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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

Study of the Effects of the Electric Field on Charging Measurements on Individual Micron-size Dust Grains by Secondary Electron Emissions

The dust charging by electron impact is an important dust charging process in Astrophysical, Planetary, and the Lunar environments. Low energy electrons are reflected or stick to the grains charging the dust grains negatively. At sufficiently high energies electrons penetrate the grain leading to excitation and emission of electrons referred to as secondary electron emission (SEE). Available theoretical models for the calculation of SEE yield applicable for neutral, planar or bulk surfaces are generally based on Sternglass Equation. However, viable models for charging of individual dust grains do not exist at the present time. Therefore, the SEE yields have to be obtained by some experimental methods at the present time. We have conducted experimental studies on charging of individual micron size dust grains in simulated space environments using an electrodynamic balance (EDB) facility at NASA-MSFC. The results of our extensive laboratory study of charging of individual micron-size dust grains by low energy electron impact indicate that the SEE by electron impact is a very complex process expected to be substantially different from the bulk materials. It was found that the incident electrons may lead to positive or negative charging of dust grains depending upon the grain size, surface potential, electron energy, electron flux, grain composition, and configuration. In this paper we give a more elaborate discussion about the possible effects of the AC field in the EDB on dust charging measurements by comparing the secondary electron emission time-period (tau (sub em) (s/e)) with the time-period (tau (sub ac) (ms)) of the AC field cycle in the EDB that we have briefly addressed in our previous publication.

Tankosic, D.↗
NASA NTRS2011

Improving Single Event Effects Testing Through Software

Radiation encountered in space environments can be damaging to microelectronics and potentially cause spacecraft failure. Single event effects (SEE) are a type of radiation effect that occur when an ion strikes a device. Single event gate rupture (SEGR) is a type of SEE that can cause failure in power transistors. Unlike other SEE rates in which a constant linear energy transfer (LET) can be used, SEGR rates sometimes require a non-uniform LET to be used to be accurate. A recent analysis shows that SEGR rates are most easily calculated when the environment is described as a stopping rate per unit volume for each ion species. Stopping rates in silicon for pertinent ions were calculated using the Stopping and Range of Ions in Matter (SRIM) software and CREME-MC software. A reference table was generated and can be used by others to calculate SEGR rates for a candidate device. Additionally, lasers can be used to simulate SEEs, providing more control and information at lower cost than heavy ion testing. The electron/hole pair generation rate from a laser pulse in a semiconductor can be related to the LET of an ion. MATLAB was used to generate a plot to easily make this comparison.

generation equation↗
NASA NTRS2015

[Redesign of the Spacesuit Long Life Battery and the Personal Life Support System Battery]

This fall I was working on two different projects that culminated into a redesign of the spacesuit LLB (long life battery). I also did some work on the PLSS (personal life support system) battery with EC. My first project was redlining the work instruction for completing DPAs (destructive physical analysis) on battery cells in the department. The purpose of this document is to create a standard process and ensure that the data in the same way no matter who carries out the analysis. I observed three DPAs, conducted one with help, and conducted two on my own all while taking notes on the procedure. These notes were used to write the final work instruction that will become is the department standard. My second project continued the work of the summer co-op before me. I was testing aluminum heat sinks for their ability to provide good thermal conduction and structural support during a thermal runaway event. The heat sinks were designed by the summer intern but there was not much time for testing before he left. We ran tests with a heater on the bottom of a trigger cell to try to drive thermal runaway and ensure that it will not propagate to adjacent cells. We also ran heat-to-vent tests in an oven to see if the assembly provided structural support and prevented sidewall rupture during thermal runaway. These tests were carried out at ESTA (energy systems test area) and are providing very promising results that safe, high performing (greater than 180 Wh/kg) designs are possible. My main project was a redesign of the LLB battery. Another summer intern did some testing and concluded that there was no simple fix to mitigate thermal runaway propagation hazards in the current design. The only option was a clean sheet redesign of the battery. I was given a volume and ideal energy density and the rest of the design was up to me. First, I created new heat sink banks in Creo using the information gathered in the metal heat sink tests from the summer intern. After this, I made capture plates to hold the cells in place and I worked on nickel bussings for the electrical connections between the cells. Finally, I designed the test box enclosure that included sections for flame arresting materials. The battery brick design, which is the heart of the battery, promises to become the first for a manned spacecraft application to achieve greater than 180 Wh/kg. My work in redlining the DPA work instructions will also be used in selecting the cells for the battery. We had a few options of cells that would provide the necessary power output and needed to make a choice. We repeatedly charged and discharged cells for around a month until they went through 100 lifecycles. The plan is to compare the DPA results on fresh and cycled cells from each manufacturer to see if cycling introduces any differences. After the complete LLB design was approved, the parts were ordered and testing should begin the first week of December. Some of my side projects included working on the CAD data for the PLSS with EC and attending the NASA Aerospace Battery Workshop in Huntsville. I was also a member of the Tours and Lectures Committee for the USRA and Pathways interns. I coordinated Apollo Evening and was on the committee for touring KSC and seeing an Atlas 5 launch. I really enjoyed my time at JSC and I would like to continue working for NASA or another aerospace company in the future. I have worked other internships prior to this, but I think the heavy research and development focus is the best fit for me. I originally thought I would need to go to grad school to work in an environment like this, but I now see it is possible with a bachelor’s degree and hard work. I would like to go into the workforce and maybe continue my education with night classes.

Scharf, Stephanie↗
NASA NTRS2010

Localized Triple Modular Redundancy vs. Distributed Triple Modular Redundancy on a ProASIC3E Reprogrammable FPGA

Field programmable gate arrays (FPGA) are used in every space application. Currently, most space flight applications use radiation hardened (RH) FPGAs, which are very expensive. There is a desire to use cheaper, commercial off the shelf reprogrammable FPGAs, which are more susceptible to radiation effects known as single-event effects (SEE). The RH parts have SEE and total ionizing dose (TID) hardened elements pre-integrated into the part. This means that the designer does not need to implement any hardening techniques while configuring the device. The COTS parts on the other hand must be mitigated by design in order to insure any form of mitigation. The design techniques this project examines concern the use of localized triple modular redundancy (LTMR) and distributed triple modular redundancy (DTMR). LTMR triples every flip flop in the device architecture while DTMR triples everything except for the global routes (clocks, resets, and enables). The testing was performed on a ProASIC3E FPGA at the Texas A&M cyclotron facility. Two design architectures were used: shift registers and counters, both with LTMR and DTMR mitigation techniques. The test results prove that DTMR is more effective at reducing SEE than LTMR. We also determined that there was not a significant difference between the use of shift registers and counters for test purposes. More testing is required to obtain additional linear energy transfer values for each architecture and mitigation technique in order to determine the most cost-effective method of SEE mitigation.

McGuffey, Alex↗
NASA NTRS2020

SISO Space Reference FOM - Tools and Testing

The Simulation Interoperability Standards Organization (SISO) Space Reference Federation Object Model (SpaceFOM) version 1.0 is nearing completion. Earlier papers have described the use of the High Level Architecture (HLA) in Space simulation as well as technical aspects of the SpaceFOM. This paper takes a look at different SpaceFOM tools and how they were used during the development and testing of the standard.The first organizations to develop SpaceFOM-compliant federates for SpaceFOM development and testing were NASA's Johnson Space Center (JSC), the University of Calabria (UNICAL), and Pitch Technologies.JSC is one of NASA's lead centers for human space flight. Much of the core distributed simulation technology development, specifically associated with the SpaceFOM, is done by the NASA Exploration Systems Simulations (NExSyS) team. One of NASA's principal simulation development tools is the Trick Simulation Environment. NASA's NExSyS team has been modifying and using Trick and TrickHLA to help develop and test the SpaceFOM.The System Modeling And Simulation Hub Laboratory (SMASH-Lab) at UNICAL has developed the Simulation Exploration Experience (SEE) HLA Starter kit, that has been used by most SEE teams involved in the distributed simulation of a Moon base. It is particularly useful for the development of federates that are compatible with the SpaceFOM. The HLA Starter Kit is a Java based tool that provides a well-structured framework to simplify the formulation, generation, and execution of SpaceFOM-compliant federates.Pitch Technologies, a company specializing in distributed simulation, is utilizing a number of their existing HLA tools to support development and testing of the SpaceFOM. In addition to the existing tools, Pitch has developed a few SpaceFOM specific federates: Space Master for managing the initialization, execution and pacing of any SpaceFOM federation; EarthEnvironment, a simple Root Reference Publisher; and Space Monitor, a graphical tool for monitoring reference frames and physical entities.Early testing of the SpaceFOM was carried out in the SEE university outreach program, initiated in SISO. Students were given a subset of the FOM, that was later extended. Sample federates were developed and frameworks were developed or adapted to the early FOM versions.As drafts of the standard matured, testing was performed using federates from government, industry, and academia. By mixing federates developed by different teams the standard could be tested with respect to functional correctness, robustness and clarity.These frameworks and federates have been useful when testing and verifying the design of the standard. In addition to this, they have since formed a starting point for developing SpaceFOM-compliant federations in several projects, for example for NASA, ESA as well as SEE.

Möller, Björn↗
NASA NTRS2022

Requirements for Progress in Understanding Solar Flare Energy Transport: The Gradual Phase

Solar flares are a fundamental component of solar eruptive events (SEEs), along with solar energetic particles (SEPs) and coronal mass ejections (CMEs). Flare emission is the first component of a SEE to impact the Earth’s atmosphere which can set the stage for the later arrival of the associated SEPs, CME, and space weather event. Magnetic reconnection drives SEEs by restructuring the solar coronal magnetic field, liberating a tremendous amount of energy which is partitioned into various physical manifestations: particle acceleration, mass and magnetic-field eruption, atmospheric heating, and the subsequent emission of radiation as solar flares. In this white paper we discuss the observational and theoretical advances required in order to make substantial progress in understanding the physical processes acting during the gradual phase of a flare. That is, the decay period, following the initial rapid release of energy during the impulsive phase (see our other white paper). In particular we want to address the unknown processes that sustain the long decay phase of flares and identify the unknown mechanism and magnitude of continued energy injection during the gradual phase.

Graham S Kerr↗
NASA NTRS2017

Recent Radiation Test Results for Trench Power MOSFETs

Single-event effect (SEE) radiation test results are presented for various trench-gate power MOSFETs. The heavy-ion response of the first (and only) radiation-hardened trench-gate power MOSFET is evaluated: the manufacturer SEE response curve is verified and importantly, no localized dosing effects are measured, distinguishing it from other, non-hardened trench-gate power MOSFETs. Evaluations are made of n-type commercial and both n- and p-type automotive grade trench-gate device using ions comparable to of those on the low linear energy transfer (LET) side of the iron knee of the galactic cosmic ray spectrum, to explore suitability of these parts for missions with higher risk tolerance and shorter duration, such as CubeSats. Part-to-part variability of SEE threshold suggests testing with larger sample sizes and applying more aggressive derating to avoid on-orbit failures. The n-type devices yielded expected localized dosing effects including when irradiated in an unbiased (0-V) configuration, adding to the challenge of inserting these parts into space flight missions.

Schottky Diodes↗
NASA NTRS2018

NASA Electronic Parts and Packaging Field Programmable Gate Array Single Event Effects Test Guideline Update

The following are updated or new subjects added to the FPGA SEE Test Guidelines manual: academic versus mission specific device evaluation, single event latch-up (SEL) test and analysis, SEE response visibility enhancement during radiation testing, mitigation evaluation (embedded and user-implemented), unreliable design and its affects to SEE Data, testing flushable architectures versus non-flushable architectures, intellectual property core (IP Core) test and evaluation (addresses embedded and user-inserted), heavy-ion energy and linear energy transfer (LET) selection, proton versus heavy-ion testing, fault injection, mean fluence to failure analysis, and mission specific system-level single event upset (SEU) response prediction. Most sections within the guidelines manual provide information regarding best practices for test structure and test system development. The scope of this manual addresses academic versus mission specific device evaluation and visibility enhancement in IP Core testing.

Field Programmable Gate Array (FPGA)↗
NASA NTRSDate not supplied

Assistive Detect and Avoid Technology in Urban Air Mobility Environments

The use of Assistive Detect and Avoid (Assistive DAA or ADAA) technology in Urban Air Mobility (UAM) environments poses potential benefits as well as challenges. Assistive DAA refers to the leveraged use of DAA technology, originally developed to replace see-and-avoid capabilities for remotely piloted aircraft, in onboard-piloted aircraft to augment (rather than replace) pilots’ see-and-avoid abilities and thus enhance the safety and efficiency of visual flight operations. ADAA is anticipated to be especially safety-enhancing in airspace where traffic density is high or traditional air traffic services are limited, such as in future UAM environments. ADAA may also enable higher-tempo UAM operations than with only see-and-avoid capabilities, while still maintaining acceptable levels of safety. UAM concepts under development by the FAA, NASA, and industry focus on operations moving people and cargo in urban and suburban areas using innovative technologies, operations, and aircraft, including electric vertical takeoff and landing (eVTOL) aircraft. Researchers at NASA Langley Research Center, in collaboration with FAA researchers at the William J. Hughes Technical Center in Atlantic City, NJ, have conducted a series of medium-fidelity, human-in-the-loop research simulations of potential future UAM operations and concepts in both Class C and Class B airspace environments. These simulations have included use of a Langley-developed ADAA research tool called DANTi, which enables configurable ADAA displays to be presented to pilots of simulated eVTOL aircraft participating in higher-density and higher-tempo UAM operations. Experience and observations made during testing of the NASA-developed DANTi ADAA capability in the UAM NFLITE simulation environment will be reported in this paper together with a discussion of airspace integration and regulatory topics.

Detect and Avoid↗
NASA NTRSDate not supplied

Assistive Detect and Avoid Technology in Urban Air Mobility Environments

The use of Assistive Detect and Avoid (Assistive DAA or ADAA) technology in Urban Air Mobility (UAM) environments poses potential benefits as well as challenges. Assistive DAA refers to the leveraged use of DAA technology, originally developed to replace see-and-avoid capabilities for remotely piloted aircraft, in onboard-piloted aircraft to augment (rather than replace) pilots’ see-and-avoid abilities and thus enhance the safety and efficiency of visual flight operations. ADAA is anticipated to be especially safety-enhancing in airspace where traffic density is high or traditional air traffic services are limited, such as in future UAM environments. ADAA may also enable higher-tempo UAM operations than with only see-and-avoid capabilities, while still maintaining acceptable levels of safety. UAM concepts under development by the FAA, NASA, and industry focus on operations moving people and cargo in urban and suburban areas using innovative technologies, operations, and aircraft, including electric vertical takeoff and landing (eVTOL) aircraft. Researchers at NASA Langley Research Center, in collaboration with FAA researchers at the William J. Hughes Technical Center in Atlantic City, NJ, have conducted a series of medium-fidelity, human-in-the-loop research simulations of potential future UAM operations and concepts in both Class C and Class B airspace environments. These simulations have included use of a Langley-developed ADAA research tool called DANTi, which enables configurable ADAA displays to be presented to pilots of simulated eVTOL aircraft participating in higher-density and higher-tempo UAM operations. Experience and observations made during testing of the NASA-developed DANTi ADAA capability in the UAM NFLITE simulation environment will be reported in this paper together with a discussion of airspace integration and regulatory topics.

Detect and Avoid↗
NASA NTRS1973

Physics in perspective, volume 2. Part B: The interfaces

Detailed information of physics subfields and interface areas are presented. Topics discussed include: astrophysics and relativity, earth and planetary physics, physics in chemistry, physics in biology, instrumentation, education, and dissemination and use of the information of physics. For Vol. 1, see N72-28706; for excerpt from Vol. 1, see N72-29689; for Vol. 2, Pt. A, see N73-15706.

Source record↗
NASA NTRS1974

SAO/NASA joint investigation of astronomical viewing quality at Mount Hopkins Observatory: 1969-1971

Quantitative measurements of the astronomical seeing conditions have been made with a stellar-image monitor system at the Mt. Hopkins Observatory in Arizona. The results of this joint SAO-NASA experiment indicate that for a 15-cm-diameter telescope, image motion is typically 1 arcsec or less and that intensity fluctuations due to scintillation have a coefficient of irradiance variance of less than 0.12 on the average. Correlations between seeing quality and local meteorological conditions were investigated. Local temperature fluctuations and temperature gradients were found to be indicators of image-motion conditions, while high-altitude-wind conditions were shown to be somewhat correlated with scintillation-spectrum bandwidth. The theoretical basis for the relationship of atmospheric turbulence to optical effects is discussed in some detail, along with a description of the equipment used in the experiment. General site-testing comments and applications of the seeing-test results are also included.

Pearlman, M. R.↗
NASA NTRS1977

Uranus' rotational period

A modified spectroscopic technique was applied to determine the rotational period of Uranus and the orientation of the projected spin axis of the planet. The method consists in obtaining a series of spectra for both a nonrotated planet disk and for a disk rotated 180 degrees. Ignoring the effects of seeing in analyzing the spectra for no rotation of the disk leads to a lower limit on the period, and for a disk rotated 180 degrees, ignoring the seeing in the modeling of the spectra leads to an upper limit on the period. When blurring from seeing and guiding errors are added to the modeling for both image orientations and the model spectra are compared to the observations, both the period and the degree of blurring are obtained simultaneously. The results gave a period of rotation of Uranus 23 + 5 or - 2 hr.

Trafton, L.↗
NASA NTRS1984

The problem of atmospheric turbulence

All ground-based observations of the solar five-minute oscillations are affected by turbulence in the Earth's atmosphere that leads to substantial refractive index variations. The turbulent motions serve to mix an air mass that is thermally stratified in the vertical, thereby producing intermittent thermal fluctuations over a wide range of heights in the atmosphere. These thermal structures yield refractive index changes that deflect the light path in a complicated way, producing intricate variations of amplitude and phase in what might have started out as simple plane waves. Since the fluid turbulence is statistical in nature, so too is the optical turbulence which is an integral measure of the refractive index changes along the light travel path. All of this produces what is usually called atmospheric seeing, which consists of image motion, blurring and distortion across the field of view. The effects of atmospheric seeing upon observations of five-minute oscillations carried out from the ground were assessed. This will help to provide a baseline estimate of the scienctific benefits that might accrue if one were able to observe the same oscillations from a space observatory unfettered by seeing effects.

Toomre, J.↗
NASA NTRS1985

High-resolution surface photometry of elliptical galaxies

High-resolution CCD surface photometry profiles have been obtained for a sample of 42 nearby elliptical and SO galaxies as a first step in a program to investigate their central structure and core properties. A comparison of the present profiles to those of other observers shows that the accuracy of the central surface brightnesses is to better than 0.02 mag rms. Central resolution is limited by the atmospheric seeing PSF which is measured for each profile. A hybrid Fourier deconvolution procedure has been developed to correct the surface photometry for seeing in a model-independent way. Tests of the procedure on simulated galaxy images show that intrinsic core radii equal to the seeing FWHM or larger can be recovered from the observations. Application of the deconvolution procedure to the observed galaxies yields surface photometry profiles of slightly sub-arc second resolution.

Lauer, T. R.↗
NASA NTRS1987

Embedded expert system for space shuttle main engine maintenance

The SPARTA Embedded Expert System (SEES) is an intelligent health monitoring system that directs analysis by placing confidence factors on possible engine status and then recommends a course of action to an engineer or engine controller. The technique can prevent catastropic failures or costly rocket engine down time because of false alarms. Further, the SEES has potential as an on-board flight monitor for reusable rocket engine systems. The SEES methodology synergistically integrates vibration analysis, pattern recognition and communications theory techniques with an artificial intelligence technique - the Embedded Expert System (EES).

Pooley, J.↗
NASA NTRS1987

CCD photometry of globular cluster core structure. I - NGC 6388, NGC 6624, and M15: One flat core and two cusps

The first results of a major survey of globular cluster core structure are reported. Surface brightness profiles for three clusters are presented: one with a normal flat core profile (NGC 6388), and two with central cusps (NGC 6624 and M15). The profiles are fitted with both seeing-convolved King models and seeing-convolved power laws. A King model provides a reasonable fit to the entire profile of NGC 6388, but there are no acceptable King profiles for NGC 6624 and M15. For these two clusters, a seeing-convolved power law provides a good fit to the inner part of the profile, while a King model gives a good fit to the outer part of the profile. The interpretation of the measured power-law slopes of the central surface brightness cusps of NGC 6624 and M15 are discussed in terms of models for core collapse in a multicomponent cluster.

Lugger, Phyllis M.↗
NASA NTRS1988

Resonance scattering by sodium in Mercury's atmosphere. I - The effect of phase and atmospheric smearing

The dependence of the intensity in the sodium D1 and D2 lines on the planetary phase and position of the disk is presented. Theoretical intensities are convolved with an atmospheric point spread function with FWHM of 0.5 and 2.0 arcsec for planetary phases 60 and 90 deg. It is shown that although the absolute intensities are extremely dependent on seeing, the I(D2)/I(D1) ratio remains a reliable indicator of column abundance regardless of the seeing function. For a uniform distribution of sodium, limb brightening will be apparent for a seeing disk with FWHM of 0.5 arcsec but will not be apparent for a FWHM of 2.0 arcsec.

Killen, R. M.↗