Studies of hydrodynamic events in stellar evolution. II - Dynamic instabilities in stellar envelopes.
Explore the source record for details and available documents.
Sparks, W. M.↗
SEARCH · Search NASA
Results for “dynamic events”
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.
Dynamics of solar cosmic ray events - Processes at large heliocentric distances /much greater than 1 AU/
Observations of solar cosmic ray events at heliocentric distances up to 6 AU and beyond obtained by the Pioneer 10 and 11 spacecraft are discussed in terms of the propagation of energetic charged particles in interplanetary space. Following a review of the diffusion propagation model used to explain cosmic ray transport, the statistical studies of McCarthy and O'Gallagher (1976) and Zwickl and Webber (1977) of the relations of event parameters with radial distance and the simultaneous observation studies of Hamilton (1977) are reviewed, and it is noted that the results imply a slowly increasing radial diffusion coefficient out to about 6 AU. More recent analyses of data obtained at heliocentric distances greater than 10 AU are then presented which indicate that the coefficient of radial diffusion may actually be decreasing with radial distance beyond 5 AU. Finally, theoretical predictions of the radial variation of the diffusion coefficient are presented which take into account the background interplanetary medium and are shown to be in agreement with observations.
Hamilton, D. C.↗
Ozone during sudden stratospheric warming: A three-dimensional simulation
Sudden warmings which are currently observed in the winter stratosphere are believed to be due to the upward propagation of planetary waves originating in the troposphere. Major warmings are characterized by local increases of the temperature in a deep layer beyond the stratopause, with values of the order of 50 K at 10 mbar appearing over a short period of time and leading to significant changes in the rate constant of several chemical reactions. During such events, the dynamical fields in the stratosphere are completely altered, so that dramatic changes in the transport of trace constituents are expected. Preliminary results of a 3-D model simulation of the ozone behavior during winter in connection with the appearance of stratospheric warmings are reported. The middle stratosphere (12 mbar or approximately 32 km) where the chemical lifetime of odd oxygen is quite long, and consequently, transport plays a major role is emphasized.
Rose, K.↗
An observational study of the final warming in the Southern Hemisphere stratosphere
The final warming in the Southern Hemisphere stratosphere during the period September 1-November 30 for the years 1978-1983 is studied. The change in zonally averaged temperatures during that period is almost the same for each year. However, there is substantial interannual variability in the time evolution of the warming as events of enhanced wave, mean-flow interaction associated with bursts of upward propagating planetary waves develop at different times in different years. Polar temperatures in the middle stratosphere can increase as much as about 20 K in 4 days during these events. Such dynamical processes can play a significant role in the interannual variability of stratospheric ozone and other constituents.
Farrara, John D.↗
Study of the Alsys implementation of the Catalogue of Interface Features and Options for the Ada language for 80386 Unix
A set of programs was written to test the functionality and performance of the Alsys Ada implementation of the Catalogue of Interface Features and Options (CIFO), a set of optional Ada packages for real-time applications. No problems were found with the task id, preemption control, or shared-data packages. Minor problems were found with the dispatching control, dynamic priority, events, non-waiting entry call, semaphore, and scheduling packages. The Alsys implementation is derived mostly from Release 2 of the CIFO standard, but includes some of the features of Release 3 and some modifications unique to Alsys. Performance measurements show that the semaphore and shared-data features are an order-of-magnitude faster than the same mechanisms using an Ada rendezvous. The non-waiting entry call is slightly faster than a standard rendezvous. The existence of errors in the implementation, the incompleteness of the documentation from the published standard impair the usefulness of this implementation. Despite those short-comings, the Alsys CIFO implementation might be of value in the development of real-time applications.
Gibson, James S.↗
STS-74/Mir photogrammetric appendage structural dynamics experiment
The Photogrammetric Appendage Structural Dynamics Experiment (PASDE) is an International Space Station (ISS) Phase-1 risk mitigation experiment. Phase-1 experiments are performed during docking missions of the U.S. Space Shuttle to the Russian Space Station Mir. The purpose of the experiment is to demonstrate the use of photogrammetric techniques for determination of structural dynamic mode parameters of solar arrays and other spacecraft appendages. Photogrammetric techniques are a low cost alternative to appendage mounted accelerometers for the ISS program. The objective of the first flight of PASDE, on STS-74 in November 1995, was to obtain video images of Mir Kvant-2 solar array response to various structural dynamic excitation events. More than 113 minutes of high quality structural response video data was collected during the mission. The PASDE experiment hardware consisted of three instruments each containing two video cameras, two video tape recorders, a modified video signal time inserter, and associated avionics boxes. The instruments were designed, fabricated, and tested at the NASA Langley Research Center in eight months. The flight hardware was integrated into standard Hitchhiker canisters at the NASA Goddard Space Flight Center and then installed into the Space Shuttle cargo bay in locations selected to achieve good video coverage and photogrammetric geometry.
Welch, Sharon S.↗
A Classification of Mediterranean Cyclones Based on Global Analyses
The Mediterranean Sea region is dominated by baroclinic and orographic cyclogenesis. However, previous work has demonstrated the existence of rare but intense subsynoptic-scale cyclones displaying remarkable similarities to tropical cyclones and polar lows, including, but not limited to, an eye-like feature in the satellite imagery. The terms polar low and tropical cyclone have been often used interchangeably when referring to small-scale, convective Mediterranean vortices and no definitive statement has been made so far on their nature, be it sub-tropical or polar. Moreover, most of the classifications of Mediterranean cyclones have neglected the small-scale convective vortices, focusing only on the larger-scale and far more common baroclinic cyclones. A classification of all Mediterranean cyclones based on operational global analyses is proposed The classification is based on normalized horizontal shear, vertical shear, scale, low versus mid-level vorticity, low-level temperature gradients, and sea surface temperatures. In the classification system there is a continuum of possible events, according to the increasing role of barotropic instability and decreasing role of baroclinic instability. One of the main results is that the Mediterranean tropical cyclone-like vortices and the Mediterranean polar lows appear to be different types of events, in spite of the apparent similarity of their satellite imagery. A consistent terminology is adopted, stating that tropical cyclone- like vortices are the less baroclinic of all, followed by polar lows, cold small-scale cyclones and finally baroclinic lee cyclones. This classification is based on all the cyclones which occurred in a four-year period (between 1996 and 1999). Four cyclones, selected among all the ones which developed during this time-frame, are analyzed. Particularly, the classification allows to discriminate between two cyclones (occurred in October 1996 and in March 1999) which both display a very well-defined eye-like feature in the satellite imagery. According to our classification system, the two events are dynamically different and can be categorized as being respectively a tropical cyclone-like vortex and well-developed polar low.
Reale, Oreste↗
Planetary System Physics
Contents include a summary of publications followed by their abstracts titeled: 1. On microlensing rates and optical depth toward the Galactic center. 2. Newly discovered brown dwarfs not seen in microlensing timescale frequency distribution? 3. Origin and evolution of the natural satellites. 4. Probing the structure of the galaxy with microlensing. 5. Tides, Encyclopedia of Astronomy and Astrophysics. 6. The Puzzle of the Titan-Hyperion 4:3 Orbital Resonance. 7. On the Validity of the Coagulation Equation and the Nature of Runaway Growth. 8. Making Hyperion. 9. The MESSENGER mission to Mercury: Scientific objectives and implementation. 10. A Survey of Numerical Solutions to the Coagulation. 11. Probability of detecting a planetary companion during a microlensing event. 12. Dynamics and origin of the 2:l orbital resonances of the GJ876 planets. 13. Planetary Interior Structure Revealed by Spin Dynamics. 14. A primordial origin of the Laplace relation among the Galilean Satellites. 15. A procedure for determining the nature of Mercury's core. 16. Secular evolution of hierarchical planetary systems. 17. Tidally induced volcanism. 18. Extrasolar planets and mean motion resonances. 19. Comparison of a ground-based microlensing search for planets with a search from space.
Peale, S. J.↗
Simulation studies of vestibular macular afferent-discharge patterns using a new, quasi-3-D finite volume method
A quasi-three-dimensional finite-volume numerical simulator was developed to study passive voltage spread in vestibular macular afferents. The method, borrowed from computational fluid dynamics, discretizes events transpiring in small volumes over time. The afferent simulated had three calyces with processes. The number of processes and synapses, and direction and timing of synapse activation, were varied. Simultaneous synapse activation resulted in shortest latency, while directional activation (proximal to distal and distal to proximal) yielded most regular discharges. Color-coded visualizations showed that the simulator discretized events and demonstrated that discharge produced a distal spread of voltage from the spike initiator into the ending. The simulations indicate that directional input, morphology, and timing of synapse activation can affect discharge properties, as must also distal spread of voltage from the spike initiator. The finite volume method has generality and can be applied to more complex neurons to explore discrete synaptic effects in four dimensions.
NASA Center ARC↗
Petri Nets as Modeling Tool for Emergent Agents
Emergent agents, those agents whose local interactions can cause unexpected global results, require a method of modeling that is both dynamic and structured Petri Nets, a modeling tool developed for dynamic discrete event system of mainly functional agents, provide this, and have the benefit of being an established tool. We present here the details of the modeling method here and discuss how to implement its use for modeling agent-based systems. Petri Nets have been used extensively in the modeling of functional agents, those agents who have defined purposes and whose actions should result in a know outcome. However, emergent agents, those agents who have a defined structure but whose interaction causes outcomes that are unpredictable, have not yet found a modeling style that suits them. A problem with formally modeling emergent agents that any formal modeling style usually expects to show the results of a problem and the results of problems studied using emergent agents are not apparent from the initial construction. However, the study of emergent agents still requires a method to analyze the agents themselves, and have sensible conversation about the differences and similarities between types of emergent agents. We attempt to correct this problem by applying Petri Nets to the characterization of emergent agents. In doing so, the emergent properties of these agents can be highlighted, and conversation about the nature and compatibility of the differing methods of agent creation can begin.
Bergman, Marto↗
Active Raman sounding of the earth's water vapor field
The typically weak cross-sections characteristic of Raman processes has historically limited their use in atmospheric remote sensing to nighttime application. However, with advances in instrumentation and techniques, it is now possible to apply Raman lidar to the monitoring of atmospheric water vapor, aerosols and clouds throughout the diurnal cycle. Upper tropospheric and lower stratospheric measurements of water vapor using Raman lidar are also possible but are limited to nighttime and require long integration times. However, boundary layer studies of water vapor variability can now be performed with high temporal and spatial resolution. This paper will review the current state-of-the-art of Raman lidar for high-resolution measurements of the atmospheric water vapor, aerosol and cloud fields. In particular, we describe the use of Raman lidar for mapping the vertical distribution and variability of atmospheric water vapor, aerosols and clouds throughout the evolution of dynamic meteorological events. The ability of Raman lidar to detect and characterize water in the region of the tropopause and the importance of high-altitude water vapor for climate-related studies and meteorological satellite performance are discussed.
Earth (Planet)↗
Real Time On-line Space Research Laboratory Environment Monitoring with Off-line Trend and Prediction Analysis
One of the responsibilities of the NASA Glenn Principal Investigator Microgravity Services is to support NASA sponsored investigators in the area of reduced-gravity acceleration data analysis, interpretation and the monitoring of the reduced-gravity environment on-board various carriers. With the International Space Station currently operational, a significant amount of acceleration data is being down-linked and processed on ground for both the space station onboard environment characterization (and verification) and scientific experiments. Therefore, to help principal investigator teams monitor the acceleration level on-board the International Space Station to avoid undesirable impact on their experiment, when possible, the NASA Glenn Principal Investigator Microgravity Services developed an artificial intelligence monitoring system, which detects in near real time any change in the environment susceptible to affect onboard experiments. The main objective of the monitoring system is to help research teams identify the vibratory disturbances that are active at any instant of time onboard the International Space Station that might impact the environment in which their experiment is being conducted. The monitoring system allows any space research scientist, at any location and at any time, to see the current acceleration level on-board the Space Station via the World Wide Web. From the NASA Glenn s Exploration Systems Division web site, research scientists can see in near real time the active disturbances, such as pumps, fans, compressor, crew exercise, re-boost, extra-vehicular activity, etc., and decide whether or not to continue operating or stopping (or making note of such activity for later correlation with science results) their experiments based on the g-level associated with that specific event. A dynamic graphical display accessible via the World Wide Web shows the status of all the vibratory disturbance activities with their degree of confidence as well as their g-level contribution to the environment. The system can detect both known and unknown vibratory disturbance activities. It can also perform trend analysis and prediction by analyzing past data over many Increments of the space station for selected disturbance activities. This feature can be used to monitor the health of onboard mechanical systems to detect and prevent potential system failure as well as for use by research scientists during their science results analysis. Examples of both real time on-line vibratory disturbance detection and off-line trend analysis are presented in this paper. Several soft computing techniques such as Kohonen s Self-Organizing Feature Map, Learning Vector Quantization, Back-Propagation Neural Networks, and Fuzzy Logic were used to design the system.
Jules, Kenol↗
Suited Occupant Injury Potential During Dynamic Spacecraft Flight Phases
In support of the Constellation Space Suit Element [CSSE], a new space-suit architecture will be created for support of Launch, Entry, Abort, Microgravity Extra- Vehicular Activity [EVA], and post-landing crew operations, safety and, under emergency conditions, survival. The space suit is unique in comparison to previous launch, entry, and abort [LEA] suit architectures in that it utilizes rigid mobility elements in the scye (i.e., shoulder) and the upper arm regions. The suit architecture also utilizes rigid thigh disconnect elements to create a quick disconnect approximately located above the knee. This feature allows commonality of the lower portion of the suit (from the thigh disconnect down), making the lower legs common across two suit configurations. This suit must interface with the Orion vehicle seat subsystem, which includes seat components, lateral supports, and restraints. Due to the unique configuration of spacesuit mobility elements, combined with the need to provide occupant protection during dynamic vehicle events, risks have been identified with potential injury due to the suit characteristics described above. To address the risk concerns, a test series has been developed in coordination with the Injury Biomechanics Research Laboratory [IBRL] to evaluate the likelihood and consequences of these potential issues. Testing includes use of Anthropomorphic Test Devices [ATDs; vernacularly referred to as "crash test dummies"], Post Mortem Human Subjects [PMHS], and representative seat/suit hardware in combination with high linear acceleration events. The ensuing treatment focuses on test purpose and objectives; test hardware, facility, and setup; and preliminary results.
Dub, Mark O.↗
Injury Potential Testing of Suited Occupants During Dynamic Spacecraft Flight Phases
In support of the Constellation Program, a space-suit architecture was envisioned for support of Launch, Entry, Abort, Micro-g EVA, Post Landing crew operations, and under emergency conditions, survival. This space suit architecture is unique in comparison to previous launch, entry, and abort (LEA) suit architectures in that it utilized rigid mobility elements in the scye and the upper arm regions. The suit architecture also employed rigid thigh disconnect elements to allow for quick disconnect functionality above the knee which allowed for commonality of the lower portion of the suit across two suit configurations. This suit architecture was designed to interface with the Orion seat subsystem, which includes seat components, lateral supports, and restraints. Due to this unique configuration of spacesuit mobility elements, combined with the need to provide occupant protection during dynamic landing events, risks were identified with potential injury due to the suit characteristics described above. To address the risk concerns, a test series was developed to evaluate the likelihood and consequences of these potential issues. Testing included use of Anthropomorphic Test Devices (ATDs), Post Mortem Human Subjects (PMHS), and representative seat/suit hardware in combination with high linear acceleration events. The ensuing treatment focuses o detailed results of the testing that has ben conducted under this test series thus far.
McFarland, Shane M.↗
Injury Potential Testing of Suited Occupants During Dynamic Spacecraft Flight Phases
In support of the NASA Constellation Program, a space-suit architecture was envisioned for support of Launch, Entry, Abort, Micro-g EVA, Post Landing crew operations, and under emergency conditions, survival. This space suit architecture is unique in comparison to previous launch, entry, and abort (LEA) suit architectures in that it utilized rigid mobility elements in the scye and the upper arm regions. The suit architecture also employed rigid thigh disconnect elements to allow for quick disconnect functionality above the knee which allowed for commonality of the lower portion of the suit across two suit configurations. This suit architecture was designed to interface with the Orion seat subsystem, which includes seat components, lateral supports, and restraints. Due to this unique configuration of spacesuit mobility elements, combined with the need to provide occupant protection during dynamic landing events, risks were identified with potential injury due to the suit characteristics described above. To address the risk concerns, a test series was developed to evaluate the likelihood and consequences of these potential issues. Testing included use of Anthropomorphic Test Devices (ATDs), Post Mortem Human Subjects (PMHS), and representative seat/suit hardware in combination with high linear acceleration events. The ensuing treatment focuses on detailed results of the testing that has been conducted under this test series thus far.
McFarland, Shane M.↗
Near-Earth Phase Risk Comparison of Human Mars Campaign Architectures
A risk analysis of the launch, orbital assembly, and Earth-departure phases of human Mars exploration campaign architectures was completed as an extension of a probabilistic risk assessment (PRA) originally carried out under the NASA Constellation Program Ares V Project. The objective of the updated analysis was to study the sensitivity of loss-of-campaign risk to such architectural factors as composition of the propellant delivery portion of the launch vehicle fleet (Ares V heavy-lift launch vehicle vs. smaller/cheaper commercial launchers) and the degree of launcher or Mars-bound spacecraft element sparing. Both a static PRA analysis and a dynamic, event-based Monte Carlo simulation were developed and used to evaluate the probability of loss of campaign under different sparing options. Results showed that with no sparing, loss-of-campaign risk is strongly driven by launcher count and on-orbit loiter duration, favoring an all-Ares V launch approach. Further, the reliability of the all-Ares V architecture showed significant improvement with the addition of a single spare launcher/payload. Among architectures utilizing a mix of Ares V and commercial launchers, those that minimized the on-orbit loiter duration of Mars-bound elements were found to exceed the reliability of no spare all-Ares V campaign if unlimited commercial vehicle sparing was assumed
Manning, Ted A.↗
Multi-Gas Monitor (MGM)
Multi-Gas Monitor is a flight experiment, a technology demonstration to test the ability of tunable diode laser spectroscopy based instrument to stay in calibration long term and follow events and dynamics occurring with the cabin atmosphere. MGM measures 4 gases: oxygen, carbon monoxide, ammonia and water vapor, as well as temperature and pressure. This month marked one year of successful and continuous MGM operation on ISS. The crew successfully tested the ammonia channel using a commercially available inhalant. MGM has detected some interesting dynamics inside Japanese Experiment Module (JEM) as a result of CO2 thruster firings from the SPHERES/RINGS payload and water spikes from dry out cycling of the JEM heat exchangers. Results to date have given us high confidence in the technology such that we believe this could have applications in the energy and medical sectors. This presentation will summarize the testing and results of the unit on ISS and suggest areas of use within the energy and medical arenas.
Pilgrim, Jeff↗
Genesis of Interplanetary Intermittent Turbulence: a Case Study of Rope-Rope Magnetic Reconnection
In a recent paper, the relation between current sheet, magnetic reconnection, and turbulence at the leading edge of an interplanetary coronal mass ejection was studied. We report here the observation of magnetic reconnection at the interface region of two interplanetary magnetic flux ropes. The front and rear boundary layers of three interplanetary magnetic flux ropes are identified, and the structures of magnetic flux ropes are reconstructed by the Grad Shafranov method. A quantitative analysis of the reconnection condition and the degree of intermittency reveals that rope-rope magnetic reconnection is the most likely site for genesis of interplanetary intermittency turbulence in this event. The dynamic pressure pulse resulting from this reconnection triggers the onset of a geomagnetic storm.
Chian, Abraham C.- L.↗