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Results for “SIMULATION METHODS”

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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1968

Methods of simulating weightlessness.

Weightlessness simulation, discussing mechanics of biological effects, simulation of specific anticipated effects and concept of mechanical acceleration and gravity equivalent effects

Bengele, H.↗
NASA NTRS1978

A method motion simulator design based on modeling characteristics of the human operator

A design criteria is obtained to compare two simulators and evaluate their equivalence or credibility. In the subsequent analysis the comparison of two simulators can be considered as the same problem as the comparison of a real world situation and a simulation's representation of this real world situation. The design criteria developed involves modeling of the human operator and defining simple parameters to describe his behavior in the simulator and in the real world situation. In the process of obtaining human operator parameters to define characteristics to evaluate simulators, measures are also obtained on these human operator characteristics which can be used to describe the human as an information processor and controller. First, a study is conducted on the simulator design problem in such a manner that this modeling approach can be used to develop a criteria for the comparison of two simulators.

Repperger, D. W.↗
NASA NTRS1982

Refined Monte Carlo method for simulating angle-dependent partial frequency redistributions

A refined algorithm for generating emission frequencies from angle-dependent partial frequency redistribution functions R sub II and R sub III is described. The improved algorithm has as its basis a 'rejection' technique that, for absorption frequencies x less than 5, involves no approximations. The resulting procedure is found to be essential for effective studies of radiative transfer in optically thick or temperature varying media involving angle-dependent partial frequency redistributions.

Lee, J.-S.↗
NASA NTRS1984

A method for simulating 3-D aircraft flow fields with jet plume effects

The objective is to develop, demonstrate, and document a coupled flow analysis procedure for computing 3D aircraft flow fields with deflected subsonic and supersonic jet exhaust plumes. The PNS plume code was transferred to the Ames computer facility for execution on the Cray computer. No problems were encountered when installing this code. The Bower's test case is currently being run. This case is being used to fine tune the procedure for coupling the plume code to PANAIR.

Source record↗
NASA NTRS1985

Scattering Models and Basic Experiments in the Microwave Regime

The objectives of research over the next three years are: (1) to develop a randomly rough surface scattering model which is applicable over the entire frequency band; (2) to develop a computer simulation method and algorithm to simulate scattering from known randomly rough surfaces, Z(x,y); (3) to design and perform laboratory experiments to study geometric and physical target parameters of an inhomogeneous layer; (4) to develop scattering models for an inhomogeneous layer which accounts for near field interaction and multiple scattering in both the coherent and the incoherent scattering components; and (5) a comparison between theoretical models and measurements or numerical simulation.

Fung, A. K.↗
NASA NTRS1991

Thoughts on the chimera method of simulation of three-dimensional viscous flow

The chimera overset grid is reviewed and discussed relative to other procedures for simulating flow about complex configurations. It is argued that while more refinement of the technique is needed, current schemes are competitive to unstructured grid schemes and should ultimately prove more useful.

Steger, Joseph L.↗
NASA NTRS1991

Propellant-remaining modeling

A successful satellite mission is predicted upon the proper maintenance of the spacecraft's orbit and attitude. One requirement for planning and predicting the orbit and attitude is the accurate estimation of the propellant remaining onboard the spacecraft. Focuss is on the three methods that were developed for calculating the propellant budget: the errors associated with each method and the uncertainties in the variables required to determine the propellant remaining that contribute to these errors. Based on these findings, a strategy is developed for improved propellant-remaining estimation. The first method is based on Boyle's law, which related the values of pressure, volume, and temperature (PVT) of an ideal gas. The PVT method is used for the monopropellant and the bipropellant engines. The second method is based on the engine performance tests, which provide data that relate thrust and specific impulse associated with a propellant tank to that tank's pressure. Two curves representing thrust and specific impulse as functions of pressure are then generated using a polynomial fit on the engine performance data. The third method involves a computer simulation of the propellant system. The propellant flow is modeled by creating a conceptual model of the propulsion system configuration, taking into account such factors as the propellant and pressurant tank characteristics, thruster functionality, and piping layout. Finally, a thrust calibration technique is presented that uses differential correction with the computer simulation method of propellant-remaining modeling. Thrust calibration provides a better assessment of thruster performance and therefore enables a more accurate estimation of propellant consumed during a given maneuver.

Torgovitsky, S.↗
NASA NTRS1993

A new method to simulate vertical and horizontal structure in galactic disks

We have modified the particles in an N-body treecode to have different softening lengths in the horizontal and vertical directions. This allows us to simultaneously have thin enough particles to resolve the vertical structure in galactic disks, and horizontally large enough particles to suppress the vertical heating due to two-body effects.

Dalcanton, Julianne J.↗
NASA NTRS1958

A method for simulating the atmospheric entry of long-range ballistic missiles

It is demonstrated with the aid of similitude arguments that a model launched from a hypervelocity gun upstream through a special supersonic nozzle should experience aerodynamic heating and resulting thermal stresses like those encountered by a long-range ballistic missile entering the earth's atmosphere. This demonstration hinges on the requirements that model and missile be geometrically similar and made of the same material, and that they have the same flight speed and Reynolds number (based on conditions just outside the boundary layer) at corresponding points in their trajectories. The hypervelocity gun provides the model with the required initial speed, while the nozzle scales the atmosphere, in terms of density variation, to provide the model with speeds and Reynolds numbers over its entire trajectory. Since both the motion and aerodynamic heating of a missile tend to be simulated in the model tests, this combination of hypervelocity gun and supersonic nozzle is termed an atmosphere entry simulator.

Eggers, A J , Jr↗
NASA NTRS2002

FFT-based methods for simulating flicker FM

Four algorithms for simulating flicker FM phase noise are given, two old and two new. Their Allan deviation and mean square time interval error (MSTIE) are examined.

flicker noise simulation phase noise↗