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NASA NTRS1972

Satellite aerodynamics as a function of atmospheric properties.

Demonstration that satellite aerodynamic properties are a function of numerous factors associated with atmospheric properties. Among these factors, the gas composition has influence on the gas surface interaction which in turn has considerable influence on the satellite drag and lift properties. The drag and lift properties, which are also influenced by the orientation of the satellite with respect to the flow, are influenced by upper atmospheric winds which cause changes in the angle of attack of the satellite. Another strong influence on the aerodynamic properties is due to the speed ratio effect which is found to cause a systematic increase in drag coefficient with respect to altitude. The study of these factors is facilitated by the introduction of a generalized gas surface interaction model which is capable of representing a wide range of possible interactions.

Karr, G. R.↗

NASA NTRS1972

Electromagnetic wave propagation and wave-vector diagram in space-time periodic media.

Analysis of TE and TM wave propagation in space-time periodic media such as dielectrics, isotropic plasmas and uniaxial plasmas. A numerical solution is obtained for media with sinusoidal periodicity. Wave-vector diagrams are plotted to facilitate studies of dipole radiation, wave propagation in waveguides and wave interactions with a half-space.

Elachi, C.↗

NASA NTRS1972

On the equinoctial orbit elements.

This paper investigates the equinoctial orbit elements for the two-body problem, showing that the associated matrices are free from singularities for zero eccentricities and zero and ninety degree inclinations. The matrix of the partial derivatives of the position and velocity vectors with respect to the orbit elements is given explicitly, together with the matrix of inverse partial derivatives, in order to facilitate construction of the matrizant (state transition matrix) corresponding to these elements. The Lagrange and Poisson bracket matrices are also given. The application of the equinoctial orbit elements to general and special perturbations is discussed.

Broucke, R. A.↗

NASA NTRS1972

Energy-ratio function for center-of-gravity feedback.

An energy-ratio function is introduced which greatly facilitates analysis and signal design for center-of-gravity feedback communication schemes. Using this function, we show that center-of-gravity feedback using regular-simplex signals achieves Shannon's lower bound on average energy per transmission for zero error probability if M, the number of messages, is 3, 4, or 5 and there is no constraint on system bandwidth.

Fang, T.-T.↗

NASA NTRS1972

A second quantized model of anharmonicity.

A heuristic description is given for a simple harmonic oscillator as a basis for a model of anharmonicity. A formalism is applied in the process, which applies to complex excitation fields involving particle clusters and also facilitates a description of nonequilibrium multibody configurations by classical methods. The heuristic description is based on Streit's results (1965) and is free of linearization requirements in most physically interesting situations.

Rasetti, M.↗

NASA NTRS1972

Spatial distribution of energetic plasma sheet electrons.

The spatial distribution of energetic plasma sheet electrons (E greater than 50 keV) out to a radial distance of 24 earth radii using data from electron spectrometer and fluxgate magnetometer experiments on Ogo 5 is presented. A comparison of distributions in geocentric solar magnetospheric coordinates (GSM) prepared with and without the use of a neutral sheet model indicates that the use of such a model facilitates organization of plasma sheet data. The percentage of flux occurrence above a given flux threshold falls off rapidly with distance from the neutral sheet. Contours of constant percentage of occurrence diverge slightly from the neutral sheet at local times away from midnight. This effect decreases with increasing flux threshold.

Walker, R. J.↗

NASA NTRS1972

Measurement of longitudinal relaxation times for spin-decoupled protons.

Description of an experimental method for the determination of the longitudinal relaxation time for spin-decoupled protons by a modified version of the saturation recovery technique reported by Van Geet and Hume (1965). The described method should facilitate relaxation studies of chemically shifted protons (or fluorines) and can be applied to more complicated spin systems with the aid of triple resonance and noise-decoupling techniques.

Gerace, M. J.↗

NASA NTRS1972

Computers formed by the problems rather than problems deformed by the computers.

Description of an approach to computer programming which tries to minimize the time required for retranslation from the computer language into the language of the original process. A notion of a programmable network is introduced which allows the abstract machines that are a model of the processes in the user's mind to be put into a rigorous and simple form. Each process is then modeled as a particular finite-state machine, a circulating page loose system being employed as an architecture for implementing these finite-state machines. An experiment is discussed in which the use of abstract machines as a language for modeling processes, in conjunction with the use of a self-organizing computer, decreases user effort, eliminates the need for compilation, facilitates debugging, and decreases computer time.

Schaffner, M. R.↗

NASA NTRS1973

Vapor phase growth of group 3, 4, and 5 compounds by HCl transport of elements

Technique has been devised for vapor-phase epitaxial growth of group 3, 4, and 5 binary, ternary, or quaternary compounds by HCl transport of the constituent elements or dopants. Technique uses all the constituents of the alloy system in their elemental form. Transport of these elements by an HCl + H2 carrier gas facilitates their transport as subchlorides.

Tyagi, R. C.↗

NASA NTRS1973

A new optical recording medium

Method has been developed for doping lithium niobiate crystals with transition metal to increase rate at which crystal can record optical data. Discovery may facilitate development of system for analog storage of TV frames, printed pages, photographs, and other visual information.

Aronson, H.↗

NASA NTRS1974

Design parameters for toroidal and bobbin magnetics

Handbook has been published to facilitate conversion to metric system. Conversion data makes it possible for transformer designers to obtain fast and close approximation of significant parameters. For greater convenience, derivations of some transformer and inductor parameters are also presented.

Mclyman, W. T.↗

NASA NTRS1972

A computer assisted teleoperator control station with tactile feedback

A computer-assisted teleoperator control system for making comparative performance evaluations is described. A local and a remote control station, each with decision-making capability, communicate with each other through a simulated time delay. Supervisory control at three increasingly automatic levels is possible. The highest level of programmed control is facilitated through the ARM language which was developed to permit easily readable program manuscripts to be written and assembled into programs of motions by novice programmers. Experimental results show the advantage of this form of supervisory control with both direct and delayed (3 sec) manipulation tasks. In addition, two systems to measure and reproduce force distributions have been designed. One system reproduces contact on the external surfaces of the remote hand using 21 airjet simulators. Another system reproduces the shape of the contact between object and jaws using 288 piezoelectric (bimorph) stimulators.

Hill, J. W.↗

NASA NTRS1972

Charts for predicting turbulent skin friction from the Van Driest method (2)

Charts are presented for rapidly estimating local or average turbulent skin friction on flat plates from Reynolds numbers, based on either length or momentum thickness. These charts facilitate the conversion from one Reynolds number to the other. Ranges of variables covered are: Mach number, 0 to 10; length Reynolds number, 10 to the 5th to 10 to the 9th power; and wall-to-adiabatic-wall temperature ratio, 0.2 to 1.0.

Hopkins, E. J.↗

NASA NTRS1972

Solid rocket motor cost model

A systematic and standardized procedure for estimating life cycle costs of solid rocket motor booster configurations. The model consists of clearly defined cost categories and appropriate cost equations in which cost is related to program and hardware parameters. Cost estimating relationships are generally based on analogous experience. In this model the experience drawn on is from estimates prepared by the study contractors. Contractors' estimates are derived by means of engineering estimates for some predetermined level of detail of the SRM hardware and program functions of the system life cycle. This method is frequently referred to as bottom-up. A parametric cost analysis is a useful technique when rapid estimates are required. This is particularly true during the planning stages of a system when hardware designs and program definition are conceptual and constantly changing as the selection process, which includes cost comparisons or trade-offs, is performed. The use of cost estimating relationships also facilitates the performance of cost sensitivity studies in which relative and comparable cost comparisons are significant.

Harney, A. G.↗

NASA NTRS1972

Research and Technology Operating Plan Summary: Fiscal Year 1973 Research and Technology Program

Abstracts are presented of each of the Research and Technology Operating Plans (RTOP) used for management review and control of research currently in progress throughout NASA. This RTOP Summary is designed to facilitate communication and coordination among concerned technical personnel in government, industry, and universities. The summary is arranged in five sections consisting of citations and abstracts of the RTOPs and subject, technical monitor, responsible NASA organization, and RTOP number indexes.

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NASA NTRS1972

Experimental investigation of a throttlable 15 cm hollow cathode ion thruster

The use of dished high perveance grids on a 15 cm modified SERT 2 thruster is shown to facilitate throttled operation over a beam current range from 60 to 600 mA. Effects of increasing the radial component of the magnetic field in the main discharge chamber and decreasing the dimensions of the cathode discharge region are examined and found to degrade performance to the extent that primary electrons are forced in toward the center-line of the thruster. Studies of the baffle aperture region of two thrusters indicate that the electric potential gradient vector is perpendicular to the local magnetic field lines when the thruster is operating properly. The correlation between the shape of the ion beam current density and that of the ion density at the screen grid within the thruster is shown to be 94%. Additional experimental studies on maximum propellant utilization, plasma ion production cost, neutral density in the cathode discharge region, double ion production in hollow cathode thrusters and thermal flow meter performance are discussed.

Wilbur, P. J.↗

NASA NTRS1972

Optimization of thermal protection systems for the space shuttle vehicle. Volume 1: Final report

A study performed to continue development of computational techniques for the Space Shuttle Thermal Protection System is reported. The resulting computer code was used to perform some additional optimization studies on several TPS configurations. The program was developed in Fortran 4 for the CDC 6400, and it was converted to Fortran 5 to be used for the Univac 1108. The computational methodology is developed in modular fashion to facilitate changes and updating of the techniques and to allow overlaying the computer code to fit into approximately 131,000 octal words of core storage. The program logic involves subroutines which handle input and output of information between computer and user, thermodynamic stress, dynamic, and weight/estimate analyses of a variety of panel configurations. These include metallic, ablative, RSI (with and without an underlying phase change material), and a thermodynamic analysis only of carbon-carbon systems applied to the leading edge and flat cover panels. Two different thermodynamic analyses are used. The first is a two-dimensional, explicit precedure with variable time steps which is used to describe the behavior of metallic and carbon-carbon leading edges. The second is a one-dimensional implicity technique used to predict temperature in the charring ablator and the noncharring RSI. The latter analysis is performed simply by suppressing the chemical reactions and pyrolysis of the TPS material.

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NASA NTRS1972

Earth resources data analysis system

The Earth Resources Laboratory Data Analysis System provides a valuable research tool in the evaluation of multispectral, radiometric, photographic, and passive microwave imagery data. The system has been in operational use for several months and has performed quite well. Emphasis on versatility of both the hardware and software design facilitates system expansion to many specialized data analysis tasks. The many independent software handlers provide building blocks for major processing programs.

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