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  • Other Sources  (30)
  • STRUCTURAL MECHANICS  (17)
  • COMPUTER PROGRAMMING AND SOFTWARE  (13)
  • 1990-1994  (30)
  • 1955-1959
  • 11
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    Conceptual design and analysis of a dynamic scale model of the Space Station Freedom (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This report documents the conceptual design study performed to evaluate design options for a subscale dynamic test model which could be used to investigate the expected on-orbit structural dynamic characteristics of the Space Station Freedom early build configurations. The baseline option was a 'near-replica' model of the SSF SC-7 pre-integrated truss configuration. The approach used to develop conceptual design options involved three sets of studies: evaluation of the full-scale design and analysis databases, conducting scale factor trade studies, and performing design sensitivity studies. The scale factor trade study was conducted to develop a fundamental understanding of the key scaling parameters that drive design, performance and cost of a SSF dynamic scale model. Four scale model options were estimated: 1/4, 1/5, 1/7, and 1/10 scale. Prototype hardware was fabricated to assess producibility issues. Based on the results of the study, a 1/4-scale size is recommended based on the increased model fidelity associated with a larger scale factor. A design sensitivity study was performed to identify critical hardware component properties that drive dynamic performance. A total of 118 component properties were identified which require high-fidelity replication. Lower fidelity dynamic similarity scaling can be used for non-critical components.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-4598 , NAS 1.26:4598 , LMSC/F440397
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 12
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    Translating an AI application from Lisp to Ada: A case study (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A set of benchmarks was developed to test the performance of a newly designed computer executing both Lisp and Ada. Among these was AutoClassII -- a large Artificial Intelligence (AI) application written in Common Lisp. The extraction of a representative subset of this complex application was aided by a Lisp Code Analyzer (LCA). The LCA enabled rapid analysis of the code, putting it in a concise and functionally readable form. An equivalent benchmark was created in Ada through manual translation of the Lisp version. A comparison of the execution results of both programs across a variety of compiler-machine combinations indicate that line-by-line translation coupled with analysis of the initial code can produce relatively efficient and reusable target code.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-TM-103845 , A-91094 , NAS 1.15:103845
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    NASA TECHNICAL REPORTS
  • 13
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    Spacecraft Orbit Design and Analysis (SODA). Version 2.0: User's guide (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The Spacecraft Orbit Design and Analysis (SODA) computer program, Version 2.0, is discussed. SODA is a spaceflight mission planning system that consists of six program modules integrated around a common database and user interface. SODA runs on a VAX/VMS computer with an Evans and Sutherland PS300 graphics workstation. In the current version, three program modules produce an interactive three dimensional animation of one or more satellites in planetary orbit. Satellite visibility and sensor coverage capabilities are also provided. Circular and rectangular, off nadir, fixed and scanning sensors are supported. One module produces an interactive three dimensional animation of the solar system. Another module calculates cumulative satellite sensor coverage and revisit time for one or more satellites. Currently, Earth, Moon, and Mars systems are supported for all modules except the solar system module.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-CR-187494 , NAS 1.26:187494 , TAO-60057
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    NASA TECHNICAL REPORTS
  • 14
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    A parametric shell analysis of the shuttle 51-L SRB AFT field joint (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Following the Shuttle 51-L accident, an investigation was conducted to determine the cause of the failure. Investigators at the Langley Research Center focused attention on the structural behavior of the field joints with O-ring seals in the steel solid rocket booster (SRB) cases. The shell-of-revolution computer program BOSOR4 was used to model the aft field joint of the solid rocket booster case. The shell model consisted of the SRB wall and joint geometry present during the Shuttle 51-L flight. A parametric study of the joint was performed on the geometry, including joint clearances, contact between the joint components, and on the loads, induced and applied. In addition combinations of geometry and loads were evaluated. The analytical results from the parametric study showed that contact between the joint components was a primary contributor to allowing hot gases to blow by the O-rings. Based upon understanding the original joint behavior, various proposed joint modifications are shown and analyzed in order to provide additional insight and information. Finally, experimental results from a hydro-static pressurization of a test rocket booster case to study joint motion are presented and verified analytically.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-102748 , NAS 1.15:102748
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  • 15
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    User's manual for MacPASCO (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A user's manual is presented for MacPASCO, which is an interactive, graphic, preprocessor for panel design. MacPASCO creates input for PASCO, an existing computer code for structural analysis and sizing of longitudinally stiffened composite panels. MacPASCO provides a graphical user interface which simplifies the specification of panel geometry and reduces user input errors. The user draws the initial structural geometry and reduces user input errors. The user draws the initial structural geometry on the computer screen, then uses a combination of graphic and text inputs to: refine the structural geometry; specify information required for analysis such as panel load and boundary conditions; and define design variables and constraints for minimum mass optimization. Only the use of MacPASCO is described, since the use of PASCO has been documented elsewhere.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-TM-104122 , NAS 1.15:104122
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  • 16
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    Detailed analysis and test correlation of a stiffened composite wing panel (1991)
    In:  Other Sources
    Details
    Publication Date: 2018-12-01
    Description: New finite element analysis methods are examined by application to a complicated composite wing panel from the V-22 rotorcraft. A detailed FEM model with a relatively coarse mesh of 9-node elements was generated, and linear and nonlinear stress analyses, first-ply failure analyses, and buckling analyses were conducted. At low values of applied load, i.e., up to the design ultimate load of the panel, the linear stress analysis accurately predicted the strains and structural response characteristics of the panel.
    Keywords: STRUCTURAL MECHANICS
    Format: text
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  • 17
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    Global synchronization algorithms for the Intel iPSC/860 (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: In a distributed memory multicomputer that has no global clock, global processor synchronization can only be achieved through software. Global synchronization algorithms are used in tridiagonal systems solvers, CFD codes, sequence comparison algorithms, and sorting algorithms. They are also useful for event simulation, debugging, and for solving mutual exclusion problems. For the Intel iPSC/860 in particular, global synchronization can be used to ensure the most effective use of the communication network for operations such as the shift, where each processor in a one-dimensional array or ring concurrently sends a message to its right (or left) neighbor. Three global synchronization algorithms are considered for the iPSC/860: the gysnc() primitive provided by Intel, the PICL primitive sync0(), and a new recursive doubling synchronization (RDS) algorithm. The performance of these algorithms is compared to the performance predicted by communication models of both the long and forced message protocols. Measurements of the cost of shift operations preceded by global synchronization show that the RDS algorithm always synchronizes the nodes more precisely and costs only slightly more than the other two algorithms.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-CR-193618 , NAS 1.26:193618 , RNR-92-027
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 18
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    Perceptual factors that influence use of computer enhanced visual displays (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This document is the final report for the NASA/Langley contract entitled 'Perceptual Factors that Influence Use of Computer Enhanced Visual Displays.' The document consists of two parts. The first part contains a discussion of the problem to which the grant was addressed, a brief discussion of work performed under the grant, and several issues suggested for follow-on work. The second part, presented as Appendix I, contains the annual report produced by Dr. Ann Fulop, the Postdoctoral Research Associate who worked on-site in this project. The main focus of this project was to investigate perceptual factors that might affect a pilot's ability to use computer generated information that is projected into the same visual space that contains information about real world objects. For example, computer generated visual information can identify the type of an attacking aircraft, or its likely trajectory. Such computer generated information must not be so bright that it adversely affects a pilot's ability to perceive other potential threats in the same volume of space. Or, perceptual attributes of computer generated and real display components should not contradict each other in ways that lead to problems of accommodation and, thus, distance judgments. The purpose of the research carried out under this contract was to begin to explore the perceptual factors that contribute to effective use of these displays.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-CR-192961 , NAS 1.26:192961
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  • 19
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    LARCRIM user's guide, version 1.0 (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: LARCRIM is a relational database management system (RDBMS) which performs the conventional duties of an RDBMS with the added feature that it can store attributes which consist of arrays or matrices. This makes it particularly valuable for scientific data management. It is accessible as a stand-alone system and through an application program interface. The stand-alone system may be executed in two modes: menu or command. The menu mode prompts the user for the input required to create, update, and/or query the database. The command mode requires the direct input of LARCRIM commands. Although LARCRIM is an update of an old database family, its performance on modern computers is quite satisfactory. LARCRIM is written in FORTRAN 77 and runs under the UNIX operating system. Versions have been released for the following computers: SUN (3 & 4), Convex, IRIS, Hewlett-Packard, CRAY 2 & Y-MP.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-CR-191416 , NAS 1.26:191416 , TAO-60306
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  • 20
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    A homotopy algorithm for digital optimal projection control GASD-HADOC (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The linear-quadratic-gaussian (LQG) compensator was developed to facilitate the design of control laws for multi-input, multi-output (MIMO) systems. The compensator is computed by solving two algebraic equations for which standard closed-loop solutions exist. Unfortunately, the minimal dimension of an LQG compensator is almost always equal to the dimension of the plant and can thus often violate practical implementation constraints on controller order. This deficiency is especially highlighted when considering control-design for high-order systems such as flexible space structures. This deficiency motivated the development of techniques that enable the design of optimal controllers whose dimension is less than that of the design plant. A homotopy approach based on the optimal projection equations that characterize the necessary conditions for optimal reduced-order control. Homotopy algorithms have global convergence properties and hence do not require that the initializing reduced-order controller be close to the optimal reduced-order controller to guarantee convergence. However, the homotopy algorithm previously developed for solving the optimal projection equations has sublinear convergence properties and the convergence slows at higher authority levels and may fail. A new homotopy algorithm for synthesizing optimal reduced-order controllers for discrete-time systems is described. Unlike the previous homotopy approach, the new algorithm is a gradient-based, parameter optimization formulation and was implemented in MATLAB. The results reported may offer the foundation for a reliable approach to optimal, reduced-order controller design.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-CR-193881 , NAS 1.26:193881
    Format: application/pdf
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