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  • Chemistry  (10,579)
  • Polymer and Materials Science  (4,131)
  • General Chemistry  (1,786)
  • Analytical Chemistry and Spectroscopy  (831)
  • COMMUNICATIONS  (650)
  • PROPULSION SYSTEMS  (637)
  • Cell & Developmental Biology
  • 1980-1984
  • 1970-1974  (13,263)
  • 1960-1964
  • 1935-1939
  • 1973  (6,803)
  • 1970  (6,460)
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  • 1980-1984
  • 1970-1974  (13,263)
  • 1960-1964
  • 1935-1939
Year
  • 1
    Publication Date: 2005-11-30
    Description: The fixed and variable Martian features investigated by the TV experiment on Mariner 9 are described. Articles are presented concerning the dust storm of October to November over the Southern Hemisphere; global surface geodesy and cartography; geology; and the satellite astronomy.
    Keywords: COMMUNICATIONS
    Type: Mariner Mars 1971 Proj., Vol. 5; p 63-70
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  • 2
    Publication Date: 2006-04-05
    Description: A very broad band of electromagnetic radiation is emitted during solar flares, especially at the explosive phase. The existence of a large variety of plasmas with various densities and a wide range of temperatures or energies is proposed as the initiating agent. The manner in which the plasmas are heated and accelerated to subrelativistic and relativistic energies is discussed. Observational evidence on the characteristics of active regions which produced proton flares and on the structure of the associated nonthermal microwave bursts of the sun is presented. The behavior of subrelativistic electrons on the sun is described.
    Keywords: COMMUNICATIONS
    Type: NASA, Washington High Energy Phenomena on the Sun; p 78-86
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  • 3
    Publication Date: 2006-03-28
    Description: The application of vibroacoustic techniques for diagnosing aircraft engine malfunctions is discussed. An experiment was conducted to determine the defects introduced by the nature of change in the amplitude-frequency characteristics of the noises and vibrations of an aircraft jet engine. The manner in which the defects were simulated is explained. The test equipment used during the experiment is identified. The results of the amplitude-frequency characteristics investigation are summarized to show optimum location of the microphone pick-up to record the acoustic data.
    Keywords: PROPULSION SYSTEMS
    Type: Cybernetic Diagnostics of Mech. Systems with Vibro-acoustic Phenomena (NASA-TT-F-14899); p 317-319
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  • 4
    Publication Date: 2006-03-28
    Description: The effects of external mechanical and climatic actions on the efficient operation of magnetic tape recording equipment are analyzed. The efficiency and reliability of the recording system are determined by the structural parameters and the characteristics of the individual elements of the transport mechanism circuit. The resistance of tape recording equipment to the effects of vibration is considered essential for reliable operations. Methods for insuring reliable tape transport and recording action are discussed.
    Keywords: COMMUNICATIONS
    Type: Cybernetic Diagnostics of Mech. Systems with Vibro-acoustic Phenomena (NASA-TT-F-14899); p 271-274
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  • 5
    Publication Date: 2006-03-28
    Description: Problems in measurement of irregularities in angular velocity of rotating assemblies in memory devices with rigid and flexible magnetic data carriers are discussed. A device and method for determination of change in angular velocities in various frequency and rotation rate ranges are examined. A schematic diagram of a photoelectric sensor for recording the signal pulses is provided. Mathematical models are developed to show the amount of error which can result from misalignment of the test equipment.
    Keywords: COMMUNICATIONS
    Type: Cybernetic Diagnostics of Mech. Systems with Vibro-acoustic Phenomena (NASA-TT-F-14899); p 279-282
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  • 6
    Publication Date: 2006-03-28
    Description: The physics of noise formation in an internal combustion engine is discussed. A dependence of the acoustical radiation on the engine operating process, its construction, and operational parameters, as well as on the degree of wear on its parts, has been established. An example of tests conducted on an internal combustion engine is provided. A system for cybernetic diagnostics for internal combustion engines by vibroacoustical parameters is diagrammed.
    Keywords: PROPULSION SYSTEMS
    Type: Cybernetic Diagnostics of Mech. Systems with Vibro-acoustic Phenomena (NASA-TT-F-14899); p 247-249
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  • 7
    Publication Date: 2006-02-22
    Description: The development of a propulsion system that employs a detonating propellant is described, and the need for such a system and its use in certain planetary atmospheres are demonstrated. A theoretical formulation of the relevant gas-dynamic processes was developed, and a related series of experimental tests were pursued.
    Keywords: PROPULSION SYSTEMS
    Type: JPL Quart. Tech. Rev., Vol. 3, No. 2 (NASA-CR-133863); p 45-52
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  • 8
    Publication Date: 2006-04-05
    Description: High resolution position and spectrum measurements were made of a complex solar radio activity on January 14, 1971, from 1120 to 1130 UT. Positions were measured with 169 MHz Nancay E-W Radioheliograph, while dynamic spectra and polarization were observed with the 60-channel radiospectrograph of Nera. The radio event consisted of two closely similar groups of type 3 bursts and type 2-like details, and a stationary type 4 continuum, including some very clear pulsating structures. The general aspect of this activity is presented.
    Keywords: COMMUNICATIONS
    Type: NASA, Washington High Energy Phenomena on the Sun; p 610-614
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  • 9
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    Publication Date: 2006-04-05
    Description: Solar burst observations in the region above 10 GHz (wavelengths less than 3 cm.) are discussed. Observations have shown that many major solar events have large millimeter wave components. The total burst radio energy is frequently concentrated in this part of the spectrum. Graphs are presented showing the peak flux density spectrum for bursts on specific dates. Microwave burst mean duration is plotted as a function of the particle energy.
    Keywords: COMMUNICATIONS
    Type: NASA, Washington High Energy Phenomena on the Sun; p 114-123
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  • 10
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    Publication Date: 2006-01-11
    Description: The boundary-layer losses associated with the flow process in the blade channel are discussed. To determine the overall design point efficiency of a turbine, other losses must also be considered; these include tip clearance loss and disk friction loss. The sum of these losses normally comprises all the losses that are considered in the design of a full admission axial flow turbine. If, however, a partial admission turbine is being considered, there are additional losses that must be included. The partial admission losses usually considered are the pumping loss in the inactive blade channels and the filling-and-emptying loss in the blade passages as they pass through the admission arc. Finally, a loss that occurs at off-design operation of any turbine is the incidence loss.
    Keywords: PROPULSION SYSTEMS
    Type: Turbine Design and Appl., Vol. 2; p 125-148
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  • 11
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    Publication Date: 2006-01-11
    Description: The design of a proper blade profile requires calculation of the blade row flow field in order to determine the velocities on the blade surfaces. An analysis theory is presented for several methods used for this calculation and associated computer programs that were developed are discussed.
    Keywords: PROPULSION SYSTEMS
    Type: Turbine Design and Appl., Vol. 2; p 27-56
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  • 12
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    Publication Date: 2006-01-11
    Description: The design of turbine blading is considered that will produce the flow angles and velocities required by velocity diagrams consistent with the desired efficiency and/or number of stages. The determination of the size, shape, and spacing of the blades is fundamental.
    Keywords: PROPULSION SYSTEMS
    Type: Turbine Design and Appl. Vol. 2; p 1-25
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  • 13
    Publication Date: 2006-01-11
    Description: A comparison was made of the results for lunar surface roughness estimates and slope frequency distributions obtained by using photogrammetric techniques with those obtained by using bistatic radar. Three topics were discussed: (1) the form of the slope frequency distributions, (2) the change of roughness estimates of the lunar surface with scale, and (3) the magnitude of surface roughness.
    Keywords: COMMUNICATIONS
    Type: NASA. Johnson Space Center Apollo 17 Prelim. Sci. Rept.; 9 p
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  • 14
    Publication Date: 2006-01-11
    Description: An examination was made of radar data on depolarized radar echoes for the general areas of (1) the Apollo 11, 12, 14, 15, 16, and 17 landing sites, (2) Ranger 7, 8, and 9 impact sites, and (3) the Surveyor 1, 3, 5, and 7 landing sites. These data were then compared with photographic data. Surveyor 6 was excluded because it landed near the center of the lunar disk where echo data are poor. Three problems concerning the echo data are (1) the frequency distributions of echo strengths from site to site, (2) the areal distribution of echoes, and (3) detailed correlation of echoes with the photographs of the Apollo 17 landing area.
    Keywords: COMMUNICATIONS
    Type: NASA. Johnson Space Center Apollo 17 Prelim. Sci. Rept.; 7 p
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  • 15
    Publication Date: 2006-01-10
    Description: The feasibility of operating small rocket engines in the Molsink facility was demonstrated. A 0.44-N (0.1-lbf) hydrazine engine and a 0.18-N (0.04-lbf) thruster using cold gas from a hydrazine plenum system were operated for both flight duty cycles and off-nominal conditions. The exhaust gases from these thrusters contain NH3, N2, and H2. The chamber was also calibrated for larger bipropellant engines using nitrogen tetroxide/monomethyl hydrazine (NTO/MMH). The exhaust products of these engines contain CO2, CO, H2, H2O, and H2. A mixture of cold gases simulating the engine exhaust was injected through a nozzle under conditions simulating thrust levels up to 26.7-N (6 lbf). Pulsing and continuous operations were investigated. The chamber background pressure traces were compared with the traces obtained for the same thrusters operated with pure nitrogen at approximately equivalent thrust. Satisfactory recuperation times were encountered in all the pulsing modes. Test times greater than 20s were obtained in steady state operation before the vacuum chamber back pressure climbed to prohibitive values.
    Keywords: PROPULSION SYSTEMS
    Type: JPL Quart. Tech. Rev., Vol. 3, No. 1; p 1-13
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  • 16
    Publication Date: 2006-04-05
    Description: High resolution dynamic spectra of solar emissions in the range 80 to 20 MHz are discussed. The major features of observations described are (1) decametric storms, (2) type 3 bursts, and (3) time profile of type 3 bursts.
    Keywords: COMMUNICATIONS
    Type: NASA, Washington High Energy Phenomena on the Sun; p 602-609
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  • 17
    Publication Date: 2006-04-05
    Description: The potential value of traveling solar radio bursts for investigating energetic particle propagation, and for probing the interplanetary medium is discussed. A general survey of the characteristics of type 3 radio phenomena observed at hectometer and kilometer wavelengths is presented along with a brief discussion of the relationships among type 1 meter noise storms, decametric continuum, and type 3 hectometric storms. Type 3 bursts are analyzed to show how these data provide information about the average energy, dispersion, and trajectory of energetic particles, the interplanetary scale, and magnetic field configuration. The recent observations of type 2 shock wave phenomena at kilometer wavelengths are described, and current research and the direction of future observation are outlined.
    Keywords: COMMUNICATIONS
    Type: High Energy Phenomena on the Sun; p 519-536
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  • 18
    Publication Date: 2006-03-28
    Description: Graphical plotting of the dynamic instability is used to diagnose carrier behavior according to a given carrier tension fluctuation spectrum.
    Keywords: COMMUNICATIONS
    Type: Cybernetic Diagnostics of Mech. Systems with Vibro-acoustic Phenomena (NASA-TT-F-14899); p 107-109
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  • 19
    Publication Date: 2006-03-27
    Description: Based on limited data, the Mariner 9 performance appears consistent throughout its mission. Several corrections have been provided by inflight verification sequences. A change in photometric response, which will impair precise photometric analysis, has been observed. Hence, only qualified photometric measurement appears feasible under limited conditions. Conversely, certain geometric and electronic parameters appear both measurable and congruent with preflight prediction. The role of inflight verification has been emphasized by these data to assess the in situ camera health and to promote efficient data analysis and interpretation.
    Keywords: COMMUNICATIONS
    Type: Mariner Mars 1971 Proj., Vol. 4; p 499-510
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  • 20
    Publication Date: 2006-04-05
    Description: Polarization properties of active regions at 9 mm are discussed, and the observed degree of polarization is used to obtain an estimate of chromospheric magnetic fields. Also discussed is the polarization structure at 9 mm of an active region that produced a minor flare around 1900 UT on September 28, 1971. Total power observations indicate that new regions develop, or weak regions intensify at millimeter wavelengths as a result of bursts at distant sites. The spectra of the peak flux density of moderately strong bursts observed at 9 mm show a sharp drop toward the shorter millimeter wavelengths. The weak bursts at 3.5 mm are manifest mainly as heating phenomena.
    Keywords: COMMUNICATIONS
    Type: NASA, Washington High Energy Phenomena on the Sun; p 104-113
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  • 21
    Publication Date: 2006-04-05
    Description: Various statistical parameters of the peak flux-density spectra of solar microwave bursts have been examined for 1968 to 1971 based on spectra obtained from fixed-frequency observations at 245, 606, 1415, 2695, 4995, 8800, 15400, and 35000 MHz. For bursts having a centimeter-radiation component, the great majority were found to have type C spectra (single spectral maximum) in the L-band to K-band range. A small percentage had miscellaneous type spectra (more than one spectral maximum) and another small percentage had what might be taken as thermal spectra. Even for gradual rise-and-fall bursts often thought to be thermal origin, less than 20 percent were found to have spectra which could be classified as thermal. The relationship between the burst spectral maximum (f sub max) and the photospheric magnetic field strength of the region associated with the burst was examined. A tendency for greater correlation at higher f sub max for stronger magnetic fields is noted; however, this is over-shadowed by the overall high correlations for those regions having strong photospheric magnetic fields.
    Keywords: COMMUNICATIONS
    Type: NASA, Washington High Energy Phenomena on the Sun; p 87-103
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  • 22
    Publication Date: 2011-08-16
    Description: The historical background concerning the application of liquid propellant rockets is considered. Progress to date in chemical liquid propellant rocket engines can be summarized as an increase in performance through the use of more energetic propellant combinations and increased combustion pressure. New advances regarding liquid propellant rocket engines are related to the requirement for reusability in connection with the development of the Space Shuttle.
    Keywords: PROPULSION SYSTEMS
    Type: AIAA Student Journal; 11; Dec. 197
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  • 23
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    Publication Date: 2011-08-16
    Description: Review of the major goals, procedures, and results of the Quiet Engine Program that was initiated four years ago and is now nearing completion. This program has developed and demonstrated, in full-scale, experimental engine tests, technology advances which, if applied to the design of future aircraft, will help produce equipment with noise levels considerably lower than the older narrow-body aircraft and significantly lower than the new wide-body aircraft flying at present. However, the application of this noise reduction technology will result in increases in aircraft operating costs. Future aircraft noise reduction research should, therefore, consider improvements in the economics associated with noise reduction technology.
    Keywords: PROPULSION SYSTEMS
    Type: Noise Control Engineering; 1; Autumn 1
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  • 24
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    Publication Date: 2011-08-16
    Description: After a review of the work of the late-Fifties on free radicals for propulsion, it is concluded that atomic hydrogen would provide a potentially large increase in specific impulse. Work conducted to find an approach for isolating atomic hydrogen is considered. Other possibilities for obtaining propellants of greatly increased capability might be connected with the technology for the generation of activated states of gases, metallic hydrogen, fuels obtained from other planets, and laser transfer of energy.
    Keywords: PROPULSION SYSTEMS
    Type: Astronautics and Aeronautics; 11; Dec. 197
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  • 25
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    Publication Date: 2011-08-16
    Description: The solution to the equation governing the propagation of sound in a uniform shear layer is expressed in terms of parabolic cylinder functions. This result is used to develop a closed-form solution for acoustic wall impedance which accounts for both the duct liner and the presence of a boundary layer in the duct. The effective wall impedance can then be used as the boundary condition for the much simpler problem of sound propagation in uniform flow.
    Keywords: PROPULSION SYSTEMS
    Type: Journal of Sound and Vibration; 30; Sept. 8
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  • 26
    Publication Date: 2011-08-16
    Description: System performance is determined for an optical communication system using noncoherent detection in the presence of tracking error induced signal fading assuming (1) binary on-off modulation (OOK) with both fixed and adaptive threshold receivers, and (2) binary polarization modulation (BPM). BPM is shown to maintain its inherent 2- to 3-dB advantage over OOK when adaptive thresholding is used, and to have a substantially greater advantage when the OOK system is restricted to a fixed decision threshold.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Communications; COM-21; Sept
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  • 27
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    Publication Date: 2011-08-16
    Description: A radio-sky map, covering the whole celestial sphere, is helpful for determining the system noise temperature of an earth-based satellite receiving system. Detailed sky maps for the 136- and 400-MHz space research (space-to-earth) satellite frequency bands have been generated, using a computer, by the National Aeronautics and Space Administration (NASA).
    Keywords: COMMUNICATIONS
    Type: IEEE; vol. 61
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  • 28
    Publication Date: 2011-08-16
    Description: Preemphasis schedules are given for 11 constant-bandwidth FM subcarriers modulating an S-band transmitter at various receiver SNRs (9 dB, 15 dB and 25 dB). The criterion for establishing these preemphasis curves is the achievement, at various receiver IF SNR, of equal receiver output SNR for all channels. The empirically derived results are compared with a simplified, analytically derived schedule and the primary differences are explained. The S-band preemphasis schedule is also found to differ from the lower frequency VHF case.
    Keywords: COMMUNICATIONS
    Type: Telemetry Journal; 8; Dec
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  • 29
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    Publication Date: 2011-08-16
    Description: Telecommunication network concepts are discussed together with carrier-tracking loops employing the phase-lock principle, phase and Doppler measurements in two-way phase-coherent tracking systems, range measurements by phase-coherent techniques, and questions of phase-coherent detection with perfect reference signals and with noisy reference signals. The design of one-way and two-way phase-coherent communication systems is considered, giving attention to the optimal design of single-channel systems, the design of two-channel systems, and the design of multichannel systems. Other topics explored include the design and the performance of phase-coherent systems preceded by band-pass limiters, symbol synchronization and its effects on data detection, noncoherent communication over the Gaussian channel, and tracking loops with improved performance.
    Keywords: COMMUNICATIONS
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  • 30
    Publication Date: 2011-08-16
    Description: The Lynch-Davisson (L-D) code is shown to be efficient for compressing line-scanned weather charts wherein each line is divided into equal-length segments, and a separate L-D code is generated for each segment. As the number of segments increases, the L-D code length decreases appreciably, thereby simplifying the encoding and decoding operations. However, the accompanying decrease in the overall compression ratio is relatively small.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Communications; COM-21; June 197
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  • 31
    Publication Date: 2011-08-16
    Description: An amplitude control technique has been employed for use with analog voice communication systems, which improves low-level phoneme reception and eliminates the received noise between words and syllables. Tests were conducted on a narrow-band frequency-modulation simplex voice communication channel employing the amplitude control technique. Presented for both the modified rhyme word tests and the phonetically balanced word tests are a series of graphical plots of the tests' score distribution, mean, and standard deviation as a function of received carrier-to-noise power density ratio. At low received carrier-to-noise power density ratios, a significant improvement in the intelligibility was obtained. A voice intelligibility improvement of more than 2 dB was obtained for the modified rhyme test words, and a voice intelligibility improvement in excess of 4 dB was obtained for the phonetically balanced word tests.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Communications; COM-21; May 1973
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  • 32
    Publication Date: 2011-08-16
    Description: Apollo 16 and 17 Lunar Rover position history while transporting astronauts over the lunar surface has been determined to a resolution of better than 1 m and uncertainties of less than 25 m utilizing a specialized very-long baseline interferometry (VLBI) tracking technique. This paper describes the technique, discusses the National Aeronautics and Space Administration worldwide tracking system used to obtain data, discusses the data, and presents results.
    Keywords: COMMUNICATIONS
    Type: IEEE; vol. 61
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  • 33
    Publication Date: 2011-08-16
    Description: One of the fundamental technical problems in aeronautical digital communications is that of multipath propagation between aircraft and ground terminal. This paper examines in detail a model of the received multipath signal that is useful for application of modern detection and estimation theories. The model treats arbitrary modulation and covers the selective and nonselective cases. The necessarily nonstationary statistics of the received signal are determined from the link geometry and the surface roughness parameters via a Kirchhoff solution.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Communications; COM-21; May 1973
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  • 34
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    Publication Date: 2011-08-16
    Description: Discussion of the improvements incorporated since 1969 in a low-power MPD thruster design which is considered a potential candidate for satellite station keeping and attitude control. The improvements include a new cathode design, and changes in thruster geometry, with xenon used as the propellant. A better thermal design is found to be necessary for further improvement of the thruster.
    Keywords: PROPULSION SYSTEMS
    Type: Journal of Spacecraft and Rockets; 10; Jan. 197
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  • 35
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    Publication Date: 2011-08-16
    Description: Consideration of three alternate definitions of cross-polarization known to the author. The three definitions are expressed precisely in terms of the same antenna pattern coordinate system, and the relative merits of the various definitions are discussed. One of the definitions is shown to be the proper choice for describing source current polarizations, another is suitable for relating source current distributions to secondary patterns, and the third is the best choice for describing antenna patterns.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-21; Jan. 197
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  • 36
    Publication Date: 2016-03-01
    Description: Bandwidth constraints in earth-satellite communication systems force consideration of uncoded M-ary modulation to obtain increased data rates. M-ary phase shift keying (MPSK) at first glance seems most promising because of the high transmitter efficiency achieved through Class C operation. Multiple phase-and-amplitude modulation candidates such as quadrature amplitude shift keying (QASK) appear less promising because the transmitter must operate at lower efficiency (in linear or multimode operation). However, initial studies indicate that QASK offers significant raw dc-power savings over MPSK, despite the reduced transmitter efficiency. For example, at S-band both solid-state and traveling wave tube (TWT) QASK transmitters can provide a 3-dB average dc-power savings over comparable 16-ary phase shift keying (PSK) for the same bit rate and error probability. The reason for this savings is that QASK requires much less average signal-to-noise ratio than 16-ary PSK for the same error rate.
    Keywords: COMMUNICATIONS
    Type: JPL Quart. Tech. Rev.; Vol. 2; No. 4; p 62-71
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  • 37
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    Publication Date: 2011-08-16
    Description: Demonstration of the value of cross-correlation signal enhancement achieved by means of a dual magnetometer system. A unique feature of a dual magnetometer system is, as pointed out by Ness et al. (1971), the opportunity it allows for signal enhancement by using cross-correlation techniques developed in statistical communication theory. Their use is shown to make it possible to overcome the limitations that the intrinsic sensor ambient noise and the measurement-contaminating spacecraft field fluctuations impose upon the signal detection performance of a single magnetometer.
    Keywords: COMMUNICATIONS
    Type: Journal of Geophysical Research; 78; Apr. 1
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  • 38
    Publication Date: 2011-08-16
    Description: The intense noise bands occurring near the upper hybrid resonance frequency have been observed with the Imp 6 GSFC radio astronomy experiment in the plasmasphere. The identification of the upper hybrid resonance provides an accurate measure of the local electron density and allows the observed noise data to be fit to the scale of characteristic frequencies in the plasma. The data are consistent with earlier theoretical interpretations in which noise is generated between the upper hybrid and plasma frequencies and propagates to region 4 of the CMA diagram, where it is reflected at the L = 0 plasma cutoff.
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    Type: Journal of Geophysical Research; 78; Apr. 1
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  • 39
    Publication Date: 2011-08-16
    Description: Significant improvement in the signal-to-noise performance of television signals has been obtained through the application of comb filtering techniques. This improvement is achieved by removing the inherent redundancy in the television signal through linear prediction and by utilizing the unique noise-rejection characteristics of the receiver comb filter. Theoretical and experimental results describe the signal-to-noise ratio and picture-quality improvement obtained through the use of baseband comb filters and the implementation of a comb network as the loop filter in a phase-lock-loop demodulator. Attention is given to the fact that noise becomes correlated when processed by the receiver comb filter.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Communications; COM-21; Apr. 197
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  • 40
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    Publication Date: 2011-08-16
    Description: Two experimental Quiet Engines using derated CF6 cores are discussed. One engine has a low-speed fan running at a tip speed of 1160 fps; the other engine has a fan running at the high speed of 1550 fps. The two engines are expected to show the relative advantages of fans operating at low tip speeds with high lift coefficients in comparison with fans operating at high tip speeds with low lift coefficients. Test results obtained with full-scale (6-ft diameter) fans are examined.
    Keywords: PROPULSION SYSTEMS
    Type: Astronautics and Aeronautics; 11; Jan. 197
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  • 41
    Publication Date: 2011-08-16
    Description: The nonducted propagation of artificial VLF waves through the magnetosphere has been studied by means of data obtained by the FR-1 satellite experiment, in which fixed frequency (16.8 kHz) waves radiated by a transmitter at the ground (at L equals 2.1) are received by the satellite, at 750 km altitude, both in the zone close to the transmitter and in the conjugate zone. From the wave-normal directions and Doppler shifts measured in the conjugate zone, it has been possible to identify waves that have been propagated from the Northern to the Southern Hemisphere in both ducted and nonducted modes. In this paper, the main features of the nonducted wave have been interpreted by ray tracing in models of the magnetosphere. The results improve our understanding as to why very few whistlers are observed on the ground at low latitudes.
    Keywords: COMMUNICATIONS
    Type: Journal of Atmospheric and Terrestrial Physics; 35; Jan. 197
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  • 42
    Publication Date: 2012-05-22
    Description: Various techniques and test results are briefly described and referenced for detail. The effort arises from the increasing concern for the measurement and control of emissions from gas turbine engines. The greater part of this research is focused on reducing the oxides of nitrogen formed during takeoff and cruise in both advanced CTOL, high pressure ratio engines, and advanced supersonic aircraft engines. The experimental approaches taken to reduce oxides of nitrogen emissions include the use of: multizone combustors incorporating reduced dwell time, fuel-air premixing, air atomization, fuel prevaporization, water injection, and gaseous fuels. In the experiments conducted to date, some of these techniques were more successful than others in reducing oxides of nitrogen emissions. Tests are being conducted on full-annular combustors at pressures up to 6 atmospheres and on combustor segments at pressures up to 30 atmospheres.
    Keywords: PROPULSION SYSTEMS
    Type: AGARD Atmospheric Pollution by Aircraft Engine; 8 p
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  • 43
    Publication Date: 2012-05-23
    Description: Radio wave propagation in the 40- to 140-GHz band through the earth's atmosphere is strongly influenced by the behavior of the O2 microwave spectrum. This behavior causes the transfer function to depend critically upon altitude. The spectroscopic properties of O2 are discussed and reduced to engineering formulas expressing attenuation and phase dispersion rates in terms of frequency and meteorological parameters. The theory is supported on several accounts by reliable spectroscopic measurements. Pressure scanning spectroscopy is used to investigate the O2 microwave spectrum under simulated atmospheric conditions. The application of spectroscopic information to analytical treatments of transfer properties for inhomogeneous slant paths is demonstrated. Attenuation and phase dispersion between 49 and 72 GHz are evaluated for zenith and tangential paths.
    Keywords: COMMUNICATIONS
    Type: AGARD Telecommun. Aspects on Freq. Between 10 and 100 GHz; 18 p
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  • 44
    Publication Date: 2012-05-23
    Description: The procedures for selecting engines for transport and combat aircraft during the design process are presented. The types of aircraft considered are: (1) a long haul conventional takeoff and landing transport, (2) a short haul vertical takeoff and landing transport, (3) a long range supersonic transport, and (4) a fighter aircraft. The influence of aircraft noise considerations on engine selection is examined. The aerodynamic characteristics of supercritical wings and their effect on engine selection are reported.
    Keywords: PROPULSION SYSTEMS
    Type: AGARD Aircraft Performance: Prediction Methods and Optimization; 55 p
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  • 45
    Publication Date: 2016-06-07
    Description: An amplitude control technique is reported that equalizes low level phonemes in a satellite narrow band FM voice communication system over channels having low carrier to noise ratios. This method presents at the transmitter equal amplitude phonemes so that the low level phonemes, when they are transmitted over the noisey channel, are above the noise and contribute to output intelligibility. The amplitude control technique provides also for squelching of noise when speech is not being transmitted.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., 1972; p 195-198
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  • 46
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    In:  CASI
    Publication Date: 2016-06-07
    Description: Long term experimental measurements to determine the propagation characteristics of 15 and 32 GHz earth-space links and to evaluate performance characteristics of operational millimeter wave systems are reported. The ATS 5 millimeter wave experimental link experienced attenuation and fading characteristics as a function of rainfall rate and other meteorological parameters. A method of site selection for the lowest attenuation rainfall rate improved reception tremendously.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., 1972; p 171-174
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  • 47
    Publication Date: 2016-06-07
    Description: A global rain rate statistic model is used to link microwave propagation statistics to measurable rain statistics in order to develop international telecommunication site criteria for radio relay and communication satellite services that minimize interference between receivers and transmitters. This rain coordination procedure utilizes a rain storm cell size, a statistical description of the rainfall rate within the cell valid for most of the earth's surface, approximations between Raleigh scatter and constancy of precipitation with altitude, and an analytic relation between radar reflectivity and rain rate.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., 1972; p 175-178
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  • 48
    facet.materialart.
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    In:  CASI
    Publication Date: 2016-06-07
    Description: It is demonstrated that state-of-the-art communications technology can be implemented and reliably operated on a global basis to increase the transmission rates and efficiencies on circuits with bandwidths greater than the typical speech channel. Optimization is affected by optimum clock recovery procedures, multilevel pulse amplitude modulation, single sideband amplitude modulation, transversal filter equalizers, data scrambling, and active compensation for phase instability.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., 1972; p 113-115
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  • 49
    Publication Date: 2016-06-07
    Description: A data compression system has been operating since February 1972, using ATS spin-scan cloud cover data. With the launch of ITOS 3 in October 1972, this data compression system has become the only source of near-realtime very high resolution radiometer image data at the data processing facility. The VHRR image data are compressed and transmitted over a 50 kilobit per second wideband ground link. The goal of the data compression experiment was to send data quantized to six bits at twice the rate possible when no compression is used, while maintaining zero error between the transmitted and reconstructed data. All objectives of the data compression experiment were met, and thus a capability of doubling the data throughput of the system has been achieved.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., 1972; p 199-204
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  • 50
    facet.materialart.
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    In:  CASI
    Publication Date: 2016-06-07
    Description: The use of ATS 6 spacecraft in a general telecommunication link for the health/education experiment demonstrates the feasibility of the small receiver-only terminal consisting of a ten foot diameter antenna located on a three-legged mount. The terminal is capable of 0 to 70 degrees elevation, course adjustment, and a plus or minus 5 degree elevation vernier adjustment. Its tuned radio frequency receiver utilizes a cavity back dipole feed and a preamplifier. The indoor unit provides further RF gain and drives a wideband limiter-discriminator.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., 1972; p 204-207
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  • 51
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    In:  CASI
    Publication Date: 2016-06-07
    Description: The simulation of an adaptive ground implemented phased array of five antenna elements is reported for a very high frequency system design that is tolerant to the radio frequency interference environment encountered by a tracking data relay satellite. Signals originating from satellites are received by the VHF ring array and both horizontal and vertical polarizations from each of the five elements are multiplexed and transmitted down to ground station. A panel on the transmitting end of the simulation chamber contains up to 10 S-band RFI sources along with the desired signal to simulate the dynamic relationship between user and TDRS. The 10 input channels are summed, and desired and interference signals are separated and corrected until the resultant sum signal-to-interference ratio is maximized. Testing performed with this simulation equipment demonstrates good correlation between predicted and actual results.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., 1972; p 103-108
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  • 52
    facet.materialart.
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    In:  CASI
    Publication Date: 2016-06-07
    Description: The ERTS video bandwith tape recorder uses a rotary head to run the tape in transverse mode; the head wheel gives a head-to-tape surface speed of nearly 5080 centimeter per second. The electronics unit handles 15 megabit per second rate with a bit-error rate of 0.00001. An operational unit onboard ERTS A returned images from the 85 to 90 percent of the earth that are not available in real time.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., 1972; p 67-70
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  • 53
    Publication Date: 2019-06-27
    Description: The Velocity Control Propulsion Subsystem (VCPS) was designed the propulsion required for trajectory and lunar orbit corrections of the spacecraft. A GFE clamp assembly physically attaches the VCPS to the spacecraft and the unit is ejected after completing the required corrections. The VCPS is physically and functionally separated from the spacecraft except for the electrical and telemetry interfaces. A GFE transtage provides the superstructure on which the VCPS is assembled. The subsystem consists of two 5 foot pound rocket engine assemblies, 4 propellant tanks, 2 latching valves, 2 fill and drain valves, a system filter, pressure transducer, gas and propellant manifolds and electrical heaters and thermostats. The RAE-B VCPS program covered the design, manufacture and qualification of one subsystem. This subsystem was to be manufactured, subjected to qualification tests; and refurbished, if necessary, prior to flight. The VCPS design and test program precluded the need for refurbishing the subsystem and the unit was delivered to GSFC at the conclusion of the program.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-132905 , SVHSER-6226
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  • 54
    Publication Date: 2019-06-27
    Description: A preliminary design was completed for an O2/H2, 89 kN (20,000 lb) thrust staged combustion rocket engine that has a single-bell nozzle with an overall expansion ratio of 400:1. The engine has a best estimate vacuum specific impulse of 4623.8 N-s/kg (471.5 sec) at full thrust and mixture ratio = 6.0. The engine employs gear-driven, low pressure pumps to provide low NPSH capability while individual turbine-driven, high-speed main pumps provide the system pressures required for high-chamber pressure operation. The engine design dry weight for the fixed-nozzle configuration is 206.9 kg (456.3 lb). Engine overall length is 234 cm (92.1 in.). The extendible nozzle version has a stowed length of 141.5 cm (55.7 in.). Critical technology items in the development of the engine were defined. Development program plans and their costs for development, production, operation, and flight support of the ASE were established for minimum cost and minimum time programs.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-121237 , PWA-FR-5654
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  • 55
    Publication Date: 2019-06-27
    Description: A review of typical surveillance and monitoring practices followed during the flight phases of representative solid-propellant upper stages and apogee motors was conducted to evaluate the need for improved flight diagnostic instrumentation on future spacecraft. The capabilities of the flight instrumentation package were limited to the detection of whether or not the solid motor was the cause of failure and to the identification of probable primary failure modes. Conceptual designs of self-contained flight instrumentation packages capable of meeting these reqirements were generated and their performance, typical cost, and unit characteristics determined. Comparisons of a continuous real time and a thresholded hybrid design were made on the basis of performance, mass, power, cost, and expected life. The results of this analysis substantiated the feasibility of a self-contained independent flight instrumentation module as well as the existence of performance margins by which to exploit growth option applications.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-136561 , JPL-TM-33-656
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  • 56
    Publication Date: 2019-06-27
    Description: The performance of command and telemetry systems, useful in deep-space communications, is frequently affected by the radio-frequency phase error which is introduced at the point of reception by means of the carrier tracking loop. In low data rate communications, this phase error may vary rapidly over the duration of the signaling interval. In this paper such phase variation is characterized by a sinusoidal input phase, K sin (omega sub o t+, pi/6), which models a typical phase variation in communication over turbulent media. Conditions for synchronization stability and the acquisition behavior are examined by detailed computer study of the phase-plane trajectories for the second and third-order loops with perfect integrator. It is demonstrated that for the phase variation considered the third-order loop has no real advantage over the second-order loop. Finally, it is shown that nonzero initial conditions may result in large steady-state phase error.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-132889 , EE-209(73)
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  • 57
    Publication Date: 2019-06-27
    Description: An S-band tracking system employing one way Doppler applicable to the tracking and data relay system (TDRS) was evaluated. This evaluation is limited to the measurement system parameters. The analysis assumes state-of-the-art components such as spacecraft oscillator long term stability of one part in 10 to the 8th power and ground station oscillator stability of one part in 10 to the 11th power. Signal characteristics comparable with the present ranging systems are utilized in the analysis. Predicated upon measurement system parameters, position uncertainties for the low orbiting spacecraft vary from 5 meters to 2 kilometers along track, 4 meters to 1 kilometer cross track, and 1 meter to 180 meters radially depending upon the tracking geometry and the high satellite position and velocity error assumptions.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-70526 , X-591-73-307
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  • 58
    Publication Date: 2019-06-27
    Description: Rain scatter and surface rain rate data were obtained from October 3, 1970 to October 2, 1971 using a bistatic radar system and tipping bucket rain gauges located in southeastern Virginia. The data showed that interference may occur between earth and terrestrial stations located within 80 km of each other either by mainlobe-to-mainlobe coupling or sidelobe-to-mainlobe coupling. The data further show that the distributions of scattering cross section per unit volume measured at several heights and estimated from surface rain gauge data were different. The density functions for the scattering cross section per unit volume values measured at a 3 km height and estimated from surface rain rate data were identical only for summer thundershowers. The data showed that the CCIR model used to estimate interference due to rain is inadequate because the cell size and change of scattering cross section per unit volume with height estimates of the model predict transmission loss values that are too low (more interference than will occur).
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-70457 , X-750-73-55-REV
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  • 59
    Publication Date: 2019-06-27
    Description: A class of detection-estimation problems on matrix Lie groups is defined in which the observation noise is multiplicative in nature. By examining the differential versions of the hypotheses, which are bilinear in nature, it is possible to derive the relevant likelihood ratio formula and the associated optimal estimation equations for the signal given the observations and the assumption that the signal is present. These estimation equations are of interest in their own right, in that they represent a finite dimensional optimal solution to a nonlinear estimation problem and can be viewed as consisting of a Kalman-Bucy filter along with the on-line computation of the solution of the associated Riccati equation, which is driven by the observations. The usefulness of these results is illustrated via an example concerning the detection of an actuator failure in a rigid body rotational control system.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-136301 , ESL-P-521
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  • 60
    Publication Date: 2019-06-27
    Description: A fixed-beam bistatic CW experiment designed to measure the temporal statistics of the volume reflectivity produced by hydrometeors at several selected altitudes, scattering angles, and at two frequencies (3.6 and 7.8 GHz) is described. Surface rain gauge data, local meteorological data, surveillance S-band radar, and great-circle path propagation measurements were also made to describe the general weather and propagation conditions and to distinguish precipitation scatter signals from those caused by ducting and other nonhydrometeor scatter mechanisms. The data analysis procedures were designed to provide an assessment of a one-year sample of data with a time resolution of one minute. The cumulative distributions of the bistatic signals for all of the rainy minutes during this period are presented for the several path geometries.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-136275 , OT-15
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  • 61
    Publication Date: 2019-06-27
    Description: A major achievement of the F-24 experiment on OGO 6 was a verification of the theory of the polarization of proton whistlers. As predicted, the electron whistler was found to be right-hand polarized and the proton whistler left hand polarized. The transition from right- to left-hand polarization was found to occur very rapidly. Thus it appears that the experimental technique may allow great accuracy in the measurement of the cross-over frequency, a frequency that provides information on the ionic composition of the ionosphere.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-132882 , NSSDC-ID-69-051A-24-PM
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  • 62
    Publication Date: 2019-06-27
    Description: The capabilities and limitations of the various published computer programs for fixed/broadcast communication satellite system synthesis and optimization are discussed. A satellite Telecommunication analysis and Modeling Program (STAMP) for costing and sensitivity analysis work in application of communication satellites to educational development is given. The modifications made to STAMP include: extension of the six beam capability to eight; addition of generation of multiple beams from a single reflector system with an array of feeds; an improved system costing to reflect the time value of money, growth in earth terminal population with time, and to account for various measures of system reliability; inclusion of a model for scintillation at microwave frequencies in the communication link loss model; and, an updated technological environment.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-136201 , R(T)-73/2
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  • 63
    Publication Date: 2019-06-27
    Description: An axial flow compressor stage, having single-airfoil blading, was designed for zero rotor prewhirl, constant rotor work across the span, and axial discharge flow. The stage was designed to produce a pressure ratio of 1.265 at a rotor tip velocity of 757 ft/sec. The rotor had an inlet hub/tip ratio of 0.8. The design procedure accounted for the rotor inlet boundary layer and included the effects of axial velocity ratio and secondary flow on blade row performance. The objectives of this experimental program were: (1) to obtain performance with uniform and distorted inlet flow for comparison with the performance of a stage consisting of tandem-airfoil blading designed for the same vector diagrams; and (2) to evaluate the effectiveness of accounting for the inlet boundary layer, axial velocity ratio, and secondary flows in the stage design. With uniform inlet flow, the rotor achieved a maximum adiabatic efficiency of 90.1% at design equivalent rotor speed and a pressure ratio of 1.281. The stage maximum adiabatic efficiency at design equivalent rotor speed with uniform inlet flow was 86.1% at a pressure ratio of 1.266. Hub radial, tip radial, and circumferential distortion of the inlet flow caused reductions in surge pressure ratio of approximately 2, 10 and 5%, respectively, at design rotor speed.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-134511 , PWA-FR-5852-PT-6
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  • 64
    Publication Date: 2019-06-27
    Description: This report summarizes the design, fabrication and test results obtained for glass-ceramic (CER-VIT) automotive thermal reactors. Several reactor designs were evaluated using both engine-dynamometer and vehicle road tests. A maximum reactor life of about 330 hours was achieved in engine-dynamometer tests with peak gas temperatures of about 1065 C (1950 F). Reactor failures were mechanically induced. No evidence of chemical degradation was observed. It was concluded that to be useful for longer times, the CER-VIT parts would require a mounting system that was an improvement over those tested in this program. A reactor employing such a system was designed and fabricated.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-134513
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  • 65
    Publication Date: 2019-06-27
    Description: Calculations of exhaust emissions from a scramjet powered hypersonic transport burning hydrogen fuel were performed over a range of Mach numbers of 5 to 12 to provide input data for wake mixing calculations and forecasts of future levels of pollutants in the stratosphere. The calculations were performed utilizing a one-dimensional chemical kinetics computer program for the combustor and exhaust nozzle of a fixed geometry dual-mode scramjet engine. Inlet conditions to the combustor and engine size was based on a vehicle of 227,000 kg (500,000 lb) gross take of weight with engines sized for Mach 8 cruise. Nitric oxide emissions were very high for stoichiometric engine operation but for Mach 6 cruise at reduced equivalence ratio are in the range predicted for an advanced supersonic transport. Combustor designs which utilize fuel staging and rapid expansion to minimize residence time at high combustion temperatures were found to be effective in preventing nitric oxide formation from reaching equilibrium concentrations.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-71464 , E-7760
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  • 66
    Publication Date: 2019-06-27
    Description: The convolutional coding study on the IME Mother-Daughter and Heliocentric spacecraft is reported. The three major tasks involved in the study are summarized.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-132880 , ASAO-PR20046-4-VOL-1
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  • 67
    Publication Date: 2019-06-27
    Description: Solutions were obtained of the wave equation for a plane horizontally polarized electro-magnetic wave incident on a semi infinite two dimensional inhomogeneous medium. Two problems were considered: An inhomogeneous half space, and an inhomogeneous layer of arbitrary thickness. Solutions of the wave equation were obtained in terms of Hankel functions with complex arguments. Numerical calculations were made of the reflection coefficient R at the interface of the homogeneous medium. The startling results show that the reflection coefficient for a complex dielectric constant with gradient, can be less than that of the same medium with zero gradient.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-70518 , X-650-73-297
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  • 68
    Publication Date: 2019-06-27
    Description: The space shuttle solid rocket boosters (SRB's) will be jettisoned to impact in the ocean within a 200-mile radius of the launch site. Tests were conducted at Long Beach, California, using a 12-inch diameter Titan 3C model to simulate the full-scale characteristics of the prototype SRB during retrieval operations. The objectives of the towing tests were to investigate and assess the following: (1) a floating and towing characteristics of the SRB; (2) need for plugging the SRB nozzle prior to tow; (3) attach point locations on the SRB; (4) effects of varying the SRB configuration; (5) towing hardware; and (6) difficulty of attaching a tow line to the SRB in the open sea. The model was towed in various sea states using four different types and varying lengths of tow line at various speeds. Three attach point locations were tested. Test data was recorded on magnetic tape for the tow line loads and for model pitch, roll, and yaw characteristics and was reduced by computer to tabular printouts and X-Y plots. Profile and movie photography provided documentary test data.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-69441 , KSC-TR-1253
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  • 69
    Publication Date: 2019-06-27
    Description: Two quiet engine program half scale fans one with a subsonic and the other with a supersonic fan tip speed at takeoff were run with 30 degree leaned and radial outlet guide vanes. Acoustic data at takeoff fan speed on the subsonic tip speed fan showed decreases in 200-foot sideline noise of from 1 to 2 PNdb. The supersonic tip speed fan a takeoff fan speed, however, showed noise increases of up 3 PNdb and a decrease in fan efficiency. At approach fan speed, the subsonic tip speed fan showed a noise decrease of 2.3 PNdb at the 200-foot sideline maximum angle and an increase in efficiency. The supersonic tip speed fan showed noise increase of 3.5 PNdb and no change in efficiency. The decrease in fan efficiency and the nature of the noise increase largely high frequency broadband noise lead to the speculation that an aerodynamic problem occurred.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-134486 , R73AEG176
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  • 70
    Publication Date: 2019-06-27
    Description: Performance characteristics of the LES-6 pulsed plasma thruster over a range of input conditions were investigated by means of a torsion pendulum system. Parameters of particular interest included the impulse bit and time average thrust (and their repeatability), specific impulse, mass ablated per discharge, specific thrust, energy per unit area, efficiency, and variation of performance with ignition command rate. Intermittency of the thruster as affected by input energy and igniter resistance were also investigated. Comparative experimental data correlation with the data presented. The results of these tests indicate that the LES-6 thruster, with some identifiable design improvements, represents an attractive reaction control thruster for attitude contol applications on long-life spacecraft requiring small metered impulse bits for precise pointing control of science instruments.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-135940 , JPL-TM-33-630
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  • 71
    Publication Date: 2019-06-27
    Description: The overall and blade-element performance of a transonic compressor stage with a tip solidity of 1.5 is presented over the stable operating range at rotative speeds from 50 to 100 percent of design speed. State peak efficiency of 0.82 was obtained at a weight flow of 29.4 kg.sec (200.4 (kg/sec)/m2 of annulus area) and a pressure ratio of 1.71. Stall margin at design speed was 14 percent. A comparison of three stages in a solidity study showed that the performance of the 1.5 solidity stage and the 1.3 solidity stage were nearly identical but that the performance of the 1.7 solidity stage was significantly lower.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-2926 , E-7255
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  • 72
    facet.materialart.
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    In:  CASI
    Publication Date: 2019-06-27
    Description: Analyses and design studies were conducted on the technical and economic feasibility of installing the JT8D-109 refan engine on the DC-9 aircraft. Design criteria included minimum change to the airframe to achieve desired acoustic levels. Several acoustic configurations were studied with two selected for detailed investigations. The minimum selected acoustic treatment configuration results in an estimated aircraft weight increase of 608 kg (1,342 lb) and the maximum selected acoustic treatment configuration results in an estimated aircraft weight increase of 809 kg (1,784 lb). The range loss for the minimum and maximum selected acoustic treatment configurations based on long range cruise at 10 668 m (35,000 ft) altitude with a typical payload of 6 804 kg (15,000 lb) amounts to 54 km (86 n. mi.) respectively. Estimated reduction in EPNL's for minimum selected treatment show 8 EPNdB at approach, 12 EPNdB for takeoff with power cutback, 15 EPNdB for takeoff without power cutback and 12 EPNdB for sideline using FAR Part 36. Little difference was estimated in EPNL between minimum and maximum treatments due to reduced performance of maximum treatment. No major technical problems were encountered in the study. The refan concept for the DC-9 appears technically feasible and economically viable at approximately $1,000,000 per airplane. An additional study of the installation of JT3D-9 refan engine on the DC-8-50/61 and DC-8-62/63 aircraft is included. Three levels of acoustic treatment were suggested for DC-8-50/61 and two levels for DC-8-62/63. Results indicate the DC-8 technically can be retrofitted with refan engines for approximately $2,500,000 per airplane.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-121252 , MDC-J5738
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  • 73
    Publication Date: 2019-06-27
    Description: The applicability of small turbofan engines to general aviation aircraft is discussed. The engine and engine/airplane performance, weight, size, and cost interrelationships are examined. The effects of specific engine noise constraints are evaluated. The factors inhibiting the use of turbofan engines in general aviation aircraft are identified.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-114630 , AIRESEARCH-73-210148
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  • 74
    Publication Date: 2019-06-27
    Description: In the absence of direct impingement erosion, electrostatic thruster accelerator grid lifetime is defined by the charge exchange erosion that occurs at peak values of the ion beam current density. In order to maximize the thrust from an engine with a specified grid lifetime, the ion beam current density profile should therefore be as flat as possible. Knauer (1970) has suggested this can be achieved by establishing a radial plasma uniformity within the thruster discharge chamber; his tests with the radial field thruster provide an example of uniform plasma properties within the chamber and a flat ion beam profile occurring together. It is shown that, in particular, the ion density profile within the chamber determines the beam current density profile, and that a uniform ion density profile at the screen grid end of the discharge chamber should lead to a flat beam current density profile.
    Keywords: PROPULSION SYSTEMS
    Type: Journal of Spacecraft and Rockets; 10; Sept
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  • 75
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    In:  CASI
    Publication Date: 2019-06-27
    Description: An on-line spatial light modulator for application as the input transducer for a real-time optical data processing system is described. The use of such a device in the analysis and processing of radar data in real time is reported. An interface from the optical processor to a control digital computer was designed, constructed, and tested. The input transducer, optical system, and computer interface have been operated in real time with real time radar data with the input data returns recorded on the input crystal, processed by the optical system, and the output plane pattern digitized, thresholded, and outputted to a display and storage in the computer memory. The correlation of theoretical and experimental results is discussed.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-124375
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  • 76
    Publication Date: 2019-06-27
    Description: The primary accomplishments have been in the analysis and simulation of receivers and bit synchronizers. It has been discovered that tracking rate effects play, a rather fundamental role in both receiver and synchronizer performance, but that data relating to recorder time-base-error, for the proper characterization of this phenomenon, is in rather short supply. It is possible to obtain operationally useful tape recorder time-base-error data from high signal-to-noise ratio tapes using synchronizers with relatively wideband tracking loops. Low signal-to-noise ratio tapes examined in the same way would not be synchronizable. Additional areas of interest covered are receiver false lock, cycle slipping, and other unusual phenomena, which have been described to some extent in this and earlier reports and simulated during the study.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-132809
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  • 77
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2019-06-27
    Description: An in-depth study of an Earth Storable Bimodal (ESB) Engine using earth storable propellants N2O/N2H4 and operating in either a monopropellant or bipropellant mode was conducted. Detailed studies were completed for both a hot-gas, regeneratively cooled thrust chamber and a ducted hot-gas, film cooled thrust chamber. Hydrazine decomposition products were used for cooling in either configuration. The various arrangements and configurations of hydrazine reactors, secondary injectors, chambers and gimbal methods were considered. The two basic materials selected for the major components were columbium alloys and L-605. The secondary injector types considered were previously demonstrated by JPL and consisted of a liquid-on-gas triplet, a liquid-on-gas doublet, and a liquid-on-gas coaxial injector. Various design tradeoffs were made with different reactor types located at: the secondary injector station, the thrust chamber throat, and the nozzle/extension interface. Associated thermal, structural, and mass analyses were completed.
    Keywords: PROPULSION SYSTEMS
    Type: BELL-8706-933005 , NASA-CR-133617
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  • 78
    Publication Date: 2019-06-27
    Description: In a simplified airplane-mission study for a Mach 2.61 supersonic transport, dry turbojets with and without real suppressors and dry turbojets with ideal rotary flow inductors were studied for sideline noise levels as low as FAR 36-20. Compressor pressure ratio was varied from 5 to 30 and turbine temperature from 1800 to 3000 F. For no noise constraint and without a suppressor, the best dry turbojet gave a payload of 9.0 percent of gross weight and a sideline noise of 126 effective perceived noise decibels. Payload dropped rapidly for lower noise goals, becoming 6.3 percent of gross weight at FAR 36. At FAR 36, the turbojet with suppressor gave a payload of 8.3 percent and the turbojet with ideal rotary flow inductor, 7.3 percent. Below FAR 36, the ideal inductor was far superior to the real suppressor, giving payloads of 6.6 percent at FAR 36-10 and 5.7 percent at FAR 36-20.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-68233 , E-7450
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  • 79
    Publication Date: 2019-06-27
    Description: Flight tests were conducted with two F-111A airplanes to study the effects of steady-state and dynamic pressure phenomena on the propulsion system. Analysis of over 100 engine compressor stalls revealed that the stalls were caused by high levels of instantaneous distortion. In 73 percent of these stalls, the instantaneous circumferential distortion parameter, k sub theta, exhibited a peak just prior to stall higher than any previous peak. The K sub theta parameter was a better indicator of stall than the distortion factor, k sub d, and the maximum-minus-minimum distortion parameter, d, was poor indicator of stall. Inlet duct resonance occurred in both F-111A airplanes and is believed to have been caused by oscillations of the normal shock wave from an internal to an external position. The inlet performance of the two airplanes was similar in terms of pressure recovery, distortion, and turbulence, and there was good agreement between flight and wind-tunnel data up to a Mach number of approximately 1.8.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TN-D-7328 , H-741
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  • 80
    Publication Date: 2019-06-27
    Description: A 5-cm structurally integrated ion thruster has been developed for attitude control and stationkeeping of synchronous satellites. As optimized with a conventional ion extraction system, the system demonstrates a thrust T = 0.47 mlb at a beam voltage of 1600 V, total mass efficiency of 76%, and electrical efficiency of 56%. Under the subject contract effort, no significant performance change was noted for operation with two dimensional electrostatic thrust-vectoring grids. Structural integrity with the vectoring grids was demonstrated for shock (+ or - 30 G), sinusoidal (9 G), and random (19.9 G rms) accelerations. System envelope is 31.2 cm long by 13.4 cm flange bolt circle, with a mass of 9.0 Kg, including 6.8 Kg mercury propellant.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-121183
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  • 81
    Publication Date: 2019-06-27
    Description: Two spoke-type suppressor plug nozzles and a basic plug nozzle were tested for noise and thrust performance. The nozzles were mounted on an underwing nacelle on an F-106B aircraft, and tests were made both statically and in flyovers at Mach 0.4 at an altitude of 91 meters (300 ft). The flight and static data were adjusted to common reference conditions so that direct comparisons could be made. The noise characteristics that these nozzles would have on a large multiengine aircraft at a 640-meter (2100-ft) sideline distance are also presented. Flight noise levels for all three nozzles were higher than static at comparable conditions; and a shift in the frequency spectra was seen from static to flight, indicating the presence of a forward velocity effect on the noise characteristics.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-2856 , E-7186
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  • 82
    Publication Date: 2019-06-27
    Description: Results of a program for sonic inlet technology development are presented. This program includes configuration and mechanical design selection of concepts, aerodynamic design description of the models, and results of test evaluation. Several sonic inlet concepts were tested and compared for aerodynamic and acoustic performance. Results of these comparative evaluations are presented. Near-field measurements were taken inside several of the inlet models. Results of these tests are discussed with respect to the effect of Mach number gradients on noise attenuation and rotor shock wave attenuation, and boundary layer effects on noise propagation. The test facilities and experimental techniques employed are described briefly.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-121126 , D6-40855-VOL-1
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  • 83
    Publication Date: 2019-06-27
    Description: For abstract, see
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-121128 , D6-40818-VOL-3
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  • 84
    Publication Date: 2019-06-27
    Description: For abstract, see
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-121127 , D6-40855-1-VOL-2
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  • 85
    Publication Date: 2019-06-27
    Description: A preflight assessment of the Skylab VHF ranging coverage for the rendezvous portion of the nominal SL-1/SL-3 mission is reported, assuming a 27 July 1973 SL-3 launch. Data are based on a nominal attitude trajectory, which has the Saturn workshop in a solar inertial attitude throughout the rendezvous; the CSM terminal phase initiation maneuver is nominal. An addendum to this report is being prepared, which considers the effects of early and late TPI maneuvers. Curves are presented which show the variation in received power levels on both spacecraft-to-spacecraft links from about 600 n.mi. range to CSM and SWS station keeping. Appropriate threshold levels are shown on these received power curves to indicate zero circuit margins for the ranging function.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-133981 , TRW-20029-H203-R0-00
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  • 86
    Publication Date: 2019-06-27
    Description: A comprehensive and fairly self-contained study of centrally obscured optical transmitting and receiving antennas is presented and is intended for use by the laser radar and communication systems designer. The material is presented in a format which allows the rapid and accurate evaluation of antenna gain. The Fresnel approximation to scalar wave theory is reviewed and the antenna analysis proceeds in terms of the power gain. Conventional range equations may then be used to calculate the power budget. The transmitter calculations, resulting in near and far field antenna gain patterns, assumes the antenna is illuminated by a laser operating in the fundamental cavity mode. A simple equation is derived for matching the incident source distribution to a general antenna configuration for maximum on-axis gain. An interpretation of the resultant gain curves allows a number of auxiliary design curves to be drawn which display the losses in antenna gain due to pointing errors and the cone angle of the outgoing beam as a function of antenna size and central obscuration. The use of telescope defocusing as an approach to spreading the beam for target acquisition is compared to some alternate methods.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-70423 , X-524-73-185
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  • 87
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2019-06-27
    Description: A composite antenna feed subsystem concentrated in a small area at the prime focus of the parabola of a satellite parabolic reflector accomodates a plurality of frequency bands. The arrays comprising the subsystem are mounted on the top cover of a communication module. A multimode horn is arranged at the center of the subsystem axis which functions at X- And C-band frequencies, and a cross array consisting of individual elements form the S-band feed, with one arm of the S-band array containing an element mutually shared with the L-band array. Provision is also made for UHF frequencies, and a dipole arrangement for VHF frequencies is arranged around the S-band arms.
    Keywords: COMMUNICATIONS
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  • 88
    Publication Date: 2019-06-27
    Description: The natural environment design requirements for the solar electric propulsion stage are presented. Environment criteria for the SEP stage will cover earth orbital operations out to geosynchronous altitudes and also interplanetary missions including comet and asteroid missions.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-64761
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  • 89
    Publication Date: 2019-06-27
    Description: Results of experimental tests conducted on a supersonic, mixed compression, axisymmetric inlet are presented. The inlet is designed for operation at Mach 2.5 with a turbofan engine (TF-30). The inlet was terminated with either a choked-orifice plate or a long pipe with variable area choked exit plug. Frequency responses were obtained for selected static pressures in the diffuser. These pressures were selected as potential control signals for terminal shock control. Frequency responses were obtained for the Mach 2 and 2.5 conditions for different terminations. Responses also were obtained with and without cowl bleed. Internal disturbances were produced by sinusoidally varying the inlet overboard bypass doors at frequencies out to 100 hertz.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-2833 , E-7426
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  • 90
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2019-06-27
    Description: Three turbofan configurations, each incorporating alternative noise reduction features, were tested under the Quiet Engine Program. Performance data for these engines are shown over a range of flight conditions. The data are presented in tabular form for standard day flight inlet conditions. Procedures for estimating nonstandard day performance are shown. Tabular data and calculation procedures to allow determination of ram recovery, customer bleed, and customer shaft power extraction effects on engine performance can be found in the original Performance Brochure titled, Experimental Quiet Engine Program, Predicted Engine Performance, dated April 8, 1970. Predicted engine noise levels for representative take-off and approach conditions are provided.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-121258
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  • 91
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2019-06-27
    Description: The equipment, exclusive of thrustors, required to demonstrate the feasibility of a resistojet propulsion system for space station attitude control application using representative simulated crew biowaste propellants and available resistojet thrustors in the ground simulation tests is discussed. The overall objective of the program was to provide a biowaste resistojet prototype propellant management and control system sufficiently similar to the flight article to permit concept feasibility and system demonstration testing of interface compatibility, operational characteristics, and system flexibility.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-132269 , MDC-G4745
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  • 92
    Publication Date: 2019-06-27
    Description: The noise level of an uncoventional propulsion system for the next generation of subsonic, long-range transport aircraft is discussed. The desired noise level may be achieved by: (1) a fixed geometry, high bypass ratio turbofan with a geared two-stage fan and advanced acoustic treatment or (2) a moderate bypass ratio turbofan with a variable pitch two-stage fan, variable primary and duct nozzles, and advanced acoustic treatment. The geared fan system meets the noise goal with minimum economic penalty. Comparison of the noise levels at takeoff and landing in combination with the economic penalties required to achieve the lower noise levels at specific noise measuring stations, indicate that both area reduction and current certification prodedures should be used to ascertain the point of diminishing returns in establishing future noise goals.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-121242 , PWA-4692
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  • 93
    Publication Date: 2019-06-27
    Description: A single grid accelerator system for an ion thrustor is discussed. A layer of dielectric material is interposed between this metal grid and the chamber containing an ionized propellant for protecting the grid against sputtering erosion.
    Keywords: PROPULSION SYSTEMS
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  • 94
    Publication Date: 2019-06-27
    Description: The monopropellant hydrazine resistojet, termed the electrothermal hydrazine thruster (EHT) by TRW systems, thermally decomposes anhydrous hydrazine propellant to produce a high-temperature, low-molecular-weight gas for expulsion through a propulsive nozzle. The EHT developed for this program required about 3-5 watts of electrical power and produced 0.020 to 0.070 pound of thrust over the inlet pressure range of 100 to 400 psia. The thruster was designed for both pulsed and steady state operation. A summary of the GSFC original requirements and GSFC modified requirements, and the performance of the engineering model EHT is given. The experimental program leading to the engineering model EHT design, modifications necessary to achieve the required thruster life capability, and the results of the life test prgram. Other facets of the program, including analyses, preliminary design, specifications, data correlation, and recommendations for a flight model are discussed.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-132784 , TRW-20266-6024-RO-00
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  • 95
    Publication Date: 2019-06-27
    Description: A model of a short takeoff and landing (STOL) fan stage was testedin a single-stage compressor research facility. Surveys of the airflow conditions ahead of the rotor, between the rotor and stator, and behind the stator were made over the stable operating range of the stage. At the design speed of 213.3 meters per second and a weight flow of 31.2 kilograms per second, the stage pressure ratio of 1.15 was less than the design value of 1.2. The stage was tested with the rotor blades reset for more flow. Design pressure ratio was achieved and surpassed with the minus 5 deg and minus 7 deg resets, respectively. The stage efficiency was 0.88 for the minus 5 deg reset and 0.85 for the minus 7 deg reset.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-2837 , E-7434
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  • 96
    Publication Date: 2019-06-27
    Description: Results are presented of analyses conducted to determine why erroneous data were transmitted by 60 of the 1 sample-per-second telemetry channels of Apollo 17 for a 2-minute period beginning at about 191 hours 40 minutes. Reasons for the failure and corrective actions taken are described.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-69367 , JSC-07985
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  • 97
    Publication Date: 2019-06-27
    Description: The design, development, and testing of the NASA-GFSC Position Location and Aircraft Communications Equipment (PLACE) at C band frequency are discussed. The equipment was installed on the USNS Vanguard. The tests involved a sea test to evalute the position-location, 2-way voice, and 2-way data communications capability of PLACE and a trilateration test to position-fix the ATS-5 satellite using the PLACE system.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-66287 , X-752-73-117
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  • 98
    Publication Date: 2019-06-27
    Description: The geometrical theory of diffraction is extended to treat the radiation from apertures or slots in convex, perfectly-conducting surfaces. It is assumed that the tangential electric field in the aperture is known so that an equivalent, infinitesimal source can be defined at each point in the aperture. Surface rays emanate from this source which is a caustic of the ray system. A launching coefficient is introduced to describe the excitation of the surface ray modes. If the field radiated from the surface is desired, the ordinary diffraction coefficients are used to determine the field of the rays shed tangentially from the surface rays. The field of the surface ray modes is not the field on the surface; hence if the mutual coupling between slots is of interest, a second coefficient related to the launching coefficient must be employed. In the region adjacent to the shadow boundary, the component of the field directly radiated from the source is presented by Fock-type functions. In the illuminated region the incident radiation from the source (this does not include the diffracted field components) is treated by geometrical optics. This extension of the geometrical theory of diffraction is applied to calculate the radiation from slots on elliptic cylinders, spheres and spheroids.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-2263
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  • 99
    Publication Date: 2019-06-27
    Description: Theoretical analysis and experimental data are combined to yield the errors to be used with antenna gain, antenna patterns, and RF cable insertion loss measurements for the Mariner Venus-Mercury 1973 Flight Project. These errors apply to measurements conducted at the JPL Mesa, West Antenna Range, on the high gain antenna, low gain antenna, and RF coaxial cables.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-133230 , JPL-TM-33-625
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  • 100
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2019-06-27
    Description: A lightweight small high gain antenna which is capable of being packaged in a collapsed form and automatically expanded when in use is described. The antenna includes a cylindrical housing having a rod with a piston adjacent to one end extending through it. Attached to the outer end of the rod in a normally collapsed state is a helical wire coil. When the gas producing means is activated the piston and rod are shifted outwardly to expand the wire coil. A latch is provided for holding the helical coil in the expanded position.
    Keywords: COMMUNICATIONS
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