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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

The proposed coding standard at GSFC

As part of the continuing effort to introduce standardization of spacecraft and ground equipment in satellite systems, NASA's Goddard Space Flight Center and other NASA facilities have supported the development of a set of standards for the use of error control coding in telemetry subsystems. These standards are intended to ensure compatibility between spacecraft and ground encoding equipment, while allowing sufficient flexibility to meet all anticipated mission requirements. The standards which have been developed to date cover the application of block codes in error detection and error correction modes, as well as short and long constraint length convolutional codes decoded via the Viterbi and sequential decoding algorithms, respectively. Included are detailed specifications of the codes, and their implementation. Current effort is directed toward the development of standards covering channels with burst noise characteristics, channels with feedback, and code concatenation.

Morakis, J. C.↗
NASA NTRS1979

A connection between block and convolutional codes

Convolutional codes of any rate and any constraint length give rise to a sequence of quasi-cyclic codes. Conversely, any quasi-cyclic code may be convolutionally encoded. Among the quasi-cyclic codes are the quadratic residue codes, Reed-Solomon codes and optimal BCH codes. The constraint length K for the convolutional encoding of many of these codes (Golay, (48, 24) QR, etc.) turns out to be surprisingly small. Thus using the soft decoding techniques for convolutional decoding, a new maximum likelihood decoding algorithm for many block codes is established. Conversely an optimal quasi-cyclic code will yield a convolutional encoding with optimal local properties and therefore with good infinite convolutional coding properties.

Solomon, G.↗
NASA NTRS1980

Calculation of two-dimensional inlet flow fields in a supersonic free stream: Program documentation and test cases

The use of a computer code for the calculation of two dimensional inlet flow fields in a supersonic free stream and a nonorthogonal mesh-generation code are illustrated by specific examples. Input, output, and program operation and use are given and explained for the case of supercritical inlet operation at a subdesign Mach number (M Mach free stream = 2.09) for an isentropic-compression, drooped-cowl inlet. Source listings of the computer codes are also provided.

Biringen, S. H.↗
NASA NTRS1980

Polar symmetry in three-dimensional analysis of laminates with angle plies

An improved procedure for the three dimensional finite element analysis of an angle ply laminate with a circular hole is discussed. The procecure exploits polar symmetry and is the basis for a new finite element computer code. For the broad class of laminates that contain angle plies, this code requires only one half as much computing capacity as conventional codes.

Raju, I. S.↗
NASA NTRS1980

Coherence bandwidth loss in transionospheric radio propagation

In this report a theoretical model is developed that predicts the single-point, two-frequency coherence function for transionospheric radio waves. The theoretical model is compared to measured complex frequency correlation coefficients using data from the seven equispaced, phase-coherent UHF signals transmitted by the Wideband satellite. The theory and data are in excellent agreement. The theory is critically dependent upon the power-law index, and the frequency coherence data clearly favor the comparatively small spectral indices that have been consistently measured from the wideband satellite phase data. A model for estimating the pulse delay jitter induced by the coherence bandwidth loss is also developed and compared with the actual delay jitter observed on synthesized pulses obtained from the Wideband UFH comb. The results are in good agreement with the theory. The results presented in this report, which are based on an asymptotic theory, are compared with the more commonly used quadratic theory. The model developed and validated in this report can be used to predict the effects of coherence bandwidth loss in disturbed nuclear environments. Simple formulas for the resultant pulse delay jitter are derived that can be used in predictive codes.

Rino, C. L.↗
NASA NTRS1981

Experimental and theoretical study of three interacting, closely-spaced, sharp-edged 60 deg delta wings at low speeds

Wind tunnel tests were conducted to determine the subsonic longitudinal aerodynamic characteristics of lifting configuration consisting of a 60 deg delta main wing with two smaller 60 deg delta wings (called sub-wings) attached underneath. The test was designed to determine the effects on lift, drag, and pitching moment due to various placement of the subwings in relation to the main wing. Test results indicate the increasing vertical separation between the main wing and the sub-wings produced the most significant results; a 23.1% increase in maximum lift coefficient, a reduction in drag coefficient at high lift coefficients, and an increase in longitudinal stability. Lateral separation of the sub-wings produced no significant changes. Placement of the sub-wings rearward increases the initial lift curve slope and maximum lift coefficient and also increase the longitudinal stability. Results of a computer study using a vortex lattice code supported the experimental conclusions.

Faery, H. F., Jr.↗
NASA NTRS1983

Validation of a three-dimensional viscous analysis of axisymmetric supersonic inlet flow fields

A three-dimensional viscous marching analysis for supersonic inlets was developed. To verify this analysis several benchmark axisymmetric test configurations were studied and are compared to experimental data. Detailed two-dimensional results for shock-boundary layer interactions are presented for flows with and without boundary layer bleed. Three dimensional calculations of a cone at angle of attack and a full inlet at attack are also discussed and evaluated. Results of the calculations demonstrate the code's ability to predict complex flow fields and establish guidelines for future calculations using similar codes.

Benson, T. J.↗
NASA NTRS1982

Outer satellite atmospheres: Their nature and planetary interactions

Significant progress is reported in early modeling analysis of observed sodium cloud images with our new model which includes the oscillating Io plasma torus ionization sink. Both the general w-D morphology of the region B cloud as well as the large spatial gradient seen between the region A and B clouds are found to be consistent with an isotropic flux of sodium atoms from Io. Model analysis of the spatially extended high velocity directional features provided substantial evidence for a magnetospheric wind driven gas escape mechanism from Io. In our efforts to define the source(s) of hydrogen atoms in the Saturn system, major steps were taken in order to understand the role of Titan. We have completed the comparison of the Voyager UVS data with previous Titan model results, as well as the update of the old model computer code to handle the spatially varying ionization sink for H atoms.

Smyth, W. H.↗
NASA NTRS1986

Aerothermal modeling program, phase 2

The main objective of the NASA sponsored Aerothermal Modeling Program, Phase 2--Element A, is to develop an improved numerical scheme for predicting combustor flow fields. This effort consists of the following three technical tasks. Task 1 involves the selection and evaluation of various candidate numerical techniques. Task 2 involves an in-depth evaluation of the selected numerical schemes. Task 3 involves the convection-diffusion scheme and the direct solver that will be incorporated in the NASA 3-D elliptic code (COM3S).

Karki, K. C.↗
NASA NTRS1989

NASA Marshall Space Flight Center solar observatory report, January - December 1987

This report provides a description of the NASA Marshall Space Flight Center's Solar Vector Magnetograph Facility and gives a summary of its observations and data reduction during January to December 1987. The systems that make up the facility are a magnetograph telescope, an H-alpha telescope, a Questar telescope, and a computer code. The data are represented by longitudinal contours with azimuth plots.

Smith, James E.↗
NASA NTRS1988

Ion-cyclotron wave heating of heavy ions in the equatorial magnetosphere - A numerical simulation theory

A 1-2/2 dimensional hybrid numerical simulation code is used to study the heating of cold H(+) ions and heavy ions by electromagnetic ion-cyclotron waves (ICWs) in the ring current region of the equatorial magnetosphere. Consideration is given to a plasma consisting of electrons, hot H(+) ions, and cold heavy ions in which the ICWs are driven by the temperature anisotropy of the hot protons. For large-amplitude ICWs, it is found that the cold H(+) ions are preferentially heated over the heavy ions although the cold H(+) ions are heated by a three-step process.

Chen, M. W.↗
NASA NTRS1990

NASA Marshall Space Flight Center solar observatory report, January to December 1989

A description is provided of the NASA-Marshall's Solar Vector Magnetograph Facility and a summary of its observations and data reduction during January to December 1989 is given. The systems that make up the facility are a magnetograph telescope, and H-alpha telescope, a Questar telescope, and a computer code. The data are represented by longitudinal contours with azimuth plots.

Smith, James E.↗
NASA NTRS1990

NASA Marshall Space Flight Center Solar Observatory report, January - June 1990

A description of the NASA Marshall Space Flight Center's Solar Vector Magnetograph Facility is presented and a summary of its observations and data reduction is given. The systems that make up the facility are a magnetograph telescope, an H alpha telescope, a Questar telescope, and a computer code. The data are represented by longitudinal contours with azimuth plots.

Smith, James E.↗
NASA NTRS1991

NASA Marshall Space Flight Center Solar Observatory report, July - September 1990

A description of the NASA Marshall Space Flight C nter's Solar Vector Magnetograph Facility is provided and gives a summary of its observations and data reduction during Jul. - Sep. 1990. The systems that make up the facility are a magnetograph telescope, an H-alpha telescope, a Questar telescope, and a computer code. The data are represented by longitudinal contours with azimuth plots.

Smith, James E.↗
NASA NTRS1991

NASA Marshall Space Flight Center Solar Observatory report, October - December 1990

A description of the NASA Marshall Space Flight Center's Solar Vector Magnetograph Facility is provided, and a summary of its observations and data reduction during Oct. - Dec. 1990 is presented. The systems that make up the facility are a magnetograph telescope, and H-alpha telescope, a Questar telescope, and a computer code. The data are represented by longitudinal contours with azimuth plots.

Smith, James E.↗
NASA NTRS1992

NASA Marshall Space Flight Center Solar Observatory report, January - June 1992

This report provides a description of the NASA Marshall Space Flight Center's Solar Vector Magnetograph Facility and gives a summary of its observations and data reduction during Jan. to Jun. 1992. The systems that make up the facility are a magnetograph telescope, and H-alpha telescope, a Questar telescope, and a computer code.

Smith, James E.↗
NASA NTRS1993

NASA Marshall Space Flight Center Solar Observatory Report, July to December 1992

This report provides a description of the NASA Marshall Space Flight Center's Solar Vector Magnetograph Facility and gives a summary of its observations and data reduction during July-December 1992. The systems that make up the facility are a magnetograph telescope, an H-alpha telescope, a Questar telescope, and a computer code.

Smith, J. E.↗
NASA NTRS1993

NASA Marshall Space Flight Center solar observatory report, January - June 1993

This report provides a description of the NASA Marshall Space Flight Center's Solar Vector Magnetograph Facility and gives a summary of its observations and data reduction during January-June 1993. The systems that make up the facility are a magnetograph telescope, an H-alpha telescope, a Questar telescope, and a computer code.

Smith, J. E.↗