(The following,"Countdown!," PMS 018 (KSC), March 1987, is a narrative summary of NASA launch vehicles and facilities prepared by the NASA Kennedy Space Center. The document, which is too large for a single hypercard scroll field, has been separated into three different buttons. Button A contains information about launch vehicles, both active and inactive, and the various propellants used by these vehicles. Some of the information regarding KSC is now historic. In particular references to unmanned expendible launch facilities at KSC, which are no longer used as noted on the calendar card. However, the information is included for historic value. At present unmanned expendible launch vehicles are still launched elsewhere.) COUNTDOWN!
NASA LAUNCH VEHICLES AND FACILITIES
Space Launch Vehicles
People and cargo are propelled into space by rocket power. NASA uses two types of rockets for this purpose, manned and unmanned. The latter, often referred to as expendable launch vehicles, have one or more powered stages. The manned Space Shuttle, the key element of the nation's Space Transportation System, or STS, is a unique design, and is in a class by itself.
Payload weight, destination and purpose determine what vehicle capabilities are required for each mission. A low-weight spacecraft designed to operate in near-Earth orbit might be flown aboard NASA's smallest space vehicle, the Scout. Sending a manned Apollo spacecraft to the Moon required the massive Saturn V. The powerful Titan-Centaur combination sent large and complex unmanned scientific explorers such as the Vikings and Voyagers to examine other planets. Atlas-Agenas sent several spacecraft to impact the Moon. Atlas-Centaurs and Deltas have launched over 200 spacecraft for a wide variety of applications that cover the broad range of the national space program.
Today, NASA's fleet of space launch vehicles include only the unmanned Scout, Delta and Atlas-Centaur, and the manned Space Shuttle.
Inactive Launch Vehicles
The Atlas/Agena was a multipurpose two-stage liquid propellant rocket. It was used to place unmanned spacecraft in Earth orbit, or inject them into the proper trajectories for planetary or deep space probes.
The programs in which the versatile Atlas/Agena was used included early Mariner probes to Mars and Venus, Ranger photographic missions to the Moon, the Orbiting Astronomical Observatory (OAO), and early Applications Technology Satellites (ATS). The Agena upper stage also was used as the rendezvous target vehicle for the Gemini spacecraft during this series of two-man missions in 1965-1966. In preparation for the manned lunar landings, Atlas/Agena launched lunar orbiter spacecraft which went into orbit around the Moon and took photographs of possible landing sites
The Atlas/Agena stood 36.6 meters (120 feet) high, and developed a total thrust at liftoff of approximately 1,725,824 newtons (288,000 pounds). It was last used in 1968 to launch an Orbiting Geophysical Observatory (OGO).
The Saturn V, America's most powerful staged rocket, carried out the ambitious task of sending astronauts to the Moon. The first Saturn V vehicle, Apollo 4, was launched on November 9, 1967. Apollo 8, the first manned flight of the Saturn V, was also the first manned flight to the Moon; launched in December 1968, it orbited the Moon but did not land. Apollo 11, launched on a Saturn V on July 16, 1969, achieved the first lunar landing.
Saturn V began its last manned mission on December 7, 1972, when it sent Apollo 17 on the final lunar exploration flight. It was last used on May 14, 1973, when it lifted the unmanned Skylab space station into Earth orbit, where it was occupied by three crews for 171 days.
All three stages of the Saturn V used liquid oxygen as the oxidizer. The first stage burned kerosene with the oxygen, while the fuel for the two upper stages was liquid hydrogen. Saturn V, with the Apollo spacecraft and its small emergency escape rocket on top, stood 111 meters (363 feet) tall, and developed 34.5 million newtons (7.75 million pounds) of thrust at liftoff.
The Saturn IB was originally used to launch Apollo lunar spacecraft into Earth orbit, to train for manned flights to the Moon. The first launch of a Saturn IB with an unmanned Apollo spacecraft took place in February 1966. A Saturn IB launched the first manned Apollo flight, Apollo 7, on October 11, 1968.
After the completion of the Apollo program, the Saturn IB launched three missions to man the Skylab space station in 1973. In 1975 it launched the American crew for the Apollo/Soyuz Test Project, the joint U.S./Soviet Union docking mission.
Saturn IB was 69 meters (223 feet) tall with the Apollo spacecraft and developed 7.1 million newtons (1.6 million pounds) of thrust at liftoff.
The Titan III-E/Centaur, first launched in 1974, had an overall height of 48.8 meters (160 feet). Designed to use the best features of three proven rocket propulsion systems, this vehicle gave the U.S, an extremely powerful and versatile rocket for launching large spacecraft on planetary missions.
The Titan III-E/Centaur was the launch vehicle for two Viking spacecraft to Mars, and two Voyager spacecraft to Jupiter, Saturn, and Uranus. It also launched two Helios spacecraft toward the Sun. All provided remarkable new information about our solar system. The Vikings and Voyagers produced spectacular color photography of the planets they explored.
The Titan III-E booster was a two-stage liquid-fueled rocket with two large solid-propellant rockets attached. At liftoff, the solid rockets provided 10.7 million newtons (2.4 million pounds) of thrust.
The Centaur stage, still in use today, produces 133,440 newtons (30,000 pounds) of thrust from two main engines, and burns for up to seven and one-half minutes. The Centaur can be restarted several times, which allows for more flexibility in launch times.
Current Launch Vehicles
Delta is called the workhorse of the space program. This vehicle has successfully transported over 160 scientific, weather, communications and applications satellites into space. These include the TIROS Nimbus and ITOS satellites, and many Explorer scientific spacecraft.
First launched in May, 1960, the Delta has been continuously upgraded over the years. Today it stands 35.4 meters (116 feet) tall. Its first stage is augmented by nine Caster IV strap-on solid propellant motors, six of which ignite at liftoff and three after, the first six burn out 58 seconds into the flight. The average first-stage thrust with the main engines and six solid-propellant motors burning is 3,196,333 newtons (718,000 pounds). Delta has liquid-fueled first and second stages and a solid-propellant third stage. For most launches today, this third stage has been replaced by a Payload Assist Module (PAM) stage attached to the spacecraft.
The new PAM upper stage is also used on Space Shuttle launches. It boosts spacecraft from the low Earth orbit achieved by the Shuttle orbit into higher ones. Many spacecraft, especially communications satellites, operate in a geosynchronous (geostationary) orbit some 35,792 kilometers (22,240 miles) above the equator. With the PAM and a recent change to a more powerful second stage, the Delta can lift some 1,270 kilograms (2,800 pounds) into a highly elliptical orbit, for transfer into geosynchronous orbit by a motor built into the spacecraft. This is almost double the 680 kilograms (1,500 pounds) a Delta could manage only seven years ago.
The Atlas/Centaur is NASA's standard launch vehicle for intermediate payloads. It is used for the launch of Earth orbital, geosynchronous, and interplanetary missions.
Centaur was the nation's first high-energy, liquid-hydrogen liquid-oxygen launch vehicle stage. It became operational in 1966 with the launch of Surveyor-1, the first U.S. spacecraft to soft-land on the Moon.
Since 1966, both the Atlas booster and the Centaur second stage have undergone many improvements. At present, the combined stages can place over 4,530 kilograms (10,000 pounds) in low-Earth orbit, about 2,020 kilograms (4,453 pounds) in geosynchronous transfer orbit, and over 1,000 kilograms (2,205 pounds) on an interplanetary trajectory.
An Atlas-Centaur stands 41.9 meters (137.6 feet) tall. At liftoff, the Atlas booster develops over 1.9 million newtons (438,400 pounds) of thrust. The Centaur second stage develops 146,784 newtons (33,000 pounds) of thrust in a vacuum.
Spacecraft launched by Atlas/Centaurs include Orbiting Astronomical Observatories; Applications Technology Satellites; Intelsat IV, IV-A and V communications satellites; Mariner Mars orbiters; the Mariner, spacecraft which made a fly-by of Venus and three of Mercury; the Pioneer, spacecraft which accomplished fly-bys of Jupiter and Saturn, and that orbited Venus and plunged through its atmosphere to the surface.
The Scout launch vehicle, which became operational in 1960, has been undergoing systematic upgrading since 1976. The standard Scout vehicle is a solid-propellant, four-stage booster system approximately 23 meters (75 feet) in length with a launch weight of 21,600 kilograms (46,620 pounds) and liftoff thrust of 588,240 newtons (132,240 pounds).
Recent improvements include an uprated third-stage motor which increases the Scout's payload capability. It can now place up to 211 kilograms (465 pounds) in low Earth orbit. The third stage also has been provided with an improved guidance system.
Over 100 Scouts have been launched to date. They have been used to place a variety of U.S. and international payloads into inclined, equatorial, and polar orbits for orbital, probe, and reeentry missions.
On April 12, 1981, the first Space Shuttle vehicle lifted off from Launch Complex 39, Pad A, at the Kennedy Space Center. After a two-day test-flight mission that verified the craft's ability to function in space, the orbiter Columbia landed at Edwards Air Force Base in California. The Vehicle was piloted by astronauts John Young and Robert Crippen. The STS-1 mission marked the first time a new space vehicle had been manned on its first flight.
The Space Shuttle consists of a reusable delta-winged spaceplane called the orbiter; two solid propellant rocket boosters, which are recovered and also reused; and an expendable external tank, containing liquid propellants for the orbiter's three main engines.
The assembled Space Shuttle is approximately 56 meters (184 feet) long, 23.3 meters (76 feet) high (to tip of orbiter's vertical tail), and 24 meters (78 feet) wide, measured across the orbiter's wingtips. Liftoff weight of the Shuttle vehicle is approximately 2,041,168 kilograms (4,500,000 pounds).
At launch, the orbiter's three liquid-fueled engines‹drawing propellants from the external tank‹and the two solid propellant rocket boosters burn simultaneously. Together, they generate about 28,650,000 newtons (6,400,000 pounds) of thrust at liftoff. As the Space Shuttle reaches an altitude of about 50 kilometers (31 miles), the spent solids are detached and parachuted into the ocean where they are recovered by waiting ships for eventual refurbishment and reuse on later missions. The orbiter and external tank, still attached to each other, continue toward Earth orbit. When the orbiter's main engines cut off, just before orbit is achieved, the external tank is jettisoned, to impact in a remote ocean area. Using on-board orbital maneuvering engines, the orbiter, with its crew and payload, accelerates into orbit to carrry out an operational mission, normally lasting from two to seven days.
When the mission is completed, the orbiter reenters the atmosphere and returns to Earth, gliding to an unpowered landing. Touchdown speed is above 335 kilometers (210 miles) per hour.
Sir Isaac Newton stated in his Third Law of Motion that every action is accompanied by an equal and opposite reaction. A rocket operates on this principle. The continuous ejection of a stream of hot gases in one direction causes a steady motion of the rocket in the opposite direction.
A jet aircraft operates on the same principle, using oxygen in the atmosphere to support combustion of its fuel. The rocket engine is designed to operate outside the atmosphere, and so must carry its own oxidizer.
The gauge of efficiency for rocket propellants is specific impulse, stated in seconds. The higher the number, the "hotter" the propellant.
Stated most simply, specific impulse is the period in seconds for which a one pound mass of propellant (total of fuel and oxidizer) will produce a thrust of one pound force. Although specific impulse is a characteristic of the propellant system, its exact value will vary to some extent with the operating conditions and design of the rocket engine. It is for this reason that different numbers are often quoted for a given propellant or combination of propellants.
NASA launch vehicles use four types of propellants: petroleum, cryogenics, hypergolics and solids.
The petroleum used as a rocket fuel is a type of kerosene similar to the kind burned in heaters and lamps. However, petroleum used for rocket fuel is highly refined, and is called RP‹1 (Refined Petroleum). It is burned with liquid oxygen (the oxidizer) to provide thrust.
RP‹1 is used as a fuel in the first stage boosters of the Delta and Atlas-Centaur rockets. It also was used to power the first stages of the Saturn IB and Saturn V. RP‹1 delivers a specific impulse considerably less than cryogenic fuels.
Cryogenic propellants used are liquid oxygen (LOX), which serves as an oxidizer, and liquid hydrogen (LH2), which is a fuel. The word cryogenic is a derivative of the Greek kryos, meaning "ice cold." LOX remains in a liquid state at temperatures of -183 degrees Celsius (-298 degrees Fahrenheit); LH2 remains liquid at temperatures of -253 degrees Celsius (-423 degrees Fahrenheit).
In gaseous form, oxygen and hydrogen have such low densities that extremely large tanks would be required to store them aboard a rocket. But cooling and compressing them into liquids vastly increases their density, making it possible to store them in large quantities in smaller tanks.
The distressing tendency of cryogenics to return to gaseous form unless kept super-cool makes them difficult to store over long periods of time, and hence less than satisfactory as propellants for military rockets, which must be kept launch-ready for months at a time.
But the high efficiency of the liquid hydrogen/liquid oxygen combination makes the low temperature problem worth coping with when reaction time and storability are not too critical. Hydrogen has about 40 percent more "bounce to the ounce" than other rocket fuels, and is very light, weighing about one-half pound per gallon.
Oxygen is much heavier, weighing about 10 pounds per gallon.
The RL‹10 engines used by Centaur, the United States' (and the world's) first liquid hydrogen rocket stage, have a specific impulse of 444 seconds. The J-2 engines used on the Saturn V second and third stages, and on the Saturn IB's second stage, also burned the LOX/ LH2 combination. They had specific impulse ratings of 425 seconds.
For comparison purposes, the liquid oxygen/kerosene combination used in the cluster of five F-1 engines in the Saturn V first stage had specific impulse ratings of 260 seconds. The same propellant combination used by the booster stage of the Atlas-Centaur rocket yields 258 seconds in the booster engine and 220 seconds in the sustainer.
The high efficiency engines aboard the Space Shuttle orbiter use liquid hydrogen-oxygen and have a specific impulse rating of 455 seconds. The two liquid propellants also are used by the orbiter's fuel cells to produce electrical power through a process best described as electrolysis in reverse.
Liquid hydrogen and oxygen burn clean, leaving a by-product of water vapor.
The rewards for mastering LH2 are substantial. The ability to use hydrogen means that a given mission can be accomplished with a smaller quantity of propellants (and hence, a smaller vehicle), or, alternately, that the mission can be accomplished with a larger payload than is possible with the same mass of conventional propellants. In short, hydrogen yields a bigger bang for the buck.
Hypergolic propellants are fuels and oxidizers which ignite on contact with each other and need no ignition source. This easy start and restart capability makes them attractive for both manned and unmanned spacecraft maneuvering systems. Another plus is their storability‹they do not have the extreme temperature requirements of cryogenics The fuel is monomethylhydrazine (MMH), and the oxidizer is nitrogen tetroxide (N204) Hydrazine is a clear, nitrogen/ hydrogen compound with a "fishy" smell. It is similar to ammonia.
N204 is a brownish fluid which might be described as a super nitric acid. It has the sharp, acrid smell of many acids. Both fluids are highly toxic, and are handled under the most stringent safety conditions.
Hypergolic propellants are used in the liquid propellant stages of the Titan class of launch vehicles, including the Titan 11 I-E/Centaur series which was used by NASA to launch the Helios sun probes, and the Viking and Voyager planetary explorers.
The Space Shuttle orbiter uses hypergols in its Orbital Maneuvering Subsystem (OMS) for orbital insertion, major orbital maneuvers and deorbit. The Reaction Control System (RCS) uses hypergols for attitude control.
The efficiency of the MMH/ N204 combination in the Space Shuttle orbiter ranges from 260 to 280 seconds in the RCS to 313 seconds in the OMS. The higher efficiency of the OMS system is attributed to higher expansion ratios in the nozzles and higher pressures in the combustion chambers.
The solid propellant motor is the oldest and simplest of all forms of rocketry, dating back to the ancient Chinese. It is simply a casing, usually steel, filled with a mixture of solid-form chemicals (fuel and oxidizer) which burn at a rapid rate, expelling hot gases from a nozzle to achieve thrust.
Solids require no turbopumps or complex propellant feed systems. Ignition is by a simple squib device at the top of the motor which directs a high-temperature flame along the surface of the propellant grain, igniting it instantaneously.
The propellant, a rubbery substance with the consistency of a hard rubber eraser, has a starshaped (other shapes are possible) hollow channel extending through the center. When ignited the propellant burns from the center out toward the sides of the casing.
The shaped center channel exposes more or less burning area at any given point in time, thus providing a means to vary the thrust of the expelled gases.
Solid propellants are easily stored and stable. Unlike liquid propellant engines though, a solid propellant motor cannot be shut down. Once ignited, it will burn until all propellant is exhausted.
Solids are used in a variety of ways for space operations. Small solids often power the final stage of a launch vehicle, or are attached to payload elements to boost satellites and spacecraft to higher orbits.
Medium solids such as the Payload Assist Module (PAM) and the Inertial Upper Stage (IUS) provide the added boost to place satellites into geosynchronous orbit or on planetary trajectories.
The PAM is used for payload boost on the Delta and Space Shuttle. The IUS is carried by the Space Shuttle and the Titan III class of launch vehicles.
Only one of the nation's stable of launch vehicles uses solids exclusively. This is NASA's Scout, a four-stage rocket used to orbit small satellites.
Titan, Delta, and Space Shuttle vehicles depend on solid rockets to provide added thrust at liftoff.
The Space Shuttle uses the largest solid rocket motors ever built and flown. Each, which is reusable, contains 498,951 kilograms (1.1 million pounds) of propellant.
This propellant consists of an aluminum powder (16 percent) as a fuel; ammonium perchlorate (69.93 percent) as an oxidizer; iron oxidizer powder (.07 percent) as a catalyst; polybutadiene acrylic acid acrylonitrile (12.04 percent) as a rubber-based binder; and an epoxy curing agent (1.96 percent). The binder and epoxy are also burned as a fuel, adding thrust.
The specific impulse of the Space Shuttle solid rocket booster propellant is 242 seconds at sea level and 262 seconds at altitude.
Facilities and Operations
NASA conducts launch operations for its current stable of launch vehicles at several sites across the country. The Scout rocket is launched by the Langley Research Center from facilities at Vandenberg Air Force Base in California, and from the Wallops Flight Facility on the east coast of Virginia. Visiting teams from Italy occasionally launch Scouts from San Marco, a man-made platform in the ocean off the east coast of Africa.
The Kennedy Space Center, the nation's primary launch organization, prepares and launches unmanned Deltas and Atlas-Centaur rockets from facilities at Complexes 17 and 36 on Cape Canaveral Air Force Station, Florida. Manned Space Shuttle launches are conducted from Launch Complex 39, located at the northern tip of Cape Canaveral.
The Complex 39 facilities at Kennedy Space Center originally were built to support the Apollo Lunar Landing Program. From 1967 to 1975, 12 Saturn V/Apollo vehicles, one Saturn V/Skylab workshop, three Saturn IB/Apollo vehicles for the Skylab crews, and one Saturn IB/Apollo for the joint U.S./Soviet Apollo-Soyuz mission were launched from Complex 39. These facilities then were modified to process and launch the Space Shuttle. Reworking existing facilities was far less expensive than building all new structures. Two major new additions were added, a special runway to land returning orbiters and an orbiter checkout hangar called the Orbiter Processing Facility. During the 1980s, a number of new facilities were added for solid rocket booster processing and Shuttle logistics.
These facilities, and how they support Space Shuttle operations, are explained in the following paragraphs.
Shuttle Landing Facility
When an operational Space Shuttle orbiter returns to Earth from its mission in space and lands at the Kennedy Space Center, it touches down on one of the world's longest runways. This facility is located two miles northwest of the Vehicle Assembly Building, on a northwest/southeast alignment.
The Shuttle Landing Facility runway is about twice the length and width of those used at commercial airports. It is 4,572 meters (15,000 feet) long, 91.4 meters (300 feet) wide, and 40.5 centimeters ( 16 inches) thick at the center. Safety overruns of 305 meters ( 1,000 feet) are provided at each end. The runway is not perfectly flat, but has a slope of 61 centimeters (24 inches) from the centerline to the edge. Small grooves, each 0.63 centimeter (0.25 inch) wide and deep, have been cut into the concrete every 2.85 centimeters (1.25 inches) across the runway. There are a total of 13,600 kilometers (8,450 miles) of these grooves. Together with the slope of the concrete they provide rapid drain-off of rain, as well as a more skid-resistant surface.
A 168-meter (550-foot) by 149-meter (490-foot) aircraft apron, or ramp, is attached to the runway near the southeastern end. The Mate/Demate Device, which lifts the orbiter for attachment to or removal from its 747 carrier aircraft during ferry operations, is located on the northeast corner of the ramp. It also provides movable platforms for access to certain orbiter components.
A Tactical Air Navigation (TACAN) station is located at midfield off the east side of the runway. This is a homing transmitter that broadcasts a signal receivable by the orbiter. The TACAN has a range of 483 kilometers (300 miles) and is received when the spacecraft emerges from the reentry blackout period. The final approach is guided by a precision Microwave Scanning Beam Landing System, which is accurate to within 99.33% in bringing the orbiter to the designated point on the runway.
Unlike conventional aircraft, the orbiter lacks propulsion during the landing phase. Its high-speed glide must bring it in for a landing perfectly the first time‹there is no circle-and-try-again capability. The landing speed of the orbiter is 346 kilometers (215 miles) per hour.
Landings may be made on the runway from the northwest to southeast (Runway 15) or from the southeast to northwest (Runway 33). The landing system ground equipment is duplicated to permit an approach from either direction. Shuttle landings also are made at Edwards AFB, California.
Orbiter Processing Facility
Space Shuttle orbiters are processed between missions in a structure analogous to a sophisticated aricraft hanger, the Orbiter Processing Facility. Capable of handling two orbiters in parallel, this facility is located to the west of the Vehicle Assembly Building.
The Orbiter Processing Facility consists of two identical high bays connected by a low bay. The high bays are each 60 meters (197 feet) long, 46 meters (150 feet) wide, and 29 meters (95 feet) high. Each is equipped with two 27-metric ton (30-ton) bridge cranes, and contains platforms which effectively surround the orbiter to provide personnel access. The high bay areas have an emergency exhaust system in case of a fuel spill, and fire protection systems are installed throughout the facility. The low bay separating the two high bays is 71 meters (233 feet) long, 30 meters (97 feet) wide, and eight meters (25 feet) high. The low bay houses electronic, mechanical, and electrical support systems as well as shops and office space.
Spacecraft processed through checkout in a horizontal attitude, such as the Hubble Space Telescope, are loaded into the orbiter in the Orbiter Processing Facility. Spacecraft that are checked out and installed in a vertical attitude are mated with the orbiter at the launch pad. The processing of the orbiter for flight resembles an airline maintenance program, rather than the customary long and complex space vehicle checkout and launch operation .
Orbiter Modification and Refurbishment Facility
Located just northwest of the Vehicle Assembly Building, this 4,645 square meter (50,000 square foot) facility is used to perform modification, rehabilitation and overhaul of Space Shuttle orbiters outside of the facilities used in the normal operational flow. The building consists of a high bay 29 meters (95 feet) high and a two story low bay area. It contains special work platforms, storage and parts areas, offices, and specialized equipment needed to perform orbiter modifications that do not require a return to the manufacturing facilities in California.
This modern, 30,159 square meter (324,640 square foot) facility is located south of the Vehicle Assembly Building and houses some 190,000 shuttle hardware parts and over 500 NASA and contractor personnel. A unique feature of the building is its state-of-the-art storage and retrieval system which includes automated handling equipment to find and retrieve specific parts.
Solid Rocket Booster Processing
Following a Space Shuttle launch, the expended solid rocket boosters parachute into the ocean. They are retrieved by recovery ships and towed back to facilities on Cape Canaveral Air Force Station for disassembly and cleaning. The empty propellant-carrying segments are transferred to booster processing facilities at Complex 39, where they are prepared for shipment by rail to the manufacturer for propellant reloading. The remaining solid rocket booster components are taken to an assembly and refurbishment area adjacent to Complex 39 for reconditioning, assembly, and testing.
The solid rocket booster launch processing flow is as follows:
Rotation Processing Building: located just north of the Vehicle Assembly Building, this facility receives new and reloaded solid rocket booster segments‹aft, aft center, forward and forward center‹shipped by rail from the manufacturer. Here, inspection, rotation and aft skirt/aft segment buildup are performed.
Assembly and Refurbishment Facility: this facility, located several miles south of the Vehicle Assembly Building, covers 45 acres and consists of four main buildings‹ Manufacturing, Engineering and Administration, Service, and Hot Fire. Inert booster components such as the aft and forward skirts frustums, nose caps, recovery systems, electronics and instrumentation, and elements of the thrust vector control system are received, refurbished, assembled, and tested. Completed aft skirt assemblies are transferred to the Rotation Processing Building for integration with the aft segments. The remaining components are integrated with the booster stack during mating operations inside the Vehicle Assembly Building.
SURGE Buildings (2): each of these facilities is used to store two solid rocket booster flight sets (eight segments) after transfer from the adjacent Rotation Processing Building. They remain here until moved to the Vehicle Assembly Building for integration with other flight-ready booster components from the Assembly and Refurbishment Facility.
Vehicle Assembly Building: all booster elements are integrated here into complete flight sets and mated with the Space Shuttle orbiter and external tank.
The external tank is transported by barge from its manufacturing site at Michoud, Louisiana, to Kennedy Space Center. It is offloaded at the Complex 39 turn basin and transferred into the Vehicle Assembly Building, where it is processed and stored in the high bay area until mating with the other Space Shuttle flight elements.
The external tank is the largest element of the Space Shuttle system. It contains two inner tanks which hold the liquid oxygen and liquid hydrogen propellants that are fed into the orbiter's main engines during the ascent phase of launch. It is the only Space Shuttle component that is not recovered and reused.
Vehicle Assembly Building
After preparation in the Orbiter Processing Facility, the orbiter is towed to the Vehicle Assembly Building. This is the heart of Launch Complex 39 and has been modified for use in assembling the Space Shuttle vehicle.
One of the largest buildings in the world, the Vehicle Assembly Building covers a ground area of 32,376 square meters (eight acres) and has a volume of 3,624,000 cubic meters (129,428,000 cubic feet). It is 160 meters (525 feet) tall, 218 meters (716 feet) long and 158 meters (518 feet) wide. The building is divided into a high bay area 160 meters (525 feet) tall, and a low bay area which is 64 meters (210 feet) tall.
The structure is designed to withstand winds of up to 200 kilometers (125 miles) per hour. Its foundation rests on more than 4,200 steel pilings 40 centimeters (16 inches) in diameter, driven down to bedrock at a depth of 49 meters (160 feet) .
The Vehicle Assembly Building has more than 70 lifting devices, including two 227-metric ton (250 ton) bridge cranes.
The Low Bay area contains Space Shuttle main engine maintenance and overhaul shops, and serves as a holding area for solid rocket booster forward assemblies and aft skirts.
High Bays 1 and 3 are used for integration and stacking of the complete Space Shuttle vehicle. High Bay 2 is used for external tank checkout and storage and as a contingency storage area for orbiters. High Bay 4 also is used for external tank checkout and storage as well as for payload canister operations and solid rocket booster contingency handling.
During Space Shuttle buildup operations inside the Vehicle Assembly Building, integrated solid rocket booster segments are transferred from nearby assembly and checkout facilities, hoisted onto a Mobile Launcher Platform in High Bays 1 or 3 and mated together to form two complete solid rocket boosters. The external tank, after arrival by barge, and subsequent checkout, inspection and storage in High Bays 2 or 4, is transferred to High Bays 1 or 3 to be attached to the solid rocket boosters already in place. The orbiter, the final element to be added, is towed from the Orbiter Processing Facility to the Vehicle Assembly Building transfer aisle, raised to a vertical position by overhead Granes, lowered onto the Mobile Launcher Platform, and mated to the rest of the stack.
When assembly and checkout operations are complete, the huge outer doors of a high bay open to permit the Crawler-Transporter to enter and move under the Mobile Launcher Platform holding the assembled Shuttle vehicle. These high bay doors are 139 meters (456 feet) high from ground to top. Seven 23 meter (76 foot) wide sliding panels rise vertically into a protected enclosure near the top of the building. Four panels at the bottom move apart horizontally, to create an opening that is 46 meters (152 feet) wide and 35 meters (114 feet) high. The Mobile Launcher Platform is so huge it forms a fairly snug "fit" within these dimensions.
Launch Control Center
If the Vehicle Assembly Building is the heart of Launch Complex 39, the Launch Control Center is its brain. This is a four-story structure on the east side of the Vehicle Assembly Building and connected with it by an elevated, enclosed bridge.
The Launch Control Center contains four firing rooms that are used to conduct NASA and classified military launches. Each is equipped with the Launch Processing System which monitors and controls most Space Shuttle assembly, checkout, and launch operations . The Space Shuttle final countdown requires approximately five hours, compared to 28 hours for a Saturn/Apollo countdown. Launches utilizing the Launch Processing System require approximately 90 personnel in the firing room as compared with 450 needed for previous manned missions.
The Launch Processing System consists of two major parts, the Central Data Subsystem and the Checkout, Control, and Monitor Subsystem.
The Central Data Subsystem operates four computers that store test procedures, vehicle processing data, a master program library, historical data, and pretest/posttest analyses. The Central Data Subsystem is located on the second floor of the Launch Control Center.
The operators of the Checkout, Control, and Monitor Subsystem utilize consoles, mini-computers, a large mass storage unit, and other related equipment located in the firing rooms to actually process and launch the vehicle. Shuttle checkout, countdown, and launch operations are conducted with the support of the information stored in the Central Data Subsystem.
The Mobile Launcher Platform is a steel structure 7.6 meters (25 feet) high, 49 meters (160 feet) long, and 41 meters (135 feet) wide. It selves as a transportable launch base for the Space Shuttle. The platform is constructed of steel up to 15 centimeters (six inches) thick. At their parking sites north of the Vehicle Assembly Building, in the high bays, and at the launch pads, the two Mobile Launcher Platforms rest on six 6.7-meter (22-foot) tall pedestals. There are three openings through the main body of a platform. Two are for the exhaust of the solid rocket boosters, and the third, the one in the center, is for the Shuttle main engines exhaust.
Two large devices called Tail Service Masts sit on each side of the Space Shuttle orbiter main engines exhaust hole. They provide several umbilical connections to the orbiter, including a liquid oxygen line running through one and a liquid hydrogen line through the other. These cryogenic propellants are fed into the external tank from the pad tanks via these connections. At launch the umbilicals are pulled away from the orbiter and retract into the masts, where protective hoods rotate closed to shield them from the exhaust flames. Each Tail Service Mast assembly is 4.5 meters (15 feet) long, 2.7 meters (nine feet) wide, and rises 9.4 meters (31 feet) above the platform deck.
The Hydrogen Burnoff System consists of two 1.5-meter (5-foot) long booms, one suspended from each Tail Service Mast. Each boom contains four flare-like devices which are designed to burn off gas from a preignition flow of liquid hydrogen through the main engines. This is to keep a cloud of excess gaseous hydrogen from forming, which could explode upon ignition of the main engines.
The Space Shuttle is supported and held on the Mobile Launcher Platform by eight attach posts, four on the aft skirt of each of the two solid rocket boosters. These fit on counterpart posts located in the platform's two solid rocket booster support wells. The vehicle is freed by triggering explosive nuts which release the giant studs linking the solid rocket booster attach posts with the platform support posts.
There are two inner levels in each Mobile Launcher Platform, with various rooms that house electrical, test, and propellant loading equipment. Unloaded, a Mobile Launcher Platform weighs 3.7 million kilograms (8.23 million pounds).
The two Crawler-Transporter tracked vehicles were previously used to move Saturn rockets from the Vehicle Assembly Building to the launch pad. The transporters are 6.1 meters (20 feet) tall, 40 meters (131 feet) long and 35 meters (114 feet) wide. The maximum speed unloaded is 3.2 kilometers (two miles) per hour, while maximum speed with the load of the Space Shuttle is 1.6 kilometers (one mile) per hour. A crawler has eight tracks, each of which has 57 shoes, or cleats. Each shoe weighs approximately one ton. Unloaded, the transporter weighs 2,857,680 kilograms (6.3 million pounds).
The transporters have a leveling system that will keep the top of the Space Shuttle vertical while negotiating the five-percent grade leading up to the top of the launch pad.
The transporter is powered by two 2,750 horsepower diesel engines. The engines drive four 1,000 kilowatt generators which provide electrical power to the 16 traction motors.
The Payload Canister provides restraint and protection to the various Shuttle payloads while in transit from payload processing or assembly facilities to either the launch pad (vertically handled payloads) or Orbiter Processing Facility (horizontally handled payloads). The canister is 21 meters (69 feet) long, 6.4 meters (21 feet) wide and 6.4 meters (21 feet) high.
The canister is made to physically resemble the cargo bay of the orbiter. It can accommodate payloads up to 18.3 meters (60 feet) long, 4.5 meters (15 feet) in diameter, and up to 29,481 kilograms (65,000 pounds) in weight. It provides environmental control and protection to payloads while in transit, and can supply certain needed support services such as gas purges and monitoring of critical measurements.
The Payload Canister Transporter is a 48-wheel self-propelled truck designed to transport the canister and its associated hardware. The transporter rides on rubber tires and is designed to operate on normal hard road surfaces. It is 19.8 meters (65 feet) long and 7 meters (23 feet) wide. Its elevating flatbed has a height of 1.8 meters (6 feet) but can be lowered to 1.6 meters (5 feet 3 inches) or raised to 2.1 meters (7 feet). Its wheels are independently steerable and permit the transporter to move forward, backward, or sideways; to "crab" diagonally; or to turn on its own axis like a carousel.
The transporter is driven by a hydraulic system powered by a liquid-cooled diesel engine. However, when within a spacecraft facility the transporter runs on an electric motor using ground power.
The bare transporter weighs 63,500 kilograms (140,000 pounds). With a full load of diesel fuel, the environmental control system, communications systems, and other equipment and instrumentation mounted on it, the transporter has a gross weight of 77,300 kilograms (170,500 pounds).
The transporter is steerable from diagonally opposed operator cabs on each end. Its top speed unloaded is 16 km/h (10 mph), but fully loaded it is 8 km/h (5 mph). Because payload handling will require precise movements, the transporter has a "creep" mode that permits it to move as slowly as 0.023 km/h (0.014 mph). The transporter can carry the payload canister in either the horizontal or vertical position.
The Crawler-Transporters move on a roadway 40 meters (130 feet) wide, almost as broad as an eightlane turnpike. The crawlerway consists of two 12-meter (40-foot) wide lanes, separated by a 15-meter (50-foot) wide median strip, that run from the Vehicle Assembly Building to the launch pads. The top surface on which the transporters operate is river gravel. This glavel layer is 20 centimeters (eight inches) thick on curves and half that on the straightaway sections. The distance from the Vehicle Assembly Building to Pad 39A is about 5.6 kilometers (3.5 miles), and to Pad 39B, 6.8 kilometers (4.25 miles).
Launch Pads 39A and 39B
The Launch Complex 39 pads are roughly octagonal in shape. Each covers about 0.64 square kilometer (0.25 square mile) of land, contained within a high chain link fence. Space Shuttles are launched from the top of the concrete hardstand in the center of the pad. The Pad A stand is 14.63 meters (48 feet) above sea level at its top, and Pad B is 16.76 meters (55 feet). The top of each pad measures 119 meters (390 feet) by 99 meters (325 feet). The two major items of equipment on each pad are the Fixed Service Structure and the Rotating Service Structure.
The Fixed Service Structure is located on the west side of the hardstand. A hammerhead crane on top provides hoisting services as required in pad operations. There are 12 work levels at six-meter (20 foot) intervals. The height of the structure to the top of the tower is 75 meters (247 feet), to the top of the hammerhead crane 81 meters (265 feet), and to the top of the lightning mast 106 meters (347 feet).
Swingarms on the Fixed Service Structure provide access to the orbiter for crew and equipment. The Orbiter Access Arm swings out to the crew compartment to provide personnel access. The outer end of this arm supports a small room, holding up to 6 persons, commonly called the "White Room." It mates with the crew hatch. This arm remains in the extended position until seven minutes prior to launch, to provide an emergency exit for the crew should one be needed. It is 20 meters (65 feet) long, 1.5 meters (5 feet) wide, and 2.4 meters (8 feet) high. The Orbiter Access Arm is attached to the Service Structure at the 44.8-meter (147-foot) level. It rotates to its retracted position in approximately 30 seconds.
The External Tank Gaseous Oxygen Vent Arm lowers a hood, called the beanie cap, over the top of the Shuttle's external fuel tank. Heated gaseous nitrogen is pumped into the hood to warm the liquid oxygen vent system at the top of the external tank. This prevents vapors at the vent opening from condensing into ice that could dislodge and damage the orbiter during launch. The vent system arm is 24.4 meters (80 feet) long, 15 meters (5 feet) wide, and 2.4 meters (8 feet) high. The diameter of the vent hood is 4 meters (13 feet). The arm is attached to the Fixed Service Structure between the 63.1-meter (207-foot) and 69.2-meter (227-foot) levels. The arm and its hood can be retracted in about one minute and 30 seconds. They are in the fully retracted position at approximately 45 seconds prior to launch.
The External Hydrogen Vent Line Access Arm provides a means of mating the external tank umbilicals to the pad facilities, and provides work access to the tank area. This arm retracts several hours before launch, leaving the umbilicals attached. At the moment the solid rocket boosters ignite, these umbilicals eject from the Shuttle and fall back against the tower, where they are protected from engine flame by a curtain of sprayed water. This arm is 15 meters (48 feet) long, and attached at the 51-meter (167-foot) level .
The Rotating Service Structure provides access to the orbiter for installation and servicing of payloads at the pad. It pivots through one third of a circle, from a retracted position well away from the Shuttle to the point where its payload changeout room doors meet and match the orbiter cargo bay doors. It rotates around a vertical hinge attached to one corner of the Fixed Service Structure. Most of its body is some 18 meters (59 feet) above the pad, supported by the hinge and a structural framework on the opposite end. This framework rests on two eight-wheel motor-driven trucks, which ride on rails installed within the pad surface. The rotating body is 31 meters (102 feet) long, 15 meters (50 feet) wide, and 40 meters (130 feet) high.
The primary purpose of the Rotating Service Structure is to receive Space Shuttle payloads while in the retracted position, rotate, and install them in the orbiter cargo bay. With the exception of the Spacelab and other large horizontal payloads, which are loaded while the orbiter is in the Orbiter Processing Facility, all spacecraft are loaded into the Shuttle at the pad. The payload changeout room provides an environmentally clean or "white room" condition in which to receive payloads from their protective transportation canisters, and maintains this cleanliness by never exposing the spacecraft to the open air during the transfer operations.
In operation, a canister is hoisted to the proper elevation in the retracted Rotating Service Structure and locked into position. The environmental seals in the Rotating Service Structure are inflated against the sides of the canister. The space between the closed doors of the Rotating Service Structure and the canister are purged with clean, temperature and humidity-controlled air, after which the doors may be opened. The payload is then transferred from the canister into the Rotating Service Structure, the canister and Rotating Service Structure doors are closed, the environmental seal is deflated, and the canister is lowered to its transporter to be taken off the pad. The Rotating Service Structure rolls into position to enclose the orbiter's payload bay, reestablishing the environmental seals and clean air purge. The Rotating Service Structure and payload bay doors are then opened so that the payload may be installed.
A Weather Protection System at Pads A and B shields the orbiter from windblown debris, heavy rains and hail that could damage the craft's fragile heat protection tiles. A considerable portion of the orbiter is shielded by the Rotating Service Structure and its attached Payload Changeout Room which closes in around the vehicle while on the pad. The Weather Protection System fills in the gaps.
Protection for the lower portion of the orbiter is provided by metal doors that slide together between the orbiter's belly and the external tank. The doors, measuring up to 16 meters (53 feet) long, 11.6 meters (38 feet) tall and weighing up to 21 metric tons (46,000 pounds), are connected to the Rotating Service Structure and the Fixed Service Structure. The doors move together from opposite sides on wheeled flanges that ride on steel beams. The top of the orbiter is protected by an inflatable seal that extends from the Payload Changeout Room, forming a semicircle covering 90 degrees of arc between the vehicle and the external tank. A series of 20 or more bifold metal doors, about 24.4 x 1.2 meters (80 x 4 feet) in size, fold out from the Payload Changeout Room on the Rotating Service Structure to cover the side areas between the external tank and the orbiter.
The Flame Deflector System protects the vehicle and pad structures from the intense heat of launch. It is located in the ground level flame trench that bisects the hardstand. A flame deflector functions by presenting an inverted V-shape to the flames pouring into the trench through openings in the Mobile Launcher Platform. Both sides of the upside-down V curve out near the bottom until they are almost horizontal. Flames follow these curves and are deflected horizontally down the flame trench, rather than bouncing back up to envelop the vehicle.
The flame trench divides the hardstand lengthwise from ground level to the pad surface. It is 149 meters (490 feet) long, 18 meters (58 feet) wide, and 12 meters (40 feet) high. At launch, flames shoot out both ends of the trench into the air. The deflector for the Space Shuttle is actually a two-in-one device, where one side of the inverted V receives the flames from the orbiter's main engines, and the opposite side the flames from the two solid rocket boosters. It is fixed near the center of the trench, and extends completely across it. The orbiter and booster deflectors are built of steel and covered with an ablative material about 13 centimeters (five inches) thick that flakes off to shed heat. They weigh over 453,592 kilograms (one million pounds) each.
In addition to the fixed deflectors, there are two movable ones located at the top of the trench, for additional protection from the solid rocket booster flames.
The Slidewire System provides an escape route for the astronauts and closeout crew until the final 30 seconds of countdown. Five slidewires extend from the Fixed Service Structure at the Orbiter Access Arm level down to the ground. A flat-bottom basket made of steel wire and heat resistant fiber is suspended from each of five wires and positioned for entry in event of emergency. Each basket can hold two persons. The basket slides down a 366-meter (1,200 foot) wire to a bunker located west of the Fixed Service Structure. The descent takes approximately 35 seconds and is controlled by a friction brake between the basket and the wire.
The Lightning Mast extends above the Fixed Service Structure and provides a "cone of protection" over the vehicle and pad structures. The 24-meter (80-foot) tall fiberglass mast is grounded by a cable which starts from a ground anchor 335 meters (1,100 feet) south of the Fixed Service Structure, angles up and over the lightning mast, then extends back down to a second ground anchor the same distance to the north. The mast functions as an electrical insulator, holding the cable away from the tower. The mast with its accompanying support structure extends 30 meters (100 feet) above the Fixed Service Structure.
A Sound Suppression Water System has been installed on the pad to protect the orbiter and its payloads from damage by acoustical energy reflected from the Mobile Launcher Platform during launch. The Shuttle orbiter, with its payloads in the cargo hold, is much closer to the surface of the Mobile Launcher Platform than was the Apollo spacecraft at the top of a Saturn V or Saturn IB rocket.
The sound suppression system includes an elevated water tank with a capacity of 1,135,550 liters (300,000 gallons). The tank is 88 meters (290 feet) high and is located on the northeast side of the pad. The water is released just prior to ignition of the Shuttle engines, and will flow through 2.1-meter (seven-foot) diameter pipes for about 20 seconds. Water pours from 16 nozzles atop the flame deflectors, and from outlets in the main exhaust hole in the Mobile Launcher Platform. By the time the solid rocket boosters ignite, a torrent of water will be flowing onto the Mobile Launcher Platform from six large quench nozzles, or "rainbirds," mounted on its surface.
The rainbirds are 3.6 meters (12 feet) high. The two in the center are 107 centimeters (42 inches) in diameter; the other four have a 76 centimeter (30-inch) diameter. The peak rate of flow from all sources is 3,406,500 liters (900,000 gallons) of water per minute at nine seconds after liftoff.
Acoustical levels reach their peak when the Space Shuttle is about 91 meters (300 feet) above the platform, and cease to be a problem at an altitude of about 308 meters (1,000 feet).
Part of the Sound Suppression Water System is the Solid Rocket Booster Overpressure Suppression System. It alleviates the effect of a reflected pressure pulse which occurs at booster ignition. This pressure, without the suppression system, would exert significant forces on the wings and control surfaces of the orbiter.
There are two primary components to the system. A water spray system provides a cushion of water which is directed into the flame hole directly beneath each booster. This is supplemented by a series of water "hammocks" stretched across each hole, providing a water mass to dampen the reflected pressure pulse. Used together, this water barrier blocks the path of the reflected pressure wave, greatly decreasing its intensity.
In the event of an aborted mission, a Post-Shutdown Engine Deluge System is used to cool the aft end of the orbiter. It also controls the burning of residual hydrogen gas after the Shuttle's main engines have been shut down with the vehicle on the pad. There are 22 nozzles around the exhaust hole for the main engines within the Mobile Launcher Platform. Fed by a 15.2 centimeter (6-inch) diameter supply line, water flows at a rate up to 9,460 liters (2,500 gallons) per minute.
Propellant Storage Facilities are located at both pads. Liquid oxygen, used as an oxidizer by the orbiter's main engines, is stored in a 3,406,500-1iter (900,000gallon) tank located at the northwest corner of each launch pad. This ball-shaped vessel is a huge vacuum bottle which is designed to maintain the supercold temperatures of cryogenic propellants.
Liquid oxygen is transferred from the storage tank to the orbiter's external tank before flight by two pumps which supply 37,850 liters (10,000 gallons) per minute each.
The liquid hydrogen fuel for the orbiter's main engines is stored in a similar 3,218,250-liter (850,000-gallon) ball-shaped vessel located at the northeast cornel of the pads.
Pumps are not required to move the liquid hydrogen from the storage tank to the orbiter's external tank during fueling operations. A small amount of liquid hydrogen is allowed to vaporize. This creates a gas pressure in the top of the tank that moves the extremely light fuel through the transfer lines.
The vacuum-jacketed transfer lines carry the supercold propellants to the Mobile Launcher Platform, where they are fed from the Tail Service Masts through the orbiter into the external tank.
Hypergolic Propellants used by the orbiter's Orbital Maneuvering Engines and Attitude Control Thrusters are also stored at the pad in well-separated areas. The fuel, monomethylhydrazine, is maintained in a facility located on the southwest corner of the pad area. Nitrogen tetroxide, an oxidizer, is stored in a similar facility located on the southeast corner. These propellants are fed by transfer lines to the Fixed Service Structure and continue to the Rotating Service Structure's Hypergolic Umbilical System, by which they are attached to the orbiter.