SIMULATION F TH5 RESTRICTED THREE-BODY PROBLEM USING THE TRICE-PB250 SYSTEM
Integration of the restricted three body problem using the trice-pb250 system with the selection of appropriate variables and programming techniques
THREE-BODY PROBLEM↗
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Results for “variable selection”
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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Nonlinear models for estimating GSFC travel requirements
A methodology is presented for estimating travel requirements for a particular period of time. Travel models were generated using nonlinear regression analysis techniques on a data base of FY-72 and FY-73 information from 79 GSFC projects. Although the subject matter relates to GSFX activities, the type of analysis used and the manner of selecting the relevant variables would be of interest to other NASA centers, government agencies, private corporations and, in general, any organization with a significant travel budget. Models were developed for each of six types of activity: flight projects (in-house and out-of-house), experiments on non-GSFC projects, international projects, ART/SRT, data analysis, advanced studies, tracking and data, and indirects.
Buffalano, C.↗
SSME/side loads analysis for flight configuration, revision A
This document describes the dynamic loads analysis accomplished for the Space Shuttle Main Engine (SSME) considering the side load excitation associated with transient flow separation on the engine bell during ground ignition. The results contained herein pertain only to the flight configuration. A Monte Carlo procedure was employed to select the input variables describing the side load excitation and the loads were statistically combined. This revision includes an active thrust vector control system representation and updated orbiter thrust structure stiffness characteristics. No future revisions are planned but may be necessary as system definition and input parameters change.
Holland, W.↗
Signal conditioner test set
A system was developed for testing components contained in a signal conditioning module with a transistor and capacitor included in a circuit. The system includes a housing with a socket into which the module to be tested is plugged. A test switch is provided for selectively connecting a variable load to either a transistor or capacitor in the circuit for testing the operation. A signal generating circuit is provided for generating signals for use in testing the components of the module.
Houck, W. H.↗
A decision and control multi-axis pilot model based on an urgency for action concept
An all digital multiple axis, multiple input, multiple output pilot model flies five different tasks in aircraft of different classes while encountering turbulence represented by the Dryden spectral model. Six degree of freedom linearized aircraft equations of motion are used together with a generalized stability augmentation system. The pilot model consists of two parts: (1) a decision maker, and (2) a control action implementer. This decision maker selects the critical variable and predicts the error at action implementation. The control action implementer decides the magnitude of control to be applied and applies it. This system has been successfully compared with hybrid/analog man in the loop simulations of the F-5, A-7, T-33, and 707 aircraft, thus validating the all digital simulation and the decision and control pilot model.
Pollard, J. J.↗
A reliability-based cost effective fail-safe design procedure
The authors have developed a methodology for cost-effective fatigue design of structures subject to random fatigue loading. A stochastic model for fatigue crack propagation under random loading has been discussed. Fracture mechanics is then used to estimate the parameters of the model and the residual strength of structures with cracks. The stochastic model and residual strength variations have been used to develop procedures for estimating the probability of failure and its changes with inspection frequency. This information on reliability is then used to construct an objective function in terms of either a total weight function or cost function. A procedure for selecting the design variables, subject to constraints, by optimizing the objective function has been illustrated by examples. In particular, optimum design of stiffened panel has been discussed.
Hanagud, S.↗
Optimal design and evaluation criteria for acoustic emission pulse signature analysis
Successful pulse recording and evaluation is strongly dependent on the instrumentation system selected and the method of analyzing the pulse signature. The paper studies system design, signal analysis techniques, and interdependences with a view toward defining optimal approaches to pulse signal analysis. For this purpose, the instrumentation system is modeled, and analytical pulses, representative of the types of acoustic emissions to be distinguished are passed through the system. Particular attention is given to comparing frequency spectrum analysis and deconvolution referred to as time domain reconstruction of the pulse or pulse train. The possibility of optimal transducer-filter system parameters is investigated. Deconvolution of a pulse is shown to be a superior approach for transient pulse analysis. Reshaping of a transducer output back to the original input pulse is possible and gives an accurate representation of the generating pulse in the time domain. Any definable transducer and filter system can be used for measurement of pulses by means of the deconvolution method. Selection of design variables for general usage is discussed.
Houghton, J. R.↗
Computer program for prediction of capture maneuver probability for an on-off reaction controlled upper stage
A FORTRAN coded computer program which computes the capture transient of a launch vehicle upper stage at the ignition and/or separation event is presented. It is for a single degree-of-freedom on-off reaction jet attitude control system. The Monte Carlo method is used to determine the statistical value of key parameters at the outcome of the event. Aerodynamic and booster induced disturbances, vehicle and control system characteristics, and initial conditions are treated as random variables. By appropriate selection of input data pitch, yaw and roll axes can be analyzed. Transient response of a single deterministic case can be computed. The program is currently set up on a CDC CYBER 175 computer system but is compatible with ANSI FORTRAN computer language. This routine has been used over the past fifteen (15) years for the SCOUT Launch Vehicle and has been run on RECOMP III, IBM 7090, IBM 360/370, CDC6600 and CDC CYBER 175 computers with little modification.
Knauber, R. N.↗
Optical and radio properties of X-ray selected BL Lacertae objects
The eight BL Lac objects from the HEAO 1 A-2 all-sky survey and from the Einstein medium-sensitivity survey (MSS) form a flux-limited complete X-ray selected sample. The optical and radio properties of the MSS BL Lac objects are presented and compared with those of the HEAO 1 A-2 sample and with those of radio-selected BL Lac objects. The X-ray selected BL Lac objects possess smaller polarized fractions and less violent optical variability than radio-selected BL Lac objects. These properties are consistent with the substantial starlight fraction seen in the optical spectra of a majority of these objects. This starlight allows a determination of definite redshifts for two of four MSS BL Lac objects and a probable redshift for a third. These redshifts are 0.2, 0.3, and 0.6. Despite the differences in characteristics between the X-ray selected and radio-selected samples, it is concluded that these eight objects possess most of the basic qualities of BL Lac objects and should be considered members of that class. Moreover, as a class, these X-ray selected objects have the largest ratio of X-ray to optical flux of any active galactic nuclei yet discovered.
Stocke, J. T.↗
Parametric analysis of synthetic aperture radar data for the study of forest stand characteristics
A parametric analysis of a Gulf Coast forest stand was performed using multipolarization, multipath airborne SAR data, and forest plot properties. Allometric equations were used to compute the biomass and basal area for the test plots. A multiple regression analysis with stepwise selection of independent variables was performed. It is found that forest stand characteristics such as biomass, basal area, and average tree height are correlated with SAR data.
Wu, Shih-Tseng↗
The multiple-function multi-input/multi-output digital controller system for the AFW wind-tunnel model
A real time multiple-function digital controller system was developed for the Active Flexible Wing (AFW) Program. The digital controller system (DCS) allowed simultaneous execution of two control laws: flutter suppression and either roll trim or a rolling maneuver load control. The DCS operated within, but independently of, a slower host operating system environment, at regulated speeds up to 200 Hz. It also coordinated the acquisition, storage, and transfer of data for near real time controller performance evaluation and both open- and closed-loop plant estimation. It synchronized the operation of four different processing units, allowing flexibility in the number, form, functionality, and order of control laws, and variability in the selection of the sensors and actuators employed. Most importantly, the DCS allowed for the successful demonstration of active flutter suppression to conditions approximately 26 percent (in dynamic pressure) above the open-loop boundary in cases when the model was fixed in roll and up to 23 percent when it was free to roll. Aggressive roll maneuvers with load control were achieved above the flutter boundary. The purpose here is to present the development, validation, and wind tunnel testing of this multiple-function digital controller system.
Hoadley, Sherwood T.↗
Application of artificial neural networks to the design optimization of aerospace structural components
The application of artificial neural networks to capture structural design expertise is demonstrated. The principal advantage of a trained neural network is that it requires trivial computational effort to produce an acceptable new design. For the class of problems addressed, the development of a conventional expert system would be extremely difficult. In the present effort, a structural optimization code with multiple nonlinear programming algorithms and an artificial neural network code NETS were used. A set of optimum designs for a ring and two aircraft wings for static and dynamic constraints were generated by using the optimization codes. The optimum design data were processed to obtain input and output pairs, which were used to develop a trained artificial neural network with the code NETS. Optimum designs for new design conditions were predicted by using the trained network. Neural net prediction of optimum designs was found to be satisfactory for most of the output design parameters. However, results from the present study indicate that caution must be exercised to ensure that all design variables are within selected error bounds.
Berke, Laszlo↗
Aerodynamic configuration design using response surface methodology analysis
An investigation has been conducted to determine a set of optimal design parameters for a single-stage-to-orbit reentry vehicle. Several configuration geometry parameters which had a large impact on the entry vehicle flying characteristics were selected as design variables: the fuselage fineness ratio, the nose to body length ratio, the nose camber value, the wing planform area scale factor, and the wing location. The optimal geometry parameter values were chosen using a response surface methodology (RSM) technique which allowed for a minimum dry weight configuration design that met a set of aerodynamic performance constraints on the landing speed, and on the subsonic, supersonic, and hypersonic trim and stability levels. The RSM technique utilized, specifically the central composite design method, is presented, along with the general vehicle conceptual design process. Results are presented for an optimized configuration along with several design trade cases.
Engelund, Walter C.↗
NASA/DOD Aerospace Knowledge Diffusion Research Project. Report 30: Computer-Mediated Communication (CMC) and the communication of technical information in aerospace
This research used survey research to examine the use of communication media in general and electronic media specifically in the U.S. aerospace industry. The survey population included 1,006 randomly selected U.S. aerospace engineers and scientists who belong to the American Institute of Aeronautics and Astronautics (AIAA). Survey data were compared with qualitative information obtained from 32 AIAA members in telephone and face-to-face conversations. The Information Processing (IP) model developed by Tushman and Nadler and Daft and Lengel constituted the study's theoretical basis. This research analyzed responses regarding communication methods of U.S. aerospace engineers and scientists who create use and disseminate aerospace knowledge and explored selected contextual environmental variables related to media use and effective performance. The results indicate that uncertainty is significantly reduced in environments when levels of analyzability are high. When uncertainty is high there is significantly more use of electronic media. However no relation was found between overall effectiveness and media use in environments stratified by levels by analyzability or equivocality. The results indicate modest support for the influences of uncertainty and analyzability on electronic media use. Although most respondents reported that electronic networks are important for their work the data suggest that there are sharply disparate levels of use.
Murphy, Daniel J.↗
Optimum Design of Aerospace Structural Components Using Neural Networks
The application of artificial neural networks to capture structural design expertise is demonstrated. The principal advantage of a trained neural network is that it requires a trivial computational effort to produce an acceptable new design. For the class of problems addressed, the development of a conventional expert system would be extremely difficult. In the present effort, a structural optimization code with multiple nonlinear programming algorithms and an artificial neural network code NETS were used. A set of optimum designs for a ring and two aircraft wings for static and dynamic constraints were generated using the optimization codes. The optimum design data were processed to obtain input and output pairs, which were used to develop a trained artificial neural network using the code NETS. Optimum designs for new design conditions were predicted using the trained network. Neural net prediction of optimum designs was found to be satisfactory for the majority of the output design parameters. However, results from the present study indicate that caution must be exercised to ensure that all design variables are within selected error bounds.
Berke, L.↗
GUST LAT Multiwavelength Planning
Because gamma-ray astrophysics profits in powerful ways from multi-wavelength studies, the GLAST Large Area Telescope (LAT) Collaboration has started multiwavelength planning well before the scheduled 2007 launch. Many aspects of this program are of direct interest to observers using VERITAS and other atmospheric Cerenkov telescopes, whose capabilities complement those of GLAST. This talk with describe some of the current developmental concepts for GLAST LAT multiwavelength work, including release of data for transient sources, nearly-continuous monitoring of selected time-variable sources, pulsar timing, follow-on observations for source identification, coordinated blazar campaigns, and cross-calibration with other high-energy telescopes. Although few details are firm at this stage of preparation for GLAST, the LAT Collaboration looks forward to cooperation with a broad cross-section of the multiwave-length community. The GLAST Large Area Telescope is an international effort, with U.S. funding provided by the Department of Energy and NASA.
Thompson, D. J.↗
Preliminary Design of a Manned Nuclear Electric Propulsion Vehicle Using Genetic Algorithms
Nuclear electric propulsion (NEP) vehicles will be needed for future manned missions to Mars and beyond. Candidate designs must be identified for further detailed design from a large array of possibilities. Genetic algorithms have proven their utility in conceptual design studies by effectively searching a large design space to pinpoint unique optimal designs. This research combined analysis codes for NEP subsystems with a genetic algorithm. The use of penalty functions with scaling ratios was investigated to increase computational efficiency. Also, the selection of design variables for optimization was considered to reduce computation time without losing beneficial design search space. Finally, trend analysis of a reference mission to the asteroids yielded a group of candidate designs for further analysis.
Irwin, Ryan W.↗
Using Computational Cognitive Modeling to Diagnose Possible Sources of Aviation Error
We present a computational model of a closed-loop, pilot-aircraft-visual scene-taxiway system created to shed light on possible sources of taxi error. Creating the cognitive aspects of the model using ACT-R required us to conduct studies with subject matter experts to identify experiential adaptations pilots bring to taxiing. Five decision strategies were found, ranging from cognitively-intensive but precise, to fast, frugal but robust. We provide evidence for the model by comparing its behavior to a NASA Ames Research Center simulation of Chicago O'Hare surface operations. Decision horizons were highly variable; the model selected the most accurate strategy given time available. We found a signature in the simulation data of the use of globally robust heuristics to cope with short decision horizons as revealed by errors occurring most frequently at atypical taxiway geometries or clearance routes. These data provided empirical support for the model.
Pilots↗