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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

PTTI applications at Hydro-Quebec

As a power utility, Hydro-Quebec used the PTTI techniques. The time dissemination system in the Hydro-Quebec Network (11th PTTI) is now installed in several points. A portable clock was built using a rubidium standard and associated circuitry which are necessary for the measurements. The apparatus and the experimental results obtained are described. The use of GOES synchronized clocks for making precise voltage angle measurement on the Hydro-Quebec Network is discussed. Some modifications were made on a commercial unit. Applications and results are presented.

Missout, G.↗
NASA NTRS1992

Electrical and infrared properties of thin niobium microbolometers near T(sub c)

Niobium microbolometers approximately 1 micron wide x 2 micron long x 10 nm thick have been integrated at the feeds of equiangular spiral antennas made of 200 nm thick Nb. The device's current-voltage characteristics and infrared responsivity as a function of DC bias voltage were measured over a range of temperature spanning approximately plus or minus 2 percent around T(sub c). The greatest voltage responsivity occurs well below T(sub c), in a regime where the I-V curve is significantly hysteretic due to self-heating and resembles the I-V curve of a superconducting microbridge.

Grossman, E. N.↗
NASA NTRS2004

Development and Characterization of a Low-Pressure Calibration System for Hypersonic Wind Tunnels

Minimization of uncertainty is essential for accurate ESP measurements at very low free-stream static pressures found in hypersonic wind tunnels. Statistical characterization of environmental error sources requires a well defined and controlled calibration method. A calibration system has been constructed and environmental control software developed to control experimentation to eliminate human induced error sources. The initial stability study of the calibration system shows a high degree of measurement accuracy and precision in temperature and pressure control. Control manometer drift and reference pressure instabilities induce uncertainty into the repeatability of voltage responses measured from the PSI System 8400 between calibrations. Methods of improving repeatability are possible through software programming and further experimentation.

Green, Del L.↗
NASA NTRS1987

Effect of component compression on the initial performance of an IPV nickel-hydrogen cell

An experimental method was developed for evaluating the effect of component compression on the charge and discharge voltage characteristics of a 3 1/2 in. diameter boiler plate cell. A standard boiler plate pressure vessel was modified by the addition of a mechanical feedthrough on the bottom of the vessel which permitted different compressions to be applied to the components without disturbing the integrity of the stack. Compression loadings from 0.94 to 27.4 psi were applied by suspending weights from the feedthrough rod. Cell voltages were measured for 0.96-C, 55-min charge and for 1.37-C, 35-min and 2-C, 24-min discharges. An initial change in voltage performance on both charge and discharge as the loading increased was attributed to seating of the components. Subsequent variation of the compression from 2.97 to 27.4 psi caused only minor changes in either the charge or the discharge voltages. Several one month open-circuit voltage stands and 1100 cycles under LEO conditions at the maximum loading have produced no change in performance.

Gahn, Randall F.↗
NASA NTRS1987

Effect of component compression on the initial performance of an IPV nickel-hydrogen cell

An experimental method was developed for evaluating the effect of component compression on the charge and discharge voltage characteristics of a 3 1/2 in. diameter boiler plate cell. A standard boiler plate pressure vessel was modified by the addition of a mechanical feedthrough on the bottom of the vessel which permitted different compressions to be applied to the components without disturbing the integrity of the stack. Compression loadings from 0.94 to 27.4 psi were applied by suspending weights from the feedthrough rod. Cell voltages were measured for 0.96-C, 55-min charge and for 1.37-C, 35-min and 2-C, 24-min discharges. An initial change in voltage performance on both charge and discharge as the loading increased was attributed to seating of the components. Subsequent variation of the compression from 2.97 to 27.4 psi caused only minor changes in either the charge or the discharge voltages. Several one month open-circuit voltage stands and 1100 cycles under LEO conditions at the maximum loading have produced no change in performance.

Gahn, Randall F.↗
NASA NTRS1975

Preliminary measurements of plasma fluctuations in an 8-cm mercury ion thruster

The rms magnitude, spectra, and cross correlations for the fluctuations in the beam current, the neutralizer keeper current, and the discharge current and voltage were measured for an 8-cm diameter, dished grid ion thruster for a beam current of 72 milliamps. The ratio of the rms magnitude of the fluctuations to the time-mean neutralizer keeper current was found to depend significantly on the neutralizer time-mean keeper current, the flow rate, and keeper hold diameter. The maxima of the spectra of the beam current fluctuations did not depend on the discharge fluctuations. It was found that: (1) the discharge current fluctuations do not directly contribute to the beam current fluctuations; and (2) the neutralizer contributions to the beam fluctuations are small (for good neutralizer-to-beam coupling) but not negligible and appear mostly in the higher frequency range measured.

Serafini, J. S.↗
NASA NTRS1979

Area scaling investigations of charging phenomena

The charging and discharging behavior of square, planar samples of silvered, fluorinated ethylene-propylene (FEP) Teflon thermal control tape was measured. The equilibrium voltage profiles scaled with the width of the sample. A wide range of discharge pulse characteristics was observed, and the area dependences of the peak current, charge, and pulse widths are described. The observed scaling of the peak currents with area was weaker than that previously reported. The discharge parameters were observed to depend strongly on the grounding impedance and the beam voltage. Preliminary results suggest that measuring only the return-current-pulse characteristics is not adequate to describe the spacecraft discharging behavior of this material. The seams between strips of tape appear to play a fundamental role in determining the discharging behavior. An approximate propagation velocity for the charge cleanoff was extracted from the data. The samples - 232, 1265, and 5058 square centimeters in area - were exposed at ambient temperature to a 1- to 2-nA/sq cm electron beam at energies of 10, 15, and 20 kilovolts in a 19-meter-long by 4.6-meter-diameter simulation facility at the Lewis Research Center.

Aron, P. R.↗
NASA NTRS2005

Performance test results of a skutterudite-based unicouple with a metallic coating

A performance test of a Skutterudite-based unicouple (MAY-04) with a metallic coating to suppress the sublimation of antimony from the legs near the hot junction is performed in vacuum (~ 9 x10-7 torr) for ~ 2,000 hours at hot and cold junction temperatures of 892.1 + 11.9 K and 316.1 + 5.5 K, respectively. The p-leg is made of CeFe3.5Co0.5Sb12 and the n-leg is made of CoSb3. Presented are the measured voltage-current characteristics, electrical power, open-circuit voltage, and Seebeck coefficients of the legs as functions of cumulative test time. Also presented is the estimate of the conversion efficiency, shortly (~ 96 hrs) after the start of test. To demonstrate the effectiveness of the metallic coating, the measurements for MAY-04 are compared with those of two uncoated unicouples of the same leg materials (MAR-03 and JUN-03), which had been tested earlier. The cross-sectional areas of the legs in MAY-04 are larger than those in MAR-03 and JUN-03, tested in argon cover gas at ~ 0.051-0.068 MPa for 450 and 1200 hours, respectively. The open circuit voltage, Voc (204 mV) of MAY-04 at Beginning-Of-Test (BOT) is almost the same as that of MAR-03, but higher than that of JUN-03 (~180 mV). Although the argon gas effectively decreased antimony loss from legs of MAR-03 and JUN-03, marked degradations in performance occurred with time in these tests. Conversely, the metallic coating in MAY-04 effectively reduced the performance degradation with cumulative test time. The estimated peak efficiency of MAY-04, shortly after BOT (10.65%) is only ~ 0.37 percentage point lower than the theoretical value, assuming zero side heat losses and zero contact resistance per leg. The peak power of MAY- 04 decreased by only ~12%, from its BOT value of ~1.6 We to ~ 1.4 We after ~ 2,000 of cumulative testing

Caillat, Thierry↗
NASA NTRS2006

Using Quasiparticle Poisoning To Detect Photons

According to a proposal, a phenomenon associated with excitation of quasiparticles in certain superconducting quantum devices would be exploited as a means of detecting photons with exquisite sensitivity. The phenomenon could also be exploited to perform medium-resolution spectroscopy. The proposal was inspired by the observation that Coulomb blockade devices upon which some quantum logic gates are based are extremely sensitive to quasiparticles excited above the superconducting gaps in their leads. The presence of quasiparticles in the leads can be easily detected via the charge states. If quasiparticles could be generated in the leads by absorption of photons, then the devices could be used as very sensitive detectors of electromagnetic radiation over the spectral range from x-rays to submillimeter waves. The devices in question are single-Cooper-pair boxes (SCBs), which are mesoscopic superconducting devices developed for quantum computing. An SCB consists of a small superconducting island connected to a reservoir via a small tunnel junction and connected to a voltage source through a gate capacitor. An SCB is an artificial two-level quantum system, the Hamiltonian of which can be controlled by the gate voltage. One measures the expected value of the charge of the eigenvectors of this quantum system by use of a radio-frequency single-electron transistor. A plot of this expected value of charge as a function of gate voltage resembles a staircase that, in the ideal case, consists of steps of height 2 e (where e is the charge of one electron). Experiments have shown that depending on the parameters of the device, quasiparticles in the form of "broken" Cooper pairs present in the reservoir can tunnel to the island, giving rise to steps of 1 e. This effect is sometimes called "poisoning." Simulations have shown that an extremely small average number of quasiparticles can generate a 1-e periodic signal. In a device according to the proposal, this poisoning would be turned to advantage. Depending on the wavelength, an antenna or other component would be used to couple radiation into the reservoir, wherein the absorption of photons would break Cooper pairs, thereby creating quasiparticles that, in turn, would tunnel to the island, creating a 1-e signal. On the basis of conservative estimates of device parameters derived from experimental data and computational simulations that fit the data, it has been estimated that the noise equivalent power of a device according to the proposal could be as low as 6 10(exp -22) W/Hz(exp 1/2). It has also been estimated that the spectroscopic resolution (photon energy divided by increment of photon energy) of such a device in visible light would exceed 100.

Echternach, Pierre↗
NASA NTRS1995

High-voltage space-plasma interactions measured on the PASP Plus test arrays

The Photovoltaic Array Space Power Plus Diagnostics (PASP Plus) experiment was developed by the Air Force's Phillips Laboratory with support from NASA's Lewis Research Center. It was launched on the Advanced Photovoltaic and Electronics EXperiments (APEX) satellite on August 3, 1994 into a 70 degree inclination, 363 km by 2550 km elliptical orbit. This orbit allows the investigation of space plasma effects on high-voltage operation (leakage current at positive voltages and arcing at negative voltages) in the perigee region. PASP Plus is testing twelve solar arrays. There are four planar Si arrays: an old standard type (used as a reference), the large-cell Space Station Freedom (SSF) array, a thin 'APSA' array, and an amorphous Si array. Next are three GaAs on Ge planar arrays and three new material planar arrays, including InP and two multijunction types. Finally, there are two concentrator arrays: a reflective-focusing Mini-Cassegrainian and a Fresnel-lens focusing Mini-Dome. PASP Plus's diagnostic sensors include: Langmuir probe to measure plasma density, an electrostatic analyzer (ESA) to measure the 30 eV to 30 KeV electron/ion spectra and determine vehicle negative potential during positive biasing, and a transient pulse monitor (TPM) to characterize the arcs that occur during the negative biasing. Through positive biasing of its test arrays, PASP Plus investigated the snapover phenomenon, which took place over the range of +100 to +300 V. It was found that array configurations where the interconnects are shielded from the space plasma (i.e., the concentrators or arrays with 'wrap-through' connectors) have lower leakage current. The concentrators exhibited negligible leakage current over the whole range up to +500 V. In the case of two similar GaAs on Ge arrays, the one with 'wrap-through' connectors had lower leakage current than the one with conventional interconnects. Through negative biasing, PASP Plus investigated the arcing rates of its test arrays. The standard Si array, with its old construction (exposed rough-surface interconnects), arced significantly over a wide voltage and plasma-density range. The other arrays arced at very low rates, mostly at voltages greater than -350 V and plasma densities near or greater than 10(exp 5)/cm(exp -3). AS expected according to theory, arcing was more prevalent when array temperatures were cold (based on biasing in eclipse).

Guidice, Donald A.↗
NASA NTRS1982

Pulsed plasma thruster ignitor plug ignition characteristics

The operating characteristics of the semiconductor spark gap ignitor plug used to initiate the discharge in a pulsed plasma thruster are investigated. Current and voltage waveform measurements for the ignitor plug alone, and for the plug mounted in the thruster cathode indicate an average dynamic impedance of 0.2 ohms for a wide range of operating conditions, and a trigger circuit energy transfer efficiency to the plug on the order of 25%. Two modes of trigger ignition are found which are related to the rise time of the applied voltage pulse. Analysis of plasma characteristics reveals plug erosion to occur primarily in the semiconductor and anode regions, by mechanisms including plug metal embrittlement, plasma sputtering and vaporization caused by the discharge current pulse. Measurements also indicate a plume velocity on the order of 1580,000 cm/sec which increases with trigger circuit stored energy. The results establish levels of performance for future applications of semiconductor spark gap ignitor plugs in plasma devices.

Brady, M. E.↗
NASA NTRS2015

Device and Method for Continuously Equalizing the Charge State of Lithium Ion Battery Cells

A method of equalizing charge states of individual cells in a battery includes measuring a previous cell voltage for each cell, measuring a previous shunt current for each cell, calculating, based on the previous cell voltage and the previous shunt current, an adjusted cell voltage for each cell, determining a lowest adjusted cell voltage from among the calculated adjusted cell voltages, and calculating a new shunt current for each cell.

Schwartz, Paul D.↗
NASA NTRS1983

Development of metallization process: FSA project, cell and module formation research area

This experiment is involved in determining bulk resistivity values for different past concentrations. Experiments were performed on silicon Cz and non-Cz wafers. To determine bulk resistivity more accurately, pastes were printed on ceramic substrates. Contact resistance was determined by measuring the voltage drop at constant current. Because of irregularity of grid profiles, accurate determination of cross sections of grid lines is difficult. The bulk resistivity is accurate when the resistivity of the metallization is much less than that of the layer beneath it. When the resistivity of the metal approaches that of the substrate, the actual resistivity will be larger than the measured value.

Garcia, A., III↗
NASA NTRS2001

Beagle 2: The Next Exobiology Mission to Mars

Beagle 2 is a 60 kg probe (with a 30 kg lander) developed in the United Kingdom for inclusion on the European Space Agency's 2003 Mars Express. Beagle 2 will deliver to the Martian surface a payload which consists of a high percentage of science instruments to landed spacecraft mass. Beagle 2 will be launched in June, 2003 with Mars Express on a Soyuz-Fregat rocket from the Baikonur Cosmodrome in Kazakhstan. Beagle 2 will land on Mars on December 26, 2003 in the Isidis Planitia basin (approximately 10 degrees N and 275 degrees W), a large sedimentary basin that overlies the boundary between ancient highlands and northern plains. Isidis Planitia, the third largest basin on Mars, which is possibly filled with sediment deposited at the bottom of long-standing lakes or seas, offers an ideal environment for preserving traces of life. Beagle 2 was developed to search for organic material and other volatiles on and below the surface of Mars in addition to the study of the inorganic chemistry and mineralogy. Beagle 2 will utilize a mechanical mole and grinder to obtain samples from below the surface, under rocks and inside rocks. A pair of stereo cameras will image the landing site along with a microscope for examination of surface and rock samples. Analyses will include both rock and soil samples at various wavelengths, X-ray spectrometer and Mossbauer spectrometer as well as a search for organics and other light element species (e.g. carbonates and water) and measurement of their isotopic compositions. Beagle 2 has as its focus the goal of establishing whether evidence for life existed in the past on Mars at the Isidis Planitia site or at least establishing if the conditions were ever suitable. Carbonates and organic components were first recognized as existing on Mars when they were found in the Martian meteorite Nakhla. Romanek et al showed the carbonates in ALH84001 were formed at low temperatures. McKay et al noted possible evidence of early life on Mars within the ALH84001 meteorite. Thomas-Keprta et al showed the magnetite biomarkers in ALH84001's carbonates are indistinguishable from those formed by magnetotactic bacteria found on Earth. Gibson et al showed there was significant evidence for liquid water and biogenic products present on Mars across a 3.9 billion year period. A mechanical arm (PAW) operates from the lander and is used for science operations along with sample acquisition. Instruments attached to the PAW include: stereo cameras, Mossbauer instrument, X-ray fluorescence instrument, microscope, environmental sensors, rock corer/grinder, a spoon, mirror, brushes, a mole attachment for acquisition of subsurface to depths of 1 to 2 meters and an illumination device. Each camera has 14 filters which have been optimized for mineralogy composition, dust and water vapor detection. The microscope's camera is designed for viewing the size and shape of dust particles, rock surfaces, microfossils, and characteristics of the samples prior to introduction into the gas analysis package (GAP). The camera has a resolution of 4 microns/pixel, features four color capability (red, green, blue and UV (ultraviolet) fluoresence), a depth of focus of 40 micrometers and translation stage of +3 millimeters. The heart of the Beagle 2's life detection package is the gas analysis package (GAP), which consists of a mass spectrometer with collectors at fixed masses for precise isotopic ratio measurements and voltage scanning for spectral analysis. Primary aim of the GAP is to search for the presence of bulk constituents, individual species, and isotopic fractionations for both extinct and extent life along with studying the low-temperature geochemistry of the hydrogen, carbon, nitrogen and oxygen components on Mars from both the surface and atmosphere. GAP is a magnetic sector mass spectrometer with the range of 1 to 140 amu which can be operated in both the static and dynamic modes. A triple Faraday collector array will be used for C, N and O ratios along with a double Faraday array for H/D. Pulse counting electron multiplier will be utilized for noble gases and selected organics. Anticipated detection limits are at the picomole level for operation in the static mode of operation and high precision isotopic measurements will be made in the dynamic mode. Sample processing and preparation system consists of reaction vessels along with references. Sample ovens capable of being heated are attached to the manifold for sample combustion. Surface, subsurface materials and interior rock specimens will be combusted in pure oxygen gas at various temperature intervals to release organic matter and volatiles. Combustion process will permit detection of all forms and all atoms of carbon present in the samples. A chemical processing system is capable of a variety of conversion reactions. Gases are manipulated either by cryogenic or chemical reactions and passed through the gas handling portion of the vacuum system. There are two modes of operation: quantitative analysis and precise isotopic measurements. Additional information is contained in the original extended abstract.

Gibson, Everett K., Jr.↗
NASA NTRS1995

Hot-wire calibration in subsonic/transonic flow regimes

A different approach for calibrating hot-wires, which simplifies the calibration procedure and reduces the tunnel run-time by an order of magnitude was sought. In general, it is accepted that the directly measurable quantities in any flow are velocity, density, and total temperature. Very few facilities have the capability of varying the total temperature over an adequate range. However, if the overheat temperature parameter, a(sub w), is used to calibrate the hot-wire then the directly measurable quantity, voltage, will be a function of the flow variables and the overheat parameter i.e., E = f(u,p,a(sub w), T(sub w)) where a(sub w) will contain the needed total temperature information. In this report, various methods of evaluating sensitivities with different dependent and independent variables to calibrate a 3-Wire hot-wire probe using a constant temperature anemometer (CTA) in subsonic/transonic flow regimes is presented. The advantage of using a(sub w) as the independent variable instead of total temperature, t(sub o), or overheat temperature parameter, tau, is that while running a calibration test it is not necessary to know the recovery factor, the coefficients in a wire resistance to temperature relationship for a given probe. It was deduced that the method employing the relationship E = f (u,p,a(sub w)) should result in the most accurate calibration of hot wire probes. Any other method would require additional measurements. Also this method will allow calibration and determination of accurate temperature fluctuation information even in atmospheric wind tunnels where there is no ability to obtain any temperature sensitivity information at present. This technique greatly simplifies the calibration process for hot-wires, provides the required calibration information needed in obtaining temperature fluctuations, and reduces both the tunnel run-time and the test matrix required to calibrate hotwires. Some of the results using the above techniques are presented in an appendix.

Nagabushana, K. A.↗
NASA NTRS2015

Evaluation of Case Size 0603 BME Ceramic Capacitors

High volumetric efficiency of commercial base metal electrode (BME) ceramic capacitors allows for a substantial reduction of weight and sizes of the parts compared to currently used military grade precious metal electrode (PME) capacitors. Insertion of BME capacitors in space applications requires a thorough analysis of their performance and reliability. In this work, six types of cases size 0603 BME capacitors from three vendors have been evaluated. Three types of multilayer ceramic capacitors (MLCCs) were designed for automotive industry and three types for general purposes. Leakage currents in the capacitors have been measured in a wide range of voltages and temperatures, and measurements of breakdown voltages (VBR) have been used to assess the proportion and severity of defects in the parts. The effect of soldering-related thermal shock stresses was evaluated by analysis of distributions of VBR for parts in 'as is' condition and after terminal solder dip testing at 350 C. Highly Accelerated Life Testing (HALT) at different temperatures was used to assess the activation energy of degradation of leakage currents and predict behavior of the parts at life test and normal operating conditions. To address issues related to rework and manual soldering, capacitors were soldered onto different substrates at different soldering conditions. The results show that contrary to a common assumption that large-size capacitors are mostly vulnerable to soldering stresses, cracking in small size capacitors does happen unless special measures are taken during assembly processes.

testing↗