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NASA NTRS1982

Expansion series of integral functions occurring in unsteady aerodynamics

Attention is given to two real integral functions which occur in the kernel of singular integral equations for subsonic unsteady lifting surfaces. The arguments k, r, and X of the functions correspond to the reduced frequency, spanwise distance, and modified coordinate in the flow direction, respectively. The value of the parameter nu in the functions depends on geometrical conditions. The considered investigation has the objective to present a series for general values of the nonnegative integer nu in order to compute efficiently the integral functions. The approach makes it possible to avoid any approximation or numerical quadrature.

Ueda, T.↗

NASA NTRS1982

An accurate and efficient method for evaluating the kernel of the integral equation relating pressure to normalwash in unsteady potential flow

This paper describes an accurate economical method for generating approximations to the kernel of the integral equation relating unsteady pressure to normalwash in nonplanar flow. The method is capable of generating approximations of arbitrary accuracy. It is based on approximating the algebraic part of the non elementary integrals in the kernel by exponential approximations and then integrating termwise. The exponent spacing in the approximation is a geometric sequence. The coefficients and exponent multiplier of the exponential approximation are computed by least squares so the method is completely automated. Exponential approximates generated in this manner are two orders of magnitude more accurate than the exponential approximation that is currently most often used for this purpose. Coefficients for 8, 12, 24, and 72 term approximations are tabulated in the report. Also, since the method is automated, it can be used to generate approximations to attain any desired trade-off between accuracy and computing cost.

Desmarais, R. N.↗

NASA NTRS1982

The role and application of data base management in integrated computer-aided design

The need to marshal the extensive data that figure in design problems is underlined. An approach to managing engineering data for use in a computerized integrated design system is described. The approach is embodied in an experimental integrated software system that is used to demonstrate and evaluate such data management functions as storage, retrieval, query, manipulation, and modification. The development and organization of the experimental integrated design system and the application of the system to selected test problems are discussed, together with insights into data management issues gained from the study.

Blackburn, C. L.↗

NASA NTRS1982

On a study of the /Delta T/c and C/asterisk/ integrals for fracture analysis under non-steady creep

Applications of a vector quantity, path-independent integral which has an energy interpretation to the characterization of crack-tip fields in the range from fast to slow crack propagation are examined. The crack tip characterization parameter is defined in terms of a conservation integral for an area around the crack tip in a two-dimensional cracked body. The actual physical interpretation of the parameter is shown to be the difference in crack lengths displayed by two identical bodies which have equal load histories. A steady-state value is obtained for the parameter for cases of steady-state creep and is shown to be related to the standard path-independent integral for macroscopic self-similar crack growth under mode I conditions. A finite element model is developed for viscoplastic material models, using an initial strain approach with steps in a size employed in tangent stiffness methods.

Stonesifer, R. B.↗

NASA NTRS1980

Integration of design information

The overall concepts of the integrated programs for aerospace-vehicle design (IPAD) from the user's viewpoint are discussed. Also a top-level view of what the user requires from such a system is provided, and the interactions between the system and user are described. The four major components discussed are design process; data storage, management and manipulation; user interface; and project management. Although an outgrowth of aerospace production experience, the basic concepts discussed, and especially their emphasis on integration, are considered applicable to all problem solving. Thus, these concepts may offer a broad base for exploitation by industry in general. This is the first in a set of three papers, the other two being Future Integrated Design Process, by D. D. Mayer, and Requirements for Company-Wide Management of Engineering Information, by J. W. Southall. In addition to tying the three together, how project management can be handled in a computing environment and also the user interface needs are discussed in detail.

Anderton, G. L.↗

NASA NTRS1981

Integrated resource inventory for southcentral Alaska (INTRISCA)

The Integrated Resource Inventory for Southcentral Alaska (INTRISCA) Project comprised an integrated set of activities related to the land use planning and resource management requirements of the participating agencies within the southcentral region of Alaska. One subproject involved generating a region-wide land cover inventory of use to all participating agencies. Toward this end, participants first obtained a broad overview of the entire region and identified reasonable expectations of a LANDSAT-based land cover inventory through evaluation of an earlier classification generated during the Alaska Water Level B Study. Classification of more recent LANDSAT data was then undertaken by INTRISCA participants. The latter classification produced a land cover data set that was more specifically related to individual agency needs, concurrently providing a comprehensive training experience for Alaska agency personnel. Other subprojects employed multi-level analysis techniques ranging from refinement of the region-wide classification and photointerpretation, to digital edge enhancement and integration of land cover data into a geographic information system (GIS).

Burns, T.↗

NASA NTRS1983

Progress in propulsion system/airframe structural integration

Attention is given to the improvements in mathematical modeling, and the emerging role of computer-related technology, in airframe structural technology advancements related to the engine/airframe integration requirements of such recent designs as the 747 airliner's JT9D turbofan engine nacelle. Also noted are investigation results concerning propulsion system flight loads and their influence on thrust-specific fuel consumption deterioration, which has been addressed through the development of the novel structural concept of the 'load-carrying core cowl' engine nacelle structure. Analytical studies on integrated system vibration include low frequency, nonsynchronous vibration analyses of large, high bypass turbofan engines that have been conducted by means of three-dimensional integrated finite element models.

White, J. L.↗

NASA NTRS1983

An integral analysis of transonic normal shock wave/turbulent boundary layer interactions in internal flow

An approximate integral viscous-inviscid interaction method is presented for calculating the development of a turbulent boundary layer subjected to a normal shock wave induced adverse pressure gradient in an internal axisymmetric flow. The inflow conditions and the downstream pressure are provided for the computation. In the supersonic region of shock pressure rise, the Prandtl-Meyer function is used to couple the viscous and inviscid flows. An analytical model for the coupling process is postulated and appropriate equations are defined. Downstream of the sonic point, one-dimensional inviscid flow is assumed for coupling with the viscous flow. The turbulent boundary layer is calculated using Green's integral lag-entrainment method. Comparisons of the solutions with the experimental data are made for interactions which are unseparated, near separation and separated. For comparison purposes, solutions to the time-dependent, mass-averaged, Navier-Stokes equations incorporating a two-equation, Wilcox-Rubesin turbulence model are also shown. The computed results from the integral method show good agreement with experimental data for unseparated interactions and reasonable agreement with the trend of the viscous effects when the interaction becomes increasingly separated.

Om, D.↗

NASA NTRS1983

DE 102 - A numerically integrated ephemeris of the moon and planets spanning forty-four centuries

It is pointed out that the 1960's were the turning point for the generation of lunar and planetary ephemerides. All previous measurements of the positions of solar system bodies were optical angular measurements. New technological improvements leading to immense changes in observational accuracy are related to developments concerning radar, Viking landers on Mars, and laser ranges to lunar corner cube retroreflectors. Suitable numerical integration techniques and more comprehensive physical models were developed to match the accuracy of the modern data types. The present investigation is concerned with the first integrated ephemeris, DE 102, which covers the entire span of the historical astronomical observations of usable accuracy which are known. The fit is made to modern data. The integration spans the time period from 1411 BC to 3002 AD.

Newhall, X. X.↗

NASA NTRS1983

Project management techniques for highly integrated programs

The management and control of a representative, highly integrated high-technology project, in the X-29A aircraft flight test project is addressed. The X-29A research aircraft required the development and integration of eight distinct technologies in one aircraft. The project management system developed for the X-29A flight test program focuses on the dynamic interactions and the the intercommunication among components of the system. The insights gained from the new conceptual framework permitted subordination of departments to more functional units of decisionmaking, information processing, and communication networks. These processes were used to develop a project management system for the X-29A around the information flows that minimized the effects inherent in sampled-data systems and exploited the closed-loop multivariable nature of highly integrated projects.

Stewart, J. F.↗

NASA NTRS1983

V-band integrated quadriphase modulator

A V-band integrated circuit quadriphase shift keyed modulator/exciter for space communications systems was developed. Intersatellite communications systems require direct modulation at 60 GHz to enhance signal processing capability. For most systems, particularly space applications, small and lightweight components are essential to alleviate severe system design constraints. Thus to achieve wideband, high data rate systems, direct modulation techniques at millimeter waves using solid state integrated circuit technology are an integral part of the overall technology developments.

Grote, A.↗

NASA NTRS1984

Exponential-fitted methods for integrating stiff systems of ordinary differential equations: Applications to homogeneous gas-phase chemical kinetics

Conventional algorithms for the numerical integration of ordinary differential equations (ODEs) are based on the use of polynomial functions as interpolants. However, the exact solutions of stiff ODEs behave like decaying exponential functions, which are poorly approximated by polynomials. An obvious choice of interpolant are the exponential functions themselves, or their low-order diagonal Pade (rational function) approximants. A number of explicit, A-stable, integration algorithms were derived from the use of a three-parameter exponential function as interpolant, and their relationship to low-order, polynomial-based and rational-function-based implicit and explicit methods were shown by examining their low-order diagonal Pade approximants. A robust implicit formula was derived by exponential fitting the trapezoidal rule. Application of these algorithms to integration of the ODEs governing homogenous, gas-phase chemical kinetics was demonstrated in a developmental code CREK1D, which compares favorably with the Gear-Hindmarsh code LSODE in spite of the use of a primitive stepsize control strategy.

Pratt, D. T.↗

NASA NTRS1983

Galileo spacecraft integration - International cooperation on a planetary mission in the Shuttle era

The Galileo mission is designed to greatly expand scientific knowledge of Jupiter and its system. The retropropulsion module (RPM) as a major functional element of the Galileo spacecraft is described. The major mission and spacecraft requirements on the RPM are presented. Complexities of the integration process due to the international interface are identified. Challenges associated with integration with new launch vehicles, the Shuttle and upper stage, and their relationships to the RPM are discussed. The results of the integration process involving mission and propulsion performance, reliability, mechanical and thermal interfaces, and safety are described. Finally, considerations and recommendations for future missions involving international cooperation are given.

Spehalski, R. J.↗

NASA NTRS1984

Elements of computational engine-airframe integration

Computerized flow simulation methods are being developed to refine the traditional engine-airframe integration process. These analyses reduce design risk, minimize wind tunnel and flight test requirements, and provide detailed design information not available by any other means. This paper describes computational tools which have matured sufficiently to permit project applications. Several applications are combined with research studies to illustrate the prediction of high-speed nonlinear phenomena associated with engine inlet flow rate, nacelle shape and position, afterbody shape and integration, propeller slipstream interactions, airframe-induced inlet flow, and pylon integration. Both fighter and transport configurations are used to highlight current capabilities and future requirements.

Boppe, C. W.↗

NASA NTRS1984

The uniform asymptotic swallowtail approximation - Practical methods for oscillating integrals with four coalescing saddle points

Methods that can be used in the numerical implementation of the uniform swallowtail approximation are described. An explicit expression for that approximation is presented to the lowest order, showing that there are three problems which must be overcome in practice before the approximation can be applied to any given problem. It is shown that a recently developed quadrature method can be used for the accurate numerical evaluation of the swallowtail canonical integral and its partial derivatives. Isometric plots of these are presented to illustrate some of their properties. The problem of obtaining the arguments of the swallowtail integral from an analytical function of its argument is considered, describing two methods of solving this problem. The asymptotic evaluation of the butterfly canonical integral is addressed.

Connor, J. N. L.↗

NASA NTRS1983

Integrated water management system - Description and test results

Water recovery subsystems are being tested at the NASA Lyndon B. Johnson Space Center for Space Station use to process waste water generated from urine and wash water collection facilities. These subsystems are being integrated into a water management system that will incorporate wash water and urine processing through the use of hyperfiltration and vapor compression distillation subsystems. Other hardware in the water management system includes a whole body shower, a clothes washing facility, a urine collection and pretreatment unit, a recovered water post-treatment system, and a water quality monitor. This paper describes the integrated test configuration, pertinent performance data, and feasibility and design compatibility conclusions of the integrated water management system.

Elden, N. C.↗

NASA NTRS1984

Integral radial cosmic ray gradients in the solar system from 1972 to 1982

The cosmic-ray telescope data on IMP 8, Voyagers 1 and 2, and Pioneer 10 have been used to determine the integral radial cosmic-ray intensity gradients for energies greater than 60 MeV per nucleon. When the 26 day average counting rates are time-shifted for the effects of the outward propagation speed of the solar modulation, the average integral radial gradients (Gr) are 3.0 + or - 0.35 (percent/AU) from 1975 to 1982. Gr is independent to the first order of the cosmic-ray intensity and radial heliocentric distance out to about 30 AU. After the large transient variations in the cosmic-ray intensity in mid-1982, the integral gradients returned to their original values.

Lockwood, J. A.↗

NASA NTRS1984

Integrating amplifiers using cooled JFETs

It is shown how a simple integrating amplifier based on commercially available JFET and MOSFET switches can be used to measure photocurrents from detectors with noise levels as low as 1.6 x 10 to the -18th A/root Hz (10 electrons/sec). A figure shows the basic circuit, along with the waveform at the output. The readout is completely nondestructive; the reset noise does not contribute since sampling of the accumulated charge occurs between resets which are required only when the stored charge has reached a very high level. The storage capacity ranges from 10 to the 6th to 10 to the 9th electrons, depending on detector parameters and linearity requirements. Data taken with an Si:Sb detector operated at 24 microns are presented. The responsivity agrees well with the value obtained by Young et al. (1981) in the transimpedance amplifier circuit. The data are seen as indicating that extremely low values of NEP can be obtained for integration times of 1 sec and that longer integrations continue to improve the SNR at a rate faster than the square root of time when background noise is not present.

Low, F. J.↗