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  • 1
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    Dynamics and control of a Shuttle-attached antenna experiment (1985)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 8; 344-353
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 2
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    Control of large antennas based on electromagnetic performance criteria (1985)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The electromagnetic (EM) performance of large flexible antennas is traditionally achieved by imposing stringent geometric restrictions on the structural distortions from a nominal optimum configuration. An approach to alleviate the stringency of the geometrical criteria of satisfactory performance is presented. The approach consists of generating a linear optimal control problem with quadratic cost functional where the cost functional is obtained from the EM characteristics of the antenna and the dynamic system constraint is given by the structural model of the antenna. It is established that the EM based optimal controller is considerably more efficient than the traditional geometrical based controllers. The same EM performance can be achieved with a much reduced control effort.
    Schlagwort(e): SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: Proc. of the Workshop on Identification and Control of Flexible Space Struct., Vol. 1; p 199-227
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 3
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    Space station dynamic modeling, disturbance accommodation, and adaptive control (1985)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Dynamic models for two space station configurations were derived. Space shuttle docking disturbances and their effects on the station and solar panels are quantified. It is shown that hard shuttle docking can cause solar panel buckling. Soft docking and berthing can substantially reduce structural loads at the expense of large shuttle and station attitude excursions. It is found predocking shuttle momentum reduction is necessary to achieve safe and routine operations. A direct model reference adaptive control is synthesized and evaluated for the station model parameter errors and plant dynamics truncations. The rigid body and the flexible modes are treated. It is shown that convergence of the adaptive algorithm can be achieved in 100 seconds with reasonable performance even during shuttle hard docking operations in which station mass and inertia are instantaneously changed by more than 100%.
    Schlagwort(e): SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: Proc. of the Workshop on Identification and Control of Flexible Space Struct., Vol. 1; p 103-139
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 4
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    Space Station dynamic modeling, control and simulation (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Dynamic disturbances of many orders of magnitude greater than those of conventional spacecraft will be routine for the Space Station. Accurate knowledge of inflight structural dynamics and disturbances will be lacking. System identification will reduce uncertainties. To deal with the remaining model errors and time-varying elements, adaptive control may be required. Dynamic models for two Space Station configurations are derived. A direct model reference adaptive control algorithm is synthesized and evaluated with respect to the station model parameter errors and plant dynamics truncations. Both the rigid body and the flexible modes are treated. Simulation results show that convergence of the adaptive algorithm can be achieved in 100 to about 300 seconds with reasonable performance even during Shuttle hard docking operations in which station mass and inertia are instantaneously changed by more than 100 percent.
    Schlagwort(e): SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 5
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    The RF spectra of first and subsequent lightning return strokes in the 1- to 200-km range (1980)
    In:  Other Sources
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    Publikationsdatum: 2019-06-28
    Beschreibung: An experimental characterization of the frequency spectra of first and subsequent stroke electric fields are presented over a distance range from about 1 km, where the fields are primarily electrostatic, to 200 km, where they are primarily radiation. Spectra are presented to about 700 kHz for lightning within 12 km and to about 300 kHz for lightning at 50 and 200 km. It is shown that the return stroke ground wave spectrum beyond 50 km has a peak near 4 kHz but that within 10 km the spectrum shows a steady increase with decreasing frequency to 1 kHz. Frequency spectra at all ranges fall off roughly as 1/f for frequencies between 5 and 100 kHz, while the falloff above 100 kHz is faster as the distance to the stroke increases. From this high-frequency attenuation an RF conductivity for central Florida of between 0.002 and 0.005/ohm/m was determined.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Radio Science; 15; Nov
    Format: text
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  • 6
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    Characterization of lightning return stroke electric and magnetic fields from simultaneous two-station measurements (1979)
    In:  Other Sources
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    Publikationsdatum: 2019-06-27
    Beschreibung: The paper presents a characterization of Florida lightning return stroke electric and magnetic fields derived from simultaneous measurements of the fields at two separate stations, one station being within 15 km of the lightning, the other at either about 50 or 200 km from the lightning. Also presented are: (1) examples of correlated wave forms, (2) typical first and subsequent stroke wave forms over the distance range 1.0-200 km, and (3) the following statistical data from which the typical wave forms were derived: for electric field, rise time, initial peak value, ramp starting time, ramp slope, value at 170 microsec, ratio of value at 170 microsec to initial peak, zero-crossing time for 50 and 200 km wave forms; for magnetic fields, time of hump following initial peak, ratio of hump value to initial peak value, zero-crossing time for 50 and 200 km wave forms. Return stroke electric and magnetic field characteristics appear to be independent of location in Florida.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Geophysical Research; 84; Oct. 20
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 7
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    Calculations of lightning return stroke electric and magnetic fields above ground (1980)
    In:  Other Sources
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    Publikationsdatum: 2019-06-27
    Beschreibung: A lightning return stroke model with which the two station electric and magnetic fields measured at ground level can be reproduced is used to compute fields at altitudes up to 10 km and at ranges from 20 m to 10 km. These calculations provide the first detailed estimates of the return strokes fields that are encountered by aircraft in flight. With the advent of modern aircraft utilizing low voltage digital electronics and reduced electromagnetic shielding by way of structures containing advanced composite materials, these calculations are of considerable practical interest. Further, since airborne electric and magnetic field measurements are presently being attempted, a comparison of the calculations presented with appropriate experimental data, when they are available, will constitute a test of the return stroke model.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: NASA. Langley Res. Center Lightning Technol.; p 21-28
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 8
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    Lightning return stroke models (1980)
    In:  Other Sources
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    Publikationsdatum: 2019-06-27
    Beschreibung: We test the two most commonly used lightning return stroke models, Bruce-Golde and transmission line, against subsequent stroke electric and magnetic field wave forms measured simultaneously at near and distant stations and show that these models are inadequate to describe the experimental data. We then propose a new return stroke model that is physically plausible and that yields good approximations to the measured two-station fields. Using the new model, we derive return stroke charge and current statistics for about 100 subsequent strokes.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Geophysical Research; 85; Mar. 20
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 9
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    Correlated electric and magnetic fields from lightning return strokes (1975)
    In:  Other Sources
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    Publikationsdatum: 2019-06-27
    Beschreibung: The first broad band (1 kHz to 5 mHz) correlated measurements of electric and magnetic fields from close lightning return strokes are presented. Sample wave forms are shown for the distance range 2-200 km. The transmission line return stroke model is used to find a typical current wave shape and return stroke velocity from the experimental data, and theoretical curves are given of electric and magnetic field as a function of time for 1, 5, 10, and 100 km by using this typical current and velocity.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Geophysical Research; 80; Jan. 20
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 10
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    Electric field statistics for close lightning return strokes near Gainesville, Florida (1976)
    In:  Other Sources
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    Publikationsdatum: 2019-06-27
    Beschreibung: The salient properties of the electric field intensity from first and subsequent lightning return strokes in the 0-25 km distance range near Gainesville, Fla., are presented, including electric field wave shape versus distance, initial peak rise time versus distance, rise time histograms, initial peak magnitude versus distance, normalized (to 100 km) initial peak magnitude histograms, normalized initial peak magnitude versus rise time, ramp starting time versus distance, and field at 170 microsec versus distance. The mean normalized initial peak field for first return strokes was 9.9 V/m and for subsequent strokes, 5.7 V/m. The maximum measured values of normalized initial peak field were about 30 V/m. The largest field recorded at 170 microsec was about 25 kV/m generated by a first stroke within 0.5 km. Return strokes were found to lower a typical charge of the order of 1 C in 170 microsec.
    Schlagwort(e): METEOROLOGY AND CLIMATOLOGY
    Materialart: Journal of Geophysical Research; 81; Aug. 20
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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