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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Thin electrostatically self-focusing electron streams.

Study of 30 to 380 microampere, 50 to 550 V, 1 to 2 mm, electrostatically self-focusing electron streams (50 cm long) drifting through mercury vapor (at 50 microtorr to 2 millitorr) in a tube with a radius of 6.6 cm. The inside surface of the tube is coated with a transparent layer whose resistivity is 50 ohm-cm per centimeter. In order to determine the charged-particle densities and the potential profile in and around the beam without disturbing the system, a multigrid electrostatic charged particle energy analyzer was used to study separately the energy distributions of both ions and electrons ejected radially from the beam. The results show two energy groupings for electrons. The energy distribution of the high-energy group is produced by ionizing collisions between beam electrons and neutral gas atoms; a group of flow-energy electrons becomes trapped in the potential well within and around the beam, subsequently escaping by collisional mechanisms.

Mccorkle, R. A.↗
NASA NTRS1992

Neutralizer and sample chamber for the Atomic Oxygen Simulation System (AOSS)

A neutralizer system capable of converting a beam of oxygen ions (O(+) or O2(+)) into a beam of low-energy neutral oxygen atoms (O) was developed. The neutralizer system is to be designed to be compatible with the Atomic Oxygen Simulation System (AOSS) located in the Physical Science Branch of MSFC. The Center for Molecular and Atomic Studies at Surfaces (CMASS) at Vanderbilt University has met these objectives by developing a system that neutralizes the ions through electron transfer during a grazing-incidence reflection of an ion beam from a smooth nickel surface. The purpose is to describe the system, provide schematic representations of the system, and to discuss the use of the system in relation to the AOSS at the Physical Science Branch of MSFC.

Albridge, Royal G.↗
NASA NTRS1978

Ion beam plume and efflux measurements of an 8-cm mercury ion thruster

Measurements of the ion beam plume and efflux constituents of an 8-cm mercury ion thruster have been carried out in the TRW 5 x 10 foot testing chamber. Charged components (ion beam plume) were measured with an array of movable position Faraday cups and retarding potential analyzers yielding both current density and particle energy determinations. Neutral components (ion beam efflux) were determined with a movable position ionization gauge. Measurements of the ion beam plume were performed for a thruster both with and without a sputter shield. Analysis of data in terms of normalized effluxes has been carried out and has been applied to an example calculation of efflux compatibility with a communications spacecraft.

Komatsu, G. K.↗
NASA NTRS1979

Further laboratory measurements of the beam-plasma discharge

The paper presents laboratory measurements of the beam-plasma discharge (BPD) produced when an energetic electron beam traverses an initially neutral gas. The results show that the critical beam current is related to energy, magnetic field, and the system length by an empirical relationship at pressures below 2 times 10 to the -5th power torr. This relationship describes the accumulation of ambient plasma density collisionally produced by the beam to a critical value at which ignition occurs. Additional measurements of the narrow-band cyclotron-related waves observed at beam currents below BPD threshold do not clearly establish whether this instability is a precursor to the BPD.

Bernstein, W.↗
NASA NTRS1973

Plasma fluctuations in a Kaufman thruster

Measurements of the RMS magnitude, spectra, and cross correlations for the fluctuations in the beam, discharge, and neutralizer keeper currents are presented for a 30 cm diameter dished grid ion thruster for a range of magnetic baffle currents. The ratio of RMS to mean ion beam current varied from 0.04 to 0.23. The spectra of the amplitudes of the beam and discharge current fluctuations were taken up to 9 MHz and show that the predominant amplitudes occur at frequencies of 10 kHz or below. The falloff with increasing frequency is rapid. Frequencies above 100 kHz the spectral levels are 45 kb or more below the maximum peak amplitudes. The cross correlations revealed the ion beam fluctuations to have large radial and axial scales.

Serafini, J. S.↗
NASA NTRS1994

Participation in the definition, conduct, and analysis of particle accelerator experiments for the first Spacelab Mission

The Space Experiments with Particle Accelerators (SEPAC) is a joint endeavor between NASA and the Institute of Space and Aeronautical Sciences (ISAS) in Japan. Its objectives are to use energetic electron beams to investigate beam-atmosphere interactions and beam-plasma interactions in the earth's upper atmosphere and ionosphere using the shuttle Spacelab. Two flights of SEPAC have occurred to date (Spacelab 1 on STS-9 in Nov.-Dec. 1983 and ATLAS 1 on STS-45 in Mar.-Apr. 1992). The SEPAC instrumentation is available for future missions, and the scientific results of the first two missions justify further investigations; however, at present there are no identifiable future flight opportunities. As specified in the contract, the primary purpose of this report is to review the scientific accomplishments of the ATLAS 1 SEPAC experiments, which have been documented in the published literature, with only a brief review of the earlier Spacelab 1 results. One of the main results of the Spacelab 1 SEPAC experiments was that the ejection of plasma from the magnetoplasmadynamic (MPD) arcjet was effective in maintaining vehicle charge neutralization during electron beam firings, but only for a brief period of 10 ms or so. Therefore, a xenon plasma contactor, which can provide continuous vehicle charge neutralization, was developed for the ATLAS 1 SEPAC experiments. Because of the successful operation of the plasma contactor on ATLAS 1, it was possible to perform experiments on beam-plasma interactions and beam-atmosphere interactions at the highest beam power levels of SEPAC. In addition, the ability of the plasma contactor to eject neutral xenon led to a successful experiment on the critical ionization velocity (CIV) phenomena on ATLAS 1.

Burch, J. L.↗
NASA NTRS1990

Advances in atomic oxygen simulation

Atomic oxygen (AO) present in the atmosphere at orbital altitudes of 200 to 700 km has been shown to degrade various exposed materials on Shuttle flights. The relative velocity of the AO with the spacecraft, together with the AO density, combine to yield an environment consisting of a 5 eV beam energy with a flux of 10(exp 14) to 10(exp 15) oxygen atoms/sq cm/s. An AO ion beam apparatus that produces flux levels and energy similar to that encountered by spacecraft in low Earth orbit (LEO) has been in existence since 1987. Test data was obtained from the interaction of the AO ion beam with materials used in space applications (carbon, silver, kapton) and with several special coatings of interest deposited on various surfaces. The ultimate design goal of the AO beam simulation device is to produce neutral AO at sufficient flux levels to replicate on-orbit conditions. A newly acquired mass spectrometer with energy discrimination has allowed 5 eV neutral oxygen atoms to be separated and detected from the background of thermal oxygen atoms of approx 0.2 eV. Neutralization of the AO ion beam at 5 eV was shown at the Martin Marietta AO facility.

Froechtenigt, Joseph F.↗
NASA NTRS1980

Structural attachments for large space structures

The feasibility of fabricating beams in space and using them as components of a large, crew assembled structure, was investigated. Two projects were undertaken: (1) design and development of a ground version of an automated beam builder capable of producing triangular cross section aluminum beams; and (2) design and fabrication of lap joints to connect the beams orthogonally and centroidal end caps to connect beams end to end at any desired angle. The first project produced a beam building machine which fabricates aluminum beams suitable for neutral buoyancy evaluation. The second project produced concepts for the lap joint and end cap. However, neither of these joint concepts was suitable for use by a pressure suited crew member in a zero gravity environment. It is concluded that before the beams can be evaluated the joint designs need to be completed and sufficient joints produced to allow assembly of a complex structure.

Pruett, E. C.↗
NASA NTRS1973

Transient ion neutralization by electrons.

The nonlinear initial-boundary-value problems describing the lateral neutralization of ion beams for the cases that (1) an auxiliary electric field accelerates the electrons into the ion space, and (2) the electrons are injected into the ion space at a prescribed current density are treated. Analytical solutions are derived which give the position and speed of the neutralization front as a function of time, and the temporal development of the electron density, velocity, and electric fields during the neutralization process.

Wilhelm, H. E.↗
NASA NTRS1996

Investigation of ion-beam machining methods for replicated x-ray optics

The final figuring step in the fabrication of an optical component involves imparting a specified contour onto the surface. This can be expensive and time consuming step. The recent development of ion beam figuring provides a method for performing the figuring process with advantages over standard mechanical methods. Ion figuring has proven effective in figuring large optical components. The process of ion beam figuring removes material by transferring kinetic energy from impinging neutral particles. The process utilizes a Kaufman type ion source, where a plasma is generated in a discharge chamber by controlled electric potentials. Charged grids extract and accelerate ions from the chamber. The accelerated ions form a directional beam. A neutralizer outside the accelerator grids supplies electrons to the positive ion beam. It is necessary to neutralize the beam to prevent charging workpieces and to avoid bending the beam with extraneous electro-magnetic fields. When the directed beam strikes the workpiece, material sputters in a predicable manner. The amount and distribution of material sputtered is a function of the energy of the beam, material of the component, distance from the workpiece, and angle of incidence of the beam. The figuring method described here assumes a constant beam removal, so that the process can be represented by a convolution operation. A fixed beam energy maintains a constant sputtering rate. This temporally and spatially stable beam is held perpendicular to the workpiece at a fixed distance. For non-constant removal, corrections would be required to model the process as a convolution operation. Specific figures (contours) are achieved by rastering the beam over the workpiece at varying velocities. A unique deconvolution is performed, using series-derivative solution developed for the system, to determine these velocities.

Drueding, Thomas W.↗
NASA NTRS2014

Design and Preliminary Performance Testing of Electronegative Gas Plasma Thruster

In classical gridded electrostatic ion thrusters, positively charged ions are generated from a plasma discharge of noble gas propellant and accelerated to provide thrust. To maintain overall charge balance on the propulsion system, a separate electron source is required to neutralize the ion beam as it exits the thruster. However, if high-electronegativity propellant gases (e.g., sulfur hexafluoride) are instead used, a plasma discharge can result consisting of both positively and negatively charged ions. Extracting such electronegative plasma species for thrust generation (e.g., with time-varying, bipolar ion optics) would eliminate the need for a separate neutralizer cathode subsystem. In addition for thrusters utilizing a RF plasma discharge, further simplification of the ion thruster power system may be possible by also using the RF power supply to bias the ion optics. Recently, the PEGASES (Plasma propulsion with Electronegative gases) thruster prototype successfully demonstrated proof-of-concept operations in alternatively accelerating positively and negatively charged ions from a RF discharge of a mixture of argon and sulfur hexafluoride.i In collaboration with NASA Marshall Space Flight Center (MSFC), the Georgia Institute of Technology High-Power Electric Propulsion Laboratory (HPEPL) is applying the lessons learned from PEGASES design and testing to develop a new thruster prototype. This prototype will incorporate design improvements and undergo gridless operational testing and diagnostics checkout at HPEPL in April 2014. Performance mapping with ion optics will be conducted at NASA MSFC starting in May 2014. The proposed paper discusses the design and preliminary performance testing of this electronegative gas plasma thruster prototype.

Liu, Thomas M.↗
NASA NTRS1990

Physics of the outer heliosphere; Proceedings of the 1st COSPAR Colloquium, Warsaw, Poland, Sept. 19-22, 1989

This volume includes chapters on spectroscopic data on the local interstellar medium and the related XUV radiation background; solar UV backscatter on neutral Galactic gases; entry and dynamics of Galactic and anomalous cosmic rays in the heliosphere; distant solar wind plasma, magnetic field, and solar energetic particles; the interaction of solar wind with the interstellar medium; and deep-space missions. Papers are on the characteristics and the velocity structure of the local interstellar medium, the scattering of solar UV on local neutral gases, solar effects on underground muons at 570 hg/sq cm, and cosmic rays and magnetosonic instabilities of solar wind flow near the heliospheric shock wave. Consideration is also given to the shock heating of the solar wind plasma, solar wind vortex flow in the outer heliosphere, the signature of a viscous interaction at the heliopause, the expected beams of energetic neutral atoms in the outer heliosphere, and the Pioneers 10 and 11 deep-space missions.

Grzedzielski, S.↗
NASA NTRS1985

Ignition of beam plasma discharge in the electron beam experiment in space

An ignition of beam plasma discharge (BPD) in space was observed in a neutral gas-electron beam interaction experiment by Space Shuttle/Spacelab-1 in 1983. An electron beam of 8 kV 100 mA was injected into a high dense nitrogen gas cloud of 10 to the 23rd molecules which was released during 100 msec from the Orbiter. The appearance of the beam and its surroundings observed by a low-light-level TV camera showed a local ignition of the beam plasma discharge in the gas cloud. The enhanced plasma production, generation of auroral emission, and associated wave emission were also detected by onboard diagnostic instruments.

Sasaki, S.↗
NASA NTRS1981

Neutral buoyancy test results of a deployable space beam

Large erectable and deployable space structures have been studied extensively in the past few years with a view toward usage in the near future for space platforms. The paper covers in particular the operational testing of a double-cell, double-folding cubic aluminum module at the Marshall Space Flight Center Neutral Buoyancy Simulator. Joining methods, deployment kinematics, configurations and operation time lines were analyzed using the Shuttle Remote Manipulator System (RMS) and EVA crewmen. Results of the test were considered successful, with crew tasks accomplished and the structural design adequate for flight design.

Stokes, J. W.↗
NASA NTRS1987

Martin Marietta atomic oxygen Low Earth Orbit (LEO) simulation

An atomic oxygen beam apparatus that produces flux levels and atomic kinetic energy similar to that encountered by spacecraft in low Earth orbit (LEO) is described. The beam apparatus consists of an electric discharge ion source, mass filter, decelerator, and neutralizer. Specific design goals include a 1.3 cm beam diameter, a 5 eV beam energy, and a flux density on the order of 10(15) cm(-2) s(-1). The total fluence will be on the order of 10(19) cm(-2) for an 8 hour test. The neutral oxygen beam will expose various materials contained within a large target chamber. Within the chamber will be a rather complex suite of instrumentation that will allow real-time studies of material mass loss and reactant species spatial distribution. In addition, a UV solar simulator will aid in the understanding of various synergistic effects.

Sjolander, Gary W.↗