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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

A Model for Tetragonal Lysozyme Crystal Nucleation and Growth

Macromolecular crystallization is a complex process, involving a system that typically has 5 or more components (macromolecule, water, buffer + counter ion, and precipitant). Whereas small molecules have only a few contacts in the crystal lattice, macromolecules generally have 10's or even 100's of contacts between molecules. These can range from hydrogen bonds (direct or water-mediated), through van der Waals, hydrophobic, salt bridges, and ion-mediated contacts. The latter interactions are stronger and require some specificity in the molecular alignment, while the others are weaker, more prevalent, and more promiscuous, i.e., can be readily broken and reformed between other sites. Formation of a consistent, ordered, 3D structure may be difficult or impossible in the absence of any or presence of too many strong interactions. Further complicating the process is the inherent structural asymmetry of monomeric (single chain) macromolecules. The process of crystal nucleation and growth involves the ordered assembly of growth units into a defined 3D lattice. We suggest that for many macromolecules, particularly those that are monomeric, this involves a preliminary solution-phase assembly process into a growth unit having some symmetry prior to addition to the lattice, recapitulating the initial stages of the nucleation process. If this model is correct then fluids and crystal growth models assuming a strictly monodisperse nutrient solution need to be revised. This model has been developed from experimental evidence based upon face growth rate, AFM, and fluorescence energy transfer data for the nucleation and growth of tetragonal lysozyme crystals.

Pusey, Marc L.↗
NASA NTRS2003

Advanced Sensor Systems for Biotelemetry

The present invention relates to telemetry-based sensing systems that continuously measures physical, chemical and biological parameters. More specifically, these sensing systems comprise a small, modular, low-power implantable biotelemetry system capable of continuously sensing physiological characteristics using implantable transmitters, a receiver, and a data acquisition system to analyze and record the transmitted signal over several months. The preferred embodiment is a preterm labor and fetal monitoring system. Key features of the invention include Pulse Interval Modulation (PIM) that is used to send temperature and pressure information out of the biological environment. The RF carrier frequency is 174-216 MHz and a pair of RF bursts (pulses) is transmitted at a frequency of about 1-2 Hz. The transmission range is 3 to 10 feet, depending on the position of the transmitter in the body and its biological environment. The entire transmitter is encapsulated in biocompatible silicone rubber. Power is supplied by on-board silver-oxide batteries. The average power consumption of the current design is less than 30 microW, which yields a lifetime of approximately 6 - 9 months. Chip-on-Board technology (COB) drastically reduces the size of the printed circuit board from 38 x 28 mm to 22 x 8 mm. Unpackaged dies are flip-chip bonded directly onto the printed circuit board, along with surface mount resistors and capacitors. The invention can monitor additional physiological parameters including, but not limited to, ECG, blood gases, glucose, and ions such as calcium, potassium, and sodium.

Hines, John W.↗
NASA NTRS1997

High-Temperature Adhesive Strain Gage Developed

Researchers at the NASA Lewis Research Center have developed a unique strain gage and adhesive system for measuring the mechanical properties of polymers and polymer composites at elevated temperatures. This system overcomes some of the problems encountered in using commercial strain gages and adhesives. For example, typical commercial strain gage adhesives require a postcure at temperatures substantially higher than the maximum test temperature. The exposure of the specimen to this temperature may affect subsequent results, and in some cases may be higher than the glass-transition temperature of the polymer. In addition, although typical commercial strain gages can be used for short times at temperatures up to 370 C, their long-term use is limited to 230 C. This precludes their use for testing some high-temperature polyimides near their maximum temperature capability. Lewis' strain gage and adhesive system consists of a nonencapsulated, unbacked gage grid that is bonded directly to the polymer after the specimen has been cured but prior to the normal postcure cycle. The gage is applied with an adhesive specially formulated to cure under the specimen postcure conditions. Special handling, mounting, and electrical connection procedures were developed, and a fixture was designed to calibrate each strain gage after it was applied to a specimen. A variety of tests was conducted to determine the performance characteristics of the gages at elevated temperatures on PMR-15 neat resin and titanium specimens. For these tests, which included static tension, thermal exposure, and creep tests, the gage and adhesive system performed within normal strain gage specifications at 315 C. An example of the performance characteristics of the gage can be seen in the figure, which compares the strain gage measurement on a polyimide specimen at 315 C with an extensometer measurement.

Pereira, J. Michael↗
NASA NTRS2003

Advanced sensor systems for biotelemetry

The present invention relates to telemetry-based sensing systems that continuously measures physical, chemical and biological parameters. More specifically, these sensing systems comprise a small, modular, low-power implantable biotelemetry system capable of continuously sensing physiological characteristics using implantable transmitters, a receiver, and a data acquisition system to analyze and record the transmitted signal over several months. The preferred embodiment is a preterm labor and fetal monitoring system. Key features of the invention include Pulse Interval Modulation (PIM) that is used to send temperature and pressure information out of the biological environment. The RF carrier frequency is 174-216 MHz and a pair of RF bursts (pulses) is transmitted at a frequency of about 1-2 Hz. The transmission range is 3 to 10 feet, depending on the position of the transmitter in the body and its biological environment. The entire transmitter is encapsulated in biocompatible silicone rubber. Power is supplied by on-board silver-oxide batteries. The average power consumption of the current design is less than 30 .mu.W., which yields a lifetime of approximately 6-9 months. Chip-on-Board technology (COB) drastically reduces the size of the printed circuit board from 38.times.28 mm to 22.times.8 mm. Unpackaged dies are flip-chip bonded directly onto the printed circuit board, along with surface mount resistors and capacitors. The invention can monitor additional physiological parameters including, but not limited to, ECG, blood gases, glucose, and ions such as calcium, potassium, and sodium.

Hines, John W.↗
NASA NTRS2004

AIN-Based Packaging for SiC High-Temperature Electronics

Packaging made primarily of aluminum nitride has been developed to enclose silicon carbide-based integrated circuits (ICs), including circuits containing SiC-based power diodes, that are capable of operation under conditions more severe than can be withstood by silicon-based integrated circuits. A major objective of this development was to enable packaged SiC electronic circuits to operate continuously at temperatures up to 500 C. AlN-packaged SiC electronic circuits have commercial potential for incorporation into high-power electronic equipment and into sensors that must withstand high temperatures and/or high pressures in diverse applications that include exploration in outer space, well logging, and monitoring of nuclear power systems. This packaging embodies concepts drawn from flip-chip packaging of silicon-based integrated circuits. One or more SiC-based circuit chips are mounted on an aluminum nitride package substrate or sandwiched between two such substrates. Intimate electrical connections between metal conductors on the chip(s) and the metal conductors on external circuits are made by direct bonding to interconnections on the package substrate(s) and/or by use of holes through the package substrate(s). This approach eliminates the need for wire bonds, which have been the most vulnerable links in conventional electronic circuitry in hostile environments. Moreover, the elimination of wire bonds makes it possible to pack chips more densely than was previously possible.

Savrun, Ender↗
NASA NTRS2013

Nickel-Graphite Composite Compliant Interface and/or Hot Shoe Material

Next-generation high-temperature thermoelectric-power-generating devices will employ segmented architectures and will have to reliably withstand thermally induced mechanical stresses produced during component fabrication, device assembly, and operation. Thermoelectric materials have typically poor mechanical strength, exhibit brittle behavior, and possess a wide range of coefficient of thermal expansion (CTE) values. As a result, the direct bonding at elevated temperatures of these materials to each other to produce segmented leg components is difficult, and often results in localized microcracking at interfaces and mec hanical failure due to the stresses that arise from the CTE mismatch between the various materials. Even in the absence of full mechanical failure, degraded interfaces can lead to increased electrical and thermal resistances, which adversely impact conversion efficiency and power output. The proposed solution is the insertion of a mechanically compliant layer, with high electrical and thermal conductivity, between the low- and high-temperature segments to relieve thermomechanical stresses during device fabrication and operation. This composite material can be used as a stress-relieving layer between the thermoelectric segments and/or between a thermoelectric segment and a hot- or cold-side interconnect material. The material also can be used as a compliant hot shoe. Nickel-coated graphite powders were hot-pressed to form a nickel-graphite composite material. A freestanding thermoelectric segmented leg was fabricated by brazing the compliant pad layer between the high-temperature p- Zintl and low-temperature p-SKD TE segments using Cu-Ag braze foils. The segmented leg stack was heated in vacuum under a compressive load to achieve bonding. The novelty of the innovation is the use of composite material that re duces the thermomechanical stresses en - countered in the construction of high-efficiency, high-temperature therm - o-electric devices. The compliant pad enables the bonding of dissimilar thermoelectric materials while maintaining the desired electrical and thermal properties essential for efficient device operation. The modulus, CTE, electrical, and thermal conductances of the composite can be controlled by varying the ratio of nickel to graphite.

Firdosy, Samad A.↗
NASA NTRS2015

Conformal Ablative Thermal Protection System for Small and Large Scale Missions: Approaching TRL 6 for Planetary and Human Exploration Missions and TRL 9 for Small Probe Missions

In 2011, NASAs Aeronautics Research Mission Directorate (ARMD) funded an effort to develop an ablative thermal protection system (TPS) material that would have improved properties when compared to Phenolic Impregnated Carbon Ablator (PICA) and AVCOAT. Their goal was a conformal material, processed with a flexible reinforcement that would result in similar or better thermal characteristics and higher strain-to-failure characteristics that would allow for easier integration on flight aeroshells than then-current rigid ablative TPS materials. In 2012, NASAs Space Technology Mission Directorate (STMD) began funding the maturation of the best formulation of the game changing conformal ablator, C-PICA. Progress has been reported at IPPW over the past three years, describing C-PICA with a density and recession rates similar to PICA, but with a higher strain-to-failure which allows for direct bonding and no gap fillers, and even more important, with thermal characteristics resulting in half the temperature rise of PICA. Overall, C-PICA should be able to replace PICA with a thinner, lighter weight, less complicated design. These characteristics should be particularly attractive for use as backshell TPS on high energy planetary entry vehicles. At the end of this year, the material should be ready for missions to consider including in their design, in fact, NASAs Science Mission Directorate (SMD) is considering incentivizing the use of C-PICA in the next Discovery Proposal call. This year both scale up of the material to large (1-m) sized pieces and the design and build of small probe heatshields for flight tests will be completed. NASA, with an industry partner, will build a 1-m long manufacturing demonstration unit (MDU) with a shape based on a mid LD lifting body. In addition, in an effort to fly as you test and test as you fly, NASA, with a second industry partner, will build a small probe to test in the Interactive Heating Facility (IHF) arc jet and, using nearly the same design, build the aeroshell and TPS, with instrumentation, for a small probe flight test article, due to fly in 2017. At the end of the year, the C-PICA will be at TRL 5+, and with the flight data in 2017, it will be at TRL 9 for missions needs with C-PICA at a small scale (12 diameter). The scale-up and small probe efforts will be de-scribed in this presentation.

Conformal Ablative↗
NASA NTRS2016

Conformal Ablative Thermal Protection Systems (CA-TPS) for Venus and Saturn Backshells

This poster provides an overview of the work performed to date on the Conformal Ablative TPS (CA-TPS) element of the TPSM project out of GCDP. Under this element, NASA is developing improved ablative TPS materials based on flexible felt for reinforcement rather than rigid reinforcements. By replacing the reinforcements with felt, the resulting materials have much higher strain-to-failure and are much lower in thermal conductivity than their rigid counterparts. These characteristics should allow for larger tile sizes, direct bonding to aeroshells and even lower weight TPS. The conformal phenolic impregnated carbon felt (C-PICA) is a candidate for backshell TPS for both Venus and Saturn entry vehicles.

Saturn↗
NASA NTRSDate not supplied

Toward Large Field-of-view X-ray Spectrometers with Magnetic Microcalorimeters

A future X-ray telescope mission like Lynx, a X-ray flagship mission concept, requires a large field of view, high energy resolution, and high spatial resolution. The Magnetic Microcalorimeter (MMC) detectors we are developing for such a mission feature a 5-arcminute field of view, approximately 100,000 pixels, each spanning 0.5–1 arcsecond. These detectors require the readout of 8,000 sensors. Three different array types have been designed to meet scientific goals, two of which utilize thermal multiplexing to reduce the number of readout channels in a scheme called “Hydra.” We are currently fabricating detectors on a recently completed buried wiring wafer with connections to every sensor. The sensors are read out using a microwave multiplexer (μMUX) with flux ramp modulation. A single μMUX can read out approximately 1,000 sensors with only two feed lines. We will report on the test of the first two-dimensional μMUX chip, consisting of 78 resonators. μMUX chips that pass screening will be directly bonded to MMC array chips using indium bump bonding. In parallel, we have tested a kinetic inductance traveling wave parametric amplifier (KI-TWPA) to amplify signals at low temperatures. The KI-TWPA exhibits extremely low internal noise, approaching the standard quantum limit. Since the energy resolution of an MMC is primarily limited by the readout system, the KI-TWPA is an ideal amplifier for MMCs with μMUX readout. We recently measured the readout noise of a μMUX with a KI-TWPA, demonstrating its capability for reading out MMC arrays. We present the design and fabrication of the latest MMC detectors, along with its readout performance.

Magntic Microcalorimeters↗
NASA NTRS1985

Rapid adhesive bonding of advanced composites and titanium

Rapid adhesive bonding (RAB) concepts utilize a toroid induction technique to heat the adhesive bond line directly. This technique was used to bond titanium overlap shear specimens with 3 advanced thermoplastic adhesives and APC-2 (graphite/PEEK) composites with PEEK film. Bond strengths equivalent to standard heated-platen press bonds were produced with large reductions in process time. RAB produced very strong bonds in APC-2 adherend specimens; the APC-2 adherends were highly resistant to delamination. Thermal cycling did not significantly affect the shear strengths of RAB titanium bonds with polyimide adhesives. A simple ultrasonic non-destructive evaluation process was found promising for evaluating bond quality.

Stein, B. A.↗
NASA NTRS1978

Totally confined explosive welding

The undesirable by-products of explosive welding are confined and the association noise is reduced by the use of a simple enclosure into which the explosive is placed and in which the explosion occurs. An infrangible enclosure is removably attached to one of the members to be bonded at the point directly opposite the bond area. An explosive is completely confined within the enclosure at a point in close proximity to the member to be bonded and a detonating means is attached to the explosive. The balance of the enclosure, not occupied by explosive, is filled with a shaped material which directs the explosive pressure toward the bond area. A detonator adaptor controls the expansion of the enclosure by the explosive force so that the enclosure at no point experiences a discontinuity in expansion which causes rupture. The use of the technique is practical in the restricted area of a space station.

Bement, L. J.↗
NASA NTRS2000

[Methods Used for Monitoring Cure Reactions in Real-time in an Autoclave]

The goal of the research was to investigate methods for monitoring cure reactions in real-time in an autoclave. This is of particular importance to NASA Langley Research Center because polyimides were proposed for use in the High Speed Civil Transport (HSCT) program. Understanding the cure chemistry behind the polyimides would allow for intelligent processing of the composites made from their use. This work has led to two publications in peer-reviewed journals and a patent. The journal articles are listed as Appendix A which is on the instrument design of the research and Appendix B which is on the cure chemistry. Also, a patent has been awarded for the instrumental design developed under this grant which is given as Appendix C. There has been a significant amount of research directed at developing methods for monitoring cure reactions in real-time within the autoclave. The various research efforts can be categorized as methods providing either direct chemical bonding information or methods that provide indirect chemical bonding information. Methods falling into the latter category are fluorescence, dielectric loss, ultrasonic and similar type methods. Correlation of such measurements with the underlying chemistry is often quite difficult since these techniques do not allow monitoring of the curing chemistry which is ultimately responsible for material properties. Direct methods such as vibrational spectroscopy, however, can often be easily correlated with the underlying chemistry of a reaction. Such methods include Raman spectroscopy, mid-IR absorbance, and near-IR absorbance. With the recent advances in fiber-optics, these spectroscopic techniques can be applied to remote on-line monitoring.

Cooper, John B.↗
NASA NTRS1995

A Method Based on Radiative Cooling for Detecting Structural Changes in Undercooled Metallic Liquids

We introduce a structure-sensitive parameter for undercooled melts which can be measured in containerless processing experiments. We have established that the ratio, R(T), of hemispherical total emissivity epsilon(sub T)(T) to constant-pressure specific heat c(sub p)(T) can serve as an indicator which is sensitive to any changes in short range atomic order in undercooled metallic melts. R(T) (triple bonds) epsilon(sub T)(T)/c(sub p)(T) values for nickel, zirconium, and silicon have been obtained using the high temperature electrostatic levitator while the levitated melts were undergoing purely radiative cooling into the deeply undercooled region. R(T) plots for undercooled liquid nickel and zirconium indicate no significant change in short-range structure from their melting temperatures to 15% undercooling. In contrast, liquid silicon shows marked short-range structural changes beginning above its melting temperature and extending throughout the undercooled region. The short-range structure of liquid silicon is related to the highly-directional covalent bonding which characterizes its solid form. The nickel and zirconium data show that epsilon(sub T) varies linearly with T, in support of metal emissivity theories.

Rulison, Aaron J.↗
NASA NTRS1978

Interconnecting conductively coated coverslides

The International Sun Earth Explorer-1 has the requirement that the entire outer surface of the spacecraft be conductive. A transparent coating of indium oxide was deposited for that reason on the satellite's solar cell coverglasses in order to give them a conductive surface, and the surfaces were interconnected to ground. This paper examines the interconnector attachment problem. On the ISEE-1, wires were bonded to the coverglasses by using a conductive epoxy; the resistance of these bonds increased dramatically with time. A program was initiated to find the functional cause of the resistance increase and to flight-qualify an alternative method of bonding. It was found the tests initiated were insufficient to find the cause of resistance increase and that an alternative solution of using indium solder is acceptable for bonding wires directly to indium oxide.

Gaddy, E. M.↗
NASA NTRS1992

Thread-Pull Test Of Curing Adhesive

Hardness (and degree of cure) of adhesive layer measured by pulling previously inserted thread out of layer. Strength of bond measured directly on assembly rather than on samples, which can be misleading.

Johnson, James A.↗
NASA NTRS1993

Performance of silvered Teflon (trademark) thermal control blankets on spacecraft

Silverized Teflon (Ag/FEP) is a widely used passive thermal control material for space applications. The material has a very low alpha/e ratio (less than 0.1) for low operating temperatures and is fabricated with various FEP thicknesses (as the Teflon thickness increases, the emittance increases). It is low outgassing and, because of its flexibility, can be applied around complex, curved shapes. Ag/FEP has achieved multiyear lifetimes under a variety of exposure conditions. This has been demonstrated by the Long Duration Exposure Facility (LDEF), Solar Max, Spacecraft Charging at High Altitudes (SCATHA), and other flight experiments. Ag/FEP material has been held in place on spacecraft by a variety of methods: mechanical clamping, direct adhesive bonding of tapes and sheets, and by Velcro(TM) tape adhesively bonded to back surfaces. On LDEF, for example, 5-mil blankets held by Velcro(TM) and clamping were used for thermal control over 3- by 4-ft areas on each of 17 trays. Adhesively bonded 2- and 5-mil sheets were used on other LDEF experiments, both for thermal control and as tape to hold other thermal control blankets in place. Performance data over extended time periods are available from a number of flights. The observed effects on optical properties, mechanical properties, and surface chemistry will be summarized in this paper. This leads to a discussion of performance life estimates and other design lessons for Ag/FEP thermal control material.

Pippin, Gary↗
NASA NTRS1992

Advanced composites structural concepts and materials technologies for primary aircraft structures: Structural response and failure analysis

Non-linear analysis methods were adapted and incorporated in a finite element based DIAL code. These methods are necessary to evaluate the global response of a stiffened structure under combined in-plane and out-of-plane loading. These methods include the Arc Length method and target point analysis procedure. A new interface material model was implemented that can model elastic-plastic behavior of the bond adhesive. Direct application of this method is in skin/stiffener interface failure assessment. Addition of the AML (angle minus longitudinal or load) failure procedure and Hasin's failure criteria provides added capability in the failure predictions. Interactive Stiffened Panel Analysis modules were developed as interactive pre-and post-processors. Each module provides the means of performing self-initiated finite elements based analysis of primary structures such as a flat or curved stiffened panel; a corrugated flat sandwich panel; and a curved geodesic fuselage panel. This module brings finite element analysis into the design of composite structures without the requirement for the user to know much about the techniques and procedures needed to actually perform a finite element analysis from scratch. An interactive finite element code was developed to predict bolted joint strength considering material and geometrical non-linearity. The developed method conducts an ultimate strength failure analysis using a set of material degradation models.

Dorris, William J.↗