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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Vapor generator wand

In low speed wind tunnels it is often desirable to visualize airflow to augment observations made with instruments such as strain and pressure gages. Current technology devices for delivery of a vapor are bulky and thus disrupt local airflow. It is the object of this invention to provide a device capable of delivering a stream of vapor with a minimal effect on local airflow. The present invention achieves this object by utilizing a narrow tube as a heating device for producing the vapor. Running an electrical current through the tube provides resistive heating to a liquid which produces a vapor when boiled. As the entire heating and delivery portion of the device is simply a small cylinder the disruption to airflow within the tunnel is minimized. this allows an experimenter to place the source of vapor fairly close to a model without causing too much change to the model data. The novelty of the present invention lies in reducing the bulk of current technology devices by combining the acts of heating and delivery.

Robelen, David B.↗
NASA NTRS1994

Hidden Markov models and neural networks for fault detection in dynamic systems

Neural networks plus hidden Markov models (HMM) can provide excellent detection and false alarm rate performance in fault detection applications, as shown in this viewgraph presentation. Modified models allow for novelty detection. Key contributions of neural network models are: (1) excellent nonparametric discrimination capability; (2) a good estimator of posterior state probabilities, even in high dimensions, and thus can be embedded within overall probabilistic model (HMM); and (3) simple to implement compared to other nonparametric models. Neural network/HMM monitoring model is currently being integrated with the new Deep Space Network (DSN) antenna controller software and will be on-line monitoring a new DSN 34-m antenna (DSS-24) by July, 1994.

Smyth, Padhraic↗
NASA NTRS1995

Utility aspects of space power: Load management versus source management

Electrical power, as an area of study, is relatively young as compared to language, chemistry, physics, mathematics, philosophy, metallurgy, textiles, transportation, or farming. Practically all of the technology that has enabled the huge, continent-spanning power grids that have become ubiquitous in developed countries was developed in the last 150 years. In fact, Tesla's advocacy of alternating current for transmission just won out in the beginning of this century. Despite the novelty of the field as a whole, space power applications are, of course, much newer. This paper looks at the history of space power, and compares it to its older sibling on earth, forming a basis for determining appropriate transitions of technology from the terrestrial realm to space applications.

Walls, B.↗
NASA NTRS1995

Method and Apparatus for Measuring Fluid Flow

The invention is a method and apparatus for monitoring the presence, concentration, and the movement of fluids. It is based on utilizing electromagnetic measurements of the complex permittivity of the fluids for detecting and monitoring the fluid. More particularly the apparatus uses one or more microwave probes which are placed at the locations where the measurements are to be made. A radio frequency signal is transmitted to the probe and the reflected signal is phase and amplitude detected at a rapid rate for the purpose of identifying the fluids, based on their dielectric constant at the probe. The apparatus can be used for multiple purposes including measures of flow rates, turbulence, dispersion, fluid identification, and changes in flow conditions of multiple fluids or multiple states of a single fluid in a flowline or a holding container. The apparatus includes a probe consisting of two electrical conductors separated by an insulator. A radio frequency signal is communicated to the probe and is reflected back from the portion of the probe exposed to the fluid. The radio frequency signal also provides a reference signal. An oscillator generates a second signal which combined with each of the reference signal and the reflected signal to produce signals of lower frequencies to facilitate filtering and amplifying those signals. The two signals are then mixed in a detector to produce an output signal that is representative of the phase and amplitude change caused by the reflection of the signal at the probe exposed to the fluid. The detector may be a dual phase detector that provides two such output signals that are in phase quadrature. A phase shifter may be provided for selectively changing the phase of the reference signal to improve the sensitivity of at least one of the output signals for more accurate readings and/or for calibration purposes. The two outputs that are in quadrature with respect to each other may be simultaneously monitored to account for drift errors. The output signals are digitized and provided to a computer at a sample rate which may be very high. The computer is operable to identify the fluid based on its complex permittivity as may be useful for identifying the flow rates, determining the fluid mixture ratio, detecting impurities in the fluid, and so forth. Novelty is believed to reside in the use of the real part of complex permittivity to measure small difference in permittivity of the fluid.

Arndt, G. Dickey↗
NASA NTRS1996

Increased Efficiency LED

In a semiconductor light emitting diode (LED) a large proportion of the light produced will be internally reflected when it strikes the end face of the LED at a semiconductor-air interface. This is due to the high index of refraction of most LED semiconductor materials. This problem may be partially overcome by modification of the shape of the LED by a reverse taper of the sides of the LED. Light is redirected by the taper to strike the interface at an angle closer to normal. This allows light to exit the LED that would be totally internally reflected in an untapered LED. The novelty of the present invention lies in the tapering of the sides of the LED for increased through transmission of light. Prior art devices have made use surface modifications such as roughening, addition of guiding layers, use of index matching materials and hemispherical shaping of the emitting end of the LED. Current technology LEDs have a transmission efficiency of only a few percent. An increase in this efficiency would be of great value to any technology that makes use of LEDs for light generation. The present invention is related to LAR 1 5050-SB, Collection of Light from Optical Fibers of NA greater than 1.

Egalon, Claudio Oliviera↗
NASA NTRS1996

Dual Brushless Resolver Rate Sensor

This invention relates to dual analog angular rate sensors which are implemented without the use of mechanical brushes. A resolver rate sensor which includes two brushless resolvers which are mechanically coupled to the same output shaft is provided with inputs which are provided to each resolver by providing the first resolver with a DC input and the second resolver with an AC sinusoidal input. A trigonometric identity in which the sum of the squares of the sin and cosine components equal one is used to advantage in providing a sensor of increased accuracy. The first resolver may have a fixed or variable DC input to permit dynamic adjustment of resolver sensitivity thus permitting a wide range of coverage. Novelty and advantages of the invention reside in the excitation of a resolver with a DC signal and in the utilization of two resolvers and the trigonometric identity of cos(exp 2)(theta) + sin(exp 2)(theta) = 1 to provide an accurate rate sensor which is sensitive to direction and accurate through zero rate.

Howard, David E.↗
NASA NTRS1996

Collection of Light From an Optical Fiber With a Numerical Aperture Greater Than One

In an optical fiber having NA greater than 1, light may be internally reflected when it strikes the fiber end at a fiber-air interface. This problem may be overcome by modification of the fiber by reverse tapering the core. Light is redirected by the taper to strike the interface at an angle closer to normal. This allows light to exit the fiber end that would by internally reflected in an untapered fiber of NA greater than 1. The novelty of the present invention lies in the tapering of the fiber core for increased through transmission of light. Prior art devices have made use of fiber tapers to achieve mode control or fiber coupling. The problem of internal reflection has not been addressed as it is one that is not as important in fibers having NA less than 1, which are more common. In chemical sensing it is advantageous to make use of fibers having higher NA due to an increased sensitivity. However the advantages in sensitivity are diminished due to the loss of signal at the fiber-air interface. The present invention overcomes the problem of loss at the interface, thus facilitating the use of high NA fibers for chemical sensing.

Egalon, Claudio O.↗
NASA NTRS1996

Crash-Energy Absorbing Composite Structure and Method of Fabrication

A stand-alone, crash-energy absorbing structure and fabrication method are provided. A plurality of adjoining rigid cells are each constructed of resin-cured fiber reinforcement and are arranged in a geometric configuration. The fiber reinforcement can be in the form of a fabric or braided fibers wrapped about a core that is either left in place or removed from the ultimate cured structure. The geometric configuration of cells is held together with more fiber reinforcement (in the form of fabric or braided fibers) in order to integrate the cells in the geometric configuration. The additional fiber reinforcement is resin-cured to the cells. Curing of the cells and ultimate structure can occur in a single step. In applications where post-crash integrity is necessary, ductile fibers can be used to integrate the cells in the geometric configuration. The novelty of the present invention is that simple fabrication techniques are used to create structures that can be formed in a variety of net stable shapes without additional reinforcement and can withstand combined loading while crushing in a desired direction.

Kellas, Sotiris↗
NASA NTRS1996

Strain Insensitive Optical Phase Locked Loop

An apparatus is provided to allow for quasi distributed sensing of strain within a test object. Strain insensitive fiber is used to deliver a light signal to a strain sensitive fiber in an optical phase locked loop sensor configuration. The use of strain insensitive delivery fiber allows for non-integrated measurements of strain without the use of expensive electronics such as those employed in ODTR techniques. The novelty of the present invention lies in the use of strain insensitive multimode fiber. The inventors had previously developed a similar sensor with strain insensitive fiber, however it was restricted to the use of single or few mode fibers. The use of an optical phase locked loop arrangement allows for the use of multimode strain insensitive fiber.

Egalon, Claudio Oliviera↗
NASA NTRS1996

Digital Mammography with a Mosaic of CCD-Arrays

The present invention relates generally to a mammography device and method and more particularly to a novel digital mammography device and method to detect microcalcifications of precancerous tissue. A digital mammography device uses a mosaic of electronic digital imaging arrays to scan an x-ray image. The mosaic of arrays is repositioned several times to expose different portions of the image, until the entire image is scanned. The data generated by the arrays during each exposure is stored in a computer. After the final exposure, the computer combines data of the several partial images to produce a composite of the original x-ray image. An aperture plate is used to reduce scatter and the overall exposure of the patient to x-rays. The novelty of this invention is that it provides a digital mammography device with large field coverage, high spatial resolution, scatter rejection, excellent contrast characteristics and lesion detectability under clinical conditions. This device also shields the patient from excessive radiation, can detect extremely small calcifications and allows manipulation and storage of the image.

Jalink, Antony, Jr.↗
NASA NTRS1995

Thermally Stable, Piezoelectric and Pyroelectric Polymeric Substrates and Method Relating Thereto

Production of an electric voltage in response to mechanical excitation (piezoelectricity) or thermal excitation (pyroelectricity) requires a material to have a preferred dipole orientation in its structure. This preferred orientation or polarization occurs naturally in some crystals such as quartz and can be induced into some ceramic and polymeric materials by application of strong electric or mechanical fields. For some materials, a combination of mechanical and electrical orientation is necessary to completely polarize the material. The only commercially available piezoelectric polymer is poly(vinylidene fluoride) (PVF2). However, this polymer has material and process limitations which prohibit its use in numerous device applications where thermal stability is a requirement. By the present invention, thermally stable, piezoelectric and pyroelectric polymeric substrates were prepared from polymers having a softening temperature greater than 1000C. A metal electrode material is deposited onto the polymer substrate and several electrical leads are attached to it. The polymer substrate is heated in a low dielectric medium to enhance molecular mobility of the polymer chains. A voltage is then applied to the polymer substrate inducing polarization. The voltage is then maintained while the polymer substrate is cooled 'freezing in' the molecular orientation. The novelty of the invention resides in the process of preparing the piezoelectric and pyroelectric polymeric substrate. The nonobviousness of the invention is found in heating the polymeric substrate in a low dielectric medium while applying a voltage.

Simpson, Joycelyn O.↗
NASA NTRS1996

Thickness Measurement Device for Ice/Water Mixture

A device and method are provided for determining the thickness of an ice and water mixture accumulated on the outer surface of an object. First and second total impedance sensors are operated at first and second frequencies over which the dielectric constants for water and ice are substantially the same. Corresponding first and second AC total impedance measuring circuits are coupled to the first and second sensors to produce output voltages based on the total impedance changes sensed by the sensors. A processor is coupled to the first and second measuring circuits to generate a voltage ratio using the measured output voltages. The voltage ratio is indicative of the thickness of the ice and water mixture. The novelty of the present invention is the use of two frequencies and dual geometry impedance sensors in order to be sensitive to the formation of ice. Thus, critical situations created by the presence of solid ice can be averted. The device is simple and is easily incorporated into current technology thereby making its realization cost- effective.

Weinstein, Leonard M.↗
NASA NTRS1995

Weaves as an Interconnection Fabric for ASIM's and Nanosatellites

Many of the micromachines under consideration require computer support, indeed, one of the appeals of this technology is the ability to intermix mechanical, optical, analog, and digital devices on the same substrate. The amount of computer power is rarely an issue, the sticking point is the complexity of the software required to make effective use of these devices. Micromachines are the nano-technologist's equivalent of 'golden screws'. In other words, they will be piece parts in larger assemblages. For example, a nano-satellite may be composed of stacked silicon wafers where each wafer contains hundreds to thousands of micromachines, digital controllers, general purpose computers, memories, and high-speed bus interconnects. Comparatively few of these devices will be custom designed, most will be stock parts selected from libraries and catalogs. The novelty will lie in the interconnections. For example, a digital accelerometer may be a component part in an adaptive suspension, a monitoring element embedded in the wrapper of a package, or a portion of the smart skin of a launch vehicle. In each case, this device must inter-operate with other devices and probes for the purposes of command, control, and communication. We propose a software technology called 'weaves' that will permit large collections of micromachines and their attendant computers to freely intercommunicate while preserving modularity, transparency, and flexibility. Weaves are composed of networks of communicating software components. The network, and the components comprising it, may be changed even while the software, and the devices it controls, are executing. This unusual degree of software plasticity permits micromachines to dynamically adapt the software to changing conditions and allows system engineers to rapidly and inexpensively develop special purpose software by assembling stock software components in custom configurations.

Gorlick, Michael M.↗
NASA NTRS1995

Advanced packaging for Integrated Micro-Instruments

The relationship between packaging, microelectronics, and micro-electrical-mechanical systems (MEMS) is an important one, particularly when the edges of performance boundaries are pressed, as in the case of miniaturized systems. Packaging is a sort of physical backbone that enables the maximum performance of these systems to be realized, and the penalties imposed by conventional packing approaches is particularly limiting for MEMS devices. As such, advanced packaging approaches, such as multi-chip modules (MCM's) have been touted as a true means of electronic 'enablement' for a variety of application domains. Realizing an optimum system of packaging, however, in not as simple as replacing a set of single chip packages with a substrate of interconnections. Research at Phillips Laboratory has turned up a number of integrating options in the two- and three-dimensional rending of miniature systems with physical interconnection structures with intrinsically high performance. Not only do these structures motivate the redesign of integrated circuits (IC's) for lower power, but they possess interesting features that provide a framework for the direct integration of MEMS devices. Cost remains a barrier to the application of MEMS devices, even in space systems. Several innovations are suggested that will result in lower cost and more rapid cycle time. First, the novelty of a 'constant floor plan' MCM which encapsulates a variety of commonly used components into a stockable, easily customized assembly is discussed. Next, the use of low-cost substrates is examined. The anticipated advent of ultra-high density interconnect (UHDI) is suggested as the limit argument of advanced packaging. Finally, the concept of a heterogeneous 3-D MCM system is outlined that allows for the combination of different compatible packaging approaches into a uniformly dense structure that could also include MEMS-based sensors.

Lyke, James L.↗
NASA NTRS1996

The Global Perspective on the Evolution of Solids in a Protoplanetary Disk

It is currently thought that planets around solar-type stars form by the accumulation of solid matter entrained in a gaseous, turbulent protoplanetary disk. We have developed a model designed to simulate the part of this process that starts from small particles suspended in the gaseous disk at the end of the formation stage, and ends up with most of the solid material aggregated into 1-10-km planetesimals. The major novelty of our approach is its emphasis on the global, comprehensive treatment of the problem, as our model simultaneously keeps track of the evolution of gas and solid particles due to gas-solid coupling, coagulation, sedimentation, and evaporation/condensation. The result of our calculations is the radial distribution of solid material circumnavigating a star in the form of a planetesimal swarm. Such a distribution should well approximate the radial apportionment of condensed components of the planets spread over the radial extent of the mature planetary system. Therefore we view our calculations as an attempt to predict the large-scale architecture of planetary systems and to assess their potential diversity. In particular, we have found that some initial conditions lead to all solids being lost to the star, but we can also identify initial conditions leading to a radial distribution of solid material quite reminiscent of what is found in our solar system.

Stepinski, T. F.↗
NASA NTRS1993

The Jet Propulsion Laboratory Space Exploration: Past, Present and Future

The most recent scientific results from space exploration carried out by the Jet Propulsion Laboratory (JPL) are discussed. To aid understanding of these results, a brief background of JPL's history is presented, followed by a description of the Deep Space Network, JPL's system of antennas which communicates with spacecraft. The results from the missions of Voyager 1 and Voyager 2 are described. The atmosphere, rings, satellites and magnetospheres of Jupiter, Saturn, Uranus and Neptune are discussed with particular emphasis on novelty of the discoveries and the challenges encountered in explaining them. A brief discussion of the impact of spray research upon space exploration follows. This is because most recently launched missions used liquid fueled rockets to escape Earth's gravity. A summary of future missions and the National Aeronautics and Space Administration's new policies is presented in the conclusion.

Bellan, Josette↗
NASA NTRS1997

Instability Mechanisms of Thermally-Driven Interfacial Flows in Liquid-Encapsulated Crystal Growth

During the past year, a great deal of effort was focused on the enhancement and refinement of the computational tools developed as part of our previous NASA grant. In particular, the interface mollification algorithm developed earlier was extended to incorporate the effects of surface-rheological properties in order to allow the study of thermocapillary flows in the presence of surface contamination. These tools will be used in the computational component of the proposed research in the remaining years of this grant. A detailed description of the progress made in this area is provided elsewhere. Briefly, the method developed allows for the convection and diffusion of bulk-insoluble surfactants on a moving and deforming interface. The novelty of the method is its grid independence: there is no need for front tracking, surface reconstruction, body-fitted grid generation, or metric evaluations; these are all very expensive computational tasks in three dimensions. For small local radii of curvature there is a need for local grid adaption so that the smearing thickness remains a small fraction of the radius of curvature. A special Neumann boundary condition was devised and applied so that the calculated surfactant concentration has no variations normal to the interface, and it is hence truly a surface-defined quantity. The discretized governing equations are solved subsequently using a time-split integration scheme which updates the concentration and the shape successively. Results demonstrate excellent agreement between the computed and exact solutions.

Haj-Hariri, Hossein↗
NASA NTRS1999

A Design Heritage-Based Forecasting Methodology for Risk Informed Management of Advanced Systems

The development of next generation systems often carries with it the promise of improved performance, greater reliability, and reduced operational costs. These expectations arise from the use of novel designs, new materials, advanced integration and production technologies intended for functionality replacing the previous generation. However, the novelty of these nascent technologies is accompanied by lack of operational experience and, in many cases, no actual testing as well. Therefore some of the enthusiasm surrounding most new technologies may be due to inflated aspirations from lack of knowledge rather than actual future expectations. This paper proposes a design heritage approach for improved reliability forecasting of advanced system components. The basis of the design heritage approach is to relate advanced system components to similar designs currently in operation. The demonstrated performance of these components could then be used to forecast the expected performance and reliability of comparable advanced technology components. In this approach the greater the divergence of the advanced component designs from the current systems the higher the uncertainty that accompanies the associated failure estimates. Designers of advanced systems are faced with many difficult decisions. One of the most common and more difficult types of these decisions are those related to the choice between design alternatives. In the past decision-makers have found these decisions to be extremely difficult to make because they often involve the trade-off between a known performing fielded design and a promising paper design. When it comes to expected reliability performance the paper design always looks better because it is on paper and it addresses all the know failure modes of the fielded design. On the other hand there is a long, and sometimes very difficult road, between the promise of a paper design and its fulfillment; with the possibility that sometimes the reliability promise is not fulfilled at all. Decision makers in advanced technology areas have always known to discount the performance claims of a design to a degree in proportion to its stage of development, and at times have preferred the more mature design over the one of lesser maturity even with the latter promising substantially better performance once fielded. As with the broader measures of performance this has also been true for projected reliability performance. Paper estimates of potential advances in design reliability are to a degree uncertain in proportion to the maturity of the features being proposed to secure those advances. This is especially true when performance-enhancing features in other areas are also planned to be part of the development program.

Maggio, Gaspare↗