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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 919 records · Page 51

All sources NASA NTRS DOE OSTI

NASA NTRS1973

The application of standardized control and interface circuits to three dc to dc power converters.

Standardized control and interface circuits were applied to the three most commonly used dc to dc converters: the buck-boost converter, the series-switching buck regulator, and the pulse-modulated parallel inverter. The two-loop ASDTIC regulation control concept was implemented by using a common analog control signal processor and a novel digital control signal processor. This resulted in control circuit standardization and superior static and dynamic performance of the three dc-to-dc converters. Power components stress control, through active peak current limiting and recovery of switching losses, was applied to enhance reliability and converter efficiency.

Yu, Y.↗

NASA NTRS1974

A self-reorganizing digital flight control system for aircraft

This paper presents a design method for digital self-reorganizing control systems which is optimally tolerant of failures in aircraft sensors. The functions of this system are accomplished with software instead of the popular and costly technique of hardware duplication. The theoretical development, based on M-ary hypothesis testing, results in a bank of M Kalman filters operating in parallel in the failure detection logic. A moving window of the innovations of each Kalman filter drives the detection logic to decide the failure state of the system. The detection logic also selects the optimal state estimate (for control logic) from the bank of Kalman filters. The design process is applied to the design of a self-reorganizing control system for a current configuration of the space shuttle orbiter at Mach 5 and 120,000 feet. The failure detection capabilities of the system are demonstrated using a real-time simulation of the system with noisy sensors.

Montgomery, R. C.↗

NASA NTRS1975

Metabolic rate control during extravehicular activity simulations and measurement techniques during actual EVAS

A description of the methods used to control and measure metabolic rate during ground simulations is given. Work levels attained at the Space Environment Simulation Laboratory are presented. The techniques and data acquired during ground simulations are described and compared with inflight procedures. Data from both the Skylab and Apollo Program were utilized and emphasis is given to the methodology, both in simulation and during flight. The basic techniques of work rate assessment are described. They include oxygen consumption, which was useful for averages over long time periods, heart rate correlations based on laboratory calibrations, and liquid cooling garment temperature changes. The relative accuracy of these methods as well as the methods of real-time monitoring at the Mission Control Center are discussed. The advantages and disadvantages of each of the metabolic measurement techniques are discussed. Particular emphasis is given to the problem of utilizing oxygen decrement for short time periods and heart rate at low work levels. A summary is given of the effectiveness of work rate control and measurements; and current plans for future EVA monitoring are discussed.

David J. Horrigan↗

NASA NTRS1978

Arc termination cracks in Inconel 718 and Incoloy 903

The welding of the nickel base, heat resistant alloys that are used extensively for welded Shuttle engine components revealed solidification cracking characteristics at weld termination points. If not detected and removed, these crater cracks may cause costly component failure. To better understand this characteristic, welding termination techniques were studied and methods developed to eliminate crater cracks. It was determined that weld termination solidification cracking can be eliminated by controlled decrease of welding current, welding voltage, wire feed, and travel speed.

Bayless, E.↗

NASA NTRS1979

Results of the second flight test of the Loran-C receiver/data collection system

The components of the Loran-C navigation system which were developed thus far are a phase-locked-loop receiver and a microcomputer development system. The microcomputer is being used as a means of testing and implementing software to handle sensor control and navigation calculations. Currently, the microcomputer is being used to collect and record data from the receiver in addition to development work. With these components, it was possible to record receiver data over a period of time and then reduce this data to obtain statistical information. It was particularly interesting to load the equipment developed in the laboratory into an aircraft and collect data while in flight. For initial flight tests, some important considerations were how well the entire system will perform in the field, signal strength levels while on the ground and in the air, the amount of noise present, changing of signal-to-noise ratio for various aircraft configurations and maneuvers, receiver overloading due to other equipment and antennas, and the overall usefulness of Loran-C as a navigation aid.

Fischer, J. P.↗

NASA NTRS1978

Characterization of degraded nickel cadmium cells

Various cells were cycled until degradation and then tested to determine the electrochemical characterization of the cells with regard to charge control. A constant voltage charged to a temperature-biased voltage, using up to an 8-voltage limit was used for the evaluation. Graphs show severe discharge voltage degradation with cycling and periodic capacity discharge; voltage extremes for cells with and without periodic capacity discharges; voltage extremes for cells with high rate discharge; voltage-temperature levels used for charge control; end of charge current and discharge voltage for 5 percent DOD cycling; cell capacity following 5 percent DOD cycling; and the end of discharge voltage and typical charge current profiles for the 20 percent DOD cycling.

Gross, S.↗

NASA NTRS1980

Radiation damage in high voltage silicon solar cells

High open circuit voltage cell designs based on 0.1 Ohm cm p-type silicon were irradiated with 1 MeV electrons and their performance determined to fluences as high as 10 to the 15th power per sq cm. Of the three cell designs, radiation induced degradation was greatest in the high low emitter (HLE) cell. The diffused and ion implanted cells degraded approximately equally but less than the HLE cell. Degradation was greatest in an HLE cell exposed to X-rays before electron irradiation. The cell regions controlling both short circuit current and open circuit voltage degradation were defined in all three cell types. An increase in front surface recombination velocity accompanied time dependent degradation of an HLE cell after X-irradiation. It was speculated that this was indirectly due to a decrease in positive charge at the silicon oxide interface. Modifications aimed at reducing radiation induced degradation are proposed for all three cell types.

Weinberg, I.↗

NASA NTRS1980

Production readiness verification testing

A Production Readiness Verification Testing (PRVT) program has been established to determine if structures fabricated from advanced composites can be committed on a production basis to commercial airline service. The program utilizes subcomponents which reflect the variabilities in structure that can realistically be expected from current production and quality control technology to estimate the production qualities, variation in static strength, and durability of advanced composite structures. The results of the static tests and a durability assessment after one year of continuous load/environment testing of twenty two duplicates of each of two structural components (a segment of the front spar and cover of a vertical stabilizer box structure) are discussed.

James, A. M.↗

NASA NTRS1981

Systems design and analysis of the microwave radiometer spacecraft

Systems design and analysis data were generated for microwave radiometer spacecraft concept using the Large Advanced Space Systems (LASS) computer aided design and analysis program. Parametric analyses were conducted for perturbations off the nominal-orbital-altitude/antenna-reflector-size and for control/propulsion system options. Optimized spacecraft mass, structural element design, and on-orbit loading data are presented. Propulsion and rigid-body control systems sensitivities to current and advanced technology are established. Spacecraft-induced and environmental effects on antenna performance (surface accuracy, defocus, and boresight off-set) are quantified and structured material frequencies and modal shapes are defined.

Garrett, L. B.↗

NASA NTRS1982

Algorithms for software development version control and change detection

Simple computer algorithms for processing source program and text data files in order to extract change detection, version control, version history, and current status information are described. These algorithms presuppose that it is possible to attach to each record of the source files a 6-character code, placed within delimiters that will cause the compiler, or other using program, to ignore this code field. The code contains a 2-character code for a character-by-character position-sensitive checksum of the record, another for the record number in the file, and a third for the data on which the encoding took place. Once the source file has been thus encoded, it is possible to detect the following transactions on the file since the most recent version coding; (1) addition of new records (having no version code), (2) modification of existing records, (3) deletion of a number of records, (4) movement and/or duplication of existing records, and (5) modification and duplication of records. In addition, it is possible to extract a version history of the number of records created or modified by date. A special file listing program is described which prints the file records without showing the version codes, but places a "change bar" at the right margin whenever a change is detected. The program also provides a list of changed pages and a version history.

Tausworthe, R. C.↗

NASA NTRS1982

Remote orbital servicing system concept

Increased applications of automation technology identified as necessary for NASA to carry out its missions within the constraints of future funding and available physical resources are described. A concept for a Remote Orbital Servicing System (ROSS) based on present teleoperator and robotics technology is presented. A single servicer design compatible with three specified spacecraft, capable of performing service to the same extent as manned extravehicular activity, controlled from a ground control station, and using currently available technology is conceptualized.

Meintel, A. J.↗

NASA NTRS1987

Diode Structure for Microwave and Infrared Applications

Microwave signals switched or modulated optically. Planar diode with transparent cathode made in BaAs, Si, and InSb versions. Depending on specific configuration and material, such diode used for optical modulation of microwave signal or as infrared detector. Transparent cathode fabricated on GaAs diode so diode illuminates to generate and control short-circuit current.

Alcorn, George↗

NASA NTRS1986

Mission Adaptive Wing test program

With the completion of the F-111 test-bed Mission Adaptive Wing (MAW) test program's manual flight control system, emphasis has been shifted to flight testing of MAW automatic control modes. These encompass (1) cruise camber control, (2) maneuver camber control, (3) maneuver load control, and (4) maneuver enhancement and load alleviation control. The aircraft is currently cleared to a 2.5-g maneuvering limit due to generally higher variable-incidence wing pivot loads than had been anticipated, especially at the higher wing-camber settings. Buffet is noted to be somewhat higher than expected at the higher camber settings.

Birk, Frank T.↗

NASA NTRS1988

Arc-Jet Power Supply And Starting Circuit

Power efficiency high, current regulated, and starting automatic. New circuit for starting arc jets and controlling them in steady operation capable of high power efficiency and constructed in lightweight form. Feedback control system keeps arc-jet current nearly constant, once arc struck by starting pulse. Circuit made of commercially available components. Design capable of high power efficiency.

Gruber, Robert P.↗

NASA NTRS1986

Laminar flow integration: Flight tests status and plans

Under the Aircraft Energy Efficiency - Laminar Flow Control Program, there are currently three flight test programs under way to address critical issues concerning laminar flow technology application to commercial transports. The Leading-Edge Flight Test (LEFT) with a JetStar aircraft is a cooperative effort with the Ames/Dryden Flight Research Facility to provide operational experience with candidate leading-edge systems representative of those that might be used on a future transport. In the Variable Sweep Transition Flight Experiment (VSTFE), also a cooperative effort between Langley and Ames/Dryden, basic transition data on an F-14 wing with variable sweep will be obtained to provide a data base for laminar flow wing design. Finally, under contract to the Boeing Company, the acoustic environment on the wing of a 757 aircraft will be measured and the influence of engine noise on laminar flow determined with a natural laminar flow glove on the wing. The status and plans for these programs are reported.

Wagner, R. D.↗

NASA NTRS1988

Field oriented control of an induction machine in a high frequency link power system

A field-oriented controlled induction machine drive operating with a high-frequency single-phase sinusoidal voltage link is presented. System performance is investigated by computer simulation and is verified by a test on a prototype system. A novel control loop to minimize the link voltage fluctuation is proposed. The capability of rapid demagnetization of the induction machine by current regulation is investigated. A current-modulation technique termed mode control is proposed, and its performance is compared with that of the conventional delta-modulation technique.

Sul, Seung K.↗

NASA NTRS1988

Inorganic chemical precipitate formation payload design

The Get Away Special payload to investigate the formation of inorganic precipitates (G-405) utilizes six transparent chemical reaction chambers to actively mix a dry powder with a liquid solution. At predetermined intervals the progress of the precipitate formation is photographed and stored as data. The precipitate particles will also be subject to post-flight analysis. The various tasks performed during the 14 hour duration of the experiment are initiated and monitored by a custom-built digital controller. The payload is currently scheduled as a backup payload for STS-29 with a possible launch date of January, 1989.

Friedrich, Craig↗

NASA NTRS1988

Class 100 large spacecraft facility

A new, large spacecraft dedicated clean facility was built and is operating at TRW Space and Defense, Redondo Beach, California. The facility includes typical integration and test and laboratory capabilities. Over 4500 square feet of filtered, air conditioned, hydrocarbon monitored, and personnel controlled working area is currently being used in state-of-the-art aerospace applications.

Ryan, L. E.↗