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  • Other Sources  (6)
  • 1995-1999  (2)
  • 1990-1994  (4)
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  • 1
    Publication Date: 2019-06-28
    Description: A new second-order theory was developed for predicting the service lives of aerospace structural components. The predictions based on this new theory were compared with those based on the Ko first-order theory and the classical theory of service life predictions. The new theory gives very accurate service life predictions. An equivalent constant-amplitude stress cycle method was proposed for representing the random load spectrum for crack growth calculations. This method predicts the most conservative service life. The proposed use of minimum detectable crack size, instead of proof load established crack size as an initial crack size for crack growth calculations, could give a more realistic service life.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-4354 , H-1760 , NAS 1.15:4354
    Format: application/pdf
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  • 2
    Publication Date: 2019-07-13
    Description: A boundary-layer transition is proposed for a future flight mission of the air-launched Pegasus space booster. The flight experiment requires attaching a glove assembly to the wing of the first-stage booster. The glove design consists of a spring and hook attachment system which allows for thermal growth of a steel 4130 skin. The results from one- and two-dimensional thermal analyses of the initial design are presented. Results obtained from the thermal analysis using turbulent flow conditions showed a maximum temperature of approximately 305 C and a chordwise temperature gradient of less than 8.9 C/cm for the critical areas in the upper glove skin. The temperatures obtained from these thermal analyses are well within the required temperature limits of the glove.
    Keywords: AERONAUTICS (GENERAL)
    Type: NASA-TM-104272 , H-1954 , NAS 1.15:104272 , Society for Experimenal Mechanics, Structural Testing Technology at High Temperature 2 Conference; Nov 08, 1993 - Nov 10, 1993; Ojai, CA; United States
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  • 3
    Publication Date: 2019-07-12
    Description: The process of gravitational fragmentation of molecular clouds is investigated through a comparison of numerical and observational results. The expected millimeter wave molecular line emission from a model fragmenting cloud generated by a numerical hydrodynamic simulation is calculated and compared with observations of HCO(+) from the star-forming region W49A. This investigation suggests that the rotating ring of H II regions, the necklace in W49A, may have formed in the gravitational fragmentation of a flattened rotating molecular cloud.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 383; 639-644
    Format: text
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  • 4
    Publication Date: 2019-07-13
    Description: The design of the next generation of space access vehicles has led to a unique flight test that blends the space and flight research worlds. The new space vehicle designs, such as the X-33 vehicle and Reusable Launch Vehicle (RLV), are powered by linear aerospike rocket engines. Conceived of in the 1960's, these aerospike engines have yet to be flown, and many questions remain regarding aerospike engine performance and efficiency in flight. To provide some of these data before flying on the X-33 vehicle and the RLV, a spacecraft rocket engine has been flight-tested atop the NASA SR-71 aircraft as the Linear Aerospike SR-71 Experiment (LASRE). A 20 percent-scale, semispan model of the X-33 vehicle, the aerospike engine, and all the required fuel and oxidizer tanks and propellant feed systems have been mounted atop the SR-71 airplane for this experiment. A major technical objective of the LASRE flight test is to obtain installed-engine performance flight data for comparison to wind-tunnel results and for the development of computational fluid dynamics-based design methodologies. The ultimate goal of firing the aerospike rocket engine in flight is still forthcoming. An extensive design and development phase of the experiment hardware has been completed, including approximately 40 ground tests. Five flights of the LASRE and firing the rocket engine using inert liquid nitrogen and helium in place of liquid oxygen and hydrogen have been successfully completed.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-1998-206567 , H-2280 , NAS 1.15:206567 , Sep 15, 1998 - Sep 17, 1998; Reno, NV; United States
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  • 5
    Publication Date: 2019-07-12
    Description: The application of the Smoothed Particle Hydrodynamics method to the fragmentation of rotating cloud and disk systems is described, allowing for molecular cooling due to H2 and CO. A novel approach to solving Poisson's equation for disklike structures which exploits the multigrid algorithm is also described. Numerical studies are presented which investigate the evolution of both rotating clouds and Maclaurin disks, in each case with both an isothermal equation of state and with molecular cooling. The results establish the influence of molecular cooling on the fragmentation of molecular clouds. The isothermal sequences, if they fragment at all, do so into far fewer lumps than the cooling sequences. This is not due to a cooling instability as such, but rather to the reduced thermal support. One of the sequences shows a remarkable similarity to the W49A star-forming region.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 375; 177-189
    Format: text
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  • 6
    Publication Date: 2019-08-15
    Description: Preparations for a boundary-layer transition experiment to be conducted on a future flight mission of the air-launched Pegasus(TM) rocket are underway. The experiment requires a flight-test article called a glove to be attached to the wing of the Mach-8 first-stage booster. A three-dimensional, nonlinear finite-element analysis has been performed and significant small-scale laboratory testing has been accomplished to ensure the glove design integrity and quality of the experiment. Reliance on both the analysis and experiment activities has been instrumental in the success of the flight-article design. Results obtained from the structural analysis and laboratory testing show that all glove components are well within the allowable thermal stress and deformation requirements to satisfy the experiment objectives.
    Keywords: Structural Mechanics
    Type: NASA-TM-4733 , H-2088 , NAS 1.15:4733 , First International Conference on Computational Methods and Testing for Engineering Integrity; Mar 19, 1996 - Mar 21, 1996; Kuala Lumpur; Malaysia
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