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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.

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At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Independent Orbiter Assessment (IOA): Assessment of the orbital maneuvering subsystem, volume 2

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the Orbital Maneuvering System (OMS) hardware and electrical power distribution and control (EPD and C), generating draft failure modes and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The IOA results were then compared to the proposed Post 51-L NASA FMEA/CIL baseline. This report documents the results of that comparison for the Orbiter OMS hardware and EPD and C systems. Volume 2 continues the presentation of IOA worksheets and contains the critical items list and the NASA FMEA to IOA worksheet cross reference and recommendations.

Haufler, W. A.↗
NASA NTRS1988

Independent Orbiter Assessment (IOA): Assessment of the reaction control system, volume 1

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the aft and forward Reaction Control System (RCS) hardware, and Electrical Power Distribution and Control (EPD and C), generating draft failure modes and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The IOA results were then compared to the proposed Post 51-L NASA FMEA/CIL baseline. This report documents the results of that comparison for the Orbiter RCS hardware and EPD and C systems. The IOA product for the RCS analysis consisted of 208 hardware and 2064 EPD and C failure mode worksheets that resulted in 141 hardware and 449 EPD and C potential critical items (PCIs) being identified. A comparison was made of the IOA product to the NASA FMEA/CIL baseline. After comparison and discussions with the NASA subsystem manager, 96 hardware issues, 83 of which concern CIL items or PCIs, and 280 EPD and C issues, 158 of which concern CIL items or PCIs, and 280 EPD and C issues, 158 of which concern CIL items or PCIs, remain unresolved. Volume 1 contains the subsystem description, assessment results, and some of the IOA worksheets.

Prust, Chet D.↗
NASA NTRS1988

Independent Orbiter Assessment (IOA): Assessment of the reaction control system, volume 2

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the aft and forward Reaction Control System (RCS) hardware and Electrical Power Distribution and Control (EPD and C), generating draft failure modes and potential critical items. The IOA results were then compared to the proposed Post 51-L NASA FMEA/CIL baseline. This report documents the results of that comparison for the Orbiter RCS hardware and EPD and C systems. Volume 2 continues the presentation of IOA worksheets.

Prust, Chet D.↗
NASA NTRS1988

Independent Orbiter Assessment (IOA): Assessment of the reaction control system, volume 3

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the aft and forward Reaction Control System (RCS) hardware and Electrical Power Distribution and Control (EPD and C), generating draft failure modes and potential critical items. The IOA results were then compared to the proposed Post 51-L NASA FMEA/CIL baseline. This report documents the results of that comparison for the Orbiter RCS hardware and EPD and C systems. Volume 3 continues the presentation of IOA worksheets.

Prust, Chet D.↗
NASA NTRS1988

Independent Orbiter Assessment (IOA): Assessment of the reaction control system, volume 4

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the aft and forward Reaction Control System (RCS) hardware and Electrical Power Distribution and Control (EPD and C), generating draft failure modes and potential critical items. The IOA results were then compared to the proposed Post 51-L NASA FMEA/CIL baseline. This report documents the results of that comparison for the Orbiter RCS hardware and EPD and C systems. Volume 4 continues the presentation of IOA worksheets and contains the potential critical items list.

Prust, Chet D.↗
NASA NTRS1988

Independent Orbiter Assessment (IOA): Assessment of the reaction control system, volume 5

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the aft and forward Reaction Control System (RCS) hardware and Electrical Power Distribution and Control (EPD and C), generating draft failure modes and potential critical items. The IOA results were then compared to the proposed Post 51-L NASA FMEA/CIL baseline. This report documents the results of that comparison for the Orbiter RCS hardware and EPD and C systems. Volume 5 contains detailed analysis and superseded analysis worksheets and the NASA FMEA to IOA worksheet cross reference and recommendations.

Prust, Chet D.↗
NASA NTRS1990

Induction motor control

Electromechanical actuators developed to date have commonly utilized permanent magnet (PM) synchronous motors. More recently switched reluctance (SR) motors have been advocated due to their robust characteristics. Implications of work which utilizes induction motors and advanced control techniques are discussed. When induction motors are operated from an energy source capable of controlling voltages and frequencies independently, drive characteristics are obtained which are superior to either PM or SR motors. By synthesizing the machine frequency from a high frequency carrier (nominally 20 kHz), high efficiencies, low distortion, and rapid torque response are available. At this time multiple horsepower machine drives were demonstrated, and work is on-going to develop a 20 hp average, 40 hp peak class of aerospace actuators. This effort is based upon high frequency power distribution and management techniques developed by NASA for Space Station Freedom.

Hansen, Irving G.↗
NASA NTRS1990

Aerospace induction motor actuators driven from a 20-kHz power link

Aerospace electromechanical actuators utilizing induction motors are under development in sizes up to 40 kW. While these actuators have immediate application to the Advanced Launch System (ALS) program, several potential applications are currently under study including the Advanced Aircraft Program. Several recent advances developed for the Space Station Freedom have allowed induction motors to be selected as a first choice for such applications. Among these technologies are bi-directional electronics and high frequency power distribution techniques. Each of these technologies are discussed with emphasis on their impact upon induction motor operation.

Hansen, Irving G.↗
NASA NTRS1990

Stanford/NASA-Ames Center of Excellence in model-based human performance

The human operator plays a critical role in many aeronautic and astronautic missions. The Stanford/NASA-Ames Center of Excellence in Model-Based Human Performance (COE) was initiated in 1985 to further our understanding of the performance capabilities and performance limits of the human component of aeronautic and astronautic projects. Support from the COE is devoted to those areas of experimental and theoretical work designed to summarize and explain human performance by developing computable performance models. The ultimate goal is to make these computable models available to other scientists for use in design and evaluation of aeronautic and astronautic instrumentation. Within vision science, two topics have received particular attention. First, researchers did extensive work analyzing the human ability to recognize object color relatively independent of the spectral power distribution of the ambient lighting (color constancy). The COE has supported a number of research papers in this area, as well as the development of a substantial data base of surface reflectance functions, ambient illumination functions, and an associated software package for rendering and analyzing image data with respect to these spectral functions. Second, the COE supported new empirical studies on the problem of selecting colors for visual display equipment to enhance human performance in discrimination and recognition tasks.

Wandell, Brian A.↗
NASA NTRS1990

Autonomous power expert fault diagnostic system for Space Station Freedom electrical power system testbed

The goal of the Autonomous Power System (APS) program is to develop and apply intelligent problem solving and control to the Space Station Freedom Electrical Power System (SSF/EPS) testbed being developed and demonstrated at NASA Lewis Research Center. The objectives of the program are to establish artificial intelligence technology paths, to craft knowledge-based tools with advanced human-operator interfaces for power systems, and to interface and integrate knowledge-based systems with conventional controllers. The Autonomous Power EXpert (APEX) portion of the APS program will integrate a knowledge-based fault diagnostic system and a power resource planner-scheduler. Then APEX will interface on-line with the SSF/EPS testbed and its Power Management Controller (PMC). The key tasks include establishing knowledge bases for system diagnostics, fault detection and isolation analysis, on-line information accessing through PMC, enhanced data management, and multiple-level, object-oriented operator displays. The first prototype of the diagnostic expert system for fault detection and isolation has been developed. The knowledge bases and the rule-based model that were developed for the Power Distribution Control Unit subsystem of the SSF/EPS testbed are described. A corresponding troubleshooting technique is also described.

Truong, Long V.↗
NASA NTRS1989

On the structure of pressure fluctuations in simulated turbulent channel flow

Pressure fluctuations in a turbulent channel flow are investigated by analyzing a database obtained from a direct numerical simulation. Detailed statistics associated with the pressure fluctuations are presented. Characteristics associated with the rapid (linear) and slow (nonlinear) pressure are discussed. It is found that the slow pressure fluctuations are larger than the rapid pressure fluctuations throughout the channel except very near the wall, where they are about the same magnitude. This is contrary to the common belief that the nonlinear source terms are negligible compared to the linear source terms. Probability density distributions, power spectra, and two-point correlations are examined to reveal the characteristics of the pressure fluctuations. The global dependence of the pressure fluctuations and pressure-strain correlations are also examined by evaluating the integral associated with Green's function representations of them. In the wall region where the pressure-strain terms are large, most contributions to the pressure-strain terms are from the wall region (i.e., local), whereas away from the wall where the pressure-strain terms are small, contributions are global. Structures of instantaneous pressure and pressure gradients at the wall and the corresponding vorticity field are examined.

Kim, John↗
NASA NTRS1990

Flight elements subpanel introduction and overview

Major objectives, milestones, key contacts, technology issues, accomplishments, and candidate programs are outlined. Topics addressed include: advanced avionics systems architectures; advanced information processing; avionics concepts; integrated Global Positioning System/guidance, navigation, and command concepts; advanced communication and telemetry; display and control concepts; advanced sensors and instrumentation; fault detection and fault management; advanced electric power, distribution, and control; EMA/power systems; and in-flight crew training. This presentation is represented by viewgraphs only.

Sollock, Paul E.↗
NASA NTRS1990

Two Axis Pointing System (TAPS) attitude acquisition, determination, and control

The Two Axis Pointing System (TAPS) is a 2 axis gimbal system designed to provide fine pointing of Space Transportation System (STS) borne instruments. It features center-of-mass instrument mounting and will accommodate instruments of up to 1134 kg (2500 pounds) which fit within a 1.0 by 1.0 by 4.2 meter (40 by 40 by 166 inch) envelope. The TAPS system is controlled by a microcomputer based Control Electronics Assembly (CEA), a Power Distribution Unit (PDU), and a Servo Control Unit (SCU). A DRIRU-II inertial reference unit is used to provide incremental angles for attitude propagation. A Ball Brothers STRAP star tracker is used for attitude acquisition and update. The theory of the TAPS attitude determination and error computation for the Broad Band X-ray Telescope (BBXRT) are described. The attitude acquisition is based upon a 2 star geometric solution. The acquisition theory and quaternion algebra are presented. The attitude control combines classical position, integral and derivative (PID) control with techniques to compensate for coulomb friction (bias torque) and the cable harness crossing the gimbals (spring torque). Also presented is a technique for an adaptive bias torque compensation which adjusts to an ever changing frictional torque environment. The control stability margins are detailed, with the predicted pointing performance, based upon simulation studies. The TAPS user interface, which provides high level operations commands to facilitate science observations, is outlined.

Azzolini, John D.↗
NASA NTRS1987

An overview of the artificial intelligence and expert systems component of RICIS

Artificial Intelligence and Expert Systems are the important component of RICIS (Research Institute and Information Systems) research program. For space applications, a number of problem areas that should be able to make good use of the above tools include: resource allocation and management, control and monitoring, environmental control and life support, power distribution, communications scheduling, orbit and attitude maintenance, redundancy management, intelligent man-machine interfaces and fault detection, isolation and recovery.

Feagin, Terry↗
NASA NTRS1990

Spacelab - Beyond development

Spacelab is a series of multiple configuration payload carriers that fit in the Orbiter cargo bay. The carriers, ranging from pressurized modules to simple support structures that span across the cargo bay, provide a variety of payload support services, such as cooling, power distribution, data management, pointing, and structural attachment. Previously published papers have addressed the joint development of the initial Spacelab system by the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA). Herein, the emphasis will be on the NASA utilization and evaluation of the system into the operational era of the Space Transportation System (STS), system enhancement, additional carrier configuration, the effects of time on system hardware, and subsequent replacements and improvement. All configurations added were intended to fulfill payload requirements not originally foreseen. Subsystem replacements thus far have resulted from life limits or unreliable performance while assessments and plans are underway to look also for increased performance and new payload requirements, to the transition from Spacelab to the Space Station Freedom.

Johnson, Charles W.↗
NASA NTRS1990

Induction motor control

Electromechanical actuators developed to date have commonly ultilized permanent magnet (PM) synchronous motors. More recently switched reluctance (SR) motors have been advocated due to their robust characteristics. Implications of work which utilized induction motors and advanced control techniques are discussed. When induction motors are operated from an energy source capable of controlling voltages and frequencies independently, drive characteristics are obtained which are superior to either PM or SR motors. By synthesizing the machine frequency from a high-frequency carrier (nominally 20 kHz), high efficiencies, low distortion, and rapid torque response are available. At this time multiple horsepower machine drives were demonstrated, and work is on-going to develop a 20 hp average, 40 hp peak class of aerospace actuators. This effort is based upon high-frequency power distribution and management techniques developed by NASA for Space Station Freedom.

Hansen, Irving G.↗
NASA NTRS1991

HF radar observations of Pc 5 field line resonances in the midnight/early morning MLT sector

The technique of F region sounding by HF coherent radar is applied to the study of field line resonances equatorward of a region of shear flow in the early morning sector. The motions were predominantly in the geomagnetic east-west direction, indicating north-south electric fields. These oscillations had pronounced peaks in their latitudinal power distribution. For the pulsation at 1.95 mHz, a latitudinal phase shift of 180 deg was observed across the peaks in all the look directions of the radar, and a longitudinal wavelength corresponding to an m value of 3 was obtained. For the 2.6-mHz pulsation, the phase shifts across the peaks had a variation with a look direction that indicated a significant longitudinal as well as latitudinal variation; for this activity, an m value of about 16 is estimated. These features are interpreted in terms of the field line resonance theory, and the possible sources of the pulsation energy are discussed.

Ruohoniemi, J. M.↗
NASA NTRS1992

Electro-Optical High-Voltage Sensors

Electro-optical sensors for measuring high voltages developed for use in automatically controlled power-distribution systems. Sensors connected to optoelectronic interrogating equipment by optical fibers. Because sensitive material and optical fibers are all dielectric, no problem in electrically isolating interrogating circuitry from high voltage, and no need for voltage dividers. Sensor signals transmitted along fibers immune to electromagnetic noise at radio and lower frequencies.

Gottsche, Allan↗