An attached flow design of a noninterfering leading-edge extension to a thick delta wing
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Ghaffari, F.↗
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Extension for ground-based testing for large space structures
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Wada, B. K.↗
Robots as man-extension systems in space
The main topic of the paper is sensing and computer based automation and man-machine interface devices and techniques which permit task-level and 'intelligent' two-way communication between human operator and remote robot in earth orbit. General considerations are presented on control and information problems in teleoperation and on the characteristics of earth orbital teleoperation. Specific control and information display devices and techniques are discussed and exemplified with development results obtained at the Jet Propulsion Laboratory (JPL) in recent years.
Bejczy, A. K.↗
Extension of continental lithosphere - A model for two scales of basin and range deformation
The development of a model for deformation in an extending continental lithosphere that is stratified in density and strength is described. The lithosphere model demonstrates that the necking instabilities at two wavelengths originate due to a strong upper crust, a mantle layer, and a weak lower crust. It is observed that the dominant wavelengths of necking are controlled by layer thickness and the strength of the layers control the amplitude of the instabilities. The model is applied to the Basin and Range Province of the western U.S. where deformations in ranges and tile domains are detected. The relation between the Bouguer gravity anomaly and the deformations is studied. The data reveal that the horizontal scale of short wavelength necking correlates with the spacings of individual basins and ranges, and the longer wavelength corresponds to the width of tilt domains. The control of the Basin and Range deformation by two scales of extensional instability is proposed.
Zuber, M. T.↗
Experimental evaluation of candidate carbon-carbon materials for OTV engine nozzle extensions
Advanced carbon-carbon nozzle materials can reduce the weight and improve the efficiency of the proposed reusable Orbit Transfer Vehicle (OTV) liquid rocket engine. Experimental evaluations of eight carbon-carbon materials in an O2/H2 rocket nozzle environment have been performed. The hot fire testing will support the choice of the materials for the OTV nozzle design. The OTV nozzle requirements and operating environment are defined. The rocket device used to simulate the OTV hot-fire nozzle environment for material specimen evaluation is described. The results of hot-fire testing for eight carbon-carbon materials are discussed. Results for coated and uncoated materials, evaluated in side-by-side testing, are compared. Plans for further testing of the leading materials are described.
Suhoza, J. P.↗
Extension of Subreflector Increases Antenna Efficiency
According to calculations, efficiency of offset Cassegrain reflector antenna increased by about 8 percent by extending edge of subreflector outward about 1 wavelength beyond optical limit. Even though main reflector partially shadowed by subreflector, partial aperture blockage more than offset by consequent reduction of diffraction on subreflector. Similar conclusions apply to symmetric Cassegrain antennas.
Rahmat-Samii, Y.↗
The evaluation and extension of TAE in the development of a user interface management system
The development of a user interface management system (UIMS) for an information gathering and display system is discussed. The system interface requirements are outlined along with the UIMS functional characteristics. Those systems requirements which are supported by the current Transportable Applications Executive (TAE) are listed and necessary modifications to the TAE are described.
Burkhart, Brenda↗
Extension of vibrational power flow techniques to two-dimensional structures
In the analysis of the vibration response and structure-borne vibration transmission between elements of a complex structure, statistical energy analysis (SEA) or Finite Element Analysis (FEA) are generally used. However, an alternative method is using vibrational power flow techniques which can be especially useful in the mid- frequencies between the optimum frequency regimes for FEA and SEA. Power flow analysis has in general been used on one-dimensional beam-like structures or between structures with point joints. In this paper, the power flow technique is extended to two-dimensional plate like structures joined along a common edge without frequency or spatial averaging the results, such that the resonant response of the structure is determined. The power flow results are compared to results obtained using FEA at low frequencies and SEA at high frequencies. The agreement with FEA results is good but the power flow technique has an improved computational efficiency. Compared to the SEA results the power flow results show a closer representation of the actual response of the structure.
Cuschieri, J. M.↗
Nonlinear programming extensions to rational function approximations of unsteady aerodynamics
This paper deals with approximating unsteady generalized aerodynamic forces in the equations of motion of a flexible aircraft. Two methods of formulating these approximations are extended to include both the same flexibility in constraining them and the same methodology in optimizing nonlinear parameters as another currently used 'extended least-squares' method. Optimal selection of 'nonlinear' parameters is made in each of the three methods by use of the same nonlinear (nongradient) optimizer. The objective of the nonlinear optimization is to obtain rational approximations to the unsteady aerodynamics whose state-space realization is of lower order than that required when no optimization of the nonlinear terms is performed. The free 'linear' parameters are determined using least-squares matrix techniques on a Lagrange multiplier formulation of an objective function which incorporates selected linear equality constraints. State-space mathematical models resulting from the different approaches are described, and results are presented which show comparative evaluations from application of each of the extended methods to a numerical example. The results obtained for the example problem show a significant (up to 63 percent) reduction in the number of differential equations used to represent the unsteady aerodynamic forces in linear time-invariant equations of motion as compared to a conventional method in which nonlinear terms are not optimized.
Tiffany, Sherwood H.↗
Extension and applications of flux-vector splitting to unsteady calculations on dynamic meshes
The Van Leer method of flux-vector splitting for the Euler equations is extended for use on moving meshes and all the properties of the original splittings are maintained. The solution is advanced in time with an implicit, approximately factored algorithm. The use of multiple grids to reduce the computer time is investigated. A substantial reduction in computer time to resolve a pitching cycle is easily obtained with virtually no loss in accuracy. A subiterative procedure to eliminate factorization and linearization errors so that larger time steps can be used is also investigated. Subsequent computations show good agreement with experimental data for transonic and supersonic airfoils and wings undergoing forced pitching oscillation.
Anderson, W. Kyle↗
Extension of a semi-implicit shock-capturing algorithm for 3-D fully coupled, chemically reacting flows in generalized coordinates
A semiimplicit high-resolution shock-capturing method for multidimensional systems of hyperbolic conservation laws with stiff source terms has been developed by Yee and Shinn (1987). The goal of this work is to extend this method to solve the three-dimensional fully coupled Navier-Stokes equations for a hypersonic chemically reacting flow in generalized coordinates. In this formulation, the global continuity equation was replaced by all the species continuity equations. The shock-capturing technique is a second-order-accurate, symmetric total-variation-diminishing method which accounts fully and directly for the coupling among the fluid and all the species. To verify the current approach, it was implemented into an existing computer code which contained the MacCormack method. Test results for a five-species reacting flow are shown to be oscillation-free around the shock, and the time spent per iteration only doubles when compared to the result using classical way of supplying numerical dissipation. The extra computation is more than justified by the elimination of spurious oscillation and nonlinear instability associated with the classical shock-capturing schemes in computing hypersonic reacting flows.
Shinn, J. L.↗
Ultraviolet observations of extensive variability in the stellar wind of Xi Persei
A detailed case study of variability in the stellar wind of the O7.5 III star Xi Persei is presented based on 56 high-resolution IUE observations taken between 1978 and 1984. Profile-fitting techniques are described, and possible interpretations for the observed Si IV variability are discussed. The derived properties of the narrow and broad discrete absorption features are given along with other P Cygni profile characteristics, including emission-to-absorption ratios and mass-loss rates. The role of ionization conditions and episodic formation of shells in accounting for the variability is addressed together with some previously reported observations of Xi Per.
Prinja, Raman K.↗
Nonlinear programming extensions to rational function approximation methods for unsteady aerodynamic forces
The approximation of unsteady generalized aerodynamic forces in the equations of motion of a flexible aircraft are discussed. Two methods of formulating these approximations are extended to include the same flexibility in constraining the approximations and the same methodology in optimizing nonlinear parameters as another currently used extended least-squares method. Optimal selection of nonlinear parameters is made in each of the three methods by use of the same nonlinear, nongradient optimizer. The objective of the nonlinear optimization is to obtain rational approximations to the unsteady aerodynamics whose state-space realization is lower order than that required when no optimization of the nonlinear terms is performed. The free linear parameters are determined using the least-squares matrix techniques of a Lagrange multiplier formulation of an objective function which incorporates selected linear equality constraints. State-space mathematical models resulting from different approaches are described and results are presented that show comparative evaluations from application of each of the extended methods to a numerical example.
Tiffany, Sherwood H.↗
Effect of initial flaw shape on crack extension in orthotropic composite materials
An analytical study is presented showing the effects of the notch tip geometry on the location and direction of crack growth from an existing notch in a unidirectional fibrous composite modelled as a homogeneous, anisotropic, elastic material. Anisotropic elasticity and the normal stress ratio theory are used to study crack growth from elliptical notches in unidirectional composites. Sharp cracks, circular holes, and ellipses are studied under far-field tension and shear loading. Limited comparisons are made showing good correlation with experimental results.
Gurdal, Z.↗
Extension of hypersonic, high-incidence, slender-body similarity
The Sychev (1960) analysis for inviscid hypersonic flow past slender bodies at large angle of attack is shown to be applicable to all slender-body flows whose crossflow Mach numbers are greater than sonic; it is therefore not restricted to flows with hypersonic crossflow Mach number values, as indicated elsewhere in the literature. It is also noted that the Sychev similarity applies to a number of slender-body flows with subsonic crossflow Mach numbers, including incompressible flow.
Barnwell, Richard W.↗
Long extension reeling in the stratosphere - A progress report
Results of the second flight of the Harvard Reel Down balloon-born winching system, in which a more complex photochemical detection package was twice lowered from a float altitude of 39 km and reeled back to the winch, are reported. Modifications over the original package design include improvements to the winch platform and reconstruction of the suspended detection package for specific ClO measurement and for tight weight control. Controlled velocities of 4-7 m/sec were implemented for both of the scans, and the package was brought to a brief stop during the first scan to evaluate dynamic effects. The results demonstrate the operational effectiveness of the system.
Hazen, N.↗
Extension of the Johnson-King turbulence model to the 3-D flows
A critical evaluation of the eddy viscosity model of Johnson and King extended to the three-dimensional case has been performed for three-dimensional boundary layer flows. The turbulence model is evaluated by a detailed comparison with available experimental data for incompressible flows over an infinite swept wing and near an idealized wing-body junction. The isotropic model of Johnson and King is found to work much better than the Cebeci-Smith model, especially in regions of strong cross flow. The significant decrease in the shear stress magnitude is almost reproduced. This means that this effect is as important as the nonisotropic eddy viscosity. The introduction of Rotta's modification to account for nonisotropic eddy viscosity in the Johnson-King formulation is found to have little effect on the predictions. The cross-flow properties are the most strongly affected.
Abid, Ridha↗
Temperature effects on the pickup process of water group and hydrogen ions - Extensions of 'A theory for low-frequency waves observed at Comet Giacobini-Zinner' by M. L. Goldstein and H. K. Wong
Cometary heavy ions can resonantly excite hydromagnetic wave activity with spacecraft frequency spectra strongly deviating from the ion cyclotron frequency. The influence of the newborn particle temperature on this effect is assessed, its relevance to the interpretation of the observations is discussed, and an alternative, more efficient mechanism to generate spacecraft frequencies of the order of the proton cyclotron frequency is suggested.
Brinca, Armando L.↗