Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Particle phenomena”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

A preliminary summary of the observations of the 16 February 1984 solar flare (STIP Interval XV, 12-21 February 1984)

The solar flare on 16 Feb. 1984 (0900 UT) and the associated photon and particle emissions were perhaps the most interesting solar and interplanetary phenomena during STIP Interval XV, 12 to 21 Feb. 1984. The X-ray and microwave radio emissions, as observed from the Earth, were relatively weak and no optical flare was reported. However, the hard X-ray and low energy gamma-ray observations made with the Pioneer Venus Orbiter spacecraft behind the west limb of the Sun indicate that the flare was, in reality, very intense. There is evidence that the flare was located approx 40 deg behind the west limb of the Sun and hence, for instruments located near the Earth, the most intense parts of the X-ray and microwave radio sources were occulted by the photosphere. However, the effect of occultation on the metric type II, type III, and type IV and decimetric (type DCIM) radio sources appeared to be relatively small. Following the flare, a large increase in the counting rates was recorded by several ground level neutron monitors and energetic particle detectors located in interplanetary space. A preliminary analysis of the 16 Feb. 1984 flare observations follows.

Kane, S. R.↗
NASA NTRS2010

Computer Models Simulate Fine Particle Dispersion

Through a NASA Seed Fund partnership with DEM Solutions Inc., of Lebanon, New Hampshire, scientists at Kennedy Space Center refined existing software to study the electrostatic phenomena of granular and bulk materials as they apply to planetary surfaces. The software, EDEM, allows users to import particles and obtain accurate representations of their shapes for modeling purposes, such as simulating bulk solids behavior, and was enhanced to be able to more accurately model fine, abrasive, cohesive particles. These new EDEM capabilities can be applied in many industries unrelated to space exploration and have been adopted by several prominent U.S. companies, including John Deere, Pfizer, and Procter & Gamble.

Source record↗
NASA NTRS1990

Rocket studies of the lower ionosphere

The earth's ionosphere in the altitude range of 50 to 200 km was investigated by rocket-borne sensors, supplemented by ground-based measurement. The rocket payloads included mass spectrometers, energetic particle detectors, Langmuir probes and radio propagation experiments. Where possible, rocket flights were included in studies of specific phenomena, and the availability of data from other experiments greatly increased the significance of the results. The principal ionospheric phenomena studied were: winter anomaly in radiowave absorption, ozone and molecular oxygen densities, mid-latitude sporadic-E layers, energetic particle precipitation at middle and low latitudes, ionospheric instabilities and turbulence, and solar eclipse effects in the D and E regions. This document lists personnel who worked on the project, and provides a bibliography of resultant publications.

Bowhill, Sidney A.↗
NASA NTRS1971

Phenomena after meteoroid penetration of a bumper plate

The analysis of hypervelocity impact of particles on a detector in space, with flow and shock penetration through fluid, plastic, and elastic zones was studied. The original paper and computer program on this topic is presented. Improvements in the program for the study of the formation of a cone of debris are discussed. The truncated apex of the cone is at the hole formed by the penetration of an initially spherical rock through a thin plate. A solution for the penetration of the thin plate was sought.

Todd, F. C.↗
NASA NTRS1991

Gamma Ray Observatory (GRO) Prelaunch Mission Operations Report (MOR)

The NASA Astrophysics Program is an endeavor to understand the origin and fate of the universe, to understand the birth and evolution of the large variety of objects in the universe, from the most benign to the most violent, and to probe the fundamental laws of physics by examining their behavior under extreme physical conditions. These goals are pursued by means of observations across the entire electromagnetic spectrum, and through theoretical interpretation of radiations and fields associated with astrophysical systems. Astrophysics orbital flight programs are structured under one of two operational objectives: (1) the establishment of long duration Great Observatories for viewing the universe in four major wavelength regions of the electromagnetic spectrum (radio/infrared/submillimeter, visible/ultraviolet, X-ray, and gamma ray), and (2) obtaining crucial bridging and supporting measurements via missions with directed objectives of intermediate or small scope conducted within the Explorer and Spacelab programs. Under (1) in this context, the Gamma Ray Observatory (GRO) is one of NASA's four Great Observatories. The other three are the Hubble Space Telescope (HST) for the visible and ultraviolet portion of the spectrum, the Advanced X-ray Astrophysics Facility (AXAF) for the X-ray band, and the Space Infrared Telescope Facility (SIRTF) for infrared wavelengths. GRO's specific mission is to study the sources and astrophysical processes that produce the highest energy electromagnetic radiation from the cosmos. The fundamental physical processes that are known to produce gamma radiation in the universe include nuclear reactions, electron bremsstrahlung, matter-antimatter annihilation, elementary particle production and decay, Compton scattering, synchrotron radiation. GRO will address a variety of questions relevant to understanding the universe, such as: the formation of the elements; the structure and dynamics of the Galaxy; the nature of pulsars; the existence of black holes; the possible existence of large amounts of antimatter, energetic and explosive phenomena occurring in galactic nuclei; the origin of the cosmic diffuse background; particle acceleration in the Sun, stars and stellar systems; processes in supernovae; and the origin and evolution of the universe itself.

Source record↗
NASA NTRS1984

Qualification of the T2 wind tunnel in cryogenic operation. B: Flow fluctuations, particle detection and qualification

This report presents part of the tests for verification of the T2 transonic induction wind tunnel in cryogenic operation. The first part of the results presented concerns fluctuations in pressure and temperature at ambient temperature and in cryogenic regulation. The second part presents the condensation phenomena which could be observed in the cryogenic flow by means of an optical particle detection system in the test section.

Dor, J. B.↗
NASA NTRS1992

Effects of space environment on structural materials

A preliminary study of materials exposed in space in a low Earth orbit for nearly six years has revealed a wide range of micrometeorite or microparticle impact craters ranging in size from 1 to 1000 micron in diameter, debris particles from adjacent and distant materials systems, reaction products, and other growth features on the specimen surfaces, and related phenomena. The exposed surface features included fine grained and nearly amorphous materials as well as a large array of single crystal particles. A replication type, lift off technique was developed to remove reaction products and debris from the specimen surfaces in order to isolate them from the background substrate without creating microchemical or microstructural artifacts or alterations. This resulted in surface features resting on a carbon support film which was virtually invisible to observation by electron microscopy and nondispersive x ray analysis. Some evidence for blisters on leading edge aluminum alloy surfaces and a high surface region concentration of oxygen determined by Auger electron spectrometry suggests oxygen effects where fluences exceed 10(exp 21) atoms/sq cm.

Miglionico, C.↗
NASA NTRS1989

The International Heliospheric Study; Proceedings of Symposium 10 of the 27th COSPAR Plenary Meeting, Espoo, Finland, July 18-29, 1988

The conference presents papers on solar phenomena, coronal mass ejections, solar wind, heliospheric magnetic field, energetic particles, cosmic rays, and interaction with the interstellar medium. Topics include the NASA heliospheric program, Alfven wave heating of the solar atmosphere in the transition region, IPS imaging of heliospheric transients, CME associated forward-reverse shock pairs, and solar wind latitude/longitude variations from interplanetary scintillations. Consideration is also given to cosmic ray gradients in the heliosphere, reconnection at the heliopause, and the interaction of the solar wind with the local interstellar medium.

Shea, M. A.↗
NASA NTRS1989

Surface discharges on natural dielectrics in the solar system

In a variety of environments, notably those defined by the magnetospheres of the giant planets, natural dielectrics are exposed to large fluxes of charged particles. Laboratory simulations of these potentially discharge-inducing charging phenomena have been conducted to ascertain whether discharges can occur on natural dielectrics. Charging beam intensities ranged from 10 to the 10th to 10 to the 12th particles/sq cm per sec, with exposure times of 1-10 min; the lowest intensity is comparable to that expected on the surface of Io. Discharges were recorded during all exposures.

Campins, Humberto↗
NASA NTRS1991

Impact cratering calculations

In the course of carrying out finite difference calculations, it was discovered that for large craters, a previously unrecognized type of crater (diameter) growth occurred which was called lip wave propagation. This type of growth is illustrated for an impact of a 1000 km (2a) silicate bolide at 12 km/sec (U) onto a silicate half-space at earth gravity (1 g). The von Misses crustal strength is 2.4 kbar. The motion at the crater lip associated with this wave type phenomena is up, outward, and then down, similar to the particle motion of a surface wave. It is shown that the crater diameter has grown d/a of approximately 25 to d/a of approximately 4 via lip propagation from Ut/a = 5.56 to 17.0 during the time when rebound occurs. A new code is being used to study partitioning of energy and momentum and cratering efficiency with self gravity for finite-sized objects rather than the previously discussed planetary half-space problems. These are important and fundamental subjects which can be addressed with smoothed particle hydrodynamic (SPH) codes. The SPH method was used to model various problems in astrophysics and planetary physics. The initial work demonstrates that the energy budget for normal and oblique impacts are distinctly different than earlier calculations for silicate projectile impact on a silicate half space. Motivated by the first striking radar images of Venus obtained by Magellan, the effect of the atmosphere on impact cratering was studied. In order the further quantify the processes of meteor break-up and trajectory scattering upon break-up, the reentry physics of meteors striking Venus' atmosphere versus that of the Earth were studied.

Ahrens, Thomas J.↗
NASA NTRS2000

Computational Analysis for Rocket-Based Combined-Cycle Systems During Rocket-Only Operation

A series of Reynolds-averaged Navier-Stokes calculations were employed to study the performance of rocket-based combined-cycle systems operating in an all-rocket mode. This parametric series of calculations were executed within a statistical framework, commonly known as design of experiments. The parametric design space included four geometric and two flowfield variables set at three levels each, for a total of 729 possible combinations. A D-optimal design strategy was selected. It required that only 36 separate computational fluid dynamics (CFD) solutions be performed to develop a full response surface model, which quantified the linear, bilinear, and curvilinear effects of the six experimental variables. The axisymmetric, Reynolds-averaged Navier-Stokes simulations were executed with the NPARC v3.0 code. The response used in the statistical analysis was created from Isp efficiency data integrated from the 36 CFD simulations. The influence of turbulence modeling was analyzed by using both one- and two-equation models. Careful attention was also given to quantify the influence of mesh dependence, iterative convergence, and artificial viscosity upon the resulting statistical model. Thirteen statistically significant effects were observed to have an influence on rocket-based combined-cycle nozzle performance. It was apparent that the free-expansion process, directly downstream of the rocket nozzle, can influence the Isp efficiency. Numerical schlieren images and particle traces have been used to further understand the physical phenomena behind several of the statistically significant results.

Steffen, C. J., Jr.↗
NASA NTRS2000

Exploring the Extreme Universe with GLAST

The Gamma-ray Large Area Space Telescope, GLAST, is a satellite-based experiment under development to measure the cosmic gamma-ray flux in the energy range 20 MeV to > 300 GeV. With a sensitivity that is more than a factor 30 greater than that of the EGRET detector on GRO, GLAST will open a new and important window on a wide variety of high energy phenomena, including supermassive black holes and active galactic nuclei, gamma-ray bursts, supernova remnants, and searches for new phenomena such as supersymmetric dark matter annihilations and big bang particle relics. The launch is planned for 2005. This talk will include a discussion of the physics, the scientific capabilities, the novel collaboration of particle physicists and high energy astrophysicists, and the mission status.

Ritz, Steven↗
NASA NTRS2003

Self-Consistent Large-Scale Magnetosphere-Ionosphere Coupling: Computational Aspects and Experiments

Both external and internal phenomena impact the terrestrial magnetosphere. For example, solar wind and particle precipitation effect the distribution of hot plasma in the magnetosphere. Numerous models exist to describe different aspects of magnetosphere characteristics. For example, Tsyganenko has developed a series of models (e.g., [TSYG89]) that describe the magnetic field, and Stern [STER75] and Volland [VOLL73] have developed an analytical model that describes the convection electric field. Over the past several years, NASA colleague Khazanov, working with Fok and others, has developed a large-scale coupled model that tracks particle flow to determine hot ion and electron phase space densities in the magnetosphere. This model utilizes external data such as solar wind densities and velocities and geomagnetic indices (e.g., Kp) to drive computational processes that evaluate magnetic, electric field, and plasma sheet models at any time point. These models are coupled such that energetic ion and electron fluxes are produced, with those fluxes capable of interacting with the electric field model. A diagrammatic representation of the coupled model is shown.

Newman, Timothy S.↗
NASA NTRS2005

Magnetic Variations Associated With Solar Flares

A report summarizes an investigation of helioseismic waves and magnetic variations associated with solar flares, involving analysis of data acquired by the Michelson Doppler Imager (MDI) aboard the Solar and Heliocentric Observatory (SOHO) spacecraft, the Yohkoh spacecraft, and the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) spacecraft. Reconstruction of x-ray flare images from RHESSI data and comparison of them with MDI magnetic maps were performed in an attempt to infer the changes in the geometry of the magnetic field. It was established that in most flares observed with MDI, downward propagating shocks were much weaker than was one observed in the July 9, 1996 flare, which caused a strong helioseismic response. It was concluded that most of the observed impulsive variations result from direct impact of high-energy particles. Computer codes were developed for further study of these phenomena.

Petrosian, Vahe↗
NASA NTRS2011

Sky Event Reporting Metadata (VOEvent) Version 2.0

VOEvent [20] defines the content and meaning of a standard information packet for representing, transmitting, publishing and archiving information about a transient celestial event, with the implication that timely follow-up is of interest. The objective is to motivate the observation of targets-of-opportunity, to drive robotic telescopes, to trigger archive searches, and to alert the community. VOEvent is focused on the reporting of photon events, but events mediated by disparate phenomena such as neutrinos, gravitational waves, and solar or atmospheric particle bursts may also be reported. Structured data is used, rather than natural language, so that automated systems can effectively interpret VOEvent packets. Each packet may contain zero or more of the "who, what, where, when & how" of a detected event, but in addition, may contain a hypothesis (a "why") regarding the nature of the underlying physical cause of the event.

Seaman, Rob↗
NASA NTRS2012

Properties of Ground Level Enhancement Events and the Associated Solar Eruptions During Solar Cycle 23

Solar cycle 23 witnessed the most complete set of observations of coronal mass ejections (CMEs) associated with the Ground Level Enhancement (GLE) events. We present an overview of the observed properties of the GLEs and those of the two associated phenomena, viz., flares and CMEs, both being potential sources of particle acceleration. Although we do not find a striking correlation between the GLE intensity and the parameters of flares and CMEs, the solar eruptions are very intense involving X-class flares and extreme CME speeds (average approx. 2000 km/s). An M7.1 flare and a 1200 km/s CME are the weakest events in the list of 16 GLE events. Most (80 %) of the CMEs are full halos with the three non-halos having widths in the range 167 to 212 degrees. The active regions in which the GLE events originate are generally large: 1290 msh (median 1010 msh) compared to 934 msh (median: 790 msh) for SEP-producing active regions. For accurate estimation of the CME height at the time of metric type II onset and GLE particle release, we estimated the initial acceleration of the CMEs using flare and CME observations. The initial acceleration of GLE-associated CMEs is much larger (by a factor of 2) than that of ordinary CMEs (2.3 km/sq s vs. 1 km/sq s). We confirmed the initial acceleration for two events for which CME measurements are available in the inner corona. The GLE particle release is delayed with respect to the onset of all electromagnetic signatures of the eruptions: type II bursts, low frequency type III bursts, soft X-ray flares and CMEs. The presence of metric type II radio bursts some 17 min (median: 16 min; range: 3 to 48 min) before the GLE onset indicates shock formation well before the particle release. The release of GLE particles occurs when the CMEs reach an average height of approx 3.09 R(sub s) (median: 3.18 R (sub s) ; range: 1.71 to 4.01 R (sub s) ) for well-connected events (source longitude in the range W20–W90). For poorly connected events, the average CME height at GLE particle release is ∼66 % larger (mean: 5.18 R (sub s) ; median: 4.61 R (sub s) ; range: 2.75–8.49 R (sub s) ). The longitudinal dependence is consistent with shock accelerations because the shocks from poorly connected events need to expand more to cross the field lines connecting to an Earth observer. On the other hand, the CME height at metric type II burst onset has no longitudinal dependence because electromagnetic signals do not require magnetic connectivity to the observer. For several events, the GLE particle release is very close to the time of first appearance of the CME in the coronagraphic field of view, so we independently confirmed the CME height at particle release. The CME height at metric type II burst onset is in the narrow range 1.29 to 1.8 R(sub s), with mean and median values of 1.53 and 1.47 R(sub s). The CME heights at metric type II burst onset and GLE particle release correspond to the minimum and maximum in the Alfven speed profile. The increase in CME speed between these two heights suggests an increase in Alfvenic Mach number from 2 to 3. The CME heights at GLE particle release are in good agreement with those obtained from the velocity dispersion analysis, including the source longitude dependence. We also discuss the implications of the delay of GLE particle release with respect to complex type III bursts by approx 18 min (median: 16 in; range: 2 to 44 min) for the flare acceleration mechanism. A similar analysis is also performed on the delay of particle release relative to the hard X-ray emission.

Geomagnetic Storms↗
NASA NTRS2021

High-speed wide-angle interleaved scanning technique for a 3D imaging lidar

In this paper, we describe a novel interleaved scanner for an eye-safe 3D scanning lidar system to measure aerodynamic phenomena in a wind tunnel using elastic backscatter from seeding particles. The scanner assembly consists of a rotating polygon scanner for line scanning along the fast axis, a galvanometer (galvo) scanner for scanning along the slow axis, angular position sensors and motor controllers. The polygon scanner sweeps the lidar beam at up to 10,000 lines/s across a 27 deg angular field-of-regard in the fast axis, while the galvo scanner covers an angular range of 20 deg in the slow axis. Using this scanner, the lidar can perform non-intrusive flow visualization, velocimetry, and hard target mapping at mmscale spatial resolution to a standoff range of 5 m at an update rate of 50 Hz for the full field-of-regard. An interleaved scanning methodology for the acquisition of two snapshots of 3D lidar intensity data with a 100 μs time offset is discussed. The design of the control and data acquisition electronics is described. The effects of rapid scanning on the response of a narrow field-of-view lidar are addressed. The design of the scanner is scalable and can be tailored to meet the requirements of other applications by increasing or decreasing the standoff range, angular field-of-regard and scan rate.

3D Imaging Lidar↗