Search NASA⌕ Search

SEARCH · Search NASA

Results for “ion conductivity”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Dry matter and nitrogen accumulation are not affected by superoptimal concentration of ammonium in flowing solution culture with pH control

While it is known that superoptimal concentrations of the nitrate (NO3-) ion in solution culture do not increase NO3- uptake or dry matter accumulation, the same is not known for the ammonium (NH4+) ion. An experiment was conducted utilizing flowing solution culture with pH control to investigate the influence of superoptimal NH4+ concentrations on dry matter, nitrogen (N), potassium (K), calcium (Ca), and magnesium (Mg) accumulation by nonnodulated soybean plants. Increasing the NH4+ concentration in solution from 1 to 10 mM did not affect dry matter or N accumulation. Accumulations of K, Ca, and Mg were slightly decreased with increased NH4+ concentration. The NH4+ uptake system, which is saturated at less than 1mM NH4+, is able to regulate uptake of NH4+ at concentrations as high as 10 mM.

NASA Discipline Life Support Systems↗
NASA NTRS2003

Effect of Branching on Rod-coil Polyimides as Membrane Materials for Lithium Polymer Batteries

This paper describes a series of rod-coil block co-polymers that produce easy to fabricate, dimensionally stable films with good ionic conductivity down to room temperature for use as electrolytes for lithium polymer batteries. The polymers consist of short, rigid rod polyimide segments, alternating with flexible, polyalkylene oxide coil segments. The highly incompatible rods and coils should phase separate, especially in the presence of lithium ions. The coil phase would allow for conduction of lithium ions, while the rigid rod phase would provide a high degree of dimensional stability. An optimization study was carried out to study the effect of four variables (degree of branching, formulated molecular weight, polymerization solvent and lithium salt concentration) on ionic conductivity, glass transition temperature and dimensional stability in this system.

Meador, Mary Ann B.↗
NASA NTRS1992

The effect of magnetospheric ion bombardment on the reflectance of Europa's surface

Laboratory investigations have been conducted to ascertain the role of sulphur ion implantation on differences in the reflectivity of the leading and trailing atmospheres of Europa in the visible and UV ranges. Under the laboratory conditions tested, neither S-implantation nor SO2 deposition can account for the general 'reddening' of the trailing hemisphere in the UV, relative to the leading hemisphere; this feature has been shown to be producible by fast penetrating ions.

Sack, N. J.↗
NASA NTRS1983

Eclipse-related measurements of middle-atmosphere electrical parameters

Measurements of electrical conductivity and its constituent parameters, charge density and ion mobility, are presented for the solar eclipse rocket campaign conducted at Red Lake, Ontario, Canada. Three parachute-borne probes (two Gerdien condensers and a blunt probe) were flown during the eclipse which occurred on 26 February 1979. Additional payloads launched at other times provided important supplemental background measurements. The entire launch series occurred during aurorally active conditions, as indicated by the probe measurements. Specifically, positive conductivity enhancements above 45 km demonstrate the dominance of auroral ionization as a source for positive ions in the region. Such effects evidenced during the eclipse make it difficult to determine the extent to which the decrease in positive conductivity above 60 km is eclipse-related. The negative conductivity component associated with free electrons displays solar dependence both during the eclipse and for the other measurement periods. In spite of the aurorally active conditions, rapid electron loss was observed during totality, thus indicating the importance of non-ionizing solar effects on electrons in the region.

Mitchell, J. D.↗
NASA NTRS1972

Cooling and evolution of a supernova remnant.

Discussion of the structure, evolution, and cooling of an old supernova remnant, aimed at providing a theoretical framework for relating remnants with similar energies and environments but of different ages. Discussed evolution details include the Sedov-Taylor blast wave, the electron-ion equipartition and thermal conduction, the temperature sag and the dynamics in the process of transition to a dense shell, and the history of remnant luminosity.

Cox, D. P.↗
NASA NTRS1973

Neutral winds above 200 km at high latitudes.

Electrically neutral, luminous clouds are a by-product of chemical releases conducted to create barium ion clouds for the measurement of electric fields. Wind measurements provided by the motions of these clouds are particularly valuable in that the motions can be directly compared with convective ion drift motions to test the importance of ion drag forces. Motion from multiple releases between 200 and 300 km from 15 rockets launched from four high-latitude locations is analyzed in this paper. The observations in the evening and midnight hours at magnetic latitudes above 65 deg strongly suggest that in these regions ion drag is the dominant force in driving neutral winds between 200 and 300 km. In the morning sector, it is evident that neutral wind observations cannot be directly interpreted in terms of ion drag; other factors must be considered.

Meriwether, J. W.↗
NASA NTRS1975

Diurnal variations in the thermosphere. I - Theoretical formulation

A nonlinear perturbation theory is formulated for the solution of the multicomponent equations of energy, mass, and momentum conservation in the atmosphere. The theory is three-dimensional and includes the effects of heat conduction and advection, viscosity, ion drag, and diffusion. The theory is described as a superposition of mathematical modes obtained by expanding the physical quantities into vector and spherical harmonics. The coupling between the various modes, both linear and nonlinear, is included. The theory provides a basis for the treatment of the thermosphere and its interaction with the lower atmosphere, where 'mode coupling' is most important. As an example, a comparison is presented between one-dimensional and three-dimensional calculations of the fundamental mode of the diurnal component in the thermosphere. Coupling between the lowest modes is considered to describe the physical conditions of the lower thermosphere where inertia and Coriolis forces become dominant over the ion-drag and viscous forces. In this region, the latitude structures of the temperature, wind field, and diffusively controlled oxygen are shown to change significantly.

Harris, I.↗
NASA NTRS1979

Neutralization tests on the SERT II spacecraft

Orbit precession returned the SERT II spacecraft to continuous sunlight in January 1979 for the first time since early 1972, and new experiments were planned and conducted. Neutralization of an ion beam was accomplished by a second neutralizer cathode located 1 meter away. Plasma potential measurements were made of the plasma surrounding the ion beam and connecting the beam to the second neutralizer. When the density of the connecting plasma was increased by turning on the main discharge of a neighboring ion thruster, the neutralization of the ion beam occurred with improved (lower) coupling voltage. These and other tests reported should aid in the future design of spacecraft using electric thruster systems. Data taken indicate that cross neutralization of ion thrusters in a multiple thruster array should occur readily.

Kerslake, W. R.↗
NASA NTRS1981

ISEE 1 observations of thermal plasma in the vicinity of the plasmasphere during periods of quieting magnetic activity

An investigation of thermal plasma behavior in the vicinity of the plasmasphere during periods of quieting magnetic activity was conducted by combining thermal ion observations made with the plasma composition experiment on ISEE 1 with plasma density profiles obtained from plasma frequency measurements made with the same satellite's plasma wave experiment. During periods in which the magnetic activity quiets, the two regions characterized by H(+):He(+):O(+) (isotropic) and H(+):O(+):He(+) (field-aligned) ion species distributions (in order of dominance) are separated by a new region in which low-energy H(+) and He(+) are found flowing along the magnetic field lines. At other times, following quieting magnetic activity, distributions having peak fluxes at 90 deg pitch angle are observed in this region.

Horwitz, J. L.↗
NASA NTRS1984

A numerical study of the stability of radiative shocks

Attention is given to the oscillatory instability of optically thin radiative shocks in time-dependent numerical calculations of accretion flows onto degenerate dwarfs. The present nonlinear calculations yield good quantitative agreement with the linear results obtained for oscillation frequencies, damping rates, and critical alpha-values. The fundamental mode and the first overtone in the shock radius and luminosity variations can be clearly identified, and evidence is sometimes seen for the second overtone. Time-dependent calculations are also performed which include additional physics relevant to degenerate dwarf accretion, such as electron thermal conduction, unequal electron and ion temperatures, Compton cooling, and relativistic corrections to the bremsstrahlung cooling law. All oscillatory modes are found to be damped, and hence stable, in the case of a 1-solar mass white dwarf accreting in spherical symmetry.

Imamura, J. N.↗
NASA NTRS1985

Perforating Thin Metal Sheets

Sheets only few mils thick bonded together, punched, then debonded. Three-step process yields perforated sheets of metal. (1): Individual sheets bonded together to form laminate. (2): laminate perforated in desired geometric pattern. (3): After baking, laminate separates into individual sheets. Developed for fabricating conductive layer on blankets that collect and remove ions; however, perforated foils have other applications - as conductive surfaces on insulating materials; stiffeners and conductors in plastic laminates; reflectors in antenna dishes; supports for thermal blankets; lightweight grille cover materials; and material for mockup of components.

Davidson, M. E.↗
NASA NTRS1985

Generation of auroral Omega bands by shear instability of the neutral winds

Thermospheric neutral wind acceleration via ion drag in the conducting E-region of the ionosphere is greatly increased by electron precipitation associated with auroras. This increased acceleration can lead to the development of significant horizontal wind shears, which were found to be unstable to the Kelvin-Helmholtz shear instability. Numerical simulation of the neutral response to an intense, postmidnight, diffuse aurora shows tne formation of an E-region 'jet stream' within the aurora, with peak winds speeds greather than 700 m/s after one hour. It is proposed that this jet stream produces unstable Kelvin-Helmholtz waves, which can drive waves of discrete aurora along the poleward boundary of the preexisting diffuse aurora. It is suggested that such auroral waves, driven by the neutral winds, form eastward propagating waves (omega bands) occasionally observed along the poleward boundary of postmidnight diffuse auroras. It was found that neutral wind shears that develop in response to discrete auroral arcs are unstable; however, the resulting wind waves are not expected to drive significant auroral waves along discrete arcs.

Lyons, L. R.↗
NASA NTRS1987

Initial results from the operation of two argon ion generators in the auroral ionosphere

Two argon ion generators have been lofted by sounding rockets in order to investigate ion beam dynamics and beam effects on the ionosphere, and auroral electrodynamics during rocket passage over auroral arcs. The ion generators were on a subpayload that was separated from the main payload early in the flight. The main payload conducted the diagnostic measurements during ion beam operations. Evidence of heating of the ionosphere around the subpayload during each ion beam emission is noted.

Erlandson, R. E.↗
NASA NTRS1988

A comparative study of plasma expansion events in the polar wind

The temporal characteristics of the polar wind have been studied using a simplified set of collisionless equations and a full set of hydrodynamic equations which contained continuity, momentum, and energy equations for H(+), O(+), and electrons, including collisional conductivities and variable isotropic, ion and electron temperatures. The temporal evolution of the polar wind was modeled for initial, extended density depletions of factors of 3, 10, and 100 starting at several altitudes for each model. Comparison of the results from the two models showed the same temporal characteristics for the polar wind densities, flow velocities, and escape fluxes. The characteristics of plasma expansion are presented. It is found that the propagation velocities of the disturbance vary with the level of the depletion.

Gombosi, Tamas I.↗
NASA NTRS1989

The use of dc-probe measurements in the middle atmosphere program

The middle atmosphere is weakly ionized, collision dominated plasma. Rocket-borne dc probes have proven effective in measuring conductivity and electron and ion concentrations in this plasma, and in some cases electron temperatures and ion composition were observed. During MAP, dc probes were also used successfully to study turbulence in the middle atmosphere, using the plasma as a passive tracer for the dynamical processes in the nonionized gas. Basic principles are reviewed of the dc-probe technique and examples are presented of results obtained during MAP.

Thrane, E. V.↗
NASA NTRS1991

Nondestructive evaluation tools and experimental studies for monitoring the health of space propulsion systems

An overview is given of background and information on space propulsion systems on both the programmatic and technical levels. Feasibility experimental studies indicate that nondestructive evaluation tools such as ultrasonic, eddy current and x-ray may be successfully used to monitor the life limiting failure mechanisms of space propulsion systems. Encouraging results were obtained for monitoring the life limiting failure mechanisms for three space propulsion systems; the degradation of tungsten arcjet and magnetoplasmadynamic electrodes; presence and thickness of spallable electrically conducting molybdenum films in ion thrusters; and the degradation of the catalyst in hydrazine thrusters.

Generazio, Edward R.↗
NASA NTRS1991

Nondestructive evaluation tools and experimental studies for monitoring the health of space propulsion systems

An overview is given of background and information on space propulsion systems on both the programmatic and technical levels. Feasibility experimental studies indicate that nondestructive evaluation tools such as ultrasonic, eddy current and X-ray may be successfully used to monitor the life limiting failure mechanisms of space propulsion systems. Encouraging results were obtained for monitoring the life limiting failure mechanims for three space propulsion systems: the degradation of tungsten arcjet and magnetoplasmadynamic electrodes; presence and thickness of spallable electrically conducting molybdenum films in ion thrusters; and the degradation of the catalyst in hydrazine thrusters.

Generazio, Edward R.↗