Preliminary results of the computer simulation of data compression using ERTS-A MSS digital tapes
There are no author-identified significant results in this report.
Spencer, D. J.↗
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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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Computer simulation of shock wave boundary layer interaction
Development of a boundary layer correction for an analysis program previously used by Bauer et al. (1972) to study two-dimensional flow past transonic airfoils at off-design conditions where shocks which interact with the boundary layer appear. Using a method which combines conformal mapping with a finite-difference scheme due to Murman and Cole (1971), an analysis is made of the interaction between shock waves on a supercritical wing section and a turbulent boundary layer, assuming that the shocks are weak and that separation is insignificant. It is shown that relatively simple shock wave/boundary layer interactions of the kind envisioned in this study can be treated by determining the displacement thickness iteratively together with the flow and altering the profile accordingly. It is concluded that the proposed boundary layer correction appears to furnish an essential improvement in cases where both pronounced aft loading and a large enclosed supersonic region of flow are present.
Bauer, F.↗
The computer simulation of automobile use patterns for defining battery requirements for electric cars
A Monte Carlo simulation process was used to develop the U.S. daily range requirements for an electric vehicle from probability distributions of trip lengths and frequencies and average annual mileage data. The analysis shows that a car in the U.S. with a practical daily range of 82 miles (132 km) can meet the needs of the owner on 95% of the days of the year, or at all times other than his long vacation trips. Increasing the range of the vehicle beyond this point will not make it more useful to the owner because it will still not provide intercity transportation. A daily range of 82 miles can be provided by an intermediate battery technology level characterized by an energy density of 30 to 50 watt-hours per pound (66 to 110 W-hr/kg). Candidate batteries in this class are nickel-zinc, nickel-iron, and iron-air. The implication of these results for the research goals of far-term battery systems suggests a shift in emphasis toward lower cost and greater life and away from high energy density.
Schwartz, H. J.↗
Apu/hydraulic/actuator Subsystem Computer Simulation. Space Shuttle Engineering and Operation Support, Engineering Systems Analysis
Major developments are examined which have taken place to date in the analysis of the power and energy demands on the APU/Hydraulic/Actuator Subsystem for space shuttle during the entry-to-touchdown (not including rollout) flight regime. These developments are given in the form of two subroutines which were written for use with the Space Shuttle Functional Simulator. The first subroutine calculates the power and energy demand on each of the three hydraulic systems due to control surface (inboard/outboard elevons, rudder, speedbrake, and body flap) activity. The second subroutine incorporates the R. I. priority rate limiting logic which limits control surface deflection rates as a function of the number of failed hydraulic. Typical results of this analysis are included, and listings of the subroutines are presented in appendicies.
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A digital computer simulation and study of a direct-energy-transfer power-conditioning system
An investigation of the behavior of the power-conditioning system as a whole is a necessity to ensure the integrity of the aggregate system in the case of space applications. An approach for conducting such an investigation is considered. A description is given of the application of a general digital analog simulator program to the study of an aggregate power-conditioning system which is being developed for use on the International Ultraviolet Explorer spacecraft. The function of the direct energy transfer system studied involves a coupling of a solar array through a main distribution bus to the spacecraft electrical loads.
Burns, W. W., III↗
Computer simulations of planetary accretion dynamics: Sensitivity to initial conditions
The implications and limitations of program ACRETE were tested. The program is a scheme based on Newtonian physics and accretion with unit sticking efficiency, devised to simulate the origin of the planets. The dependence of the results on a variety of radial and vertical density distribution laws, the ratio of gas to dust in the solar nebula, the total nebular mass, and the orbital eccentricity of the accreting grains was explored. Only for a small subset of conceivable cases are planetary systems closely like our own generated. Many models have tendencies towards one of two preferred configurations: multiple star systems, or planetary systems in which Jovian planets either have substantially smaller masses than in our system or are absent altogether. But for a wide range of cases recognizable planetary systems are generated - ranging from multiple star systems with accompanying planets, to systems with Jovian planets at several hundred AU, to single stars surrounded only by asteroids.
Isaacman, R.↗
A computer simulation of the afterburning processes occurring within solid rocket motor plumes in the troposphere
As part of a continuing study of the environmental effects of solid rocket motor (SRM) operations in the troposphere, a numerical model was used to simulate the afterburning processes occurring in solid rocket motor plumes and to predict the quantities of potentially harmful chemical species which are created. The calculations include the effects of finite-rate chemistry and turbulent mixing. It is found that the amount of NO produced is much less than the amount of HCl present in the plume, that chlorine will appear predominantly in the form of HCl although some molecular chlorine is present, and that combustion is complete as is evident from the predominance of carbon dioxide over carbon monoxide.
Gomberg, R. I.↗
Computer simulation of the velocity diffusion of cosmic rays
Monte Carlo simulation experiments were performed in order to study the velocity diffusion of charged particles in a static turbulent magnetic field. By following orbits of particles moving in a large ensemble of random magnetic field realizations with suitable chosen statistical properties, a pitch-angle diffusion coefficient is derived. Results are presented for a variety of particle rigidities and rms random field strengths and compared with the predictions of standard quasi-linear theory and the nonlinear partially averaged field theory.
Kaiser, T. B.↗
Quantum chemical calculations of interatomic potentials for computer simulation of solids
A comprehensive mathematical model by which the collective behavior of a very large number of atoms within a metal or alloy can accurately be simulated was developed. Work was done in order to predict and modify the strength of materials to suit our technological needs. The method developed is useful in studying atomic interactions related to dislocation motion and crack extension.
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The computer simulation of automobile use patterns for defining battery requirements for electric cars
The modeling process of a complex system, based on the calculation and optimization of the system parameters, is complicated in that some parameters can be expressed only as probability distributions. In the present paper, a Monte Carlo technique was used to determine the daily range requirements of an electric road vehicle in the United States from probability distributions of trip lengths, frequencies, and average annual mileage data. The analysis shows that a daily range of 82 miles meets to 95% of the car-owner requirements at all times with the exception of long vacation trips. Further, it is shown that the requirement of a daily range of 82 miles can be met by a (intermediate-level) battery technology characterized by an energy density of 30 to 50 Watt-hours per pound. Candidate batteries in this class are nickel-zinc, nickel-iron, and iron-air. These results imply that long-term research goals for battery systems should be focused on lower cost and longer service life, rather than on higher energy densities
Schwartz, H.-J.↗
Computer simulation of concentrated solid solution strengthening
The interaction forces between a straight edge dislocation moving through a three-dimensional block containing a random array of solute atoms were determined. The yield stress at 0 K was obtained by determining the average maximum solute-dislocation interaction force that is encountered by edge dislocation, and an expression relating the yield stress to the length of the dislocation and the solute concentration is provided. The magnitude of the solid solution strengthening due to solute atoms can be determined directly from the numerical results, provided the dislocation line length that moves as a unit is specified.
Kuo, C. T. K.↗
Computer simulation of the motion of a straight dislocation line in concentrated solid solutions. II
An investigation was undertaken to determine if the size and modulus interaction of a solute atom with a screw dislocation and the modulus interaction with an edge dislocation contributed to strengthening, in addition to the size interaction with an edge dislocation. The results indicate that the size interaction between solute atom and an edge dislocation accounts for most of the solid solution strengthening in f.c.c. alloys. The contribution to the yield stress from the modulus interaction with an edge dislocation is less than 15%. The interaction between a solute atom and a screw dislocation is much less than that between a solute atom and an edge dislocation.
Kuo, C. T. K.↗
The dynamics and control of large flexible space structures. Part B: Development of continuum model and computer simulation
The equations of motion of an arbitrary flexible body in orbit were derived. The model includes the effects of gravity with all its higher harmonics. As a specific example, the motion of a long, slender, uniform beam in circular orbit was modelled. The example considers both the inplane and three dimensional motion of the beam in orbit. In the case of planar motion with only flexible vibrations, the pitch motion is not influenced by the elastic motion of the beam. For large values of the square of the ratio of the structural modal frequency to the orbital angular rate the elastic motion was decoupled from the pitch motion. However, for small values of the ratio and small amplitude pitch motion, the elastic motion was governed by a Hill's 3 term equation. Numerical simulation of the equation indicates the possibilities of instability for very low values of the square of the ratio of the modal frequency to the orbit angular rate. Also numerical simulations of the first order nonlinear equations of motion for a long flexible beam in orbit were performed. The effect of varying the initial conditions and the number of modes was demonstrated.
Bainum, P. M.↗
Computer simulation of the velocity diffusion of cosmic rays
Monte Carlo simulation experiments have been performed in order to study the velocity diffusion of charged particles in a static turbulent magnetic field. By following orbits of particles moving in a large ensemble of random magnetic field realizations with suitably chosen statistical properties, a pitch-angle diffusion coefficient is derived. Results are presented for a variety of particle rigidities and rms random field strengths and compared with the predictions of standard quasi-linear theory and the nonlinear partially averaged field theory.
Kaiser, T. B.↗
Mapping ocean tides with satellites - A computer simulation
As a preliminary study for the future worldwide direct mapping of the open ocean tide with satellites equipped with precision altimeters we conducted a simulated study using sets of artificially generated altimeter data constructed from a realistic geoid and four pairs of major tides in the northeastern Pacific Ocean. Recovery of the original geoid and eight tidal maps is accomplished by a space-time, least squares harmonic analysis scheme. The resultant maps appear fairly satisfactory even when random noises up to + or - 100 cm are added to the altimeter data of sufficient space-time density. The method also produces a refined geoid which is rigorously corrected for the dynamic tides.
Won, I. J.↗
Computer simulation of engine systems
The use of computerized simulations of the steady state and transient performance of jet engines throughout the flight regime is discussed. In addition, installation effects on thrust and specific fuel consumption is accounted for as well as engine weight, dimensions and cost. The availability throughout the government and industry of analytical methods for calculating these quantities are pointed out.
Fishbach, L. H.↗
Performance evaluation of telecommunication systems using computer simulation
The SYSTID time domain digital simulation technique is reviewed. A technique is illustrated which estimates the signal to noise ratio at a point in the simulation of a communication system. Signals having a lowpass or bandpass spectra are utilized. Simulation results show the technique to be accurate over a wide range of signal to noise ratios. Examples which illustrate application to both analog and digital communication systems are provided.
Tranter, W. H.↗
Computer simulation of engine systems
The paper discusses the availability throughout the government and industry of analytical methods for calculating both the steady state and transient performance of an aircraft engine during an entire flight regime. The historical development of some of the analytical tools capable of evaluating installation effects on engine performance is traced and their present status is described.
Fishbach, L. H.↗