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  • Other Sources  (14)
  • NASA Technical Reports  (14)
  • STRUCTURAL MECHANICS  (5)
  • COMPUTER PROGRAMMING AND SOFTWARE  (3)
  • INORGANIC AND PHYSICAL CHEMISTRY  (3)
  • METEOROLOGY AND CLIMATOLOGY  (3)
  • 1990-1994  (14)
  • 1955-1959
  • 1993  (14)
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  • Other Sources  (14)
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  • NASA Technical Reports  (14)
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  • 1990-1994  (14)
  • 1955-1959
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  • 1
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    Technology integration box beam failure study (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Composite structures have the potential to be cost-effective, structurally efficient primary aircraft structures. The Advanced Composites Technology (ACT) Program has the goal to develop the technology to exploit this potential for heavily loaded aircraft structures. As part of the ACT Program, Lockheed Aeronautical Systems Company completed the design and fabrication of the Technology Integration Box Beam (TIBB). The TIBB is an advanced composite prototype structure for the center wing section of the C-130 aircraft. Lockheed subjected the TIBB to downbending, upbending, torsion and combined upbending and torsion load conditions to verify the design. The TIBB failed at 83 percent of design ultimate load for the combined upbending and torsion load condition. The objective of this paper is to describe the mechanisms that led to the failure of the TIBB. The results of a comprehensive analytical and experimental study are presented. Analytical results include strain and deflection results from both a global analysis of the TIBB and a local analysis of the failure region. These analytical results are validated by experimental results from the TIBB tests. The analytical and experimental results from the TIBB tests are used to determine a sequence of events that resulted in failure of the TIBB. A potential cause of failure is high stresses in a stiffener runout region. Analytical and experimental results are also presented for a stiffener runout specimen that was used to simulate the TIBB failure mechanisms.
    Keywords: STRUCTURAL MECHANICS
    Type: Third NASA Advanced Composites Technology Conference, Volume 1, Part 2; p 951-965
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  • 2
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    Limited Duration of Candidate Materials Exposure Experiment (LDCE): A Complex Autonomous Payload (CAP) using a Get Away Special (GAS) canister (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: CMSS has designed, fabricated, qualified and flown the LDCE payload as a cost effective space flight hardware to conduct exposure of materials to the space environment. The hardware has been qualified for 10 missions, utilizing a GAS Canister, supplied by Goddard Space Flight Center. Results of the first series of LDCE experiments have shown that the hardware performed as expected.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: NASA. Goddard Space Flight Center, The 1993 Shuttle Small Payloads Symposium; p 115-124
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  • 3
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    Structural control sensors for the CASES GTF (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: CASES (Controls, Astrophysics and Structures Experiment in Space) is a proposed space experiment to collect x-ray images of the galactic center and solar disk with unprecedented resolution. This requires precision pointing and suppression of vibrations in the long flexible structure that comprises the 32-m x-ray telescope optical bench. Two separate electro-optical sensor systems are provided for the ground test facility (GTF). The Boom Motion Tracker (BMT) measures eigenvector data for post-mission use in system identification. The Tip Displacement Sensor (TDS) measures boom tip position and is used as feedback for the closed-loop control system that stabilizes the boom. Both the BMT and the TDS have met acceptance specifications and were delivered to MSFC in February 1992. This paper describes the sensor concept, the sensor configuration as implemented in the GTF, and the results of characterization and performance testing.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center, The Fifth NASA(DOD Controls-Structures Interaction Technology Conference, Part 1; p 263-275
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  • 4
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    Design, analysis, and testing of high frequency passively damped struts (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Objectives of the research are: (1) to develop design requirements for damped struts to stabilize control system in the high frequency cross-over and spill-over range; (2) to design, fabricate and test viscously damped strut and viscoelastically damped strut; (3) to verify accuracy of design and analysis methodology of damped struts; and (4) to design and build test apparatus, and develop data reduction algorithm to measure strut complex stiffness. In order to meet the stringent performance requirements of the SPICE experiment, the active control system is used to suppress the dynamic responses of the low order structural modes. However, the control system also inadvertently drives some of the higher order modes unstable in the cross-over and spill-over frequency range. Passive damping is a reliable and effective way to provide damping to stabilize the control system. It also improves the robustness of the control system. Damping is designed into the SPICE testbed as an integral part of the control-structure technology.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center, The Fifth NASA(DOD Controls-Structures Interaction Technology Conference, Part 1; p 239-249
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  • 5
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    Diffusion-controlled magnesium isotopic fractionation of a single crystal forsterite evaporated from the solid state (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: Though the origin of calcium- and aluminum-rich inclusions (CAI's) in carbonaceous chondrites is till a disputed issue, evaporation is no doubt one of the most important processes for the formation of CAI's in the early solar nebula. The mechanism for production of large isotopic mass fractionation effects in magnesium, silicon, oxygen, and chromium in CAI's can be better understood by examining isotopic fractionation during the evaporation of minerals. New evaporation experiments were performed on single-crystal forsterite. The magnesium isotopic distribution near the evaporating surfaces of the residues using a modified AEI IM-20 ion microprobe to obtain rastered beam depth profiles was measured. A theoretical model was used to explain the profiles and allowed determination of the diffusion coefficient of Mg(++) in forsterite at higher temperatures than previous measurements. The gas/solid isotopic fractionation factor for magnesium for evaporation from solid forsterite was also determined and found to be nearly the same as that for evaporation of liquid Mg2SiO4.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 3: N-Z; p 1479-1480
    Format: text
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  • 6
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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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  • 7
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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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  • 8
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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
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  • 9
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    Spectral emissivity of cirrus clouds (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The inference of cirrus cloud properties has many important applications including global climate studies, radiation budget determination, remote sensing techniques and oceanic studies from satellites. Data taken at the Parsons Kansas site during the FIRE II project are used for this study. On November 26 there were initially clear sky conditions gradually giving way to a progressively thickening cirrus shield over a period of a few hours. Interferometer radiosonde and lidar data were taken throughout this event. Two techniques are used to infer the downward spectral emittance of the observed cirrus layer. One uses only measurements and the other involves measurements and FASCODE III calculations. FASCODE III is a line-by line radiance/transmittance model developed at the Air Force Geophysics Laboratory.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: NASA. Langley Research Center, The FIRE Cirrus Science Results 1993; p 125-128
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  • 10
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    Spectral variation of scattering and absorption by cirrus (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The impact of cirrus clouds on the radiative budget of the earth depends on the microphysics and scattering properties of the clouds. Cirrus clouds have been especially difficult to observe because of their high altitude and complex tenuous structure. Observations by Abakumova et. al. (1991) show that the near infrared wavelengths are more sensitive to the cirrus cloud properties than the shorter ultraviolet wavelengths. Anikin (1991) was able to show that collimated spectral measurements can be used to determine an effective particle size of the cirrus clouds. Anikin (1991) also showed that the effect of scattering through cloud causes the apparent optical depth of a 10 degrees field of view pyrheliometer to be roughly half the actual optical depth. Stackhouse and Stephens (1991) have shown that the existence of small ice crystals do dramatically affect the radiative properties of the cirrus, though observations taken during the 1986 FIRE were not totally explained by their presence.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: NASA. Langley Research Center, The FIRE Cirrus Science Results 1993; p 121-124
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