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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Molecular rotation and reorientation - Microscopic and hydrodynamic contributions

The relative roles of microscopic and hydrodynamic contributions to molecular rotation and reorientation are examined within the framework of the microscopic boundary layer theory recently proposed by the authors. The theory is applied to rough spheres, for which computer simulation data are available and to experimental results on spherical top molecules. Attention is focused on rotational diffusion constants, the kappa parameter introduced by Kivelson et al., and orientational relaxation times. It is shown that, while collective effects are present and often nonnegligible, the motion of small molecules is dominated by its microscopic aspects. Experimental trends which can incorrectly suggest dominance by hydrodynamic contributions are discussed in some detail. Finally, the transition to the regime where collective effects are dominant is considered.

Hynes, J. T.↗
NASA NTRS1977

The multiple applications of electrons in space

An electron source such as a simple cathode is a cheap and light device which can serve several technological and scientific purposes in space: (1) electrostatic charging of a spacecraft can be limited by releasing electrons accumulated on the conductive elements of their surface; (2) the erosion of conductive coatings and the ability of conductive paints to withstand the space environment can be evaluated by monitoring the flow of charged particles impinging on their surface; (3) measuring the current collected by the spacecraft surface as a function of its potential with respect to an emitter is a very sensitive diagnostic technique which can yield a number of plasma parameters, such as density and temperature; (4) it is possible to convert the thermal motion of space plasmas into electrical energy by collecting energetic electrons and returning them to the medium as cold particles; (5) a wave in a plasma is characterized by a conduction current density which gives rise to fluctuations of the current flowing to the surface.

Grard, R. J. L.↗
NASA NTRS1980

Visualization of the laminar-turbulent transition in the flow over an airfoil using the smoke-wire technique

A flow visualization technique, referred to as the smoke-wire, was used for visualization of the transition of the free shear layer associated with the laminar separation bubble of a NACA 66 sub 3-018 airfoil section at low Reynolds number (50,000-130,000). The smoke-wire technique allows the introduction of fine smoke streaklines into the flow field through the electrical resistive heating of a very fine wire which has been coated with oil and which is located upstream from the leading edge of the airfoil section. Streakline data were collected using both high speed still and motion picture photography.

Batill, S. M.↗
NASA NTRS1990

Gradiometry coexperiments to the gravity probe B and step missions

The Gravity Probe-B (GP-B) spacecraft, designed to test predictions of general relativity, will fly in the mid 1990s. It will carry four electrostatically suspended gyroscopes in a cryogenic environment and will have a drag-free control system to minimize disturbances on the gyroscopes. The Stanford Test of Equivalence Principle (STEP) spacecraft, to fly later, will carry a set of test masses under very similar conditions. The possibility of using differential measurements of the GP-B gyroscopes suspension forces and the STEP tests mass displacement readout to form single-axis gravity gradiometers is explored. It is shown that the noise in the suspension systems is sufficiently small in the relevant frequency range, and that enough information is collected to compensate for the spacecrafts' attitude motion. Finally, using Breakwell's flat-earth approximation, these experiments are compared to other geodesy experiments and predict the contribution they can make to the knowledge of the Earth's geopotential.

Tapley, M.↗
NASA NTRS1992

The interstellar gas experiment

The Interstellar Gas Experiment (IGE) exposed thin metallic foils to collect neutral interstellar gas particles. These particles penetrate the solar system due to their motion relative to the sun. Thus, it is possible to entrap them in the collecting foils along with precipitating magnetospheric and perhaps some ambient atmospheric particles. For the entire duration of the Long Duration Exposure Facility (LDEF) mission, seven of these foils collected particles arriving from seven different directions as seen from the spacecraft. In the mass spectroscopic analysis of the noble gas component of these particles, we have detected the isotopes of He-3, He-4, Ne-20, and Ne-22. In the foil analyses carried out so far, we find a distribution of particle arrival directions which shows that a significant part of the trapped particles are indeed interstellar atoms. The analysis needed to subtract the competing fluxes of magnetospheric and atmospheric particles is still in progress.

Lind, D. L.↗
NASA NTRS1993

A residual flexibility approach to multibody dynamics

Many complex systems can be modeled as a collection of interacting bodies, where the relative motion of the bodies may be large. The dynamics of such systems are simulated using multibody dynamic formulations. Many of these treat each body as a rigid component, but recently the flexibility of the components has been incorporated. This paper presents a residual flexibility formulation of the multibody dynamics problem. The formulation is very simple and offers great computational efficiency since it treats each body as a free structure in space, interacting with other bodies only through interface forces. Each body's accelerations can be solved independently, as can each set of interface forces. We have applied the technique successfully to several special applications, and the initial implementation in a general mechanisms code has given excellent results in comparison to a direct finite element representation of flexibility.

Blelloch, Paul A.↗
NASA NTRS1993

Experimental technique to investigate the interstellar gas - Preliminary analysis

The Interstellar Gas Experiment (IGE) exposed thin metallic foils to collect neutral interstellar gas particles. These particles penetrate the solar system due to their motion relative to the sun. Thus, it was possible to entrap them in the collecting foils along with precipitating magnetospheric and perhaps some ambient atmospheric particles. For the entire duration of the Long Duration Exposure Facility mission, seven of these foils collected particles arriving from seven different directions as seen from the spacecraft. In the mass spectrometric analysis of the noble gas component of these particles, we have detected the isotopes of He-3, He-4, Ne-20, and Ne-22. In the foil analyses carried out so far, we find a distribution of particle arrival directions which shows that a significant part of the trapped particles are indeed interstellar atoms. The analysis needed to subtract the competing fluxes of magnetospheric and atmospheric particles is still in progress.

Lind, D. L.↗
NASA NTRS1998

A Review of Scientific and Technological Results from the TSS-1R Mission

The Tethered Satellite System (TSS) program was designed to provide a unique opportunity to explore certain space plasma-electrodynamic processes and the orbital mechanics of a gravity-gradient stabilized system of two satellites linked by a long conducting tether. A unique data set was obtained during deployment which has allowed significant science to be accomplished. This paper focuses on results from the TSS-1R mission that are most important to the future technological applications of electrodynamic tethers in space, in particular, the current collection process. Of particular significance is an apparent transition of the physics of current collection when the potential of the collecting body becomes greater than the ram energy of the ionospheric atomic oxygen ions. Previous theoretical models of current collection were electrostatic, assuming that the orbital motion of the system, which is highly subsonic with respect to electron thermal motion, was unimportant. This may still be acceptable for the case of relatively slow-moving sounding rockets. However, the TSS-1R results show that motion relative to the plasma must be accounted for in orbiting systems.

Stone, N. H.↗
NASA NTRS1998

The TSS-1R Electrodynamic Tether Experiment: Scientific and Technological Results

The bi-national, US-Italian, Tethered Satellite System (TSS) program was designed to provide a unique opportunity to explore certain space plasma- electrodynamic processes and the orbital mechanics of a gravity-gradient stabilized system of two satellites linked by a long conducting tether. The second flight, TSS-LR, was launched February 22, 1996 on STS-75 and satellite deployment began at MET 3/00:27. A unique data set was obtained over the next five hours, as the tether was deployed to a length of 19695 meters, which has allowed significant science to be accomplished. This presentation will focus on electrodynamic processes generated by the tether--in particular, the collection of electrical current from the ionospheric plasma. Of particular significance is an apparent transition of the physics of current collection when the potential of the collecting body becomes greater than the ram energy of the ionospheric atomic oxygen ions. Previous theoretical models of current collection were electrostatic--assuming that the orbital motion of the system, which is highly subsonic with respect to electron thermal motion, was un- important. This may still be acceptable for the case of relatively slow-moving sounding rockets. However, the TSS-LR results show that motion relative to the plasma must be accounted for in orbiting systems.

Stone, Nobie H.↗
NASA NTRS1982

A functional video-based anthropometric measuring system

A high-speed anthropometric three dimensional measurement system using the Selcom Selspot motion tracking instrument for visual data acquisition is discussed. A three-dimensional scanning system was created which collects video, audio, and performance data on a single standard video cassette recorder. Recording rates of 1 megabit per second for periods of up to two hours are possible with the system design. A high-speed off-the-shelf motion analysis system for collecting optical information as used. The video recording adapter (VRA) is interfaced to the Selspot data acquisition system.

Nixon, J. H.↗
NASA NTRS1992

Determination of orbits of comets: P/Kearns-Kwee, P/Gunn, including nongravitational effects in the comets' motion

To improve the orbits, all the positional observations of the comets were collected. The observations were selected and weighted according to objective mathematical criteria and the mean residuals a priori were calculated for both comets. We took into account nongravitational effects in the comets' motion using Marsden's method applied in two ways: either determining the three constant parameters, A(sub 1), A(sub 2), A(sub 3) or the four parameters A, eta, I, phi connected with the rotating nucleus of the comet. To link successfully all the observations, we had to assume for both comets that A(t) = A(sub O)exp(-B x t) where B was an additional nongravitational parameter.

Todorovic-Juchniewicz, Bozenna↗
NASA NTRS1985

Stimulus specificity and individual stereotypy of autonomic responses to motion stressors

Motion sickness research shows a lack of agreement regarding the contribution of the autonomic nervous system (ANS). The resolution of this question is exigent for Space Adaptation Syndrome, zero gravity sickness. A case is drawn for the necessity to apply a methodological approach that incorporates: (1) standardization of parameters in relation to the individual differences in variability and prestimulus levels; (2) a concern for patterning of responses; and (3) the physiological association with subjective reports. Vasomotor, heart rate, respiration rate, skin conductance and subjective reports of malaise were collected from 22 subjects while participating in three motion stressors; vertical acceleration, Coriolis stimulation, and combined optokinetic and Coriolis stimulation. The results demonstrate that ANS response patterns can be separated into three mutually exclusive components: (1) a generalized response to motion sickness; (2) a stimulus specific response to the type of stressor being presented; and (3) individualized stereotypical response patterns that are associated with subjective reports of malaise.

Morgan, M. G.↗
DOE OSTI2026

Power output of turbines mounted on tension-leg platforms subjected to fully developed ocean gravity waves

A concern in the deployment of large wind turbines on ocean floating platforms is the effect of floating-platform motions on their electrical power generation. Further, it is not clear how floating motions influence waking, which might affect the combined power generation of collections of turbines. We examine the average power output of a single and a collection of NREL 5 MW wind turbines mounted on a tension-leg platform (TLP) under the action of fully developed ocean wave motions, coupling floating motions with the large-eddy simulation (LES) of atmospheric and rotor dynamics. The ocean dynamics enter as fully developed waves derived from the Pierson–Moskowitz spectrum. To assess the influence of ocean motions, we performed simulations over the full range of wind speeds in the operational range of the turbine, reporting comparisons of average power output when the platforms are allowed to move to when they are held rigidly in place. In all simulations, we find that the effects of the TLP floating-platform's induced motions have a minor effect on single and multiple turbine power production and wake deficits. Even when using coherent and large amplitude harmonic-floating-induced perturbations, any significant wake modifications from floating motions are confined to the near-wake region, where downstream turbines are unlikely to be located. The relatively small amplitude of TLP motions relative to pre-existing turbulent fluctuations are the primary reason for low wake and power modifications downstream.

Restrepo, Juan [ORNL] (ORCID:0000000326092882)↗
DOE OSTI2024

Enhancement of magnetic domain wall velocity via resonant dissipation of standing wave modes of domain wall structure with perpendicular magnetic anisotropy

The dynamic behaviors of magnetic domain walls have significant implications for developing advanced spintronic devices. In this study, we investigate the intriguing resonance phenomenon within the magnetic domain wall structure, focusing on the dissipation mechanism and its impact on domain wall dynamic motion. By applying a static external magnetic field, we observe a remarkable amplification of domain wall velocity through the resonant excitations of the flexure modes. The resonance of the flexure mode exerts an indirect influence on the domain wall velocity through energy dissipation, leading to a significant enhancement from the predictions of the one-dimensional Walker model. We establish a robust model platform rooted in energy dissipation allows comprehensive understanding the dramatic enhancement of domain wall velocity observed during width-directional flexure mode resonance. By directly quantifying energy dissipation, our approach provides highly effective and accurate estimates of domain wall velocity, surpassing previous methods that focus solely on the instantaneous dynamics of the domain wall structure. These findings offer crucial insights into the fundamental mechanisms governing the dynamics of domain walls and other magnetic systems, such as magnetic skyrmions, bubbles, and magnetic vortices, paving the way for development and optimization of next-generation spintronic devices.

Collective dynamics↗
NASA NTRS1974

Fabrication of neurophysiological monitoring systems

A system designed to collect electroencephalographic, electro-oculographic, electromyographic, and head motion data is described. The portable instrumentation provides a rapid and simple means by which neurophysiological data can be obtained by the patient in his home and the taped data returned to the laboratory for analysis. The system was designed primarily for the study of sleep.

Frost, J. D., Jr.↗
NASA NTRS1976

Arctic odyssey - Five years of data buoys in AIDJEX

The Arctic Ice Dynamics Joint Experiment of 1975-1976 used data bouys in conjunction with tracking satellites to study the interaction of Arctic Sea ice with the environment, and, more specifically, to define the motion of ice on the perimeter of the area of interest and to measure surface barometeric pressure over the same area. Charts are presented, indicating the position of the buoy array along with a table detailing buoy characteristics. The position fix accuracy of RAMS (Random Access Measurement System) buoys is discussed together with position errors due to the along-track motion of the observing satellites. Polar satellite data collection and tracking efficiency is assessed together with satellite system flexibility concepts.

Martin, P.↗