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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 505 records · Page 28
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NASA NTRS2016

Results of the Alternative Water Processor Test, A Novel Technology for Exploration Wastewater Remediation

Biologically-based water recovery systems are a regenerative, low energy alternative to physiochemical processes to reclaim water from wastewater. This report summarizes the results of the Alternative Water Processor (AWP) Integrated Test, conducted from June 2013 until April 2014. The system was comprised of four (4) membrane aerated bioreactors (MABRs) to remove carbon and nitrogen from an exploration mission wastewater and a coupled forward and reverse osmosis system to remove large organic and inorganic salts from the biological system effluent. The system exceeded the overall objectives of the test by recovering 90% of the influent wastewater processed into a near potable state and a 64% reduction of consumables from the current state of the art water recovery system on the International Space Station (ISS). However, the biological system fell short of its test goals, failing to remove 75% and 90% of the influent ammonium and organic carbon, respectively. Despite not meeting its test goals, the BWP demonstrated the feasibility of an attached-growth biological system for simultaneous nitrification and denitrification, an innovative, volume- and consumable-saving design that does not require toxic pretreatment.

Meyer, Caitlin E.↗
NASA NTRS1983

The structure of the heliospheric current sheet - 1978-1982

Continuing the study near solar minimum in 1976-1977 (Hoeksema et al., 1982), the configuration of the heliospheric magnetic field for the period 1976-1982 is calculated using a potential field model. Particular attention is given to the structure during the rising phase, maximum, and early decline of sunspot cycle 21, from 1978 to 1982. Four warps in the current sheet (the boundary between interplanetary magnetic field toward and away from the sun) are seen early in this interval; these give rise to a four-sector structure in the interplanetary magnetic field observed at earth. It is noted that the location of the current sheet changes slowly and extends to a heliographic latitude of approximately 50 deg. The strength of the polar field correction throughout this period is determined and included in the model calculations. The lower latitude magnetic fields become much stronger as the polar fields weaken and reverse polarity near maximum, decreasing the effect of the polar field correction.

Hoeksema, J. T.↗
NASA NTRS1989

Room-temperature InGaAs detector arrays for 2.5 microns

This paper describes new alloy heterojunction detectors of In(.8)Ga(.2)As/InAs(.6)P(.4) which can detect light between 1.7 and 2.6 microns with 50 percent quantum efficiency and 5 mA/sq cm dark current (-1 V) density at room temperature. Wafer probe data showed that over 50 good contiguous 100 micron diameter devices (spaced 400 microns) could be made on a 25 x 30 mm wafer with overall yield above 93 percent. The ability to operate under -1 V reverse bias makes these devices ideally compatible with existing commercial multiplexer readouts.

Olsen, G. H.↗
NASA NTRS1976

Properties of spikelike shear flow reversals observed in the auroral plasma by Atmosphere Explorer C

A study of the characteristics of pairs of oppositely directed spikes in ionospheric convection velocities (or shear flow reversals), as first described by Gurnett, has been conducted by using data from Atmosphere Explorer C. These phenomena tend to occur near the large-scale reversal from sunward to antisunward convection on the nightside of the earth. Generally, the spikelike shear flow reversals involve electric field components along the spacecraft orbit that are directed toward the region between them, in which inverted V type electron precipitation is observed. This relationship between the electron precipitation and the electric field spikes is consistent with an upward-flowing field-aligned current that is fed by Pedersen currents from the adjacent regions of strong convection. In one case a divergent equivalent electric field structure was observed, that is, with the spikelike electric fields pointing away from the region in between, which in this case exhibited a sharp electron flux dropout. This opposite configuration may be an example of counterparts to inverted V structures existing in regions of downward-flowing field-aligned currents.

Burch, J. L.↗
NASA NTRS1995

Numerical simulation of corotating interaction regions

We report on a numerical simulation of Corotating Interaction Regions (CIRs) in the solar wind. We employ an MHD calculation with a tilted dipole model: slow wind is assumed around the tilted current sheet. As a simplifying assumption the solar wind is kept radial, meridional and azimuthal deflections are neglected. Despite of this simplification the model reproduces several observed features of CIR-s. CIR-s turn out most prominent at mid-latitudes. Toward increasing heliographic latitudes, reverse shocks become dominant, forward shocks tend to become weaker then disappear. The frozen in magnetic field is calculated and applied for the simulation of the transport of cosmic rays in the heliosphere. Some consequences on recurrent cosmic ray phenomena and on the acceleration of energetic particles will be discussed.

Kota, J.↗
NASA NTRS1999

The Mars Environmental Compatibility Assessment (MECA) Wet Chemistry Experiment on the Mars 2001 Lander

The Mars Environmental Compatibility Assessment (MECA) is an instrument suite that will fly on the Mars Surveyor 2001 Lander Spacecraft. MECA is sponsored by the Human Exploration and Development of Space (HEDS) program and will evaluate potential hazards that the dust and soil of Mars might present to astronauts and their equipment on a future human mission to Mars. Four elements constitute the integrated MECA payload: a microscopy station, patch plates, an electrometer, and the wet chemistry laboratory (WCL). The WCL consists of four identical cells, each of which will evaluate a sample of Martian soil in water to determine conductivity, pH, redox potential, dissolved C02 and 02 levels, and concentrations of many soluble ions including sodium, potassium, magnesium, calcium and the halides. In addition, cyclic voltammetry will be used to evaluate reversible and irreversible oxidants present in the water/soil solution. Anodic stripping voltammetry will be used to measure concentrations of trace metals including lead, copper, and cadmium at ppb levels. Voltammetry is a general electrochemical technique that involves controlling the potential of an electrode while simultaneously measuring the current flowing at that electrode. The WCL experiments will provide information on the corrosivity and reactivity of the Martian soil, as well as on soluble components of the soil which might be toxic to human explorers. They will also guide HEDS scientists in the development of high fidelity Martian soil simulants. In the process of acquiring information relevant to HEDS, the WCL will assess the chemical composition and properties of the salts present in the Martian soil.

Grannan, S. M.↗
NASA NTRS1985

Hot-spot heating susceptibility due to reverse bias operating conditions

Because of field experience (indicating that cell and module degradation could occur as a result of hot spot heating), a laboratory test was developed at JPL to determine hot spot susceptibility of modules. The initial hot spot testing work at JPL formed a foundation for the test development. Test parameters are selected as follows. For high shunt resistance cells, the applied back bias test current is set equal to the test cell current at maximum power. For low shunt resistance cells, the test current is set equal to the cell short circuit current. The shadow level is selected to conform to that which would lead to maximum back bias voltage under the appropriate test current level. The test voltage is determined by the bypass diode frequency. The test conditions are meant to simulate the thermal boundary conditions for 100 mW/sq cm, 40C ambient environment. The test lasts 100 hours. A key assumption made during the development of the test is that no current imbalance results from the connecting of multiparallel cell strings. Therefore, the test as originally developed was applicable for single string case only.

Gonzalez, C. C.↗
NASA NTRS1987

Determination of lifetime and surface recombination velocity of p-n junction solar cells and diodes by observing transients

The unified view of transient methods for the determination of recombination lifetime tau and back surface recombination velocity S presented here for silicon solar cells and diodes attempts to define limitations of existing methods and to evolve improvements. The presence of sizable junction capacitance for silicon devices under forward voltage invalidates the use of conventional open-circuit voltage decay (OCVD) and reverse recovery. This led Green (1983) to his method of compensated open-circuit voltage decay, in which the addition of an external resistor shunting the solar cell partially corrects for the presence of the junction capacitance. Setting this resistance to zero produces an electrical short-circuit current-decay method, which has the advantage of enabling determination of both tau and S. In an alternate approach, one may insert the functional dependence of the junction capacitance on forward voltage. This new method, denoted by the acronym OCVDCAP, enables the determination of tau with apparently greater accuracy than that obtained by previous methods utilizing voltage transients. But OCVDCAP has in common with the previous methods that it determines tau only and has practical utility only for determining tau of long-base devices. This means that it is useful only for thick base regions. In principle, however, it has an advantage over short-circuit current decay: it requires only pressure contacts, not ohmic contacts, and therefore may be used to determine tau after key processing steps in manufacturing.

Lindholm, Fredrik A.↗
NASA NTRS1987

Development of 8 cm x 8 cm silicon gridded back solar cell for space station

The 8-cm x 8-cm gridded back cell being developed for the space station photovoltaic array is described. Modeling studies show that the beginning of life power output of 1.039 W per cell may be met by several different configurations, the most promising being either a fielded or nonfielded 2 ohm-cm planar 8-mil cell. Experimental data are presented which show that a thermal alpha of 0.63 is achievable on a planar cell but at the expense of some Isc. Planar cells are found to possess short-circuit currents which are 9 percent lower than on textured cells due to the loss of near-IR radiation by transmission through the cell. Preliminary modeling shows that the efficiency of the textured cell exceeds the planar cell by approximately 9 percent at 25 C but the situation is reversed in orbit due to the high thermal alpha of textured cells (0.82). Experimental data show that the IR absorption in textured cells can be reduced by about 3 alpha points without loss of efficiency by controlling the doping concentration in the diffused layers, thus increasing the efficiency in orbit.

Lillington, D. R.↗
NASA NTRS1990

The electrochemical generation of useful chemical species from lunar materials

Electrochemical cells have been fabricated for the simultaneous generation of oxygen and lithium from a Li2O-containing molten salt (Li2O-LiCl-LiF). The cell utilizes an oxygen vacancy conducting solid electrolyte, yttria-stabilized zirconia (YSZ), to effect separation between oxygen evolving and lithium reduction half-cell reactions. The cell, which operates at 700-850 C, possesses rapid electrode kinetics at the lithium-alloy electrode with exchange current density values being greater than 60 mA/sq cm. When used in the electrolytic mode, lithium produced at the negative electrode would be continuously removed from the cell for later use (under lunar conditions) as an easily storable reducing agent for the chemical refining of lunar ores. Because of the high reversibility of this electrochemical system, it has also formed the basis for the lithium-oxygen secondary battery system which possesses the highest theoretical energy density yet investigated.

Tsai, Kan J.↗
NASA NTRSDate not supplied

Learning From Failure: Boosting Cycling Endurance of Optical Phase Change Materials

Chalcogenide phase change materials (PCMs) are a unique class of compounds whose switchable optical and electronic properties have fueled an explosion of emerging applications in microelectronics and microphotonics. Key to any application is the ability of PCMs to reliably switch between crystalline and amorphous states over a large number of cycles. While this issue has been extensively studied in the case of microelectronic memories, current PCM-based optical devices suffer from much inferior endurance. To understand the failure mechanisms limiting endurance of PCMs specifically in microphotonic devices, we have developed an on-chip resistive micro-heater platform and an automatic multi-modal characterization system to analyze cycling performance of optical PCMs. Reversible switching of large-area PCM devices over 50,000 cycles was demonstrated.

Optical phase change material↗
NASA NTRS2012

Reversible Ammonia Sorption for the Primary Life Support System (PLSS)

Results are presented on the development of regenerable trace-contaminant (TC) sorbent for use in Extravehicular Activities (EVAs), and more specifically in the Primary Life Support System (PLSS). Since ammonia is the most important TC to be captured, data presented in this paper are limited to ammonia sorption, with results relevant to other TCs to be reported at a later time. The currently available TC-control technology involves the use of a packed bed of acid-impregnated granular charcoal. The sorbent is non-regenerable, and its use is associated with appreciable pressure drop, i.e. power consumption. The objective of this work is to demonstrate the feasibility of using vacuum-regenerable sorbents for PLSS application. In this study, several carbon sorbent monoliths were fabricated and tested. Multiple adsorption/vacuum-regeneration cycles were demonstrated at room temperature, as well as carbon surface conditioning that enhances ammonia sorption without impairing sorbent regeneration. Depending on sorbent monolith geometry, the reduction in pressure drop with respect to granular sorbent was found to be between 50% and two orders of magnitude. Resistive heating of the carbon sorbent monolith was demonstrated by applying voltage to the opposite ends of the monolith.

Wojtowicz, Marek A.↗
NASA NTRS1979

Spacecraft automated operations

Trends in automation of planetary spacecraft are examined using data from missions as far back as Mariner '67 and up to the highly sophisticated Galileo. Nine design considerations which influence the degree of automation such as protection against catastrophic failures, highly repetitive functions, loss of spacecraft communications, and the need for near-real-time adaptivity are discussed. Rapid growth of automation is shown in terms of on-board hardware by plots of number of processors on board, the average speed of processors, and total core memory. The number of commands transmitted from the ground has grown to 5 million bits in Voyager, so that increases in mission complexity have increased both in spacecraft automation and ground operations. Achieving greater automation by transferring ground operations to the spacecraft with the current means of controlling missions, are considered noting proposed changes. For the future, improved computer technology, more microprocessors and increased core storage will be used, and the number of automated functions and their complexity will grow. It is concluded that using the growing computational capability of spacecraft will achieve more autonomy thus reversing the trend of increased mission complexity and cost.

Bird, T. H.↗
NASA NTRS1982

Fast recovery, high voltage silicon diodes for AC motor controllers

The fabrication and characterization of a high voltage, high current, fast recovery silicon diode for use in AC motor controllers, originally developed for NASA for use in avionics power supplies, is presented. The diode utilizes a positive bevel PIN mesa structure with glass passivation and has the following characteristics: peak inverse voltage - 1200 volts, forward voltage at 50 amperes - 1.5 volts, reverse recovery time of 200 nanoseconds. Characterization data for the diode, included in a table, show agreement with design concepts developed for power diodes. Circuit diagrams of the diode are also given.

Balodis, V.↗
NASA NTRS1994

Auroral activity associated with Kelvin-Helmholtz instability at the inner edge of the low-latitude boundary layer

Auroral activity occurred in the late afternoon sector (approx. 16 MLT) in the northern hemisphere during the passage at Earth of an interplanetary magnetic cloud on January 14, 1988. The auroral activity consisted of a very dynamic display which was preceded and followed by quiet auroral displays. During the quiet displays, discrete rayed arcs aligned along the geomagnetic L shells were observed. In the active stage, rapidly evolving spiral forms centered on magnetic zenith were evident. The activity persisted for many minutes and was characterized by the absence of directed motion. They were strongly suggestive of intense filaments of upward field-aligned currents embedded in the large-scale region 1 current system. Distortions of the flux ropes as they connect from the equatorial magnetosphere to the ionosphere were witnessed. We assess as possible generating mechanisms three nonlocal sources known to be associated with field-aligned currents. Of these, partial compressions of the magnetosphere due to variations of solar wind dynamic pressure seem an unlikely source. The possibility that the auroral forms are due to reconnection is investigated but is excluded because the active aurora were observed on the closed field line region just equatorward of the convection reversal boundary. To support this conclusion further, we apply recent results on the mapping of ionospheric regions to the equatorial plane based on the Tsyganenko 1989 model (Kaufmann et al., 1993). We find that for comparable magnetic activity the aurora map to the equatorial plane at X(sub GSM) = approx. 3 R(sub E) and approx. 2 R(sub E) inward of the magnetopause, that is, the inner edge of the boundary layer close to dusk. Since the auroral forms are manifestly associated with magnetic field shear, a vortical motion at the equatorial end of the flux rope is indicated, making the Kelvin-Helmholtz instability acting at the inner edge of the low-latitude boundary layer the most probable generating source.

Farrugia, C. J.↗
NASA NTRS2006

Unsteady Flow Simulation of High-speed Turbopumps

Computation of high-speed hydrodynamics requires high-fidelity simulation to resolve flow features involving transient flow, cavitation, tip vortex and multiple scales of unsteady fluctuations. One example of this type in aerospace is related to liquid-fueled rocket turbopump. Rocket turbopumps operate under severe conditions at very high rotational speeds typically at thousands of rpm. For example, the Shuttle orbiter low-pressure-fuel-turbopump creates transient flow features associated with reverse flows, tip clearance effects, secondary flows, vortex shedding, junction flows, and cavitation effects. Flow unsteadiness originating from the orbiter Low-Pressure-Fuel-Turbopump (LPFTP) inducer is one of the major contributors to the high frequency cyclic loading that results in high cycle fatigue damage to the flow liners just upstream of the LPFTP. The reverse flow generated at the tip of the inducer blades travels upstream and interacts with the bellows cavity. Simulation procedure for this type high-speed hydrodynamic problems requires a method for quantifying multi-scale and multi-phase flow as well as an efficient high-end computing strategy. The current paper presents a high-fidelity computational procedure for unsteady hydrodynamic problems using a high-speed liquid-fueled rocket turbopump.

Kiris, Cetin C.↗
NASA NTRS2010

Ablative Rocket Deflector Testing and Computational Modeling

A deflector risk mitigation program was recently conducted at the NASA Stennis Space Center. The primary objective was to develop a database that characterizes the behavior of industry-grade refractory materials subjected to rocket plume impingement conditions commonly experienced on static test stands. The program consisted of short and long duration engine tests where the supersonic exhaust flow from the engine impinged on an ablative panel. Quasi time-dependent erosion depths and patterns generated by the plume impingement were recorded for a variety of different ablative materials. The erosion behavior was found to be highly dependent on the material s composition and corresponding thermal properties. For example, in the case of the HP CAST 93Z ablative material, the erosion rate actually decreased under continued thermal heating conditions due to the formation of a low thermal conductivity "crystallization" layer. The "crystallization" layer produced near the surface of the material provided an effective insulation from the hot rocket exhaust plume. To gain further insight into the complex interaction of the plume with the ablative deflector, computational fluid dynamic modeling was performed in parallel to the ablative panel testing. The results from the current study demonstrated that locally high heating occurred due to shock reflections. These localized regions of shock-induced heat flux resulted in non-uniform erosion of the ablative panels. In turn, it was observed that the non-uniform erosion exacerbated the localized shock heating causing eventual plume separation and reversed flow for long duration tests under certain conditions. Overall, the flow simulations compared very well with the available experimental data obtained during this project.

Allgood, Daniel C.↗
NASA NTRS1982

Reverse draping of magnetic field lines in the boundary layer

An unexpected orientation of field lines has been found by ISEE satellite measurements of the earth magnetosphere boundary layer, perhaps indicating a reverse draping. Three-dimensional plasma flow measurements by ISEE 1 and 2 show the tailward flow in the boundary layer to have an equatorward component which suggests high-latitude plasma entry. Simultaneous magnetic field measurements with the two satellites during a boundary crossing sequence yielded data on the boundary layer electric currents and the boundary layer interface with plasma sheet and magnetosheath. The currents are found to be largely field-aligned, with intensities in the 0.03-0.06 microampere/sq m range.

Hones, E. W., Jr.↗