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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Destruction of Interstellar Dust

Interstellar dust is an important component of the interstellar medium. Dust grains are the dominant opacity source and thus regulate the radiative transfer in the interstellar medium. Besides the spectral characteristics of sources, dust therefore influences directly the molecular composition of clouds through photodissociation and the heating of the gas through the photoelectric effect. Furthermore, dust grains also provide surfaces for active chemistry. This paper will review the destruction of interstellar dust with an emphasis on processing by interstellar shocks. Interstellar dust is affected by a variety of processes. Stars in the late stages of their evolution form dust grains by chemical nucleation and growth and injected them into the ISM. Grains in the ISM are processed by strong shock waves which sputter, vaporize, diamondize, and shatter them. The physics of interstellar shock waves and of these destruction processes will be reviewed. The ISM is organized in a number of phases: HI and molecular clouds, warm (neutral/ionized) intercloud medium, and coroner gas. Dust destruction is dominated by supernova shock waves in the intercloud medium. Because of rapid exchange of dust and gas between the phases, the effects of this are felt through all phases. This will be briefly discussed.

Tielens, A. G. G. M.↗
NASA NTRS2005

Instrumentation and Measurements for Electron Emission from Charged Insulators

The electron was first discovered in 1898 by Sir John Joseph Thomson and has since been the subject of detailed study by nearly every scientific discipline. At nearly the same time Heinrich Rudolf Hertz conducted a series of experiments using cathode tubes, high potentials and ultraviolet light. When applying a large potential to a cathode he found that an arching event across the metal plates would occur. In addition, when shining an ultraviolet light on the metal he found that less potential was required to induce the spark. This result, taken together with other electrical phenomena brought about by the shining of light upon metal and was eventually termed the photoelectric effect. The work of Thomson and Hertz represent the beginning of electron emission studies and a body of ideas that pervade nearly all aspects of physics. In particular these ideas tell us a great deal about the nature of physical interactions within solids. In this thesis we will focus on the emission of electrons induced by an incident electron source over a range of energies, in which one can observe changes in emitted electron flux and energy distribution. In particular, when energetic particles impinge on a solid they can impart their energy, exciting electrons within the material. If this energy is sufficient to overcome surface energy barriers such as the work function, electron affinity or surface charge potential, electrons can escape from the material. The extent of electron emission from the material can be quantified as the ratio of incident particle flux to emitted particle flux, and is termed the electron yield.

Sim, Alec M.↗
NASA NTRS2005

X-ray Polarimetry with a Micro-Pattern Gas Detector

Topics covered include: Science drivers for X-ray polarimetry; Previous X-ray polarimetry designs; The photoelectric effect and imaging tracks; Micro-pattern gas polarimeter design concept. Further work includes: Verify results against simulator; Optimize pressure and characterize different gases for a given energy band; Optimize voltages for resolution and sensitivity; Test meshes with 80 micron pitch; Characterize ASIC operation; and Quantify quantum efficiency for optimum polarization sensitivity.

Hill, Joe↗
NASA NTRS2007

A Burst Chasing X-ray Polarimeter

Gamma-ray bursts are one of the most powerful explosions in the universe and have been detected out to distances of almost 13 billion light years. The exact origin of these energetic explosions is still unknown but the resulting huge release of energy is thought to create a highly relativistic jet of material and a power-law distribution of electrons. There are several theories describing the origin of the prompt GRB emission that currently cannot be distinguished. Measurements of the linear polarization would provide unique and important constraints on the mechanisms thought to drive these powerful explosions. We present the design of a sensitive, and extremely versatile gamma-ray burst polarimeter. The instrument is a photoelectric polarimeter based on a time-projection chamber. The photoelectric time-projection technique combines high sensitivity with broad band-pass and is potentially the most powerful method between 2 and 100 keV where the photoelectric effect 1s the dominant interaction process We present measurements of polarized and unpolarized X-rays obtained with a prototype detector and describe the two mission concepts, the Gamma-Ray Burst Polarimeter (GRBP) for thc U S Naval Academy satellite MidSTAR-2, and thc Low Energy Polarimeter (LEP) onboard POET, a broadband polarimetry concept for a small explorer mission.

Hill, Joanne E.↗
NASA NTRS2007

A Burst Chasing X-ray Polarimeter

Tihs is a viewgraph presentation of a discussion of the X-ray Polarimeter. Gamma-ray bursts are one of the most powerful explosions in the universe and have been detected out to distances of almost 13 billion light years. The exact origin of these energetic explosions is still unknown but the resulting huge release of energy is thought to create a highly relativistic jet of material and a power-law distribution of electrons. There are several theories describing the origin of the prompt GRB emission that currently cannot be distinguished. Measurements of the linear polarization would provide unique and important constraints on the mechanisms thought to drive these powerful explosions. We present the design of a sensitive, and extremely versatile gamma-ray burst polarimeter. The instrument is a photoelectric polarimeter based on a time-projection chamber. The photoelectric time-projection technique combines high sensitivity with broad band-pass and is potentially the most powerful method between 2 and 100 keV where the photoelectric effect is the dominant interaction process We present measurements of polarized and unpolarized X-rays obtained with a prototype detector and describe the two mission concepts, the Gamma-Ray Burst Polarimeter (GRBP) for thc U S Naval Academy satellite MidSTAR-2, and thc Low Energy Polarimeter (LEP) onboard POET, a broadband polarimetry concept for a small explorer mission.

Hill, Joanne↗
NASA NTRS2010

Active Dust Control and Mitigation Technology for Lunar and Martian Exploration

Mars is covered with a layer of dust that has been homogenized by global dust storms. Dust, levitated by these storms as well as by the frequent dust devils, is the dominant weather phenomenon on Mars. NASA's Mars exploration rovers have shown that atmospheric dust falling on solar panels can decrease their efficiency to the point of rendering the rover unusable. Dust covering the surface of the moon is expected to be electrostatically charged due to the solar wind, cosmic rays, and the solar radiation itself through the photoelectric effect. Electrostatically charged dust has a large tendency to adhere to surfaces. The Apollo missions to the moon showed that lunar dust adhesion can hinder manned and unmanned exploration activities. In this paper, we report on our efforts to develop and electrodynamic dust shield to prevent the accumulation of dust on surfaces and to remove dust already adhering to those surfaces. The technology uses electrostatic and dielectrophoretic forces to carry dust particles off surfaces and to generate an electrodynamic shield that prevents further accumulation of dust. The concept of the electrodynamic dust shield was introduced by NASA in the late 1960s and later reduced to practice during the 1970s for terrestrial applications. In 2003, our laboratory, in collaboration with several universities, applied this technology to space applications, specifically to remove dust from solar panels on Mars. We show how, with an appropriate design, we can prevent the electrostatic breakdown at the low Martian atmospheric pressures. We are also able to show that uncharged dust can be lifted and removed from surfaces under simulated Martian environmental conditions. We have also been able to develop a version of the electrodynamic dust shield working under hard vacuum conditions that simulate the lunar environment. We have implemented the electrodynamic dust shield on solar arrays, optical systems, spectrometers, viewports, thermal radiators, batteries, and power systems, as well as on fabrics for spacesuits. We present data on the design and optimization of the electrodynamic dust shields and provide data on the performance of the different implementations of the technology for lunar and Martian exploration activities.

Calle, C. I.↗
NASA NTRS2011

The Electrostatic Environments of Mars and the Moon

The electrical activity present in the environment near the surfaces of Mars and the moon has very different origins and presents a challenge to manned and robotic planetary exploration missions. Mars is covered with a layer of dust that has been redistributed throughout the entire planet by global dust storms. Dust, levitated by these storms as well as by the frequent dust devils, is expected to be electrostatically charged due to the multiple grain collisions in the dust-laden atmosphere. Dust covering the surface of the moon is expected to be electrostatically charged due to the solar wind, cosmic rays, and the solar radiation itself through the photoelectric effect. Electrostatically charged dust has a large tendency to adhere to surfaces. NASA's Mars exploration rovers have shown that atmospheric dust falling on solar panels can decrease their efficiency to the point of rendering the rover unusable. And as the Apollo missions to the moon showed, lunar dust adhesion can hinder manned and unmanned lunar exploration activities. Taking advantage of the electrical activity on both planetary system bodies, dust removal technologies are now being developed that use electrostatic and dielectrophoretic forces to produce controlled dust motion. This paper presents a short review of the theoretical and semiempirical models that have been developed for the lunar and Martian electrical environments.

Calle, Carlos I.↗
NASA NTRS2011

X-Ray Polarimetry with GEMS

The polarization properties of cosmic X-ray sources are still largely unexplored. The Gravity and Extreme Magnetism SMEX (GEMS) will carry out the first sensitive X-ray polarization survey of a wide range of sources including; accreting compact objects (black holes and neutron stars), AGN, supernova remnants, magnetars and rotation-powered pulsars. GEMS employs grazing-incidence foil mirrors and novel time-projection chamber (TPC) polarimeters leveraging the photoelectric effect to achieve high polarization sensitivity in the 2 - 10 keV band. I will provide an update of the project status, illustrate the expected performance with several science examples, and provide a brief overview of the data analysis challenges

Strohmayer, Tod↗
NASA NTRS2011

Data Analysis And Polarization Measurements With GEMS

The Gravity and Extreme Magnetism SMEX (GEMS) mission was selected by NASA for flight in 2014. GEMS will make the first sensitive survey of X-ray polarization across a wide range of source classes including black hole and neutron star binaries, AGN of different types, rotation and accretion-powered pulsars, magnetars, shell supernova remnants and pulsar wind nebulae. GEMS employs grazing-incidence foil mirrors and novel time-projection chamber (TPC) polarimeters leveraging the photoelectric effect. The GEMS detectors image the charge tracks of photoelectrons produced by 2 - 10 keV X-rays. The initial direction of the photoelectron is determined by the linear polarization of the photon. We present an overview of the data analysis challenges and methods for GEMS, including procedures for producing optimally filtered images of the charge tracks and estimating their initial directions. We illustrate our methods using laboratory measurements of polarized and unpolarized X-rays with flight-like detectors as well as from simulated tracks. We also present detailed simulations exploring the statistics of polarization measurements appropriate for GEMS, and make comparisons with previous work.

Stohmayer, Tod↗
NASA NTRS2013

Chemical Enrichment and Physical Conditions in IZw18*

Low-metallicity star-forming dwarf galaxies are prime targets to understand the chemical enrichment of the interstellar medium. The H I region contains the bulk of the mass in blue compact dwarfs, and it provides important constraints on the dispersal and mixing of heavy elements released by successive star-formation episodes. The metallicity of the H I region is also a critical parameter to investigate the future star-formation history, as metals provide most of the gas cooling that will facilitate and sustain star formation. Aims. Our primary objective is to study the enrichment of the H I region and the interplay between star-formation history and metallicity evolution. Our secondary obje ctive is to constrain the spatial- and time-scales over which the HI and H II regions are enriched, and the mass range of stars responsible for the heavy element production. Finally, we aim to examine the gas heating and cooling mechanisms in the H I region. Methods. We observed the most metal-poor star-forming galaxy in the Local Universe, I Zw 18, with the Cosmic Origin Spectrograph onboard Hubble. The abundances in the neutral gas are derived from far-ultraviolet absorption-lines (H I, CIII, CIIi*, N I, OI,...) and are compared to the abundances in the H II region. Models are constructed to calculate the ionization structure and the thermal processes. We investigate the gas cooling in the HIi region through physical diagnostics drawn from the fine-structure level of C+. Results. We find that H I region abundances are lower by a factor of approx 2 as compared to the H II region. There is no differential depletion on dust between the H I and H II region. Using sulfur as a metallicity tracer, we calculate a metallicity of 1/46 Z(solar) (vs. 1/31 Z(solar) in the H II region). From the study of the C/O, [O/Fe], and N/O abundance ratios, we propose that C, N, O, and Fe are mainly produced in massive stars. We argue that the H I envelope may contain pockets of pristine gas with a metallicity essentially null. Finally, we derive the physical conditions in the H I region by investigating the C II* absorption line. The cooling rate derived from C II* is consistent with collisions with H(sup 0) atoms in the diffuse neutral gas. We calculate the star-formation rate from the CII* cooling rate assuming that photoelectric effect on dust is the dominant gas heating mechanism. Our determination is in good agreement with the values in the literature if we assume a low dust-to-gas ratio (approx 2000 times lower than the Milky Way value).

far-ultraviolet absorption-lines↗
NASA NTRS2015

A Triboelectric Sensor Array for Electrostatic Studies on the Lunar Surface

The moons electrostatic environment requires careful consideration in the development of future lunar landers. Electrostatically charged dust was well documented during the Apollo missions to cause thermal control, mechanical, and visibility issues. The fine dust particles that make up the surface are electrostatically charged as a result of numerous charging mechanisms. The relatively dry conditions on the moon creates a prime tribocharging environment during surface operations. The photoelectric effect is dominant for lunar day static charging, while plasma electrons are the main contributor for lunar night electrostatic effects. Electrostatic charging is also dependent on solar intensity, Earth-moon relative positions, and cosmic ray flux. This leads to a very complex and dynamic electrostatic environment that must be studied for the success of long term lunar missions.In order to better understand the electrostatic environment of planetary bodies, Kennedy Space Center, in previous collaboration with the Jet Propulsion Laboratory, has developed an electrostatic sensor suite. One of the instruments included in this package is the triboelectric sensor array. It is comprised of strategically selected materials that span the triboelectric series and that also have previous spaceflight history. In this presentation, we discuss detailed testing with the triboelectric sensor array performed at Kennedy Space Center. We will discuss potential benefits and use cases of this low mass, low cost sensor package, both for science and for mission success.

Charging↗
NASA NTRSDate not supplied

Improving the transient sensitivity of AMEGO-X using single-site events

AMEGO-X is a proposed Compton/pair telescope which will image and survey the medium-energy gamma-ray sky between 100 keV and 1 GeV. It is designed to detect and characterize gamma-ray emission from multi-messenger sources. On short time scales (<100s), including information from single-site events (photoelectric effect interactions)significantly increases AMEGO-X's sensitivity and lowers its energy threshold down to 25 keV. In this presentation, we will present AMEGO-X's sensitivity to transient events such as gamma-ray bursts and magnetar giant flares, and discuss the improvements due to the inclusion of single-site events. We will also discuss AMEGO-X's ability to localize transient sources and alert the community for follow-up observations.

Henrike Fleischhack↗
NASA NTRSDate not supplied

Improving the Transient Sensitivity of AMEGO-X Using Single-site Events

AMEGO-X is a Compton/pair gamma-ray telescope, submitted to NASA's 2021 MIDEX AO, which will image and survey the medium-energy gamma-ray sky between 100 keV and 1 GeV. It is designed to detect and characterize gamma-ray emission from multi-messenger sources. On short time scales (<100s), including information from single-site events (photoelectric effect interactions) significantly increases AMEGO-X's sensitivity and lowers its energy threshold down to 25 keV. In this presentation, we will present AMEGO-X's sensitivity to transient events such as gamma-ray bursts and magnetar giant flares, and discuss the improvements due to the inclusion of single-site events. We will also discuss AMEGO-X's ability to localize transient sources and alert the community for follow-up observations.

Henrike Fleischhack↗
NASA NTRSDate not supplied

NASA’s Handheld Ionizer Tool for Astronauts

NASA’s next human lunar mission will require handheld tools to eliminate dust accumulation as well as electrostatic charge for the upcoming manned missions to the moon in the Artemis Program. The Moon’s lack of substantial atmosphere means the lunar surface is directly exposed to the solar wind, solar UV radiation, and cosmic rays which can cause dielectric charging of the lunar regolith via the photoelectric effect. The result is a layer of highly charged dust that is levitated and transported about a meter off the surface called the “horizon glow” as seen by the Apollo astronauts. The complex lunar electrostatic environment coupled with the surface dust behavior poses a concern for the longevity of surface infrastructures. The Electrostatics and Surface Physics Laboratory at NASA’S Kennedy Space Center retrofitted a commercial ionizer and successfully demonstrated that air ionizers are effective at removing dust particles and the static charge in high vacuum. Additional work is planned to establish the optimal voltage and flow characteristic to develop a high-fidelity ground prototype for future flight certification.

Electrostatics↗
NASA NTRSDate not supplied

Where Lies the Quantumness Behind Detecting Electromagnetic Waves for Frequencies from Infrared and Up?

The synthesis of Newtonian concept of corpuscles during emission with Huygens’ concept of secondary-wavelets during propagation implies that all EM radiations from quantized atoms and molecules are released as discrete amount of energies. However, they propagate out as time-finite Maxwellian light pulses. Huygens also underscored that his secondary wavelets keep propagating as independent pulses in the absence of any interacting medium, or until intercepted by an interface with a medium or a detector. Then we use the Superposition Principle and the coherence theory to derive Einstein’s photoelectric equation by summing innumerable random time-finite pulses. This process driven approach should yield the characteristic statistical variations of photoelectron current pulses, as generated by photodetectors for different kinds of light sources. Lamb & Scully originally proposed this semiclassical approach without assuming that light actually consists of time finite pulses. The quantumness remains confined within the excitation and de-excitations processes in the material particles.

Electromagnetic Waves↗
NASA NTRS1990

An imaging photoemission polarimeter for soft X-rays

Results of investigations are reviewed to assess the polarization dependence of photoemission in the optical, UV, and soft X-ray bands, as well as present a design for an imaging photoelectric polarimeter. Data regarding the effect of the dependence in the soft X-ray band are emphasized including the quantity of photons produced by each X-ray. The phase shift encountered in some experiments indicates that a third axis is present; the importance of the phase shift in understanding the vectoral photoeffect is emphasized. Measurements of the pulse height show that this measure is proportional to the number of electrons photoemitted by the incident X-ray. The development of X-ray polarimeters can be significantly improved as a result of the study of polarization sensitivity in the photoelectric effect. The design of a photoelectric polarimeter is presented, and the potential uses for the instrument include measuring the polarization of supernova remnants, AGN, and black hole candidates.

Kaaret, Philip↗