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  • COMMUNICATIONS  (61)
  • PROPULSION SYSTEMS  (52)
  • ASTROPHYSICS
  • 1970-1974  (113)
  • 1955-1959
  • 1972  (113)
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  • 1970-1974  (113)
  • 1955-1959
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  • 1
    Publication Date: 2019-06-27
    Description: A preliminary mission study of a reusable vehicle from staging to orbit indicates payload advantages for a dual-propulsion system consisting of separate scramjet and rocket engines. In the analysis the scramjet operated continuously and the initiation of rocket operation was varied. For a stage weight of 500,000 lb the payload was 10.4 percent of stage weight or 70 percent greater than that of a comparable all-rocket-powered stage. When compared with a reusable two-state rocket vehicle having 50,000 lb payload, the use of the dual propulsion system for the second stage resulted in significant decreases in lift-off weight and empty weight, indicating possible lower hardware costs.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TN-D-6762 , E-6555
    Format: application/pdf
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  • 2
    Publication Date: 2019-07-13
    Description: Description of the transmitting and receiving system configurations to be used in an ATS-F propagation experiment designed to gather data on the attenuation of satellite uplink signals (at approximately 13.2 and 17.8 GHz) due to atmospheric hydrometeors (mostly rain). The data will be used for statistical determination of system power margins required for operational communications systems at frequencies above 10 GHz. A secondary analysis will study site diversity as a means of reducing the required system margins. A spacecraft transponder receives signals from 15 dual-frequency ground transmitter stations and retransmits these signals to a central ground receiving terminal at a frequency of 4 GHz.
    Keywords: COMMUNICATIONS
    Type: NTC ''72; National Telecommunications Conference; Dec 04, 1972 - Dec 06, 1972; Houston, TX
    Format: text
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  • 3
    Publication Date: 2019-06-27
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-20; Nov. 197
    Format: text
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  • 4
    Publication Date: 2019-07-13
    Description: The stabilizing influence of acoustic cavities (quarterwave acoustic resonators) on acoustic modes of combustion instability has been studied. The ability to analytically predict cavity damping was improved. Relatively good agreement between predicted damping and measured stability was demonstrated. Full-scale motor firings were made to evaluate the influence of several parameters on stability. Results from these firings showed that stability was changed, but not dramatically, by changes in the engine operating conditions. Variations in the film-coolant flowrate do not significantly affect cavity stabilization. The ability to stabilize an engine with unconventional cavity configurations was demonstrated.
    Keywords: PROPULSION SYSTEMS
    Type: AIAA PAPER 72-1147 , Joint Propulsion Specialist Conference; Nov 29, 1972 - Dec 01, 1972; New Orleans, LA; US
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  • 5
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    In:  CASI
    Publication Date: 2005-11-30
    Description: The selection and design of velocity diagrams for axial flow turbines are considered. Application is treated in two parts which includes: (1) mean-section diagrams, and (2) radial variation of diagrams. In the first part, the velocity diagrams occurring at the mean section are assumed to represent the average conditions encountered by the turbine. The different types of diagrams, their relation to stage efficiency, and their selection when staging is required are discussed. In the second part, it is shown that in certain cases the mean-section diagrams may or may not represent the average flow conditions for the entire blade span. In the case of relatively low hub- to tip-radius ratios, substantial variations in the velocity diagrams are encountered. The radial variations in flow conditions and their effect on the velocity diagrams are considered.
    Keywords: PROPULSION SYSTEMS
    Type: Turbine Design and Appl., Vol. 1; p 69-99
    Format: text
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  • 6
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    In:  CASI
    Publication Date: 2005-11-30
    Description: The purpose of the reported experiment was to determine the principal electromagnetic and structural properties of the lunar surface from the observation of command and service module (CSM) radio transmissions that were reflected from the lunar surface and received on earth. These transmissions emanate from the CSM communication systems at wavelengths of 13 cm (S-band) and 116 cm (very high frequency (VHF)). Lunar crustal properties such as dielectric constant, average slope and slope probability, density, small-scale surface roughness, and embedded rocks to a depth of 20 m may be determined. The results are proving to be most useful in understanding the processes that have produced and modified the crust and in distingushing between adjacent and subjacent geological units. The experimental observations are also of intrinsic interest in the study of electromagnetic scattering.
    Keywords: COMMUNICATIONS
    Type: NASA. Lyndon B. Johnson Space Center Apollo 16 Prelim. Sci. Rept.; 13 p
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  • 7
    Publication Date: 2006-03-12
    Description: There are two types of experimental measurement errors of the Doppler data associated with the radio occultation, random and systematic. Random errors are due to thermal noise in the transmission channel, and the phase lock loop, and quantization error in the digital circuitry. These are called noise type errors. The systematic errors are due to geometric uncertainty and equipment phase instability. Considered is the amount of uncertainty, due to random measurement errors, in the refractivity profiles reconstructed by this type of indirect sensing experiment. A class of refractivity profiles is defined which approximately fit the set of measured data. Bounds are placed on the extent of this class of solution profiles. To accomplish this, the sensivity of the reconstructed refractivity profiles to errors in the measured quantity and the statistics of the errors in the measurement are examined.
    Keywords: COMMUNICATIONS
    Type: NASA. Ames Res. Center Math. of Profile Inversion; 5 p
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  • 8
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    In:  CASI
    Publication Date: 2006-02-22
    Description: An estimate of the antenna noise temperature and the uplink signal-to-noise ratio has been made for Bremsstrahlung radiation emitted by a spacecraft ion beam; a worst-case situation in which the spacecraft antenna is located in the exit plane of the ion beam and directed at varying angles into the ion beam is assumed. Numerical results of the antenna noise temperature versus antenna pointing angle are given for a typical set of ion beam and antenna pattern parameters. The uplink signal-to-noise ratio due to the ion beam noise alone is given in terms of a critical range in AU at which a typical ranging transmission is received with S/N = 0 db. The effects of the ion beam divergence angle and antenna distance on the ion beam are also presented. Results of the study show typical increases in the antenna noise temperature of about 0.2 K and critical ranges of the order of 3-5 AU. An ion engine thus generally introduces an undetectable level of noise into a spacecraft receiver.
    Keywords: COMMUNICATIONS
    Type: JPL Quart. Tech. Rev., Vol. 2, No. 2; p 61-71
    Format: text
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  • 9
    Publication Date: 2006-02-22
    Description: On 14 November 1971 the Mariner 9 1334-N-(300-lbf)-thrust rocket engine was fired for just over 15 min to place the first man-made satellite into orbit about Mars. Propulsion subsystem data gathered during the 5-month interplanetary cruise and orbit insertion are of significance to future missions of this type. Specific results related to performance predictability, zero g heat transfer, and nitrogen permeation, diffusion, and solubility values are presented.
    Keywords: PROPULSION SYSTEMS
    Type: JPL Quarterly Tech. Rev., Vol. 2, No. 1; p 113-122
    Format: text
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  • 10
    Publication Date: 2011-08-16
    Description: Simultaneous measurements of radar reflectivity and radio refractive index at several altitudes in clear air convection have been made. The experimental data were compared with the theoretical relationship which relates the reflectivity to the refractivity spectrum. The agreement between the measurements and the theory is excellent and shows that the radar returns in clear air are the result of, and can be quantitatively described as being from, fine-scale refractivity fluctuations due to turbulent mixing. Further, the data give strong support to the -5/3 spectral decay of the refractivity spectrum in the inertial subrange.
    Keywords: COMMUNICATIONS
    Type: Journal of Applied Meteorology; 11; Oct. 197
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