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  • Other Sources  (420)
  • STRUCTURAL MECHANICS  (212)
  • COMMUNICATIONS AND RADAR  (208)
  • 1980-1984  (420)
  • 1950-1954
  • 1982  (420)
  • 1950
  • 1
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    Space shuttle solid rocket booster water entry cavity collapse loads (1982)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Solid rocket booster cavity collapse flight measurements included external pressures on the motor case and aft skirt, internal motor case pressures, accelerometers located in the forward skirt, mid-body area, and aft skirt, as well as strain gages located on the skin of the motor case. This flight data yielded applied pressure longitudinal and circumferential distributions which compare well with model test predictions. The internal motor case ullage pressure, which is below atmospheric due to the rapid cooling of the hot internal gas, was more severe (lower) than anticipated due to the ullage gas being hotter than predicted. The structural dynamic response characteristics were as expected. Structural ring and wall damage are detailed and are considered to be attributable to the direct application of cavity collapse pressure combined with the structurally destabilizing, low internal motor case pressure.
    Keywords: STRUCTURAL MECHANICS
    Type: Shock and Vibration Inform. Center The Shock and Vibration Bull., No. 52. Part 2; p 21-26
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  • 2
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    A study of component design loads due to dynamic environment (1982)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The random vibration of the components of the space shuttle causing internal cargo bay acoustic impingement on the payload was investigated. The import factors to be considered in the design of acoustically loaded structures are the prediction of acoustic environment, prediction of structural response to this environment, and to determine the effect of the response on the structural strength requirements. Two basic responses were analyzed. The primary structure response due to random vibration is first analyzed. The output of primary structure response is used as an input to the secondary structure to calculate the component response.
    Keywords: STRUCTURAL MECHANICS
    Type: Alabama Univ. in Huntsville The 1981 NASA(ASEE Summer Fac. Fellowship Program; 12 p
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  • 3
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    A new SPS antenna design to reduce grating lobes (1982)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: In the Solar Power Satellite system, the antenna's misalignment will produce well defined grating lobes. These gratings lobe peaks occur every 440 km and are potentially hazardous to the environment. One way to suppress these peaks is to phase control every power module. The cost due to the increase in receiving electronics and processors, however, could prove to be prohibitive. A new design of the antenna involving the addition of two broad gaps, one along the x axis and another along the y axis is proposed. The gap distance is exactly one half of the distance between the center of two neighboring subarrays. Calculation of far field radiation patterns shows that the design reduces grating lobe peaks without sacrificing power in the main lobe.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The 1981 NASA(ASEE Summer Fac. Fellowship Program; 14 p
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  • 4
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    Surface contour of a biaxially strained, doubly curved antenna reflective mesh (1982)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The elastic membrane equations which describe the deflection of a biaxially tensioned reflective mesh from an idealized surface were developed and solved. The conditions of equilibrium of the forces acting on a membrane element furnish equations which may be used to solve a variety of problems. Configurations considered include continuous, as well as incremental mesh attachment to structural members to form shapes which are approximately parabolic or spherical.
    Keywords: STRUCTURAL MECHANICS
    Type: Alabama Univ. in Huntsville The 1981 NASA(ASEE summer Fac. Fellowship Program; 11 p
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  • 5
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    Miniature voice output communication aid (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA Technol. Appl. Team; p 20
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  • 6
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    Low gain and steerable vehicle antennas for communications with land mobile satellite (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Current development activities at JPL for ground mobile vehicle antennas to be used with the Land Mobile Satellite Service (LMSS) system are described. Both low gain and electronically steerable high gain type antennas are discussed in terms of their design concept and RF performance. For the low gain type, three classes of antennas are under various stages of development. These are the crossed-drooping dipole, quadrifilar helix, and microstrip patch designs. The antennas are intended to provide circularly-polarized radiation with a minimum of 3-dB gain in the angular region from 19 degrees to 60 deg from the horizon in elevation plane and with an omnidirectional pattern in azimuthal plane. For the electronically steerable high gain type, circularly-polarized microstrip patch phased arrays formed on a planar surface and on the surface of a truncated cone are under study. The arrays are intended to provide a minimum of 12 dB gain in the same angular region in elevation plane at all azimuthal angles. This coverage is accomplished by scanning the high gain pencil beam in both elevation and azimuthal directions. Both types of antennas are to transmit at 821-831 MHz band and to receive at 866-876 MHz band. They must be of low cost design and reasonably conformal to the vehicle.
    Keywords: COMMUNICATIONS AND RADAR
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  • 7
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    Concept for advanced satellite communications and required technologies (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The advanced communications technology satellite (ACTS) program of NASA is aimed at the development of high risk technologies that will enable exploiting higher frequency bands and techniques for improving frequency reuse. The technologies under development include multiple beam spacecraft antennas, on-board switching and processing, RF devices and components and advanced earth stations. The program focus is on the Ka-band (30/20 GHz) as the implementing frequency since it has five times the bandwidth of either the C- or Ku-bands. However, the technology being developed is applicable to other frequency bands as well and will support a wide range of future communications systems required by NASA, other Government agencies and the commercial sector. An overview is presented of an operational 30/20 GHz satellite system that may evolve. How the system addresses service requirements is discussed, and the technology required and being developed is considered. Previously announced in STAR as N83-11210
    Keywords: COMMUNICATIONS AND RADAR
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  • 8
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    An advanced generation land mobile satellite system and its critical technologies (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A conceptual design for a Land Mobile Satellite System (LMSS) for the 1990s is presented. LMSS involves small tranceivers accessing satellites directly, with ground reception through small car-top antennas. The satellite would have a large antenna and blanket coverage areas in the UHF. The call may originate from a home, be carried by wire to a gateway, transmitted to satellite on the S-band, converted to UHF on the satellite, and transmitted to the vehicle. The system design is constrained by the number of users in an area during the busiest hours, Shuttle storage, controllability factors, and the total area served. A 55-m antenna has been selected, with 87 spot beams and two 10 MHz UHF bands in the 806-890 MHz band. A 17 dB interbeam isolation level is required, implying that sufficient sub-bands can be generated to assure 8265 total channels. The mobile satellite (MSAT) would have an 83 m mast lower segment, a 34 m upper segment, and a second, 10 m antenna made of a deployable mesh. Various antenna function modes are considered.
    Keywords: COMMUNICATIONS AND RADAR
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  • 9
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    TDM/FM/FDMA - A modulation technique for multiple-beam satellites which precludes cochannel interference and allows non-uniform geographic distribution of user channels (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The technique outlined in this paper is intended to eliminate the problems of cochannel interference and uniform geographic distribution of user channels which arise in conventional designs for a multiple spot beam communication satellite to serve mobile telephony users across the CONUS. By time multiplexing FM/FDMA signal ensembles so that only those beams operating on distinct frequency subbands are allowed to transmit concurrently, cochannel interference arising from simultaneous frequency subband reuse is precluded. Thus, time disjoint frequency reuse is accomplished over a repetitive sequence of fixed time slots. By assigning different size subbands to each time slot, a market of nonuniform users can be accommodated. The technique results in a greatly simplified antenna feed system design for the satellite, at a cost of imposing the need for time slot synchronization on the mobile FM receivers whose ability for rejecting adjacent channel interference is somewhat diminished.
    Keywords: COMMUNICATIONS AND RADAR
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  • 10
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    Determination of normal modes from measured complex modes (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A technique is presented for computing a set of normal modes from a set of measured complex modes. The number of elements in the modal vectors, which is equal to the number of measurements, can be larger than the number of modes under consideration. It is also shown that the practice of normal mode approximation to complex modes can lead to very large errors when the modes are too complex. A numerical example and a simulated experiment illustrate the concepts discussed and support the theory presented.
    Keywords: STRUCTURAL MECHANICS
    Type: Shock and Vibration Inform. Center The Shock and Vibration Bull., No. 52. Part 5; p 13-17
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  • 11
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    Required developments in structural dynamics (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The finite element method, modal component synthesis, and the use of fast Fourier transformation were key developments in structural dynamics in the past 15 to 20 years. Current areas requiring additional effort include: (1) the correct calculation of modal shape and natural frequencies for complex structures; (2) the correlation of math models with test data; (3) the establishment of a criteria for "goodness" of the correlation between analysis and test; (4) the selection of the correct displacement functions when using computer programs for modal synthesis; (5) accuracy of response calculations; and (6) the inverse problem of determining the force problem from the response data. Trends identified include the use of distributed computing, greater reliance on analysis, and the possible use of artificial intelligence techniques, or some way of feeding back information, to provide solution guidance to engineers.
    Keywords: STRUCTURAL MECHANICS
    Type: Shock and Vibration Inform. Center The Shock and Vibration Bull., No. 52. Part 1; p 49-54
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  • 12
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    Space Shuttle and TDRSS telecommunications system interfaces (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The telecommunications system interfaces between the spacecraft and the space shuttle, and between the spacecraft and the Tracking and Data Relay Satellite System (TDRSS) are discussed. The payload/shuttle/ground communications network, principle end-to-end link configurations, and requirements for attached and detached payloads are addressed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telecommun. Systems Eng.; p 557-596
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  • 13
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    Telecommunications performance analysis and monitoring software (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The computer software used for telecommunications performance analysis and monitoring is discussed. The utilization of the TPAP analysis program for the Viking 1975 project and the Voyager 1977 project is described. The functional and design requirements for the successor system, TPAS, are also given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telecommun. Systems Eng.; p 491-516
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  • 14
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    Radio frequency selection and interference prevention (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The bands available for deep-space communications, and the choice of particular mission frequencies are discussed. The more general susceptibility of deep-space Earth stations to various kinds of interference is then presented. An associated topic is the development of protection criteria that specify maximum allowable levels of interference. Next, the prediction of interference from near-Earth satellites is described, with particular emphasis on the problems and uncertainties of such predictions. Finally, a brief description of other activities aimed at the prevention or avoidance of interference to deep-space radio communications is given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telecommun. Systems Eng.; p 517-555
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  • 15
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    Spacecraft antennas (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A tutorial description is given for spacecraft antennas used for deep-space-to-Earth communication. Radiation pattern parameters, pointing errors, pointing and polarization loss, and noise characteristics are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telecommun. Systems Eng.; p 413-460
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  • 16
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    Spacecraft radio frequency subsystem (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The historical background for the development of the planetary (RFS) is reviewed, and the performance capabilities of the various functional subassemblies are described. The flight radio frequency subsystem is a valid component for the three spacecraft telecommunications functions of tracking, command, and telemetry. It is the radio and the signal processing equipment residing in the spacecraft that interfaces with the control & data subsystem and performs two-way communications with the Earth-based Deep Space Network. The RFS consists of all the elements for RF reception, demodulation, modulation, and transmission, including those for command detection and telemetry modulation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telecommun. Systems Eng.; p 383-412
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  • 17
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    Command system (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Multimission Command (MMC) System is described. The major components within the MMC System are discussed, with the emphasis on the telecommunication-related implementations. Two versions of the spacecraft command detection system (the Viking heritage command detector and the NASA standard command detector) are discussed in detail. The former prevails in the existing flight projects and the latter will likely be adopted by the missions of the near future. The preparation of design control tables for the control of command link performance between deep space stations and the spacecraft is also discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telecommun. Systems Eng.; p 343-381
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  • 18
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    Receiver design and performance characteristics (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The basic design, principles of operation, and characteristics of deep space communications receivers are examined. In particular, the basic fundamentals of phase-locked loop and Costas loop receivers used for synchronization, tracking, and demodulation of phase-coherent signals in residual carrier and suppressed carrier systems are addressed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telcommun. Systems Eng.; p 49-121
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  • 19
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    Special characteristics of digital modulations (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The importance of the bandwidth required for transmitting the chosen signaling or modulation technique in evaluating efficiency of a communication system is noted. The direct relation between bandwidth and the power spectral density (PSD) of the signaling scheme makes efficient analytical methods for calculating the PSD essential to specifying the spectral occupancy of the transmission channel. Several techniques for calculating the PSD of synchronous data pulse streams are reviewed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telecommun. Systems Eng.; p 23-47
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  • 20
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    Telecommunications systems design (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The general configuration of deep space telecommunication systems is reviewed with regard to the design criteria necessary to insure the integrity of the system's telemetry, command, and tracking functions. The signal to noise spectral density ratios that characterize telecommunications performance are defined in terms of the link parameters. For design control, a statistical approach to predict link performance and to assess its uncertainty is described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telecommun. Systems Eng.; p 1-22
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  • 21
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    The usage of substructuring analyses in the Get Away Special (GAS) program (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The use of automatic multi-stage substructing analysis is demonstrated for a hypothetical case of a GAS container supported by structural channels with a simulated experimental package inside the container. The GAS program purpose is stated and potential candidate structures to support experimental packages are discussed. The GAS container model and the substructuring analysis capabilities of NASTRAN make it possible to study the experiments inside the container as well as the design constraints resulting from the support structures holding the containers. The use of substructuring in the GAS program could be an important factor in increasing the number of flight opportunities.
    Keywords: STRUCTURAL MECHANICS
    Type: Georgia Univ. 10th NASTRAN User's Colloq.; p 204-215
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  • 22
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    Adaptive arrays - A new approach to the steady-state analysis (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A closed-form expression for the steady-state output signal-to-noise ratio (SNR) of an n-element adaptive array excited by one desired narrow-band signal and K - 1 narrow-band jammers is obtained. This is facilitated by representing each excitation by a complex n-dimensional vector - the excitation vector. It is shown that the important system parameters are functions of scalar products of pairs of these excitation vectors. In particular, the normalized output SNR of the array is shown to be the ratio of determinants whose elements involve these scaler products. Such determinants are also shown to be involved in the expressions for the optimal array weights.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-30; Jan. 198
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  • 23
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    A mixed formulation finite element for linear thin shell analysis (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An eight node curved thin shell slement was tested. The element is based on the degenerate solid concept and the mixed formulation with the independent inplane and transverse shear strains. The number of unknown parameters in the assumed strains is chosen to alleviate the spurious constaining or locking effect. It is indicated that for a pinched cylindrical shell with diaphragmed ends and fixed ends the present element shows good performance.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Struct. and Solid Mech., 1982; p 219-228
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  • 24
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    Application of a boundary element method to the study of dynamical torsion of beams (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: During dynamic torsion of beam elements, consideration of nonuniform warping effects involves a more general technical formulation then that of Saint-Venant. Nonclassical torsion constants appear in addition to the well known torsional rigidity. The adaptation of the boundary integral element method to the calculation of these constants for general section shapes is described. The suitability of the formulation is investigated with some examples of thick as well as thin walled cross sections.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Struct. and Solid Mech., 1982; p 129-139
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  • 25
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    Application of the reduced basis method to nonlinear transient thermal analysis (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An effort to apply the reduced basis method to nonlinear transient thermal analysis is described. The method combines the classical Rayleigh-Ritz and modal superposition techniques with contemporary finite element methods to retain modeling versatility as the degrees of freedom in a problem are reduced. The essence of the method is to use a few thermal modes from eigenvalue analyses as basis vectors to represent the temperature response for a given thermal problem similar to the use of vibration modes to represent displacements in a dynamic response problem. Approximate temperature distributions were obtained using the reduced basis method for a small section of the Shuttle Orbiter lower wing undergoing reentry heating. Good agreement was obtained between the reduced basis method solutions and full system solutions with reductions in the degrees of freedom of up to a factor of four. The good agreement indicates the reduced basis method has the potential for significant reduction in computing effort for thermal analysis; however, considerable work remains to determine techniques for selecting the type and number of basis vectors needed for approximate solutions to more complex transient thermal problems.
    Keywords: STRUCTURAL MECHANICS
    Type: Res. in Struct. and Solid Mech., 1982; p 49-65
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  • 26
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    New CCIR papers on telecommunications for deep space research (1982)
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    Publication Date: 2011-08-18
    Description: The selection of preferred frequency bands for deep space telecommunications in the 20 to 120 GHz range is discussed. The performance of links between Earth stations and stations in deep space is affected by the atmosphere of the Earth. Attenuation and emission by the atmosphere generally limits deep space telecommunications to frequencies below 20 GHz. There are, however, certain frequency bands in the 20 to 120 GHz range where atmospheric attenuation is low enough to permit links between Earth stations and deep space stations. Additionally there are certain other bands in the 20 to 120 GHz range that would be particularly suitable for links between an Earth orbiting relay station and deep space stations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 86-102
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  • 27
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    An experimental investigation of the changes of VLBI time delays due to antenna structural deformations (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Structural deformations primarily occur as functions of antenna elevation angle due to gravity loading. For a Cassegrain antenna, one of the major effects of structural deformation on measured VLBI time delays are those delay changes associated with axial subreflector displacement from its nominal position. Two types of time delay changes that occur when the subreflector is axially defocused are: a change which is a linear function of subreflector defocus position; and a cyclical change caused by multipath. Test results show that for the 64-m DSN antenna, the linear change is 1.8 times the subreflector defocus position, while the peak-to-peak change in cyclical variation is about + or - 3 cm when a spanned bandwidth of 38 MHz at 2290 MHz is used.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 8-16
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  • 28
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    Sideband-aided receiver arraying (1982)
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    Publication Date: 2011-08-18
    Description: Efforts to increase the amount of data that can be received from outer planet missions by coherently combining signals from ground antennas in such a way as to increase the total effective aperture of the receiving system are discussed. As these signals become weaker, the baseband arraying technique in current use degrades somewhat due to carrier jitter. One solution to this problem is Sideband-Aided Receiver Arraying (SARA). In SARA, sidebands demodulated to baseband in a master receiver at the largest antenna are used to allow slave receivers in the other antennas to track the sideband power in the signal rather than the carrier power. The already existing receivers can be used in the slaves to track and demodulate the signals in either a residual carrier or a suppressed carrier environment. The resultant baseband signals from all the antennas can then be combined using existing baseband combining equiment. Computer simulations of SARA show increases in throughput (measured in data bits per second) over baseband-only combining 17 percent at Voyager 2 Uranum encounter and 31 percent at Neptune for a four-element antenna array and (7, 1/2) convolutional coding.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 39-54
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  • 29
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    The DSN radio science system Mark 3, 1980 (1982)
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    Publication Date: 2011-08-18
    Description: The DSN Radio Science System supported the Voyager 2 Saturn encounter radio science experiments in August 1981. Support for these experiments was provided by all the Deep Space Stations of the DSN. However, the critical support for the Saturn occultation and ring scattering experiment was provided at DSS 43 by the medium-band open-loop recording system. The DSN Radio Science System is descried and the recent implementation at DSS 43 is emphasized.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 6-11
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  • 30
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    Selection of frequencies for deep-space telecommunications (1982)
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    Publication Date: 2011-08-18
    Description: The procedures used by the Jet Propulsion Laboratory to select and recommend frequencies to be used for deep space telecommunications are explained. The frequency selection process described deals only with the potential for radio frequency interference between deep space telecommunication links. Channel plans based on bandwidth, hardware implementation, and frequency ratio considered are used. The channel selection process is based on calculations and analysis of interference-to-signal power ratios as a function of time for each possible pair of missions. The modes of interference and the interference protection ratio are explained, and the interference analysis procedure described. Equations used in calculating the downlink and uplink interference analyses are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 49-61
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  • 31
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    Signalling characteristics in satellite-aided land mobile communications (1982)
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    Publication Date: 2011-08-18
    Description: The feasibility of land mobile radio communications has been demonstrated by a large number of experiments with NASA's ATS satellites. Significant differences in the propagation characteristics of satellite and terrestrial mobile signal paths were observed in the experiments. Terrestrial paths are best in cities where they can provide frequency reuse and assure communication by bouncing signals around obstructions. Satellites may be best in thinly populated areas because they eliminate the need for many tower mounted relays. The satellite paths do not have the severe Rayleigh fading that limits the range and signal quality of terrestrial paths if the satellite is above approximately ten degrees elevation, a value easily achieved for the United States. The experiments verified that high quality voice communications and other functions, such as data transmission and vehicle position surveillance, are easily accomplished through geostationary satellites with vehicle transmitter power and antenna gain no different than those of terrestrial mobile communications.
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  • 32
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    Approximate analysis of postbuckled through-width delaminations (1982)
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    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N81-27202)
    Keywords: STRUCTURAL MECHANICS
    Type: Composites Technology Review; 4; Fall 198
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    Prediction of transonic flutter for a supercritical wing by modified strip analysis (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: (Previously cited in issue 12, p. 2022, Accession no. A81-29471)
    Keywords: STRUCTURAL MECHANICS
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    Observations of tropospheric phase scintillations at 5 GHz on vertical paths (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The article presents observations of turbulence-induced tropospheric phase fluctuations measured at 5 GHz on the near-vertical paths relevant to many astronomical and geophysical measurements. The data are summarized as phase power spectra, structure functions, and Allan variances. Comparisons to other microwave observations indicate relatively good agreement in both the level and shape of the power spectrum of these tropospheric phase fluctuations. Implications for precision Doppler tracking of spacecraft and geodesy/radio interferometry are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 17; Nov
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  • 35
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    Evaluation and reduction of errors induced by the Guyan transformation (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Guyan reduction refers to a method used to reduce the number of degrees of freedom in a structural model for dynamic analysis. Experience shows that, if the method is properly employed, then this reduction method does in fact provide a "reasonably" accurate approximation of the dynamic characteristics of the unreduced model. A method that provides an accurate estimate of the error in each mode of the reduced eigenvalue problem and, in addition, gives first order correction terms that greatly improve the accuracy of the eigenvectors and eigenvalues is presented. The method is demonstrated by standard COSMIC NASTRAN DAMP alters to rigid format 3, real normal mode analysis. Comparative computer time of modal extraction versus error analysis is discussed for the VAX-11/780 version of COSMIC NASTRAN.
    Keywords: STRUCTURAL MECHANICS
    Type: 10th NASTRAN User's Colloq.; p 233-248
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    Improving a NASTRAN dynamic model with test data using LINWOOD (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The concept of expressing test modes as a linear combination of analytical modes was applied to the prediction of corrective terms in math model mass and stiffness. Test data for the Space Shuttle quarter scale solid rocket booster were analyzed by this method and significant improvements in frequency and mode shap correlation are noted. The applicability of the method is demonstrated.
    Keywords: STRUCTURAL MECHANICS
    Type: Georgia Univ. 10th NASTRAN User's Colloq.; p 74-86
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    Solution of axisymmetric fluid structure interaction problems with NASTRAN (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The solution of axisymmetric acoustic fluid structure interaction problems, employing the NASTRAN computer program is presented. A previously developed 3-D Cartesian Coordinates pressure element formulation is adapted especially for axisymmetric elements. Analogous to the 3-D Cartesian Coordinate predecessor, the fluid portion of the problem is modeled with finite elements wherein one of the displacement components serves as a dummy variable for the pressure unknowns. Two alternatives for implementation of the analogy are presented: (1) an approximate method by which dummy values of G, and nu are used to approximately invoke the analogy wherein the accuracy of the approximation is made as close as desired to the proper analogy within an arbitrary small parameter epsiton; (2) an exact method whereby the NASTRAN FORTRAN coding is slightly changed to invoke the analogy exactly. Comparison of the finite element solution to the exact solution to the same problem is given.
    Keywords: STRUCTURAL MECHANICS
    Type: Georgia Univ. 10th NASTRAN User's Colloq.; p 87-111
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  • 38
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    Recent developments of NASTRAN pre- amd post-processors: Response spectrum analysis (RESPAN) and interactive graphics (GIFTS) (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Two specific NASTRAN preprocessors and postprocessors are examined. A postprocessor for dynamic analysis and a graphical interactive package for model generation and review of resuls are presented. A computer program that provides response spectrum analysis capability based on data from NASTRAN finite element model is described and the GIFTS system, a graphic processor to augment NASTRAN is introduced.
    Keywords: STRUCTURAL MECHANICS
    Type: 10th NASTRAN User's Colloq.; p 19-44
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  • 39
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    Recent improvements and enhancements to NASTRAN (1982)
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    Publication Date: 2011-08-18
    Description: Several improvements and enhancements recently made to NASTRAN are described. Some of the more important features are: streamlined rigid formats; improved rigid formats; changes related to plotting; checking of required PARAM bulk data cards; checkpoint/restart capability; unsorted and sorted bulk data deck echo; automatic output of the DMAP source listing; elimination of link switching caused by use of utility modules; paging the NASTRAN output; processing of mixed record data blocks by INPUT2/OUTPUT2 modules; module execute flag included in the OSCAR listing; and use of the multiple XDMAP cards in the DMAP. It is concluded that these changes increase the usefulness of the program.
    Keywords: STRUCTURAL MECHANICS
    Type: Georgia Univ. 10th NASTRAN User's Colloq.; p 12-17
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  • 40
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    Ultrasonic measurement of axial stress (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The theory of acoustic propagation in strained media is examined, with particular emphasis on rod (bolt) geometries. The continuous wave (CW) approach is the basis of the study, and the theory is developed from a frequency domain analysis standpoint in order to obtain an applied stress/normalized frequency shift relationship. CW measurements may be influenced by such factors as propagation effects, mode conversion, frequency, material properties, and geometry. After the first loading cycle, axial stress measurements for a preloading with an initial frequency of 4.995 36 MHz dropped to 4.989 19 MHz, indicating a 6.17 kHz change. CW and pseudo-CW ultrasonic techniques are found to be reliable for axial stress measurements, and acoustic attenuation measurements correlated to residual stress fields may possibly involve transducer phase cancellation. It is thus concluded that signal drop is an artifact of the transducer directivity, rather than an actual acoustic power decrease.
    Keywords: STRUCTURAL MECHANICS
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  • 41
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    Extended range stress intensity factor expressions for chevron-notched short bar and short rod fracture toughness specimens (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Fracture; 19; July 198
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  • 42
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    Crack displacements for J/I/ testing with compact specimens (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The suggestion is made that the standard compact specimen (with opening displacement measured at the crack mouth) may be entirely suitable for J-integral determinations if a very simple conversion factor is used. Experimental determination of J-integral values requires the measurement of displacements at the points of load application. For the compact specimen this is a difficult task. On the basis of studies reported by Newman (1979) and Fisher and Buzzard (1980), it is suggested that for any J-based test the standard compact specimen can be used. A very good approximation to the load point displacement (within 3.4 percent) can be obtained by measuring the crack mouth displacement and multiplying by 0.773.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Fracture; 19; July 198
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  • 43
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    An explanation for the systematic flow of plasma in the solar transition region (1982)
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    Publication Date: 2011-08-18
    Description: Using numerical simulations, it is shown that the systematic flow of plasma along a coronal magnetic flux tube is easily produced by a change in the spatial dependence of the heating rate from a symmetric deposition which supports a stationary equilibrium to a time-independent asymmetric deposition. The velocity of the flow is roughly proportional to the heating symmetry and is directed to the side of the loop away from the bulk of the energy deposition.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Astrophysical Journal; vol. 258
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  • 44
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    On restarts in NASTRAN (1982)
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    Publication Date: 2011-08-18
    Description: The checkpoint/restart capability available in NASTRAN is very sophisticated. Improvements and enhancements to this capability made with a view to increasing its efficiency and usefulness are considered. Some important features resulting from these changes are discussed. In particular, the different types of restarts available in NASTRAN are described and how they are handled both in the rigid format and DMAP environments explained. The output to restart runs are also illustrated.
    Keywords: STRUCTURAL MECHANICS
    Type: Georgia Univ. 10th NASTRAN User's Colloq.; p 249-267
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  • 45
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    NASTRAN of the HEP (1982)
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    Publication Date: 2011-08-18
    Description: Preliminary plans for the conversion of NASTRAN to DENELCOR's heterogeneous element processor (HEP) are presented. First, a brief history of computer architecture and the architecture of the HEP computer system are discussed. Second, a description of the HEP computer system is provided. Lastly, the preliminary NASTRAN conversion plans for link management, I/O management, memory management, and code optimization are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: Georgia Univ. 10th NASTRAN User's Colloq.; p 187-203
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  • 46
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    A new capability for elastic aircraft airloads via NASTRAN (1982)
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    Publication Date: 2011-08-18
    Description: A new direct matrix abstract program for NASTRAN written to calculate internal stresses and airloads for a flexible wing is described. The difficulties encountered in interfacing the doublet lattice solution to the aerodynamic problem to the finite element solution to the structural problem are discussed. A brief numerical example is included.
    Keywords: STRUCTURAL MECHANICS
    Type: Georgia Univ. 10th NASTRAN User's Colloq.; p 165-186
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  • 47
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    Finite element solution of torsion and other 2-D Poisson equations (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The NASTRAN structural analysis computer program may be used, without modification, to solve two dimensional Poisson equations such as arise in the classical Saint Venant torsion problem. The nonhomogeneous term (the right-hand side) in the Poisson equation can be handled conveniently by specifying a gravitational load in a "structural" analysis. The use of an analogy between the equations of elasticity and those of classical mathematical physics is summarized in detail.
    Keywords: STRUCTURAL MECHANICS
    Type: Georgia Univ. 10th NASTRAN User's Colloq.; p 153-164
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  • 48
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    Environmentally induced discharges on satellites (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A discharge process whose trigger conditions are a negative exposed metallic surface surrounded by a less negative dielectric, and a large voltage gradient at a dielectric/metal interface is proposed. Analysis of SCATHA data for a discharge substantiates the postulation. Surface discharges cause a small transient charge transfer to space which results in voltage transients. A method of computing these transients, based on the charge lost through the capacitance to space and a fraction of charge stored in the dielectric at the discharge source was developed. It gives an estimate of the discharge transients at the discharge site, which is used as input for coupling code analysis of structure/system response. The transient computations were applied to a three-axis stabilized, geosynchronous satellite for both sunlight and eclipse charging. The energy of the transient pulses are about 1 mJ for sunlight discharge and 8 mJ for eclipse. Changing of selected coatings on the satellite would relieve the stress.
    Keywords: COMMUNICATIONS AND RADAR
    Type: ESA 2nd ESTEC Spacecraft Electromag. Compatibility Seminar; p 161-172
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    Large displacements and stability analysis of nonlinear propeller structures (1982)
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    Publication Date: 2011-08-18
    Description: The use of linear rigid formats in COSMIC NASTRAN without DMAP procedures for the analysis of nonlinear propeller structures is described. Approaches for updating geometry and applying follower forces for incremental loading are demonstrated. The COSMIC NASTRAN rigid formats and other independent finite element programs are compared. The comparisons include results from the four approaches for updating the geometry using RIGID FORMAT 1, RIGID FORMATS 4 and 13, MARC and MSC/NASTRAN. It is shown that user friendly updating approaches can be used to predict the large displacements and instability of these nonlinear structures. The approaches are easily implemented by the user and predict conservative results.
    Keywords: STRUCTURAL MECHANICS
    Type: Georgia Univ. 10th NASTRAN User's Colloq.; p 112-132
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    An interactive review system for NASTRAN (1982)
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    Publication Date: 2011-08-18
    Description: An interactive review system that addresses the problems of model display, model error checking, and postprocessing is described. The menu driven system consists of four programs whose advantages and limitations are detailed. The interface between NASTRAN and MOVIE-BYU, the modifications required to make MOVIE usable in a finite element context, and the resulting capabilities of MOVIE as a graphics postprocessor for NASTRAN are illustrated.
    Keywords: STRUCTURAL MECHANICS
    Type: Georgia Univ. 10th NASTRAN User's Colloq.; p 45-64
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  • 51
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    Input impedance of microstrip antennas (1982)
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    Publication Date: 2011-08-18
    Description: Using Richmond's reaction integral equation, an expression is derived for the input impedance of microstrip patch antennas excited by either a microstrip line or a coaxial probe. The effects of the finite substrate thickness, a dielectric protective cover, and associated surface waves are properly included by the use of the exact dyadic Green's function. Using the present formulation the input impedance of a rectangular microstrip antenna is determined and compared with experimental and earlier calculated results.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-30; July 198
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    Far-field radiation patterns of Y and T shaped arrays with Chebyshev loading (1982)
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    Publication Date: 2011-08-18
    Description: The far-field radiation patterns for Chebyshev loaded Y- and T-shaped array antennas are given for a number of cases. Included are full- and half-length loaded array arms. The goal of the investigation is to determine the effect of different Chebyshev loading arrangements on this type of array. It is found that in both the Y- and T-shaped arrays, the main lobes are defined by the shape of the array and that the level of the side-lobes is mainly dependent on the Chebyshev loading (that is, complete or partial).
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-30; July 198
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    Scattering by Pruppacher-Pitter raindrops at 30 GHz (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N81-30327)
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 17; July-Aug
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    Reliability of the finite element method for calculating free edge stresses in composite laminates (1982)
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    Publication Date: 2011-08-18
    Description: The interlaminar normal stress distributions along the interface between the +45 deg and -45 deg plies of a graphite/epoxy laminate, obtained by various investigators, were found to disagree in both magnitude and sign. The reliability of the displacement-formulated finite element method in analyzing the edge-stress problem of a composite laminate is investigated. The history of the edge-stress problem is reviewed, and two well-known elasticity problems, one involving a stress discontinuity and one a singularity, are analyzed. The finite element analysis in these problems yields accurate stress distributions everywhere except in two elements closest to the stress discontinuity or singularity. Stress distributions for a + or -45 deg ply laminate near the singularity were similar to those of the two elasticity problems, demonstrating the methods, accuracy for calculating interlaminar stresses in composite laminates. The disagreement between the numerical methods was attributed to the unsymmetric stress tensor at singularity.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures; 15; 1, 19; 1982
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    Microwave noise temperature and attenuation of clouds - Statistics of these effects at various sites in the United States, Alaska, and Hawaii (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The microwave attenuation and noise temperature effects of clouds can result in serious degradation of telecommunications link performance, especially for low-noise systems presently used in deep-space communications. Although cloud effects are generally less than rain effects, the frequent presence of clouds will cause some amount of link degradation a large portion of the time. This paper presents a general review of cloud types and their water particle densities, attenuation and noise temperature calculations, and basic link signal-to-noise ratio calculations. Tabular results of calculations for 12 different cloud models are presented for frequencies in the range 10-50 GHz. Curves of average-year attenuation and noise temperature statistics at frequencies ranging from 10 to 90 GHz, calculated from actual surface and radiosonde observations, are given for 15 climatologically distinct regions in the contiguous United States, Alaska, and Hawaii. Nonuniform sky cover is considered in these calculations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 17; Nov
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    Special activity utilization of GDSCC antennas during 1981 (1982)
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    Publication Date: 2011-08-18
    Description: The activities are categorized as advanced systems program, radio astronomy program, crustal dynamics program, and operations and support activities. The goals of each of the activities that received tracking support at Goldstone during 1981 are discussed. All Goldstone stations (DSSs 11, 12, 13 and 14) provided a total of 2353.55 hours of support to special activities during the period.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 121-126
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    Noise temperature and noise figure concepts: DC to light (1982)
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    Publication Date: 2011-08-18
    Description: The Deep Space Network is investigating the use of higher operational frequencies for improved performance. Noise temperature and noise figure concepts are used to describe the noise performance of these receiving systems. It is proposed to modify present noise temperature definitions for linear amplifiers so they will be valid over the range (hf/kT) 1 (hf/kT). This is important for systems operating at high frequencies and low noise temperatures, or systems requiring very accurate calibrations. The suggested definitions are such that for an ideal amplifier, T sub e = (hg/k) = T sub q and F = 1. These definitions revert to the present definition for (hf/kT) 1. Noise temperature calibrations are illustrated with a detailed example. These concepts are applied to system signal-to-noise analysis. The fundamental limit to a receiving system sensitivity is determined by the thermal noise of the source and the quantum noise limit of the receiver. The sensitivity of a receiving system consisting of an ideal linear amplifier with a 2.7 K source, degrades significantly at higher frequencies.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 100-111
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    Provision of 9.6-kbps wideband data rate capability in the DSN (1982)
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    Publication Date: 2011-08-18
    Description: The new 9.6-kbps wideband data rate capability in the DSN is reviewed. A functional description of the completed implementation is presented, together with a plan to upgrade the central communications terminal for additional 9.6 s operational flexibility.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 189-193
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    Solution of Von Karman's plate equation with perturbation and series summation (1982)
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    Publication Date: 2011-08-18
    Description: A nonliner series summation technique was combined with Chien's small parameter perturbation technique to solve the problem of the finite deflection of a simply supported circular plate subjected to a uniform transverse load. Problems involving finite deflections of plates with simply supported or free edges were regarded as almost intractable. The great advantage of incorporating the summation method into the solution procedure is demonstrated.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Centre Res. in Struct. and Solid Mech., 1982; p 349-361
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    Susceptibility of symmetric structures to nonlinear torsional coupling (1982)
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    Publication Date: 2011-08-18
    Description: The susceptibility to induced torsional response of symmetric building structures with nonliner resisting elements was investigated. Stability curves show the effect of the arrangement of the load resisting elements on induced torsional coupling in these nonliner but other wise symmetric structures. Universal upper and lower bound instability curves are also derived; these identify the susceptibility to torsional coupling of symmetric structures with different stiffness arrangements but which have equal mass and total lateral stiffness, and which are intended to model alternative structural strategies for lateral load resistance.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Struct. and Solid Mech., 1982; p 313-328
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    Synthesis of frameworks under multilevel performance constraints (1982)
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    Publication Date: 2011-08-18
    Description: A method for the minimum weight design of practical planar frameworks under both service and ultimate loading conditions is presented. Acceptable elastic stresses and displacements are ensured at the service load level while, simultaneously, adequate safety against plastic collapse is ensured at the ultimate load level. The features of the design method for an industrial steel mill building are illustrated.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Struct. and Solid Mech., 1982; p 285-299
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    RFI measurement survey at Goldstone in November and December 1981 (1982)
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    Publication Date: 2011-08-18
    Description: A measurement survey was conducted to measure the emissions from the transmitters at Deep Space Station 14 and the Spaceflight Tracking and Data Network station. Both intended and spurious emissions were measured from DSN operational transmitters. The quiescent electromagnetic environment was also measured.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 110-121
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    An efficient sampling technique for sums of bandpass functions (1982)
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    Publication Date: 2011-08-18
    Description: A well known sampling theorem states that a bandlimited function can be completely determined by its values at a uniformly placed set of points whose density is at least twice the highest frequency component of the function (Nyquist rate). A less familiar but important sampling theorem states that a bandlimited narrowband function can be completely determined by its values at a properly chosen, nonuniformly placed set of points whose density is at least twice the passband width. This allows for efficient digital demodulation of narrowband signals, which are common in sonar, radar and radio interferometry, without the side effect of signal group delay from an analog demodulator. This theorem was extended by developing a technique which allows a finite sum of bandlimited narrowband functions to be determined by its values at a properly chosen, nonuniformly placed set of points whose density can be made arbitrarily close to the sum of the passband widths.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 3-7
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    An exact zooming method for finite element analyses (1982)
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    Publication Date: 2011-08-18
    Description: An exact zooming technique which employs static condensation and exact structural reanalysis methods was developed. Successive application of static condensation reduces the system to one that is only associated with the degrees of freedom (dof) of the original model. Application of an exact static reanalysis technique permits the displacements at the dof of the original model that are contained in the zoomed portion of the structure to be obtained first. The response external to the zoom, as well as the response of additional dof within various levels of zooming, is computed. With the triangular factor of the stiffness matrix of the original system available, this approach involves only the solution of a system of equations of small order.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Struct. Solid Mech., 1982; p 229-249
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    An emulator for minimizing finite element analysis implementation resources (1982)
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    Publication Date: 2011-08-18
    Description: A finite element analysis emulator providing a basis for efficiently establishing an optimum computer implementation strategy when many calculations are involved is described. The SCOPE emulator determines computer resources required as a function of the structural model, structural load-deflection equation characteristics, the storage allocation plan, and computer hardware capabilities. Thereby, it provides data for trading analysis implementation options to arrive at a best strategy. The models contained in SCOPE lead to micro-operation computer counts of each finite element operation as well as overall computer resource cost estimates. Application of SCOPE to the Memphis-Arkansas bridge analysis provides measures of the accuracy of resource assessments. Data indicate that predictions are within 17.3 percent for calculation times and within 3.2 percent for peripheral storage resources for the ELAS code.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Struct. and Solid Mech., 1982; p 185-199
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    Interaction of heat production, strain rate and stress power in a plastically deforming body under tensile test (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: At high strain rates the heat produced by plastic deformation can give rise to a rate dependent response even if the material has rate independent constitutive equations. This effect has to be evaluated when interpreting a material test, or else it could erroneously be ascribed to viscosity. A general thermodynamic theory of tensile testing of elastic-plastic materials is given in this paper; it is valid for large strain at finite strain rates. It enables discovery of the parameters governing the thermodynamic strain rate effect, provides a method for proper interpretation of the results of the tests of dynamic plasticity, and suggests a way of planning experiments in order to detect the real contribution of viscosity.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Struct. and Solid Mech., 1982; p 113-127
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    Nonlinear constitutive theory for turbine engine structural analysis (1982)
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    Publication Date: 2011-08-18
    Description: A number of viscoplastic constitutive theories and a conventional constitutive theory are evaluated and compared in their ability to predict nonlinear stress-strain behavior in gas turbine engine components at elevated temperatures. Specific application of these theories is directed towards the structural analysis of combustor liners undergoing transient, cyclic, thermomechanical load histories. The combustor liner material considered in this study is Hastelloy X. The material constants for each of the theories (as a function of temperature) are obtained from existing, published experimental data. The viscoplastic theories and a conventional theory are incorporated into a general purpose, nonlinear, finite element computer program. Several numerical examples of combustor liner structural analysis using these theories are given to demonstrate their capabilities. Based on the numerical stress-strain results, the theories are evaluated and compared.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Struct. and Solid Mech., 1982; p 67-96
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    A semi-implicit dynamic relaxation algorithm for static nonlinear structural analysis (1982)
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    Publication Date: 2011-08-18
    Description: A semiimplicit dynamic relaxation technique for solution of the nonlinear structural equlibrium equation is presented. A previously presented basic transient response analysis algorithm is employed, permitting use of one solution method and one software module for both static and dynamic analyses. A theoretical comparison of the method with explicit dynamic relaxation techniques shows that it offers a substantially improved convergence property without additional computational overhead.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Struct. and Solid Mech., 1982; p 1-10
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    Receiver-exciter controller design (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A description of the general design of both the block 3 and block 4 receiver-exciter controllers for the Deep Space Network (DSN) Mark IV-A System is presented along with the design approach. The controllers are designed to enable the receiver-exciter subsystem (RCV) to be configured, calibrated, initialized and operated from a central location via high level instructions. The RECs are designed to be operated under the control of the DMC subsystem. The instructions are in the form of standard subsystem blocks (SSBs) received via the local area network (LAN). The centralized control provided by RECs and other DSCC controllers in Mark IV-A is intended to reduce DSN operations costs from the Mark III era.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 117-125
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    DSN RFI susceptibility models development program overview (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The RFI model development described intended to provide an understanding of the interference susceptibility of DSN receivers. An overview of interference types and effects, analytic modelling and experimental verification is presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 103-109
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    Goldstone radio spectrum signal identification, March 1980 - March 1982 (1982)
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    Publication Date: 2011-08-18
    Description: The signal identification process is described. The Goldstone radio spectrum environment contains signals that are a potential source of electromagnetic interference to the Goldstone tracking receivers. The identification of these signals is accomplished by the use of signal parameters and environment parameters. Statistical data on the Goldstone radio spectrum environment from 2285 to 2305 MHz are provided.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 197-199
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    Applicaton of radiative transfer theory to microwave transmission medium calibrations (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Precise determinations of the transmission medium loss and noise temperature contribution which are important to the performance characterization of low noise microwave receiving systems and thermal noise standards are discussed. Tropospheric loss is frequently inferred from microwave radiometer noise temperature measurements. Interpretation of these measurements requires an inversion of the radiative transfer integral equation. This is inconvenient even with computer techniques. Solutions of a rapidly convergent power series of the radiative transfer equations are presented. This solution is applicable to a low loss medium with either uniform or nonuniform loss distributions. A four layer atmosphere model is investigated to demonstrate the accuracy of the solution relative to the model. Applications include thermal noise standards and single- and dual-frequency water radiometers.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 179-188
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    Analysis, prediction and control of radio frequency interference with respect to DSN (1982)
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    Publication Date: 2011-08-18
    Description: Susceptibility modeling, prediction of radio frequency interference from satellites, operational radio frequency interference control, and international regulations are considered. The existing satellite interference prediction program DSIP2 is emphasized. A summary status evaluation and recommendations for future work are given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 81-100
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    RF processing (1982)
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    Publication Date: 2011-08-18
    Description: The Loran-C radio frequency processing is discussed. A diagram which generally illustrates the automatic gain control is presented. The augmented differentiator for pulse envelopes adapts conventional communications receiver with wideband AM capability to detect pulse signals such as Loran-C. The circuit enhances reception for surveillance and observation of HF over-the-horizon radar signals or others where time difference estimates between pulse returns are of interest. The high resolution VLF spectrum which receives weak VLF signals by using an HP 3581A wave analyzer detecting signals with a very narrow bandwidth of only 3 Hz is also presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Langley Research Center Joint Univ. Program for Air Transportation Res., 1981; p 165-172
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    Operations of the reconfigured Ground Communications Facility Central Communications Terminal and the Network Operations Control Center (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The ground communications facility (GCF) central communications terminal and network operations control center (NOCC) hardware was rearranged, supplemented, and modified, and software programs changed to provide an improved GCF and NOCC operational environment and capability. Control center operations section activities required to make the changeover from the old to the new GCF and NOCC configuration are addressed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 122-129
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    the finite element machine: An experiment in parallel processing (1982)
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    Publication Date: 2011-08-18
    Description: The Finite Element Machine at the NASA Langley Research Center is a prototype computer designed to support parallel solutions to structural analysis problems. The hardware architecture and support software for the machine, initial solution algorithms and test applications, and preliminary results are described. Directions for future work are presented.
    Keywords: STRUCTURAL MECHANICS
    Type: Res. in Struct. and Solid Mech., 1982; p 201-217
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  • 77
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    Integration of multidimensional regions with applications to finite element analysis (1982)
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    Publication Date: 2011-08-18
    Description: Alternatives to Gaussian integration methods for multidimensional regions are presented. These rules preserve the convergence behavior of the exact integrated element but require fewer evaluation points than the Gauss methods. Numerical examples are given to verify the behavior of the new integration rules.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Struct. and Solid Mech., 1982; p 171-183
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    A novel boundary element method program for heat transfer analysis of composite materials (1982)
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    Publication Date: 2011-08-18
    Description: A boundary element method computer program developed for heat transfer analysis of two dimensional composite structures is described. The program runs on a time share mode and interacts with the user for multirun analysis. During a run, the geometry can be modified interactively by the user as many times as desired by using various options available and the new results printed or plotted. A concept of plotting the results for boundary element method is introduced. The advantage of such a program over the finite element method for simple design problems is demonstrated.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Struct. and Solid Mech., 1982; p 141-152
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    Operator split methods in the numerical solution of the finite deformation elastoplastic dynamic problem (1982)
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    Publication Date: 2011-08-18
    Description: The spatial formulation of the elastoplastic dynamic problem for finite deformations is considered. A thermodynamic argument leads to an additive decomposition of the spatial rate of deformation tensor and allows an operator split of the evolutionary equations of the problem into elastic and plastic parts. This operator split is taken as the basis for the definition of a global product algorithm. In the context of finite element discretization the product algorithm entails, for every time step, the solution of a nonlinear elastodynamic problem followed by the application of plastic algorithms that operate on the stresses and internal variables at the integration points and bring in the plastic constitutive equations. Suitable plastic algorithms are discussed for the cases of perfect and hardening plasticity and viscoplasticity. The proposed formalism does not depend on any notion of smoothness of the yield surface and is applicable to arbitrary convex elastic regions, with or without corners. The stabiity properties of the global product algorithm are shown to be identical to those of the algorithm used for the integration of the nonlinear elastodynamic problem. Numerical examples illustrate the accuracy of the method.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Struct. and Solid Mech., 1982; p 25-47
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    Field interface module for antenna control assembly (1982)
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    Publication Date: 2011-08-18
    Description: The hardware aspects and capabilities of the field interface module (FIM) developed for monitor and control functions in the antenna mechanical subsystems of the deep space network and in the technical facilities controllers for the various complexes are described. The FIM is capable of monitoring and responding to a range of anaog and digital inputs and controlling external elements. The flexibility of the design makes it applicable to other control needs, using software developed for those specific applications.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 107-112
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    New CCIR papers on telecommunications for deep space research (1982)
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    Publication Date: 2011-08-18
    Description: Three draft reports submitted by JPL to the International Radio Consultative Committee (CCIR) for inclusion in their 1982 edition of reports and recommendations are presented. Potential interference between deep space telecommunications and the fixed satellite and broadcasting satellite services in harmonically related bands, protection criteria and sharing considerations relating to deep space research, and preferred frequencies and bandwidths for deep space research are considered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 62-80
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  • 82
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    Dynamic response of lined tunnels by boundary elements (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The dynamic stress concentration manifested around a lined cylindrical tunnel buried in an infinitely extending linear elastic or viscoelastic medium due to the passage of transient disturbances was investigated. Plane strain is assumed to hold and the transient disturbances can be of any arbitrary time variation. The boundary element method formulated in the Laplace transform domain is employed. Isoparametric boundary elements are used in the discretization of the liner and tunnel surfaces. Viscoelastic material behavior can be readily obtained from the linear elastic case in the Laplace transform domain through the use of the correspondence principle. The transient solution is recovered by numerical inversion of the solution obtained in the transformed domain.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Research Center Res. in Struct. and Solid Mech., 1982; p 251-264
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    Radiation patterns of interfacial dipole antennas (1982)
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    Publication Date: 2011-08-18
    Description: The radiation pattern of an infinitesimal electric dipole is calculated for the case where the dipole is vertically located on the plane interface of two dielectric half spaces and for the case where the dipole is lying horizontally along the interface. For the vertical case, it is found that the radiation pattern has nulls at the interface and along the dipole axis. For the horizontal case, it is found that the pattern has a null at the interface; that the pattern in the upper half space, whose index of refraction is taken to be less than that of the lower half space, has a single lobe whose maximum is normal to the interface; and that in the lower half space, in the plane normal to the interface and containing the dipole, the pattern has three lobes, whereas in the plane normal to the interface and normally bisecting the dipole, the pattern has two maxima located symmetrically about a minimum. Interpretation of these results in terms of the Cerenkov effect is given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 17; Nov
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    Multiple scattering calculations of rain effects (1982)
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    Publication Date: 2011-08-18
    Description: The multiple scattering calculations of rain effects are studied on the basis of calculating the incoherent intensity at 30, 60, 90, and 120 GHz. The Mie solution and the Laws-Parsons distribution are used to determine scattering and absorption characteristics. The equation of transfer and the Stokes parameters are used to determine incoherent intensities for the horizontal and vertical polarizations. The ratio of the copolarized incoherent intensity to the copolarized coherent intensity is defined as the incoherent copolarized discrimination. The ratio of the cross-polarized incoherent intensity is defined as the incoherent cross-polarized discrimination. These ratios are calculated in terms of copolarized attenuation, rain rate, and field of view. The results show that multiple scattering effects may become significant during heavy rains.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 17; Nov
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    Using NASTRAN to solve symmetric structures with nonsymmetric loads (1982)
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    Publication Date: 2011-08-18
    Description: A method for computation of reflective dihedral symmetry in symmetrical structures under nonsymmetric loads is described. The method makes it possible to confine the analysis to a half, a quarter, or an octagonal segment. The symmetry of elastic deformation is discussed, and antisymmetrical deformation is distinguished from nonsymmetrical deformation. Modes of deformation considered are axial, bending, membrane, and torsional deformation. Examples of one and two dimensional elements are presented and extended to three dimensional elements. The method of setting up a problem within NASTRAN is discussed. The technique is applied to a thick structure having quarter symmetry which was modeled with polyhedra and subjected to five distinct loads having varying degrees of symmetry.
    Keywords: STRUCTURAL MECHANICS
    Type: 10th NASTRAN User's Colloq.; p 216-232
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    On elastic-plastic analysis of an overloaded breech ring using NASTRAN (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The piece-wise linear analysis option of the NASTRAN code was used to analyze a photoplastic model for a sliding breech mechanism. A two dimensional finite element representation for the breech ring was chosen and the material was made of polycarbonate resin. The aluminum block was regarded as rigid and the width of contact was assumed to remain unchanged during loading. The displacements and stresses in the breech ring were obtained for loading in the elastic as well as plastic range. The maximum tensile stresses before and after complete unloading were obtained and compared with numerical and experimental results.
    Keywords: STRUCTURAL MECHANICS
    Type: Georgia Univ. 10th NASTRAN User's Colloq.; p 143-152
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    Prediction of bead area contact load at the tire-wheel interface using NASTRAN (1982)
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    Publication Date: 2011-08-18
    Description: The theoretical prediction of the bead area contact load at the tire wheel interface using NASTRAN is reported. The application of the linear code to a basically nonlinear problem results in excessive deformation of the structure and the tire-wheel contact conditions become impossible to achieve. A psuedo-nonlinear approach was adopted in which the moduli of the cord reinforced composite are increased so that the computed key deformations matched that of the experiment. Numerical results presented are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: Georgia Univ. 10th NASTRAN User's Colloq.; p 133-142
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    On the use of harmonic expansions in magnetic field problems in NASTRAN (1982)
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    Publication Date: 2011-08-18
    Description: The use of a prolate spheroidal harmonic expansion to compute far field results in magnetics problems with the DTNSRDC version of NASTRAN is demonstrated. When field problems with infinite exterior domains are solved by the finite element method, the domain must be modeled to infinity. The density of the finite element mesh usually decreases as the distance from the structure increases, thus degrading the results in the far field.
    Keywords: STRUCTURAL MECHANICS
    Type: Georgia Univ. 10th NASTRAN User's Colloq.; p 65-73
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    Operating in the age of NASTRAN (1982)
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    Publication Date: 2011-08-18
    Description: The history of the development of the NASTRAN computer program, a general purpose finite element code for structural analysis, is described. The need for research programs to improve analysis of structures, and the writing of a computer program to give numerical solutions for shell behavior, were the impetus for the program design. The use of finite elements to obtain engineering solutions was introduced. The architecture, solution structure, DMAP language, decomposition technique for banded matrices with active columns, general purpose plotter, engineering data inputs, elastic element routines, programmer manuals, of NASTRAN's system design are described.
    Keywords: STRUCTURAL MECHANICS
    Type: 10th NASTRAN User's Colloq.; p 1-11
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    Real-time optical synthetic aperture radar /SAR/ processor (1982)
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    Publication Date: 2011-08-18
    Description: A description is given of a real-time optical synthetic aperture radar (SAR). The processor employs an acoustooptic device as the input electronic-to-optical transducer and a CCD camera that serves as the optical detector and simultaneously performs the focusing of the SAR image in the azimuth direction. The performance criteria of the optical processor that are discussed include azimuth resolution, image size in azimuth, range resolution, image size in range, flexibility, and dynamic range.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Optical Engineering; 21; Sept
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    Recent advances in electromagnetic synthesis and analysis of dual-shaped reflector antennas (1982)
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    Publication Date: 2011-08-18
    Description: Dual-shaped reflectors have been used for many years. Thus, these reflectors have been used as high gain antennas on Voyagers 1 and 2. The objectives of the geometrical optics (GO) dual shaped synthesis are considered. Concerning the synthesis of dual shaped reflectors, it has been shown for circular symmetric reflectors that an exact GO solution can be found to the problem of transforming, by two reflections, any feed pattern into any aperture distribution. This problem involves solving two simultaneous nonlinear ordinary differential equations. The same approach for offset geometry leads to two simultaneous nonlinear partial differential equations. It is shown that these equations could also be integrated numerically, except that in general these equations are not total and therefore, in general, they do not have a 'smooth' solution. It is further shown that the offset partial differentials often very nearly form a total differential in many cases of practical importance.
    Keywords: COMMUNICATIONS AND RADAR
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    The performance of M-ary FH-DPSK in the presence of partial-band multitone jamming (1982)
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    Publication Date: 2011-08-18
    Description: Using a geometric approach, the performance of M-ary FH-DPSK in the presence of partial-band multitone jamming is evaluated. The optimal jamming strategy is determined as a function of the number of signaling levels M and the ensuing results are used to determine worst case bit error probability performance as a function of this same parameter. It is demonstrated that, for M = 2 to the m power (where m is an integer), the best performance is obtained for M = 4.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-30; May 1982
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    Statics of wrinkling films (1982)
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    Publication Date: 2011-08-18
    Description: An analytical investigation of the equilibrium of wrinkling films is conducted. Zak (1979) has shown that wrinkling occurs in connection with the instability of a smooth film having no resistance to bending in the case of compression. The governing equation for the equilibrium of a film with possible regions of wrinkling is considered. The introduction of fictitious stress reduces the governing equation to a form which formally coincides with the governing equation for a string. Equilibrium conditions in the case of an absence of external forces are explored, taking into account the stretching of a semispherical film, the torsion of a convex film of revolution, and stress singularities. A study is conducted of the equilibrium under conditions in which external forces normal to the surface of a film are present. Attention is also given to the equilibrium in a potential field.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Elasticity; 12; Jan. 198
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    Differentially coherent detection of QASK for frequency-hopping systems. II - Performance in the presence of jamming (1982)
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    Publication Date: 2011-08-18
    Description: The performance of differentially coherent detection of frequency-hopped QASK in the presence of partial-band noise and partial-band multitone jamming is presented. In each case, the worst case jamming strategy is determined which consists of specifying the worst case partial-band fraction and the corresponding maximum average error probability. The results obtained are compared with those of M-ary FH-DPSK operating in the same jamming environment.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-30; Jan. 198
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  • 95
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    Differentially coherent detection of QASK for frequency-hopping systems. I - Performance in the presence of a Gaussian noise environment (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Bandwidth-conserving modulation techniques, which trade average power for bandwidth in a favorable exchange, have recently found widespread application in digital radio and satellite communication systems. Quadrature amplitude-shift-keying (QASK) is a particular type of the considered techniques. QASK makes use of multilevel signals to amplitude modulate the in-phase and quadrature components of a carrier. Frequency hopping (FH) is used to protect a conventional communication system from radio frequency interference (RFI) or jamming. Differentially coherent detection provides a possible solution to the effect of phase discontinuities introduced by FH. The application of such a detection technique to QASK signals is discussed. A receiver structure is proposed and its symbol error probability performance for an additive white Gaussian noise (AWGN) background is investigated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-30; Jan. 198
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    Extensional collapse modes of structural members (1982)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: Attenuation of the load transmitted to a vehicle occupant by the structure, either by modifying structural assembly, changing geometry of its elements, or adding specific load limiting devices to help dissipate kinetic energy was studied. General aviation aircraft have fuselage subfloors of a built up structure which are generally very stiff perpendicular to the floor of the cabin. The subfloor structure, designed to crush at an appropriate force level, can be used to advantage in a crash by dissipating energy through plastic buckling of the floor beams and frames. Simple closed form solutions to predict the mean crushing force levels of subfloor designs is useful in engineering practice. The crushing process of thin walled, plate formed, open structures with particular emphasis on L and cruciform shapes was analyzed. Lower and upper bound solutions for the mean crushing strength of cruciforms are obtained by considering modes of deformation which account for both bending and extensional deformation. It is the importance of extensional deformation to the energy absorption process, representing at least one third of the dissipated energy is shown.
    Keywords: STRUCTURAL MECHANICS
    Type: Res. in Struct. and Solid Mech., 1982; p 405-434
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    Structural fatigue test results for large wind turbine blade sections (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: In order to provide quantitative information on the operating life capabilities of wind turbine rotor blade concepts for root-end load transfer, a series of cantilever beam fatigue tests was conducted. Fatigue tests were conducted on a laminated wood blade with bonded steel studs, a low cost steel spar (utility pole) with a welded flange, a utility pole with additional root-end thickness provided by a swaged collar, fiberglass spars with both bonded and nonbonded fittings, and, finally, an aluminum blade with a bolted steel fitting (Lockheed Mod-0 blade). Photographs, data, and conclusions for each of these tests are presented. In addition, the aluminum blade test results are compared to field failure information; these results provide evidence that the cantilever beam type of fatigue test is a satisfactory method for obtaining qualitative data on blade life expectancy and for identifying structurally underdesigned areas (hot spots).
    Keywords: STRUCTURAL MECHANICS
    Type: Large Horizontal-Axis Wind Turbines; p 303-328
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  • 98
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    The application of digital signal processing techniques to a teleoperator radar system (1982)
    In:  Other Sources
    Details
    Publication Date: 2016-06-07
    Description: A digital signal processing system was studied for the determination of the spectral frequency distribution of echo signals from a teleoperator radar system. The system consisted of a sample and hold circuit, an analog to digital converter, a digital filter, and a Fast Fourier Transform. The system is interfaced to a 16 bit microprocessor. The microprocessor is programmed to control the complete digital signal processing. The digital filtering and Fast Fourier Transform functions are implemented by a S2815 digital filter/utility peripheral chip and a S2814A Fast Fourier Transform chip. The S2815 initially simulates a low-pass Butterworth filter with later expansion to complete filter circuit (bandpass and highpass) synthesizing.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Marshall Space Flight Center The 1982 NASA(ASEE Summer Fac. Fellowship Program; 20 p
    Format: text
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  • 99
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    Deep Space Communications Complex Command Subsystem Mark IVA (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The Deep Space Communications Complex Command Subsystem will require major changes for the Mark IVA era. A description of the subsystem and its assemblies is contained in this article.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. J.; p 129-136
    Format: application/pdf
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  • 100
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    Direct comparison of Viking 2.3-GHz signal phase fluctuation and columnar electron density between 2 and 160 solar radii (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The relationship between solar wind induced signal phase fluctuation and solar wind columnar electron density has been the subject of intensive analysis during the last two decades. In this article, a sizeable volume of 2.3-GHz signal phase fluctuation and columnar electron density measurements separately and concurrently inferred from Viking spacecraft signals are compared as a function of solar geometry. These data demonstrate that signal phase fluctuation and columnar electron density are proportional over a very wide span of solar elongation angle. A radially dependent electron density model which provides a good fit to the columnar electron density measurements and, when appropriately scaled, to the signal phase fluctuation measurements, is given. This model is also in good agreement with K-coronameter observations at 2 solar radii (2r0), with pulsar time delay measurements at 10r0, and with spacecraft in situ electron density measurements at 1 AU.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. J.; p 117-128
    Format: application/pdf
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