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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 NTRS2001

Multidisciplinary Design Optimization of a Full Vehicle with High Performance Computing

Multidisciplinary design optimization (MDO) of a full vehicle under the constraints of crashworthiness, NVH (Noise, Vibration and Harshness), durability, and other performance attributes is one of the imperative goals for automotive industry. However, it is often infeasible due to the lack of computational resources, robust simulation capabilities, and efficient optimization methodologies. This paper intends to move closer towards that goal by using parallel computers for the intensive computation and combining different approximations for dissimilar analyses in the MDO process. The MDO process presented in this paper is an extension of the previous work reported by Sobieski et al. In addition to the roof crush, two full vehicle crash modes are added: full frontal impact and 50% frontal offset crash. Instead of using an adaptive polynomial response surface method, this paper employs a DOE/RSM method for exploring the design space and constructing highly nonlinear crash functions. Two NMO strategies are used and results are compared. This paper demonstrates that with high performance computing, a conventionally intractable real world full vehicle multidisciplinary optimization problem considering all performance attributes with large number of design variables become feasible.

Yang, R. J.↗
NASA NTRS1992

Computational simulation of probabilistic lifetime strength for aerospace materials subjected to high temperature, mechanical fatigue, creep, and thermal fatigue

The results of a fourth year effort of a research program conducted for NASA-LeRC by The University of Texas at San Antonio (UTSA) are presented. The research included on-going development of methodology that provides probabilistic lifetime strength of aerospace materials via computational simulation. A probabilistic material strength degradation model, in the form of a randomized multifactor interaction equation, is postulated for strength degradation of structural components of aerospace propulsion systems subjected to a number of effects or primitive variables. These primitive variables may include high temperature, fatigue, or creep. In most cases, strength is reduced as a result of the action of a variable. This multifactor interaction strength degradation equation was randomized and is included in the computer program, PROMISC. Also included in the research is the development of methodology to calibrate the above-described constitutive equation using actual experimental materials data together with regression analysis of that data, thereby predicting values for the empirical material constants for each effect or primitive variable. This regression methodology is included in the computer program, PROMISC. Actual experimental materials data were obtained from industry and the open literature for materials typically for applications in aerospace propulsion system components. Material data for Inconel 718 was analyzed using the developed methodology.

Boyce, Lola↗
NASA NTRS2000

Cascade Optimization Strategy with Neural Network and Regression Approximations Demonstrated on a Preliminary Aircraft Engine Design

A preliminary aircraft engine design methodology is being developed that utilizes a cascade optimization strategy together with neural network and regression approximation methods. The cascade strategy employs different optimization algorithms in a specified sequence. The neural network and regression methods are used to approximate solutions obtained from the NASA Engine Performance Program (NEPP), which implements engine thermodynamic cycle and performance analysis models. The new methodology is proving to be more robust and computationally efficient than the conventional optimization approach of using a single optimization algorithm with direct reanalysis. The methodology has been demonstrated on a preliminary design problem for a novel subsonic turbofan engine concept that incorporates a wave rotor as a cycle-topping device. Computations of maximum thrust were obtained for a specific design point in the engine mission profile. The results (depicted in the figure) show a significant improvement in the maximum thrust obtained using the new methodology in comparison to benchmark solutions obtained using NEPP in a manual design mode.

Hopkins, Dale A.↗
NASA NTRS1976

Payload/orbiter contamination control requirement study

The Spacelab carrier induced contaminant environment and Spacelab's ability to meet established contamination control criteria for the shuttle program are determined. The primary areas of on-going activity include updating, refining, and improving the Spacelab Contamination Computer Model and contamination analysis methodology; establishing the resulting adjusted induced environment predictions for comparison with the applicable criteria; determining Spacelab design and operational requirements necessary to meet the criteria; conducting mission feasibility analyses of the combined Spacelab/orbiter contaminant environment for specific proposed missions and payload mixes; and establishing a preliminary Spacelab mission support plan and model interface requirements. A summary is given of these activities conducted to date including any modifications in approach or methodology utilized in the contamination assessment of the Spacelab vehicle. The emphasis is placed on the Spacelab modeling efforts.

Bareiss, L. E.↗
NASA NTRS1976

The calculation of steady non-linear transonic flow over finite wings with linear theory aerodynamics

The feasibility of calculating steady mean flow solutions for nonlinear transonic flow over finite wings with a linear theory aerodynamic computer program is studied. The methodology is based on independent solutions for upper and lower surface pressures that are coupled through the external flow fields. Two approaches for coupling the solutions are investigated which include the diaphragm and the edge singularity method. The final method is a combination of both where a line source along the wing leading edge is used to account for blunt nose airfoil effects; and the upper and lower surface flow fields are coupled through a diaphragm in the plane of the wing. An iterative solution is used to arrive at the nonuniform flow solution for both nonlifting and lifting cases. Final results for a swept tapered wing in subcritical flow show that the method converges in three iterations and gives excellent agreement with experiment at alpha = 0 deg and 2 deg. Recommendations are made for development of a procedure for routine application.

Cunningham, A. M., Jr.↗
NASA NTRS1976

Payload/orbiter contamination control requirement study: Spacelab configuration contamination study

The assessment of the Spacelab carrier induced contaminant environment was continued, and the ability of Spacelab to meet established contamination control criteria for the space transportation system program was determined. The primary areas considered included: (1) updating, refining, and improving the Spacelab contamination computer model and contamination analysis methodology, (2) establishing the resulting adjusted induced environment predictions for comparison with the applicable criteria, (3) determining the Spacelab design and operational requirements necessary to meet the criteria, (4) conducting mission feasibility analyses of the combined Spacelab/Orbiter contaminant environment for specific proposed mission and payload mixes, and (5) establishing a preliminary Spacelab mission support plan as well as model interface requirements; A summary of those activities conducted to date with respect to the modelling, analysis, and predictions of the induced environment, including any modifications in approach or methodology utilized in the contamination assessment of the Spacelab carrier, was presented.

Bareiss, L. E.↗
NASA NTRS1979

Supercritical flow about a thick circular-arc airfoil

The supercritical flow about a biconvex circular-arc airfoil is being thoroughly documented at Ames Research Center in order to provide experimental test cases suitable for guiding and evaluating current and future computer codes. The effects of angle of attack, effects of leading and trailing-edge splitter plates, additional unsteady pressure fluctuation (buffeting) measurements and glow-field shadowgraphs, and application of an oil-film technique to display separated-wake streamlines were studied. Computed and measured pressure distributions for steady and unsteady flows, using a recent computer code representative of current methodology, are compared. It was found that the numerical solutions are often fundamentally incorrect in that only strong (shock-polar terminology) shocks are captured, whereas experimentally, both strong and weak shock waves appear.

Mcdevitt, J. B.↗
NASA NTRS1981

Remote sensing applied to agriculture: Basic principles, methodology, and applications

The general principles of remote sensing techniques as applied to agriculture and the methods of data analysis are described. the theoretical spectral responses of crops; reflectance, transmittance, and absorbtance of plants; interactions of plants and soils with reflectance energy; leaf morphology; and factors which affect the reflectance of vegetation cover are dicussed. The methodologies of visual and computer-aided analyses of LANDSAT data are presented. Finally, a case study wherein infrared film was used to detect crop anomalies and other data applications are described.

Dejesusparada, N.↗
NASA NTRS1985

Research and development activities in unified control-structure modeling and design

Results of work to develop a unified control/structures modeling and design capability for large space structures modeling are presented. Recent analytical results are presented to demonstrate the significant interdependence between structural and control properties. A new design methodology is suggested in which the structure, material properties, dynamic model and control design are all optimized simultaneously. Parallel research done by other researchers is reviewed. The development of a methodology for global design optimization is recommended as a long-term goal. It is suggested that this methodology should be incorporated into computer aided engineering programs, which eventually will be supplemented by an expert system to aid design optimization.

Nayak, A. P.↗
NASA NTRS1985

Research and development activities in unified control-structure modeling and design

Results of work sponsored by JPL and other organizations to develop a unified control/structures modeling and design capability for large space structures is presented. Recent analytical results are presented to demonstrate the significant interdependence between structural and control properties. A new design methodology is suggested in which the structure, material properties, dynamic model and control design are all optimized simultaneously. The development of a methodology for global design optimization is recommended as a long term goal. It is suggested that this methodology should be incorporated into computer aided engineering programs, which eventually will be supplemented by an expert system to aid design optimization. Recommendations are also presented for near term research activities at JPL. The key recommendation is to continue the development of integrated dynamic modeling/control design techniques, with special attention given to the development of structural models specially tailored to support design.

Nayak, A. P.↗
NASA NTRS1985

Fault-free behavior of reliable multiprocessor systems: FTMP experiments in AIRLAB

This report describes a set of experiments which were implemented on the Fault tolerant Multi-Processor (FTMP) at NASA/Langley's AIRLAB facility. These experiments are part of an effort to formulate and evaluate validation methodologies for fault-tolerant computers. This report deals with the measurement of single parameters (baselines) of a fault free system. The initial set of baseline experiments lead to the following conclusions: (1) The system clock is constant and independent of workload in the tested cases; (2) the instruction execution times are constant; (3) the R4 frame size is 40mS with some variation; (4) the frame stretching mechanism has some flaws in its implementation that allow the possibility of an infinite stretching of frame duration. Future experiments are planned. Some will broaden the results of these initial experiments. Others will measure the system more dynamically. The implementation of a synthetic workload generation mechanism for FTMP is planned to enhance the experimental environment of the system.

Clune, E.↗
NASA NTRS1986

Streamlining shuttle ground operations

To meet NASA Space Transportation System goals the Shuttle Processing Contractors have to reduce Space Transportation System ground processing time and ground processing costs. These objectives must be met without compromising safety of flight or safety during assembly, test, and service operations. Ground processing requirements are analyzed to determine critical serial flow paths and costly labor-intensive tasks. Processing improvements are realized by improvements in processing methodology, by application of computer-aided technology, and by modernization of KSC facilities. Ongoing improvement efforts are outlined and progress-to-date is described.

Heimbold, R. L.↗
NASA NTRS1989

Testing of reliability - Analysis tools

An outline is presented of issues raised in verifying the accuracy of reliability analysis tools. State-of-the-art reliability analysis tools implement various decomposition, aggregation, and estimation techniques to compute the reliability of a diversity of complex fault-tolerant computer systems. However, no formal methodology has been formulated for validating the reliability estimates produced by these tools. The author presents three states of testing that can be performed on most reliability analysis tools to effectively increase confidence in a tool. These testing stages were applied to the SURE (semi-Markov Unreliability Range Evaluator) reliability analysis tool, and the results of the testing are discussed.

Hayhurst, Kelly J.↗
NASA NTRS1989

The application of ab initio calculations to molecular spectroscopy

The state of the art in ab initio molecular structure calculations is reviewed with an emphasis on recent developments, such as full configuration-interaction benchmark calculations and atomic natural orbital basis sets. It is found that new developments in methodology, combined with improvements in computer hardware, are leading to unprecedented accuracy in solving problems in spectroscopy.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1989

The application of ab initio calculations to molecular spectroscopy

The state of the art in ab initio molecular structure calculations is reviewed, with an emphasis on recent developments such as full configuration-interaction benchmark calculations and atomic natural orbital basis sets. It is shown that new developments in methodology combined with improvements in computer hardware are leading to unprecedented accuracy in solving problems in spectroscopy.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1991

CHIMES-2: A tool for automated HCI analysis

The topics are presented in view graph form and include the following: Computer Human Interaction Models (CHIMES) methodology; the CHIMES-2 prototype; and CHIMES future development.

Weiland, William J.↗
NASA NTRS1993

Probabilistic sizing of laminates with uncertainties

A reliability based design methodology for laminate sizing and configuration for a special case of composite structures is described. The methodology combines probabilistic composite mechanics with probabilistic structural analysis. The uncertainties of constituent materials (fiber and matrix) to predict macroscopic behavior are simulated using probabilistic theory. Uncertainties in the degradation of composite material properties are included in this design methodology. A multi-factor interaction equation is used to evaluate load and environment dependent degradation of the composite material properties at the micromechanics level. The methodology is integrated into a computer code IPACS (Integrated Probabilistic Assessment of Composite Structures). Versatility of this design approach is demonstrated by performing a multi-level probabilistic analysis to size the laminates for design structural reliability of random type structures. The results show that laminate configurations can be selected to improve the structural reliability from three failures in 1000, to no failures in one million. Results also show that the laminates with the highest reliability are the least sensitive to the loading conditions.

Shah, A. R.↗
NASA NTRS1992

Probabilistic evaluation of uncertainties and risks in aerospace components

A methodology is presented for the computational simulation of primitive variable uncertainties, and attention is given to the simulation of specific aerospace components. Specific examples treated encompass a probabilistic material behavior model, as well as static, dynamic, and fatigue/damage analyses of a turbine blade in a mistuned bladed rotor in the SSME turbopumps. An account is given of the use of the NESSES probabilistic FEM analysis CFD code.

Shah, A. R.↗