiter contain maneuvering engines (Orbital Maneuvering System, or OMS) and their propellant -monomethyl hydrazine (fuel) and nitrogen tetroxide (oxidizer). Helium tanks pressurize the propellant tanks, and the fuel and oxidizer ignite on contact (known as "hypergolic"). There are also forty-four smaller rocket motors (the Reaction Control System, or RCS) on the Orbiter's nose and aft section that allow attitude control as well as small trajectory changes. A separate set of fuel, oxidizer, and helium tanks are kept in the nose section for the forward RCS jets.

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