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  • Other Sources  (5)
  • 1985-1989  (5)
  • 1986  (2)
  • 1985  (3)
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  • 1985-1989  (5)
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  • 1
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    Space Shuttle Main Engine fuel preburner augmented spark igniter shutdown detonations (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Detonations were experienced in the Space Shuttle Main Engine fuel preburner (FPB) augmented spark igniter (ASI) during engine cutoff. Several of these resulted in over pressures sufficient to damage the FPB ASI oxidizer system. The detonations initiated in the FPB ASI oxidizer line when residual oxidizer (oxygen) in the line mixed with backflowing fuel (hydrogen) and detonated. This paper reviews the damage history to the FPB ASI oxidizer system, an engineering assessment of the problem cause, a verification of the mechanisms, the hazards associated with the detonations, and the solution implemented.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 86-1445
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Impact resistance and interlaminar fracture toughness of through-the-thickness reinforced graphite/epoxy (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Five through-the-thickness stitch configurations are analyzed to determine the effect of impact resistance and interlaminar fracture toughness on T3000/3501-6 graphite/epoxy. The test specimens were stitched with either polyester or Kevlar yarns and with various stitch parameters. Tension and compression mechanical, impact and compression-after-impact, and double cantilever beam tests were conducted. It is observed that the stitched laminates have tension and compression strengths 20-25 percent lower than the strengths of unstitched laminates, the tension strength of stitched laminates is reduced with increasing number of stitches, and the compression strength increases as the number of stitches are increased. The impact data reveal that the Kevlar stitched laminates have less damage than unstitched laminates; the most effective configuration for suppressing impact damage and improving interlaminar fracture toughness consists of Kevlar yarns 1/4 inch apart with eight stitches per inch. The mode 1 critical strain energy release rate for the 1/4 inch Kevlar eight stitch laminate was calculated as 30 times higher than that of the unstitched.
    Keywords: COMPOSITE MATERIALS
    Type: AIAA PAPER 86-1020
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Measurement and analysis of critical crack tip processes during fatigue crack growth (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The mechanics of fatigue crack growth under constant-amplitudes and variable-amplitude loading were examined. Critical loading histories involving relatively simple overload and overload/underload cycles were studied to provide a basic understanding of the underlying physical processes controlling crack growth. The material used for this study was 7091-T7E69, a powder metallurgy aluminum alloy. Local crack-tip parameters were measured at various times before, during, and after the overloads, these include crack-tip opening loads and displacements, and crack-tip strain fields. The latter were useed, in combination with the materials cyclic and monotonic stress-strain properties, to compute crack-tip residual stresses. The experimental results are also compared with analytical predictions obtained using the FAST-2 computer code. The sensitivity of the analytical model to constant-amplitude fatigue crack growth rate properties and to through-thickness constrain are studied.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-172597 , NAS 1.26:172597
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Chemical kinetic performance losses for a hydrogen laser thermal thruster (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Projected requirements for efficient, economical, orbit-raising propulsion systems have generated investigations into several potentially high specific impulse, moderate thrust, advanced systems. One of these systems, laser thermal propulsion, utilizes a high temperature plasma as the enthalpy source. The plasma is sustained by a focused laser beam which maintains the plasma temperature at levels near 20,000 K. Since such temperature levels lead to total dissociation and high ionization, the plasma thruster system potentially has a high specific impulse decrement due to recombination losses. The nozzle flow is expected to be sufficiently nonequilibrium to warrant concern over the achievable specific impluse. This investigation was an attempt at evaluation of those losses. The One-Dimensional Kinetics (ODK) option of the Two-Dimensional Kinetics (TDK) Computer Program was used with a chemical kinetics rate set obtained from available literature to determine the chemical kinetic energy losses for typical plasma thruster conditions. The rates were varied about the nominal accepted values to band the possible losses. Kinetic losses were shown to be highly significant for a laser thermal thruster using hydrogen. A 30 percent reduction in specific impulse is possible simply due to the inability to completely extract the molecular recombination energy.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 85-0907
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Advances in Composites Technology (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A significant level of research is currently focused on the development of tough resins and high strain fibers in an effort to gain improved damage tolerance. Moderate success has been achieved with the development of new resins such as PEEK and additional improvements look promising with new thermoplastic resins. Development of innovative material forms such as 2-D and 3-D woven fabrics and braided structural subelements is also expected to improve damage tolerance and durability of composite hardware. The new thrust in composites is to develop low cost manufacturing and design concepts to lower the cost of composite hardware. Processes being examined include automated material placement, filament winding, pultrusion, and thermoforming. The factory of the future will likely incorporate extensive automation in all aspects of manufacturing composite components.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TM-86353 , NAS 1.15:86353
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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