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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Theory of the fly-through mode for neutral mass spectrometers

The Atmosphere Explorer satellites carry a quasi-open source neutral mass spectrometer which has the capability to operate in a nonstagnating or 'fly-through' mode. Technical information on the operating characteristics of fly-through along with considerable scientific data have been acquired in this mode. When the vehicle is spun, the fly-through signal contains information on the kinetic temperature as well as the neutral density. Both quantities can be extracted from the data once the theory of operation is formulated in terms of the ambient gas velocity distribution and the angular response of the instrument.

Kayser, D. C.↗
NASA NTRS1979

Experimental transition probabilities and Stark-broadening parameters of neutral and single ionized tin

Strengths and Stark-effect widths of the Sn I and Sn II lines prominent between 3200 and 7900 A are measured with a spectroscopic shock tube. Absolute strengths of 17 ionic lines are obtained with estimated (22-50)% accuracy and conform to appropriate quantum-mechanical sum rules. Relative transition probabilities for nine prominent neutral tin lines, normalized to radiative-lifetime data, are compared with other experiments and theoretical predictions. Parameters for Stark-effect broadening are measured over a range of plasma electron densities. Broadening data (with accuracies of 15-35%) for one neutral and ten ionic lines of tin are compared to theoretical predictions.

Miller, M. H.↗
NASA NTRS1979

Position paper on the potential of inadvertent weather modification of the Florida Peninsula resulting from neutralization of space shuttle solid rocket booster exhaust clouds

A concept of injecting compounds into the exhaust cloud was proposed to neutralize the acidic nature of the low-level stabilized ground cloud (SGC) was studied. The potential Inadvertent Weather Modification caused by exhaust cloud characteristics from three hours to seven days after launch was studied. Possible effects of the neutralized SGC in warm and cloud precipitation processes were discussed. Based on a detailed climatology of the Florida Peninsula, the risk for weather modification under a variety of weather situations was assessed.

Bollay, E.↗
NASA NTRS1980

Laboratory studies of the charge neutralization of a rocket payload during electron beam emission

The charge neutralization of an electrically-isolated rocket payload emitting an energetic electron beam has been studied in experiments in the large vacuum chamber at Johnson Space Center. The introduction of an RF-discharge-produced ambient plasma density (10,000 to 50,000 per cu cm) reduces the payload potential to 200 V for low current (1 and 10 ma) beams. The ignition of the beam-plasma discharge provides an efficient neutralization process for higher current beams.

Bernstein, W.↗
NASA NTRS1980

A statistical determination of the shape and position of the geomagnetic neutral sheet

Using 2.5-minute average field values from Imp 6, 7, and 8 magnetic field measurements, the standard magnetotail neutral sheet (MNS) model is examined. The best representation for the MNS is found to be an arched surface which crosses the solar magnetospheric equatorial plane on the flanks of the tail about 18 earth radii (ER) from the tail axis; the surface is anchored to the geomagnetic dipole at a hinging distance of 10.5 ER. In addition, the shape and position of the neutral sheet (NS) do not vary significantly with distance down the tail, but the NS is anchored somewhat closer to the earth during disturbed geomagnetic conditions.

Fairfield, D. H.↗
NASA NTRS1980

Pioneer Venus Orbiter neutral gas mass spectrometer experiment

The Pioneer Venus Orbiter Neutral Mass Spectrometer (ONMS) is designed to measure the vertical and horizontal density variations of the major neutral constituents in the upper atmosphere of Venus. The mass spectrometer sensor includes a retarding potential ion source, hyperbolic quadrupole rod analyzer, and electron multiplier detector. The supporting electronic system consists of hybrid integrated circuits to reduce weight and power. The ONMS instrument was launched aboard the Pioneer Venus Orbiter on May 20, 1978, and turned on in orbit around Venus on December 4, 1978. It has operated flawlessly for over a Venus year (243 earth days) and has returned data of the composition of the major constituents in the Venus atmosphere between the altitudes of 150 and 350 km.

Niemann, H. B.↗
NASA NTRS1980

Observations of neutral wind profiles between 115- and 175-km altitude in the dayside auroral oval

Lithium trail neutral wind measurements have been made in the morning dayside auroral oval as a function of altitude. During all four experiments the winds displayed a large altitude shear. In the most extreme case the wind at 135-km altitude was toward the south at 210 m/s, and at 185-km altitude toward the northwest at 170 m/s. A one-dimensional numerical solution to the Navier Stokes equation including an initial steady-state wind profile, viscosity, pressure gradient, Lorenz force and the Coriolis force was made in order to study the effect of auroral processes on the neutral atmosphere. Since electric fields and plasma density were measured, the Lorenz force could be modeled with reasonable accuracy. The pressure gradient was determined in an iterative way as a best fit to the observations. Within the limitations of a one-dimensional model the numerical solution is in reasonable agreement with one of the observations, which is applicable to such a modeling, and indicates that both Lorenz forces and pressure gradients due to auroral processes are required to explain the observation.

Pereira, E.↗
NASA NTRS1980

Correlations between neutral meridional winds and ion densities observed on AE-E

The southward directed neutral meridional wind and the nighttime ion density simultaneously measured on AE-E for altitudes from 250 to 290 km are compared and found to correlate when the magnetic field inclination is negative and anticorrelate when the inclination is positive. This effect is attributed to neutral winds transporting the ions up or down a field line depending upon the sign of the field-aligned wind and the inclination. Model calculations for the ion density in the presence of a field-aligned wind and ambipolar diffusion are presented. Six examples of this ionospheric response are analyzed and found to be in qualitative and approximate quantitative agreement with the theoretical results.

Wharton, L. E.↗
NASA NTRS1982

Neutralizing Amine-Cured Epoxy Surfaces

New surface treatment is a rapid, convenient, and effective method for converting unused amines and amine functional groups into neutral, noncorrosive substituted urea. Reaction proceeds at room temperature, takes only a few minutes, and leaves no corrosive residue. Surface should first be washed with alcohol to remove as much as possible of unreacted amine. Then it should be dried, since residual moisture or alcohol may consume some of treatment reagent and neutralization may then be incomplete.

Lee, S. Y.↗
NASA NTRS1981

Additional application of the NASCAP code. Volume 2: SEPS, ion thruster neutralization and electrostatic antenna model

The interactions of spacecraft systems with the surrounding plasma environment were studied analytically for three cases of current interest: calculating the impact of spacecraft generated plasmas on the main power system of a baseline solar electric propulsion stage (SEPS), modeling the physics of the neutralization of an ion thruster beam by a plasma bridge, and examining the physical and electrical effects of orbital ambient plasmas on the operation of an electrostatically controlled membrane mirror. In order to perform these studies, the NASA charging analyzer program (NASCAP) was used as well as several other computer models and analytical estimates. The main result of the SEPS study was to show how charge exchange ion expansion can create a conducting channel between the thrusters and the solar arrays. A fluid-like model was able to predict plasma potentials and temperatures measured near the main beam of an ion thruster and in the vicinity of a hollow cathode neutralizer. Power losses due to plasma currents were shown to be substantial for several proposed electrostatic antenna designs.

Katz, I.↗
NASA NTRS1980

Ion temperature troughs induced by a meridional neutral air wind in the night-time equatorial topside ionosphere

A mathematical model was constructed to calculate O(+) and H(+) concentrations, field-aligned velocities, and electron temperatures in the night-time equatorial topside ionosphere. The model is used to establish the ability of F-region neutral air winds to produce observed ion temperature distributions, and to study the properties of ion temperature troughs as functions of altitude, latitude, and ionospheric composition. The O(+) - H (+) transition height represents an altitude limit above which the ion cooling from adiabatic expansion of the plasma is very small; the northern and southern edges of the ion temperature troughs are restricted to the limiting dip altitudes determined by magnetic field line geometry and by the functional form of the F-region neutral wind velocity.

Bailey, G. J.↗
NASA NTRS1981

Neutral thermospheric temperature from ion concentration measurements

A technique for extracting information on neutral temperature from in situ F region measurements of O(+) and H(+) ion concentrations is analyzed and evaluated. Advantage is taken of the condition of charge-exchange equilibrium of these species in the neighborhood of 320 km to infer the associated relative abundances of neutral oxygen and hydrogen. Results are shown to be generally consistent with other concurrent in situ measurements.

Breig, E. L.↗
NASA NTRS1981

Spectroscopy of neutral-colored QSO candidates

Spectroscopic observations of 21 QSO candidates are discussed; the candidates were taken mainly from sets of objects described as neutral colored that have been listed as possible identifications of radio sources. Candidate identifications are accepted for study without color discrimination (that is, neutral-colored and even reddish objects are examined) in the hope of removing possible bias against finding QSOs with z greater than approximately 3.5. The largest redshift among the objects described here, however, is z = 2.43. The observations therefore support the tentative conclusion that the decline in numbers of objects with z greater than approximately 3 among these samples is real.

Baldwin, J. A.↗
NASA NTRS1981

Neutral winds and electric fields in the dusk auroral oval. I - Measurements

Two rockets carrying an upleg and downleg trimethyl aluminum chemical trail release and three barium cannisters were launched from Poker Flat, Alaska on Feb. 28, 1978 and Mar. 2, 1978 in order to study neutral winds and electric fields in the dusk auroral oval. Electric field measurements were also made with a radar system to supplement the barium cloud data. The barium cloud drifts on both days showed intense poleward electric fields in the subauroral region. The drifts were nearly latitude-independent and were equivalent to electric fields of 60 mV/m of February 2 and 40 mV/m on March 2. The data indicate that the Lorentz force and Joule heating had a strong influence on the observed neutral winds.

Mikkelsen, I. S.↗
NASA NTRS1981

Fluid model of plasma outside a hollow cathode neutralizer

The present study analyzes the capability of a fluid model of electron transport to explain observed properties of the external plasma of a hollow cathode neutralizer used to neutralize beams emerging from ion thrusters. Calculations reported here show that when the effective collision frequency in such a model is near the plasma frequency, the resulting electric potential and electron temperature variations are in qualitative agreement with values measured in the plume mode of the hollow cathode. Both theory and experiment show strong variations of temperature and potential within a few centimeters of the cathode orifice.

Parks, D. E.↗
NASA NTRS1981

Magnetospheric substorm models - Comparison with neutral sheet magnetic field observations

Four models for geomagnetic substorms, a quiet tail model, and models incorporating structural effects of the tail are examined for consistency with magnetic-field data during satellite crossings of the tail neutral sheet/plasma sheet. For this data the tearing mode instability model is always consistent, and inward moving distant neutral line is sometimes consistent, quasi-steady reconnection with slow shock and intermediate wave structure and locally quiet tail rarely consistent, and an outward propagating rarefaction wave is never consistent with the magnetic observations. In several cases structural effects of the tail are consistent with key features of the magnetic signatures.

Speiser, T. W.↗
NASA NTRS1981

Distribution of neutral gas and dust near Saturn

The distribution of neutral gas and dust within the magnetosphere of Saturn has been inferred from the electron velocity distribution functions measured by the Voyager 1 plasma science experiment. Substantial enhancements of neutral material near Titan and in the vicinity of Enceladus are found. The E ring is also shown to be larger than previously thought.

Sittler, E. C., Jr.↗
NASA NTRS1981

An investigation of the neutral and ionized gas in M16

An attempt is made to understand the physical and kinematic conditions in the M16 active star formation site, by means of mapping observations of neutral and ionized hydrogen and observations of (C-12)O from selected positions within the H II regions. The 21-cm maps suggest that at least two neutral clouds are present in the M16 complex, one of which is likely to be the remains of the cloud in which star formation initially occurred, and the other is probably the cold gas remaining from a disrupted cloud edge where the ionization front has crossed the cloud-intercloud boundary. Multislit echelle spectra of the H-alpha line are obtained to determine the physical conditions within the ionized gas, and H-alpha maps show that the ionized gas is systematically blueshifted in the east and splits into two streams in the southwest.

Mufson, S. L.↗