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NASA NTRS1988

Basic results of medical studies during prolonged manned flights on-board the Salyut-7/Soyuz-T orbital complex

From 1982 through 1986 six extended flights (from 65 to 237 days) were carried out in the Salyut-7/Soyuz-T orbital complex by the principal crews, and five short-term flights (8 to 12 days) by visiting crews. During these flights, a broad series of medical studies was performed, their greatest extent during the longest flight (237 days), with the participation of a cosmonaut-doctor. The medical studies were aimed at obtaining additional information and new data on the reactions of the body's basic systems during a prolonged state of weightlessness.

Source record↗

NASA NTRS1988

On the sensitivity of complex, internally coupled systems

A method is presented for computing sensitivity derivatives with respect to independent (input) variables for complex, internally coupled systems, while avoiding the cost and inaccuracy of finite differencing performed on the entire system analysis. The method entails two alternative algorithms: the first is based on the classical implicit function theorem formulated on residuals of governing equations, and the second develops the system sensitivity equations in a new form using the partial (local) sensitivity derivatives of the output with respect to the input of each part of the system. A few application examples are presented to illustrate the discussion.

Sobieszczanskisobieski, Jaroslaw↗

NASA NTRS1987

Complex space monofilar approximation of diffraction currents on a conducting half plane

Simple approximation of diffraction surface currents on a conducting half plane, due to an incoming plane wave, is obtained with a line current (monofile) in complex space. When compared to an approximating current at the edge, the diffraction pattern is seen to improve by an order of magnitude for a minimal increase of computation effort. Thus, the inconvient Fresnel integral functions can be avoided for quick calculations of diffracted fields and the accuracy is good in other directions than along the half plane. The method can be applied to general problems involving planar metal edges.

Lindell, I. V.↗

NASA NTRS1986

Full potential methods for analysis/design of complex aerospace configurations

The steady form of the full potential equation, in conservative form, is employed to analyze and design a wide variety of complex aerodynamic shapes. The nonlinear method is based on the theory of characteristic signal propagation coupled with novel flux biasing concepts and body-fitted mapping procedures. The resulting codes are vectorized for the CRAY XMP and the VPS-32 supercomputers. Use of the full potential nonlinear theory is demonstrated for a single-point supersonic wing design and a multipoint design for transonic maneuver/supersonic cruise/maneuver conditions. Achievement of high aerodynamic efficiency through numerical design is verified by wind tunnel tests. Other studies reported include analyses of a canard/wing/nacelle fighter geometry.

Shankar, Vijaya↗

NASA NTRS1988

Minimum-complexity helicopter simulation math model

An example of a minimal complexity simulation helicopter math model is presented. Motivating factors are the computational delays, cost, and inflexibility of the very sophisticated math models now in common use. A helicopter model form is given which addresses each of these factors and provides better engineering understanding of the specific handling qualities features which are apparent to the simulator pilot. The technical approach begins with specification of features which are to be modeled, followed by a build up of individual vehicle components and definition of equations. Model matching and estimation procedures are given which enable the modeling of specific helicopters from basic data sources such as flight manuals. Checkout procedures are given which provide for total model validation. A number of possible model extensions and refinement are discussed. Math model computer programs are defined and listed.

Heffley, Robert K.↗

NASA NTRS1988

An illustration of the complexity of continent formation

It was pointed out that a consensus may be emerging in crustal growth models, considering the clustering of most growth curves and their uncertainties. Curves most distant from this clustering represent models involving extensive recycling of continental material back into the mantle, but the author wondered if geochemical signatures for this would be recognizable considering the lack of evidence from seismic tomography for discrete mantle reservoirs, and the likelihood of core-mantle interaction based on recent high pressure experiments. Unreactivated Archean rocks represent only 2 percent of present continental area, and the author was uncomfortable about basing inferences on what the early Earth was like on such a small amount of information. He feels that the hypothesis of continental assembly that needs testing is that of banging together of island arcs, such as in Indonesia today. As an example of how complex this process can be, the author described the geology of the Caribbean arc system, which shows evidence for reversals of subduction polarity, numerous collisional events, and substantial strike-slip movements. It seemed unlikely to the author that Archean examples would have been less complicated.

Burke, Kevin↗

NASA NTRS1988

Evidence for crustal recycling during the Archean: The parental magmas of the stillwater complex

The petrology and geochemistry of the Stillwater Complex, an Archean (2.7 Ga) layered mafic intrusion in the Beartooth Mountains of Montana is discussed. Efforts to reconstruct the compositions of possible parental magmas and thereby place some constraints on the composition and history of their mantle source regions was studied. A high-Mg andesite or boninite magma best matches the crystallization sequences and mineral compositions of Stillwater cumulates, and represents either a primary magma composition or a secondary magma formed, for example, by assimilation of crustal material by a very Mg-rich melt such as komatiite. Isotopic data do not support the extensive amounts of assimilation required by the komatiite parent hypothesis, and it is argued that the Stillwater magma was generated from a mantle source that had been enriched by recycling and homogenization of older crustal material over a large area.

Mccallum, I. S.↗

NASA NTRS1987

Nonlinear dynamics, chaos and complex cardiac arrhythmias

Periodic stimulation of a nonlinear cardiac oscillator in vitro gives rise to complex dynamics that is well described by one-dimensional finite difference equations. As stimulation parameters are varied, a large number of different phase-locked and chaotic rhythms is observed. Similar rhythms can be observed in the intact human heart when there is interaction between two pacemaker sites. Simplified models are analyzed, which show some correspondence to clinical observations.

Glass, L.↗

NASA NTRS1987

Complex space multipole theory for scattering and diffraction problems

Classical multipole theory can be extended to multipoles located in complex space and applied in scattering and diffraction problems with the advantage that, if the point of the multipole is correctly chosen, the first term may give an order of magnitude better approximation to the source than when the multipole is in real space. The basic theory, given elsewhere, is presented here in a more straightforward manner and the improvement in radiation pattern is demonstrated for sources of constant polarization. Applications on scattering by spheroidal dielectric bodies and diffraction by a dielectric half-space are discussed.

Lindell, Ismo V.↗

NASA NTRS1988

Application of transonic slender body theory to bodies of varying complexity

Transonic flows over several bodies of varying complexity including a simple wing-body combination and the Shuttle Orbiter have been modeled with the use of slender body theory. Flows with various angles of attack have been considered. Also some off-body flow calculations were conducted. For attached flows, the calculations predicted the pressure results with good accuracy.

Rajagopal, Karunamurthy↗

NASA NTRS1988

Infrared band extinctions and complex refractive indices of crystalline C2H2 and C4H2

Thermal IR absorption intensities are obtained for thin films of crystalline C2H2 and C4H2 at 70 K, and their n and k complex refractive indices are ascertained by separating true film absorption from interface reflection on the basis of an analysis of the transmission spectrum ratio for two sample thicknesses. This method significantly simplifies the n and k iteration process. The n and k values determined in the laboratory will in most cases reproduce a given sample thickness' observed transmission to within + or - 5 percent.

Khanna, R. K.↗

NASA NTRS1987

Fan blade angle system for the National Full-scale Aerodynamic Complex

An adjustable, fan-blade-angle-positioning system for use in a wind tunnel was designed and fabricated to control the airflow from rotating fans in the National Full-scale Aerodynamic Complex (NFAC) at Ames Research Center. The NFAC consists of two test sections, a 40- by 80-ft test section with a top airspeed rating of 300 knots and an 80- by 120-ft test section with a top airspeed rating of 110 knots.

King, Reginald F.↗

NASA NTRS1988

Aerodynamic flow quality and acoustic characteristics of the 40- by 80-foot test section circuit of the National Full-Scale Aerodynamic Complex

The 40- by 80-foot wind tunnel circuit of the National Full-Scale Aerodynamic Complex (NFAC) has recently undergone major modifications and subsequently completed final acceptance testing. The initial testing and calibration of the wind tunnel are described and in many cases these results are compared with predictions derived from model tests and theoretical analyses. The wind tunnel meets or exceeds essentially all performance objectives. The facility runs smoothly and routinely at its maximum test-section velocity of 300 knots (Mach number = 0.45). An effective cooling air exchange system enables the wind tunnel to operate indefinitely at this maximum power condition. Throughout the operating envelope of the wind tunnel the test-section dynamic pressure is uniform to within + or - 0.5 deg, and the axial component of turbulence is generally less than 0.5 percent. Acoustic measurements indicate that, due to the low noise fans and acoustic treatment in the wind-tunnel circuit and test section, the background noise level in the test section is comparable to other large-scale acoustic wind tunnels in the United States and abroad.

Olson, Lawrence E.↗

NASA NTRS1988

Modeling surface deformations at complex strike-slip plate boundaries

Two new versions of the physical base-traction model of Li and Rice (1987) have been developed to study the loading processes and surface deformation near plate boundaries with geometric complexities, including a shallow creeping fault segment and two subparallel faults. Predictions of surface velocity and surface slip rate for the region between the San Andreas fault and the Pacific coast at the latitude of the Parkfield-Cholame segment using model parameters based on geologic, geodetic, and seismic considerations were found to be in good agreement with contemporary geodetic field data (not used in constrainning model parameters). Also, predicted surface velocity for the Salton Sea-Coachella Valley area were fit to recently derived contemporary geodetic data and very large baseline interferometry data, althoug here the model parameters are not well constrained.

Li, Victor C.↗

NASA NTRS1988

Optical polarization measurements in the vicinity of nearby star-forming complexes. I - The Lynds 1641 molecular cloud

Optical polarization results for 219 stars located in the vicinity of the Lynds 1641 giant molecular cloud are presented. The data indicate that L 1641 is representative of a class of star-forming complexes in which the magnetic field has played an incidental role during the global cloud-collapse phases. It is suggested that the magnetic field may control the direction of collimated mass outflows associated with young stellar objects.

Vrba, Frederick J.↗

NASA NTRS1988

Three-dimensional self-adaptive grid method for complex flows

A self-adaptive grid procedure for efficient computation of three-dimensional complex flow fields is described. The method is based on variational principles to minimize the energy of a spring system analogy which redistributes the grid points. Grid control parameters are determined by specifying maximum and minimum grid spacing. Multidirectional adaptation is achieved by splitting the procedure into a sequence of successive applications of a unidirectional adaptation. One-sided, two-directional constraints for orthogonality and smoothness are used to enhance the efficiency of the method. Feasibility of the scheme is demonstrated by application to a multinozzle, afterbody, plume flow field. Application of the algorithm for initial grid generation is illustrated by constructing a three-dimensional grid about a bump-like geometry.

Djomehri, M. Jahed↗

NASA NTRS1986

Efficient numerical techniques for complex fluid flows

The central feature in any flow prediction method is the treatment of the coupling between the momentum and continuity equations. In natural-convection flows, the energy equation also becomes strongly coupled with the momentum equations. Because of the nonlinear nature of the coupling, these equations are solved iteratively. Iterative methods are often prone to slow convergence, divergence, and extreme sensitivity to underrelaxation factors. The aim of the present research is to develop more efficient and reliable solution schemes for the coupled flow equations. Such schemes will significantly reduce the expense of computing complex flows encountered in combustion chambers, gas turbines, heat exchangers, and other practical equipment. In the work completed so far, a technique employing norm reduction in conjunction with the successive-substitution and Newton-Raphson techniques was developed. Also, a block-correction procedure for the flow equations is currently being formulated and tested.

Patankar, Suhas V.↗

NASA NTRS1988

Surface grid generation for complex three-dimensional geometries

An outline is presented for the creation of surface grids from primitive geometry data such as obtained from CAD/CAM systems. The general procedure is applicable to any geometry including full aircraft with wing, nacelle, and empennage. When developed in an interactive graphics environment, a code based on this procedure is expected to substantially improve the turn around time for generating surface grids on complex geometries. Results are shown for a general hypersonic airplane geometry.

Luh, Raymond Ching-Chung↗