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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Results of an integrated structure-control law design sensitivity analysis

Next generation air and space vehicle designs are driven by increased performance requirements, demanding a high level of design integration between traditionally separate design disciplines. Interdisciplinary analysis capabilities have been developed, for aeroservoelastic aircraft and large flexible spacecraft control for instance, but the requisite integrated design methods are only beginning to be developed. One integrated design method which has received attention is based on hierarchal problem decompositions, optimization, and design sensitivity analyses. This paper highlights a design sensitivity analysis method for Linear Quadratic Cost, Gaussian (LQG) optimal control laws, which predicts change in the optimal control law due to changes in fixed problem parameters using analytical sensitivity equations. Numerical results of a design sensitivity analysis for a realistic aeroservoelastic aircraft example are presented. In this example, the sensitivity of the optimally controlled aircraft's response to various problem formulation and physical aircraft parameters is determined. These results are used to predict the aircraft's new optimally controlled response if the parameter was to have some other nominal value during the control law design process. The sensitivity results are validated by recomputing the optimal control law for discrete variations in parameters, computing the new actual aircraft response, and comparing with the predicted response. These results show an improvement in sensitivity accuracy for integrated design purposes over methods which do not include changess in the optimal control law. Use of the analytical LQG sensitivity expressions is also shown to be more efficient that finite difference methods for the computation of the equivalent sensitivity information.

Gilbert, Michael G.↗
NASA NTRS1987

Component specific modeling

The objective was to develop and verify a series of interdisciplinary modeling and analysis techniques specialized to address hot section components. These techniques incorporate data as well as theoretical methods from many diverse areas, including cycle and performance analysis, heat transfer analysis, linear and nonlinear stress analysis, and mission analysis.

Mcknight, R. L.↗
NASA NTRS1988

Mars rover sample return: An exobiology science scenario

A mission designed to collect and return samples from Mars will provide information regarding its composition, history, and evolution. At the same time, a sample return mission generates a technical challenge. Sophisticated, semi-autonomous, robotic spacecraft systems must be developed in order to carry out complex operations at the surface of a very distant planet. An interdisciplinary effort was conducted to consider how much a Mars mission can be realistically structured to maximize the planetary science return. The focus was to concentrate on a particular set of scientific objectives (exobiology), to determine the instrumentation and analyses required to search for biological signatures, and to evaluate what analyses and decision making can be effectively performed by the rover in order to minimize the overhead of constant communication between Mars and the Earth. Investigations were also begun in the area of machine vision to determine whether layered sedimentary structures can be recognized autonomously, and preliminary results are encouraging.

Rosenthal, D. A.↗
NASA NTRS1989

An initiative in multidisciplinary optimization of rotorcraft

Described is a joint NASA/Army initiative at the Langley Research Center to develop optimization procedures aimed at improving the rotor blade design process by integrating appropriate disciplines and accounting for important interactions among the disciplines. The activity is being guided by a Steering Committee made up of key NASA and Army researchers and managers. The committee, which has been named IRASC (Integrated Rotorcraft Analysis Steering Committee), has defined two principal foci for the activity: a white paper which sets forth the goals and plans of the effort; and a rotor design project which will validate the basic constituents, as well as the overall design methodology for multidisciplinary optimization. The optimization formulation is described in terms of the objective function, design variables, and constraints. Additionally, some of the analysis aspects are discussed and an initial attempt at defining the interdisciplinary couplings is summarized. At this writing, some significant progress has been made, principally in the areas of single discipline optimization. Results are given which represent accomplishments in rotor aerodynamic performance optimization for minimum hover horsepower, rotor dynamic optimization for vibration reduction, and rotor structural optimization for minimum weight.

Adelman, Howard M.↗
NASA NTRS1989

Optimization of rotor blades for combined structural, performance, and aeroelastic characteristics

The strategies whereby helicopter rotor blades can be optimized for combined structural, inertial, dynamic, aeroelastic, and aerodynamic performance characteristics are outlined. There are three key ingredients in the successful execution of such an interdisciplinary optimization. The first is the definition of a satisfactory performance index that combines all aspects of the problem without too many constraints. The second element is the judicious choice of computationally efficient analysis tools for the various quantitative components in both the cost functional and constraints. The third element is an effective strategy for combining the various disciplines either in parallel or sequential optimizations.

Peters, David A.↗
NASA NTRS1989

An interpretation and solution of ill-conditioned linear equations

Data insufficiency, poorly conditioned matrices and singularities in equations occur regularly in complex optimization, correlation, and interdisciplinary model studies. This work concerns itself with two methods of obtaining certain physically realistic solutions to ill-conditioned or singular algebraic systems of linear equations arising from such studies. Two efficient computational solution procedures that generally lead to locally unique solutions are presented when there is insufficient data to completely define the model, or a least-squares error formulation of this system results in an ill-conditioned system of equations. If it is assumed that a reasonable estimate of the uncertain data is available in both cases cited above, then we shall show how to obtain realistic solutions efficiently, in spite of the insufficiency of independent data. The proposed methods of solution are more efficient than singular-value decomposition for dealing with such systems, since they do not require solutions for all the non-zero eigenvalues of the coefficient matrix.

Ojalvo, I. U.↗
NASA NTRS1989

An analytical sensitivity method for use in integrated aeroservoelastic aircraft design

Interdisciplinary analysis capabilities have been developed for aeroservoelastic aircraft and large flexible spacecraft, but the requisite integrated design methods are only beginning to be developed. One integrated design method which has received attention is based on hierarchal problem decompositions, optimization, and design sensitivity analyses. This paper highlights a design sensitivity analysis method for Linear Quadratic Gaussian (LQG) optimal control laws, enabling the use of LQG techniques in the hierarchal design methodology. The LQG sensitivity analysis method calculates the change in the optimal control law and resulting controlled system responses due to changes in fixed design integration parameters using analytical sensitivity equations. Numerical results of a LQG design sensitivity analysis for a realistic aeroservoelastic aircraft example are presented. In this example, the sensitivity of the optimal control law and aircraft response for various parameters such as wing bending natural frequency is determined. The sensitivity results computed from the analytical expressions are used to estimate changes in response resulting from changes in the parameters. Comparisons of the estimates with exact calculated responses show they are reasonably accurate for + or - 15 percent changes in the parameters. Evaluation of the analytical expressions is computationally faster than equivalent finite difference calculations.

Gilbert, Michael G.↗
NASA NTRS1988

Calibration support for the Earth Observing System Project

The Earth Observing System Project (EOS) program guidelines establishes significantly more stringent requirements on calibrations of instruments. This requirement is driven by the need for long-term continuity of acquired data sets and the use of measurements in interdisciplinary investigations. Personnel from the Standards and Calibration Office have been supporting the Program and Project in interpreting these goals into specific requirements. Contributions to EOS have included participation in the Panel of Experts which produced a list of consensus items necessary for accomplishing an accurate calibration and suggested EOS Project Calibration Policy, and drafting the announcement of opportunity and bidders information package positions on instrument calibration and data product validation. Technical staffing was provided to the NASA delegates to the Committee on Earth Orbiting Satellites (club of space-faring nations) for the standing working group on Calibration and Data Validation.

Guenther, B. W.↗
NASA NTRS1988

A satellite data processing and analysis software system for earth's atmosphere and surface research

The OASIS (Oceanic and Atmospheric Satellite Imaging System) is a satellite data processing and analysis software system being developed by the California Space Institute (Cal Space) for support of interdisciplinary and integrated earth sciences research programs. The system's software applications are integrated under a common executive, NASA's Transportable Application Executive (TAE). In this paper, TAE and the system software and hardware are described, and specific techniques used for ingesting, processing, analyzing, and graphically displaying data from many of the sensors presently being flown are presented. Scientific uses of these capabilities that are, or will shortly be, running under TAE at Cal Space are described.

Dealy, B.↗
NASA NTRS1988

Application of integrated fluid-thermal structural analysis methods

Hypersonic vehicles operate in a hostile aerothermal environment which has a significant impact on their aerothermostructural performance. Significant coupling occurs between the aerodynamic flow field, structural heat transfer, and structural response creating a multidisciplinary interaction. Interfacing state-of-the-art disciplinary analysis methods are not efficient, hence interdisciplinary analysis methods integrated into a single aerothermostructural analyzer are needed. The NASA Langley Research Center is developing such methods in an analyzer called LIFTS (Langley Integrated Fluid-Thermal-Structural) analyzer. The evolution and status of LIFTS is reviewed and illustrated through applications.

Wieting, Allan R.↗
NASA NTRS1989

Technology for monitoring global change

Multiinstrumented earth-science platforms currently being planned for both LEO and GEO positions will furnish data for the compilation of systematic and intercorrelated information that is suitable for the treatment of interdisciplinary questions concerning atmospheric, oceanic, hydrological, geological, and biological changes of an either natural or anthropogenic nature. Attention will be given in these observational campaigns to such essential earth variables as atmospheric pressure, rainfall/snowfall, vegetation cover, soil nutrient cycles, sea surface temperatures, ocean circulation, and ocean biological productivity.

Johnston, Gordon I.↗
NASA NTRS1989

A new unified architecture of thermal/structural dynamic algorithms - Applications to coupled thermoelasticity

A new unified architecture of robust thermal-structural dynamic algorithms is presented with emphasis on applications to coupled thermoelasticity. The proposed formulations are based on Lax-Wendroff/Taylor-Galerkin explicit time integration methodology. The applicability of the proposed unified architecture to interdisciplinary problems relevant to coupled dynamic thermoelasticity is demonstrated. The basic concepts and characteristic features of the unified formulations are discussed.

Tamma, Kumar K.↗
NASA NTRS1989

An automated, integrated approach to Space Station structural modeling

NASA and its contractors have developed an integrated, interdisciplinary CAD/analysis system designated IDEAS(double asterisk)2 in order to conduct evaluations of alternative Space Station concepts' performance over the projected course of the Station's evolution in orbit. Attention is presently given to the requirements associated with automated FEM-building methods applicable to Space Station system-level structural dynamic analysis, and the ways in which IDEAS(double asterisk)2 addresses these requirements. Advantage is taken of the interactive capabilities of the SUPERTAB FEM preprocessor system for Space Station model manipulation and modification.

Lindenmoyer, Alan J.↗
NASA NTRS1989

Integrated multidisciplinary design optimization of rotorcraft

The NASA/Army research plan for developing the logic elements for helicopter rotor design optimization by integrating appropriate disciplines and accounting for important interactions among the disciplines is discussed. The paper describes the optimization formulation in terms of the objective function, design variables, and constraints. The analysis aspects are discussed, and an initial effort at defining the interdisciplinary coupling is summarized. Results are presented on the achievements made in the rotor aerodynamic performance optimization for minimum hover horsepower, rotor dynamic optimization for vibration reduction, rotor structural optimization for minimum weight, and integrated aerodynamic load/dynamics optimization for minimum vibration and weight.

Adelman, Howard M.↗
NASA NTRS1989

Scientific computing challenges arising from space-borne observations

Five supercomputing problems are described: (1) determining the motions of the earth's inner core boundary from outer-space measurements of the magnetic field, (2) simulating the global dynamics of the earth's ocean currents, sea-ice cycles, land surface biology, and interannual atmospheric climates, (3) upper atmospheric chemistry, (4) modeling solar flare eruptions, and (5) the role of jet processes in the birth of stars. In addition, two examples indicating the growing importance of the use of supercomputers for scientific visualization are presented. The first deals with remote mapping from space of the earth's topography or other planets. The second problem from astrophysics deals with mapping the cosmic background radiation in the presence of other astronomical signatures. A brief overview of interdisciplinary modeling plans under development for the next generation of supercomputers is given.

Halem, Milton↗
NASA NTRS1989

NASA'S controls-structures interaction program

A NASA program is about to start which has the objective to advance Controls-Structures Interaction (CSI) technology to a point where it can be used in spacecraft design for future missions. Because of the close interrelationships between the structure, the control hardware, and the analysis/design, a highly interdisciplinary activity is defined in which structures, dynamics, controls, computer and electronics engineers work together on a daily basis and are co-located to a large extent. Methods will be developed which allow the controls and structures analysis and design functions to use the same mathematical models. Hardware tests and applications are emphasized and will require development of concepts and test methods to carry out. Because of a variety of mission application problem classes, several time-phased, focus ground test articles are planned. They will be located at the Langley Researdh Center (LaRC), the Marshall Space Flight Center (MSFC) and at the Jet Propulsion Laboratory (JPL). It is anticipated that the ground tests will be subject to gravity and other environmental effects to the extent that orbital flights tests will be needed for verification of some technology items. The need for orbital flight experiments will be quantified based on ground test results and mission needs. Candidate on-orbit experiments will be defined and preliminary design/definition and cost studies will be carried out for one or more high-priority experiments.

Hanks, Brantley R.↗
NASA NTRS1989

Integrated multidisciplinary design optimization of rotorcraft

The NASA/Army research plan for developing the logic elements for helicopter rotor design optimization by integrating appropriate disciplines and accounting for important interactions among the disciplines is discussed. The optimization formulation is described in terms of the objective function, design variables, and constraints. The analysis aspects are discussed, and an initial effort at defining the interdisciplinary coupling is summarized. Results are presented on the achievements made in the rotor dynamic optimization for vibration reduction, rotor structural optimization for minimum weight, and integrated aerodynamic load/dynamics optimization for minimum vibration and weight.

Adelman, Howard M.↗
NASA NTRS1989

Integrated multidisciplinary optimization of rotorcraft: A plan for development

This paper describes a joint NASA/Army initiative at the Langley Research Center to develop optimization procedures aimed at improving the rotor blade design process by integrating appropriate disciplines and accounting for important interactions among the disciplines. The paper describes the optimization formulation in terms of the objective function, design variables, and constraints. Additionally, some of the analysis aspects are discussed, validation strategies are described, and an initial attempt at defining the interdisciplinary couplings is summarized. At this writing, significant progress has been made, principally in the areas of single discipline optimization. Accomplishments are described in areas of rotor aerodynamic performance optimization for minimum hover horsepower, rotor dynamic optimization for vibration reduction, and rotor structural optimization for minimum weight.

Adelman, Howard M.↗