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Results for “ELASTIC COLLISION”

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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Examination of the collision force method for analyzing the responses of simple containment/deflection structures to impact by one engine rotor blade fragment

An approximate collision analysis, termed the collision-force method, was developed for studying impact-interaction of an engine rotor blade fragment with an initially circular containment ring. This collision analysis utilizes basic mass, material property, geometry, and pre-impact velocity information for the fragment, together with any one of three postulated patterns of blade deformation behavior: (1) the elastic straight blade model, (2) the elastic-plastic straight shortening blade model, and (3) the elastic-plastic curling blade model. The collision-induced forces are used to predict the resulting motions of both the blade fragment and the containment ring. Containment ring transient responses are predicted by a finite element computer code which accommodates the large deformation, elastic-plastic planar deformation behavior of simple structures such as beams and/or rings. The effects of varying the values of certain parameters in each blade-behavior model were studied. Comparisons of predictions with experimental data indicate that of the three postulated blade-behavior models, the elastic-plastic curling blade model appears to be the most plausible and satisfactory for predicting the impact-induced motions of a ductile engine rotor blade and a containment ring against which the blade impacts.

Zirin, R. M.↗
NASA NTRS1991

Studies of electron collisions with polyatomic molecules using distributed-memory parallel computers

Elastic electron scattering cross sections from 5-30 eV are reported for the molecules C2H4, C2H6, C3H8, Si2H6, and GeH4, obtained using an implementation of the Schwinger multichannel method for distributed-memory parallel computer architectures. These results, obtained within the static-exchange approximation, are in generally good agreement with the available experimental data. These calculations demonstrate the potential of highly parallel computation in the study of collisions between low-energy electrons and polyatomic gases. The computational methodology discussed is also directly applicable to the calculation of elastic cross sections at higher levels of approximation (target polarization) and of electronic excitation cross sections.

Winstead, C.↗
NASA NTRS1972

Perturbation of the Maxwellian distribution in chemically reacting gas mixtures

Chemically reacting gas mixtures are considered for the case in which inelastic collisions occur significantly less frequently than elastic ones. The first approximation of the general solution of the Boltzmann equation is developed and is shown to contain an additional scaler term. The concentration, the mean mass velocity, and the temperature of the mixture are determined and the rate of reaction in the first approximation is formulated. Tables are presented which give reaction rate values obtained by both the first and second approximation for different activation energies. The tables show that the first approximation is sufficient for practical purposes for calculating the reaction rate.

Alekseyev, B. V.↗
NASA NTRS1976

Electron detachment from negative ions - The effects of isotopic substitution

Absolute total electron-detachment cross sections and relative elastic-scattering cross sections are presented for collisions of H(-) or D(-) with He, Ne, Ar, and N2 for collision energies ranging from about 2 eV up to 100 eV. Special emphasis has been given to the effect of isotopic substitution. It was found that, with the exception of the helium target, the results cannot be in accord with a model using a localized complex potential. On the other hand, the results for H(-) or D(-) with He are in excellent agreement with predictions based on previous (local complex potential) analysis of differential elastic-scattering measurements.

Champion, R. L.↗
NASA NTRS1985

Differential scattering cross sections for collisions of 0.5-, 1.5-, and 5.0-keV helium atoms with He, H2, N2, and O2

This paper reports the first results of an experimental program established to provide cross section data for use in modeling various atmospheric processes. Absolute cross sections, differential in the scattering angle, have been measured for collisions of 0.5-, 1.5-, and 5.0-keV helium atoms with He, H2, N2, and O2 at laboratory scattering angles between 0.1 deg and 5 deg. The results are the sums of cross sections for elastic and inelastic scattering of helium atoms; charged collision products are not detected. Integration of the differential cross section data yields integral cross sections consistent with measurements by other workers. The apparatus employs a position-sensitive detector for both primary and scattered particles and uses a short target cell with a large exit aperture to ensure a simple and well-defined apparatus geometry.

Newman, J. H.↗
NASA NTRS1974

Annihilation during positron-hydrogen collisions

Using the precision s- and p-wave elastic-scattering wave functions obtained previously, we have calculated the annihilation rate for positrons colliding with hydrogen atoms below the positronium-formation threshold. The s-wave results agree well with those of Humberston, while the p-wave results, which are new, contribute about 20% of the total at the higher energies.

Bhatia, A. K.↗
NASA NTRS1993

Total electron scattering and electronic state excitations cross sections for O2, CO, and CH4

Available electron collision cross section data concerning total and elastic scattering, vibrational excitation, and ionization for O2, CO, and CH4 have been critically reviewed, and a set of cross sections for modeling of planetary atmospheric behavior is recommended. Utilizing these recommended cross sections, we derived total electronic state excitation cross sections and upper limits for dissociation cross sections, which in the case of CH4 should very closely equal the actual dissociation cross section.

Kanik, I.↗
NASA NTRS1993

Total Electron Scattering and Electronic State Excitations Cross Sections for O_2, CO, and CH_4

Available electron collision cross section data concerning total and elastic scattering, vibrationalexcitation, and ionization for O_2, CO, and CH_4 have been critically reviewed, and a set of crosssections for modeling of planetary atmospheric behavior is recommended. Utilizing theserecommended cross sections, we derived total electronic state excitation cross sections and upperlimits for dissociation cross sections, which in the case of CH_4 should very closely equal the actualdissociation cross section.

Kanik, I.↗
NASA NTRS2022

Design, Control, and Simulation of Tensegrity Based Kites

Due to lowering price and increased functionality, the future could bring in a huge number of UAVs flying in urban areas. In order to safely accommodate them, they should be fundamentally safe to fly. Unfortunately, current rigid designs could cause significant damage in case of a crash. To mitigate this problem, this report proposes constructing soft UAVs using tensegrity structures in order to mitigate the impact of collisions, effectively improving the safety of the vehicles and increasing public confidence in the use of UAVs. In this paradigm, the frame of the vehicle is designed using a tensegrity structure, a geometric structure composed of suspended elements of pure compression and pure tension, which during a collision can better absorb high stresses through elastic deformation. As a feasibility study we test this concept on an actuated tensegrity kite in a custom physics simulator, designed to simulate tensegrity structures with non-rigid rods, along with basic simulations of lift. Results show that this concept is feasible and that the kite can change orientation by actively changing the shape of the tensegrity structure.

Tensegrity↗
NASA NTRS1975

Rotational excitation in H2-H2 collisions - Close-coupling calculations

Rotational excitation in molecule-molecule collisions has been treated for the first time by accurate quantum close-coupling scattering calculations, employing an expansion basis set of two to three rotational levels for each molecule and correctly accounting for exchange of identical particles. Elastic and inelastic cross sections have been computed for collisions of para-para, ortho-ortho, and para-ortho hydrogen molecules assuming an intermolecular potential suggested previously. The accuracy of recent 'effective potential' calculations is demonstrated by comparison with the exact quantum results.

Green, S.↗
NASA NTRS1972

Use of the Glauber approximation in atomic collisions - A progress report.

Recent progress in the use of the Glauber (1970) theory for estimating atomic collision cross sections is reviewed. It appears that the Glauber approximation is reliable for electron-hydrogen elastic scattering and excitation at incident energies exceeding 30 eV. For more complicated atomic collisions, the usefulness of the Glauber approximation has not yet been significantly tested.

Gerjuoy, E.↗