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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

The Abundance and Isotopic Composition of Hg in Extraterrestrial Materials

During the past three year grant period we made excellent progress in our study of the abundances and isotopic compositions of Hg and other volatile trace elements in extraterrestrial materials. As part of my startup package I received funds to construct a state-of-the-art experimental facility to study gas-solid reaction kinetics. Much of our effort was spent developing the methodology to measure the abundance and isotopic composition of Hg at ultratrace levels in solid materials. In our first study, the abundance and isotopic composition of Hg was determined in bulk samples of the Murchison (CM) and Allende (CV) carbonaceous chondrites. We have continued our study of mercury in primitive meteorites and expanded the suite of meteorites to include other members of the CM and CV chondrite group as well as CI and CO chondrites. Samples of the CI chondrite Orgueil, the CM chondrites Murray, Nogoya, and Cold Bokkeveld, the CO chondrites Kainsaz, Omans, and Isna, and the CV chondrites Vigarano, Mokoia, and Grosnaja were tested. We have developed a thermal analysis ICP-MS technique and applied it to the study of a suite of thermally labile elements (Zn, As, Se, Cd, In, Sn, Sb, Te, Hg, Au, Tl, Pb, and Bi) in geologic materials as well.

Lauretta, D. S.↗
NASA NTRS1989

Beneficiation of lunar ilmenite feedstock

The chemical and physical characteristics are reviewed of ilmenite in lunar material and high precision, low abundance analyses were developed for platinoids and other possibly important elements in space materials using an induced coupled plasma mass spectrometer.

Ruiz, J.↗
NASA NTRS2005

Characterization of Meta-Materials Using Computational Electromagnetic Methods

An efficient and powerful computational method is presented to synthesize a meta-material to specified electromagnetic properties. Using the periodicity of meta-materials, the Finite Element Methodology (FEM) is developed to estimate the reflection and transmission through the meta-material structure for a normal plane wave incidence. For efficient computations of the reflection and transmission over a wide band frequency range through a meta-material a Finite Difference Time Domain (FDTD) approach is also developed. Using the Nicholson-Ross method and the Genetic Algorithms, a robust procedure to extract electromagnetic properties of meta-material from the knowledge of its reflection and transmission coefficients is described. Few numerical examples are also presented to validate the present approach.

Deshpande, Manohar↗
NASA NTRS2016

Meso-Scale Digital Materials: Modular, Reconfigurable, Lattice-Based Structures

We present a modular, reconfigurable system for building large structures. This system uses discrete lattice elements, called digital materials, to reversibly assemble ultralight structures that are 99.7% air and yet maintain sufficient specific stiffness for a variety of structural applications and loading scenarios. Design, manufacturing, and characterization of modular building blocks are described, including struts, nodes, joints, and build strategies. Simple case studies are shown using the same building blocks in three different scenarios: a bridge, a boat, and a shelter. Field implementation and demonstration is supplemented by experimental data and numerical simulation. A simplified approach for analyzing these structures is presented which shows good agreement with experimental results.

Reconfigurable↗
NASA NTRS1986

Composite structural materials

Overall emphasis is on basic long-term research in the following categories: constituent materials, composite materials, generic structural elements, processing science technology; and maintaining long-term structural integrity. Research in basic composition, characteristics, and processing science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to present and future problems. Detailed descriptions of the progress achieved in the various component parts of this comprehensive program are presented.

Loewy, R.↗
NASA NTRS2001

Multi-shock assembly for protecting a spacecraft surface from hypervelocity impactors

A hypervelocity impact shield assembly for protecting a spacecraft surface from hypervelocity impactors. The shield assembly includes at least one sacrificial impactor disrupting/shocking layer of hypervelocity impactor disrupting/shocking material. A primary spacing element, including space-rated open cell foam material, is positioned between the at least one sacrificial impactor disrupting/shocking layer and a spacecraft surface. A cover member is arranged and disposed relative to the sacrificial impactor disrupting/shocking layer and the primary spacing element to maintain the integrity of the hypervelocity impact shield assembly. In the event of exposure to a hypervelocity impactor, the sacrificial impactor disrupting/shocking layer is perforated while shocking the impactor breaking it into fragments, and/or melting it, and/or vaporizing it, thus providing a dispersion in the form of an expanding debris cloud/plume which spreads the impact energy of the impactor over a volume formed by the primary spacing element between the sacrificial impactor disrupting/shocking layer and the spacecraft surface. This significantly reduces impact lethality at the spacecraft surface. The space-rated open cell foam material provides an extremely lightweight, low-cost, efficient means of spacing and supporting the at least one sacrificial impactor disrupting/shocking layer before, during, and after launch. In a preferred embodiment, the invention is in the form of a multi-shock assembly including a plurality of sacrificial impactor disrupting/shocking layers. In such instance, the hypervelocity impact shield assembly includes a plurality of secondary spacing elements. Each secondary spacing element is positioned adjacent an associated sacrificial impactor disrupting/shocking layer to form a multi-shock subassembly. Thus, a plurality of multi-shock subassemblies are provided which include alternating layers of sacrificial impactor disrupting/shocking layers and secondary spacing elements.

Dvorak, Bruce D.↗
NASA NTRS1980

Corotational velocity strain formulations for nonlinear analysis of beams and axisymmetric shells

Finite element formulations for large strain, large displacement problems are formulated using a kinematic description based on the corotational components of the velocity strain. The corotational components are defined in terms of a system that rotates with each element and approximates the rotation of the material. To account for rotations of the material relative to this element system, extra terms are introduced in the velocity strain equations. Although this formulation is incremental, in explicitly integrated transient problems it compares very well with formulations that are not.

Belytschko, T.↗
NASA NTRS2012

Constraining the Origin of Impact Craters on Al Foils from the Stardust Interstellar Dust Collector

Preliminary examination (PE) of the aerogel tiles and Al foils from the Stardust Interstellar Dust Collector has revealed multiple impact features. Some are most likely due to primary impacts of interstellar dust (ISD) grains, and others are associated with secondary impacts of spacecraft debris, and possibly primary impacts of interplanetary dust particles (IDPs) [1, 2]. The current focus of the PE effort is on constraining the origin of the individual impact features so that definitive results from the first direct laboratory analysis of contemporary ISD can be reported. Because crater morphology depends on impacting particle shape and composition, in addition to the angle and direction of impact, unique particle trajectories are not easily determined. However, elemental analysis of the crater residues can distinguish real cosmic dust from the spacecraft debris, due to the low cosmic abundance of many of the elements in the spacecraft materials. We present here results from the elemental analysis of 24 craters and discuss the possible origins of 4 that are identified as candidate ISD impacts

Stroud, Rhonda M.↗
NASA NTRS1992

Chemical transport during formation and alteration of Martian impact and volcanic deposits

Much of the surface of Mars, including volcanic and cratered terrains, probably experienced alteration and degassing processes. These processes may have depleted or enriched many important elements in surface materials, including bedrock, dust, and soils. The composition of the martian soil may represent the best estimate, for some elements, of the average composition of the martian crust, similar to the composition of loess created by glacial action on the Earth. The martian soil may represent the only convenient, globally or regionally averaged sample of the martian crust. In order to understand the composition of the source material for the soil, however, we need to understand the contributions of volcanic vs. impact sources for this material and the chemical fractionations involved in its production. The processes to be addressed include degassing of volcanic deposits, as observed in the Valley of Ten Thousand Smokes at Katmai, Alaska, and degassing of meltbearing impact ejecta as inferred for suevite ejecta sheets at the Ries Crater, and alteration or palagonitization of volcanic deposits, as documented for volcanos in British Columbia and many other volcanic terrains, and impact crater deposits. The process of palagonitization has been the subject of several studies with reference to Mars, and palagonite is a good analogue for the spectroscopic properties of the martian dust. The role of impact in cratering has not been as well studied, although other researchers have established that both degassing and alteration are common features of impact crater deposits. Other relevant sources of experimental data include the extensive literature on the corrosion of nuclear waste glass and leaching of shocked materials.

Newsom, H. E.↗
NASA NTRS2005

The Abundance and Isotopic Composition of Hg in Extraterrestrial Materials

During the three year grant period we made excellent progress in our study of the abundances and isotopic compositions of Hg and other volatile trace elements in extraterrestrial materials. At the time the grant started, our collaborating PI, Dante Lauretts, was a postdoctoral research associate working with Peter Buseck at Arizona State University. The work on chondritic Hg was done in collaboration with Dante Lauretta and Peter Buseck and this study was published in Lauretta et a1 (2001a). In July, 2001 Dante Lauretta accepted a position as an Assistant Professor in the Lunar and Planetary Laboratory at the University of Arizona. His funding was transferred and this grant has supported much of his research activities during his first two years at the U of A. Several other papers are in preparation and will be published soon. We presented papers on this topic at Goldschmidt Conferences, the Lunar and Planetary Science Conferences, and the Annual Meetings of the Meteoritical Society. The work done under this grant has spurred several new directions of inquiry, which we are still pursuing. Included in this paper are the studies of bulk abundances and isotopic compositions of metreoritic Mercury, and the development of a thermal analysis ICP-MS technique applied to thermally liable elements.

Blum, J. D.↗
NASA NTRS1990

Users manual for AUTOMESH-2D: A program of automatic mesh generation for two-dimensional scattering analysis by the finite element method

AUTOMESH-2D is a computer program specifically designed as a preprocessor for the scattering analysis of two dimensional bodies by the finite element method. This program was developed due to a need for reproducing the effort required to define and check the geometry data, element topology, and material properties. There are six modules in the program: (1) Parameter Specification; (2) Data Input; (3) Node Generation; (4) Element Generation; (5) Mesh Smoothing; and (5) Data File Generation.

Hua, Chongyu↗
NASA NTRS1996

Highly Accurate Beam Torsion Solutions Using the p-Version Finite Element Method

A new treatment of the classical beam torsion boundary value problem is applied. Using the p-version finite element method with shape functions based on Legendre polynomials, torsion solutions for generic cross-sections comprised of isotropic materials are developed. Element shape functions for quadrilateral and triangular elements are discussed, and numerical examples are provided.

Smith, James P.↗
NASA NTRS1993

Design considerations for a Space Shuttle Main Engine turbine blade made of single crystal material

Nonlinear finite-element structural analyses were performed on the first stage high-pressure fuel turbopump blade of the Space Shuttle Main Engine. The analyses examined the structural response and the dynamic characteristics at typical operating conditions. Single crystal material PWA-1480 was considered for the analyses. Structural response and the blade natural frequencies with respect to the crystal orientation were investigated. The analyses were conducted based on typical test stand engine cycle. Influence of combined thermal, aerodynamic, and centrifugal loadings was considered. Results obtained showed that the single crystal secondary orientation effects on the maximum principal stresses are not highly significant.

Abdul-Aziz, A.↗
NASA NTRS1977

Doubly-curved variable-thickness isoparametric heterogeneous finite element

This paper describes an element streamlined for the analysis of doubly-curved, variable-thickness structural components and illustrates its effective application to vibration and static problems. The element is isoparametric, doubly-curved, thin-shell and triangular with variable thickness and accounts for anisotropic, inhomogeneous elastic material behavior. The element has six nodes (three corner and three mid-side) with five degrees-of-freedom (DOF) per node - three translations and two rotations. Quadratic isoparametric interpolation polynomials are used to express the element geometry and displacement variables in terms of corresponding nodal variables.

Minich, M. D.↗
NASA NTRS2010

History of Space Shuttle Main Engine Turbopump Bearing Testing at the Marshall Space Flight Center

The Space Shuttle is propelled into orbit by two solid rocket motors and three liquid fed main engines. After the solid motors fall away, the shuttle engines continue to run for a total time of 8 minutes. These engines are fed propellants by low and high pressure turbopumps. A critical part of the turbopump is the main shaft that supports the drive turbine and the pump inducer and impeller. Rolling element bearings hold the shaft in place during rotation. If the bearings were to fail, the shaft would move, allowing components to rub in a liquid oxygen or hydrogen environment, which could have catastrophic results. These bearings are required to spin at very high speeds, support radial and axial loads, and have high wear resistance without the benefit of a conventional means of lubrication. The Rocketdyne built Shuttle turbopumps demonstrated their capability to perform during launches; however, the seven hour life requirement was not being met. One of the limiting factors was the bearings. In the late 1970's, an engineering team was formed at the Marshall Space Flight Center (MSFC), to develop a test rig and plan for testing the Shuttle s main engine high pressure oxygen turbopump (HPOTP) bearings. The goals of the program were to better understand the operation of bearings in a cryogenic environment and to further develop and refine existing computer models used to predict the operational limits of these bearings. In 1982, testing began in a rig named the Bearing and Seal Material Tester or BSMT as it was commonly called. The first testing investigated the thermal margin and thermal runaway limits of the HPOTP bearings. The test rig was later used to explore potential bearing improvements in the area of increased race curvatures, new cage materials for better lubrication, new wear resistant rolling element materials, and other ideas to improve wear life. The most notable improvements during this tester s time was the incorporation of silicon nitride balls and bronze filled polytetrafluoroethylene (PTFE) cage inserts into the bearings and the anchoring of the SHABERTH bearing model and SINDA thermal computer model for cryogenic bearing analysis. In the mid 1990's, Pratt and Whitney (P&W) won the contract to deliver new high pressure turbopumps for the Shuttle s engines. P&W used two new bearing materials for the rings, Cronidur 30 and AISI 9310 steel and testing was needed on these new materials. A test rig had been designed and delivered to MSFC for testing hydrostatic bearings but with the need by Pratt to validate their bearings, the rig was reconfigured for testing of two ball bearings or a ball bearing and a roller bearing. The P&W bearings are larger than the Rocketdyne bearings and could not be installed in the BSMT. This new test rig was called the LH2 test rig and began operation in 1995. The LH2 test rig accumulated 75,000 seconds of run time in hydrogen. This test rig was valuable in two areas: validating the use of silicon nitride balls and rollers in Alternate Turbopump Development (ATD) bearings, which Pratt eventually used, and in proving the robustness of the balls and rollers after river marks appeared on the surface of the rolling elements. Individual test reports have been presented at conferences and symposiums throughout the years. This paper is a comprehensive report of all the bearing testing done at Marshall. It represents thousands of hours of dedication and labor in all engineering and technical fields that made this program a success.

Gibson, Howard↗
NASA NTRS1997

The Effect of Gravity on the Combustion of Bulk Metals

In recent years, metal combustion studies at the University of Colorado have focused on the effects of gravity (g) on the ignition and burning behavior of bulk metals. The impetus behind this effort is the understanding of the ignition conditions and flammability properties of structural metals found in oxygen (O2) systems for space applications. Since spacecraft are subjected to higher-than-1g loads during launch and reentry and to a zero-gravity environment while in orbit, the study of ignition and combustion of bulk metals at different gravitational accelerations is of great practical concern. From the scientific standpoint, studies conducted under low gravity conditions provide simplified boundary conditions, since buoyancy is removed, and make possible the identification of fundamental ignition and combustion mechanisms. This investigation is intended to provide experimental verification of the influence of natural convection on the burning behavior of metals. In addition, the study offers the first findings of the influence of gravity on ignition of bulk metals and on the combustion mechanism and structure of metal-oxygen, vapor-phase diffusion flames in a buoyancy-free environment. Titanium (Ti) and magnesium (Mg) metals were chosen because of their importance as elements of structural materials and their simple chemical composition-pure metals instead of multicomponent alloys to simplify chemical and spectroscopic analyses. In addition, these elements present the two different combustion modes observed in metals: heterogeneous or surface burning (for Ti) and homogeneous or gas-phase reaction (for Mg). Finally, Mg, Ti, and their oxides exhibit a wide range of thermophysical and chemical properties. Metal surface temperature profiles, critical and ignition temperatures, propagation rates, burning times, and spectroscopic measurements are obtained under normal and reduced gravity. Visual evidence of all phenomena is provided by high-speed photography.

Branch, Melvyn C.↗
NASA NTRS1994

Thermal analysis of a functionally graded material subject to a thermal gradient using the boundary element method

The boundary element method is utilized in this study to conduct thermal analysis of functionally graded composites, materials in which the internal microstructure or properties are explicitly tailored in order to obtain an optimal response, on the micromechanical (constituent) scale. A unique feature of the boundary element formulations used here is the use of circular shape functions to convert the two-dimensional integrations of the composite fibers to one dimensional integrations. Using the computer code BEST-CMS, the through the thickness temperature profiles are computed for a representative material with varying numbers of fibers and fiber spacing in the thickness direction. The computed temperature profiles are compared to those obtained using an alternate analytical theory which explicitly couples the heterogeneous microstructure to the global analysis. The boundary element results compared favorably to the analytical calculations, with discrepancies that are explainable based on the boundary element formulation. The results serve both to demonstrate the ability of the boundary element method to analyze these types of materials, and to verify the accuracy of the analytical theory.

Goldberg, Robert K.↗