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At least 739 records · Page 41

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NASA NTRS1981

The dynamics and control of large flexible space structures-IV

The effects of solar radiation pressure as the main environmental disturbance torque were incorporated into the model of the rigid orbiting shallow shell and computer simulation results indicate that within the linear range the rigid modal amplitudes are excited in proportion to the area to mass ratio. The effect of higher order terms in the gravity-gradient torque expressions previously neglected was evaluated and found to be negligible for the size structures under consideration. A graph theory approach was employed for calculating the eigenvalues of a large flexible system by reducing the system (stiffness) matrix to lower ordered submatrices. The related reachability matrix and term rank concepts are used to verify controllability and can be more effective than the alternate numerical rank tests. Control laws were developed for the shape and orientation control of the orbiting flexible shallow shell and numerical results presented.

Bainum, P. M.↗

NASA NTRS2010

CFD Fuel Slosh Modeling of Fluid-Structure Interaction in Spacecraft Propellant Tanks with Diaphragms

Liquid sloshing within spacecraft propellant tanks causes rapid energy dissipation at resonant modes, which can result in attitude destabilization of the vehicle. Identifying resonant slosh modes currently requires experimental testing and mechanical pendulum analogs to characterize the slosh dynamics. Computational Fluid Dynamics (CFD) techniques have recently been validated as an effective tool for simulating fuel slosh within free-surface propellant tanks. Propellant tanks often incorporate an internal flexible diaphragm to separate ullage and propellant which increases modeling complexity. A coupled fluid-structure CFD model is required to capture the damping effects of a flexible diaphragm on the propellant. ANSYS multidisciplinary engineering software employs a coupled solver for analyzing two-way Fluid Structure Interaction (FSI) cases such as the diaphragm propellant tank system. Slosh models generated by ANSYS software are validated by experimental lateral slosh test results. Accurate data correlation would produce an innovative technique for modeling fuel slosh within diaphragm tanks and provide an accurate and efficient tool for identifying resonant modes and the slosh dynamic response.

Sances, Dillon J.↗

NASA NTRS1986

Thermal environment around the Space Shuttle with hot-gas jets for ice suppression

To prevent prelaunch ice formation on the external tank of the Space Shuttle, the final selected approach is to heat the surrounding air with vertical hot-gas jets located at the launch pad. This approach was considerably more cost-effective than other ice suppression methods considered, although its feasibility was not easily discernible due to the complex flowfield interactions. This paper describes how the use of vertical jets was first evaluated with the aid of a computational fluid dynamics (CFD) technique. An existing general-purpose CFD program (PHOENICS) was used to predict the thermal environment around the Shuttle under various jet configurations and wind conditions. The program accounts for effects of buoyancy, turbulence, and structural obstructions in the flowfield. The computed results showed physically plausible and consistent trends. The wind wake effects were found to be significant, and normally resulted in higher temperatures on the leeward side of the tank. High wind conditions were found to be more severe than calm wind conditions. The use of four jets with two different temperatures was identified as a promising option in which the air temperatures were raised sufficiently to prevent ice formation on the external tank, without excessive increase in Orbiter surface temperature. The use of the numerical model also facilitated the selection of test configurations and a test matrix for verifying the approach. Selected results of an experimental verification (by using a 2 percent scale model in a wind tunnel) are also presented.

Singhal, A. K.↗

NASA NTRS1971

Study-simulation of space station dynamics

Matrix algebra translator and executor /MATE/ takes equations describing structural control system environmental interaction problem for flexible spacecraft components and loads them into self programming computer.

Gaitens, M. J.↗

NASA NTRS1979

Experimental Investigation of Launch Vehicle Transient Input Simulation in Payload Tests

The technique of electronically simulating the structural dynamics of a launch vehicle in transient tests of payloads using multiple vibration excitation systems was investigated. The development of computer programs to determine transfer functions, synthesize shaker forcing functions, and control vibration exciters is described. A demonstration test using the techniques was described and results are presented. The evaluation of the potential for applying this technique to large Shuttle payloads is discussed.

Rader, P.↗

NASA NTRS1981

Voyager at Saturn

The spacecraft design and operations and mission results of the Voyager Project are reviewed with particular emphasis on the results of the Saturn encounters. The mission was undertaken by two spacecraft: Voyager 2, launched first on August 20, 1977 on a lower energy trajectory to Jupiter, Saturn, Uranus and Neptune; and Voyager 1, launched on September 5, 1977 on a higher energy trajectory to closer flybys of Jupiter and Saturn. The Voyager spacecraft make use of earlier Mariner and Viking Orbiter design concepts, with additional capabilities for solar independent power, long-range communications and autonomy as well as equipment for the 11 science investigations. The Voyager operations system consists of a ground data system, missions operations system, and support by the Mission Control and Computer Center and Deep Space Network. Among the results of the Jupiter encounter are data concerning the magnetospheric structure and atmospheric dynamics of the planet and the surface features of the Galilean satellites. The encounters with Saturn produced scientific data concerning wind speeds, auroral emissions, and radio emissions from the planet, the fine structure of the previously known and newly discovered rings, the surface features of the satellites and the atmospheric composition and conditions of Titan. Voyager 1 is presently making field and particle measurements on its flight into interstellar space, while Voyager 2 is headed for an encounter with Uranus in January 1986 and Neptune in August 1989.

Heacock, R. L.↗

NASA NTRS1987

Composite mechanics for engine structures

Recent research activities and accomplishments at Lewis Research Center on composite mechanics for engine structures are summarized. The activities focused mainly on developing procedures for the computational simulation of composite intrinsic and structural behavior. The computational simulation encompasses all aspects of composite mechanics, advanced three-dimensional finite-element methods, damage tolerance, composite structural and dynamic response, and structural tailoring and optimization.

Chamis, Christos C.↗

NASA NTRS1989

Composite mechanics for engine structures

Chamis, Christos C.↗

NASA NTRS1991

A Computational and Experimental Investigation of a Three-Dimensional Hypersonic Scramjet Inlet Flow Field

A combined computational and experimental parametric study of the internal aerodynamics of a generic three dimensional sidewall compression scramjet inlet configuration was performed. The study was designed to demonstrate the utility of computational fluid dynamics as a design tool in hypersonic inlet flow fields, to provide a detailed account of the nature and structure of the internal flow interactions, and to provide a comprehensive surface property and flow field database to determine the effects of contraction ratio, cowl position, and Reynolds number on the performance of a hypersonic scramjet inlet configuration.

Holland, Scott Douglas↗

NASA NTRS1993

Autonomous Frequency-Domain System-Identification Program

Autonomous Frequency Domain Identification (AU-FREDI) computer program implements system of methods, algorithms, and software developed for identification of parameters of mathematical models of dynamics of flexible structures and characterization, by use of system transfer functions, of such models, dynamics, and structures regarded as systems. Software considered collection of routines modified and reassembled to suit system-identification and control experiments on large flexible structures.

Yam, Yeung↗

NASA NTRS2007

Engineered Structured Sorbents for the Adsorption of Carbon Dioxide and Water Vapor from Manned Spacecraft Atmospheres: Applications and Modeling 2007/2008

In NASA s Vision for Space Exploration, humans will once again travel beyond the confines of earth s gravity, this time to remain there for extended periods. These forays will place unprecedented demands on launch systems. They must not only blast out of earth s gravity well as during the Apollo moon missions, but also launch the supplies needed to sustain a larger crew over much longer periods. Thus all spacecraft systems, including those for the separation of metabolic carbon dioxide and water from a crewed vehicle, must be minimized with respect to mass, power, and volume. Emphasis is also placed on system robustness both to minimize replacement parts and ensure crew safety when a quick return to earth is not possible. This paper describes efforts to improve on typical packed beds of sorbent pellets by making use of structured sorbents and alternate bed configurations to improve system efficiency and reliability. The development efforts described offer a complimentary approach combining testing of subscale systems and multiphysics computer simulations to characterize the regenerative heating substrates and evaluation of engineered structured sorbent geometries. Mass transfer, heat transfer, and fluid dynamics are included in the transient simulations.

Knox, James C.↗

NASA NTRS2014

FUN3D Manual: 12.5

This manual describes the installation and execution of FUN3D version 12.5, including optional dependent packages. FUN3D is a suite of computational uid dynamics simulation and design tools that uses mixed-element unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables ecient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status.

Biedron, Robert T.↗

NASA NTRS2015

FUN3D Manual: 12.6

This manual describes the installation and execution of FUN3D version 12.6, including optional dependent packages. FUN3D is a suite of computational fluid dynamics simulation and design tools that uses mixed-element unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables efficient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status.

Biedron, Robert T.↗

NASA NTRS2015

FUN3D Manual: 12.7

This manual describes the installation and execution of FUN3D version 12.7, including optional dependent packages. FUN3D is a suite of computational fluid dynamics simulation and design tools that uses mixed-element unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables efficient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status.

Biedron, Robert T.↗

NASA NTRS2015

FUN3D Manual: 12.8

This manual describes the installation and execution of FUN3D version 12.8, including optional dependent packages. FUN3D is a suite of computational fluid dynamics simulation and design tools that uses mixed-element unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables efficient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status.

Biedron, Robert T.↗

NASA NTRS2016

Evaluation of Load Analysis Methods for NASAs GIII Adaptive Compliant Trailing Edge Project

The Air Force Research Laboratory (AFRL), NASA Armstrong Flight Research Center (AFRC), and FlexSys Inc. (Ann Arbor, Michigan) have collaborated to flight test the Adaptive Compliant Trailing Edge (ACTE) flaps. These flaps were installed on a Gulfstream Aerospace Corporation (GAC) GIII aircraft and tested at AFRC at various deflection angles over a range of flight conditions. External aerodynamic and inertial load analyses were conducted with the intention to ensure that the change in wing loads due to the deployed ACTE flap did not overload the existing baseline GIII wing box structure. The objective of this paper was to substantiate the analysis tools used for predicting wing loads at AFRC. Computational fluid dynamics (CFD) models and distributed mass inertial models were developed for predicting the loads on the wing. The analysis tools included TRANAIR (full potential) and CMARC (panel) models. Aerodynamic pressure data from the analysis codes were validated against static pressure port data collected in-flight. Combined results from the CFD predictions and the inertial load analysis were used to predict the normal force, bending moment, and torque loads on the wing. Wing loads obtained from calibrated strain gages installed on the wing were used for substantiation of the load prediction tools. The load predictions exhibited good agreement compared to the flight load results obtained from calibrated strain gage measurements.

Aerodynamic Loads↗

NASA NTRS2016

FUN3D Manual: 12.9

This manual describes the installation and execution of FUN3D version 12.9, including optional dependent packages. FUN3D is a suite of computational fluid dynamics simulation and design tools that uses mixed-element unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables efficient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status.

Biedron, Robert T.↗

NASA NTRS2016

FUN3D Manual: 13.0

This manual describes the installation and execution of FUN3D version 13.0, including optional dependent packages. FUN3D is a suite of computational fluid dynamics simulation and design tools that uses mixed-element unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables efficient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status.

Biedron, Robert T.↗