Crew Cabin

The two-to-eight person crew occupies a two-level cabin at the forward end of the orbiter. They operate the vehicle from the upper level, the flight deck. The flight controls for the mission commander and pilot are at the front. A station at the rear, overlooking the payload bay through two windows, containing the controls a mission specialist astronaut uses to operate the Remote Manipulator System arm which handles some items in the payload. Mission operations displays and controls are on the right side of the cabin, and payload controls on the left. The latter are operated by payload specialists, who are usually not career astronauts. The living, eating and sleeping area for off-duty crew members, called the middeck, is located below the flight deck. It contains pre-packaged food, a toilet, bunks, and other amenities.

The daily routine for crew members aboard flights will vary according to crew assignments but each member will follow a detailed schedule each day. Time is allotted for each person for sleep, personal hygiene, work, meal preparation, and eating as well as routine Orbiter subsystem housekeeping. Housekeeping duties include cleaning the waste compartment, dumping excess water, replacing the carbon dioxide scrubbing canisters, purging the fuel cells, giving daily status reports to the ground controllers, and aligning the inertial measurement unit (the device that directs the vehicle attitude in space). A 24-hour time period is normally divided into an 8-hour sleep period and a 16-hour awake period for each crew member.

Spacehab Module

Periodically the Shuttle is scheduled to carry a complete scientific laboratory called "Spacelab" into Earth orbit. Two complete Spacelabs (plus instrument-carrying platforms exposed to space, called "pallets") have been built by the European Space Agency (ESA), which paid for the development expense and manufacturing costs of the first one. NASA purchased the second unit. A Spacelab is similar to a small but well-equipped laboratory on Earth, but has been designed for zero-gravity operation. It provides a shirt-sleeve environment where up to four people, who eat and sleep in the orbiter, can perform scientific tests utilizing the high vacuum and microgravity of orbital space, and make observations above the abscurring atmosphere.

Spacelab payload specialists are men and women of many nations, experts in their fields, who must be in reasonably good health. They are required to have only a few weeks of spaceflight training, but may have spent years preparing to perform their experiments in orbit.

Currently, most of the experiments on a given Spacelab mission are devoted to a single broad field, such as medicine, manufacturing, astronomy, space physics or pharmaceuticals. Some previous Spacelab flights combine experiments from several fields. One mission utilized an all-pallet configuration, where all the instruments were exposed to space and operated from inside the orbiter.

Cargo Bay

The Space Shuttle is designed to carry large and heavy payloads into Earth orbit. The payload bay is 60 feet (18.3 meters) long and 15 feet (4.6 meters) wide, about the size of a school bus. The bay is flexible enough to provide accommodations for unmanned spacecraft in a variety of shapes and sizes, and for fully equipped scientific laboratories such as the Spacelab. Depending on the requirements of the particular mission, a Space Shuttle can carry about 50,000 pounds (22,680 kilograms) into orbit.

The Shuttle also provides a new capability, to repair malfunctioning satellites in orbit, or return them to Earth for a more extensive overhaul and another launch. Solar Maximum Mission, a complex scientific spacecraft, was repaired in orbit at a small percentage of the cost of building and launching a new satellite. The Westar VI and Palapa B-2 communications satellites, stranded in low orbit by failures in their attached booster rockets, were recovered, returned to ground, refurbished, and later success fully re-launched on commercial unmanned vehicles.

All satellites released from a Space Shuttle enter low Earth orbit. Some, such as the Hubble Space Telescope, for astronomical observations, or the Upper Atmosphere Research Satellite, for monitoring the environment, remain there throughout their working lives. Interplanetary explorers launch from Space Shuttles, such as the Magellan mission to Venus, or the Galileo spacecraft to Jupiter, also use the IUS . They leave low Earth orbit on trajectories that will take them to Earth's planetary neighbors.

The Remote Manipulator System (RMS), the shuttle "arm", is a 15.2 meter (50 foot) long articulating arm that is remotely controlled from the flight deck of the orbiter. The elbow and wrist movements of the RMS permit payloads to be grappled for deployment out of the payload bay attach points or to be retrieved and secured for return to Earth. Because the RMS can be operated from the shirt-sleve environment of the cabin, an Extra Vehicular Activity, EVA, "spacewalk", maneuver is not required.

Space Shuttle Main Engines

The Space Shuttle main engine is the most advanced liquid-fueled rocket engine ever built. Its main features are variable thrust, high performance, reusability, total redundancy, and a fully integrated controller. The performance of the engine is the highest thrust for its weight of any engine yet developed. Three main engines are mounted on the orbiter aft fuselage in a triangular pattern. The engines are spaced so that they are movable during flight and, in conjunction with the two solid rocket boosters, are used to steer the Shuttle vehicle during flights as well as provide thrust for launch.

Fuel for the engines, liquid hydrogen and liquid oxygen, is contained in the external tank, the largest element of the Shuttle. Fuel is supplied from the tank at a rate of about 178,000 liters (47,000 gallons) per minute of hydrogen and 64,000 liters (17,000 gallons) per minute of oxygen.

The main engines use a staged combustion cycle in which all propellants entering the engines are used to produce thrust more efficiently than any rocket engine developed previously. In the staged combustion cycle, propellants are burned partially at high pressure and relatively low temperature, and then burned completely at high temperature and high pressure in the main combustion chamber. The rapid mixing of the propellants under these conditions is so complete that a combustion efficiency of about 99 percent is attainable.

The Shuttle main engine is the first rocket engine to use a built-in electronic digital controller. The controller will accept commands from the orbiter for engine start, shutdown and change in throttle setting, and also will monitor engine operation. In the event of a failure, the controller takes action automatically to correct the problem or shutdown the engine safely. Shuttle main engines are thoroughly inspected and tested between flights to assure acceptable operation during subsequent flights. The design goal is to operate for 7.5 accumulated hours.

The Space Shuttle external tank (ET) is the largest single element and the only major non-reusable component of the Shuttle system. The ET is 154 feet (47 meters) long and 27.6 feet (8.4 meters) in diameter and carries more than 528,600 gallons (2 million liters) of cryogenic propellants that are fed to the orbiter's three main engines during powered flight.

The ET is the structural backbone of the Shuttle system and absorbs the total 6,610,000-pound thrust loads generated by the orbiter's three main engines and two solid rocket boosters. The tank is non-reusable, and must be produced economically in quantities needed to meet the frequency of Shuttle flight.

The ET is actually three components in one: a liquid oxygen tank located in the forward position; a liquid hydrogen tank located aft; and an intertank assembly that connects the two propellant tanks and houses the forward solid rocket booster attachment points. The ET weighs approximately 1,655,600 pounds (751,000 kilograms) when filled with propellants and 66,000 pounds (29,900 kilograms) when empty.

The ET is covered with a multilayered thermal protective coating approximately 1 inch (2.5 centimeters) thick. The insulation allows the tank to withstand the extreme internal and external temperatures generated during prelaunch, launch, and flight. The exact materials, thicknesses, and methods of application vary at different locations on the tank.

At launch, propellants are pressure fed at a combined rate of 1,035 gallons (3,900 liters) per second through 17-inch (43.2 centimeter) diameter feedlines to the orbiter's three main engines. Eight and one-half minutes into flight, the orbiter and ET have reached an altitude of about 71 miles (114 kilometers), the main engines are cut off and the tank is jettisoned. Residual gaseous oxygen is used to initiate a slow tumble away from the orbiter, prevent the ET from skipping off the Atmosphere, and assist in its break-up and descent into a remote ocean area.

Prior to launch, the entire weight of the Space Shuttle is supported on the launch pad by two solid rocket boosters. Each booster is attached to the pad by four large bolts. The heart of each booster is the motor, the largest solid rocket ever to be flown and the first designed for reuse. It is made of four factory prepared segments filled with propellant at the manufacturer's facility and assembled at the launch site. The segmented design permits ease of fabrication, transportation and handling.

The motor segments are located in pairs from one batch of propellant ingredients to minimize any thrust imbalances between boosters used for a single Shuttle flight. Propellant loading is also done in such a manner as to cause a reduction in thrust 55 seconds into the Shuttle flight to prevent overstressing the Shuttle vehicle during its critical phase of flight, the period of maximum dynamic pressure. The exhaust nozzle in the aft segment of each motor, in conjunction with the orbiter main engines, steers the Shuttle during flight. It can be moved up to eight degrees by the booster thrust vector control system which is controlled by the orbiter guidance and control computer.

At burnout the two solid rocket boosters are separated from the external tank by pyrotechnic (explosive) devices and moved away from the Shuttle vehicle by eight separation motors - four housed in the forward compartment and four mounted on the aft skirt. The separation motors are fired by a command from the orbiter. The recovery system, in the forward section of the booster, consists of parachutes and a homing device. Following separation - at about 5.8 kilometers (19,000 feet) - the booster is slowed by a drogue parachute and finally by three main parachutes to impact water at a speed of about 25 meters/second (85 feet/sec), aft end first. By entering the water this way, the air in the empty booster is trapped and compressed, causing the booster to float with the forward end out of the water. After divers insert a nozzle closure and force the water from the booster using air pumps, the booster is towed to shore.

After recovery, the booster is disassembled and refurbished. The motor segments are shipped to the manufacturer for reload for another Shuttle flight. The other systems are refurbished either at the launch site or at the respective manufactures' locations.

The two solid rocket boosters are each 149.1 feet (45.4 meters) high and 12.2 feet (3.7 meters) in diameter. Each weighs 1,300,000 pounds (589,670 kilograms). Their solid propellant consists of a mixture of Aluminum powder, Ammonium Perchlorate powder, and a dash of Iron Oxide catalyst, held together with a polymer binder. They produce about 3.1 million pounds (13.8 million newtons) thrust each for the first few seconds after ignition, before gradually declining for the remainder of a two-minute burn. Tog ether with the three main engines on the orbiter, this provides a total thrust of over 7.3 million pounds (32.5 million newtons) at liftoff