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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

A Thermal Runaway Failure Model for Low-Voltage BME Ceramic Capacitors with Defects

Reliability of base metal electrode (BME) multilayer ceramic capacitors (MLCCs) that until recently were used mostly in commercial applications, have been improved substantially by using new materials and processes. Currently, the inception of intrinsic wear-out failures in high quality capacitors became much greater than the mission duration in most high-reliability applications. However, in capacitors with defects degradation processes might accelerate substantially and cause infant mortality failures. In this work, a physical model that relates the presence of defects to reduction of breakdown voltages and decreasing times to failure has been suggested. The effect of the defect size has been analyzed using a thermal runaway model of failures. Adequacy of highly accelerated life testing (HALT) to predict reliability at normal operating conditions and limitations of voltage acceleration are considered. The applicability of the model to BME capacitors with cracks is discussed and validated experimentally.

reliability↗
DOE OSTI2024

High-Power Oak Ridge Converter (ORC) for Extreme Fast Charging Applications

This project report presents a novel power converter system called Oak Ridge Converter (ORC), a patented technology developed by the Oak Ridge National Laboratory (ORNL) for XFC wireless EV charging systems. ORC integrates the grid interface converter (also known as the active front-end rectifier with power factor correction) with the high-frequency inverter stage, promoting size and cost-effective charging technology with reduced infrastructure costs. The integration of the front-end rectifier with the high-frequency inverter truly eliminates one power conversion stage and achieves more than 33% size, weight, volume, and cost reduction on the wireless charging systems. Furthermore, ORC eliminates the primary side direct current (DC) bus bulk capacitors that are usually aluminum electrolytic capacitors and replaces them with very small, cost-effective, highly reliable, and high-temperature operation-capable alternate current (AC) film capacitors. ORC is also applicable to both single-phase and poly-phase couplers. When used with polyphase couplers, ORC further improves the power density of the overall system with higher power density power electronics. Moreover, ORC is inherently bidirectional and allows the system to provide power back to the grid for grid ancillary or grid support services. The ORC, based on a patented ORNL technology, is an excellent approach to resolving the high-power charging problems as described above, which directly converts the 60 hertz (Hz) line frequency into high frequency (i.e., 85 kilohertz (kHz)) to use with a high-frequency isolation transformer or wireless charging coils while eliminating the primary side number of power conversion stages from two to one. The result of the project is a prototype and reference design for a high-power wireless charging system—including power electronics, magnetics, and thermal—serving as a baseline for product development. The proposed system results are demonstrated for 270 kW of output power, with the system's overall efficiency of 92% from the AC grid, achieving less than 3% current total harmonic distortion (THD) and around 0.99 power factor (PF).

33 ADVANCED PROPULSION SYSTEMS↗
NASA NTRS2015

Leakage Currents and Gas Generation in Advanced Wet Tantalum Capacitors

Currently, military grade, established reliability wet tantalum capacitors are among the most reliable parts used for space applications. This has been achieved over the years by extensive testing and improvements in design and materials. However, a rapid insertion of new types of advanced, high volumetric efficiency capacitors in space systems without proper testing and analysis of degradation mechanisms might increase risks of failures. The specifics of leakage currents in wet electrolytic capacitors is that the conduction process is associated with electrolysis of electrolyte and gas generation resulting in building up of internal gas pressure in the parts. The risk associated with excessive leakage currents and increased pressure is greater for high value advanced wet tantalum capacitors, but it has not been properly evaluated yet. In this work, in Part I, leakages currents in various types of tantalum capacitors have been analyzed in a wide range of voltages, temperatures, and time under bias. Gas generation and the level of internal pressure have been calculated in Part II for different case sizes and different hermeticity leak rates to assess maximal allowable leakage currents. Effects related to electrolyte penetration to the glass seal area have been studied and the possibility of failures analyzed in Part III. Recommendations for screening and qualification to reduce risks of failures have been suggested.

degradation mechanisms↗
DOE OSTI2023

Characterization of superconducting through-silicon vias as capacitive elements in quantum circuits

The large physical size of superconducting qubits and their associated on-chip control structures presents a practical challenge toward building a large-scale quantum computer. In particular, transmons require a high-quality-factor shunting capacitance that is typically achieved by using a large coplanar capacitor. Other components, such as superconducting microwave resonators used for qubit state readout, are typically constructed from coplanar waveguides, which are millimeters in length. Here, we use compact superconducting through-silicon vias to realize lumped-element capacitors in both qubits and readout resonators to significantly reduce the on-chip footprint of both of these circuit elements. We measure two types of devices to show that through-silicon vias are of sufficient quality to be used as capacitive circuit elements and provide a significant reduction in size over existing approaches.

Physics↗
DOE OSTI2020

CCM vs. CRM Design Optimization of a Boost-derived Parallel Active Power Decoupler for Microinverter Applications

Single-phase inverter or rectifier systems often make use of an auxiliary active power decoupler (APD) to balance the mismatch between steady DC power and fluctuating AC power. This paper deals with efficiency and size optimization of a parallel boost-type APD circuit for PV microinverter applications. Specifically, design of an eGaNFET-based, 400 W APD circuit, employing planar inductor and operating in either continuous conduction mode (CCM) or critical conduction mode (CRM) is considered. Available design variables including inductance value, inductor core geometry, capacitor voltage, switching frequency, and modulation scheme (CCM vs. CRM) are explored to identify Pareto-optimal configurations, which can achieve low California Energy Commission (CEC) efficiency drop while also reducing the footprint area of the inductor. The theoretical study predicts that the optimal CRM design can achieve 37% reduced inductor size, while operating with similar efficiency drop, compared to the optimal CCM design. Experimental results, obtained using two separate 40 V, 400 W hardware prototypes for CCM and CRM, are presented to verify the analyses.

14 SOLAR ENERGY↗
NASA NTRSDate not supplied

Cryogenic Modules for Synergistic O2 Generation and CO2 Retention in Closed-Circuit Escape Respirators

Since 2018, NASA and the National Institute for Occupational Safety and Health (NIOSH) have been developing a liquid oxygen storage module (LOXSM) based on the NASA patent-pending Cryogenic Flux Capacitor (CFC) technology. LOXSM’s could potentially replace the gaseous or chemical-based oxygen supply in current closed-circuit escape respirators (CCER), with reducing CCER size being a primary goal. By virtue of the CFC functionality, cryogenic oxygen stored within the LOXSM is released in response to heat input, ideally from the breathing loop. Prior efforts focused on the oxygen storage potential of silica aerogel materials that the CFC utilizes, and were previously reported. Current work explored the LOXSM’s potential to remove and retain CO 2 produced by the CCER user, in conjunction with oxygen generation, creating a synergy that may be exploited to reduce or eliminate the chemical CO 2 absorber used in current CCERs. A test program for determining CO 2 retention is presented, as well as the evolution of LOXSM prototypes. Testing showed that it is possible to completely remove CO 2 out of an effluent stream at the flowrate required for the capacity of the CCER for an appreciable time, and that the LOXSM prototype design progression had a positive effect on that duration.

A.M. Swanger↗
NASA NTRS1994

Capaciflector camera

A capacitive type proximity sensor having improved range and sensitivity between a surface and an intruding object in the vicinity of the surface having a voltage source, a number of outer electrical conductors on the surface with each forming one electrode of a number of sensor capacitors, the other electrode for each sensor capacitor being the object. The outer conductors are made from thin sheets of conductive material covered with insulation. An intermediate electrical conductor is located between the outer conductors and the surface and is of a size larger than the outer conductors to act as a shield for reducing the parasitic capacitance between the outer conductors and the surface. The intermediate conductor is also made from a thin sheet of conductive material covered with insulation. The outer conductors and the intermediate conductor are attached to the surface with no gap between the insulation on the conductors and no gap between the surface and the insulation on intermediate conductor, the outer conductors and the intermediate conductor conjoining with each other and with the surface, with the surface acting as a ground plane. A current-measuring voltage follower circuit is connected to the voltage source for coupling in phase and amplitude the instantaneous voltage at the voltage source to the outer electrical conductors and the intermediate electrical conductor. This circuit is responsive to the change in capacitance of the sensor capacitors and generates a number of output signals.

Vranish, John M.↗
NASA NTRS1994

Reducing Ripple In A Switching Voltage Regulator

Ripple voltage in output of switching voltage regulator reduced substantially by simple additional circuitry adding little to overall weight and size of regulator. Heretofore, additional filtering circuitry needed to obtain comparable reductions in ripple typically as large and heavy as original regulator. Current opposing ripple current injected into filter capacitor.

Paulkovich, John↗
NASA NTRS1993

Capaciflector camera

A capacitive type proximity sensor having improved range and sensitivity between a surface and an intruding object in the vicinity of the surface having a voltage source, a number of outer electrical conductors on the surface with each forming one electrode of a number of sensor capacitors, the other electrode for each sensor capacitor being the object is described. The outer conductors are made from thin sheets of conductive material covered with insulation. An intermediate electrical conductor is located between the outer conductors and the surface and is of a size larger than the outer conductors to act as a shield for reducing the parasitic capacitance between the outer conductors and the surface. The intermediate conductor is also made from a thin sheet of conductive material covered with insulation. The outer conductors and the intermediate conductor are attached to the surface with no gap between the insulation on the conductors and no gap between the surface and the insulation on intermediate conductor, the outer conductors and the intermediate conductor conjoining with each other and with the surface, with the surface acting as a ground plane. A current-measuring voltage follower circuit is connected to the voltage source for coupling in phase and amplitude the instantaneous voltage at the voltage source to the outer electrical conductors and the intermediate electrical conductor. This circuit is responsive to the change in capacitance of the sensor capacitors and generates a number of output signals.

Vranish, John M.↗
NASA NTRS1977

Testing of typical spacecraft materials in a simulated substorm environment

The test specimens were spacecraft paints, silvered Teflon, thermal blankets, and solar array segments. The samples, ranging in size from 300 to 1000 sq cm were exposed to monoenergetic electron energies from 2 to 20 keV at a current density of 1 NA/sq cm. The samples generally behaved as capacitors with strong voltage gradient at their edges. The charging characteristics of the silvered Teflon, Kapton, and solar cell covers were controlled by the secondary emission characteristics. Insulators that did not discharge were the spacecraft paints and the quartz fiber cloth thermal blanket sample. All other samples did experience discharges when the surface voltage reached -8 to -16kV. The discharges were photographed. The breakdown voltage for each sample was determined and the average energy lost in the discharge was computed.

Stevens, N. J.↗
NASA NTRS1976

Testing of typical spacecraft materials in a simulated substorm environment

An investigation to determine spacecraft materials characteristics under charging conditions was conducted at the Lewis Research Center substorm simulation facility. The test specimens were spacecraft paints, silvered Teflon, thermal blankets and solar array segments. The samples, ranging in size from 300 to 1,000 sq cm were exposed to monoenergetic electron energies from 2 to 20 keV at a current density of 1 nA sq cm. The samples generally behaved as capacitors with strong voltage gradients at their edges. The charging characteristics of the silvered Teflon, Kapton, and solar cell covers were controlled by the secondary emission characteristics. Insulators that did not discharge were the spacecraft paints and the quartz fiber cloth thermal blanket sample. All other samples did experience discharges when the surface voltage reached -8 to -16 kV. The discharges were photographed. The breakdown voltage for each sample was determined and the average energy lost in the discharge was computed.

Stephens, N. J.↗
NASA NTRS2003

Advanced sensor systems for biotelemetry

The present invention relates to telemetry-based sensing systems that continuously measures physical, chemical and biological parameters. More specifically, these sensing systems comprise a small, modular, low-power implantable biotelemetry system capable of continuously sensing physiological characteristics using implantable transmitters, a receiver, and a data acquisition system to analyze and record the transmitted signal over several months. The preferred embodiment is a preterm labor and fetal monitoring system. Key features of the invention include Pulse Interval Modulation (PIM) that is used to send temperature and pressure information out of the biological environment. The RF carrier frequency is 174-216 MHz and a pair of RF bursts (pulses) is transmitted at a frequency of about 1-2 Hz. The transmission range is 3 to 10 feet, depending on the position of the transmitter in the body and its biological environment. The entire transmitter is encapsulated in biocompatible silicone rubber. Power is supplied by on-board silver-oxide batteries. The average power consumption of the current design is less than 30 .mu.W., which yields a lifetime of approximately 6-9 months. Chip-on-Board technology (COB) drastically reduces the size of the printed circuit board from 38.times.28 mm to 22.times.8 mm. Unpackaged dies are flip-chip bonded directly onto the printed circuit board, along with surface mount resistors and capacitors. The invention can monitor additional physiological parameters including, but not limited to, ECG, blood gases, glucose, and ions such as calcium, potassium, and sodium.

Hines, John W.↗
NASA NTRS2006

Nearly Direct Measurement of Relative Permittivity

A recently conceived technique for determining the relative permittivity of a material sample at a given frequency is more nearly direct than are prior techniques that involve measurement of such related non-electrical quantities as the size, shape, and/or weight of the specimen. The present technique involves only measurement of two voltages at the frequency in question, followed by calculation of the ratio between the voltages. The technique requires two circuits a test circuit and a reference circuit that are identical except as described below. Each circuit includes a capacitor C1 connected in series with a much larger capacitor C2 to form a voltage divider (see figure). C1 is a parallel-plate capacitor. The top electrode of C1 is connected to an AC signal source of voltage Va at the frequency of interest. The top electrode of C1 is surrounded by a guard electrode that, in turn, is surrounded by a grounded electrode. The bottom electrode of C1 is connected to the top electrode of C2. The bottom electrode of C2 is grounded. The volume enclosed by the top, bottom, and guard electrodes of C1 constitutes a sample cell. A material sample, having relative permittivity k at the frequency of interest, is placed in the sample cell. The exact shape and size of the sample volume is not critical and can be chosen to fit the material sample. What is critical is that (a) C2 in both circuits be identical and (b) the sample cell in the test circuit have the same size and shape as that in the reference circuit, so that the capacitances of the two sample cells are proportional to the permittivities of their contents.

Calle, Carlos I.↗
NASA NTRS2003

Advanced Sensor Systems for Biotelemetry

The present invention relates to telemetry-based sensing systems that continuously measures physical, chemical and biological parameters. More specifically, these sensing systems comprise a small, modular, low-power implantable biotelemetry system capable of continuously sensing physiological characteristics using implantable transmitters, a receiver, and a data acquisition system to analyze and record the transmitted signal over several months. The preferred embodiment is a preterm labor and fetal monitoring system. Key features of the invention include Pulse Interval Modulation (PIM) that is used to send temperature and pressure information out of the biological environment. The RF carrier frequency is 174-216 MHz and a pair of RF bursts (pulses) is transmitted at a frequency of about 1-2 Hz. The transmission range is 3 to 10 feet, depending on the position of the transmitter in the body and its biological environment. The entire transmitter is encapsulated in biocompatible silicone rubber. Power is supplied by on-board silver-oxide batteries. The average power consumption of the current design is less than 30 microW, which yields a lifetime of approximately 6 - 9 months. Chip-on-Board technology (COB) drastically reduces the size of the printed circuit board from 38 x 28 mm to 22 x 8 mm. Unpackaged dies are flip-chip bonded directly onto the printed circuit board, along with surface mount resistors and capacitors. The invention can monitor additional physiological parameters including, but not limited to, ECG, blood gases, glucose, and ions such as calcium, potassium, and sodium.

Hines, John W.↗
NASA NTRS1994

Hypervelocity Impact Test Facility: A gun for hire

An affordable technique has been developed to duplicate the types of impacts observed on spacecraft, including the Shuttle, by use of a certified Hypervelocity Impact Facility (HIF) which propels particulates using capacitor driven electric gun techniques. The fully operational facility provides a flux of particles in the 10-100 micron diameter range with a velocity distribution covering the space debris and interplanetary dust particle environment. HIF measurements of particle size, composition, impact angle and velocity distribution indicate that such parameters can be controlled in a specified, tailored test designed for or by the user. Unique diagnostics enable researchers to fully describe the impact for evaluating the 'targets' under full power or load. Users regularly evaluate space hardware, including solar cells, coatings, and materials, exposing selected portions of space-qualified items to a wide range of impact events and environmental conditions. Benefits include corroboration of data obtained from impact events, flight simulation of designs, accelerated aging of systems, and development of manufacturing techniques.

Johnson, Calvin R.↗
DOE OSTI2020

Ultrahigh capacitive energy density in ion-bombarded relaxor ferroelectric films

Dielectric capacitors can store and release electric energy at ultrafast rates and are extensively studied for applications in electronics and electric power systems. Among various candidates, thin films based on relaxor ferroelectrics, a special kind of ferroelectric with nanometer-sized domains, have attracted special attention because of their high energy densities and efficiencies. We show that high-energy ion bombardment improves the energy storage performance of relaxor ferroelectric thin films. Intrinsic point defects created by ion bombardment reduce leakage, delay low-field polarization saturation, enhance high-field polarizability, and improve breakdown strength. We demonstrate energy storage densities as high as ~133 joules per cubic centimeter with efficiencies exceeding 75%. Deterministic control of defects by means of postsynthesis processing methods such as ion bombardment can be used to overcome the trade-off between high polarizability and breakdown strength.

Kim, Jieun↗
NASA NTRS1981

Preliminary design development of 100 KW rotary power transfer device

Contactless power transfer devices for transferring electrical power across a rotating spacecraft interface were studied. A power level of 100 KW was of primary interest and the study was limited to alternating current devices. Rotary transformers and rotary capacitors together with the required dc to ac power conditioning electronics were examined. Microwave devices were addressed. The rotary transformer with resonant circuit power conditioning was selected as the most feasible approach. The rotary capacitor would be larger while microwave devices would be less efficient. A design analysis was made of a 100 KW, 20 kHz power transfer device consisting of a rotary transformer, power conditioning electronics, drive mechanism and heat rejection system. The size, weight and efficiency of the device were determined. The characteristics of a baseline slip ring were presented. Aspects of testing the 100 KW power transfer device were examined. The power transfer device is a feasible concept which can be implemented using presently available technologies.

Weinberger, S. M.↗
NASA NTRS1994

Steering capaciflector sensor

A capacitive type proximity sensor having substantial range and sensitivity between a machine and an intruding object in the immediate vicinity of the machine and having a steerable sensing field has an outer electrical conductor on the machine forming one electrode of a sensor capacitor, the other electrode is the object. The outer conductor is a thin sheet of conductive material with a pair (or more) of intermediate electrical conductors located between the outer conductor and the machine. The pair of intermediate electrical conductors are in close proximity to each other and together form a surface having a size substantially larger than the outer conductor to act as a shield for reducing the parasitic capacitance between the outer conductor and the machine and to steer the sensor field. The pair of intermediate conductors are thin sheets of conductive material substantially wider than the first conductor. The outer and pair of intermediate conductors are attached to a surface on the machine in electrical isolation and with no gaps between the conductors and no gap between the surface and the pair of intermediate conductors. The outer and pair of intermediate conductors are also in conformance with each other and the surface of the machine, and the surface of the machine acts as a ground plane. Variable gain voltage follower circuits are used for coupling, in phase, the instantaneous voltage at the outer electrical conductor to the pair of intermediate electrical conductors and a signal generator is coupled to the outer conductor and is responsive to the capacitance of the sensor capacitor for generating a control signal to the machine.

Jenstrom, Del T.↗