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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Mode coupling and wave particle interactions for unstable ion acoustic waves

A theory for the spatial development of linearly unstable, coupled waves is presented in which both quasi-linear and mode coupling effects are treated in a self-consistent manner. Steady state excitation of two waves is assumed at the boundary x = 0, the plasma being homogeneous in the y and z directions. Coupled equations are derived for the x dependence of the amplitudes of the primary waves and the secondary waves, correct through second order terms in the wave amplitude, but without usual approximation of small growth rates. This general formalism is then applied to the case of coupled ion acoustic waves driven unstable by an ion beam streaming in the direction of the x axis. If the modifications of the ion beam by the waves (quasi-linear effects) are ignored, explosive instabilities (singularities in all of the amplitudes at finite x) are found, even when all of the waves have positive energy. If these wave-particle interactions are included, the solutions are no longer singular, and all of the amplitudes have finite maxima.

Martin, P.↗
NASA NTRS2008

Recent Progress in the Development of a Multi-Layer Green's Function Code for Ion Beam Transport

To meet the challenge of future deep space programs, an accurate and efficient engineering code for analyzing the shielding requirements against high-energy galactic heavy radiation is needed. To address this need, a new Green's function code capable of simulating high charge and energy ions with either laboratory or space boundary conditions is currently under development. The computational model consists of combinations of physical perturbation expansions based on the scales of atomic interaction, multiple scattering, and nuclear reactive processes with use of the Neumann-asymptotic expansions with non-perturbative corrections. The code contains energy loss due to straggling, nuclear attenuation, nuclear fragmentation with energy dispersion and downshifts. Previous reports show that the new code accurately models the transport of ion beams through a single slab of material. Current research efforts are focused on enabling the code to handle multiple layers of material and the present paper reports on progress made towards that end.

Tweed, John↗
NASA NTRS1997

Measurements of momentum transfer coefficients for H2, N2, CO and CO2 incident upon spacecraft surfaces

Measurements of momentum transfer coefficients were made for gas-surface interactions between the Space Shuttle reaction control jet plume gases and the solar panel array materials to be used on the International Space Station. Actual conditions were simulated using a supersonic nozzle source to produce beams of the gases with approximately the same average velocities as the gases have in the Shuttle plumes. Samples of the actual solar panel materials were mounted on a torsion balance that was used to measure the force exerted on the surfaces by the molecular beams. Measurements were made with H2, N2, CO, and CO2 incident upon the solar array material, Kapton, SiO2-coated Kapton, and Z93-coated Al. The measurements showed that molecules scatter from the surfaces more specularly as the angle of incidence increases and that scattering behavior has a strong dependence upon both the incident gas and velocity. These results show that for some technical surfaces the simple assumption of diffuse scattering with complete thermal accommodation is entirely inadequate. It is clear that additional measurements are required to produce models that more accurately describe the gas-surface interactions encountered in rarefied flow regimes.

Cook, S. R.↗
NASA NTRS1997

Measurement of Momentum Transfer Coefficients for H2, N2, CO, and CO2 Incident Upon Spacecraft Surfaces

Measurements of momentum transfer coefficients were made for gas-surface interactions between the Space Shuttle reaction control jet plume gases and the solar panel array materials to be used on the International Space Station. Actual conditions were simulated using a supersonic nozzle source to produce beams of the gases with approximately the same average velocities as the gases have in the Shuttle plumes. Samples of the actual solar panel materials were mounted on a torsion balance that was used to measure the force exerted on the surfaces by the molecular beams. Measurements were made with H2, N2, CO, and CO2 incident upon the solar array material, Kapton, SiO2-coated Kapton, and Z93-coated Al. The measurements showed that molecules scatter from the surfaces more specularly as the angle of incidence increases and that the scattering behavior has a strong dependence upon both the incident gas and velocity. These results show that for some technical surfaces the simple assumption of diffuse scattering with complete thermal accommodation is entirely inadequate. It is clear that additional measurements are required to produce models that more accurately describe the gas-surface interactions encountered in rarefied flow regimes.

Cook, Steven R.↗
NASA NTRS1984

The (20)Ne interaction in extended matter

Although heavy ion transport theory is developed to a relatively advanced stage, the present limitation in biomedical and electronic applications is the uncertainty in nuclear fragmentation parameters. The present status on Ne-20 beams is discussed and useful formulae are presented for future use in analysis of beam transport experiments.

Wilson, J. W.↗
NASA NTRS1972

Sky-wave backscatter - A means for observing our environment at great distances.

During the last five years, much progress has been made in the understanding of sky-wave backscatter. An explanation of the various interacting phenomena is presented, as is a review of the current state of knowledge reflecting recent advances in observational methods and analytic techniques. New narrow-beam antennas, coupled with signal modulations that permit fine resolution in time delay, are beginning to yield information concerning the character of the scatterers, which now can be separately discerned. These narrow beams also permit study of polarization fading from small regions, and this shows promise as a means for learning the distant sea state. Doppler shifts of a fraction of a hertz on signals of tens of megahertz are separable, permitting isolation of sea returns from ground returns by virtue of the Doppler effect resulting from sea-wave speed; this also suggests a potential sea-monitoring principle. Despite these advances, there is little practical application of sky-wave backscatter as a means of environmental monitoring. This lack is attributed to the large remaining gaps in our understanding of the echoes and our inability to interpret the forms of data that can be acquired with equipment of reasonable cost.

Croft, T. A.↗
NASA NTRS1974

High speed hydrogen/graphite interaction

Various aspects of a research program on high speed hydrogen/graphite interaction are presented. Major areas discussed are: (1) theoretical predictions of hydrogen/graphite erosion rates; (2) high temperature, nonequilibrium hydrogen flow in a nozzle; and (3) molecular beam studies of hydrogen/graphite erosion.

Kelly, A. J.↗
NASA NTRS1975

Charge-exchange plasma generated by an ion thruster

The use of high voltage solar arrays greatly reduces or eliminates power processing requirements in space electric propulsion systems. This use also requires substantial areas of solar array to be at high positive potential relative to space and most of the spacecraft. The charge exchange plasma conducts electrons from the ion beam to such positive surfaces, and thereby electrically load the high voltage solar array. To evaluate this problem, the charge-exchange plasma generated by an ion beam was investigated experimentally. Based upon the experimental data, a simple model was derived for the charge-exchange plasma. This model is conservative in the sense that both the electron/ion density and the electron current density should be equal to, or less than, the preducted value for all directions in the hemisphere upstream of the ion beam direction. Increasing the distance between a positive potential surface (such as a high voltage solar array) and the thruster is the simplest way to control interactions. Both densities and currents vary as the inverse square of this distance.

Kaufman, H. R.↗
NASA NTRS1979

Characterization of graphite/epoxy laminates for aeroelastic tailoring

A study of interaction between wing bending and twist by graphite/epoxy anisotropic laminates used in aircraft wing skins is presented. The laminates were used as covers for subscale box beams supported as a cantilever and tested in tip shear and tip torque, measuring beam response with a reflected light technique. The results indicated that the in-plane stiffness properties of anisotropic laminates can be predicted if the layer properties of the composite materials are known; thus, the coupled bending/twist response of wing type structures made from these laminates can be determined provided the limits of the laminate linear behavior are not significantly exceeded.

Shyprykevich, P.↗
NASA NTRS1986

Quadrupole mass spectrometer for Space Shuttle applications - Flight capabilities and ground calibration

The AFGL Quadrupole Ion/Neutral Mass Spectrometer (QINMS), its flight capabilities, and a few examples of QINMS data from the STS-4 flight are discussed in addition to the beam facility and calibration procedures used at the Los Alamos National Laboratory facility. A 5-eV atomic oxygen beam is produced using a continuous optical discharge technique, and the resulting pumped beam has sufficient high flux and velocity to simulate orbital conditions. The calibrated instrument will be used in the NASA Johnson Space Center Evaluation of Oxygen Interactions with Materials experiment to measure the density of ambient oxygen and to identify the products of oxygen-surface reactions.

Hunton, D. E.↗
NASA NTRS1987

Dynamics of spacecraft control laboratory experiment (SCOLE) slew maneuvers

This is the first of two reports on the dynamics and control of slewing maneuvers of the NASA Spacecraft Control Laboratory Experiment (SCOLE). In this report, the dynamics of slewing maneuvers of SCOLE are developed in terms of an arbitrary maneuver about any given axis. The set of dynamical equations incorporate rigid-body slew maneuver and three-dimensional vibrations of the complete assembly comprising the rigid shuttle, the flexible beam, and the reflector with an offset mass. The analysis also includes kinematic nonlinearities of the entire assembly during the maneuver and the dynamics of the interaction between the rigid shuttle and the flexible appendage. The final set of dynamical equations obtained for slewing maneuvers is highly nonlinear and coupled in terms of the flexible modes and the rigid-body modes. The equations are further simplified and evaluated numerically to include the first ten flexible modes and the SCOLE data to yield a model for designing control systems to perform slew maneuvers.

Kakad, Y. P.↗
NASA NTRS1992

Slew maneuvers of Spacecraft Control Laboratory Experiment (SCOLE)

This is the final report on the dynamics and control of slew maneuvers of the Spacecraft Control Laboratory Experiment (SCOLE) test facility. The report documents the basic dynamical equation derivations for an arbitrary large angle slew maneuver as well as the basic decentralized slew maneuver control algorithm. The set of dynamical equations incorporate rigid body slew maneuver and three dimensional vibrations of the complete assembly comprising the rigid shuttle, the flexible beam, and the reflector with an offset mass. The analysis also includes kinematic nonlinearities of the entire assembly during the maneuver and the dynamics of the interactions between the rigid shuttle and the flexible appendage. The equations are simplified and evaluated numerically to include the first ten flexible modes to yield a model for designing control systems to perform slew maneuvers. The control problem incorporates the nonlinear dynamical equations and is expressed in terms of a two point boundary value problem.

Kakad, Yogendra P.↗
NASA NTRSDate not supplied

Indigenous Organic Matter Associated with Unusual Low Temperature Aqueous Secondary Phases in the Mars Meteorite Nakhla

In freshly fractured chips of the Mars meteorite Nakhla, we found carbonaceous phases intimately associated with secondary aqueous alteration phases, both mineral and amorphous, interpreted to have formed through the low-temperature, mineral-water dissolution of the host Martian basalt.We have characterized the nature of carbonaceous matter and spatially associated secondary phases within Nakhla using a multidisciplinary suite of optical and electron beam instrumentation(Thomas-Keprta et al., 2022). Secondary Phases: The preserved secondary mineral phases are best described as ‘juvenile’ hydrated amorphous silica formed when water interacts with mafic rocks. Although amorphous silica on Earth rarely persists through geologic time due to alteration into other phases, e.g.,microcrystalline opal-CT and eventually quartz, the lack of maturation of primarily amorphous silica with embedded nano phase ferrihydrite in Nakhla infers these phases formed in a limited water environment by low temperature, circumneutral pH fluids stabilized by the presence of coexisting amorphous silica.Additionally, we report the presence of the ferrous hydroxycarbonate mineral chukanovite (Fe2(OH)2CO3)within some of the secondary mineral aggregates studied. Organic Matter:Indigenous Nakhla carbonaceous matter is present both in condensed phases and in a dispersed state spatially associated with secondary alteration phases. In the former, discrete refractory micron to submicron assemblages were identified that appear macromolecular in nature and, in several cases, associated with F and, in one case, significant N. While organically bound Fhas yet to be detected remotely on Mars, the identification of organic N within one of the carbonaceous phases is considered a prerequisite for Martian astrobiological potential. Summary: Neither the intimate association of carbonaceous matter with secondary phases nor the identification of chukanovite have been previously reported in any of the Martian meteorites.A variety of habitability-related metastable solid-phase, oxidation-reduction, and organic-molecular sample attributes in Nakhla formed hundreds of millions of years ago near Mars’ surface; these alteration products persisted on Mars until very recentlyand resemble the amorphous materials observed at Gale crater by Mars Science Laboratory CuriosityRover (Rampe et al., 2020).Similar phases may be expected to occur elsewhere on Mars (e.g., Jezerocrater). References: Rampe E. B. et al.(2020) Mineralogy and geochemistry of sedimentary rocks and eolian sediments in Gale crater, Mars: A review after six Earth years of exploration with Curiosity.Geochemistry80, 125605; Thomas-Keprta K.L. et al. (2022) Indigenous carbon-rich matter associated with unusual aqueous alteration features in Nakhla: Complex formation and preservation history. Geochim. et Cosmochim. Acta320, 41-78 (online).

Mars meteorite↗
NASA NTRS2016

Dislocation Content Measured Via 3D HR-EBSD Near a Grain Boundary in an AlCu Oligocrystal

Interactions between dislocations and grain boundaries are poorly understood and crucial to mesoscale plasticity modeling. Much of our understanding of dislocation-grain boundary interaction comes from atomistic simulations and TEM studies, both of which are extremely limited in scale. High angular resolution EBSD-based continuum dislocation microscopy provides a way of measuring dislocation activity at length scales and accuracies relevant to crystal plasticity, but it is limited as a two-dimensional technique, meaning the character of the grain boundary and the complete dislocation activity is difficult to recover. However, the commercialization of plasma FIB dual-beam microscopes have made 3D EBSD studies all the more feasible. The objective of this work is to apply high angular resolution cross correlation EBSD to a 3D EBSD data set collected by serial sectioning in a FIB to characterize dislocation interaction with a grain boundary. Three dimensional high angular resolution cross correlation EBSD analysis was applied to an AlCu oligocrystal to measure dislocation densities around a grain boundary. Distortion derivatives associated with the plasma FIB serial sectioning were higher than expected, possibly due to geometric uncertainty between layers. Future work will focus on mitigating the geometric uncertainty and examining more regions of interest along the grain boundary to glean information on dislocation-grain boundary interaction.

Ruggles, Timothy↗
NASA NTRS1985

Laboratory studies of Kapton degradation in an oxygen ion beam

Results are presented from a preliminary laboratory investigation of the degradation of the widely used polyimide Kapton under oxygen ion bombardment. Recent space shuttle flights have shown that Kapton and some other materials exposed to the apparent ram flow of residual atmosphere (at orbital velocity in low Earth orbit) lose mass and change their optical properties. It was hypothesized that these changes are caused by chemical interaction with atomic oxygen, aided by the 5-eV impact energy of atmospheric oxygen atoms in the ram. The reaction rate under O(+) bombardment seemed to be independent of incident energy over a wide range of energies. Although the flux of thermal ions in this experiment was much greater than the accelerated flux, the observed Kapton degradation was limited to the beam area and ram flow direction. This is consistent with an activation energy above the thermal energies but well below the beam energies. The results reproduce well the material loss, optical changes, SEM surface structure, and ram directionality of the samples returned by the shuttle. These factors, along with the lack of degradation under argon ion bombardment, are convincing evidence for ram flow oxidation as the mechanism of degradation.

Ferguson, D. C.↗
NASA NTRS1971

The stopping rate of negative cosmic-ray muons near sea level

A production rate of 0.065 + or - 0.003 Ar-37 atom/kg min of K-39 at 2-mwe depth below sea level was measured by sweeping argon from potassium solutions. This rate is unaffected by surrounding the solution by paraffin and is attributed to negative muon captures and the electromagnetic interaction of fast muons, and not to nucleonic cosmic ray component. The Ar-37 yield from K-39 by the stopping of negative muons in a muon beam of a synchrocyclotron was measured to be 8.5 + or - 1.7%. The stopping rate of negative cosmic ray muons at 2-mwe depth below sea level from these measurements and an estimated 17% electromagnetic production is 0.63 + or - 0.13 muon(-)/kg min. Previous measurements on the muon stopping rate vary by a factor of 5. Our value is slightly higher but is consistent with two previous high values. The sensitivity of the Ar-37 radiochemical method for the detection of muons is considerably higher than that of the previous radiochemical methods and could be used to measure the negative muon capture rates at greater depths.

Spannagel, G.↗
NASA NTRS1974

A numerical-perturbation method for the nonlinear analysis of structural vibrations

A numerical-perturbation method is proposed for the determination of the nonlinear forced response of structural elements. Purely analytical techniques are capable of determining the response of structural elements having simple geometries and simple variations in thickness and properties, but they are not applicable to elements with complicated structure and boundaries. Numerical techniques are effective in determining the linear response of complicated structures, but they are not optimal for determining the nonlinear response of even simple elements when modal interactions take place due to the complicated nature of the response. Therefore, the optimum is a combined numerical and perturbation technique. The present technique is applied to beams with varying cross sections.

Nayfeh, A. H.↗
NASA NTRS1978

Momentum modulation of free electrons by laser light

Measurements have been made of the electron momentum modulation resulting from the inverse Cerenkov interaction with laser light. The experiment utilized 40-MeV particles and a 30-MW Nd:YAG laser. Results are given for the harmonic content of the electron beam as a function of distance along the z-axis, electron bunching for the ideal case, and electron current at the laser frequency normalized to the dc current as a function of distance along the z-axis.

Kimura, W. D.↗