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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Enhanced beam coupling modulation using the polarization properties of photorefractive GaAs

Observation is reported of a rotation in the polarization of the two photorefractive recording beams in GaAs for a configuration with the internally generated space-charge field along the line 110 crystallographic orientation. This rotation is a result of simultaneous constructive and destructive beam coupling in each beam for the optical electric field components along the two electrooptically induced principal dielectric axes of the crystal. By turning one of the beams on and off, the intensity of the other beam after the crystal and a polarization analyzer can be modulated by as much as 500 percent. This result is of particular importance for optical information processing applications.

Partovi, Afshin↗
NASA NTRS2006

A study of spacecraft charging due to exposure to interplanetary protons

The majority of research regarding IESD has been concerned with the electrons in the space environment around the Earth and at Jupiter; little research has been done on the charging of spacecraft in interplanetary space due to solar event protons. This paper provides a review of the literature regarding IESD due to protons and presents the results of recent laboratory experiments.

spacecraft charging↗
NASA NTRS2007

Validation of ISS Floating Potential Measurement Unit Electron Densities and Temperatures

Validation of the Floating Potential Measurement Unit (FPMU) electron density and temperature measurements is an important step in the process of evaluating International Space Station spacecraft charging issues .including vehicle arcing and hazards to crew during extravehicular activities. The highest potentials observed on Space Station are due to the combined VxB effects on a large spacecraft and the collection of ionospheric electron and ion currents by the 160 V US solar array modules. Ionospheric electron environments are needed for input to the ISS spacecraft charging models used to predict the severity and frequency of occurrence of ISS charging hazards. Validation of these charging models requires comparing their predictions with measured FPMU values. Of course, the FPMU measurements themselves must also be validated independently for use in manned flight safety work. This presentation compares electron density and temperatures derived from the FPMU Langmuir probes and Plasma Impedance Probe against the independent density and temperature measurements from ultraviolet imagers, ground based incoherent scatter radar, and ionosonde sites.

Coffey, Victoria N.↗
NASA NTRS2014

Characteristics of Extreme Auroral Charging Events

The highest level spacecraft charging observed in low Earth orbit (LEO) occurs when spacecraft are exposed to energetic auroral electrons. Since auroral charging has been identified as a mechanism responsible for on-orbit anomalies and even possible satellite failures it is important to consider extreme auroral charging events as design and test environments for spacecraft to be used in high inclination LEO orbits. This paper will report on studies of extreme auroral charging events using data from the SSJ/4 and SSJ/5 precipitating electron and ion sensors on the Defense Meteorology Satellite Program (DMSP) satellites. Early studies of DMSP charging to negative potentials ≥100 V focused on statistics of the electron environment responsible for charging. Later statistical studies of auroral charging have generally focused on solar cycle dependence of charging behavior and magnitude of the maximum potential and duration of the charging events. We extend these studies to focus on more detailed investigations of extreme charging event characteristics that are required to evaluate potential threats to spacecraft systems. A collection of example auroral charging events is assembled from the DMSP data set using the criteria that "extreme auroral charging" is defined as periods with spacecraft negative potentials ≥400 V. Specific characteristics to be treated include (but are not limited to) maximum and mean potentials, time history of spacecraft potentials through the events, total charging duration and the time potentials exceed voltage thresholds, frame charging/discharging rates, and information on geographic and geomagnetic latitudes at which the events are observed. Finally, we will comment on the implications of these studies for potential auroral charging risks to the International Space Station.

Minow, Joseph I.↗
NASA NTRS2015

Electrostatic Model Applied to ISS Charged Water Droplet Experiment

The electrostatic force can be used to create novel relative motion between charged bodies if it can be isolated from the stronger gravitational and dissipative forces. Recently, Coulomb orbital motion was demonstrated on the International Space Station by releasing charged water droplets in the vicinity of a charged knitting needle. In this investigation, the Multi-Sphere Method, an electrostatic model developed to study active spacecraft position control by Coulomb charging, is used to simulate the complex orbital motion of the droplets. When atmospheric drag is introduced, the simulated motion closely mimics that seen in the video footage of the experiment. The electrostatic force's inverse dependency on separation distance near the center of the needle lends itself to analytic predictions of the radial motion.

Stevenson, Daan↗
NASA NTRS2005

Experimentally derived resistivity for dielectric samples from the CRRES internal discharge monitor

Resistivity values were experimentally determined using charge storage methods for six samples remaining from the construction of the Internal Discharge Monitor (IDM) flown on the Combined Release and Radiation Effects Satellite (CRRES). Three tests were performed over a period of four to five weeks each in a vacuum of -5x10^-6 torr with an average temperature of -25 (deg)C to simulate a space environment.

spacecraft charging↗
NASA NTRS1979

On the charge polarization of cosmic systems

The positive electric charge density associated with the internal electric fields of self-gravitating systems in hydrostatic equilibrium can be canceled by nearby external flowing plasmas, such as winds. For example, it can be shown that the positive electric charge of a star is likely to be completely screened by its stellar wind. Because winds and other nonstatic phenomena are widespread, the electrical polarization due to the positive charge on static systems such as stars should occur on relatively local scales, in contrast to the universal scale recently suggested by Bally and Harrison. The latter viewpoint would be correct only if the entire universe were in strict hydrostatic equilibrium.

Barnes, A.↗
NASA NTRS2003

Comparison of On-orbit and Ground Based Hollow Cathode Operation

The Plasma Contactor Units (PCUs) were developed at NASA Glenn Research Center (GRC) and Boeing for charge control on board the International Space Station (ISS). Since the first ignition of a PCU on 10/16/2000 over 3,900 hours of operation have been demonstrated on a single unit. In order to guarantee that the PCUs hollow cathode assemblies (HCAs), which emit the electrons used for charge control, would satisfy the life requirement of 18,000 hours, a ground based hollow cathode life test program was initiated at GRC. The life test program aimed at 27,000 hours of operation on a single unit to demonstrate the industry standard 1.5 times operational life requirement. As of this printing, over 18,000 hours of operation have been accumulated on a single hollow cathode. By comparing the data received from the on-orbit HCAs to the data obtained for the life test cathodes, a comparison may be drawn to determine if the on-orbit HCAs are operating normally, with a final goal of predicting lifetime. Based on the data taken thus far, it can be concluded that the on-orbit HCAs are operating within their design specifications.

Patterson, Michael↗
NASA NTRS1978

Spin-related magnetism of interstellar grains

The magnetic dipole moments and internal magnetic fields due to the spin of electrically charged elongated nonmagnetic interstellar grains in kinetic equilibrium with their surroundings are computed for the grain-size range from 0.01 to 1.0 micron. It is shown that the induced magnetic moments and internal magnetic fields of charged spinning nonmagnetic grains of arbitrary composition and prolate spheroidal shape can be appreciable, possibly even exceeding 0.01 emu/cu cm for 0.01-micron grains. The results indicate that virtually all grains smaller than 0.1 micron in mean diameter, and all elongated grains smaller than about 1 micron in length, are immersed in local magnetic fields due to spin that are much larger than the ambient galactic field. Some implications of this effect are discussed in relation to the polarization of starlight by aligned dust grains and the primordial remanent magnetization found in primitive carbonaceous chondrites.

Srnka, L. J.↗
NASA NTRS1972

Coupled nuclear spin relaxation and internal rotations in magnesium fluosilicate hexahydrate.

Both proton and fluorine nuclear spin-lattice relaxations have been studied by the 180- to 90-deg pulse method in magnesium fluosilicate hexahydrate at 25 and 13 MHz over the temperature range from 170 to 350 K. Observed nonexponential behavior of the nuclear magnetic relaxation is explained by internal rotations of the doubly charged negative fluosilicate ions and doubly charged positive magnesium hexahydrate ions.

Utton, D. B.↗
NASA NTRS1984

A comparison of lightning and nuclear electromagnetic pulse response of a helicopter

A numerical modeling technique is utilized to investigate the response of a UH-60A helicopter to both lightning and nuclear electromagnetic pulses (NEMP). The analytical approach involves the three-dimensional time domain finite-difference solutions of Maxwell's equations. Both the external currents and charges as well as the internal electromagnetic fields and cable responses are computed. Results of the analysis indicate that, in general, the short circuit current on internal cables is larger for lightning, whereas the open-circuit voltages are slightly higher for NEMP. The lightning response is highly dependent upon the rise time of the injected current as was expected. The analysis shows that a coupling levels to cables in a helicopter are 20 to 30 dB larger than those observed in fixed-wing aircraft.

C C Easterbrook↗
NASA NTRS1988

Plasma diagnostics package. Volume 1: OSS-1 section

This volume (1) of the Plasma Diagnostics Package (PDP) final science report contains a summary of all of the data reduction and scientific analyses which were performed using PDP data obtained on STS-3 as a part of the Office of Space Science first payload (OSS-1). This work was performed during the period of launch, March 22, l982, through June 30, l983. During this period the primary data reduction effort consisted of processing summary plots of the data received by the 14 instruments located on the PDP and submitting these data to the National Space Science Data Center (NSSDC). The scientific analyses during the performance period consisted of general studies which incorporated the results of several of the PDP's instruments, detailed studies which concentrated on data from only one or two of the instruments, and joint studies of beam-plasma interactions with the OSS-1 Fast Pulse Electron Generator (FPEG) of the Vehicle Charging and Potential Investigation (VCAP). Internal reports, published papers and oral presentations which involve PDP/OSS-1 data are listed in Sections 3 and 4. A PDP/OSS-1 scientific results meeting was held at the University of Iowa on April 19-20, 1983. This meeting was attended by most of the PDP and VCAP investigators and provided a forum for discussing and comparing the various results, particularly with regard to the shuttle orbiter environment. One of the most important functional objectives of the PDP on OSS-1 was to characterize the orbiter environment.

Pickett, Jolene S.↗
NASA NTRS1988

Plasma diagnostics package. Volume 2: Spacelab 2 section, part A

This volume (2), which consists of two parts (A and B), of the Plasma Diagnostics Package (PDP) Final Science Report contains a summary of all of the data reduction and scientific analyses which were performed using PDP data obtained on STS-51F as a part of the Spacelab 2 (SL-2) payload. This work was performed during the period of launch, July 29, l985, through June 30, l988. During this period the primary data reduction effort consisted of processing summary plots of the data received by 12 of the 14 instruments located on the PDP and submitting these data to the National Space Science Data Center (NSSDC). The scientific analyses during the performance period consisted of follow-up studies of shuttle orbiter environment and orbiter/ionosphere interactions and various plasma particle and wave studies which dealt with data taken when the PDP was on the Remote Manipulator System (RMS) arm and when the PDP was in free flight. Of particular interest during the RMS operations and free flight were the orbiter wake studies and joint studies of beam/plasma interactions with the SL-2 Fast Pulse Electron Generator (FPEG) of the Vehicle Charging and Potential Investigation (VCAP). Internal reports, published papers and presentations which involve PDP/SL-2 data are listed in Sections 3 and 4. A PDP/SL-2 scientific results meeting was held at the University of Iowa on June 10, l986. This meeting was attended by most of the PDP and VCAP investigators and provided a forum for discussing and comparing the various results, particularly with regard to the PDP free flight.

Pickett, Jolene S.↗
NASA NTRS1991

Naming the newly found landforms on Venus

The mapping of Venus is unique in the history of cartigraphy; never has so much territory been discovered and mapped in so short a period of time. Therefore, in the interest of international scientific communication, there is a unique urgency to the development of a system of names for surface features on Venus. The process began with the naming of features seen on radar images taken from Earth and continued through mapping expeditions of the U.S. and U.S.S.R. However, the Magellan Mission resolves features twenty-five times smaller than those mapped previously, and its radar data will cover an area nearly equivalent to that of the continents and the sea-floors of the Earth combined. The International Astronomical Union (IAU) was charged with the formal endorsement of names of features on the planets. Proposed names are collected, approved, and applied through the IAU Working Group for Planetary System Nomenclature (WGPSN) and its task groups, prior to IAU approval by the IAU General Assembly. Names approved by the WGPSN and its task groups, prior to final approval may be used on published maps and articles, provided that their provisional nature is stipulated. The IAU has established themes for the names to be used on each of the planets; names of historical and mythological women are used on Venus. Names of political entities and those identified with active religions are not acceptable, and a person must have been deceased for three years or more to be considered. Any interested person may propose a name for consideration by the IAU.

Batson, R. M.↗
NASA NTRS1991

Visualizing the thermal performance of heat pipes with thermochromic liquid crystals

A novel technique has been developed to visualized the thermal performance characteristics of simple low temperature heat pipes and thermosyphons. Copper heat pipes with internal, annular mesh wicks and charged with Refrigerant-12 were externally coated with thermochromic liquid crystal (TLC) paints. The thermally sensitive TLC coating reversibly changes color upon heating and readily permits visual identification of transient and steady state isotherms during low temperature operation. The start-up and operational behaviors of the heat pipe as well as the presence of non-condensible gases can be visually identified through a spectrum of color changes. A brief video demonstration illustrating heat pipe thermal performance characteristics has been developed and illustrates the utility of TLCs for visualizing thermal behavior.

Gunnerson, Fred S.↗
NASA NTRS2002

Comparison of graphite, aluminum, and TransHab shielding material characteristics in a high-energy neutron field

Space radiation transport models clearly show that low atomic weight materials provide a better shielding protection for interplanetary human missions than high atomic weight materials. These model studies have concentrated on shielding properties against charged particles. A light-weight, inflatable habitat module called TransHab was built and shown to provide adequate protection against micrometeoroid impacts and good shielding properties against charged particle radiation in the International Space Station orbits. An experiment using a tissue equivalent proportional counter, to study the changes in dose and lineal energy spectra with graphite, aluminum, and a TransHab build-up as shielding, was carried out at the Los Alamos Nuclear Science Center neutron facility. It is a continuation of a previous study using regolith and doped polyethylene materials. This paper describes the results and their comparison with the previous study. Published by Elsevier Science Ltd.

NASA Center JSC↗
NASA NTRS2015

Upwelling Radiance at 976 nm Measured from Space Using a CCD Camera

The Optical Payload for Lasercomm Science (OPALS) Flight System on-board the International Space Station uses a charge coupled device (CCD) camera for receiving a beacon laser from Earth. Relative measurements of the background contributed by upwelling radiance under diverse illumination conditions and varying terrain is presented. In some cases clouds in the field-of-view allowed a comparison of terrestrial and cloud-top upwelling radiance. In this paper we will report these measurements and examine the extent of agreement with atmospheric model predictions.

Biswas, Abhijit↗