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  • Other Sources  (101)
  • FLUID MECHANICS AND HEAT TRANSFER  (40)
  • STRUCTURAL MECHANICS  (32)
  • COMMUNICATIONS AND RADAR  (29)
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  • Chemical Engineering
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  • SPACE SCIENCES
  • 1990-1994
  • 1980-1984  (101)
  • 1982  (101)
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  • 1990-1994
  • 1980-1984  (101)
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  • 1
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    Sideband-aided receiver arraying (1982)
    In:  Other Sources
    Details
    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
    Format: text
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  • 2
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    An interactive review system for NASTRAN (1982)
    In:  Other Sources
    Details
    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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  • 3
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    ADI on staggered mesh - A method for the calculation of compressible convection (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: An alternating direction implicit (ADI) method has been applied to a staggered grid for the computation of convection in a highly stratified fluid. Since artificial viscosity is not needed, subtle effects like the onset of convection can be studied. These computations compare well with the 2-D results by Graham (1975) and also agree with standard Boussinesq results when taken to that limit. Good efficiency has been achieved with a time step hundreds of times larger than the stability limit imposed by the explicit treatment of diffusion and the Courant number is not restricted to be below 1. The Navier-Stokes equation contains cross spatial derivatives which are treated explicitly in most ADI schemes. The destabilizing effect of such a practice on a 2-D model system with second-order spatial derivative terms only was analyzed and found to be not excessive.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Computational Physics (ISSN 0021-9991); 47; July 198
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  • 4
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    Reentry heat transfer analysis of the space shuttle orbiter (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A structural performance and resizing finite element thermal analysis computer program was used in the reentry heat transfer analysis of the space shuttle. Two typical wing cross sections and a midfuselage cross section were selected for the analysis. The surface heat inputs to the thermal models were obtained from aerodynamic heating analyses, which assumed a purely turbulent boundary layer, a purely laminar boundary layer, separated flow, and transition from laminar to turbulent flow. The effect of internal radiation was found to be quite significant. With the effect of the internal radiation considered, the wing lower skin temperature became about 39 C (70 F) lower. The results were compared with fight data for space transportation system, trajectory 1. The calculated and measured temperatures compared well for the wing if laminar flow was assumed for the lower surface and bay one upper surface and if separated flow was assumed for the upper surfaces of bays other than bay one. For the fuselage, good agreement between the calculated and measured data was obtained if laminar flow was assumed for the bottom surface. The structural temperatures were found to reach their peak values shortly before touchdown. In addition, the finite element solutions were compared with those obtained from the conventional finite difference solutions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Langley Research Center Computational Aspects of Heat Transfer in Struct.; p 295-325
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  • 5
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    Viterbi decoder node synchronization losses in the Reed-Solomon/Veterbi concatenated channel (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The Viterbi decoders currently used by the Deep Space Network (DSN) employ an algorithm for maintaining node synchronization that significantly degrades at bit signal-to-noise ratios (SNRs) of below 2.0 dB. In a recent report by the authors, it was shown that the telemetry receiving system, which uses a convolutionally encoded downlink, will suffer losses of 0.85 dB and 1.25 dB respectively at Voyager 2 Uranus and Neptune encounters. This report extends the results of that study to a concatenated (255,223) Reed-Solomon/(7, 1/2) convolutionally coded channel, by developing a new radio loss model for the concatenated channel. It is shown here that losses due to improper node synchronization of 0.57 dB at Uranus and 1.0 dB at Neptune can be expected if concatenated coding is used along with an array of one 64-meter and three 34-meter antennas.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. J.; p 73-80
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  • 6
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    Reentry heating analysis of space shuttle with comparison of flight data (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Surface heating rates and surface temperatures for a space shuttle reentry profile were calculated for two wing cross sections and one fuselage cross section. Heating rates and temperatures at 12 locations on the wing and 6 locations on the fuselage are presented. The heating on the lower wing was most severe, with peak temperatures reaching values of 1240 C for turbulent flow and 900 C for laminar flow. For the fuselage, the most severe heating occured on the lower glove surface where peak temperatures of 910 C and 700 C were calculated for turbulent flow and laminar flow, respectively. Aluminum structural temperatures were calculated using a finite difference thermal analyzer computer program, and the predicted temperatures are compared to measured flight data. Skin temperatures measured on the lower surface of the wing and bay 1 of the upper surface of the wing agreed best with temperatures calculated assuming laminar flow. The measured temperatures at bays two and four on the upper surface of the wing were in quite good agreement with the temperatures calculated assuming separated flow. The measured temperatures on the lower forward spar cap of bay four were in good agreement with values predicted assuming laminar flow.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Langley Research Center Computational Aspects of Heat Transfer in Struct.; p 271-294
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  • 7
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    Analytical modeling of operating characteristics of premixing-prevaporizing fuel-air mixing passages. Volume 2: User's manual (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A user's manual describing the operation of three computer codes (ADD code, PTRAK code, and VAPDIF code) is presented. The general features of the computer codes, the input/output formats, run streams, and sample input cases are described.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-167990-VOL-2 , NAS 1.26:167990-V0L-2 , R82-915362-40-VOL-2
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  • 8
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    Computation of transonic viscous-inviscid interacting flow (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Transonic viscous-inviscid interaction is considered using the Euler and inverse compressible turbulent boundary-layer equations. Certain improvements in the inverse boundary-layer method are mentioned, along with experiences in using various Runge-Kutta schemes to solve the Euler equations. Numerical conditions imposed on the Euler equations at a surface for viscous-inviscid interaction using the method of equivalent sources are developed, and numerical solutions are presented and compared with experimental data to illustrate essential points.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-85203 , NAS 1.15:85203
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  • 9
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    Analytical modeling of operating characteristics of premixing-prevaporizing fuel-air mixing passages. Volume 1: Analysis and results (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A model for predicting the distribution of liquid fuel droplets and fuel vapor in premixing-prevaporizing fuel-air mixing passages of the direct injection type is reported. This model consists of three computer programs; a calculation of the two dimensional or axisymmetric air flow field neglecting the effects of fuel; a calculation of the three dimensional fuel droplet trajectories and evaporation rates in a known, moving air flow; a calculation of fuel vapor diffusing into a moving three dimensional air flow with source terms dependent on the droplet evaporation rates. The fuel droplets are treated as individual particle classes each satisfying Newton's law, a heat transfer, and a mass transfer equation. This fuel droplet model treats multicomponent fuels and incorporates the physics required for the treatment of elastic droplet collisions, droplet shattering, droplet coalescence and droplet wall interactions. The vapor diffusion calculation treats three dimensional, gas phase, turbulent diffusion processes. The analysis includes a model for the autoignition of the fuel air mixture based upon the rate of formation of an important intermediate chemical species during the preignition period.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-167990-VOL-1 , NAS 1.26:167990-VOL-1 , R82-915362-40-VOL-1
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  • 10
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    Integrating matrix solution of the hybrid state vector equations for beam vibration (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A simple, versatile, and efficient computational technique has been developed for dynamic analysis of linear elastic beam and rod type of structures. Moreover, the method provides a rather general solution approach for two-point boundary value problems that are described by a single independent spatial variable. For structural problems, the method is implemented by a mixed state vector formulation of the differential equations, combined with an integrating matrix solution procedure. Highly accurate solutions are easily achieved with this approach. Example solutions are given for beam vibration problems including discontinuous stiffness and mass parameters, elastic restraint boundary conditions, concentrated inertia loading, and rigid body modes
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA PAPER 82-0732 , In: Structures, Structural Dynamics and Materials Conference; May 10, 1982 - May 12, 1982; New Orleans, LA
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