The Marshall Space Flight Center is responsible for the space shuttle main engines, the external tank and the solid rocket boosters. It is also responsible for Spacelab, the reusable, modular scientific research facility that is carried in the payload bay of the orbiter, and managing Spacelab missions. Marshall also has management responsibility for the Hubble Space Telescope, tethered satellite system and orbital maneuvering vehicle and has a substantial role in the development of the space station.
Two other sites are managed by Marshall: the Michoud Assembly Facility in New Orleans, La., which manufactures the shuttle external tank, and the Slidell Computer Complex in Slidell, La., which provides computer services to the Michoud facility.
The Rocketdyne Division of Rockwell International in Canoga Park, Calif., is responsible to the Marshall Space Flight Center for the design, development, manufacture, test and assembly of the space shuttle main engines. The Rocketdyne facility at Santa Susana, Calif., is also used for the space shuttle main engines.
Martin Marietta is responsible to Marshall and uses the Michoud facility at New Orleans for the design, development, manufacture, test and assembly of the external tank.
Morton Thiokol's Wastach Division at Brigham City, Utah, is responsible to Marshall for the design, development, test and assembly of the solid rocket booster motors. After each shuttle mission the solid rocket booster motor casings are recovered and returned to Thiokol's Wastach Division for refurbishment.
United Space Boosters Inc. Production Company in Florida is responsible to Marshall for solid rocket booster assembly, checkout and refurbishment involving non-solid-rocket-motor components and for solid rocket motor integration.
The Payload Operations Control Center allows users on the ground to support and interact with onboard mission activities and permits direct communication between the investigator on the ground and flight crew on orbit. It provides ground command capability to operate experiments, manage payload resources and operate payload support equipment. Its facilities and services for instrument monitoring and control are made available to all users who request them. Each user area has a standard set of support equipment and space for special instrument-dedicated ground support equipment. A communication link can be arranged to allow the investigator to perform some or all operations from his own institution.
The facilities and services for instrument monitoring and control are provided within designated user areas. Investigators are concerned primarily with the user rooms, where they monitor and control their instruments. Standard equipment and services for each user room include TV monitors, a digital data monitor, intelligent terminals, strip chart recorders, communication panels, an interface data panel for data outputs to experiment ground support equipment, and miscellaneous carry-in monitors and recorders for voice and video. Space is available in each user support area for experimenters to set up their own special processing equipment in addition to the services provided by the POCC. The investigator has the additional option of operating out of his home institution by arranging for a communications link with the POCC. Investigators are responsible for defining their requirements for POCC use early in the mission cycle.
Training requirements depend on the complexity of both the individual instruments and the integrated payload. The investigator helps determine training requirements for his instrument and participates in training the payload specialists and support personnel who may operate equipment, monitor data or assist in troubleshooting. Investigators who participate in such activities also require indoctrination and training in practices and equipment operation. Payload crew training currently begins 1.5 to two years before launch and continues through launch. Training on individual experiments and experiment instruments is normally scheduled before payload integration, which begins approximately one year before launch.
Specific operational and support responsibilities for the space shuttle and its science payloads are assigned to several NASA field centers, a number of which have Spacelab training facilities. Training on experiment engineering models and flight hardware may also take place at the principal investigators' facilities.
The mission management team works to ensure that the mission scenario meets the needs of the investigators, that the requirements of the scientific payload match the shuttle-Spacelab resources and that all systems and instruments operate properly during flight. The team also conducts crew training in payload operation and prepares the science teams for their roles in the Payload Operations Control Center during the mission.
Marshall Space Flight Center's responsibility for integrated mission-dependent training required the development of the Payload Crew Training Complex. This training facility houses host computers, development peripherals, simulation director stations, mockups of the Spacelab pressurized modules, Spacelab pallet mockups, an orbiter aft flight deck mockup and other simulators to support the command and data management subsystem and experiments. The host simulator provides hardware and software to represent space CDMS operation, pointing system operation and the general Spacelab environment. Experiment simulators provide software experiment models that interface with the host simulator.
The Spacelab simulator facility at the Johnson Space Center consists of a full-scale, high-fidelity Spacelab core and experiment module segment; subsystem racks; controls and displays; scientific airlock; and viewport. It uses the shuttle mission simulator computer complex to process simulation data. It does not include the tunnel area or any experiments. The Spacelab simulator provides full-task training in the operation of Spacelab support subsystems for pilots and mission and payload specialists.
The Kennedy Space Center plans and manages the ground processing of cargoes for integration in the orbiter. This typically includes receiving and preintegration checkout of experiments and test equipment, physical integration of user science instruments with the carrier, verification of the integrated payload, loading of payloads into the orbiter and final preflight validation of the integrated mission vehicle and ground systems. In most cases, payload integration and checkout require the investigator's presence.
Although designated primarily as payload integration and test areas of the Kennedy Space Center Operations and Checkout Building, both the Level IV area and the cargo integration test equipment stand contain detailed simulators of the orbiter aft flight deck (payload, on-orbit and mission stations). With their direct physical access to payload equipment, these aft flight deck simulators provide a final training opportunity during the Spacelab integration cycle for mission and payload specialists to act as test operators with flight hardware and maintain proficiency with integrated payload operations.
Throughout the 1970s, the role of the laboratory complex-directly under NASA Headquarters-expanded. The federal/state facility now services more than a score of government agencies and dozens of programs in development and testing.
At the eastern boundary of the main facility and at the end of the main canal is the huge test stand complex where the Saturn S-IC stage was test-fired. The space shuttle main propulsion system tests, also conducted at this complex, included firing of the three main engines. (Rockwell International's Space Transportation Systems Division in Downey, Calif., under the management of the Marshall Space Flight Center, conducted the testing.)
Approximately 1.5 miles west are two stands- A-1 and A-2- that are used to test the space shuttle main engines separately. The engines are built by Rockwell's Rocketdyne Division in Canoga Park, Calif., under the management of Marshall Space Flight Center. The test stands were also used in the 1960s and early 1970s to test the Rockwell-built Saturn S-II stages.
The main propulsion system test program consisted of a series of cryogenic (supercold) tankings and static firings designed to integrate and evaluate performance of the entire system and to demonstrate the compatibility of all interfacing elements and subsystems. Full-duration firings of the space shuttle main engines were used to verify integrated system performance, investigate off-nominal conditions and assess design changes in the system. The series of tests certified the main propulsion system for the space shuttle's first flight.
The cryogenic propellants of the main propulsion system are liquid hydrogen fuel, which must be maintained at minus 423 F, and liquid oxygen oxidizer, which must be maintained at minus 297 F.
Hardware for the propulsion system testing was the main propulsion test article, which was given the Rockwell internal identification of MPTA-098. The test article consists of a spacecraft aft fuselage and a structural truss arrangement that simulates the spacecraft's midfuselage. The three space shuttle main engines were housed in the aft fuselage and the test article was connected to an external fuel tank. For ground test acoustic fatigue protection, the test article's aft fuselage consisted of a substitute covering in place of the reusable thermal protection system installed on the outer surface of the actual spacecraft.
The portion of the orbiter hydraulic system associated with main engine valve control and thrust vector control servoactuation for engine gimbaling was included in the aft fuselage. Ground support equipment supplied the hydraulic power in place of the orbiter auxiliary power unit and hydraulic system to position the hydraulic servoactuators for the main engine valve and thrust vector control. Also included in the aft fuselage was a flight purge, vent and drain system that operated during tankings and firings for aft compartment conditioning. One ground computer, a shuttle avionics test set, was used in place of the five onboard flight computers to control the avionics and monitor functions for the test.
The external tank was a complete flight-weight tank with auxiliary drain, vent and pressurization systems required for safety reasons. The structural connections between the external tank and the simulated spacecraft were flight hardware except that the pyrotechnic devices used for in-flight separation of the external tank from the spacecraft were not included.
The STDN controlled by the NCC at Goddard is composed of the White Sands Ground Terminal and NASA Ground Terminal, White Sands, N.M.; the NASA communications network, Flight Dynamics Facility, Simulation Operations Center, all at Goddard; and the ground network. These elements are linked by voice and data communications services provided by Nascom. The prime operational communications is by data formatted into 4,800-bit blocks and transmitted via the Nascom wide-band data and message switching system. Alternate communications are provided by teletype and facsimile facilities.
The Tracking and Data Relay Satellite system will consist of two Tracking and Data Relay satellites in geosynchronous orbit and 130 degrees apart (in longitude), an on-orbit spare, and ground terminal facilities located at White Sands. The TDRS is capable of transmitting to, receiving data from, and tracking a user spacecraft in a low Earth orbit for a minimum of 85 percent of its orbit.
The NSGT is colocated with the WSGT. The NSGT is managed and operated by the Networks Division and, in combination with Nascom, is NASA's physical and electrical interface with the TDRSS. The NSGT provides the interface to the common carrier, monitors the quality of the service from the TDRSS and remotes the data quality to the NCC.
Goddard's ground tracking stations are located at Ascension Island (S-band and UHF air-to-ground); Bermuda (S-band, C-band and UHF air-to-ground); Guam (S-band and UHF air-to-ground); Kauai, Hawaii (S-band and UHF air-to-ground); Merritt Island, Fla. (S-band and UHF air-to-ground; Santiago, Chile (S-band); Ponce de Leon, Fla. (S-band); Canberra, Australia (S-band); Dakar, Senegal (UHF air-to-ground); and Wallops, Va. (C-band).
Also supporting the STDN are several instrumented United States Air Force aircraft, referred to as advanced range instrumentation aircraft, which are situated, upon request, at various locations around the world where ground stations are unable to support space shuttle missions.
The various antennas at each STDN tracking station accomplish a specific task, usually in a specific frequency band. Functioning like giant electronic magnifying glasses, the larger antennas absorb radiated electronic signals transmitted by spacecraft in a radio form called telemetry.
The major switching centers in Nascom are located at Goddard; the Jet Propulsion Laboratory, Pasadena, Calif.; Cape Canaveral, Fla.; Canberra, Australia; and Madrid, Spain.
The Nascom Division, headquartered at the Goddard Space Flight Center, is responsible for providing an operational telecommunications network for all NASA programs and projects. The Nascom network is a worldwide complex of communications services, including data, voice, teletype and television systems that are a mixture of government-owned and leased equipment as well as leased services. Nascom is responsible for the operations, maintenance and testing required to provide optimum services to users.
This communications network is composed of telephone, microwave, radio, submarine cables and communications satellites. These various systems link data flow through 11 countries of the free world with 15 foreign and domestic carriers and provide the required information between tracking sites and the Johnson Space Center in Houston, Texas, and GSFC control centers. Special wide-band and video circuitry also is utilized as needed. The Goddard Space Flight Center has the largest wide-band system in existence.
Included in the equipment of the worldwide STDN system are numerous computers located at the different stations. The computers at these remote sites control tracking antennas, handle commands and process data for transmission to the Johnson Space Center and Goddard control centers. Data from the space shuttle from all the tracking stations around the world are funneled into the main switching computers at GSFC and are rerouted to JSC without delay via domestic communications satellites. Commands generated at JSC are transmitted to the main switching computers at GSFC and switched to the proper tracking station for transmission to the space shuttle.
If NASA's Johnson Space Center Mission Control Center should be impaired for an extended period of time, an emergency control center would be established at the NASA Ground Terminal, White Sands, N.M., and manned by NASA's JSC personnel.
A station conferencing and monitoring arrangement allows various traffic managers to ''conference'' as many as 220 different voice terminals throughout the United States and abroad with talk/listen capability at the touch of a few buttons. The system is redundant, which accounts for its mission support reliability record of 99.6 percent. All space shuttle voice traffic is routed through SCAMA at Goddard.
Communications satellites are used to connect the Earth stations electronically and permit 10 to 20 times more data to be transmitted. Ground terminals for domestic communications satellites are situated at JSC; Kauai, Hawaii; Goldstone, Calif.; the Kennedy Space Center. Florida; NASA's Ames Dryden Flight Research Facility, California; GSFC; and White Sands, N.M.
The tracking station at Ponce de Leon Inlet, Fla. (near New Smyrna Beach) provides support during powered flight due to attenuation problems from the solid rocket booster motor plume.
The existing worldwide ground stations cover up to approximately 20 percent of a satellite's or spacecraft's orbit. Coverage is limited to brief periods when the satellite or spacecraft is within the line of sight of a given tracking station.