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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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Process-control decisions made by applying rules to process data streams. Expert System Executive computer program demonstrates feasibility of automated real-time monitoring. Using Executives knowledge of system formally coded as set of rules specifying actions taken under various conditions. Program makes inferences about observed data based on rules. Written in C language.
The maximum entropy method (MEM) and balanced correlation method were used to reconstruct the images of low-intensity X-ray objects obtained experimentally by means of a uniformly redundant array coded aperture system. The reconstructed images from MEM are clearly superior. However, the MEM algorithm is computationally more time-consuming because of its iterative nature. On the other hand, both the inherently two-dimensional character of images and the iterative computations of MEM suggest the use of parallel processing machines. Accordingly, computations were carried out on the massively parallel processor at Goddard Space Flight Center as well as on the serial processing machine VAX 8600, and the results are compared.
The Nuclear Astrophysics Explorer was proposed in 1986 for NASA's Explorer Concept Study Program by an international collaboration of 25 scientists from nine institutions. The one-year feasibility study began in June 1988. The Nuclear Astrophysics Explorer would obtain high resolution observations of gamma-ray lines, E/Delta E about 1000, at a sensitivity of about 0.000003 ph/sq cm s, in order to study fundamental problems in astrophysics such as nucleosynthesis, supernovae, neutron star and black-hole physics, and particle acceleration and interactions. The instrument would operate from 15 keV to 10 Mev and use a heavily shielded array of nine cooled Ge spectrometers in a very low background configuration. Its 10 deg FWHM field of view would contain a versatile coded mask system which would provide two-dimensional imaging with 4 deg resolution, one-dimensional imaging with 2 deg resolution, and efficiendt measurements of diffuse emission. An unshielded Ge spectrometer would obtain wide-field measurements of transient gamma-ray sources. The earliest possible mission would begin in 1995.
The tools and methods used for the configuration management of the artifacts (including software and documentation) associated with the Guidance and Control Software (GCS) project are described. The GCS project is part of a software error studies research program. Three implementations of GCS are being produced in order to study the fundamental characteristics of the software failure process. The Code Management System (CMS) is used to track and retrieve versions of the documentation and software. Application of the CMS for this project is described and the numbering scheme is delineated for the versions of the project artifacts.
SOL is computer language geared to solution of design problems. Includes mathematical modeling and logical capabilities of computer language like FORTRAN; also includes additional power of nonlinear mathematical programming methods at language level. SOL compiler takes SOL-language statements and generates equivalent FORTRAN code and system calls. Provides syntactic and semantic checking for recovery from errors and provides detailed reports containing cross-references to show where each variable used. Implemented on VAX/VMS computer systems. Requires VAX FORTRAN compiler to produce executable program.
The Unified AeroAcoustic Program (UAAP) code calculates the airloads on a single rotation prop-fan, or propeller, and couples these airloads with an acoustic radiation theory, to provide estimates of near-field or far-field noise levels. The steady airloads can also be used to calculate the nonuniform velocity components in the propeller wake. The airloads are calculated using a three dimensional compressible panel method which considers the effects of thin, cambered, multiple blades which may be highly swept. These airloads may be either steady or unsteady. The acoustic model uses the blade thickness distribution and the steady or unsteady aerodynamic loads to calculate the acoustic radiation. The users manual for the UAAP code is divided into five sections: general code description; input description; output description; system description; and error codes. The user must have access to IMSL10 libraries (MATH and SFUN) for numerous calls made for Bessel functions and matrix inversion. For plotted output users must modify the dummy calls to plotting routines included in the code to system-specific calls appropriate to the user's installation.
Results of a recent study of a ten-bay truss structure at the NASA Langley Research Center are reported. First, the conditioning of complex eigenvectors derived by the ERA method is discussed. Results of parameter estimation using the SSID (Structural System Identification) code are then presented. Based on the results of the study, it is concluded that (1) parameter estimation based on modal data should include eigenvectors as well as eigenvalues; (2) the eigenvectors should be orthogonalized when orthogonality is poor due to closely spaced modes; and (3) the parameters used in the estimation should enable the model to match the data.
The Nuclear Astrophysics Explorer (NAE) is a concept for a possible future NASA Explorer mission which would obtain high resolution, E/Delta E about 500, observations of gamma-ray lines in order to study many fundamental problems in astrophysics. It operates from 15 keV to 10 MeV with a 3-sigma sensitivity of about 3 x 10 to the -6th ph/sq cm-s in a 10 to the 6th s observation. This is 100 times below the presently known gamma-ray line fluxes. The NAE uses a heavily shielded array of nine cooled Ge detectors in a very low background configuration. Its 10-deg field of view contains a versatile coded mask system which provides 2D imaging with 4-deg resolution, 1D imaging with 2-deg resolution and efficient measurements of emission from diffuse and point sources. The late 1990s is the earliest the NAE mission could begin. The scientific motivation, instrument concept, mission concept and expected results, and status and plans for the NAE are presented.
Techniques and software are discussed for generating grids about a high-speed civil transport configuration. The configuration is defined by a computer-aided design system in wing, fuselage, tail and engine-nacelle components. Grid topology and the surfaces outlining the blocks of the topology are computed with interactive software. The volume grid is computed using software based on transfinite interpolation and Lagrangian blending functions. Several volume grids for inviscid and viscous flow have been generated using this system of codes. Demonstration flowfields around this vehicle are described.
Proposed scheme under development for transmission of vector-quantized digital video images, vector quantizer codebook updated to adapt quantizer to changing signal statistics. Intended to be realized with electronic neural network. Codebook, which consists of patterns constituting video images, will undergo training during operation and scheme will develop codebooks ordered during training. System enables coding more compact, more immune to noise, and supports variable rate compression.
An integrated system for the multidisciplinary analysis and optimization of airframe and propulsion design parameters is being developed. This system is known as IPAS, the Integrated Propulsion/Airframe Analysis System. The traditional method of analysis is one in which the propulsion system analysis is loosely coupled to the overall mission performance analysis. This results in a time consuming iterative process. First, the engine is designed and analyzed. Then, the results from this analysis are used in a mission analysis to determine the overall aircraft performance. The results from the mission analysis are used as a guide as the engine is redesigned and the entire process repeated. In IPAS, the propulsion system, airframe, and mission are closely coupled. The propulsion system analysis code is directly integrated into the mission analysis code. This allows the propulsion design parameters to be optimized along with the airframe and mission design parameters, significantly reducing the time required to obtain an optimized solution.
A new nuclear electric propulsion (NEP) systems analysis code is discussed. The new code is modular and consists of a driver code and various subsystem models. The code models five different subsystems: (1) reactor/shield; (2) power conversion; (3) heat rejection; (4) power management and distribution (PMAD); and (5) thrusters. The code optimizes for the following design criteria: minimum mass; minimum radiator area; and low mass/low area. The code also optimizes the following parameters: separation distance; temperature ratio; pressure ratio; and transmission frequency. The discussion is presented in vugraph form.
An integrated system for the multidisciplinary analysis and optimization of airframe and propulsion design parameters is being developed. This system is known as IPAS, the Integrated Propulsion/Airframe Analysis System. The traditional method of analysis is one in which the propulsion system analysis is loosely coupled to the overall mission performance analysis. This results in a time consuming iterative process. First, the engine is designed and analyzed. Then, the results from this analysis are used in a mission analysis to determine the overall aircraft performance. The results from the mission analysis are used as a guide as the engine redesigned and the entire process repeated. In IPAS, the propulsion system, airframe, and mission are closely coupled. The propulsion system analysis code is directly integrated into the mission analysis code. This allows the propulsion design parameters to be optimized along with the airframe and mission design parameters, significantly reducing the time required to obtain an optimized solution.
A series of experiments that were performed on the Rocky 3 robot is described. Rocky 3 is a small autonomous rover capable of navigating through rough outdoor terrain to a predesignated area, searching that area for soft soil, acquiring a soil sample, and depositing the sample in a container at its home base. The robot is programmed according to a reactive behavior control paradigm using the ALFA programming language. This style of programming produces robust autonomous performance while requiring significantly less computational resources than more traditional mobile robot control systems. The code for Rocky 3 runs on an eight bit processor and uses about ten k of memory.
This research program has successfully demonstrated a new target label architecture that allows a microcomputer to determine the position, orientation, and identity of an object. It contains a CAD-like database with specific geometric information about the object for approach, grasping, and docking maneuvers. Successful demonstrations were performed selecting and docking an ORU box with either of two ORU receptacles. Small, but significant differences were seen in the two camera types used in the program, and camera sensitive program elements have been identified. The software has been formatted into a new co-autonomy system which provides various levels of operator interaction and promises to allow effective application of telerobotic systems while code improvements are continuing.
A computational fluid dynamics (CFD) technique is employed to solve aeroacoustics problems on massively parallel computers. The algorithm is based on a 4th order accurate central finite difference and 4th order accurate 4-stage Runge-Kutta time integration method that solves the 3-D full Navier-Stokes/Euler equations on a curvilinear coordinate system. The code has been developed to predict noise radiation from ducted fans. A specific application of this code is made here to the oscillating circular piston problem (Workshop Category 4, Problem 2) by solving the full Euler equations with nonreflecting boundary conditions in the axisymmetric mode. The features of the code that apply to this particular problem are described in this paper.
Recent experience using ANOPP to predict turbofan engine flyover noise suggests that it over-predicts overall EPNL by a significant amount. An improvement in this prediction method is desired for system optimization and assessment studies of advanced UHB engines. An assessment of the ANOPP fan inlet, fan exhaust, jet, combustor, and turbine noise prediction methods is made using static engine component noise data from the CF6-8OC2, E(3), and QCSEE turbofan engines. It is shown that the ANOPP prediction results are generally higher than the measured GE data, and that the inlet noise prediction method (Heidmann method) is the most significant source of this overprediction. Fan noise spectral comparisons show that improvements to the fan tone, broadband, and combination tone noise models are required to yield results that more closely simulate the GE data. Suggested changes that yield improved fan noise predictions but preserve the Heidmann model structure are identified and described. These changes are based on the sets of engine data mentioned, as well as some CFM56 engine data that was used to expand the combination tone noise database. It should be noted that the recommended changes are based on an analysis of engines that are limited to single stage fans with design tip relative Mach numbers greater than one.
The Aircraft Noise Predication Program (ANOPP) is an industry-wide tool used to predict turbofan engine flyover noise in system noise optimization studies. Its goal is to provide the best currently available methods for source noise prediction. As part of a program to improve the Heidmann fan noise model, models for fan inlet and fan exhaust noise suppression estimation that are based on simple engine and acoustic geometry inputs have been developed. The models can be used to predict sound power level suppression and sound pressure level suppression at a position specified relative to the engine inlet.