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  • SPACECRAFT DESIGN, TESTING AND PERFORMANCE  (11)
  • 1
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    An analytical investigation of shape control of large space structures by applied temperatures (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA Journal (ISSN 0001-1452); 23; 450-457
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  • 2
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    Integrated structural electromagnetic shape control of large space anatenna reflectors (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA Journal (ISSN 0001-1452); 27; 814-819
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  • 3
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    Selection of actuator locations for static shape control of large space structures by heuristic integer programing (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Orbiting spacecraft such as large space antennas have to maintain a highly accurate shape to operate satisfactorily. Such structures require active and passive controls to maintain an accurate shape under a variety of disturbances. Methods for the optimum placement of control actuators for correcting static deformations are described. In particular, attention is focused on the case were control locations have to be selected from a large set of available sites, so that integer programing methods are called for. The effectiveness of three heuristic techniques for obtaining a near-optimal site selection is compared. In addition, efficient reanalysis techniques for the rapid assessment of control effectiveness are presented. Two examples are used to demonstrate the methods: a simple beam structure and a 55m space-truss-parabolic antenna.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Computers and Structures (ISSN 0045-7949); 20; 1-3,; 575-582
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  • 4
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    An analytical investigation of shape control of large space structures by applied temperatures (1983)
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    Publication Date: 2018-12-01
    Description: An analytical procedure for the static shape control of flexible space structures subjected to thermal distortions is developed which is based on prescribing temperatures in control elements having much higher coefficients of thermal expansion than the main structure. The temperatures at the control elements are defined so as to minimize the overall thermal distortion of the structure from its ideal shape, and a matrix equation is obtained which can be solved for the set of optimum control temperatures. A formulation of the procedure for continuous structures governed by differential equations and a formulation for discrete (finite element modeled) structures governed by matrix equations are presented. The equations from the continuous formulation are employed for the shape control of a simple beam distorted by nonuniform heating, and the discrete formulation is applied in a general purpose finite-element structural analysis computer program for the shape control of a 750 m radiometer antenna reflector dish subjected to orbital heating. A reduction in thermal distortion by a factor of nearly 50 was obtained with the use of only seven control elements. Results for four different sets of control locations for the antenna are presented in which reductions in distortion of up to a factor of four were obtained.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
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  • 5
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    Integrated structural electromagnetic optimization of large space antenna reflectors (1987)
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    Publication Date: 2019-06-28
    Description: The requirements for extremely precise and powerful large space antenna reflectors have motivated the development of a procedure for shape control of the reflector surface. A mathematical optimization procedure has been developed which improves antenna performance while minimizing necessary shape correction effort. In contrast to previous work which proposed controlling the rms distortion error of the surface thereby indirectly improving antenna performance, the current work includes electromagnetic (EM) performance calculations as an integral part of the control procedure. The application of the procedure to a radiometer design with a tetrahedral truss backup structure demonstrates the potential for significant improvement. The results indicate the benefit of including EM performance calculations in procedures for shape control of large space antenna reflectors.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 87-0824
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  • 6
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    Some aspects of algorithm performance and modeling in transient thermal analysis of structures (1981)
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    Publication Date: 2019-07-13
    Description: The status of an effort to increase the efficiency of calculating transient temperature fields in complex aerospace vehicle structures is described. The advantages and disadvantages of explicit and implicit algorithms are discussed. A promising set of implicit algorithms with variable time steps, known as the GEAR package is described. Four test problems, used for evaluating and comparing various algorithms, have been selected and finite-element models of the configurations are described. These problems include a Space Shuttle frame component, an insulated cylinder, a metallic panel for a thermal protection system, and a model of the Space Shuttle Orbiter wing. Results generally indicate a preference for implicit over explicit algorithms for solution of transient structural heat transfer problems when the governing equations are 'stiff' (typical of many practical problems such as insulated metal structures).
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: ASME PAPER 81-WA/HT-4 , Winter Annual Meeting; Nov 15, 1981 - Nov 20, 1981; Washington, DC
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  • 7
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    The effect of sensor and actuator errors on static shape control for large space structures (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: An analytical study was performed to predict and assess the effect of actuator and sensor errors on the performance of a shape control procedure for flexible space structures using applied temperatures. Approximate formulas were derived for the expected value and variance of the rms distortion ratio (ratio of rms distortions with and without corrections) based on the assumption of zero-mean normally distributed random errors in measured distortions and actuator output temperatures. Studies were carried out for a 55-meter radiometer antenna reflector distorted from its ideal parabolic shape by nonuniform orbital heating. The first study consisted of varying the sensor and actuator errors for the case of 12 actuators and computing the distortion ratio. In the second study, sensor and actuator errors were prescribed and the effect of increasing the number of actuators was evaluated.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-86446 , NAS 1.15:86446 , AIAA/VPI&SU Symp. on Dyn. and Control of Large Struct.; Jun 12, 1985 - Jun 14, 1985; Blacksburg, VA; United States
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  • 8
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    Selection of actuator locations for static shape control of large space structures by heuristic integer programing (1984)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Orbiting spacecraft such as large space antennas have to maintain a highly accurate space to operate satisfactorily. Such structures require active and passive controls to mantain an accurate shape under a variety of disturbances. Methods for the optimum placement of control actuators for correcting static deformations are described. In particular, attention is focused on the case were control locations have to be selected from a large set of available sites, so that integer programing methods are called for. The effectiveness of three heuristic techniques for obtaining a near-optimal site selection is compared. In addition, efficient reanalysis techniques for the rapid assessment of control effectiveness are presented. Two examples are used to demonstrate the methods: a simple beam structure and a 55m space-truss-parabolic antenna.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-85769 , NAS 1.15:85769 , GWU/LaRC Symp. on Advan. and Trends in Struct. and Dyn.; Oct 22, 1984 - Oct 25, 1984; Washington, DC; United States
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  • 9
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    Integrated Thermal-structural-electromagnetic Design Optimization of Large Space Antenna Reflectors (1986)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The requirements for low mass and high electromagnetic (EM) performance in large, flexible space antenna structures is motivating the development of a systematic procedure for antenna design. In contrast to previous work which concentrated on reducing rms distortions of the reflector surface, thereby indirectly increasing antenna performance, the current work involves a direct approach to increasing electromagnetic performance using mathematical optimization. The thermal, structural, and EM analyses are fully integrated in the context of an optimization procedure, and consequently, the interaction of the various responses is accounted for directly and automatically. Preliminary results are presented for sizing cross-sectional areas of a tetrahedral truss reflector. The results indicate potential for this integrated procedure from the standpoint of mass reduction, performance increase, and efficiency of the design process.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-87713 , NAS 1.15:87713 , AIAA/ASME/ASCE/AHS Structures, Structural Dynamics and Materials Conference; May 19, 1986 - May 21, 1986; San Antonio, TX; United States
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  • 10
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    Multiwall TPS - An emerging concept (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Research on titanium multiwall used for thermal protection is reviewed. Continuing analytical and experimental studies yielding a fundamental understanding of the thermal and structural performance of the basic multiwall concept are presented noting that central to this understanding is a knowledge of the extensional behavior of the dimpled sheets since the thinner flat sheets will buckle and be relatively ineffective in supporting compressive loads. Results from radiant heating, aerothermal, vibration, acoustic and lightning strike tests are described as part of an effort to verify the performance of multiwall tiles under representative operating conditions. Flight tests of a large array of tiles are also planned as part of an orbiter experiments program. The research effort is being extended from flat all-titanium multiwall configurations limited to temperatures below 810 K to curved surfaces and higher temperature versions. Multi-wall concepts are found to offer the durability of metallic systems and to be mass competitive with the insulation system currently used on the Space Shuttle Orbiter.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 81-0586 , Conference on Structures, Structural Dynamics and Materials; Apr 06, 1981 - Apr 08, 1981; Atlanta, GA
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