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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Endurance test and evaluation of alkaline water electrolysis cells

Utilization in the development of multi-kW low orbit power systems is discussed. The following technological developments of alkaline water electrolysis cells for space power application were demonstrated: (1) four 92.9 cm2 single water electrolysis cells, two using LST's advanced anodes and two using LST's super anodes; (2) four single cell endurance test stands for life testing of alkaline water electrolyte cells; (3) the solid performance of the advanced electrode and 355 K; (4) the breakthrough performance of the super electrode; (5) the four single cells for over 5,000 hours each significant cell deterioration or cell failure. It is concluded that the static feed water electrolysis concept is reliable and due to the inherent simplicity of the passive water feed mechanism coupled with the use of alkaline electrolyte has greater potential for regenerative fuel cell system applications than alternative electrolyzers. A rise in cell voltage occur after 2,000-3,000 hours which was attributed to deflection of the polysulfone end plates due to creepage of the thermoplastic. More end plate support was added, and the performance of the cells was restored to the initial performance level.

Burke, K. A.↗
NASA NTRSDate not supplied

Predicting Thermal Response in a Li-ion Cell on a UAV Fight Profile

As the energy storage devices continue to "pack" more energy in a small space, any damage, battery component failure, manufacturing defect, or electrically abusing the battery can lead to catastrophic thermal runaway events. A catastrophic thermal event in a cell leads to high temperature, in some instances spewing of battery materials due to gas development from side reactions initiated due to high internal temperatures. Also, a thermal runaway event can propagate from a single "failed" cell to the pack in a battery pack, leading to a more significant event. Mitigating a thermal runaway event is important in the commercial and automotive sectors. However, preventing such events in an electric aircraft (or air taxis) is paramount due to the lack of alternatives in the event of a failure. Battery prognostics algorithms allow the prediction of state-of-charge (SOC) and end-of-life (EOL) of a Li-ion battery in a UAV (unmanned air vehicle) [1]. For this presentation, we will extend this two-level battery predictive algorithm to predict SOC, EOL, and estimated maximum temperature during a simulated flight. The model is extended by integrating a lumped physics-driven thermal model for high current densities [2]. The parameters used to control SOC and EOL are maximum storable charge, time constant for Li-ion diffusivity in the carbon particles, and internal cell resistance. Cycling leads to an increase in the heat generated by an aged Li-ion cell with a LiyCoO2 (LCO) cathode and a LixC6 (MCMB) anode. The aging of a cell leads to increase in SEI layer thickness, the diffusion time for the lithium ions inside the electrodes, and the local reaction rates, in addition to the thermodynamic abuse caused by fixed cycling voltages controlled by a Battery Management System. As the battery ages, the cell resistance increases, while the onset temperature of the thermal runaway decreases (depends on the cell chemistry and cell abuse history). Any large deviation of the cell temperature from the estimated (expected) value can identify a faulty cell. Since SEI decomposition has the lowest onset temperature in the series of reactions leading to thermal runaway, the model considers the self-heating rate of the SEI decomposition as onset temperature (similar to Ref. [3]). The parameters in the Arrhenius equation for the SEI heating rate depend on the number of cycles, the cell's operating temperature, and the cell's abuse history [4,5]. Coupling the electrochemical, thermal, and aging model allow the prognostic algorithm to estimate a typical cell voltage and temperature as a function of age (cycling and calendar), whose departure from measured values from the BMS is used to identify a safety event. In addition, we will present the results from two simulated flight scenarios for a UAV: typical and extreme, since the power requirements vary significantly during take-off, landing, and changing altitudes, while the power requirements remain low during the cruise. For this presentation, the power requirement for a battery pack in a UAV is scaled to a single cell. This cell is cycled through a simulated profile, and the data is collected and used to predict a safety event.

Li-ion↗
NASA NTRS1992

Monolithic and mechanical multijunction space solar cells

High-efficiency, lightweight, radiation-resistant solar cells are essential to meet the large power requirements of future space missions. Single-junction cells are limited in efficiency. Higher cell efficiencies could be realized by developing multijunction, multibandgap solar cells. Monolithic and mechanically stacked tandem solar cells surpassing single-junction cell efficiencies have been fabricated. This article surveys the current status of monolithic and mechanically stacked multibandgap space solar cells, and outlines problems yet to be resolved. The monolithic and mechanically stacked cells each have their own problems related to size, processing, current and voltage matching, weight, and other factors. More information is needed on the effect of temperature and radiation on the cell performance. Proper reference cells and full-spectrum range simulators are also needed to measure efficiencies correctly. Cost issues are not addressed, since the two approaches are still in the developmental stage.

Jain, Raj K.↗
NASA NTRS1990

Future mission opportunities and requirements for advanced space photovoltaic energy conversion technology

The variety of potential future missions under consideration by NASA will impose a broad range of requirements on space solar arrays, and mandates the development of new solar cells which can offer a wide range of capabilities to mission planners. Major advances in performance have recently been achieved at several laboratories in a variety of solar cell types. Many of those recent advances are reviewed, the areas are examined where possible improvements are yet to be made, and the requirements are discussed that must be met by advanced solar cell if they are to be used in space. The solar cells of interest include single and multiple junction cells which are fabricated from single crystal, polycrystalline and amorphous materials. Single crystal cells on foreign substrates, thin film single crystal cells on superstrates, and multiple junction cells which are either mechanically stacked, monolithically grown, or hybrid structures incorporating both techniques are discussed. Advanced concentrator array technology for space applications is described, and the status of thin film, flexible solar array blanket technology is reported.

Flood, Dennis J.↗
NASA NTRS2003

A Comparison between Growth Morphology of "Eutectic" Cells/Dendrites and Single-Phase Cells/Dendrites

Directionally solidified (DS) intermetallic and ceramic-based eutectic alloys with an in-situ composite microstructure containing finely distributed, long aspect ratio, fiber, or plate reinforcements are being seriously examined for several advanced aero-propulsion applications. In designing these alloys, additional solutes need to be added to the base eutectic composition in order to improve heir high-temperature strength, and provide for adequate toughness and resistance to environmental degradation. Solute addition, however, promotes instability at the planar liquid-solid interface resulting in the formation of two-phase eutectic "colonies." Because morphology of eutectic colonies is very similar to the single-phase cells and dendrites, the stability analysis of Mullins and Sekerka has been extended to describe their formation. Onset of their formation shows a good agreement with this approach; however, unlike the single-phase cells and dendrites, there is limited examination of their growth speed dependence of spacing, morphology, and spatial distribution. The purpose of this study is to compare the growth speed dependence of the morphology, spacing, and spatial distribution of eutectic cells and dendrites with that for the single-phase cells and dendrites.

Tewari, S. N.↗
NASA NTRS1995

Laboratory instrumentation and techniques for characterizing multi-junction solar cells for space applications

Multi-junction solar cells are attractive for space applications because they can be designed to convert a larger fraction of AMO into electrical power at a lower cost than single-junction cells. The performance of multi-junction cells is much more sensitive to the spectral irradiance of the illuminating source than single-junction cells. The design of high efficiency multi-junction cells for space applications requires matching the optoelectronic properties of the junctions to AMO spectral irradiance. Unlike single-junction cells, it is not possible to carry out quantum efficiency measurements using only a monochromatic probe beam and determining the cell short-circuit current assuming linearity of the quantum efficiency. Additionally, current-voltage characteristics can not be calculated from measurements under non-AMO light sources using spectral-correction methods. There are reports in the literature on characterizing the performance of multi junction cells by measuring and convoluting the quantum efficiency of each junction with the spectral irradiance; the technique is of limited value for the characterization of cell performance under AMO power-generating conditions. We report the results of research to develop instrumentation and techniques for characterizing multi junction solar cells for space . An integrated system is described which consists of a standard lamp, spectral radiometer, dual-source solar simulator, and personal computer based current-voltage and quantum efficiency equipment. The spectral radiometer is calibrated regularly using the tungsten-halogen standard lamp which has a calibration based on NIST scales. The solar simulator produces the light bias beam for current-voltage and cell quantum efficiency measurements. The calibrated spectral radiometer is used to 'fit' the spectral irradiance of the dual-source solar simulator to WRL AMO data. The quantum efficiency apparatus includes a monochromatic probe beam for measuring the absolute cell quantum efficiency at various voltage biases, including the voltage bias corresponding to the maximum-power point under AMO light bias. The details of the procedures to 'fit' the spectral irradiance to AMO will be discussed. An assessment of the role of the accuracy of the 'fit' of the spectral irradiance and probe beam intensity on measured cell characteristics will be presented. quantum efficiencies were measured with both spectral light bias and AMO light bias; the measurements show striking differences. Spectral irradiances were convoluted with cell quantum efficiencies to calculate cell currents as function of voltage. The calculated currents compare with measured currents at the 1% level. Measurements on a variety of multi-junction cells will be presented. The dependence of defects in junctions on cell quantum efficiencies measured under light and voltage bias conditions will be presented. Comments will be made on issues related to standards for calibration, and limitations of the instrumentation and techniques. Expeditious development of multi-junction solar cell technology for space presents challenges for cell characterization in the laboratory.

Woodyard, James R.↗
NASA NTRS1982

Progress toward thin-film GaAs solar cells using a single-crystal Si substrate with a Ge interlayer

Development of a technology for fabricating light-weight, high-efficiency, radiation-resistant solar cells for space applications is reported. The approaches currently adopted are to fabricate shallow homojunction n(+)/p as well as p/n AlGaAs-heteroface GaAs solar cells by organometallic chemical vapor deposition (OM-CVD) on single-crystal Si substrates using in each case, a thin Ge epi-interlayer first grown by CVD. This approach maintains the advantages of the low specific gravity of Si as well as the high efficiency and radiation-resistant properties of the GaAs solar cell which can lead to greatly improved specific power for a solar array. The growth of single-crystal GaAs epilayers on Ge epi-interlayers on Si substrates is investigated. Related solar cell fabrication is reviewed.

Yeh, Y. C. M.↗
NASA NTRS1984

Microcrystalline silicon growth for heterojunction solar cells

A single source of evaporation with B mixed with highly doped Si is used instead of the coevaporation of separate Si and B sources to reduce possible carbon contamination. The results of both the heterojunction or heteroface structures, however, are similar when evaporation is used. The best Voc of the heterojunction is about 460mV and no improvement in Voc in the heteroface structure is observed. Slight Voc degradation occurred. A study of the p m-Si/p c-Si structure showed a negative Voc in many cases. The interface properties between the two materials are such that instead of repelling minority carriers from the substrate carrier, collection actually occurred. Another study of cells made in the part of substrates not covered by n-Si results in performance lower than the controls. This indicates possible substrate degradation in the process.

Iles, P. A.↗
NASA NTRS1991

Performance of a dual anode nickel-hydrogen cell

An experimental study was conducted to characterize the voltage performance of a nickel-hydrogen cell containing a hydrogen electrode on both sides of the nickel electrode. The dual anode cell was compared with a conventional single anode cell using the same nickel electrode. Higher discharge voltages and lower charge voltages were obtained with the dual anode cell during constant current discharges to 10C, pulse discharges to 8C, and polarization measurements at 50% state-of-charge.

Randall F Gahn↗
NASA NTRS2009

Battery Cell Voltage Sensing and Balancing Using Addressable Transformers

A document discusses the use of saturating transformers in a matrix arrangement to address individual cells in a high voltage battery. This arrangement is able to monitor and charge individual cells while limiting the complexity of circuitry in the battery. The arrangement has inherent galvanic isolation, low cell leakage currents, and allows a single bad cell in a battery of several hundred cells to be easily spotted.

Davies, Francis↗
NASA NTRS1984

Experimental Investigation of Shock-Cell Noise Reduction for Single Stream Nozzles in Simulated Flight

Seven single stream model nozzles were tested in the Anechoic Free-Jet Acoustic Test Facility to evaluate the effectiveness of convergent divergent (C-D) flowpaths in the reduction of shock-cell noise under both static and mulated flight conditions. The test nozzles included a baseline convergent circular nozzle, a C-D circular nozzle, a convergent annular plug nozzle, a C-D annular plug nozzle, a convergent multi-element suppressor plug nozzle, and a C-D multi-element suppressor plug nozzle. Diagnostic flow visualization with a shadowgraph and aerodynamic plume measurements with a laser velocimeter were performed with the test nozzles. A theory of shock-cell noise for annular plug nozzles with shock-cells in the vicinity of the plug was developed. The benefit of these C-D nozzles was observed over a broad range of pressure ratiosin the vicinity of their design conditions. At the C-D design condition, the C-D annual nozzle was found to be free of shock-cells on the plug.

Yamamoto, K.↗
NASA NTRS1978

Fabrication and testing of silver-hydrogen cells

Silver electrodes containing various additives were fabricated and tested in single electrode cells in order to improve the electrochemical utilization of sintered silver cathodes in Ag-H2 aerospace batteries. A standard stack arrangement was used which featured a NASA-developed organic-inorganic separator. All cells were cycled in a regime designed to remove 75% of the cells nominal capacity based on 3.3 gms/AHr Ag utilization. In cases where performance degradation was observed, the main feature mode appeared to be corrosion of either the expanded silver current collector or the connection between the silver electrode and the electrode tab. Promising silver electrodes from single electrode studies were used in the construction of 35 AHr Ag-H2 cells. Two such cells were constructed and installed in heavy walled pressure vessels for testing. Based on the data obtained from all cells tested during the program, four lightweight 35 AHr cells were fabricated. During acceptance testing these cells yielded an average gravimetric energy density of 30 WHr/1b.

Debicarri, D. J.↗
NASA NTRS2001

Different mechanisms of radiation-induced loss of heterozygosity in two human lymphoid cell lines from a single donor

Allelic loss is an important mutational mechanism in human carcinogenesis. Loss of heterozygosity (LOH) at an autosomal locus is one outcome of the repair of DNA double-strand breaks (DSBs) and can occur by deletion or by mitotic recombination. We report that mitotic recombination between homologous chromosomes occurred in human lymphoid cells exposed to densely ionizing radiation. We used cells derived from the same donor that express either normal TP53 (TK6 cells) or homozygous mutant TP53 (WTK1 cells) to assess the influence of TP53 on radiation-induced mutagenesis. Expression of mutant TP53 (Met 237 Ile) was associated with a small increase in mutation frequencies at the hemizygous HPRT (hypoxanthine phosphoribosyl transferase) locus, but the mutation spectra were unaffected at this locus. In contrast, WTK1 cells (mutant TP53) were 30-fold more susceptible than TK6 cells (wild-type TP53) to radiation-induced mutagenesis at the TK1 (thymidine kinase) locus. Gene dosage analysis combined with microsatellite marker analysis showed that the increase in TK1 mutagenesis in WTK1 cells could be attributed, in part, to mitotic recombination. The microsatellite marker analysis over a 64-cM region on chromosome 17q indicated that the recombinational events could initiate at different positions between the TK1 locus and the centromere. Virtually all of the recombinational LOH events extended beyond the TK1 locus to the most telomeric marker. In general, longer LOH tracts were observed in mutants from WTK1 cells than in mutants from TK6 cells. Taken together, the results demonstrate that the incidence of radi-ation-induced mutations is dependent on the genetic background of the cell at risk, on the locus examined, and on the mechanisms for mutation available at the locus of interest.

NASA Discipline Radiation Health↗
NASA NTRS1981

Multijunction high-voltage solar cell

Multijunction cell allows for fabrication of high-voltage solar cell on single semiconductor wafer. Photovoltaic energy source using cell is combined on wafer with circuit it is to power. Cell consists of many voltage-generating regions internally or externally interconnected to give desired voltage and current combination. For computer applications, module is built on silicon wafer with energy for internal information processing and readouts derived from external light source.

Evans, J. C., Jr.↗
NASA NTRS1997

Activation and proliferation of lymphocytes and other mammalian cells in microgravity

The experimental findings reviewed in this chapter support the following conclusions: Proliferation. Human T-lymphocytes, associated with monocytes as accessory cells, show dramatic changes in the centrifuge, in the clinostat and in space. In free-floating cells the mitogenic response is depressed by 90% in microgravity, whereas in cells attached to a substratum activation is enhanced by 100% compared to 1-G ground and inflight controls. The duration of phase G1 of the mitotic cycle of HeLa cells is reduced in hypergravity, resulting in an increased proliferation rate. Other systems like Friend cells and WI38 human embryonic lung cells do not show significant changes. Genetic expression and signal transduction. T-lymphocytes and monocytes show important changes in the expression of cytokines like interleukin-1, interleukin-2, interferon-gamma and tumor necrosis factor. The data from space experiments in Spacelab, Space Shuttle mid-deck, and Biokosmos have helped to clarify certain aspects of the mechanism of T-cell activation. Epidermoid A431 cells show changes in the genetic expression of the proto-oncogenes c-fos and c-jun in the clinostat and in sounding rockets. Membrane function, in particular the binding of ligates as first messengers of a signal, is not changed in most of the cell systems in microgravity. Morphology and Mortility. Free cells, lymphocytes in particular, are able to move and form aggregates in microgravity, indicating that cell-cell contacts and cell communications do take place in microgravity. Dramatic morphological and ultrastructural changes are not detected in cells cultured in microgravity. Important experiments with single mammalian cells, including immune cells, were carried out recently in three Spacelab flights, (SL-J, D-2, and IML-2 in 1992, 1993, and 1994, respectively). The results of the D-2 mission have been published in ref. 75; those of the IML-2 mission in ref. 76. Finally, many cell biology experiments in space have suffered in the past from a lack of adequate controls (like 1-G centrifuges) and of proper experimental conditions (like well-controlled temperature). In this respect the availability of Biorack, outfitted with proper incubators with 1-G control centrifuge as well as a glovebox with a microscope, is a great advantage. It is also desirable that cell biology experiments in space are accompanied or even preceded by a program of ground-based investigations in the fast rotating clinostat and in the centrifuge, and that preparatory experiments be done in parabolic flights and sounding rockets, whenever possible. Proper publication of the results of space experiments is another important need. A great number of data have been published in proceedings and reports that are not available to the broad scientific community. To guarantee the credibility and the international recognition of space biology it is important that the results be published in international, peer reviewed journals.

manned↗
NASA NTRS2000

Chromosomal instability induced by heavy ion irradiation

PURPOSE: To establish the dose-response relationship for the induction of chromosomal instability in GM10115 cells exposed to high-energy iron ions (1 GeV/nucleon, mean LET 146 keV/microm) and gold ions (11 GeV/nucleon, mean LET 1450 keV/microm). Past work has established that sparsely ionizing X-rays can induce a long-lived destabilization of chromosomes in a dose-dependent manner at an incidence of approximately 3% per gray. The present investigation assesses the capacity of High-Z and High-energy (HZE) particles to elicit this same endpoint. MATERIALS AND METHODS: Clonal populations derived from single progenitor cells surviving heavy-ion irradiation were analyzed cytogenetically to identify those clones showing a persistent destablization of chromosomes. RESULTS: Dose-response data, with a particular emphasis at low dose (< 1.0 Gy), indicate a frequency of approximately 4% per gray for the induction of chromosomal instability in clones derived from single progenitor cells surviving exposure to iron ions. The induction of chromosomal instability by gold ions was, however, less responsive to applied dose, as the observed incidence of this phenotype varied from 0 to 10% over 1-8 Gy. Both iron and gold ions gave dose-dependent increases in the yield of chromosomal aberrations (both chromosome- and chromatid-type) measured at the first mitosis following irradiation, as well as shoulderless survival curves having D0=0.87 and 1.1 Gy respectively. CONCLUSIONS: Based on the present dose-response data, the relative biological effectiveness of iron ions is 1.3 for the induction of chromosomal instability, and this indicates that heavy ions are only slightly more efficient than X-rays at eliciting this delayed phenotype.

Non-NASA Center↗