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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Static strain measurements on gas turbine combustor liners

It is noted that the combustor, a critical hot section component, can suffer failure through crack formation, buckling, and liner burn-through. Thus, there is a need to develop instrumentation which can function reliably in the combustor liner environment during testing and provide data to verify the accuracy of the analytical predictive tools used in designing the combustors. The results of an investigation into the suitability of a number of resistive, capacitive, optical, and electronic sensors are presented. The three sensors judged to possess the potential for measuring static strains up to + or - 2,000 micro-strain at temperatures to 1150 K with an accuracy of + or - 10% are the Kanthal A-1 Wire Strain Gage, Speckle Photography with Heterodyne Halo Evaluation, and the Thin Film Capacitive Sensor.

Raymondo, P.↗
NASA NTRS1993

A Microseismometer for Terrestrial and Extraterrestrial Applications

The scientific and technical requirements of extraterrestrial seismology place severe demands on instrumentation. Performance in terms of sensitivity, stability, and frequency band must match that of the best terrestrial instruments, at a fraction of the size, mass, and power. In addition, this performance must be realized without operator intervention in harsh temperature, shock, and radiation environments. These constraints have forced us to examine some fundamental limits of accelerometer design in order to produce a small, rugged, sensitive seismometer. Silicon micromachined sensor technology offers techniques for the fabrication of monolithic, robust, compact, low-power and -mass accelerometers. However, currently available sensors offer inadequate sensitivity and bandwidth. Our implementation of an advanced silicon micro machined seismometer is based on principles developed at JPL for high-sensitivity position sensor technology. The use of silicon micro machining technology with these new principles should enable the fabrication of a 10(exp -11) g sensitivity seismometer with a bandwidth of at least 0.01 to 20 Hz. The low Q properties of pure single-crystal silicon are essential in order to minimize the Brownian thermal noise limitations generally characteristic of seismometers with small proof masses. A seismometer consists of a spring-supported proof mass and a transducer for measuring its motion. For long period motion a position sensor is generally used, for which the displacement is proportional to the ground acceleration. The mechanical sensitivity can be increased either by increasing the proof mass or decreasing the spring stiffness, neither of which is desirable for planetary applications. Our approach has been to use an ultra sensitive capacitive position sensor with a sensitivity of better than 10(exp -13) m/Hz(exp 1/2). This allows the use of a stiffer suspension and a smaller proof mass. We have built several prototypes using these principles, and tests show that these devices can exhibit performance comparable to state-of-the-art instruments.

Banerdt, W.↗
NASA NTRS2006

"Virtual Feel" Capaciflectors

The term "virtual feel" denotes a type of capaciflector (an advanced capacitive proximity sensor) and a methodology for designing and using a sensor of this type to guide a robot in manipulating a tool (e.g., a wrench socket) into alignment with a mating fastener (e.g., a bolt head) or other electrically conductive object. A capaciflector includes at least one sensing electrode, excited with an alternating voltage, that puts out a signal indicative of the capacitance between that electrode and a proximal object.

Vranish, John M.↗
NASA NTRS2018

All-Elastomer 3-Axis Contact Resistive Tactile Sensor Arrays and Micromilled Manufacturing Methods Thereof

At least one tactile sensor includes an insulating layer and a conductive layer formed on the surface of the insulating layer. The conductive layer defines at least one group of flexible projections extending orthogonally from the surface of the insulating layer. The flexible projections include a major projection extending a distance orthogonally from the surface and at least one minor projection that is adjacent to and separate from the major projection wherein the major projection extends a distance orthogonally that is greater than the distance that the minor projection extends orthogonally. Upon a compressive force normal to, or a shear force parallel to, the surface, the major projection and the minor projection flex such that an electrical contact resistance is formed between the major projection and the minor projection. A capacitive tactile sensor is also disclosed that responds to the normal and shear forces.

Charalambides, Alexandros↗
NASA NTRS1976

Exospheric density measurements from the drag-free satellite Triad

The Triad satellite is maintained within 1 mm of its proof mass (a small metal ball) in a purely gravitational orbit, using a drag-free control system, named Discos, as the disturbance compensation system. The Discos proof mass is surrounded by an outer shell which holds fuel tanks and cold gas jets. The shell shields the proof mass from such nongravitational forces as radiation pressure, atmospheric drag, and micrometeorite impact. Whenever these forces displace the outer shell relative to the proof mass, an error signal is generated by a capacitive bridge sensor, and the satellite is propelled by gas jets to remain centered on the proof mass when the error reaches 1 mm. Local atmospheric densities near 800 km were measured, using ball position data, and the observed accelerations were corrected for the effects of solar radiation pressure. The measured densities reveal a greater dependence on latitude than that indicated by balloon satellites, and also a dependence on longitude. Only a small dependence on Kp, however, was observed in the region where the measurements were made.

Moe, K.↗
NASA NTRS1983

A microprocessor-based position control system for a telescope secondary mirror

The pointing requirements for the Shuttle IR Telescope Facility (SIRTF), which consists of an 0.85-m cryogenically cooled IR telescope, call for an image stability of 0.25 arcsec. Attention is presently given to a microprocessor-based position control system developed for the control of the SIRTF secondary mirror, employing a special control law (to minimize energy dissipation), a precision capacitive position sensor, and a specially designed power amplifier/actuator combination. The microprocessor generates the command angular position and rate waveforms in order to maintain a 90 percent dwell time/10 percent transition time ratio independently of chop frequency or amplitude. Performance and test results of a prototype system designed for use with a demonstration model of the SIRTF focal plane fine guidance sensor are presented.

Lorell, K. R.↗
NASA NTRS1991

A berthing and fastening strategy for orbital replacement units

Research in the area of berthing of Orbital Replacement Units (ORU's) at the GSFC consists of two major parts. First, we concentrate on the development of a comprehensive fastening strategy that can provide both mechanical as well as electrical connection to the ORU. Second, our efforts in robot collision avoidance and motion planning have led to the development of a state-of-the-art capacitive proximity sensor with associated motion control algorithms. These efforts combine to produce a system that allows safe and reliable machine assisted berthing. Although our main emphasis was on berthing of ORU's, we believe that some of our results can also be applied to docking.

Vranish, John↗
NASA NTRS1995

Aspects of atmospheric science and instrumentation for martian missions

There are four main reasons which make observations of meteorological phenomena in the Martian atmosphere important: (1) Meteorology as science, (2) Comparative meteorology between the Earth and Mars, (3) Other instruments need information about meteorological parameters, (4) Weather conditions essentially affect planning of safe future landings on Mars. The Earth and Mars have almost equal rotation periods and axial tilts, and hence similarities in the meteorology of these planets are considerable. At present, the number of theoretical modelling results of the Martian atmosphere is much larger than measured data, so measurements are urgently needed. Both in-situ observations on the planetary surface and remote sensing from an orbiter are necessary. The former give important ground-truth data to the latter. This paper outlines some open issues in Martian atmospheric research, and introduces promising capacitive micro sensors developed by the Vaisala Ltd, Finland, to be used in meteorological instrumentation for Mars. Due to the sensors' accuracy, light weight and low power consumption, they are very suitable for planetary exploration purposes.

Harri, A.-M.↗
NASA NTRS2007

System and Method for Detecting Cracks and their Location

A system and method are provided for detecting cracks and their location in a structure. A circuit coupled to a structure has capacitive strain sensors coupled sequentially and in parallel to one another. When excited by a variable magnetic field, the circuit has a resonant frequency that is different for unstrained and strained states. In terms of strained states, the resonant frequency is indicative of a region of the circuit that is experiencing strain induced by strain in a region of the structure in proximity to the region of the circuit. An inductor is electrically coupled to one end of each circuit. A magnetic field response recorder wirelessly transmits the variable magnetic field to the inductor and senses the resonant frequency of the circuit so-excited by the variable magnetic field.

Woodward, Stanley E.↗
NASA NTRS2008

Wearable Wireless Telemetry System for Implantable BioMEMS Sensors

Telemetry systems of a type that have been proposed for the monitoring of physiological functions in humans would include the following subsystems: Surgically implanted or ingested units that would comprise combinations of microelectromechanical systems (MEMS)- based sensors [bioMEMS sensors] and passive radio-frequency (RF) readout circuits that would include miniature loop antennas. Compact radio transceiver units integrated into external garments for wirelessly powering and interrogating the implanted or ingested units. The basic principles of operation of these systems are the same as those of the bioMEMS-sensor-unit/external-RFpowering- and-interrogating-unit systems described in "Printed Multi-Turn Loop Antennas for Biotelemetry" (LEW-17879-1) NASA Tech Briefs, Vol. 31, No. 6 (June 2007), page 48, and in the immediately preceding article, "Hand-Held Units for Short-Range Wireless Biotelemetry" (LEW-17483-1). The differences between what is reported here and what was reported in the cited prior articles lie in proposed design features and a proposed mode of operation. In a specific system of the type now proposed, the sensor unit would comprise mainly a capacitive MEMS pressure sensor located in the annular region of a loop antenna (more specifically, a square spiral inductor/ antenna), all fabricated as an integral unit on a high-resistivity silicon chip. The capacitor electrodes, the spiral inductor/antenna, and the conductor lines interconnecting them would all be made of gold. The dimensions of the sensor unit have been estimated to be about 110.4 mm. The external garment-mounted powering/ interrogating unit would include a multi-turn loop antenna and signal-processing circuits. During operation, this external unit would be positioned in proximity to the implanted or ingested unit to provide for near-field, inductive coupling between the loop antennas, which we have as the primary and secondary windings of an electrical transformer.

Simons, Rainee N.↗
NASA NTRS2009

NASA Tech Briefs, July 2009

Topics covered include: Dual Cryogenic Capacitive Density Sensor; Hail Monitor Sensor; Miniature Six-Axis Load Sensor for Robotic Fingertip; Improved Blackbody Temperature Sensors for a Vacuum Furnace; Wrap-Around Out-the-Window Sensor Fusion System; Wide-Range Temperature Sensors with High-Level Pulse Train Output; Terminal Descent Sensor Simulation; A Robust Mechanical Sensing System for Unmanned Sea Surface Vehicles; Additive for Low-Temperature Operation of Li-(CF)n Cells; Li/CFx Cells Optimized for Low-Temperature Operation; Number Codes Readable by Magnetic-Field-Response Recorders; Determining Locations by Use of Networks of Passive Beacons; Superconducting Hot-Electron Submillimeter-Wave Detector; Large-Aperture Membrane Active Phased-Array Antennas; Optical Injection Locking of a VCSEL in an OEO; Measuring Multiple Resistances Using Single-Point Excitation; Improved-Bandwidth Transimpedance Amplifier; Inter-Symbol Guard Time for Synchronizing Optical PPM; Novel Materials Containing Single-Wall Carbon Nanotubes Wrapped in Polymer Molecules; Light-Curing Adhesive Repair Tapes; Thin-Film Solid Oxide Fuel Cells; Zinc Alloys for the Fabrication of Semiconductor Devices; Small, Lightweight, Collapsible Glove Box; Radial Halbach Magnetic Bearings; Aerial Deployment and Inflation System for Mars Helium Balloons; Steel Primer Chamber Assemblies for Dual Initiated Pyrovalves; Voice Coil Percussive Mechanism Concept for Hammer Drill; Inherently Ducted Propfans and Bi-Props; Silicon Nanowire Growth at Chosen Positions and Orientations; Detecting Airborne Mercury by Use of Gold Nanowires; Detecting Airborne Mercury by Use of Palladium Chloride; Micro Electron MicroProbe and Sample Analyzer; Nanowire Electron Scattering Spectroscopy; Electron-Spin Filters Would Offer Spin Polarization Greater than 1; Subcritical-Water Extraction of Organics from Solid Matrices; A Model for Predicting Thermoelectric Properties of Bi2Te3; Integrated Miniature Arrays of Optical Biomolecule Detectors; A Software Rejuvenation Framework for Distributed Computing; Kurtosis Approach to Solution of a Nonlinear ICA Problem; Robust Software Architecture for Robots; R4SA for Controlling Robots; Bio-Inspired Neural Model for Learning Dynamic Models; Evolutionary Computing Methods for Spectral Retrieval; Monitoring Disasters by Use of Instrumented Robotic Aircraft; Complexity for Survival of Living Systems; Using Drained Spacecraft Propellant Tanks for Habitation; Connecting Node; and Electrolytes for Low-Temperature Operation of Li-CFx Cells.

Source record↗
NASA NTRS2003

MOS Circuitry Would Detect Low-Energy Charged Particles

Metal oxide semiconductor (MOS) circuits for measuring spatially varying intensities of beams of low-energy charged particles have been developed. These circuits are intended especially for use in measuring fluxes of ions with spatial resolution along the focal planes of mass spectrometers. Unlike prior mass spectrometer focal-plane detectors, these MOS circuits would not be based on ion-induced generation of electrons, and photons; instead, they would be based on direct detection of the electric charges of the ions. Hence, there would be no need for microchannel plates (for ion-to-electron conversion), phosphors (for electron-to-photon conversion), and photodetectors (for final detection) -- components that degrade spatial resolution and contribute to complexity and size. The developmental circuits are based on linear arrays of charge-coupled devices (CCDs) with associated readout circuitry (see figure). They resemble linear CCD photodetector arrays, except that instead of a photodetector, each pixel contains a capacitive charge sensor. The capacitor in each sensor comprises two electrodes (typically made of aluminum) separated by a layer of insulating material. The exposed electrode captures ions and accumulates their electric charges during signal-integration periods.

Sinha, Mahadeva↗
NASA NTRS2015

Differential Draining of Parallel-Fed Propellant Tanks in Morpheus and Apollo Flight

Parallel-fed propellant tanks are an advantageous configuration for many spacecraft. Parallel-fed tanks allow the center of gravity (cg) to be maintained over the engine(s), as opposed to serial-fed propellant tanks which result in a cg shift as propellants are drained from tank one tank first opposite another. Parallel-fed tanks also allow for tank isolation if that is needed. Parallel tanks and feed systems have been used in several past vehicles including the Apollo Lunar Module. The design of the feedsystem connecting the parallel tank is critical to maintain balance in the propellant tanks. The design must account for and minimize the effect of manufacturing variations that could cause delta-p or mass flowrate differences, which would lead to propellant imbalance. Other sources of differential draining will be discussed. Fortunately, physics provides some self-correcting behaviors that tend to equalize any initial imbalance. The question concerning whether or not active control of propellant in each tank is required or can be avoided or not is also important to answer. In order to provide data on parallel-fed tanks and differential draining in flight for cryogenic propellants (as well as any other fluid), a vertical test bed (flying lander) for terrestrial use was employed. The Morpheus vertical test bed is a parallel-fed propellant tank system that uses passive design to keep the propellant tanks balanced. The system is operated in blow down. The Morpheus vehicle was instrumented with a capacitance level sensor in each propellant tank in order to measure the draining of propellants in over 34 tethered and 12 free flights. Morpheus did experience an approximately 20 lb/m imbalance in one pair of tanks. The cause of this imbalance will be discussed. This paper discusses the analysis, design, flight simulation vehicle dynamic modeling, and flight test of the Morpheus parallel-fed propellant. The Apollo LEM data is also examined in this summary report of the flight data.

Hurlbert, Eric↗
NASA NTRSDate not supplied

Displacement Damage Induced Dark Current and Random Telegraph Signal in P-Type Deep-Trench Pinned Photogates

This study focuses on displacement damage induced dark current and Random Telegraph Signal (RTS) in STMicroelectronics P-Type photogate, a device moving away from the 4T Pinned-Photodiode, with a sensitive volume exclusively made of boron-doped P-type epitaxy, and collecting holes instead of electrons. Results show a typical trend for the shape of dark current and RTS degradation in CMOS Image Sensors with the exception that the measured generation rates seem 2 times smaller than typical literature values in irradiated silicon. Different hypothesis on the origin of this discrepancy are explored.

displacement damage dose↗
NASA NTRS1993

On Machine Capacitance Dimensional and Surface Profile Measurement System

A program was awarded under the Air Force Machine Tool Sensor Improvements Program Research and Development Announcement to develop and demonstrate the use of a Capacitance Sensor System including Capacitive Non-Contact Analog Probe and a Capacitive Array Dimensional Measurement System to check the dimensions of complex shapes and contours on a machine tool or in an automated inspection cell. The manufacturing of complex shapes and contours and the subsequent verification of those manufactured shapes is fundamental and widespread throughout industry. The critical profile of a gear tooth; the overall shape of a graphite EDM electrode; the contour of a turbine blade in a jet engine; and countless other components in varied applications possess complex shapes that require detailed and complex inspection procedures. Current inspection methods for complex shapes and contours are expensive, time-consuming, and labor intensive.

Resnick, Ralph↗
NASA NTRS2011

Capacitance Based Moisture Sensing for Microgravity Plant Modules: Sensor Design and Considerations

Life support systems for growing plants in microgravity should strive for providing optimal growing conditions and increased automation. Accurately tracking soil moisture content can forward both of these aims, so an attempt was made to instrument a microgravity growth module currently in development, the VEGGIE rooting pillow, in order to monitor moisture levels. Two electrode systems for a capacitance-based moisture sensor were tested. Trials with both types of electrodes showed a linear correlation between observed capacitance and water content over certain ranges of moisture within the pillows. Overall, both types of the electrodes and the capacitance-based moisture sensor are promising candidates for tracking water levels for microgravity plant growth systems.

Schaber, Chad L.↗
NASA NTRS1998

Radial displacement sensor for non-contact bearings

A radial position sensor includes four capacitive electrodes oriented about a shaft, arranged in two diametrically opposite pairs. Sensor circuitry generates an output signal in proportion to the capacitance between the electrodes and the shaft; the capacitance between an electrode and the shaft increases as the shaft approaches the electrode and decreases as the shaft recedes from the electrode. The sensor circuitry applies an alternating voltage to one electrode of a pair and a 180 degree out of phase alternating voltage to the other electrode of the pair. The electrical responses of the two electrodes to their respective input signals are summed to form a radial deviation signal which is relatively free from the alternating voltage and accurately represents the position of the shaft relative to the electrodes of the pair.

McCormick, John A.↗
NASA NTRS1988

Integrated control and health management. Orbit transfer rocket engine technology program

To insure controllability of the baseline design for a 7500 pound thrust, 10:1 throttleable, dual expanded cycle, Hydrogen-Oxygen, orbit transfer rocket engine, an Integrated Controls and Health Monitoring concept was developed. This included: (1) Dynamic engine simulations using a TUTSIM derived computer code; (2) analysis of various control methods; (3) Failure Modes Analysis to identify critical sensors; (4) Survey of applicable sensors technology; and, (5) Study of Health Monitoring philosophies. The engine design was found to be controllable over the full throttling range by using 13 valves, including an oxygen turbine bypass valve to control mixture ratio, and a hydrogen turbine bypass valve, used in conjunction with the oxygen bypass to control thrust. Classic feedback control methods are proposed along with specific requirements for valves, sensors, and the controller. Expanding on the control system, a Health Monitoring system is proposed including suggested computing methods and the following recommended sensors: (1) Fiber optic and silicon bearing deflectometers; (2) Capacitive shaft displacement sensors; and (3) Hot spot thermocouple arrays. Further work is needed to refine and verify the dynamic simulations and control algorithms, to advance sensor capabilities, and to develop the Health Monitoring computational methods.

Holzmann, Wilfried A.↗