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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 433 records · Page 24

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NASA NTRS1990

Interaction of a neutral cloud moving through a magnetized plasma

Current collection by outgassing probes in motion relative to a magnetized plasma may be significantly affected by plasma processes that cause electron heating and cross field transport. Simulations of a neutral gas cloud moving across a static magnetic field are discussed. The authors treat a low-Beta plasma and use a 2-1/2 D electrostatic code linked with the authors' Plasma and Neutral Interaction Code (PANIC). This study emphasizes the understanding of the interface between the neutral gas cloud and the surrounding plasma where electrons are heated and can diffuse across field lines. When ionization or charge exchange collisions occur a sheath-like structure is formed at the surface of the neutral gas. In that region the crossfield component of the electric field causes the electron to E times B drift with a velocity of the order of the neutral gas velocity times the square root of the ion to electron mass ratio. In addition a diamagnetic drift of the electron occurs due to the number density and temperature inhomogeneity in the front. These drift currents excite the lower-hybrid waves with the wave k-vectors almost perpendicular to the neutral flow and magnetic field again resulting in electron heating. The thermal electron current is significantly enhanced due to this heating.

Goertz, C. K.↗

NASA NTRS1991

A method for the analysis of biaxial graded-index optical fibers

The problem of wave propagation is a biaxial graded-index fiber with circular symmetry is considered. The problem is formulated in terms of four first-order differential equations for the tangential components of the electric and magnetic fields. A general solution method for solving systems of differential equations is presented. This solution method is then used to solve the system of equations for a particular example of a biaxial graded-index fiber. Numerical results for the propagation constant in the fiber are given.

Kawalko, Stephen F.↗

NASA NTRS1992

Effects of a lightning discharge detected by the DE 2 satellite over Hurricane Debbie

The satellite observation of a large, about 40-mV/m, transient electric field disturbance over Hurricane Debbie in September 1982 is reported. The electric field event is viewed as a spheric disturbance from a lightning discharge in the active weather system located beneath the satellite. To elucidate this observation of upward moving electrons in the ionosphere associated with a lightning event, several mechanisms for electron acceleration by electric field with components, E(parallel), along the magnetic field are compared. 'Runaway' electrons were accelerated in about 1 ms by a downward directed E(parallel) pulse of about 1 V/m magnitude. Such fields can result from rapidly exposed, negative space charges near the tops of clouds during positive cloud-to-ground discharges. HF frequency Fourier components of the E(parallel) pulse must propagate through the low-conducting nighttime atmosphere to the ionosphere with little dissipation.

Burke, William J.↗

NASA NTRS1993

The interaction of high voltage systems with the environments of the Moon and Mars

High voltage systems designed for use on the lunar and Martian surfaces or in orbit will interact with environmental components such as electrically charged dust, low pressure atmospheres, ionospheric plasmas and neutrals, and chemically reactive species. As the Space Exploration Initiative (SEI) advances from the realm of feasibility study to that of conceptual design, guidelines will be required to ensure that these effects are properly accounted for. A first step in providing such guidelines is the prioritization of interactions for each of the space or surface environments that will be encountered. For those issues that are identified as high priority, the state of environmental knowledge, emphasizing essential data, must be determined. This report describes possible means of obtaining such information, including ground tests, modeling and analysis, and flight experiments. The development of computational tools which will enable engineers to simulate and thereby quantify the interactions will be especially considered. Our analysis is drawn from various study and workshop activities undertaken within the last two years.

Hillard, G. Barry↗

NASA NTRS1994

Continued reduction and analysis of data from the Dynamics Explorer Plasma Wave Instrument

The plasma wave instrument on the Dynamics Explorer 1 spacecraft provided measurements of the electric and magnetic components of plasma waves in the Earth's magnetosphere. Four receiver systems processed signals from five antennas. Sixty-seven theses, scientific papers and reports were prepared from the data generated. Data processing activities and techniques used to analyze the data are described and highlights of discoveries made and research undertaken are tabulated.

Gurnett, Donald A.↗

NASA NTRS1991

A physical control interface with proprioceptive feedback and multiple degrees of freedom

The use of the drug thalidomide by pregnant mothers in Britain resulted in a variety of deformities including the birth of children having no arms. Such children were provided with powered artificial arms with up to five degrees of freedom simultaneously controlled in real time by shoulder movement. The physiological sense of proprioception was extended from the user into the device, reducing the need for visual feedback and conscious control. With the banning of thalidomide, this technique fell into disuse but it is now being re-examined as a control mechanism for other artificial limbs and it may have other medical applications to allow patients to control formerly paralyzed limbs moved by electrical stimulation. It may also have commercial applications in robotic manipulation or physical interaction with virtual environments. To allow it to be investigated further, the original pneumatic control system has recently been converted to an electrical analogue to allow interfacing to electronic and computer-assisted systems. A harness incorporates force-sensitive resistors and linear potentiomenters for sensing position and force at the interface with the skin, and miniature electric motors and lead screws for feeding back to the user the position of the robotic arm and the forces applied to it. In the present system, control is applied to four degrees of freedom using elevation/depression and protraction/reaction of each shoulder so that each collar bone emulates a joystick. However, both electrical and mechanical components have been built in modular form to allow rapid replication and testing of a variety of force and position control strategies.

Creasey, G. H.↗

NASA NTRS1994

Observations of lightning in convective supercells within tropical storms and hurricanes

Cloud-to-ground (CG) lightning observations from land-based lightning detection networks now allow monitoring this component of the electrical structure of tropical storms and hurricanes within a few hundred kilometers of the United States coastline. Several case studies confirm the long-held opinion that lightning is rather common within the outer rainbands. The general absence of CG lightning within the interior of mature tropical cyclones is also apparent. On the other hand, bursts of CG lightning near the circulation center of developing storms appear to precede periods of further deepening. The CG events are associated with convective supercells, whose anvil canopies can often obscure much of the underlying storm. Near-eyewall CG bursts preceding periods of intensification were noted in Hurricanes Diana (1984) and Florence (1988). A detailed case study of the 1987 unnamed tropical storm that struck the Texas-Louisiana coastline reveals that lightning was associated with two large supercells. These supercells appeared to be the trigger for the development of a closed circulation that formed several hours after the apparent low pressure center made landfall. Further studies of lightning may provide additional insight into the role of convective supercells in tropical storm intensification. It may also provide a useful diagnostic of impending deepening.

Lyons, Walter A.↗

NASA NTRS1993

ULF waves in the Io torus: Ulysses observations

Throughout the Io torus, Ulysses has observed intense ultralow frequency (ULF) wave activity in both electric and magnetic components. Such ULF waves have been previously suggested as the source of ion precipitation leading to Jovian aurorae. The peaks of the wave spectra are closely related to the ion cyclotron frequencies, which is evidence of the waves being ion cyclotron waves (ICWs). Analysis of the dispersion relation using a multicomponent density model shows that at high latitudes (approximately 30 deg), peak frequencies of the waves fall into L mode branches of guided or unguided ICWs. Near the equator, in addition to the ICWs below f(sub cO(2+)), there are strong signals at approximately 10 Hz which require an unexpectedly large energetic ion temperature anistropy to be explained by the excitation of either convective or nonconvective ion cyclotron instabilities. Their generation mechanism remains open for the future study. Evaluation of the Poynting vector and the dispersion relation analysis suggest that the waves near the equator had a small wave angle relative to the magnetic field, while those observed at high latitudes were more oblique. The polarization of the waves below f(sub cH(+)) is more random than that of the whistler mode waves, but left-hand-polarized components of the waves can still be seen. The intensity of the ICWs both near the equator and at high latitudes are strong enough to meet the requirement for producing strong pitch angle scattering of energetic ions.

Lin, Naiguo↗

NASA NTRS1977

Light-Activated Amino Acid Transport Systems in Halobacterium halobium Envelope Vesicles: Role of Chemical and Electrical Gradients

The accumulation of 20 commonly occurring L-amino acids by cell envelope vesicles of Halobacterium halobium, in response to light-induced membrane potential and an artificially created sodium gradient, has been studied. Nineteen of these amino acids are actively accumulated under either or both of these conditions. Glutamate is unique in that its uptake is driven only by a chemical gradient for sodium. Amino acid concentrations at half-maximal uptake rates (Km) and maximal transport rates (V(sub max) have been determined for the uptake of all 19 amino acids. The transport systems have been partially characterized with respect to groups of amino acids transported by common carriers, cation effects, and relative response to the electrical and chemical components of the sodium gradient, the driving forces for uptake. The data presented clearly show that the carrier systems, which are responsible for uptake of individual amino acids, are as variable in their properties as those found in other organisms, i. e., some are highly specific for individual amino acids, some transport several amino acids competitively, some are activated by a chemical gradient of sodium only, and some function also in the complete absence of such a gradient. For all amino acids, Na(+) and K(+) are both required for maximal rate of uptake. The carriers for L-leucine and L-histidine are symmetrical in that these amino acids are transported in both directions across the vesicle membrane. It is suggested that coupling of substrate transport to metabolic energy via transient ionic gradients may be a general phenomenon in procaryotes.

MacDonald, Russell E.↗

NASA NTRS2002

Test Facilities in Support of High Power Electric Propulsion Systems

Successful development of space fission systems requires an extensive program of affordable and realistic testing. In addition to tests related to design/development of the fission system, realistic testing of the actual flight unit must also be performed. If the system is designed to operate within established radiation damage and fuel burn up limits while simultaneously being designed to allow close simulation of heat from fission using resistance heaters, high confidence in fission system performance and lifetime can be attained through non-nuclear testing. Through demonstration of systems concepts (designed by DOE National Laboratories) in relevant environments, this philosophy has been demonstrated through hardware testing in the High Power Propulsion Thermal Simulator (HPPTS). The HPPTS is designed to enable very realistic non-nuclear testing of space fission systems. Ongoing research at the HPPTS is geared towards facilitating research, development, system integration, and system utilization via cooperative efforts with DOE labs, industry, universities, and other NASA centers. Through hardware based design and testing, the HPPTS investigates High Power Electric Propulsion (HPEP) component, subsystem, and integrated system design and performance.

VanDyke, Melissa↗

NASA NTRS2004

Probabilistic Physics-Based Risk Tools Used to Analyze the International Space Station Electrical Power System Output

This paper describes the methods employed to apply probabilistic modeling techniques to the International Space Station (ISS) power system. These techniques were used to quantify the probabilistic variation in the power output, also called the response variable, due to variations (uncertainties) associated with knowledge of the influencing factors called the random variables. These uncertainties can be due to unknown environmental conditions, variation in the performance of electrical power system components or sensor tolerances. Uncertainties in these variables, cause corresponding variations in the power output, but the magnitude of that effect varies with the ISS operating conditions, e.g. whether or not the solar panels are actively tracking the sun. Therefore, it is important to quantify the influence of these uncertainties on the power output for optimizing the power available for experiments.

Patel, Bhogila M.↗

NASA NTRS1995

An equivalent body surface charge model representing three-dimensional bioelectrical activity

A new surface-source model has been developed to account for the bioelectrical potential on the body surface. A single-layer surface-charge model on the body surface has been developed to equivalently represent bioelectrical sources inside the body. The boundary conditions on the body surface are discussed in relation to the surface-charge in a half-space conductive medium. The equivalent body surface-charge is shown to be proportional to the normal component of the electric field on the body surface just outside the body. The spatial resolution of the equivalent surface-charge distribution appears intermediate between those of the body surface potential distribution and the body surface Laplacian distribution. An analytic relationship between the equivalent surface-charge and the surface Laplacian of the potential was found for a half-space conductive medium. The effects of finite spatial sampling and noise on the reconstruction of the equivalent surface-charge were evaluated by computer simulations. It was found through computer simulations that the reconstruction of the equivalent body surface-charge from the body surface Laplacian distribution is very stable against noise and finite spatial sampling. The present results suggest that the equivalent body surface-charge model may provide an additional insight to our understanding of bioelectric phenomena.

NASA Discipline Regulatory Physiology↗

NASA NTRS2004

Stirling Engine Dynamic System Modeling

The Thermo-Mechanical systems branch at the Glenn Research Center focuses a large amount time on Stirling engines. These engines will be used on missions where solar power is inefficient, especially in deep space. I work with Tim Regan and Ed Lewandowski who are currently developing and validating a mathematical model for the Stirling engines. This model incorporates all aspects of the system including, mechanical, electrical and thermodynamic components. Modeling is done through Simplorer, a program capable of running simulations of the model. Once created and then proven to be accurate, a model is used for developing new ideas for engine design. My largest specific project involves varying key parameters in the model and quantifying the results. This can all be done relatively trouble-free with the help of Simplorer. Once the model is complete, Simplorer will do all the necessary calculations. The more complicated part of this project is determining which parameters to vary. Finding key parameters depends on the potential for a value to be independently altered in the design. For example, a change in one dimension may lead to a proportional change to the rest of the model, and no real progress is made. Also, the ability for a changed value to have a substantial impact on the outputs of the system is important. Results will be condensed into graphs and tables with the purpose of better communication and understanding of the data. With the changing of these parameters, a more optimal design can be created without having to purchase or build any models. Also, hours and hours of results can be simulated in minutes. In the long run, using mathematical models can save time and money. Along with this project, I have many other smaller assignments throughout the summer. My main goal is to assist in the processes of model development, validation and testing.

Nakis, Christopher G.↗

NASA NTRS2005

Lightning Often Strikes Twice

Contrary to popular misconception, lightning often strikes the same place twice. Certain conditions are just ripe for a bolt of electricity to come zapping down; and a lightning strike is powerful enough to do a lot of damage wherever it hits. NASA created the Accurate Location of Lightning Strikes technology to determine the ground strike point of lightning and prevent electrical damage in the immediate vicinity of the Space Shuttle launch pads at Kennedy Space Center. The area surrounding the launch pads is enmeshed in a network of electrical wires and components, and electronic equipment is highly susceptible to lightning strike damage. The accurate knowledge of the striking point is important so that crews can determine which equipment or system needs to be retested following a strike. Accurate to within a few yards, this technology can locate a lightning strike in the perimeter of the launch pad. As an added bonus, the engineers, then knowing where the lightning struck, can adjust the variables that may be attracting the lightning, to create a zone that will be less susceptible to future strikes.

Source record↗

NASA NTRS2006

Evaluating the Performance of the NASA LaRC CMF Motion Base Safety Devices

This paper describes the initial measured performance results of the previously documented NASA Langley Research Center (LaRC) Cockpit Motion Facility (CMF) motion base hardware safety devices. These safety systems are required to prevent excessive accelerations that could injure personnel and damage simulator cockpits or the motion base structure. Excessive accelerations may be caused by erroneous commands or hardware failures driving an actuator to the end of its travel at high velocity, stepping a servo valve, or instantly reversing servo direction. Such commands may result from single order failures of electrical or hydraulic components within the control system itself, or from aggressive or improper cueing commands from the host simulation computer. The safety systems must mitigate these high acceleration events while minimizing the negative performance impacts. The system accomplishes this by controlling the rate of change of valve signals to limit excessive commanded accelerations. It also aids hydraulic cushion performance by limiting valve command authority as the actuator approaches its end of travel. The design takes advantage of inherent motion base hydraulic characteristics to implement all safety features using hardware only solutions.

Gupton, Lawrence E.↗

NASA NTRS2006

A Brief Summary of Some of the Laboratory Astrophysics Workshop

Our present knowledge of the molecular universe has come primarily from radio observations [ I include here millimeter and submillimeter in this rubric]. There are a number of reasons for this but the primary one is the extremely high spectral resolution. The ease of observing emission from the volume of dense molecular clouds without significant attenuation by scattering from dust has shown this to be the powerful observational tool for molecular astronomy. Finally the relative simplicity of rotational compared to vibrational or electronic spectroscopy allows carrier identification as well as facile evaluation of cloud conditions such as density and temperature. These virtues become tenuous as the astronomical observations are pushed to higher frequencies for enhanced observational sensitivity. Thus precision rest frequencies are mandatory for the search for new species. We may inquire about which new species require particular attention, and which species may be relatively safely predicted on the basis of lower frequency laboratory measurements. For a rigid rotor the three rotational constants are sufficient to completely specify the transition frequencies. The intensities require the three components of the electric dipole moment. For semirigid species, where the centrifugal distortion, may be treated at the quartic level of angular momentum (Bunker et al. 1998), up to five additional constants are required (Watson 1967). There are a number of such species of considerable interest, where laboratory measurements are adequate for astronomical searches.

Klemperer, William↗

NASA NTRS2010

Shuttle Environmental Assurance: Brominated Flame Retardants - Concerns, Drivers, Potential Impacts and Mitigation Strategies

Brominated Flame Retardants (BFRs) are widely used in the manufacture of electrical and electronic components and as additives in formulations for foams, plastics and rubbers. The United States (US) and the European Union (EU)have increased regulation and monitoring of of targeted BFRs, such as Polybrominated Diphenyl Ethers (PBDEs) due to the bioaccumulative effects in humans and animals. In response, manufacturers and vendors of BFR-containing materials are changing flame-retardant additives, sometimes without notifying BFR users. In some instances, Deca-bromodiphenylether (Deca-BDE) and other families of flame retardants are being used as replacement flame retardants for penta-BDE and octa-BDE. The reformulation of the BFR-containing material typically results in the removal of the targeted PBDE and replacement with a non-PBDE chemical or non-targeted PBDE. Many users of PBDE -based materials are concerned that vendors will perform reformulation and not inform the end user. Materials performance such as flammability, adhesion , and tensile strength may be altered due to reformulation. The requalification of newly formulated materials may be required, or replacement materials may have to be identified and qualified. The Shuttle Enviornmental Assurance (SEA) team indentified a risk to the Space Shuttle Program associated with the possibility that targeted PBDEs may be replaced without notification. Resultant decreases in flame retardancy, Liquid Oxygen (LOX) compatibility, or material performance could have serious consequences.

Clark-Ingram, Marceia↗

NASA NTRS2003

Perovskite Superlattices as Tunable Microwave Devices

Experiments have shown that superlattices that comprise alternating epitaxial layers of dissimilar paraelectric perovskites can exhibit large changes in permittivity with the application of electric fields. The superlattices are potentially useful as electrically tunable dielectric components of such microwave devices as filters and phase shifters. The present superlattice approach differs fundamentally from the prior use of homogeneous, isotropic mixtures of base materials and dopants. A superlattice can comprise layers of two or more perovskites in any suitable sequence (e.g., ABAB..., ABCDABCD..., ABACABACA...). Even though a single layer of one of the perovskites by itself is not tunable, the compositions and sequence of the layers can be chosen so that (1) the superlattice exhibits low microwave loss and (2) the interfacial interaction between at least two of the perovskites in the superlattice renders either the entire superlattice or else at least one of the perovskites tunable.

Christen, H. M.↗