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At least 667 records · Page 37

All sources NASA NTRS DOE OSTI

NASA NTRS1985

Optimal cooperative control synthesis of active displays

The utility of augmenting displays to aid the human operator in controlling high order complex systems is well known. Analytical evaluations of various display designs for a simple k/s-squared plant in a compensatory tracking task using an Optimal Control Model (OCM) of human behavior is carried out. This analysis reveals that significant improvement in performance should be obtained by skillful integration of key information into the display dynamics. The cooperative control synthesis technique previously developed to design pilot-optimal control augmentation is extended to incorporate the simultaneous design of performance enhancing augmented displays. The application of the cooperative control synthesis technique to the design of augmented displays is discussed for the simple k/s-squared plant. This technique is intended to provide a systematic approach to design optimally augmented displays tailored for specific tasks.

Garg, S.↗

NASA NTRS1986

Low-Concentration-Ratio Solar-Cell Arrays

Paper presents design concept for mass-producible arrays of solar electric batteries and concentrators tailored to individual requirements. Arrays intended primarily for space stations needing about 100 kW of power. However, modular, lightweight, compact, and relatively low-cost design also fulfill requirements of some terrestrial applications. Arrays built with currently available materials. Pultrusions, injectionmolded parts, and composite materials used extensively to keep weight low. For added flexibility in design and construction, silicon and gallium arsenide solar-cell panels interchangeable.

Biss, M. S.↗

NASA NTRS1983

NASA LeRC/Akron University Graduate Cooperative Fellowship Program and Graduate Student Researchers Program

On June 1, 1980, the University of Akron and the NASA Lewis Research Center (LERC) established a Graduate Cooperative Fellowship Program in the specialized areas of Engine Structural Analysis and Dynamics, Computational Mechanics, Mechanics of Composite Materials, and Structural Optimization, in order to promote and develop requisite technologies in these areas of engine technology. The objectives of this program are consistent with those of the NASA Engine Structure Program in which graduate students of the University of Akron participate by conducting research at Lewis. This report is the second on this grant and summarizes the second and third year research effort, which includes the participation of five graduate students where each student selects one of the above areas as his special field of interest. Each student is required to spend 30 percent of his educational training time at the NASA Lewis Research Center and the balance at the University of Akron. His course work is judiciously selected and tailored to prepare him for research work in his field of interest. A research topic is selected for each student while in residence at the NASA Lewis Research Center, which is also approved by the faculty of the University of Akron as his thesis topic for a Master's and/or a Ph.D. degree.

Fertis, D. G.↗

NASA NTRS1985

Space shuttle descent design: From development to operations

The descent guidance system, the descent trajectories design, and generating of the associated flight products are discussed. The programs which allow the successful transitions from development to STS operations, resulting in reduced manpower requirements and compressed schedules for flight design cycles are addressed. The topics include: (1) continually upgraded tools for the job, i.e., consolidating tools via electronic data transfers, tailoring general purpose software for needs, easy access to tools through an interactive approach, and appropriate flexibility to allow design changes and provide growth capability; (2) stabilizing the flight profile designs (I-loads) in an uncertain environment; and (3) standardizing external interfaces within performance and subsystems constraints of the Orbiter.

Crull, T. J.↗

NASA NTRS1985

Parametric study of the aeroelastic stability of a bearingless rotor

A trade study was conducted to illustrate the sensitivity of the aeroelastic stability of a bearingless main rotor to the rotor hub coupling parameters that are available for the designer. The results are presented over the complete range of rotor speed and collective pitch available and the effects on air resonance of the 6 beam installation angles are compared together with the results of offsetting the cuff snubber attachment. The major part of the study was conducted using the FLAIR analysis which incorporates a uniform representation of the flexbeam. Results are also shown for a modified version of FLAIR in which the uniform beam is replaced by a member having the geometric tailoring resulting from structural optimization.

Hooper, W. E.↗

NASA NTRS1986

Multispectral glancing incidence X-ray telescope

A multispectural glancing incidence X-ray telescope is illustrated capable of broadband, high-resolution imaging of solar and stellar X-ray and extreme ultraviolet radiation sources which includes a primary optical system preferably of the Wolter I type having a primary mirror system. The primary optical system further includes an optical axis having a primary focus at which the incoming radiation is focused by the primary mirrors. A plurality of ellipsoidal mirrors are carried at an inclination to the optical axis behind the primary focus. A rotating carrier is provided on which the ellipsoidal mirrors are carried so that a desired one of the ellipsoidal mirrors may be selectively positioned in front of the incoming radiation beam. In the preferred embodiment, each of the ellipsoidal mirrors has an identical concave surface carrying a layered synthetic microstructure coating tailored to reflect a desired wavelength of 1.5A or longer. Each of the identifical ellipsoidal mirrors has a second focus at which a detector is carried. Thus the different wavelength image is focused upon the detector irregardless of which mirror is positioned in front of the radiation beam.

Hoover, R. B.↗

NASA NTRS1986

Analytical ultrasonics for evaluation of composite materials response. Part 2: Generation and detection

To evaluate the response of composite materials, it is imperative that the input excitation as well as the observed output be well characterized. This characterization ideally should be in terms of displacements as a function of time with high spatial resolution. Additionally, the ability to prescribe these features for the excitation is highly desirable. Various methods for generating and detecting ultrasound in advanced composite materials are examined. Characterization and tailoring of input excitation is considered for contact and noncontact, mechanical, and electromechanical devices. Type of response as well as temporal and spatial resolution of detection methods are discussed as well. Results of investigations at Virginia Tech in application of these techniques to characterizing the response of advanced composites are presented.

Duke, J. C., Jr.↗

NASA NTRS1985

The design and implementation of cost-effective algorithms for direct solution of banded linear systems on the vector processor system 32 supercomputer

The problem of solving banded linear systems by direct (non-iterative) techniques on the Vector Processor System (VPS) 32 supercomputer is considered. Two efficient direct methods for solving banded linear systems on the VPS 32 are described. The vector cyclic reduction (VCR) algorithm is discussed in detail. The performance of the VCR on a three parameter model problem is also illustrated. The VCR is an adaptation of the conventional point cyclic reduction algorithm. The second direct method is the Customized Reduction of Augmented Triangles' (CRAT). CRAT has the dominant characteristics of an efficient VPS 32 algorithm. CRAT is tailored to the pipeline architecture of the VPS 32 and as a consequence the algorithm is implicitly vectorizable.

Samba, A. S.↗

NASA NTRS1984

Highly Maneuverable Aircraft Technology (HiMAT) flight-flutter test program

The highly maneuverable aircraft technology (HiMAT) vehicle was evaluated in a joint NASA and Air Force flight test program. The HiMAT vehicle is a remotely piloted research vehicle. Its design incorporates the use of advanced composite materials in the wings, and canards for aeroelastic tailoring. A flight-flutter test program was conducted to clear a sufficient flight envelope to allow for performance, stability and control, and loads testing. Testing was accomplished with and without flight control-surface dampers. Flutter clearance of the vehicle indicated satisfactory damping and damping trends for the structural modes of the HiMAT vehicle. The data presented include frequency and damping plotted as a function of Mach number.

Kehoe, M. W.↗

NASA NTRS1985

Summary of process research analysis efforts

A summary of solar-cell process research analysis efforts was presented. Process design and cell design are interactive efforts where technology from integrated circuit processes and other processes are blended. The primary factors that control cell efficiency are: (1) the bulk parameters of the available sheet material, (2) the retention and enhancement of these bulk parameters, and (3) the cell design and the cost to produce versus the finished cells performance. The process sequences need to be tailored to be compatible with the sheet form, the cell shape form, and the processing equipment. New process options that require further evaluation and utilization are lasers, robotics, thermal pulse techniques, and new materials. There are numerous process control techniques that can be adapted and used that will improve product uniformity and reduced costs. Two factors that can lead to longer life modules are the use of solar cell diffusion barriers and improved encapsulation.

Burger, D. R.↗

NASA NTRS1986

CSTAR star catalogue development

The Continuous Stellar Tracking Attitude Reference (CSTAR) system is an in-house project for the Space Station to provide high accuracy, drift free attitude and angular rate information for the GN&C system. Constraints exist on the star catalogue incorporated in the system. These constraints include the following: mass memory allocated for catalogue storage, star tracker imaging sensitivity, the minimum resolvable separation angle between stars, the width of the field of view of the star tracker, and the desired number of stars to be tracked in a field of view. The Smithsonian Astrophysical Observatory (SAO) catalogue is the basis reference for this study. As it stands, the SAO does not meet the requirements of any of the above constraints. Star selection algorithms have been devised for catalogue optimization. Star distribution statistics have been obtained to aid in the development of these rules. VAX based software has been developed to implement the star selection algorithms. The software is modular and provides a design tool to tailor the catalogue to available star tracker technology. The SAO catalogue has been optimized for the requirements of the present CSTAR system.

Uhde-Lacovara, J. A.↗

NASA NTRS1986

The continuing battle against defects in nickel-base superalloys

In the six decades since the identification of age hardenable nickel-base superalloys their compositions and microstructures have changed markedly. Current alloys are tailored for specific applications. Thus their microstructures are defined for that application. This paper briefly reviews the evolution of superalloy microstructures and comments on the appearance and implications of microstructural defects in high performance superalloys. It is seen that new alloys and proceses have generated new types of defects. Thus as the industry continues to develop new alloys and processes it must remain vigilant toward the identification and control of new types of defects.

Dreshfield, R. L.↗

NASA NTRS1986

Optimal cooperative control synthesis of active displays

The utility of augmenting displays to aid the human operator in controlling high order complex systems is well known. Analytical evaluation of various display designs for a simple k/s sup 2 plant in a compensatory tracking task using an optimal Control Model (OCM) of human behavior is carried out. This analysis reveals that significant improvement in performance should be obtained by skillful integration of key information into the display dynamics. The cooperative control synthesis technique previously developed to design pilot-optimal control augmentation is extended to incorporate the simultaneous design of performance enhancing augmented displays. The application of the cooperative control synthesis technique to the design of augmented displays is discussed for the simple k/s sup 2 plant. This technique is intended to provide a systematic approach to design optimally augmented displays tailored for specific tasks.

Garg, S.↗

NASA NTRS1986

Fiber reinforced glasses and glass-ceramics for high performance applications

The development of fiber reinforced glass and glass-ceramic matrix composites is described. The general concepts involved in composite fabrication and resultant composite properties are given for a broad range of fiber and matrix combinations. It is shown that composite materials can be tailored to achieve high levels of toughness, strength, and elastic stiffness, as well as wear resistance and dimensional stability.

Prewo, K. M.↗

NASA NTRS1985

Noise transmission of double wall composite shells

This paper describes analytical studies of noise transmission of double wall laminated composite cylindrical shells of finite extent. The main objective is to estimate structureborne noise generated by the concentrated random forces. The theoretical solutions of the governing acoustic-structural equations are obtained utilizing modal decomposition. Results indicate that from the viewpoint of noise attenuation the composite shell does not seem to offer advantage over an aluminum shell. However, the orientation of the fibers and the material characteristics of the soft viscoelastic core can be tailored to meet the specific needs of noise attenuation.

Vaicaitis, R.↗

NASA NTRS1985

Analysis of a two row hydrostatic journal bearing with variable properties, inertia effects and surface roughness

A computer algorithm for simulation of hydrostatic journal bearing pressure-flow behavior has been generated. The effects taken into account are inertia, cavitation, variable properties (isothermal bearing) and roughness. The program has been specifically tailored for simulation of the hybrid bearing of the cryogenic turbopumps of the main shuttle engine. Due to the high pressure (515 psia) of the supply line no cavitation has been found. The influence of the roughness effects have been found to become important only when the surface-roughness order of magnitude is comparable with that of the bearing clearance itself. Pocket edge inertia and variable properties have been found to have quite an important influence upon the pocket pressure, field pressure distribution and lubricant mass flow.

Braun, M. J.↗

NASA NTRS1985

Upper air forecasting for aviation in the United States

It is shown that the present forecast models used in the aviation digital forecast (ADF) product for automated flight planning in the U.S. did not improve in accuracy and precision over the past two decades. A new approach to the upper air forecasting is presented in the NASA/NOAA MERIT project. In MERIT, a concept of a tailored analysis is used, based on a high density automated aircraft report database (including radiosonde and satellite data), producing an accurate and precise description of the initial state of the atmosphere, and a relatively simple forecast model to move the forecast forward in time. The steadily updated 2-12 h forecasts provided every 3 h will be more efficient and accurate than the present 18 and 24 h forecasts provided every 12 hours.

Steinberg, R.↗

NASA NTRS1986

The evaluation of single crystal superalloys for turbopump blades in the SSME

This paper discusses single-crystal nickel-base superalloys for use in gaseous hydrogen environments, like the Space Shuttle Main Engine (SSME). PWA 1480E was chosen as a candidate alloy based on strength retention in hydrogen environments. Selection of single-crystal-alloy primary and secondary crystallographic axes allows tailoring of the airfoil resonant frequency as a function of orientation. PWA 1480E 111-line primary orientation proved to be the most hydrogen-resistant orientation. By choosing the proper primary and secondary orientation combinations, the fourth excitation mode of the SSME may be avoided.

Bowen, K.↗