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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 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Control/structure interaction conceptual design tool

The JPL Control/Structure Interaction Program is developing new analytical methods for designing micro-precision spacecraft with controlled structures. One of these, the Conceptual Design Tool, will illustrate innovative new approaches to the integration of multi-disciplinary analysis and design methods. The tool will be used to demonstrate homogeneity of presentation, uniform data representation across analytical methods, and integrated systems modeling. The tool differs from current 'integrated systems' that support design teams most notably in its support for the new CSI multi-disciplinary engineer. The design tool will utilize a three dimensional solid model of the spacecraft under design as the central data organization metaphor. Various analytical methods, such as finite element structural analysis, control system analysis, and mechanical configuration layout, will store and retrieve data from a hierarchical, object oriented data structure that supports assemblies of components with associated data and algorithms. In addition to managing numerical model data, the tool will assist the designer in organizing, stating, and tracking system requirements.

Briggs, Hugh C.↗
NASA NTRS1998

Health Monitoring of Composite Material Structures Using a Vibrometry Technique

Non-destructive evaluation (NDE) methods for quantifying and locating damage are essential for inspecting structures to ensure safety and reliability. Transmittance function monitoring is a potentially new NDE technique being tested as a tool to detect, quantify, and locate damage on flexible structures. The technique has a large spatial range that is practical for detecting damage on large composite material structures such as a reusable launch vehicle. The Transmittance Function (TF) theory is based on structural dynamics principles that define how vibration at one point in a structure is related to a force at another point. This relationship is called the Frequency Response Function (FRF). A Transmittance Function (TF) is derived as the ratio of FRFs, and can detect damage because the FRFs change due to damage. If one excitation is used for the testing, the force does not need to be measured to compute the TF. In the damage detection procedure, the structure is subjected to wide-band vibration and TFs are computed between different accelerometers to detect changes in the structure, presumably due to damage. In the first year of the project the TF method was tested on a bolted panel, a curved panel, and beams, all made of fiberglass. It was shown that damage could be detected using low frequency vibration, 250 to 1,250 Hz. The technique is sensitive to damage, but it requires storage of historical or pre-damage TFs for the healthy structure. This would become a large data storage requirement for large structures. Thus one objective for the second year of the project was to eliminate the need to store historical data. The second year report gives details of how storage of historical data was eliminated. Further results of testing panel structures are also given.

Schulz, Mark J.↗
NASA NTRS2006

Adding Hierarchical Objects to Relational Database General-Purpose XML-Based Information Managements

NETMARK is a flexible, high-throughput software system for managing, storing, and rapid searching of unstructured and semi-structured documents. NETMARK transforms such documents from their original highly complex, constantly changing, heterogeneous data formats into well-structured, common data formats in using Hypertext Markup Language (HTML) and/or Extensible Markup Language (XML). The software implements an object-relational database system that combines the best practices of the relational model utilizing Structured Query Language (SQL) with those of the object-oriented, semantic database model for creating complex data. In particular, NETMARK takes advantage of the Oracle 8i object-relational database model using physical-address data types for very efficient keyword searches of records across both context and content. NETMARK also supports multiple international standards such as WEBDAV for drag-and-drop file management and SOAP for integrated information management using Web services. The document-organization and -searching capabilities afforded by NETMARK are likely to make this software attractive for use in disciplines as diverse as science, auditing, and law enforcement.

Lin, Shu-Chun↗
NASA NTRS1980

Evaluation of existing knowledge of the tectonic history and lithospheric structure of South America

While data is available on the lithospheric and crustal structure of the Andes region of South America, there is limited knowledge of these aspects of the eastern portion of the continent. For this reason, a surface wave dispersion study of the area was initiated. Long period seismograms were obtained for a tripartite analysis of dispersion. A flow chart of the analysis to be conducted is presented along with a preliminary geologic/tectonic map that was prepared. Efforts to characterize the provinces identified in terms of their geological and geophysical parameters continue.

Keller, G. R.↗
NASA NTRS1984

Investigations of Thematic Mapper data dimensionality and features using field spectrometer data

Landsat-4 TM and MSS data, simulated from field reflectance spectra, are used to determine the dimensionality and structure of TM data (excluding the thermal band), demonstrate the relationships between the two sensors, and derive a Tasseled Cap Transformation for TM data. The simulated TM data are found to primarily occupy three dimensions, and to be concentrated into two adjoining and orthogonal planes and a transition zone between the two. The 'Plane of Vegetation' is shown to be comparable to the MSS Tasseled Cap plane, while the 'Plane of Soils' represents new information. The potential for improved spectral estimation of the relative mix of vegegation and soil in the field of view, and for improved monitoring of soil moisture status, is demonstrated.

Crist, E. P.↗
NASA NTRS1986

Application of multiple objective optimization techniques to finite element model tuning

This report examines tuning a finite element model using vector optimization techniques. Structural models using finite element theory often need to be adjusted so they can accurately simulate the real structure. The goal is to tune the model such that it will reproduce data derived from structural tests. First, the performance indices are extremized using multiple objective optimization theory, producing a set of possible solutions. Next, the solutions are rank ordered according to a decision maker's preferences to select the best answer. The tuning process was applied to a T-38 horizontal stabilizer. Numerous weighted solutions contained a best static deformation model, a best frequency model and three intermediate combinations of these two models. This automated procedure proved to be a versatile method capable of producing solutions for many types of tuning problems.

Devore, Charles R.↗
NASA NTRS1980

An enhancement of NASTRAN for the seismic analysis of structures

New modules, bulk data cards and DMAP sequence were added to NASTRAN to aid in the seismic analysis of nuclear power plant structures. These allow input consisting of acceleration time histories and result in the generation of acceleration floor response spectra. The resulting system contains numerous user convenience features, as well as being reasonably efficient.

Burroughs, J. W.↗
NASA NTRS1999

Iron, Manganese and Copper Release from Synthetic Hydroxyapatite

Kinetic stir-flow dissolution experiments were performed on iron- (Fe-SHA), manganese- (Mn-SHA), and copper- (Cu-SHA) containing synthetic hydroxyapatites. Solution treatments consisted of de-ionized water, citric acid and DTPA. Initially, Mn concentrations were higher than Cu concentrations and Fe concentrations were the lowest in all treatments. At later times Mn and Cu concentrations dropped in the DTPA treatment while Fe rose to the concentration similar to Mn and Cu. At all times, metal release concentrations in the water and citric acid treatments followed the trend of Mn>Cu>Fe. Rietveld analysis of x-ray diffraction data and ^31P NMR indicated that the metals substituted for Ca in the SHA structure. However, EPR data suggested that a metal (hydr)oxide phase existed either on the SHA surface or between the SHA crystallites. The metal concentration trend of Mn>Cu>Fe suggested that the initial solution metal concentrations are dependent on the dissolution of (hydr)oxides from SHA surfaces or between SHA crystallites. Similar metal concentrations at later times in the DTPA experiments suggests that metal concentrations were controlled by the release of Mn, Cu, or Fe from the SHA structure.

Sutter, B.↗
NASA NTRS2004

Multi-Sensor Distributive On-Line Processing, Visualization, and Analysis Infrastructure for an Agricultural Information System at the NASA Goddard Earth Sciences DAAC

The Goddard Space Flight Center Earth Sciences Data and Information Services Center (GES DISC) Distributed Active Center (DAAC) is developing an Agricultural Information System (AIS), evolved from an existing TRMM On-line Visualization and Analysis System precipitation and other satellite data products and services. AIS outputs will be ,integrated into existing operational decision support system for global crop monitoring, such as that of the U.N. World Food Program. The ability to use the raw data stored in the GES DAAC archives is highly dependent on having a detailed understanding of the data's internal structure and physical implementation. To gain this understanding is a time-consuming process and not a productive investment of the user's time. This is an especially difficult challenge when users need to deal with multi-sensor data that usually are of different structures and resolutions. The AIS has taken a major step towards meeting this challenge by incorporating an underlying infrastructure, called the GES-DISC Interactive Online Visualization and Analysis Infrastructure or "Giovanni," that integrates various components to support web interfaces that ,allow users to perform interactive analysis on-line without downloading any data. Several instances of the Giovanni-based interface have been or are being created to serve users of TRMM precipitation, MODIS aerosol, and SeaWiFS ocean color data, as well as agricultural applications users. Giovanni-based interfaces are simple to use but powerful. The user selects geophysical ,parameters, area of interest, and time period; and the system generates an output ,on screen in a matter of seconds.

Teng, William↗
NASA NTRS2006

Structure Detection of Nonlinear Aeroelastic Systems with Application to Aeroelastic Flight Test Data

This viewgraph presentation reviews the applicability of NARMAX structure detection to aeroelastic systems. In conclusion, the simulation results demonstrate bootstrap approach for structure computation of aircraft structural stiffness provided a high rate of true model selection: 1. T-test and stepwise regression methods had difficulty providing accurate results 2. Work contributes to understanding of the use of structure detection for modelling and identification of aerospace systems. 3. Limitation of model complexity that can be studied with these structure computation techniques 4. Result of the large number of candidate terms, for a given model order, and the data length required to guarantee convergence 5. Another approach to structure computation problem uses a least absolute shrinkage and selection operator (LASSO)

Kukreja, Sunil L.↗
NASA NTRS1972

ATS-5 solar cell experiment results after one year in synchronous orbit

The results of the ATS-5 solar cell experiment after one year in synchronous orbit are reported. A partial failure in the experimental electronics package has caused a loss of data from half the 80 experimental solar cells. Procedures for extracting data due to a partial spacecraft failure are described and discussed. Data from the remaining 40 solar cells, including 15 mounted on a thin flexible structure are analyzed. Data are corrected to a solar intensity of 140 mW/sq cm and a temperature of 25 C. It was found that after one year in synchronous orbit: (1) cells with 1.52-mm-thick coverslides did not show a clear-cut advantage over those with 0.15-mm coverslides, (2) cells with solderless grid lines are degrading at the same rate as are cells with solder-dipped grid lines, (3) cells not quite completely covered with coverslides suffered a large power loss in comparison to cells fully covered, (4) no clear-cut advantage of 10-cm cells over 2-cm cells has yet been observed, (5) cells mounted on the flexible panel with relatively little backshielding did not degrade any faster than those with substantial backshielding, and (6) the flight data in large part confirms the adequacy of the ground-based techniques used in our preflight radiation test program.

Anspaugh, B. E.↗
NASA NTRS1984

Fine-scale structure of the Jovian magnetotail current sheet

New evidence concerning the detailed structure of the magnetic field in and near the Jovian tail sheet is presented, and nonunique temporal variations in the sheet structure are deduced. Data from Voyagers 1 and 2 are used to show that the local sheet structure, while tending to vary with time and distance from Jupiter, generally corresponds to one of four general types. The four types are classified using examples, and possible geometries associated with each type are identified. The locations of the different types of sheet crossings are pointed out and discussed. The possibility of reconnection occurring at the current sheet is discussed through analogy with the terrestrial magnetotail. It is concluded that the results support the view that reconnection occurs in the Jovian magnetotail as a time-dependent, and possibly spatially localized, process.

Behannon, K. W.↗
NASA NTRS1991

ADDRAS - An integrated systems approach

NASA-Langley's Acoustics Division Data Reduction and Analysis System (ADDRAS) computes far-field noise spectral estimates on the basis of weather, aircraft state and position, and acoustic data sets. The structure and function of ADDRAS has been primarily determined by rotorcraft flyover test design, data acquisition, and data flow criteria. The RIM relational database management software is used to organize all noise test data for ADDRAS.

Becker, Lawrence E.↗
NASA NTRS1997

Identification of Rotorcraft Structural Dynamics from Flight and Wind Tunnel Data

Excessive vibration remains one one of the most difficult problems that faces the helicopter industry today, affecting all production helicopters at some phase of their development. Vibrations in rotating structures may arise from external periodic dynamic airloads whose frequencies are are close to the natural frequencies of the rotating system itself. The goal for the structures engineer would thus be to design a structure as free from resonance effects as possible. In the case of a helicopter rotor blade these dynamic loads are a consequence of asymmetric airload distribution on the rotor blade in forward flight, leading to a rich collection of higher harmonic airloads that force rotor and airframe response. Accurate prediction of the dynamic characteristics of a helicopter rotor blade will provide the opportunity to affect in a positive manner noise intensity, vibration level, durability, reliability and operating costs by reducing objectionable frequencies or moving them to a different frequency range and thus providing us with a lower vibration rotor. In fact, the dynamic characteristics tend to define the operating limits of a rotorcraft. As computing power has increased greatly over the last decade, researchers and engineers have turned to analyzing the vibrational characteristics of aerospace structures at the design and development stage of the production of an aircraft. Modern rotor blade construction methods lead to products with low mass and low inherent damping so careful design and analysis is required to avoid resonance and an undesirable dynamic performance. In addition, accurate modal analysis is necessary for several current approaches in elastic system identification and active control.

McKillip, Robert M., Jr.↗
NASA NTRS1999

Progressive Failure Analysis Methodology for Laminated Composite Structures

A progressive failure analysis method has been developed for predicting the failure of laminated composite structures under geometrically nonlinear deformations. The progressive failure analysis uses C(exp 1) shell elements based on classical lamination theory to calculate the in-plane stresses. Several failure criteria, including the maximum strain criterion, Hashin's criterion, and Christensen's criterion, are used to predict the failure mechanisms and several options are available to degrade the material properties after failures. The progressive failure analysis method is implemented in the COMET finite element analysis code and can predict the damage and response of laminated composite structures from initial loading to final failure. The different failure criteria and material degradation methods are compared and assessed by performing analyses of several laminated composite structures. Results from the progressive failure method indicate good correlation with the existing test data except in structural applications where interlaminar stresses are important which may cause failure mechanisms such as debonding or delaminations.

Sleight, David W.↗
NASA NTRS1939

Pressure Distribution on the Fuselage of a Midwing Airplane Model at High Speeds

The pressure distribution on the fuselage of a midwing airplane model was measured in the NACA 8-foot high speed wind tunnel at speeds from 140 to 440 miles per hour for lift coefficients ranging from -0.2 to 1.0. The primary purpose of the tests was to provide data showing the air pressures on various parts of the fuselage for use in structural design. The data may also be used for the design of scoops and vents. The results show that the highest negative pressures occurred near the wing and were more dependent on the wing than on the fuselage. At high speeds, the magnitude of the pressure coefficients as predicted from pressure coefficients determined experimentally at low speeds by application of the theoretical factor 1/(square root)1-M(exp 2) (where M is the ratio of the air speed to the speed of sound in air) may misrepresent the actual conditions. At the points where the maximum negative pressures ocurred, however, the variation of the pressure coefficients was in good agreement with the theoretical factor, indicating that this factor may afford satisfactory predictions of critical speed, at least for fuselages similar to the shape tested.

Delano, James B.↗