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  • LUNAR AND PLANETARY EXPLORATION  (6)
  • COMPOSITE MATERIALS  (3)
  • 2005-2009
  • 1990-1994  (9)
  • 1992  (9)
  • 1
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    Technology integration box beam failure study (1992)
    In:  Other Sources
    Details
    Publication Date: 2013-08-29
    Description: Composite structures have the potential to be cost effective, structurally efficient primary aircraft structures. As part of the Advanced Composite Technology (ACT) program to exploit this potential for heavily loaded aircraft structures, the design and fabrication of the technology integration box beam (TIBB) was completed. The TIBB is an advanced composite prototype structure for the center wing section of the Lockheed C-130 aircraft. The TIBB was tested for 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. Current analytical and experimental results are described for a study of the mechanisms that led to the failure of the TIBB. Experimental results include load, strain, and deflection data. An analytical study was conducted of the TIBB structural response. Analytical results include strain and deflection results from a global analysis of the TIBB.
    Keywords: COMPOSITE MATERIALS
    Type: Second NASA Advanced Composites Technology Conference; p 99-111
    Format: text
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  • 2
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    Overview of the ACT program (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: NASA's Advanced Composites Program (ACT) was initiated in 1988. A National Research Announcement was issued to solicit innovative ideas that could significantly contribute to development and demonstration of an integrated technology data base and confidence level that permits cost-effective use of composite primary structures in transport aircraft. Fifteen contracts were awarded by the Spring of 1989 and the participants include commercial and military airframe manufacturers, materials developers and suppliers, universities, and government laboratories. The program approach is to develop materials, structural mechanics methodology, design concepts, and fabrication procedures that offer the potential to make composite structures cost-effective compared to aluminum structure. Goals for the ACT program included 30-50 percent weight reduction, 20-25 percent acquisition cost reduction, and provided the scientific basis for predicting materials and structures performance. This paper provides an overview of the ACT program status, plans, and selected technical accomplishments. Sixteen additional papers, which provide more detailed information on the research and development accomplishments, are contained in this publication.
    Keywords: COMPOSITE MATERIALS
    Type: FAA, Ninth DOD(NASA)FAA Conference on Fibrous Composites in Structural Design, Volume 2; p 577-59
    Format: application/pdf
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  • 3
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    Liquid water habitats on early Mars (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Although the Viking results may indicate that Mars has no life today, the possibility exists that Mars may hold the best record of the events that led to the origin of life. There is direct geomorphological evidence that in the past Mars had large amounts of liquid water on its surface. Atmospheric models would suggest that this early period of hydrological activity was due to the presence of a thick atmosphere and the resulting warmer temperatures. From a biological perspective the existence of liquid water by itself motivates the question of the origin of life on Mars. From studies of the Earth's earliest biosphere, we know that by 3.5 Gyr ago life had originated on Earth and reached a fair degree of biological sophistication. Surface activity and erosion on Earth make it difficult to trace the history of life before the 3.5 Gyr timeframe. If Mars did maintain a clement environment for longer than it took for life to originate on Earth, then the question of the origin of life on Mars follows naturally. Based upon simple models of the evolution of the Martian climate, we divide the history of liquid water habitats on the Martian surface into four epochs based upon the atmospheric temperature and pressure.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Papers Presented to the Workshop on the Evolution of the Martian Atmosphere; p 21
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  • 4
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    Issues for further study (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The topics covered include the following: a lunar outpost map, lunar resource utilization, asteroid resource utilization, space energy utilization, and space 'real estate' utilization.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Johnson Space Center, Space Resources. Volume 1: Scenarios; p 41-58
    Format: application/pdf
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  • 5
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    Evolution of the Martian atmosphere: The role of the polar caps (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: Lines of evidence indicate that early in Mars' history, it had a much thicker CO2 atmosphere than it does today. A model was constructed for the evolution of the Martian atmosphere that self consistently calculates the rates at which CO2 is stored in Mars' polar reservoirs. Given some initial abundance, which is assumed to be entirely in the atmosphere, the model calculates the annually averaged temperature of the equatorial region and the polar region, and the planetwide mean. Thus far, results obtained for the case where CO2 condensation in the atmosphere is not a limiting factor. Results fall into two categories: initial inventories above 1 bar and below 1 bar. For inventories above 1 bar, CO2 is partitioned between the atmosphere and regolith with the latter taking up almost 800 mbar of CO2. The rest remains in the atmosphere and is weathered out at a rate proportional to atmospheric pressure. For values less than 1 bar, the evolution scenario is different, polar caps form immediately since there is not enough greenhouse warming to prevent CO2 from going into the regolith and thereby reducing the atmospheric pressure to levels where caps can form. The results do not favor either scenario.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Workshop on the Polar Regions of Mars: Geology, Glaciology, and Climate History, Part 1; p 10-11
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  • 6
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    Mesosiderite clasts with the most extreme positive europium anomalies among solar system rocks (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Pigeonite-plagioclase gabbros that occur as clasts in mesosiderites (brecciated stony-iron meteorites) show extreme fractionations of the rare-earth elements (REEs) with larger positive europium anomalies than any previously known for igneous rocks from the earth, moon, or meteorite parent bodies and greater depletions of light REEs relative to heavy REEs than known for comparable cumulate gabbros. The REE pattern for merrillite in one of these clasts is depleted in light REEs and has a large positive europium anomaly as a result of metamorphic equilibration with the silicates. The extreme REE ratios exhibited by the mesosiderite clasts demonstrate that multistage igneous processes must have occurred on some asteroids in the early solar system. Melting of the crust by large-scale impacts or electrical induction from an early T-Tauri-phase sun may be responsible for these processes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 257; 5073
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  • 7
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    The influence of fiber waviness on the compressive behavior of unidirectional continuous fiber composites (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The influence of fiber waviness and matrix nonlinearity on the compressive behavior of continuous fiber composites is studied. A micromechanics model based on the kinematics of the fibers has been developed to predict the behavior of unidirectional composites with initially wavy fibers under compressive loads. The initial waviness has been idealized as sinusoidal. Nonlinear shear behavior of the matrix has been included. Because the shear strain in the matrix is a function of position, the deformed shape of the fibers differs from the initial shape. Therefore, the deformed fiber shape is represented by a sine series. Fiber waviness and matrix shear properties have been determined experimentally for T650-42/Radel C under several conditions. These experimental data have been used as input into the analytical model. Predicted compressive response is in reasonable agreement with experimental data.
    Keywords: COMPOSITE MATERIALS
    Type: Conference on Composite Materials: Testing and Design; Apr 24, 1990 - Apr 25, 1990; San Francisco, CA; United States
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  • 8
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    Collision rates and impact velocities in the Main Asteroid Belt (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Wetherill's (1967) algorithm is presently used to compute the mutual collision probabilities and impact velocities of a set of 682 asteroids with large-than-50-km radius representative of a bias-free sample of asteroid orbits. While collision probabilities are nearly independent of eccentricities, a significant decrease is associated with larger inclinations. Collisional velocities grow steeply with orbital eccentricity and inclination, but with curiously small variation across the asteroid belt. Family asteroids are noted to undergo collisions with other family members 2-3 times more often than with nonmembers.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 97; 1 Ma
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  • 9
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    Asteroid collisional evolution - An integrated model for the evolution of asteroid rotation rates (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: A comprehensive model for the changes in asteroid spin rates due to large collisions was developed by combining the theoretical results of Cellino et al. (1990) with previously published work on spin rate changes for cratering impacts (Harris, 1979; Dobrovolskis and Burns, 1984). The spin change algorithm, when incorporated into an existing simulation of collisional effects on asteroid sizes, produced an integrated model for studying the simultaneous evolution of asteroid sizes and spin rates over the solar system history. As a result of an analysis of 32 collisional scenarios with regard to the change in the spin rate as a function of asteroid size, it is concluded that the spin rates of all asteroids, except possibly the largest ones, have been significantly altered by collisions over the solar system history and that, in general, shattering impacts are much more important than cratering events in changing the spin of asteroids.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 253; 2 Ja; 604-614
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