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  • 1
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    Demonstration of decomposition and optimization in the design of experimental space systems (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Effective design strategies for a class of systems which may be termed Experimental Space Systems (ESS) are needed. These systems, which include large space antenna and observatories, space platforms, earth satellites and deep space explorers, have special characteristics which make them particularly difficult to design. It is argued here that these same characteristics encourage the use of advanced computer-aided optimization and planning techniques. The broad goal of this research is to develop optimization strategies for the design of ESS. These strategics would account for the possibly conflicting requirements of mission life, safety, scientific payoffs, initial system cost, launch limitations and maintenance costs. The strategies must also preserve the coupling between disciplines or between subsystems. Here, the specific purpose is to describe a computer-aided planning and scheduling technique. This technique provides the designer with a way to map the flow of data between multidisciplinary analyses. The technique is important because it enables the designer to decompose the system design problem into a number of smaller subproblems. The planning and scheduling technique is demonstrated by its application to a specific preliminary design problem.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Recent Advances in Multidisciplinary Analysis and Optimization, Part 1; p 297-316
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  • 2
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    Active strut placement using integer programming for the CSI Revolutionary Model (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A method for determining the most effective locations for active struts on large space structures is developed and tested on the NASA CSI Evolutionary Model. Depending on the choice of weighting factors, the method can be used to maximize the maximum modal damping ratio or decay rate, or to maximize a mission-oriented measure of performance. Placement of 8, 16, and 32 active struts out of 1507 candidate truss elements is demonstrated. Preliminary estimates of damping enhancement are reported pending refined structural models and dynamic test results. The method can handle complicated FEM models wih a large number of truss elements and many target modes. It can treat each mode equally or it can emphasize the importance of selected modes. The method can eliminate some combinations of actuator locations based on topological constraints.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA PAPER 92-4787 , In: AIAA(USAF)NASA/OAI Symposium on Multidisciplinary Analysis and Optimization, 4th, Cleveland, OH, Sept. 21-23, 1992, Technical Papers. Pt. 2 (A93-20301 06-66); p. 784-793.
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  • 3
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    ISS Radiation Shielding and Acoustic Simulation Using an Immersive Environment (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: The International Space Station Environment Simulator (ISSES) is a virtual reality application that uses high-performance computing, graphics, and audio rendering to simulate the radiation and acoustic environments of the International Space Station (ISS). This CAVE application allows the user to maneuver to different locations inside or outside of the ISS and interactively compute and display the radiation dose at a point. The directional dose data is displayed as a color-mapped sphere that indicates the relative levels of radiation from all directions about the center of the sphere. The noise environment is rendered in real time over headphones or speakers and includes non-spatial background noise, such as air-handling equipment, and spatial sounds associated with specific equipment racks, such as compressors or fans. Changes can be made to equipment rack locations that produce changes in both the radiation shielding and system noise. The ISSES application allows for interactive investigation and collaborative trade studies between radiation shielding and noise for crew safety and comfort.
    Keywords: Spacecraft Design, Testing and Performance
    Format: application/pdf
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  • 4
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    Accuracy of derivatives of control performance using a reduced structural model (1987)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The sensitivity of control system performance to structural changes is calculated for a multi-span beam with direct-rate feedback vibration control. Reduced models based on the natural modes of the structure are formed and derivatives of the damping ratios of the closed-loop eigenvalues are calculated. The convergence of the derivatives of the damping ratios with increasing number of modes is shown to be slower than the convergence of the damping ratios themselves. In particular, in some cases the convergence of finite-element approximations to the derivatives is much faster than the convergence of the modal approximations. The results indicate that the use of reduced models based on natural vibration modes may be ill-advised for calculating the sensitivity of control system performance to changes in the controlled structure.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA PAPER 87-0905
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  • 5
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    OLTARIS: An Efficient Web-Based Tool for Analyzing Materials Exposed to Space Radiation (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The near-Earth space radiation environment includes energetic galactic cosmic rays (GCR), high intensity proton and electron belts, and the potential for solar particle events (SPE). These sources may penetrate shielding materials and deposit significant energy in sensitive electronic devices on board spacecraft and satellites. Material and design optimization methods may be used to reduce the exposure and extend the operational lifetime of individual components and systems. Since laboratory experiments are expensive and may not cover the range of particles and energies relevant for space applications, such optimization may be done computationally with efficient algorithms that include the various constraints placed on the component, system, or mission. In the present work, the web-based tool OLTARIS (On-Line Tool for the Assessment of Radiation in Space) is presented, and the applicability of the tool for rapidly analyzing exposure levels within either complicated shielding geometries or user-defined material slabs exposed to space radiation is demonstrated. An example approach for material optimization is also presented. Slabs of various advanced multifunctional materials are defined and exposed to several space radiation environments. The materials and thicknesses defining each layer in the slab are then systematically adjusted to arrive at an optimal slab configuration.
    Keywords: Space Radiation
    Type: NF1676L-12527 , SPIE Optics and Photonics 2011; Aug 21, 2011 - Aug 25, 2011; San Diego, CA; United States
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  • 6
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    Integrated controls-structures optimization of a large space structure (1990)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A technique for the simultaneous optimization of structural and control elements of a large space structure is developed and demonstrated for a test problem, the NASA COFS-I Mast Flight System. General-purpose control and structural-analysis codes are applied directly to a large detailed model, with realistic objective and constraint functions. The steps in the process (structural optimization, control optimization, and system coordination) are described and illustrated with diagrams; the numerical implementation (using different computers for different steps) is discussed; and results showing significant design improvements in three COFS-I configurations are presented in graphs. When the weights of both structure and power-generating equipment are taken into account, a 40-bay truss design is found to be better than designs with 42 or 44 bays.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 90-1058 , AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 02, 1990 - Apr 04, 1990; Long Beach, CA; United States
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  • 7
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    On-Line Tool for the Assessment of Radiation in Space - Deep Space Mission Enhancements (2011)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The On-Line Tool for the Assessment of Radiation in Space (OLTARIS, https://oltaris.nasa.gov) is a web-based set of tools and models that allows engineers and scientists to assess the effects of space radiation on spacecraft, habitats, rovers, and spacesuits. The site is intended to be a design tool for those studying the effects of space radiation for current and future missions as well as a research tool for those developing advanced material and shielding concepts. The tools and models are built around the HZETRN radiation transport code and are primarily focused on human- and electronic-related responses. The focus of this paper is to highlight new capabilities that have been added to support deep space (outside Low Earth Orbit) missions. Specifically, the electron, proton, and heavy ion design environments for the Europa mission have been incorporated along with an efficient coupled electron-photon transport capability to enable the analysis of complicated geometries and slabs exposed to these environments. In addition, a neutron albedo lunar surface environment was also added, that will be of value for the analysis of surface habitats. These updates will be discussed in terms of their implementation and on how OLTARIS can be used by instrument vendors, mission designers, and researchers to analyze their specific requirements.12
    Keywords: Space Radiation
    Type: IEEAC Paper 1107 , NF1676L-11003 , 2011 IEEE Aerospace Conference; Mar 05, 2011 - Mar 12, 2011; Big Sky, MT; United States
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  • 8
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    On-line identification of forward/inverse systems for adaptive control applications (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The paper is concerned with the on-line identification of system Markov parameters using observers. Two types of parameters are sought: the forward system parameters, which provide estimates of the outputs for given inputs, and inverse system parameters, which provide estimates of inputs for given outputs. A procedure is proposed which uses the inverse system to generate commands that produce a desired system response. The feasibility of the procedure is demonstrated using test results from an implementation of a truss structure fitted with piezoelectric actuators and collocated strain gauges.
    Keywords: CYBERNETICS
    Type: AIAA PAPER 92-4384 , AIAA Guidance, Navigation and Control Conference; Aug 10, 1992 - Aug 12, 1992; Hilton Head Island, SC; United States
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  • 9
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    Accuracy of eigenvalue derivatives from reduced-order structural models (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 12; 822-829
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  • 10
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    Modal truncation, Ritz vectors, and derivatives of closed-loop damping ratios (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The effect of modal truncation on the damping ratio and their derivatives with respect to an added mass is investigated for a simply supported, multispan beam with a linear quadratic Gaussian control system. It is found that both the damping ratios and derivatives converge slowly, but the derivatives converge more slowly than the damping ratios. However, it is shown that when Ritz vectors corresponding to static displacements due to actuator forces are added to the reduced model, the convergence of both the damping ratios and their derivatives is accelerated. It is also shown that the accuracy of the damping ratio predicted by a reduced-model control design can be improved significantly if the Ritz vectors are included in the design of the control system. Thus, it appears that Ritz vectors added to the reduced model of flexible structures can improve greatly the accuracy of both the design and analysis of the control system.
    Keywords: CYBERNETICS
    Type: Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 14; 785-790
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