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  • 1
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    Torsional suspension system for testing space structures (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A low frequency torsional suspension system for testing a space structure uses a plurality of suspension stations attached to the space structure along the length thereof in order to suspend the space structure from an overhead support. Each suspension station includes a disk pivotally mounted to the overhead support, and two cables which have upper ends connected to the disk and lower ends connected to the space structure. The two cables define a parallelogram with the center of gravity of the space structure being vertically beneath the pivot axis of the disk. The vertical distance between the points of attachment of the cables to the disk and the pivot axis of the disk is adjusted to lower the frequency of the suspension system to a level which does not interfere with frequency levels of the space structure, thereby enabling accurate measurement.
    Keywords: GROUND SUPPORT SYSTEMS AND FACILITIES (SPACE)
    Format: application/pdf
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  • 2
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    An analysis of the effect of a curved ramp on the take-off performance of catapult-launched airplanes (1952)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Type: NACA-RM-L52I05
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  • 3
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    A Preliminary Flight Investigation of the Effects of Vortex Generators on Separation Due to Shock (1950)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Type: NACA-RM-L50J02
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  • 4
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    An analytical study of the effect of airplane wake on the lateral dispersion of aerial sprays (1953)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Type: NACA-TN-3032
    Format: application/pdf
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  • 5
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    An analytical study of the effect of airplane wake on the lateral dispersion of aerial sprays (1954)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Calculations are made to determine the trajectories of liquid droplets introduced into the air disturbances generated by an airplane engaged in aerial spraying. The effects of such factors as the positions at which droplets are ejected into the disturbances, airplane lift coefficient, and altitude are investigated. The distribution of deposit on the ground is computed for several droplet-size spectra, variations in the rate at which mass is ejected along the span, and lateral flight-path spacings. Consideration is then given to the problem of adjusting these factors with the aim of improving the uniformity and increasing the effective width of the deposit. The results indicate that the lateral dispersion of droplets is increased when the spanwise position at which particles are ejected is moved toward the wing tip. Greater dispersion also results when the airplane lift coefficient or altitude is increased.
    Type: NACA-TR-1196
    Format: application/pdf
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  • 6
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    Suspension systems for ground testing large space structures (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A research program is documented for the development of improved suspension techniques for ground vibration testing of large, flexible space structures. The suspension system must support the weight of the structure and simultaneously allow simulation of the unconstrained rigid-body movement as in the space environment. Exploratory analytical and experimental studies were conducted for suspension systems designed to provide minimum vertical, horizontal, and rotational degrees of freedom. The effects of active feedback control added to the passive system were also investigated. An experimental suspension apparatus was designed, fabricated, and tested. This test apparatus included a zero spring rate mechanism (ZSRM) designed to support a range of weights from 50 to 300 lbs and provide vertical suspension mode frequencies less than 0.1 Hz. The lateral suspension consisted of a pendulum suspended from a moving cart (linear bearing) which served to increase the effective length of the pendulum. The torsion suspension concept involved dual pendulum cables attached from above to a pivoting support (bicycle wheel). A simple test structure having variable weight and stiffness characteristics was used to simulate the vibration characteristics of a large space structure. The suspension hardware for the individual degrees of freedom was analyzed and tested separately and then combined to achieve a 3 degree of freedom suspension system. Results from the exploratory studies should provide useful guidelines for the development of future suspension systems for ground vibration testing of large space structures.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-CR-4325 , NAS 1.26:4325 , D-377
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  • 7
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    An Analytical Treatment of Aircraft Propeller Precession Instability (1961)
    In:  CASI
    Details
    Publication Date: 2019-08-16
    Description: An analytical investigation is made of a precession-type instability which can occur in a flexibly supported aircraft-engine-propeller combination. By means of an idealized mathematical model which is comprised of a rigid power-plant system flexibly mounted in pitch and yaw to a fixed backup structure, the conditions required for neutral stability are determined. The paper also examines the sensitivity of the stability boundaries to changes in such parameters as stiffness, damping, and asymmetries in the engine mount, propeller speed, airspeed, Mach number, propeller thrust, and location of pitch and yaw axes. Stability is found to depend strongly on the damping and stiffness in the system. With the use of nondimensional charts, theoretical stability boundaries are compared with experimental results obtained in wind-tunnel tests of an aeroelastic airplane model. In general, the theoretical results, which do not account for wing response, show the same trends as observed experimentally; however, for a given set of conditions calculated airspeeds for neutral stability are consistently lower than the measured values. Evidently, this result is due to the fact that wing response tends to add damping to the system.
    Keywords: Aircraft Design, Testing and Performance
    Type: NASA-TN-D-659
    Format: application/pdf
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  • 8
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    Low-Frequency Suspension System For Large Space Structures (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Simple system enables vibration testing of space structures on ground. Suspension system includes number of suspension stations attached by cables to space structure (such as truss beam) along its length. Suspension stations fixed to ceiling or other rigid support. Disk and cable adjustments lower frequency of oscillatory motion of suspension system to enable accurate measurements of frequencies of vibration of space structure. Designed to alleviate coupling between suspension system and torsional vibrational modes of structure.
    Keywords: MECHANICS
    Type: LAR-14149 , NASA Tech Briefs (ISSN 0145-319X); 15; 6; P. 62
    Format: text
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  • 9
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    Analog Techniques for Measuring the Frequency Response of Linear Physical Systems Excited by Frequency-Sweep Inputs (1960)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: Data-reduction methods using general-purpose analog computer equipment and compatible testing techniques for determining the frequency response of linear physical systems are examined. The techniques considered may be classed as steady state or transient depending on the method of excitation. The relative merits of periodic, slow sweep, and transient (rapid sweep) forcing functions are discussed and applications are given that relate to dynamic-response tests of aeroelastic systems. Two frequency-sweep-input methods are considered in detail. one case the sweep rate is sufficiently slow that the response is approximately the same as that for steady-state conditions. With this input the frequency response can be evaluated and displayed in real time while the test is in progress. Errors due to treating sweep data as steady state can be eliminated, when desired, by reanalyzing tape-recorded time histories of the input and output as transient rather than as periodic data. In the second method the frequency-response function is deter- mined from the system's transient response to a very rapid sweep input. The purpose of frequency sweep in this case is to provide sufficient harmonic content in the input to overcome noise while keeping the test time as short as possible. tests and limited flight-test data presented herein, it appears that a transient-type rapid-sweep forcing function offers a considerable saving in test time while preserving the accuracy possible with steady-state sinusoidal inputs.
    Keywords: Computer Programming and Software
    Type: NASA-TN-D-508 , L-985
    Format: text
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