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At least 91 records · Page 5

User's manual for two dimensional FDTD version TEA and TMA codes for scattering from frequency-independent dielectric materials

The Penn State Finite Difference Time Domain Electromagnetic Scattering Code Versions TEA and TMA are two dimensional electromagnetic scattering codes based on the Finite Difference Time Domain Technique (FDTD) first proposed by Yee in 1966. The supplied version of the codes are two versions of our current FDTD code set. This manual provides a description of the codes and corresponding results for the default scattering problem. The manual is organized into eleven sections: introduction, Version TEA and TMA code capabilities, a brief description of the default scattering geometry, a brief description of each subroutine, a description of the include files (TEACOM.FOR TMACOM.FOR), a section briefly discussing scattering width computations, a section discussing the scattering results, a sample problem setup section, a new problem checklist, references, and figure titles.

Beggs, John H.↗

Rapid Assessment of Agility for Conceptual Design Synthesis

This project consists of designing and implementing a real-time graphical interface for a workstation-based flight simulator. It is capable of creating a three-dimensional out-the-window scene of the aircraft's flying environment, with extensive information about the aircraft's state displayed in the form of a heads-up-display (HUD) overlay. The code, written in the C programming language, makes calls to Silicon Graphics' Graphics Library (GL) to draw the graphics primitives. Included in this report is a detailed description of the capabilities of the code, including graphical examples, as well as a printout of the code itself

Biezad, Daniel J.↗

Capabilities of the Natural Environments Branch at NASA's Marshall Space Flight Center, Revised 2009

The Natural Environment Branch at NASA's Marshall Space Flight Center (MSFC) has the responsibility to provide natural environments engineering support to programs and projects. The Natural Environments Branch is responsible for natural environments definitions, modeling, database development, and analytical assessments of effects. Natural Environments Branch personnel develop requirements for flight projects and provide operational support for space and launch vehicle systems. To accomplish these responsibilities, models and analytical tools have been developed in the areas of planetary atmospheres, meteoroids, ionizing radiation, plasmas and ionospheres, magnetic and gravitational fields, spacecraft charging modeling, and radiation effects on electronic parts. This paper will build on a previous paper published in 2006 and provide updated descriptions of the capabilities within the Natural Environments Branch1. Updates describing improvements and new releases of several analytical tools and models will be presented. Separate sections will specifically describe modifications in the Meteoroid Engineering Model (MEM), and the Marshall Solar Activity Future Estimation (MSAFE) capabilities.

Edwards, David L.↗

Life science research objectives and representative experiments for the space station

A workshop was convened to develop hypothetical experiments to be used as a baseline for space station designer and equipment specifiers to ensure responsiveness to the users, the life science community. Sixty-five intra- and extramural scientists were asked to describe scientific rationales, science objectives, and give brief representative experiment descriptions compatible with expected space station accommodations, capabilities, and performance envelopes. Experiment descriptions include hypothesis, subject types, approach, equipment requirements, and space station support requirements. The 171 experiments are divided into 14 disciplines.

Johnson, Catherine C.↗

Results from teleoperated free-flying spacecraft simulations in the Martin Marietta space operations simulator lab

To augment the capabilities of the Space Transportation System, NASA has funded studies and developed programs aimed at developing reusable, remotely piloted spacecraft and satellite servicing systems capable of delivering, retrieving, and servicing payloads at altitudes and inclinations beyond the reach of the present Shuttle Orbiters. Since the mid 1970's, researchers at the Martin Marietta Astronautics Group Space Operations Simulation (SOS) Laboratory have been engaged in investigations of remotely piloted and supervised autonomous spacecraft operations. These investigations were based on high fidelity, real-time simulations and have covered a wide range of human factors issues related to controllability. Among these are: (1) mission conditions, including thruster plume impingements and signal time delays; (2) vehicle performance variables, including control authority, control harmony, minimum impulse, and cross coupling of accelerations; (3) maneuvering task requirements such as target distance and dynamics; (4) control parameters including various control modes and rate/displacement deadbands; and (5) display parameters involving camera placement and function, visual aids, and presentation of operational feedback from the spacecraft. This presentation includes a brief description of the capabilities of the SOS Lab to simulate real-time free-flyer operations using live video, advanced technology ground and on-orbit workstations, and sophisticated computer models of on-orbit spacecraft behavior. Sample results from human factors studies in the five categories cited above are provided.

Hartley, Craig S.↗

Remote manipulator dynamic simulation

A simulator to generate the real time visual scenes required to perform man in the loop investigations of remote manipulator application and design concepts for the space shuttle is described. The simulated remote manipulator consists of a computed display system that uses a digital computer, the electronic scene generator, an operator's station, and associated interface hardware. A description of the capabilities of the implemented simulation is presented. The mathematical models and programs developed for the simulation are included.

Wild, E. C.↗

The finite element method in low speed aerodynamics

The finite element procedure is shown to be of significant impact in design of the 'computational wind tunnel' for low speed aerodynamics. The uniformity of the mathematical differential equation description, for viscous and/or inviscid, multi-dimensional subsonic flows about practical aerodynamic system configurations, is utilized to establish the general form of the finite element algorithm. Numerical results for inviscid flow analysis, as well as viscous boundary layer, parabolic, and full Navier Stokes flow descriptions verify the capabilities and overall versatility of the fundamental algorithm for aerodynamics. The proven mathematical basis, coupled with the distinct user-orientation features of the computer program embodiment, indicate near-term evolution of a highly useful analytical design tool to support computational configuration studies in low speed aerodynamics.

Baker, A. J.↗

Multipurpose interactive NASA information system

Multipurpose Interactive NASA Information System (MINIS) is data management system capable of retrieving descriptive data from LANDSAT photos. General enough to be used with other user-defined data bases, interactive data management and information retrieval system was especially developed for small and medium-sized computers. It uses free-form data base that allows one to create entirely new and different data bases and to control format of output products.

Hill, J. M.↗

A modular multiple use system for precise time and frequency measurement and distribution

A modular CAMAC based system is described which was developed to meet a variety of precise time and frequency measurement and distribution needs. The system was based on a generalization of the dual mixer concept. By using a 16 channel 100 ns event clock, the system can intercompare the phase of 16 frequency standards with subpicosecond resolution. The system has a noise floor of 26 fs and a long term stability on the order of 1 ps or better. The system also used a digitally controlled crystal oscillator in a control loop to provide an offsettable 5 MHz output with subpicosecond phase tracking capability. A detailed description of the system is given including theory of operation and performance. A method to improve the performance of the dual mixer technique is discussed when phase balancing of the two input ports cannot be accomplished.

Reinhardt, V. S.↗

An axial flow research compressor facility designed for flow measurement in rotor passages

An axial flow research compressor facility, which is designed for relative flow measurement, is described in this paper. The facility has a rotating probe traverse mechanism which is capable of traversing hot wire, pitot and other probes at 0.09 deg intervals across the rotor blade passage. The data transmission system includes rotating transducers, pressure transfer device, ten-channel mercury slip ring unit, scanivalve, etc. The instrumentation includes on-line data processing capability. A brief description of probes used as well as some typical data on the rotor blade static pressure, rotor endwall flow and rotor wake characteristics are given in the paper.

Lakshminarayana, B.↗

Computer program for nonlinear static stress analysis of shuttle thermal protection system: User's manual

User documentation is presented for a computer program which considers the nonlinear properties of the strain isolator pad (SIP) in the static stress analysis of the shuttle thermal protection system. This program is generalized to handle an arbitrary SIP footprint including cutouts for instrumentation and filler bar. Multiple SIP surfaces are defined to model tiles in unique locations such as leading edges, intersections, and penetrations. The nonlinearity of the SIP is characterized by experimental stress displacement data for both normal and shear behavior. Stresses in the SIP are calculated using a Newton iteration procedure to determine the six rigid body displacements of the tile which develop reaction forces in the SIP to equilibrate the externally applied loads. This user documentation gives an overview of the analysis capabilities, a detailed description of required input data and an example to illustrate use of the program.

Giles, G. L.↗

DSN test support system, Mark IV-85

As part of the network consolidation program, DSN test and training system, Mark III-77, will be upgraded during the Mark IVA implementation. This upgraded system is referred to as the DSN test support system, Mark IV-85. Descriptions and functional capabilities that exist or will be implemented in the subsystems which comprise the DSN test support system are provided.

Falin, B. W.↗

Shuttle derived vehicle analysis solid booster unmanned launch vehicle concept definition study, volume 2

The technical effort associated with the selection and definition of the recommended SRB-X concept is documented. Included are discussions concerning the trades leading to the selected concept, the analysis that established the concept's basic subsystem characteristics, selected configuration description and performance capabilities, launch site operations and facility needs, development schedule, cost characteristics, risk assessment, and a cursory comparison with other launch systems.

Source record↗

Fuels research studies at NASA Lewis

Fuels research studies carried out in a variety of areas related to aviation propulsion, ground transportation, and stationary power generation systems are discussed. The major efforts are directed to studies on fuels for jet aircraft. These studies involve fuels preparation, fuels analysis, and fuel quality evaluations. The scope and direction of research activities in these areas is discussed, descriptions of Lewis capabilities and facilities given, and results of recent research efforts reported.

Antoine, A. C.↗

Numerical modelling of cryogenic propellant behavior in low-G

A partial survey is presented of recent research, sponsored by the NASA Lewis Research Center, into the computational modelling of cryogenic propellant behavior in a low gravity environment. This presentation is intended to provide insight into some of the specific problems being studied and into how these studies are part of an integrated plan to develop predictive capabilities. A brief description of the computational models developed to analyze jet induced mixing in cryogenic propellant tankage is presented along with representative results. Similar information is presented for a recent examination of on-orbit self-pressurization. A study of propellant reorientation has recently been initiated and preliminary results are included. The presentation concludes with a list of ongoing efforts and projected goals.

Hochstein, John I.↗

Multiprocessor architecture: Synthesis and evaluation

The goal is to remove the influence of the choice of algorithm used for a particular application and to remove the effects of the high-level language and the efficiency of the program. The study concentrates on only those characteristics of the structure of the architecture. The structure of the architecture is defined to include those parameters that distinguish an architectural design at the diagram level. For example, the interconnection network plays an integral part in such a description while the capabilities of the individual processing elements, while crucial to the execution of the program, are not represented in the diagram.

Standley, Hilda M.↗

Control/structure interaction design methodology

The Control Structure Interaction Program is a technology development program for spacecraft that exhibit interactions between the control system and structural dynamics. The program objectives include development and verification of new design concepts (such as active structure) and new tools (such as a combined structure and control optimization algorithm) and their verification in ground and possibly flight test. The new CSI design methodology is centered around interdisciplinary engineers using new tools that closely integrate structures and controls. Verification is an important CSI theme and analysts will be closely integrated to the CSI Test Bed laboratory. Components, concepts, tools and algorithms will be developed and tested in the lab and in future Shuttle-based flight experiments. The design methodology is summarized in block diagrams depicting the evolution of a spacecraft design and descriptions of analytical capabilities used in the process. The multiyear JPL CSI implementation plan is described along with the essentials of several new tools. A distributed network of computation servers and workstations was designed that will provide a state-of-the-art development base for the CSI technologies.

Briggs, Hugh C.↗