As Apollo moved into high gear, NASA began to look at the directions space programs of the future might take. On Sept. 15, 1969, a Space Task Group appointed by President Nixon recommended broad outlines for the next 10 years of space exploration. Among the options was the concept of a reusable Space Shuttle, which offered major advantages over conventional rocket systems. It would be reusable for up to 100 or more missions. Moreover, spacecraft built to fly aboard a Shuttle vehicle could be designed with more emphasis an their mission capabilities, and less emphasis on their ability to withstand the rigors of conventional rocket launches. In addition, studies indicated a reusable Space Shuttle would require the least capital risk per flight, offer the lowest technical risk in development and provide the highest rate of return on the government's investment. The U.S. Air Force, which had been actively involved with Shuttle planning and which would also participate in
Shuttle missions, agreed with this judgment.
The design for the new Space Shuttle vehicle called for three attached main elements: an obiter, which carries astronauts and payloads into orbit; an external propellant tank; two unmanned solid rocket boosters. The boosters burn in unison with the orbiter's three main engines, providing the primary thrust to get the Shuttle off the ground. The propellant in the two boosters burns out about 29 miles (47 kilometers) above Earth. At that time, the booster casings separate from the orbiter and fall into the sea, their descent being slowed by parachutes. Specially equipped ships in the recovery area retrieve the floating casings and parachutes. The casings are then towed back to the launch area for refurbishment and reuse.
To save space and weight on the orbiter, the tanks for the propellants which power its engines are not part of its fuselage. Instead, the design incorporates a large external tank, divided to hold both the liquid hydrogen and the liquid oxygen-a total of more than 1,577,000 pounds (715,300 kilograms) of propellants. The tank is jettisoned over a remote part of the ocean just before the orbiter enters orbit. It is not recovered.
The 122-foot (37-meter) long orbiter, about the size of a DC-9 jetliner, continues on its Earth-orbital mission for a period of three to 10 days. It then re-enters the atmosphere, and like an enormous glider, makes an unpowered landing on a runway. Then the orbiter is refurbished, assembled with refurbished boosters and a new external tank and checked out for a new mission. Orbiters are designed to fly up to 100 missions, solid rocket casings for 20 or more missions.
The Shuttle concept represents a whole new way of space flight. On a standard mission, it carries up to seven crew members, only three of whom need be NASA astronauts. The others can be payload specialists, usually technicians, engineers or scientists, who make observations and conduct experiments. For rescue missions, the orbiter's cabin holds as many as 10 persons; this means that an orbiter with a basic three-man crew can rescue all occupants of a disabled orbiter.
The orbiter's cargo bay measures 60 feet (18 meters) by 15 feet (5 meters) and carries up to about 55,000 pounds (24,948 kilograms) of payload, but because of constraints imposed should a mission have to be aborted and the orbiter return to Earth still carrying its cargo, the maximum payload capability is capped at about 50,000 pounds (22,680 kilograms).
Multiple payloads (up to five satellites) may be carried in the cargo bay. Fully equipped laboratories, where experimenters work in a shirt-sleeve environment, can also be accommodated. Specialists can repair damaged satellites already in orbit, or, if necessary, return the satellites to Earth for a major overhaul. For missions requiring higher orbits than the orbiter's maximum altitude of about 500 miles (805 kilometers), a small solid rocket stage is attached to the satellites carried aboard. After being unloaded and checked out in space, the solid rocket is used to boost the satellite into the higher orbit. Likewise, interplanetary spacecraft or deep space probes are accelerated into their trajectories by this procedure.
Once it enters Earth orbit, the orbiter uses small rocket engines in its orbital maneuvering system to adjust its path, to facilitate rendezvous operations, and, at the completion of orbital operations, to slow down for re-entry into the atmosphere.
A reaction control system containing small thruster rockets provides the Shuttle orbiter with attitude control in space, and precision velocity changes for the final phases of rendezvous and docking or orbit modification. Used in conjunction with the aerodynamic control surfaces, it provides attitude control during re-entry.
The orbiter does not follow a ballistic path to the ground like previous manned spacecraft. It "pancakes" into the Earth's upper atmosphere with its nose pointed up at a steep angle. At lower altitudes, the orbiter goes into a more nearly horizontal flight for an aircraft-type approach and landing. The orbiter has a cross-range capability (can maneuver to the right or left of its planned entry path) of about 1,270 miles (2,044 kilometers). Landing speed is about 215 miles (346 kilometers) per hour.
The orbiter touches down like an airplane, on runways at either Kennedy Space Center or the Dryden Flight Research Facility in Edwards, Calif.
At KSC, the orbiter lands on a 15,000-foot (4.6-kilometer) runway. Located northwest of the Vehicle Assembly Building, the Shuttle Landing Facility has a northwest-southeast alignment. This airstrip, one of the world's largest, is 300 feet (91 meters) wide and has a 1,000-foot (305-meter) safety overrun at each end. A microwave beam landing system guides the orbiter to a landing. An extremely sophisticated and accurate system is necessary because the orbiter makes a "dead-stick" approach to the runway; that is, it has no flight power system on board for landing. It is, in effect, a glider at this point. In the unlikely event of a missed approach, it cannot circle the strip and try a second time.
During re-entry, crew members experience a designed maximum gravity load of less than 1.5 Gs; during launch it reaches only 3 Gs. (These accelerations are about one-third the levels experienced on Apollo flights.) Because of the low G force and various other features, such as a standard sea-level atmosphere, most persons in good health can safely ride aboard the orbiter.
A fleet of four operational orbiters, with all associated hardware, is projected for the Space Shuttle program. Budget considerations and launch rates, however, will determine the final number of orbiters.
The first orbiter to be constructed was named the "Enterprise," after the flagship in the popular television series, "Star Trek." Designed as an atmospheric test vehicle, it was used for the Shuttle approach and landing tests conducted in 1977 at NASA's Dryden Flight Research Facility in California. During the tests the Enterprise was carried atop a modified Boeing 747 carrier aircraft for a series of low-altitude flight tests to verify the aerodynamic and flight control characteristics of the orbiter's design.
During the initial test flights, the Enterprise was unmanned and remained aboard the 747 from takeoff through landing. The next step was a series of manned captive flights. For the final series, NASA astronaut-pilots fired explosive bolts to release the orbiter from the 747, and flew it to an unpowered landing several minutes later. All tests were successfully completed ahead of schedule in October 1977.
Following the approach and landing test program, Enterprise was shipped to Marshall in Huntsville, Ala., for ground vibration tests. The whole configuration-orbiter, external tank, and solid rocket boosters-was tested to see how it could withstand the stresses incurred at launch. Following these tests, the Enterprise was ferried to the Kennedy Space Center where it was used as a facilities verification vehicle.
The second orbiter built was named the "Columbia," after the American Naval vessel that circumnavigated the globe in the 18th century. The first orbiter scheduled for space flight, Columbia was delivered to Kennedy in March 1979, and began flight processing for its first launch, which occurred April 12, 1981 (see next chapter). By the end of 1985, three more orbiters had arrived at Kennedy: Challenger, Discovery, and Atlantis. Challenger was destroyed during a launch failure in 1986, and will be replaced by Endeavour, scheduled to arrive at KSC in 1991.
As the Space Shuttle concept was being developed, NASA assigned areas of program responsibility to its Centers. KSC was given the responsibility for designing ground support facilities and systems for the Shuttle. The Johnson Space Center became lead center for the Shuttle program and was responsible for designing and procuring the orbiter. The Marshall Space Flight Center was charged with design and procurement of the external propellant tank, the three main engines of the orbiter, and the solid rocket boosters.
Just two days before the launch of Apollo 16 on April 14, 1972, Dr. George M. Low, acting NASA administrator at the time, announced that KSC would be the initial launch site for the Shuttle. The Department of Defense later was authorized to construct a second site at Vandenberg Air Force Base in California, to handle launches into polar orbits (across the North and South Poles). However, the 1986 Challenger accident and subsequent hiatus in Shuttle launches resulted in the moth-balling of the California facilities.
KSC's future for manned missions was assured. Many of the same structures originally constructed and equipped for Apollo would serve for the Shuttle in their present configuration; others required varying degrees of modification. Soon after the official announcement, KSC geared up to build the Shuttle Landing Facility and other facilities unique to the needs of Shuttle operations. Ground-breaking ceremonies for the three-mile (4.8-kilometer) runway took place in April 1974.
With a view to keeping costs down, planners took full advantage of existing structures and scheduled new construction only when a unique requirement existed. One of the first major new buildings was the Orbiter Processing Facility, located in the heart of Complex 39. It connects with the Shuttle Landing Facility and the nearby Vehicle Assembly Building by tow ways similar to aircraft taxiways.
The Orbiter Processing Facility is essentially a hangar with two high bays in which orbiters undergo "safing" and servicing after landing. It is here in a "clean-room" environment that the propellant feedlines are drained and purged and explosive actuators removed. Next, flight and landing systems are refurbished, returned payloads are removed, and the payload bay support equipment is inspected and refurbished. If the payload scheduled for the next mission is to be installed horizontally, it will be placed in the orbiter while it is in the hangar. (Other payloads of the vertical-placement type are installed in the cargo bay after the vehicle is in position on the launch pad.)
Two orbiters in parallel flow can be handled in the Orbiter Processing Facility. In 1987, a third orbiter processing facility was opened nearby. The Orbiter Modification and Refurbishment Facility has a high bay of the same dimensions as the two in the Orbiter Processing Facility, but at present only non-hazardous work can be performed here. NASA plans to upgrade the Orbiter Modification and Refurbishment Facility to allow total orbiter checkout like that conducted in its sister hangars.
Because Shuttle vehicles differ significantly in size and shape from previous manned space vehicles, a technological "face-lift" was undertaken to prepare some existing structures for their new roles. Modifications in the Vehicle Assembly Building included major changes to High Bays 1 and 3 to equip them for the assembly and checkout of complete Space Shuttles. Work platforms had to be reshaped to fit the Shuttle configuration.
The other two High Bays, 2 and 4, required internal structural changes to accommodate one vertical storage cell and one checkout cell apiece. The 154-foot (47-meter) Shuttle external tank, shipped by barge from Louisiana, is brought here.
A low bay checkout cell was converted into an enclosed, environmentally controlled workshop where orbiter main engines are received and inspected, The workshop also serves as a support facility for all main engine operations at the Center.
In addition, the north door of the huge assembly building was widened 40 feet (12.2 meters) to accommodate the 78-foot (24-meter) wingspan of the orbiter as it is towed into the building prior to assembly with other Shuttle elements. The widest stage of the Saturn V was 33 feet (10 meters) in diameter.
Two of the four firing rooms in the adjacent Launch Control Center were equipped with consoles, computers and associated equipment that are one element of the Launch Processing System. This advanced system performs much of the checkout of the Space Shuttle vehicle while the vehicle components are being processed for launch. It was especially developed at KSC for the Shuttle program. With the Launch Processing System, the final countdown for the Shuttle was compressed from the 28 hours needed for an Apollo launch to three hours.
The Apollo launch pads at Complex 39 also underwent major changes. All the structures on the surface of the pads were removed with the exception of the six fixed pedestals at each pad. For previous manned missions, these pedestals were used to support a mobile launcher holding an Apollo-Saturn vehicle. The same pedestals hold the modified mobile launcher platforms on which Shuttle vehicles are assembled.
The most obvious change to the mobile launchers used for previous Saturn vehicle launches is the absence of each launcher's 380-foot (116-meter) tall umbilical tower with its nine swing arms and large crane. The upper portions of the umbilical towers were dismantled and installed at the pads to serve as fixed service structures. A rotating service structure was built at each pad to provide an environmentally controlled Payload Changeout Room for inserting vertically handled payloads in the orbiter payload bay. Mounted on semicircular rails, this structure swings away from the vehicle prior to launch to prevent heat and blast damage.
Another change in the mobile launcher platforms is the replacement of the one large hole formerly at the center of each platform with three smaller openings, which separately accommodate the liftoff flames and hot exhaust gases emitted from the orbiter's three engine cluster and the two boosters.
In 1986, another new facility was activated in the Complex 39 Area. The Solid Rocket Booster Assembly and Refurbishment Facility became the refurbishment and subassembly site for non-propellant booster hardware -- primarily the forward and aft assemblies -- initially performed in the Vehicle Assembly Building. NASA's Marshall Space Flight in Huntsville manages the Assembly and Refurbishment Facility.
Completed aft skirt assemblies of solid rocket boosters are transported Rotation, Processing and Surge Facility, another Shuttle era facility. This set of Complex 39 buildings is also the receiving point for new or reloaded booster segments from Utah. The aft skirt assemblies are integrated with the booster aft segments, and along with other booster segments, are then transported to the Vehicle Assembly Building for stacking and integration with other flight-ready booster components.
A number of structures and buildings in the Industrial Area to the south and nearby Cape Canaveral Air Force Station also were modified for Space Shuttle operations. For example, the Cape-side Hangar AF first used during the Gemini program now serves as the Solid Rocket Booster Disassembly Facility, the receiving point for the two spent solid rocket boosters. After preliminary safing, the nose cone, frustum and aft skirt of each booster are removed and taken to Launch Complex 39 facilities for further processing.
The booster casings are disassembled into their major pieces and cleaned. The casings are then carried by truck to railroad cars and shipped to the manufacturer's plant in Utah, to be reloaded with propellant.
Some buildings and hangars at Cape Canaveral receive, assemble and check out payloads that are to be vertically integrated into the orbiter. These payloads, primarily automated satellites or spacecraft with attached stages, are then processed through one of two explosive-safe areas, also on the Cape.
These payloads are next brought over to the Vertical Processing Facility in the Industrial Area. This building, formerly used to encapsulate payloads in the nose cones of their expendable space vehicles, is now the site where two or more spacecraft and attached solid motors are integrated into a single Shuttle cargo package. Assembled payloads are inserted into a canister, which has interior dimensions that duplicate those Of the orbiter's cargo bay. The canister is then sealed and transported to the pad. At the rotating service structure, the canister is hoisted and locked into position at the payload changeout room. The payload is then moved into the room, and the canister disconnected and lowered. The rotating service structure then swings around until it fits flush with the cargo bay of the orbiter. The payloads are then moved into the orbiter. Throughout this series of transfers, the payloads remain under "clean room" conditions.
Another Industrial Area facility converted for Shuttle operations is the Parachute Refurbishment Facility. This building was originally used to process parachutes for the Gemini manned space program, and was also used for a time as the KSC News Center during the Apollo program. Now it is the processing facility for the parachutes which slow the solid rocket boosters' descent into the Atlantic Ocean. The parachutes are washed, dried and prepared for reuse, and, along with new ones, stored until needed.
The nearby Hypergolic Maintenance and Checkout Facility was modified to process and store components of the Shuttle orbital maneuvering system and reaction control system. A Launch Equipment Test Facility, located at the Marshall Center during the Apollo program, was moved to KSC and then modified for Shuttle testing.
The Operations and Checkout Building, also in the Industrial Area, was originally designed for the assembly and checkout of Apollo spacecraft modules. It was converted to process Shuttle payloads which are integrated in a horizontal mode. It is used primarily for processing Spacelab, a scientific laboratory built by the European Space Agency (ESA). Spacelab and other payloads of this type are installed in the orbiter's cargo bay in the Orbiter Processing Facility.
The reusable Spacelab was developed as a modular concept so that its configuration can be varied according to specific mission requirements. Enough modules exist to keep two complete Spacelabs in continuous flow. One of a Spacelab's two principal components is a pressurized module which provides a laboratory where experimenters can work in ordinary clothing. The module is segmented to permit additional flexibility in size. It is connected to the orbiter's pressurized cabin by a tunnel. Payload specialists for Spacelab operations eat and sleep in the orbiter's cabin throughout the mission. Each Spacelab module is designed for at least 50 trips into space.
The second major element of a Spacelab is an open pallet that exposes materials and equipment directly to space. Five pallet segments are available, each 10 feet (three meters) long. The pallets are designed for large man-directed instruments that require direct exposure to space or broad fields of view. Such equipment includes telescopes, antennas and various types of sensors.
A Spacelab is transported into orbit by the Space Shuttle for missions lasting seven to 10 days. It remains inside the cargo bay of the orbiter throughout that time.
After a mission, the Spacelab is removed from the orbiter's cargo bay and returned to the Operations and Checkout Building. The experiments are removed for detailed analysis, a preliminary analysis having been done in flight. The Spacelab is then refurbished and readied for its next mission. In the interval, a second Spacelab may be launched if required.
ESA, under terms of an agreement with NASA, assumed responsibility for designing, developing, manufacturing, testing and delivering to NASA a Spacelab engineering model and a flight unit, plus ground support equipment and spare parts. NASA agreed to purchase one additional Spacelab and more if needed. Nations cooperating in the Spacelab program are: West Germany, Italy, France, the United Kingdom, Belgium, Spain, The Netherlands, Denmark, Switzerland, and Austria. NASA, which worked closely with ESA during all phases of Spacelab's development and production, has the responsibility for Spacelab operations.
In addition to the 10 Western European nations participating in the Spacelab project, the international flavor of the Shuttle program is further demonstrated by the orbiter's payload handling system. This system was designed and produced by a Canadian industrial team. The Remote Manipulator System deploys and retrieves payloads in orbit, using a 50-foot (15-meter) hinged arm -- sometimes called the "Canadarm" -- attached to the front of the payload bay. A second arm can be installed if needed. Each arm has remotely controlled television cameras, and lights that provide side viewing and depth perception.
The selection of potential new astronauts, the completion of initial flight tests of the orbiter, the production of other Shuttle elements and support equipment, the modification and construction of facilities and the development of a management team -- all heralded the start of a new era in space operations.
This era began some two decades after the first U.S. venture into space--the launch of the 30.8-pound (14-kilogram) satellite, Explorer 1, on Jan. 31, 1958. Since then, unmanned spacecraft have probed the near and far reaches of space. Manned spacecraft have explored the lunar surface as well as expanded the existing knowledge of the Earth, the Sun, and the adaptability of people to extended flight in Earth orbit. The wealth of experience and knowledge gained from the accomplishments led to the development of the Shuttle.
With its versatility and reusability, the Space Shuttle is expected to open wide the doors to long duration exploration of space. A major step along this new path was taken April 12, 1981, with the first launch of the Space Shuttle.