Search NASA⌕ Search

SEARCH · Search NASA

Results for “process controls”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Status report and preliminary results of the spacecraft control laboratory experiment

The Spacecraft Control Laboratory Experiment (SCOLE) was conceived to provide a physical test bed for investigation of control techniques for large flexible spacecraft. The SCOLE problem is defined as two design challenges. The first challenge is to design control laws for a mathematical model of a large antenna attached to the space shuttle by a long flexible mast. The second challenge is to design and implement a control scheme on a laboratory representation of the structure modelled in the first part. Control sensors and actuators are typical of those which the control designer would have to deal with on an actual spacecraft. The primary control processing computer is representative of the capacity and speed which may be expected in actual flight computers. A brief description is given of the laboratory apparatus along with some preliminary results of structural dynamics tests and actuator effectiveness tests.

Williams, Jeffrey P.↗
NASA NTRS1987

Integration of communications and tracking data processing simulation for space station

A simplified model of the communications network for the Communications and Tracking Data Processing System (CTDP) was developed. It was simulated by use of programs running on several on-site computers. These programs communicate with one another by means of both local area networks and direct serial connections. The domain of the model and its simulation is from Orbital Replaceable Unit (ORU) interface to Data Management Systems (DMS). The simulation was designed to allow status queries from remote entities across the DMS networks to be propagated through the model to several simulated ORU's. The ORU response is then propagated back to the remote entity which originated the request. Response times at the various levels were investigated in a multi-tasking, multi-user operating system environment. Results indicate that the effective bandwidth of the system may be too low to support expected data volume requirements under conventional operating systems. Instead, some form of embedded process control program may be required on the node computers.

Lacovara, Robert C.↗
NASA NTRS1986

Thermal stability tests of CFRP sandwich panels for far infrared astronomy

An account is given of fabrication methods and low temperature figure tests for CFRP sandwich panels, in order to ascertain their applicability to ultralightweight 3-m aperture primary mirrors for balloon-borne sub-mm and far-IF telescopes that must maintain a 1-2 micron rms surface figure accuracy at -40 to -50 C. Optical figure measurements on the first two of a series of four 0.5-m test panels, replicated to a spherical surface, show a radius-of-curvature change and astigmatism down to -60 C; this approximately follows the composite's theoretical predictions and implies that material and process control is excellent, so that the large scale changes observed can be compensated for.

Hoffmann, W. F.↗
NASA NTRS1986

Dust and neutral gas modeling of the inner atmospheres of comets

This paper summarizes the present, preencounter understanding of the physical and chemical processes controlling the inner (r less than 1000 km) region of cometary atmospheres. Special emphasis was attached to compiling a self-consistent set of governing equations. This review is aimed at readers who want to understand the present status of the mantle and coma regions and/or who want to develop new, next generation models which will be needed as the large volume of new observational data will become available in the near future.

Gombosi, T. I.↗
NASA NTRS1986

The other side of the safety coin

The development, inspection and testing requirements for successful production and launch and safe operation of spaceflight hardware are discussed. Emphasis is placed on paying acute attention to malfunctions, which could be caused by contaminants (particles in docking rings), insufficiently durable materials (Orbiter brakes), etc. Generic and specific problems which occur in propulsion, avionics, mechanical and computer systems and in configuration management, manufacturing and process control efforts are explored. Case histories of deficiencies found in LOX fuel lines, contaminated hydraulic control systems, the Solar Maximum Mission thermal insulation grommets, are summarized. Thorough inspection and testing procedures and design change recording during manufacture of spacecraft components are identified as requisites for successful space missions.

Roth, Gilbert L.↗
NASA NTRS1987

Cosmic-ray propagation in the Galaxy and in the heliosphere - The path-length distribution at low energy

The energy dependence of the path-length distribution of cosmic rays at low energies, below relativistic velocities, is studied, and its implications for models of cosmic-ray confinement and propagation in the Galaxy and Galactic halo, including the effects of a possible Galactic wind, are studied. It is found that the mean free path in Galactic propagation must be fully energy-dependent, with the mean of an exponential path-length distribution increasing with increasing energy below 1 GeV per nucleon and decreasing with increasing energy above 1 GeV per nucleon. This indicates that, at low energies, diffusion is not the controlling process. The path-length distribution is not purely exponential but is depleted in short path lengths at low energies. This depletion is energy-dependent, being largest at low energies and decreasing with increasing energy.

Garcia-Munoz, M.↗
NASA NTRS1987

Cellular microstructure of chill block melt spun Ni-Mo alloys

Chill block melt spun ribbons of Ni-Mo binary alloys containing 8.0 to 41.8 wt pct Mo have been prepared under carefully controlled processing conditions. The growth velocity has been determined as a function of distance from the quench surface from the observed ribbon thickness dependence on the melt puddle residence time. Primary arm spacings measured at the midribbon thickness locations show a dependence on growth velocity and alloy composition which is expected from dendritic growth models for binary alloys directionally solidified in a positive temperature gradient. Microsegregation across cells and its variation with distance from the quench surface and alloy composition have been examined and compared with theoretical predictions.

Tewari, S. N.↗
NASA NTRS1986

Colloidal characterization of silicon nitride and silicon carbide

The colloidal behavior of aqueous ceramic slips strongly affects the forming and sintering behavior and the ultimate mechanical strength of the final ceramic product. The colloidal behavior of these materials, which is dominated by electrical interactions between the particles, is complex due to the strong interaction of the solids with the processing fluids. A surface titration methodology, modified to account for this interaction, was developed and used to provide fundamental insights into the interfacial chemistry of these systems. Various powder pretreatment strategies were explored to differentiate between true surface chemistry and artifacts due to exposure history. The colloidal behavior of both silicon nitride and carbide is dominated by silanol groups on the powder surfaces. However, the colloid chemistry of silicon nitride is apparently influenced by an additional amine group. With the proper powder treatments, silicon nitride and carbide powder can be made to appear colloidally equivalent. The impact of these results on processing control will be discussed.

Feke, Donald L.↗
NASA NTRS1986

Polymer precursors for ceramic composites

The fiber composite approach to reinforced ceramics provides the possibility of achieving ceramics with high fracture toughness relative to monolithics. Fabrication of ceramic composites, however, demands low processing temperatures to avoid fiber degradation. Formation of complex shapes further requires small diameter fibers as well as techniques for infiltrating the matrix between fibers. Polymers offer low temperature processability, control of rheology not available with ceramic powders, and should serve as precursors to matrix fibers. In recent years, a number of polysilanes and polysilezanes were investigated as potential presursors. A review of candidate polymers is presented, including recent studies of silsesquioxanes.

Hurwitz, Frances I.↗
NASA NTRS1987

Space Station services and design features for users

The operational design features and services planned for the NASA Space Station will furnish, in addition to novel opportunities and facilities, lower costs through interface standardization and automation and faster access by means of computer-aided integration and control processes. By furnishing a basis for large-scale space exploitation, the Space Station will possess industrial production and operational services capabilities that may be used by the private sector for commercial ventures; it could also ultimately support lunar and planetary exploration spacecraft assembly and launch facilities.

Kurzhals, Peter R.↗
NASA NTRS1987

A new approach to reliability estimation for reconfigurable systems

A new approach to computing the probability of failure for process-control systems that achieve reliability by redundancy and reconfiguration is described. This approach has three distinguishing characteristics. It is based on information about the components and the system that can be observed; it requires a minimum of information; and it fills the gaps by locating the redundant unit misbehavior pattern that produces the largest probability of system failure.

White, Allan L.↗
NASA NTRS1987

Primary arm spacing in chill block melt spun Ni-Mo alloys

Chill block melt spun ribbons of Ni-Mo binary alloys containing 8.0 to 41.8 wt pct Mo have been prepared under carefully controlled processing conditions. The growth velocity has been determined as a function of distance from the quench surface from the observed ribbon thickness dependence on the melt puddle residence time. Primary arm spacing measured at the midribbon thickness locations show a dependence on growth velocity and alloy composition which is expected from dendritic growth models for binary alloys directionally solidified in a positive temperature gradient.

Tewari, S. N.↗
NASA NTRS1988

Automated knowledge generation

The general objectives of the NASA/UCF Automated Knowledge Generation Project were the development of an intelligent software system that could access CAD design data bases, interpret them, and generate a diagnostic knowledge base in the form of a system model. The initial area of concentration is in the diagnosis of the process control system using the Knowledge-based Autonomous Test Engineer (KATE) diagnostic system. A secondary objective was the study of general problems of automated knowledge generation. A prototype was developed, based on object-oriented language (Flavors).

Myler, Harley R.↗
NASA NTRS1988

The meteorological measurement system on the NASA ER-2 aircraft

A Meteorological Measurement System (MMS) was designed for the high-altitude ER-2 aircraft (NASA 706). Through dedicated instrumentation installed on the aircraft and repeated calibrations, the MMS provides accurate in situ measurements of free-stream pressure, temperature, and the wind vector. The MMS has participated in two major high-altitude scientific expeditions, the Stratosphere-Troposphere Exchange Project (STEP) based in northern Australia and the Airborne Antarctic Ozone Experiment (AAOE) based in southern Chile. Key MMS subsystems are described. The MMS consists of a dedicated inertial navigation system (INS), a randome differential pressure system, a data acquisition system, and air data instrumentation. The MMS incorporates a high-resolution INS (Litton LIN-72RH model), which is specially configured and is updated at 25 Hz. The differential pressure system, consisting of two sets of pressure ports and transducers, is installed in the ER-2 radome to provide sensitive measurements of the airflow angles (angle of attack and angle of sideslip). The data acquisition system was designed to meet aircraft requirements of compactness and light weight (2 cu ft 50 lb) and for MMS requirements to sample, control, process, and store 45 parameters (some redundant) at a sampling rate up to 10 Hz. The MMS data are stored both in a tape recorder (20 MB) and a hermatically-sealed winchester hard disc (10 MB). Special and redundant instrumentation for temperature and pressure measurements were also installed on the aircraft.

Scott, Stan G.↗
NASA NTRS1988

An expert system for satellite and instrument data anomaly and fault isolation

A prototype Generic Payload Operations Control System (GPOCC) is being developed at the NASA Jet Propulsion Laboratory to provide a low-cost command and control processing center for science instruments and small payloads. The GPOCC supports the difficult transition from integration and test to flight operations. The prototype will incorporate four expert systems to perform telemetry, command, and mission planning functions as well as telecommunications scheduling. The first of these expert systems to be developed will perform telemetry data analysis and fault isolation, as well as propose corrective action. This Data Analysis Module (DAM) will monitor telemetry data and perform continual data monitoring and trend analysis based on a knowledge base and historic data archived on an optical disk storage device. The system maintains a continuous knowledge database of past system performance characteristics. The goal of the Data Analysis Module is to achieve consistent, dependable and validatable performance, to demonstrate thorough, reliable and fast reasoning, and to reduce the concentration demanded of flight analysis personnel.

Busse, Carl↗
NASA NTRS1986

The CAIS 2 Project

The Common APSE Interface Set (CAIS) is a proposed MIL-STD intended to promote the portability of Ada Programming Support Environment (APSE) tools written in Ada. The standardized interfaces define a virtual operating system, from which portable tools derive their basic services, e.g., file management, input/output, communications, and process control. In the Ada world, such a virtual operating system is called a Kernel Ada Programming Support Environment (KAPSE). The CAIS is a standardized interface between KAPSEs and tools. The CAIS has been proposed as a starting point for standard interfaces to be used in the NASA Software Support Environment (SSE) for the Space Station Program. The status of the CAIS standardization effort and plans for further development are described.

Legrand, Sue↗
NASA NTRS1988

Data systems

The Data Systems Program consists of research and technology devoted to controlling, processing, storing, manipulating, and analyzing space-derived data. The objectives are to provide the technology advancements needed to enable affordable utilization of space-derived data, to increase substantially the capability for future missions of on-board processing and recording and to provide high speed and high volume computational systems anticipated for missions such as the evolutionary Space Station and Earth Observing System. The Data Systems Program supports fundamental research in such areas as laser diodes, supports work to select and provide the appropriate on-board processor technology for future NASA missions, and also supports the development of two flight processors with special architectures.

Smith, Paul H.↗
NASA NTRS1989

Applications of fuzzy sets to rule-based expert system development

Problems of implementing rule-based expert systems using fuzzy sets are considered. A fuzzy logic software development shell is used that allows inclusion of both crisp and fuzzy rules in decision making and process control problems. Results are given that compare this type of expert system to a human expert in some specific applications. Advantages and disadvantages of such systems are discussed.

Lea, Robert N.↗