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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

The Deflection Plate Analyzer: A Technique for Space Plasma Measurements Under Highly Disturbed Conditions

A technique has been developed to measure the characteristics of space plasmas under highly disturbed conditions; e.g., non-Maxwellian plasmas with strong drifting populations and plasmas contaminated by spacecraft outgassing. The present method is an extension of the capabilities of the Differential Ion Flux Probe (DIFP) to include a mass measurement that does not include either high voltage or contamination sensitive devices such as channeltron electron multipliers or microchannel plates. This reduces the complexity and expense of instrument fabrication, testing, and integration of flight hardware as compared to classical mass analyzers. The new instrument design is called the Deflection Plate Analyzer (DPA) and can deconvolve multiple ion streams and analyze each stream for ion flux intensity (density), velocity (including direction of motion), mass, and temperature (or energy distribution). The basic functionality of the DPA is discussed. The performance characteristics of a flight instrument as built for an electrodynamic tether mission, the Propulsive Small Expendable Deployer System (ProSEDS), and the instrument s role in measuring key experimental conditions are also discussed.

Wright, Kenneth H., Jr.↗
NASA NTRS1988

Modulated-Voltage Metastable-Ionization Detector

New detector retains sensitivity of conventional ones but automatically reduces voltage to prevent current saturation at higher values, enabling quantitative determination of relative concentrations approaching 100 percent. Detector includes feedback circuitry to prevent current saturation. When detector current begins to exceed threshold, detector high voltage reduced to keep current from rising much more. Recorder output shows detector-current and voltage-reduction signals from gas mixture with constituents both above and below threshold concentration. Those above threshold cause both current and voltage-reduction peaks. Those below threshold give rise to current peaks only.

Carle, Glenn C.↗
NASA NTRS2002

Macro Fiber Piezocomposite Actuator Poling Study

The performance and advantages of Piezocomposite Actuators are to provide a low cost, in-situ actuator/sensor that is flexible, low profile and high strain per volt performance in the same plane of poled voltage. This paper extends reported data for the performance of these Macrofiber Composite (MFC) Actuators to include 4 progressively narrower Intedigitized electrode configurations with several line widths and spacing ratios. Data is reported for max free strain, average strain per applied volt, poling (alignment of the electric dipoles of the PZT ceramic) voltage vs. strain and capacitance, time to poling voltage 95% saturation. The output strain per volt progressively increases as electrode spacing decreases, with saturation occurring at lower poling voltages. The narrowest spacing ratio becomes prone to voltage breakdown or short circuits limiting the spacing width with current fabrication methods. The capacitance generally increases with increasing poling voltage level but has high sensitivity to factors such as temperature, moisture and time from poling which limit its usefulness as a simple indicator. The total time of applied poling voltage to saturate or fully line up the dipoles in the piezoceramic was generally on the order of 5-20 seconds. Less sensitivity to poling due to the applied rate of voltage increase over a 25 to 500 volt/second rate range was observed.

Werlink, Rudy J.↗
NASA NTRS1995

Method for characterizing the upset response of CMOS circuits using alpha-particle sensitive test circuits

A method for predicting the SEU susceptibility of a standard-cell D-latch using an alpha-particle sensitive SRAM, SPICE critical charge simulation results, and alpha-particle interaction physics. A technique utilizing test structures to quickly and inexpensively characterize the SEU sensitivity of standard cell latches intended for use in a space environment. This bench-level approach utilizes alpha particles to induce upsets in a low LET sensitive 4-k bit test SRAM. This SRAM consists of cells that employ an offset voltage to adjust their upset sensitivity and an enlarged sensitive drain junction to enhance the cell's upset rate.

Buehler, Martin G.↗
NASA NTRS2006

Single Event Transients in Voltage Regulators for FPGA Power Supply Applications

As with other bipolar analog devices, voltage regulators are known to be sensitive to single event transients (SET). In typical applications, large output capacitors are used to provide noise immunity. Therefore, since SET amplitude and duration are generally small, they are often of secondary importance due to this capacitance filtering. In low voltage applications, however, even small SET are a concern. Over-voltages may cause destructive conditions. Under-voltages may cause functional interrupts and may also trigger electrical latchup conditions. In addition, internal protection circuits which are affected by load as well as internal thermal effects can also be triggered from heavy ions, causing dropouts or shutdown ranging from milliseconds to seconds. In the case of FPGA power supplies applications, SETS are critical. For example, in the case of Actel FPGA RTAX family, core power supply voltage is 1.5V. Manufacturer specifies an absolute maximum rating of 1.6V and recommended operating conditions between 1.425V and 1.575V. Therefore, according to the manufacturer, any transient of amplitude greater than 75 mV can disrupt normal circuit functions, and overvoltages greater than 100 mV may damage the FPGA. We tested five low dropout voltage regulators for SET sensitivity under a large range of circuit application conditions.

Poivey, Christian↗
NASA NTRS1986

Cosmic dust detection with large surface piezoceramics

Piezoelectric transducers mounted on targets made out of metal plates or plastic foils have been used in many former space missions to detect impacting dust particles and to determine some of their parameters (e.g., momentum). The proposed detector is based on a large disc made out of piezoceramic material. Dust particles impacting on the detector will cause electrical charge pulses due to the piezoelectric nature of the target material. These charge pulses are measured on the electrodes of the disc and transformed with a charge sensitive amplifier (CSA) to voltage pulses. Counting the number of pulses leads to the dust-flux impacting on the detector. Additionally the amplitude and the rise time of the pulse slopes are determinated to evaluate the momentum and the size of the dust particles. Due to the high charge production rate per force unit of piezoceramics and momentum transfer without loss the sensivity of this acoustic sensor is very high. A method to derive size and momentum from the rising slope of an acoustic signal is described.

Weishaupt, U.↗
NASA NTRS1989

Comparison between field mill and corona point instrumentation at Kennedy Space Center - Use of these data with a model to determine cloudbase electric fields

A novel coronal current-determining instrument is being used at NASA-KSC which overcomes previous difficulties with wind sensitivity and a voltage-threshold 'deadband'. The mounting of the corona needle at an elevated location reduces coronal and electrode layer space-charge influences on electric fields, rendering the measurement of space charge density possible. In conjunction with a space-charge compensation model, these features allow a more realistic estimation of cloud base electric fields and the potential for lightning strike than has previously been possible with ground-based sensors.

Markson, R.↗
NASA NTRS2005

X-ray Polarimetry with a Micro-Pattern Gas Detector

Topics covered include: Science drivers for X-ray polarimetry; Previous X-ray polarimetry designs; The photoelectric effect and imaging tracks; Micro-pattern gas polarimeter design concept. Further work includes: Verify results against simulator; Optimize pressure and characterize different gases for a given energy band; Optimize voltages for resolution and sensitivity; Test meshes with 80 micron pitch; Characterize ASIC operation; and Quantify quantum efficiency for optimum polarization sensitivity.

Hill, Joe↗
NASA NTRS2008

Silicon Photo-Multiplier Readouts for Scintillators in High-Energy Astronomy

New scintillator materials have recently been shown to hold great potential for low-cost, reliable gamma-ray detectors in high-energy astronomy. New devices for the detection of scintillation light promise to make scintillator-based instruments even more attractive by reducing mass and power requirements,in particular, silicon photo-multipliers (SiPMs) are starting to become commercially available that offer gains and quantum efficiencies similar to those of photo-multiplier tubes (PMTs), but with greatly reduced mass, high ruggedness, low voltage requirements, and no sensitivity to magnetic fields. We have conducted laboratory tests of a sample of commercially available SiPMs coupled to LaBr3;Ce, a scintillator of relevance to to future high-energy astrophysics missions. We present results for gamma-ray spectroscopy. compare the SiPM performance to that of a PMT, and discuss the extent to which SiPMs offer significant advantages for scintillator-based space missions.

Bloser, Peter F.↗
NASA NTRS1972

Sensitivity of hot-cathode ionization vacuum gages in several gases

Four hot-cathode ionization vacuum gages were calibrated in 12 gases. The relative sensitivities of these gages were compared to several gas properties. Ionization cross section was the physical property which correlated best with gage sensitivity. The effects of gage accelerating voltage and ionization-cross-section energy level were analyzed. Recommendations for predicting gage sensitivity according to gage type were made.

Holanda, R.↗
NASA NTRS1982

Partial discharge testing under direct voltage conditions

DC partial discharge (PD) (corona) testing is performed using a multichannel analyzer for pulse storing, and data is collected during increase of voltage and at quiescent voltage levels. Thus high voltage ceramic disk capacitors were evaluated by obtaining PD data interspersed during an accelerated life test. Increased PD activity was found early in samples that later failed catastrophically. By this technique, trends of insulation behavior are revealed sensitively and nondestructively in high voltage dc components.

Bever, R. S.↗
NASA NTRS2014

Insulation Resistance and Leakage Currents in Low-Voltage Ceramic Capacitors with Cracks

Measurement of insulation resistance (IR) in multilayer ceramic capacitors (MLCCs) is considered a screening technique that ensures the dielectric is defect-free. This work analyzes the effectiveness of this technique for revealing cracks in ceramic capacitors. It is shown that absorption currents prevail over the intrinsic leakage currents during standard IR measurements at room temperature. Absorption currents, and consequently IR, have a weak temperature dependence, increase linearly with voltage (before saturation), and are not sensitive to the presence of mechanical defects. In contrary, intrinsic leakage currents increase super-linearly with voltage and exponentially with temperature (activation energy is in the range from 0.6 eV to 1.1 eV). Leakage currents associated with the presence of cracks have a weaker dependence on temperature and voltage compared to the intrinsic leakage currents. For this reason, intrinsic leakage currents prevail at high temperatures and voltages, thus masking the presence of defects.

dielectric polarization↗
NASA NTRS2016

Insulation Resistance and Leakage Currents in Low-Voltage Ceramic Capacitors with Cracks

Measurement of insulation resistance (IR) in multilayer ceramic capacitors (MLCCs) is considered a screening technique that ensures the dielectric is defect-free. This work analyzes the effectiveness of this technique for revealing cracks in ceramic capacitors. It is shown that absorption currents prevail over the intrinsic leakage currents during standard IR measurements at room temperature. Absorption currents, and consequently IR, have a weak temperature dependence, increase linearly with voltage (before saturation), and are not sensitive to the presence of mechanical defects. In contrary, intrinsic leakage currents increase super-linearly with voltage and exponentially with temperature (activation energy is in the range from 0.6 eV to 1.1 eV). Leakage currents associated with the presence of cracks have a weaker dependence on temperature and voltage compared to the intrinsic leakage currents. For this reason, intrinsic leakage currents prevail at high temperatures and voltages, thus masking the presence of defects.

testing↗
NASA NTRS1991

Performances of 250 Amp-hr lithium/thionyl chloride cells

A 250 Ah lithium thionyl chloride battery is being developed for a booster rocket engine. Extensive cell testing is running to evaluate functional and safety performances. Some results are presented. The lithium/thionyl chloride batteries were selected for their high energy density (low weight) as compared to other sources. The temperature of a lower weight item will be more sensitive to variations of internal and external heat fluxes than a heavier one. The use of high energy density L/TC batteries is subjected to stringent thermal environments to have benefit of energy density and to stay safe in any conditions. The battery thermal environment and discharge rate have to be adjusted to obtain the right temperature range at cell level, to have the maximum performances. Voltage and capacity are very sensitive to temperature. This temperature is the cell internal actual temperature during discharge. This temperature is directed by external thermal environment and by cell internal heat dissipation, i.e., cell actual voltage.

Goualard, Jacques↗
NASA NTRS1969

Fuse protects circuit from voltage and current overloads

Low-melting resistor connected in series with the load protects the circuit against current overloads. It protects test subjects and patients being monitored by electronic instrumentation from inadvertant overloads of current, and sensitive electronic equipment against high-voltage damage.

Casey, L. O.↗