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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Effects of Electrons, Protons, and Ultraviolet Radiation on Thermophysical Properties of Polymeric Films

The response of coated thin polymer films to ultraviolet (UV), electron and proton radiation simultaneously has been evaluated, with selected measurements in situ. Exposure was intended to simulate the electron and proton radiation environment near the Earth-Sun Lagrangian points (LI and L2) for five years and approximately 1000 equivalent solar hours (ESH) UV. These orbital environments are relevant to several potential missions such as the Next Generation Space Telescope and Geomagnetic Storm Warning, both of which may use thin film based structures for a sunshade and solar sail, respectively. The thin film candidates (12.5 micrometers thick) consisted of commercially available materials (Kapton(R) E, HN, Upilex(R) S, CP-1, CP-2, TOR-RC, and TOR-LMBP) that were metalized on one side with vapor deposited aluminum. All of the films are aromatic polyimides, with the exception of TORLMBP, which is a copoly(arylene ether benzimidazole). The films were exposed as second surface mirrors and the effects of the exposure on solar absorptance, thermal emittance, and tensile properties were determined. The in situ changes in solar absorptance from Kapton(R) and Upilex(R) were less than 0. 1, whereas the solar absorptance of TOR and CP films increased by more than 0.3 without saturating. The thermal emittance measurements also showed that the Kapton(R) and Upilex(R) materials increased only 1-2%, but the remaining materials increased 5-8%. Based on tensile property measurements made in air following the test, the failure stress of every type of polymer film decreased as a result of irradiation. The polymers most stable in reflectance, namely Upilex(R) and Kapton(R), were also the strongest in tension before irradiation, and they retained the greatest percentage of tensile strength. The films less stable in reflectance were also weaker in tension, and lost more tensile strength as a result of irradiation. The apparent failure strain (as a percent of original gage length) of every type of polymer film except TOR-RC, decreased as a result of irradiation.

Russell, Dennis A.↗
NASA NTRS2001

Effects of Flame Structure and Hydrodynamics on Soot Particle Inception and Flame Extinction in Diffusion Flames

This paper summarizes recent studies of the effects of stoichiometric mixture fraction (structure) and hydrodynamics on soot particle inception and flame extinction in diffusion flames. Microgravity experiments are uniquely suited for these studies because, unlike normal gravity experiments, they allow structural and hydrodynamic effects to be independently studied. As part of this recent flight definition program, microgravity studies have been performed in the 2.2 second drop tower. Normal gravity counterflow studies also have been employed and analytical and numerical models have been developed. A goal of this program is to develop sufficient understanding of the effects of flame structure that flames can be "designed" to specifications - consequently, the program name Flame Design. In other words, if a soot-free, strong, low temperature flame is required, can one produce such a flame by designing its structure? Certainly, as in any design, there will be constraints imposed by the properties of the available "materials." For hydrocarbon combustion, the base materials are fuel and air. Additives could be considered, but for this work only fuel, oxygen and nitrogen are considered. Also, the structure of these flames is "designed" by varying the stoichiometric mixture fraction. Following this line of reasoning, the studies described are aimed at developing the understanding of flame structure that is needed to allow for optimum design.

Axelbaum, R. L.↗
NASA NTRS2002

Laboratory Studies of the Optical Properties and Condensation Processes of Cosmic Dust Particles

A laboratory facility for levitating single isolated dust particles in an electrodynamics balance has been developing at NASA/Marshall Space Flight Center for conducting a variety of experimental, of astrophysical interest. The objective of this research is to employ this innovative experimental technique for studies of the physical and optical properties of the analogs of cosmic grains of 0.2-10 micron size in a chamber with controlled pressure/temperatures simulating astrophysical environments. In particular, we will carry out three classes of experiments to investigate the microphysics of the analogs of interstellar and interplanetary dust grains. (1) Charge characteristics of micron size single dust grains to determine the photoelectric efficiencies, yields, and equilibrium potentials when exposed to UV radiation. These measurements will provide the much-needed photoelectric emission data relating to individual particles as opposed to that for the bulk materials available so far. (2) Infrared optical properties of dust particles obtained by irradiating the particles with radiation from tunable infrared diode lasers and measuring the scattered radiation. Specifically, the complex refractive indices, the extinction coefficients, the scattering phase functions, and the polarization properties of single dust grains of interest in interstellar environments, in the 1-25 micron spectral region will be determined. (3) Condensation experiments to investigate the deposition of volatile gases on colder nucleated particles in dense interstellar clouds and lower planetary atmospheres. The increase in the mass or m/q ratio due to condensation on the particle will be monitored as a function of the dust particle temperature and the partial pressure of the injected volatile gas. The measured data wild permit determination of the sticking efficiencies of volatile gases of astrophysical interest. Preliminary results based on photoelectric emission experiments on 0.2-6.6 micron size silica particles exposed to UV radiation in the 120-200 nm spectral region will be presented.

Abbas, Mian M.↗
NASA NTRS1998

Thin Film...Large Payoff

SRS Technologies is currently the only company licensed by Langley Research Center to produce colorless polyimides. They currently produce two polyimides, the LaRC-CP1 and LaRC-CP2 developed by Langley Research Center. These polyimides offer many advantages over other commercially available materials including excellent thermal stability, radiation resistance, solubility, and transparency. The SRS polyimides can be used in laminates, films, molded parts, and stock shapes. The polyimide technology has also helped the company further their development of solar arrays.

Source record↗
NASA NTRS2003

Magnetohydrodynamic Augmented Propulsion Experiment: I. Performance Analysis and Design

The performance of conventional thermal propulsion systems is fundamentally constrained by the specific energy limitations associated with chemical fuels and the thermal limits of available materials. Electromagnetic thrust augmentation represents one intriguing possibility for improving the fuel composition of thermal propulsion systems, thereby increasing overall specific energy characteristics; however, realization of such a system requires an extremely high-energy-density electrical power source as well as an efficient plasma acceleration device. This Technical Publication describes the development of an experimental research facility for investigating the use of cross-field magnetohydrodynamic (MHD) accelerators as a possible thrust augmentation device for thermal propulsion systems. In this experiment,a 1.5-MW(sub e) Aerotherm arc heater is used to drive a 2-MW(sub e) MHD accelerator. The heatsink MHD accelerator is configured as an externally diagonalized, segmented channel, which is inserted into a large-bore, 2-T electromagnet. The performance analysis and engineering design of the flow path are described as well as the parameter measurements and flow diagnostics planned for the initial series of test runs.

Litchford, R. J.↗
NASA NTRS2002

Synchrotron FTIR Examination of Interplanetary Dust Particles: An Effort to Determine the Compounds and Minerals in Interstellar and Circumstellar Dust

Some interplanetary dust particles (IDPs), collected by NASA from the Earth's stratosphere, are the most primitive extraterrestrial material available for laboratory analysis. Many exhibit isotopic anomalies in H, N, and O, suggesting they contain preserved interstellar matter. We report the preliminary results of a comparison of the infrared absorption spectra of subunits of the IDPs with astronomical spectra of interstellar grains.

Flynn, G. J.↗
NASA NTRS2003

Standards Advisor-Advanced Information Technology for Advanced Information Delivery

Developers of space systems must deal with an increasing amount of information in responding to extensive requirements and standards from numerous sources. Accessing these requirements and standards, understanding them, comparing them, negotiating them and responding to them is often an overwhelming task. There are resources to aid the space systems developer, such as lessons learned and best practices. Again, though, accessing, understanding, and using this information is often more difficult than helpful. This results in space systems that: 1. Do not meet all their requirements. 2. Do not incorporate prior engineering experience. 3. Cost more to develop. 4. Take longer to develop. The NASA Technical Standards Program (NTSP) web site at http://standards.nasa.gov has made significant improvements in making standards, lessons learned, and related material available to space systems developers agency-wide. The Standards Advisor was conceived to take the next steps beyond the current product, continuing to apply evolving information technology that continues to improve information delivery to space systems developers. This report describes the features of the Standards Advisor and suggests a technical approach to its development.

Hawker, J. Scott↗
NASA NTRS1961

A Preliminary Study of V/STOL Transport Aircraft and Bibliography of NASA Research in the VTOL-STOL Field

This group of papers was prepared by the staff of the Langley Research Center to assist in planning for future commercial air-transport facilities in the New York metropolitan area. Areas of particular interest were predictions regarding the types of V/STOL aircraft that are likely to be developed for various commercial transport applications, estimates of the performance and probable operating procedures for such aircraft, and the approximate dates these aircraft could be available for use. Although the NASA has made no comprehensive studies of this type, the extensive research program in the VTOL-STOL field during the last 10 years appeared to provide a source for some of the desired information . The five papers included herein were therefore prepared to summarize pertinent available material in a form suitable for the intended use. In several instances, new studies and analysis were required to provide the necessary information, but because of a time deadline, many of the significant points received only a cursory examination. For example, much of the quantitative data used in the papers for making generalized comparisons was obtained by approximate methods and is not considered appropriate for use in applications where precise estimates are required. It should be recognized, then, that the treatment of the V/STOL transport provided by this group of papers is necessarily of a preliminary nature.

Source record↗
NASA NTRS2003

Dye-Sensitized Solar Cells for Space Power

During the course of this grant, dye-sensitized solar cells were prepared and characterized. The solar cells were prepared using materials (dyes, electrolytes, transparent conductive oxide coated glass, nanocrystalline TiO2) entirely prepared in-house, as well as prepared using materials available commercially. Complete cells were characterized under simulated AM0 illumination. The best cell prepared at NASA had an AM0 efficiency of 1.22% for a 1.1 sq cm cell. Short circuit current (Isc), open circuit voltage (Voc) and fill factor (FF) for the cell were 6.95 mA, 618 mV and 42.8%, respectively. For comparison purposes, two commercially prepared dye-sensitized solar cells were obtained from Solaronix SA, Aubonne, Switzerland. The Solaronix cells were also characterized under simulated AM0 illumination. The best cell from Solaronix had an active area of 3.71 sq cm and measured an AM0 efficiency of 3.16%. with Isc, Voc and FF of 45.80 mA, 669.6 mV and 52.3%, respectively. Both cells from Solaronix were rapid thermal cycled between -80 C and 80 C. Thermal cycling led to a 4.6% loss of efficiency in one of the cells and led to nearly a complete failure in the second cell.

Harris, Jerry D.↗
NASA NTRS2004

Representation of the Geosynchronous Plasma Environment for Spacecraft Charging Calculations

Historically, our ability to predict and postdict surface charging has suffered from both a lack of reliable secondary emission and backscattered electron yields and poor characterization of the plasma environment. One difficulty lies in the common practice of fitting the plasma data to a Maxwellian or Double Maxwellian distribution function, which may not represent the data well for charging purposes. For 13 years Los Alamos National Laboratory (LANL) has been accumulating measurements of electron and proton spectra from Magnetospheric Plasma Analyzer (MPA) instruments aboard a series of geosynchronous satellites. These data provide both a plasma characterization and the potential of the instrument ground. We use electron and ion flux spectra measured by the LANL MPA to examine how the use of different spectral representations of the charged particle environment in computations of spacecraft potentials during magnetospheric substorms affects the accuracy of the results. We calculate the spacecraft potential using both the measured fluxes and several different fits to these fluxes. These flux measurements and fits have been corrected for the difference between the measured and calculated potential. The potentials computed using the measured fluxes, the best available material properties of graphite carbon, and a secondary electron escape fraction of 81%, are within a factor of three of the measured potential for nearly all the data. Using a Kappa fit to the electron distribution function and a Maxwellian fit to the ion distribution function gives agreement similar to the calculations using the actual data. Alternative spectral representations, including Maxwellian and double Maxwellian for both species, lead to less satisfactory agreement between predicted and measured potentials.

Davis, V. A.↗
NASA NTRS2005

Large Engine Technology Program. Task 21: Rich Burn Liner for Near Term Experimental Evaluations

The objective of the task reported herein, which was conducted as part of the NASA sponsored Large Engine Technology program, was to define and evaluate a near-term rich-zone liner construction based on currently available materials and fabrication processes for a Rich-Quench-Lean combustor. This liner must be capable of operation at the temperatures and pressures of simulated HSCT flight conditions but only needs sufficient durability for limited duration testing in combustor rigs and demonstrator engines in the near future. This must be achieved at realistic cooling airflow rates since the approach must not compromise the emissions, performance, and operability of the test combustors, relative to the product engine goals. The effort was initiated with an analytical screening of three different liner construction concepts. These included a full cylinder metallic liner and one with multiple segments of monolithic ceramic, both of which incorporated convective cooling on the external surface using combustor airflow that bypassed the rich zone. The third approach was a metallic platelet construction with internal convective cooling. These three metal liner/jacket combinations were tested in a modified version of an existing Rich-Quench-Lean combustor rig to obtain data for heat transfer model refinement and durability verification.

Hautman, D. J.↗
NASA NTRS2004

The Nature and Origin of Interplanetary Dust: High Temperature Components

The specific parent bodies of individual interplanetary dust particles (IDPs) are un-known, but the anhydrous chondritic-porous (CP) sub-set has been linked directly to cometary sources [1]. The CP IDPs escaped the thermal processing and water-rock interactions that have severely modified or destroyed the original mineralogy of primitive meteorites. Their origin in the outer regions of the solar system suggests they should retain primitive chemical and physical characteristics from the earliest stages of solar system formation (including abundant presolar materials). Indeed, CP IDPs are the most primitive extraterrestrial materials available for laboratory studies based on their unequilibrated mineralogy [2], high concentrations of carbon, nitrogen and volatile trace elements relative to CI chondrites [3, 4, 5], presolar hydrogen and nitrogen isotopic signatures [6, 7] and abundant presolar silicates [8].

Keller, L. P.↗
NASA NTRS2005

Effects of Control Mode and R-Ratio on the Fatigue Behavior of a Metal Matrix Composite

Composite Because of their high specific stiffness and strength at elevated temperatures, continuously reinforced metal matrix composites (MMC's) are under consideration for a future generation of aeropropulsion systems. Since components in aeropropulsion systems experience substantial cyclic thermal and mechanical loads, the fatigue behavior of MMC's is of great interest. Almost without exception, previous investigations of the fatigue behavior of MMC's have been conducted in a tension-tension, load-controlled mode. This has been due to the fact that available material is typically less than 2.5-mm thick and, therefore, unable to withstand high compressive loads without buckling. Since one possible use of MMC's is in aircraft skins, this type of testing mode may be appropriate. However, unlike aircraft skins, most engine components are thick. In addition, the transient thermal gradients experienced in an aircraft engine will impose tension-compression loading on engine components, requiring designers to understand how the MMC will behave under fully reversed loading conditions. The increased thickness of the MMC may also affect the fatigue life. Traditionally, low-cycle fatigue (LCF) tests on MMC's have been performed in load control. For monolithic alloys, low-cycle fatigue tests are more typically performed in strain control. Two reasons justify this choice: (1) the critical volume from which cracks initiate and grow is generally small and elastically constrained by the larger surrounding volume of material, and (2) load-controlled, low-cycle fatigue tests of monolithics invariably lead to unconstrained ratcheting and localized necking--an undesired material response because the failure mechanism is far more severe than, and unrelated to, the fatigue mechanism being studied. It is unknown if this is the proper approach to composite testing. However, there is a lack of strain-controlled data on which to base any decisions. Consequently, this study addresses the isothermal, LCF behavior of a [0]_32 MMC tested under strain- and load-controlled conditions for both zero-tension and tension-compression loading conditions. These tests were run at 427 C on thick specimens of SiC-reinforced Ti-15-3. For the fully-reversed tests, no difference was observed in the lives between the load- and strain-controlled tests. However, for the zero-tension tests, the strain-controlled tests had longer lives by a factor of 3 in comparison to the load-controlled tests. This was due to the fact that under strain-control the specimens cyclically softened, reducing the cracking potential. In contrast, the load-controlled tests ratcheted toward larger tensile strains leading to an eventual overload of the fibers. Fatigue tests revealed that specimens tested under fully-reversed conditions had lives approximately an order of magnitude longer than for those specimens tested under zero tension. When examined on a strain-range basis, the fully reversed specimens had similar, but still shorter lives than those of the unreinforced matrix material. However, the composite had a strain limitation at short lives because of the limited strain capacity of the brittle ceramic fiber. The composite also suffered at very high lives because of the lack of an apparent fatigue limit in comparison to the unreinforced matrix. The value of adding fibers to the matrix is apparent when the fatigue lives are plotted as a function of stress range. Here, the composite is far superior to the unreinforced matrix because of the additional load-carrying capacity of the fibers.

Source record↗
NASA NTRS2005

Design Considerations for High Temperature Power Inductors

A uniform B-field approximation model is used to develop design formulas for single-layer wound, toroidal core, ac power inductors that must handle a specified current. Such a geometry is well suited for high temperature, high frequency inductors, where removal of heat from the core becomes critical. Explicit expressions are derived for core radii, core and winding volumes, winding turns and core permeability as functions of a dimensional scaling ratio (S). A limit on the maximum allowed core B-field leads to the result that the minimum core volume is proportional to the permeability, which has a lower bound. Plots versus S are provided for a specific case, to show that good designs can be picked in the overlap regions around the minima in mass and overall size, where the mass and size are relatively flat. Data to 250 C are presented for an MPP core based inductor to show that a quasi-linear, high temperature inductor can be constructed with available materials. A similar development is applied to a toroidal air-core geometry, showing that for the same ratings, such an inductor is considerably bigger and more massive, at least in the single-layer version.

Niedra, Janis M.↗
NASA NTRS2006

Representation of the Geosynchronous Plasma Environment in Spacecraft Charging Calculations

Historically, our ability to predict and postdict spacecraft surface charging has been limited by the characterization of the plasma environment. One difficulty lies in the common practice of fitting the plasma data to a Maxwellian or Double Maxwellian distribution function, which may not represent the data well for charging purposes. We use electron and ion flux spectra measured by the Los Alamos National Laboratory (LANL) Magnetospheric Plasma Analyzer (MPA) to examine how the use of different spectral representations of the charged particle environment in computations of spacecraft potentials during magnetospheric substorms affects the accuracy of the results. We calculate the spacecraft potential using both the measured fluxes and several different fits to these fluxes. These measured fluxes have been corrected for the difference between the measured and calculated potential. The potential computed using the measured fluxes and the best available material properties of graphite carbon, with a secondary electron escape fraction of 81%, is within a factor of three of the measured potential for 87% of the data. Potentials calculated using a Kappa function fit to the incident electron flux distribution function and a Maxwellian function fit to the incident ion flux distribution function agree with measured potentials nearly as well as do potentials calculated using the measured fluxes. Alternative spectral representations gave less accurate estimates of potential. The use of all the components of the net flux, along with spacecraft specific average material properties, gives a better estimate of the spacecraft potential than the high energy flux alone.

Davis, V. A.↗
NASA NTRS1999

WorldWide ElectroActive Polymers

For many years, electroactive polymers (EAP) received relatively little attention due to the small number of available materials as well as their limited actuation capability.

Electroactive Polymers Actuators↗
NASA NTRS2008

Characterization of Ni19.5Ti50.5Pd25Pt5 High-Temperature Shape Memory Alloy Springs and their Potential Application in Aeronautics

Shape memory alloys (SMAs) have been used as actuators in many different industries since the discovery of the shape memory effect, but the use of SMAs as actuation devices in aeronautics has been limited due to the temperature constraints of commercially available materials. Consequently, work is being done at NASA's Glenn Research Center to develop new SMAs capable of being used in high temperature environments. One of the more promising high-temperature shape memory alloys (HTSMAs) is Ni19.5Ti50.5Pd25Pt5. Recent work has shown that this material is capable of being used in operating environments of up to 250 C. This material has been shown to have very useful actuation capabilities, demonstrating repeatable strain recoveries up to 2.5% in the presence of an externally applied load. Based on these findings, further work has been initiated to explore potential applications and alternative forms of this alloy, such as springs. Thus, characterization of Ni19.5Ti50.5Pd25Pt5 springs, including their mechanical response and how variations in this response correlate to changes in geometric parameters, are discussed. The effects of loading history, or training, on spring behavior were also investigated. A comparison of the springs with wire actuators is made and the benefits of using one actuator form as opposed to the other discussed. These findings are used to discuss design considerations for a surge-control mechanism that could be used in the centrifugal compressor of a T-700 helicopter engine.

Stebner, Aaron↗