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  • 11
    Publication Date: 2019-06-28
    Description: This paper concerns the dynamic modeling and control of multibody, open-chained, structurally flexible, mechanical systems where the bodies are connected by revolute joints. The equations of motion are formulated based on a matrix form of Lagrange's equations for inertial quasi-coordinates. Each body is treated as a substructure of the system. For the purposes of simulation and control, the equations of motion are separated into two sets of equations using a perturbation approach: one to describe large rigid-body motions of the articulated system and the other to describe small linear motions of the bodies about the large motions. A biologically natural control strategy is used for vibration suppression and tracking the prescribed motion.
    Keywords: CYBERNETICS
    Type: In: Dynamics and control of large structures; Proceedings of the 8th VPI&SU Symposium, Blacksburg, VA, May 6-8, 1991 (A93-29328 10-63); p. 119-131.
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  • 12
    Publication Date: 2019-06-28
    Description: This paper is concerned with the derivation of the equations of motion for the Spacecraft Control Laboratory Experiment (SCOLE). For future reference, the equations of motion of a similar structure orbiting the earth are also derived. The structure is assumed to undergo large rigid-body maneuvers and small elastic deformations. A perturbation approach is presented where the quantities defining the rigid-body maneuver are assumed to be relatively large, with the elastic deformations and deviations from the rigid-body maneuver being relatively small. The perturbation equations have the form of linear, non-self-adjoint equations with time-dependent coefficients. An active control technique can then be formulated to permit maneuvering of the spacecraft and simultaneously suppressing the elastic vibration.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
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  • 13
    Publication Date: 2019-06-28
    Description: Structural temperatures were measured on a hypersonic wing test structure during a heating test that simulated a Mach 8 thermal environment. Measured data are compared to design calculations and temperature predictions obtained from a finite-difference thermal analysis.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-85918 , H-1271 , A-85137 , NAS 1.15:85918
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  • 14
    Publication Date: 2019-06-28
    Description: Equations of motion, control strategy, perturbation, rigid-body maneuvers, quasi-modal equations, and vibration control are discussed for flexible spacecraft.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA. Marshall Space Flight Center Structural Dynamics and Control Interaction of Flexible Structures; p 867-880
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  • 15
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    In:  Other Sources
    Publication Date: 2019-06-28
    Description: This paper is concerned with the simultaneous maneuver and vibration control of the Spacecraft Control Laboratory Experiment (SCOLE). Summaries of the derivation of the equations of motion and of a perturbation method permitting a maneuver strategy independent of the vibration control are presented. Some of the problems encountered in dynamical modeling of a flexible spacecraft in an earth-based laboratory are high-lighted and solved. Numerical results demonstrating rotational maneuvers of the SCOLE model are included.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 86-1993
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  • 16
    Publication Date: 2019-06-28
    Description: The derivation of the equations describing the vibration of a flexible spacecraft is presented in the context of a perturbation method permitting a maneuver strategy independent of the vibration control. A straightforward open-loop minimum-time rotational maneuver strategy is developed for the spacecraft regarded as a rigid body. Actuator dynamics are considered in the formulation. A maneuver force distribution is developed which excites the least amount of elastic deformation of the flexible parts of the spacecraft. An efficient technique for simulating structural vibrations during a maneuver is presented. Numerical results demonstrate the maneuver strategy and highlight the vibration caused by rotational maneuvers.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 86-0906
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  • 17
    Publication Date: 2016-06-07
    Description: A structural performance and resizing finite element thermal analysis computer program was used in the reentry heat transfer analysis of the space shuttle. Two typical wing cross sections and a midfuselage cross section were selected for the analysis. The surface heat inputs to the thermal models were obtained from aerodynamic heating analyses, which assumed a purely turbulent boundary layer, a purely laminar boundary layer, separated flow, and transition from laminar to turbulent flow. The effect of internal radiation was found to be quite significant. With the effect of the internal radiation considered, the wing lower skin temperature became about 39 C (70 F) lower. The results were compared with fight data for space transportation system, trajectory 1. The calculated and measured temperatures compared well for the wing if laminar flow was assumed for the lower surface and bay one upper surface and if separated flow was assumed for the upper surfaces of bays other than bay one. For the fuselage, good agreement between the calculated and measured data was obtained if laminar flow was assumed for the bottom surface. The structural temperatures were found to reach their peak values shortly before touchdown. In addition, the finite element solutions were compared with those obtained from the conventional finite difference solutions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Langley Research Center Computational Aspects of Heat Transfer in Struct.; p 295-325
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  • 18
    Publication Date: 2016-06-07
    Description: Surface heating rates and surface temperatures for a space shuttle reentry profile were calculated for two wing cross sections and one fuselage cross section. Heating rates and temperatures at 12 locations on the wing and 6 locations on the fuselage are presented. The heating on the lower wing was most severe, with peak temperatures reaching values of 1240 C for turbulent flow and 900 C for laminar flow. For the fuselage, the most severe heating occured on the lower glove surface where peak temperatures of 910 C and 700 C were calculated for turbulent flow and laminar flow, respectively. Aluminum structural temperatures were calculated using a finite difference thermal analyzer computer program, and the predicted temperatures are compared to measured flight data. Skin temperatures measured on the lower surface of the wing and bay 1 of the upper surface of the wing agreed best with temperatures calculated assuming laminar flow. The measured temperatures at bays two and four on the upper surface of the wing were in quite good agreement with the temperatures calculated assuming separated flow. The measured temperatures on the lower forward spar cap of bay four were in good agreement with values predicted assuming laminar flow.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Langley Research Center Computational Aspects of Heat Transfer in Struct.; p 271-294
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  • 19
    Publication Date: 2019-05-29
    Description: Aerodynamic heating analysis of X-15 aircraft in flight
    Keywords: AIRCRAFT
    Type: NASA-TM-X-638
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  • 20
    Publication Date: 2019-05-24
    Description: Information bandwidth reduction for analog television signals - Description of multiple interlace system
    Keywords: COMMUNICATIONS
    Type: NASA-CR-65034 , P63-90
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