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Results for “design, synthesis and processing”

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 145 records · Page 8

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NASA NTRS1974

Synthesis of stiffened shells of revolution

Computer programs for the synthesis of shells of various configurations were developed. The conditions considered are: (1) uniform shells (mainly cones) using a membrane buckling analysis, (2) completely uniform shells (cones, spheres, toroidal segments) using linear bending prebuckling analysis, and (3) revision of second design process to reduce the number of design variables to about 30 by considering piecewise uniform designs. A perturbation formula was derived and this allows exact derivatives of the general buckling load to be computed with little additional computer time.

Thornton, W. A.↗

NASA NTRS1987

Imaging and data processing with the Low Frequency Space Array

The Low Frequency Space Array (LFSA) is being designed to image the entire sky at extremely low radio frequencies with arcmin to subarcmin resolution. To accomplish this goal, data from LFSA will be continuously integrated for many months and then be used with aperture synthesis techniques to produce images. The three dimensional nature of LFSA and the effects of orbital geometry make LFSA a continuously evolving array which has an excellent synthesized point-response function. After transforming the data to produce an initial image, it is possible to remove low-level sidelobe responses remaining in the image and thereby produce a high dynamic-range image. Interference (both man-made and from solar-system objects) is a potential problem for LFSA, but appropriate data handling techniques are available which should eliminate any of its effects.

Simon, R. S.↗

NASA NTRS1990

Composite laminate tailoring with probabilistic constraints and loads

A reliability-based structural synthesis procedure was developed to tailor laminates to meet reliability-based (ply) strength requirements and achieve desirable laminate responses. The main thrust is to demonstrate how to integrate the optimization technique in the composite laminate tailoring process to meet reliability design requirements. The question of reliability arises in fiber composite analysis and design because of the inherent scatter that is observed in the constituent (fiber and matrix) material properties during experimentation. Symmetric and asymmetric composite laminates subject to mechanical loadings are considered as application examples. These application examples illustrate the effectiveness and ease with which reliability considerations can be integrated in the design optimization model for composite laminate tailoring.

Thanedar, P. B.↗

NASA NTRS1990

Composite laminate tailoring with probabilistic constraints and loads

Thanedar, P. B.↗

NASA NTRS1994

Program Aids Analysis And Optimization Of Design

NETS/ PROSSS (NETS Coupled With Programming System for Structural Synthesis) computer program developed to provide system for combining NETS (MSC-21588), neural-network application program and CONMIN (Constrained Function Minimization, ARC-10836), optimization program. Enables user to reach nearly optimal design. Design then used as starting point in normal optimization process, possibly enabling user to converge to optimal solution in significantly fewer iterations. NEWT/PROSSS written in C language and FORTRAN 77.

Rogers, James L., Jr.↗

NASA NTRS1982

Effect of processing on Polymer/Composite structure and properties

Advances in the vitality and economic health of the field of polymer forecasting are discussed. A consistent and rational point of view which considers processing as a participant in the underlying triad of relationships which comprise materials science and engineering is outlined. This triad includes processing as it influences material structure, and ultimately properties. Methods in processing structure properties, polymer science and engineering, polymer chemistry and synthesis, structure and modification and optimization through processing, and methods of melt flow modeling in processing structure property relations of polymer were developed. Mechanical properties of composites are considered, and biomedical materials research to include polymer processing effects are studied. An analysis of the design technology of advances graphite/epoxy composites is also reported.

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NASA NTRS2002

Bi-Level Integrated System Synthesis (BLISS) for Concurrent and Distributed Processing

The paper introduces a new version of the Bi-Level Integrated System Synthesis (BLISS) methods intended for optimization of engineering systems conducted by distributed specialty groups working concurrently and using a multiprocessor computing environment. The method decomposes the overall optimization task into subtasks associated with disciplines or subsystems where the local design variables are numerous and a single, system-level optimization whose design variables are relatively few. The subtasks are fully autonomous as to their inner operations and decision making. Their purpose is to eliminate the local design variables and generate a wide spectrum of feasible designs whose behavior is represented by Response Surfaces to be accessed by a system-level optimization. It is shown that, if the problem is convex, the solution of the decomposed problem is the same as that obtained without decomposition. A simplified example of an aircraft design shows the method working as intended. The paper includes a discussion of the method merits and demerits and recommendations for further research.

Sobieszczanski-Sobieski, Jaroslaw↗

NASA NTRS2006

Free Fall Plasma-Arc Reactor for Synthesis of Carbon Nanotubes in Microgravity

High temperatures inside the plasma of a carbon arc generate strong buoyancy driven convection which has an effect on the growth and morphology of the single-walled carbon nanotubes (SWNTs). To study the effect of buoyancy on the arc process, a miniature carbon arc apparatus was designed and developed to synthesize SWNTs in a microgravity environment substantially free from buoyant convective flows. An arc reactor was operated in the 2.2- and 5.18-second drop towers at the NASA Glenn Research Center. The apparatus employed a 4 mm diameter anode and was powered by a portable battery pack capable of providing in excess of 300 amps at 30 volts to the arc for the duration of a 5-second drop. However, the principal result is that no dramatic difference in sample yield or composition was noted between normal gravity, 2.2-and 5-second long microgravity runs.

Alford, J. M.↗

NASA NTRS1976

Analytical display design for flight tasks conducted under instrument meteorological conditions

Paramount to proper utilization of electronic displays is a method for determining pilot-centered display requirements. Display design should be viewed fundamentally as a guidance and control problem which has interactions with the designer's knowledge of human psychomotor activity. From this standpoint, reliable analytical models of human pilots as information processors and controllers can provide valuable insight into the display design process. A relatively straightforward, nearly algorithmic procedure for deriving model-based, pilot-centered display requirements was developed and is presented. The optimal or control theoretic pilot model serves as the backbone of the design methodology, which is specifically directed toward the synthesis of head-down, electronic, cockpit display formats. Some novel applications of the optimal pilot model are discussed. An analytical design example is offered which defines a format for the electronic display to be used in a UH-1H helicopter in a landing approach task involving longitudinal and lateral degrees of freedom.

Hess, R. A.↗

NASA NTRS1987

An Application of Retroduction to Analyzing and Testing the Backing off of Nuts and Bolts During Dynamic Loading

The method of retroduction, adapted from the doctoral thesis of Dr. A. Croce, relies on a process of dialectic questioning that begins with the information sought, proceeds to Given items (either in the form of dimensions or limits of research). and to Known mathematical forms of analysis in design or to principles of study in research. Finally, analysis and synthesis are used to abstract the dielectic questions and to arrive at the information desired. This method is used to solve the engineering design problem of a beam and to determine why bolts and nuts vibrate apart. Both mathematical analysis and dialectic logical analysis are utilized. Results are provided of tests conducted to check the retroductive study of why and how nuts back off.

Kerley, James J.↗

NASA NTRS1990

Application of global sensitivity equations in multidisciplinary aircraft synthesis

The present paper investigates the applicability of the Global Sensitivity Equation (GSE) method in the multidisciplinary synthesis of aeronautical vehicles. The GSE method provides an efficient approach for representing a large coupled system by smaller subsystems and accounts for the subsystem interactions by means of first-order behavior sensitivities. This approach was applied in an aircraft synthesis problem with performance constraints stemming from the disciplines of structures, aerodynamics, and flight mechanics. Approximation methods were considered in an attempt to reduce problem dimensionality and to improve the efficiency of the optimization process. The influence of efficient constraint representations, the choice of design variables, and design variable scaling on the conditioning of the system matrix was also investigated.

Hajela, P.↗

NASA NTRS1973

Development of weight/sizing design synthesis computer program. Volume 3: User Manual

The user manual for the weight/sizing design synthesis program is presented. The program is applied to an analysis of the basic weight relationships for the space shuttle which contribute significant portions of the inert weight. The relationships measure the parameters of load, geometry, material, and environment. A verbal description of the processes simulated, data input procedures, output data, and values present in the program is included.

Garrison, J. M.↗

NASA NTRS1973

Space processes for extended low-G testing

Results of an investigation of verifying the capabilities of space processes in ground based experiments at low-g periods are presented. Limited time experiments were conducted with the processes. A valid representation of the complete process cycle was achieved at low-g periods ranging from 40 to 390 seconds. A minimum equipment inventory, is defined. A modular equipment design, adopted to assure low cost and high program flexibility, is presented as well as procedures and data established for the synthesis and definition of dedicated and mixed rocket payloads.

Steurer, W. H.↗

NASA NTRS1974

Preliminary performance estimates of an oblique, all-wing, remotely piloted vehicle for air-to-air combat

A computerized aircraft synthesis program has been used to assess the effects of various vehicle and mission parameters on the performance of an oblique, all-wing, remotely piloted vehicle (RPV) for the highly maneuverable, air-to-air combat role. The study mission consists of an outbound cruise, an acceleration phase, a series of subsonic and supersonic turns, and a return cruise. The results are presented in terms of both the required vehicle weight to accomplish this mission and the combat effectiveness as measured by turning and acceleration capability. This report describes the synthesis program, the mission, the vehicle, and results from sensitivity studies. An optimization process has been used to establish the nominal RPV configuration of the oblique, all-wing concept for the specified mission. In comparison to a previously studied conventional wing-body canard design for the same mission, this oblique, all-wing nominal vehicle is lighter in weight and has higher performance.

Nelms, W. P., Jr.↗

NASA NTRS1993

Two-Stage Reduction Of Dynamical Models

No longer necessary to solve eigenvalue problems of high order. Component-mode projection-and-assembly model-reduction (COMPARE) method provides approximation of dynamics of vibrations of complicated, multiple flexible bodies by use of mathematical models of reduced order. Incorporates component-mode synthesis (CMS) method and enhanced projection-and-assembly (EP&A) method, described in "Enhanced Method of Reduction of Dynamical Models" (NPO-18402), providing for somewhat simplified two-stage process in which order of applicable mathematical models reduced. Reduced-order models used to design algorithms of control systems to suppress vibrations or otherwise control structure.

Lee, Allan Y.↗

NASA NTRS1989

A 'figure-of-merit' approach to extraterrestrial resource utilization

An approach for interrelated optimizations in space missions that utilize extraterrestrial resources is developed, consisting in the concept of an overall mission 'figure-of-merit' leading to more realistic designs than through individual performance maximizations. After a brief discussion of this concept, the synthesis of four major components of any future space mission is considered. The four major components are: orbital mechanics of the transportation; performance of the rocket motors; support systems including power, thermal and process controls, and instruments; and in situ resource utilization plant equipment. The Mars Sample Return mission is the basis of an illustration of the proposed concept. A popular spreadsheet is used to quantitatively demonstrate the interdependent nature of the mission optimization. Future prospects are outlined, that promise great economy through extraterrestrial resource utilization and a quick evaluation technique.

Ramohalli, Kumar↗

NASA NTRS1986

Optimal airframe synthesis for gust loads

An optimization capability for sizing airframe structures that are subjected to a combination of deterministic and random flight loads was established. The random vibration environment introduces the need for selecting a statistical process that best describes the random loads and permits computation of the dynamic response parameters of interest. Furthermore, it requires a formulation of design constraints that would minimize the conservativeness in the design and retain computational viability. The random loads are treated as a stationary, homogeneous process with a Gaussian probability distribution. The formulation of the analysis problem, the structure of the optimization programming system and a representative numerical example are discussed.

Hajela, P.↗

NASA NTRS1987

Controller synthesis for flexible spacecraft using multivariable loop-shaping and factorization methods

The problem of designing fine-pointing controllers is considered for large, flexible space structures using modern multivariable synthesis methods. The first method is an iterative procedure which utilizes frequency-domain singular-value techniques, and is found to yield satisfactory performance and robustness. For the second method, which is based on coprime factorizations, a particular bicoprime is obtained, and the steps in the design process are described. This method is still under development.

Joshi, Suresh M.↗