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  • 1
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    Parameter identification of material constants in a composite shell structure (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: One of the basic requirements in engineering analysis is the development of a mathematical model describing the system. Frequently comparisons with test data are used as a measurement of the adequacy of the model. An attempt is typically made to update or improve the model to provide a test verified analysis tool. System identification provides a systematic procedure for accomplishing this task. The terms system identification, parameter estimation, and model correlation all refer to techniques that use test information to update or verify mathematical models. The goal of system identification is to improve the correlation of model predictions with measured test data, and produce accurate, predictive models. For nonmetallic structures the modeling task is often difficult due to uncertainties in the elastic constants. A finite element model of the shell was created, which included uncertain orthotropic elastic constants. A modal survey test was then performed on the shell. The resulting modal data, along with the finite element model of the shell, were used in a Bayes estimation algorithm. This permitted the use of covariance matrices to weight the confidence in the initial parameter values as well as confidence in the measured test data. The estimation procedure also employed the concept of successive linearization to obtain an approximate solution to the original nonlinear estimation problem.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: JPL, Model Determination for Large Space Systems Workshop, Volume 1; p 331-372
    Format: text
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  • 2
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    Nonlinear modeling, identification and estimation of slew induced structural deformation (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: This proposal discusses a new nonlinear, nonparametric method for off-line modeling and on-line estimation of the deformation of a flexible structure undergoing rapid retargeting maneuvers. In these circumstances, the structural stiffness and damping coefficients depend on the angular acceleration omega(dot), the angular rate omega, and the square of the angular rate omega. In the single axis case, the excitation of the structure is represented by the vector u(exp T) = (omega(dot), omega(exp 2), 2(omega)), to which the structural dynamics responds as a 'bilinear' (i.e., parametrically excited) system. A similar technique for multiaxial rotations yields a bilinear model with respect to matrix valued excitations. Three methods of estimation and modeling are described in this proposal to achieve deformation state determination: (1) a method based on a feedback linearized procedure which gives an estimate of the state by means of observers installed in the deformable body; (2) off-line modeling of the deformation state of the structure by means of topological interpolators; and (3) an on-line structural state estimation method based on a combination of the two previous techniques.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: JPL, Model Determination for Large Space Systems, Volume 3; 17 p
    Format: text
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  • 3
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    Space truss assembly using teleoperated manipulators (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Teleoperator experiments were conducted which have demonstrated that a realistic, complex task, typical of those accomplished on-orbit by EVA astronauts, can be done in a smooth, timely manner with manipulators remotely controlled by humans. The real concerns were: (1) do manipulators have sufficient dexterity for these tasks, (2) can sufficient information from the remote site be provided to permit adequate teleoperator control, (3) can reasonable times relative to EVA times be achieved, (4) can the task be completed without frequent and/or damaging impacts among the task components and the manipulators? Positive answers were found to all of these concerns. Tasks times, operator fatigue, and smoothness of operation could be improved by designing the task components and the manipulators for greater compatibility. The data recorded supplements a data base of performance metrics for the same task done in the water immersion training facility as well as space flight and provides management with an objective basis for deciding how and where to apply manipulators in space.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA, Goddard Space Flight Center, Proceedings of 1987 Goddard Conference on Space Applications of Artificial Intelligence (AI) and Robotics; 18 p
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  • 4
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    Space station docking mechanism dynamic testing (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A prototype docking mechanism for the Space Station was designed and fabricated for NASA. This docking mechanism is actively controlled and uses a set of electromechanical actuators for alignment and load attenuation. Dynamic tests are planned using the Marshall Space Flight Center's 6-DOF Motion Simulator. The proposed tests call for basic functionality verification as well as complete hardware-in-the-loop docking dynamics simulations.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA, Goddard Space Flight Center, 15th Space Simulation Conference: Support the Highway to Space Through Testing; p 168-175
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  • 5
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    Utilization of spray on foam insulation for manned and unmanned spacecraft and structures (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The idea of using spray-on foam insulation as a passive thermal and micrometeorite protection system is explored. The benefits of applying an exterior coating of foam insulation can be: (1) the foam can provide a thermally stable shield that can assist in reducing the strain on traditional space radiator systems and can also act as a passive thermal guard, allowing a greater fault tolerance if the standard system should fail; (2) the foam can act as an ablative shell diminishing the effects of natural and manmade debris striking the structure; (3) the foam is lightweight - about 1/2 ounce per sq ft; (4) the foam is low cost and easy to maintain; and (5) the foam is a stable material that does not react when exposed to earth or lunar environments.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
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  • 6
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    Control law synthesis and optimization software for large order aeroservoelastic systems (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A flexible aircraft or space structure with active control is typically modeled by a large-order state space system of equations in order to accurately represent the rigid and flexible body modes, unsteady aerodynamic forces, actuator dynamics and gust spectra. The control law of this multi-input/multi-output (MIMO) system is expected to satisfy multiple design requirements on the dynamic loads, responses, actuator deflection and rate limitations, as well as maintain certain stability margins, yet should be simple enough to be implemented on an onboard digital microprocessor. A software package for performing an analog or digital control law synthesis for such a system, using optimal control theory and constrained optimization techniques is described.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Proceedings of the Workshop on Computational Aspects in the Control of Flexible Systems, Part 2; p 693-707
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  • 7
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    Near-optimal strategies for sub-decimeter satellite tracking with GPS (1986)
    In:  Other Sources
    Details
    Publication Date: 2013-08-29
    Description: Decimeter tracking of low Earth orbiters using differential Global Positioning System (GPS) techniques is discussed. A precisely known global network of GPS ground receivers and a receiver aboard the user satellite are needed, and all techniques simultaneously estimate the user and GPS satellite orbits. Strategies include a purely geometric, a fully dynamic, and a hybrid strategy. The last combines dynamic GPS solutions with a geometric user solution. Two powerful extensions of the hybrid strategy show the most promise. The first uses an optimized synthesis of dynamics and geometry in the user solution, while the second uses a gravity adjustment method to exploit data from repeat ground tracks. These techniques promise to deliver subdecimeter accuracy down to the lowest satellite altitudes.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: ESA Proceedings of the Second International Symposium on Spacecraft Flight Dynamics; p 233-238
    Format: text
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  • 8
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    United States Air Force Academy get-away-special flexible beam experiment (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Department of Astronautics at the United States Air Force Academy is currently planning to fly an experiment in a NASA Get-Away-Special (GAS) canister. The experiment was named the flex beam experiment. The primary technical objective of the flex beam experiment is to measure the damping of a thin beam in the vacuum and zero G environment of space. By measuring the damping in space, it is hoped to determine the amount of damping the beam normally experiences due to the gravitational forces present on Earth. This will allow validation of models which predict the dynamics of thin beams in the space environment. The experiment will also allow the Academy to develop and improve its ability to perform experiments within the confines of a NASA GAS canister. Several experiments, of limited technical difficulty, were flown by the Academy. More complex experiments are currently planned and it is hoped to learn techniques with each space shuttle flight.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA, Langley Research Center, NASA(DOD Controls-Structures Interaction Technology 1989; p 459-47
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  • 9
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    Design and dynamic testing of an instrumented spacecraft component (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Details relating to the design and subsequent vibration and shock tests of a spacecraft component for a severe vibration and shock environment are presented. The design process and analysis method involve the use of finite element analysis coupled with the Modal Strain Energy method with risk graphs to determine the adequacy of the design. The vibration levels experienced by box parts are reduced by the application of passive constrained layer viscoelastic treatments that significantly improve component reliability. All significant internal components were fully instrumented in both the random vibration and shock tests, the latter being done on a mechanical impact pyro simulator. Correlation between analysis and test data is good, validating the modeling and analysis techniques.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA. Marshall Space Flight Center, The 58th Shock and Vibration Symposium, Volume 2; p 93-102
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  • 10
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    Assembly of user systems at Space Station (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: The technical and programmatic benefits of on-orbit assembly are outlined. Operational and automation considerations relating to on-orbit assembly are reviewed. Space Station capabilities for orbital assembly are discussed.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: ESA. Proceedings of the 1st European In-Orbit Operations Technology Symposium; p 39-45
    Format: text
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