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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Structure and Dynamics of the Solar Corona

Advanced computational techniques were used to study solar coronal heating and coronal mass ejections. A three dimensional, time dependent resistive magnetohydrodynamic code was used to study the dynamic response of a model corona to continuous, slow, random magnetic footpoint displacements in the photosphere. Three dimensional numerical simulations of the response of the corona to simple smooth braiding flows in the photosphere were calculated to illustrate and understand the spontaneous formation of current filaments. Two dimensional steady state helmet streamer configurations were obtained by determining the time asymptotic state of the interaction of an initially one dimensinal transponic solar wind with a spherical potential dipole field. The disruption of the steady state helmet streamer configuration was studied as a response to shearing of the magnetic footpoints of the closed field lines under the helmet.

Schnack, D. D.↗
NASA NTRS1994

Modeling coronal evolution

Helmet streamers on the sun were observed to be the site of coronal mass ejections, dynamic events that eject coronal plasma and magnetic fields into the solar wind. A two dimensional (azimuthally symmetric) helmet streamer configuration was developed by computing solutions of the time dependent magnetohydrodynamic (MHD) equations, for a specified magnetic flux distribution on the sun. The helmet streamer is not symmetric about the equator. The evolution of the configuration, when differential rotation is applied, was investigated. It was found that after many rotations the configuration does not reach a steady state, but disrupts recurrently with the ejection of a plasmoid. These results suggest that differential rotation may be one of the mechanisms by which mass ejections are initiated.

Linker, Jon A.↗
NASA NTRS1996

Dynamical Evolution of a Coronal Streamer-Flux Rope System: 2. A Self-Consistent Non-Planar Magnetohydrodynamic Simulation

The dynamical response of a helmet streamer to a flux rope escape from the sub-photosphere is examined in a physically self-consistent manner within the approximation of axisymmetric three-dimensional magnetohydrodynamics (i.e., so-called '2 1/2 D'). In contrast to the previous planar analyses of Paper 1 (Wu, Guo, and Wang), the present study shows, with the inclusion of out-of-plane components of magnetic and velocity fields, that the magnetic configuration represents a helical flux rope instead of a planar bubble as shown in Paper 1. Because of this more physically-realistic configuration, we are able to examine the dynamical evolution of the helical flux rope's interaction with the helmet streamer. This process leads to the formation of two parts of the solar mass ejection: (i) the expulsion of the helmet dome due to eruption of this flux rope, and (ii) the flux rope's eruption itself. When this two-part feature propagates out to the interplanetary space, it exhibits all the physical characteristics of observed interplanetary magnetic clouds. These numerical simulations also show that the dynamical behavior of the streamer-flux rope system has three distinct states: (i) quasi-equilibrium, (ii) non-equilibrium, and (iii) eruptive state depending on the energy level of the flux rope.

Wu, S. T.↗
NASA NTRS2001

Stagnation Flow in Streamer Boundaries

Flow tubes adjacent to closed magnetic field lines on the boundaries of streamers can have spreading factors which change rapidly with height. Numerical models in this thin layer are subject to uncertainties. Here we use an analytic model of magnetically closed and adjacent open regions to compute the spreading factor close to the closed field lines and the flow on the open field lines. We axe able to recover the shape of the closed field region, or helmet, and show the evolution of the helmet under slowly increasing temperature. We also show why and when stagnation flow can occur in the vicinity of the cusp at the top of the helmet.

Suess, Steven T.↗
NASA NTRS2002

Stagnation Flow in Streamer Boundaries

It is possible for flow tubes adjacent to closed magnetic field lines on the boundaries of streamers to have spreading factors that change rapidly according to height. Mathematical models in this thin layer are prone to uncertainties. In this paper we use an analytical model of magnetically closed and adjacent open regions to calculate the spreading factor close to the closed field lines and near the flow on the open field lines. We recovered the shape of the closed field region, or helmet, and show the evolution of the helmet under increasing temperature. We also show why and when stagnation flow can occur in the area of the cusp at the top of the helmet.

Suess, S. T.↗
NASA NTRS2002

Flow in Streamer Boundaries and Streamer Stability

Streamers can extend to many solar radii but the closed field regions, or helmets, probably never reach higher than 2-4 solar radii. The brightness boundary defining streamers therefore is a boundary between different flow regimes rather than between static plasma and expanding solar wind. It is reasonable to assume that this boundary divides fast coronal hole wind from slow wind. Flow inside this boundary can be studied using simple MHD models and is a type of stagnation flow. We will present examples of what this flow can be like. The flow effects the stability of the underlying helmet, which can be subject to leakage out the cusp similar to the small mass releases observed with the SOHO/LASCO coronagraph. It can also cause the helmet to be more or less susceptible to being carried away in a coronal mass ejection.

Suess, S. T.↗
NASA NTRS2004

Flow In Streamer Boundaries, and Streamer Stability

Streamers can extend to many solar radii but the closed field regions, or helmets, reach no higher than 2-4 solar radii. The brightness boundary defining streamers is therefore a boundary between different flow regimes rather than between static plasma and expanding solar wind. It is reasonable to assume that this boundary divides fast coronal hole wind from slow wind. Flow inside this boundary can be studied using MHD models and is a type of stagnation flow. We describe such a model that is essentially analytic and show examples of flow solutions within the context and assumptions of the model. The flow affects the stability of the underlying helmet, which can be subject to a leakage out of the cusp that is similar to the small mass releases observed with the SOHO/LASCO coronagraph. It can also cause the helmet to be susceptible to being carried away in a coronal mass ejection. The model therefore also offers a way to study streamer stability.

Suess, S. T.↗
NASA NTRS2003

In Vitro Studies on Space Radiation-Induced Delayed Genetic Responses: Shielding Effects

Understanding the radiation risks involved in spaceflight is of considerable importance, especially with the long-term occupation of ISS and the planned crewed exploration missions. Several independent causes may contribute to the overall risk to astronauts exposed to the complex space environment, such as exposure to GCR as well as SPES. Protons and high-Z energetic particles comprise the GCR spectrum and may exert considerable biological effects even at low fluence. There are also considerable uncertainties associated with secondary particle effects (e.g. HZE fragments, neutrons etc.). The interaction of protons and high-LET particles with biological materials at all levels of biological organization needs to be investigated fully in order to establish a scientific basis for risk assessment. The results of these types of investigation will foster the development of appropriately directed countermeasures. In this study, we compared the biological responses to proton irradiation presented to the target cells as a monoenergetic beam of particles of complex composition delivered to cells outside or inside a tissue phantom head placed in the United States EVA space suit helmet. Measurements of chromosome aberrations, apoptosis, and the induction of key proteins were made in bone marrow from CBA/CaJ and C57BL/6 mice at early and late times post exposure to radiation at 0, 0.5, 1 and 2 Gy while inside or outside of the helmet. The data showed that proton irradiation induced transmissible chromosomal/genomic instability in haematopoietic stem cells in both strains of mice under both irradiation conditions and especially at low doses. Although differences were noted between the mouse strains in the degree and kinetics of transforming growth factor-beta 1 and tumor necrosis factor-alpha secretion, there were no significant differences observed in the level of the induced instability under either radiation condition, or for both strains of mice. Consequently, when normalized to physical dose, the monoenergetic proton field present inside the helmet-protected phantom produced equivalent biological responses, when compared to unshielded cells, as measured by the induction of delayed genetic effects in murine haematopoietic stem cells.

Kadhim, Munira A.↗
NASA NTRS2007

A Novel Method for Breath Capture Inside a Space Suit

Any non-robotic mission to the Mars surface will need to rely on various life support technologies. The large metabolic generation rate and low tolerance to elevated levels of carbon dioxide (CO2) in the Mars atmosphere make CO2 removal one of the preeminent tasks in this domain. In addition, these same features provide a strong impetus for using regenerable CO2 removal technologies. In the past, many of these regenerable technologies have relied on the low partial pressure CO2 surrounding the vehicle to provide an ultimate sink for removing this gas contaminant, however any Mars mission will have to overcome the presence of the Mars atmosphere. This paper describes the investigation of methods to capture the exhaled CO2 from a suited crewmember before it becomes diluted with the high volumetric air flow present within the space suit. Typical expired air contains CO2 partial pressures in the range of 20-35 mm Hg. This research investigated methods to capture this high partial pressure CO2 prior to its dilution with the low partial pressure CO2 ventilation flow. Specifically the research looked at potential designs for a collection cup for use inside the space suit helmet. This collection cup should not be considered the same as a breathing mask typical of that worn by firefighters, etc. Instead, the collection cup is a non-contact device that makes use of detailed analyses of the ventilation flow environment within the helmet. The research used a detailed Computational Fluid Dynamic (CFD) code called Fluent to provide modeling of the various gas species (CO2, water vapor, O2) as they pass through a helmet. This same model was used to numerically evaluate several different collection cup designs for this same CO2 segregation effort.

Paul, Heather↗
NASA NTRS2007

Mobile Collection and Automated Interpretation of EEG Data

A system that would comprise mobile and stationary electronic hardware and software subsystems has been proposed for collection and automated interpretation of electroencephalographic (EEG) data from subjects in everyday activities in a variety of environments. By enabling collection of EEG data from mobile subjects engaged in ordinary activities (in contradistinction to collection from immobilized subjects in clinical settings), the system would expand the range of options and capabilities for performing diagnoses. Each subject would be equipped with one of the mobile subsystems, which would include a helmet that would hold floating electrodes (see figure) in those positions on the patient s head that are required in classical EEG data-collection techniques. A bundle of wires would couple the EEG signals from the electrodes to a multi-channel transmitter also located in the helmet. Electronic circuitry in the helmet transmitter would digitize the EEG signals and transmit the resulting data via a multidirectional RF patch antenna to a remote location. At the remote location, the subject s EEG data would be processed and stored in a database that would be auto-administered by a newly designed relational database management system (RDBMS). In this RDBMS, in nearly real time, the newly stored data would be subjected to automated interpretation that would involve comparison with other EEG data and concomitant peer-reviewed diagnoses stored in international brain data bases administered by other similar RDBMSs.

Mintz, Frederick↗
NASA NTRS2007

Infrared Imaging System for Studying Brain Function

A proposed special-purpose infrared imaging system would be a compact, portable, less-expensive alternative to functional magnetic resonance imaging (fMRI) systems heretofore used to study brain function. Whereas a typical fMRI system fills a large room, and must be magnetically isolated, this system would fit into a bicycle helmet. The system would include an assembly that would be mounted inside the padding in a modified bicycle helmet or other suitable headgear. The assembly would include newly designed infrared photodetectors and data-acquisition circuits on integrated-circuit chips on low-thermal-conductivity supports in evacuated housings (see figure) arranged in multiple rows and columns that would define image coordinates. Each housing would be spring-loaded against the wearer s head. The chips would be cooled by a small Stirling Engine mounted contiguous to, but thermally isolated from, the portions of the assembly in thermal contact with the wearer s head. Flexible wires or cables for transmitting data from the aforementioned chips would be routed to an integrated, multichannel transmitter and thence through the top of the assembly to a patch antenna on the outside of the helmet. The multiple streams of data from the infrared-detector chips would be sent to a remote site, where they would be processed, by software, into a three-dimensional display of evoked potentials that would represent firing neuronal bundles and thereby indicate locations of neuronal activity associated with mental or physical activity. The 3D images will be analogous to current fMRI images. The data would also be made available, in real-time, for comparison with data in local or internationally accessible relational databases that already exist in universities and research centers. Hence, this system could be used in research on, and for the diagnosis of response from the wearer s brain to physiological, psychological, and environmental changes in real time. The images would also be stored in a relational database for comparison with corresponding responses previously observed in other subjects.

Mintz, Frederick↗
NASA NTRS2010

Exploration EVA Purge Flow Assessment

An advanced future spacesuit will require properly sized suit and helmet purge flow rates in order to sustain a crew member with a failed Portable Life Support System (PLSS) during an Extravehicular Activity (EVA). A computational fluid dynamics evaluation was performed to estimate the helmet purge flow rate required to washout carbon dioxide and to prevent the condensing ("fogging") of water vapor on the helmet visor. An additional investigation predicted the suit purge flow rate required to provide sufficient convective cooling to keep the crew member comfortable. This paper summarizes the results of these evaluations.

Navarro, Moses↗
NASA NTRS2011

Exploration EVA Purge Flow Assessment

An advanced future spacesuit will require properly sized suit and helmet purge flow rates in order to sustain a crew member with a failed Portable Life Support System (PLSS) during an Extravehicular Activity (EVA). A computational fluid dynamics evaluation was performed to estimate the helmet purge flow rate required to washout carbon dioxide and to prevent the condensing ("fogging") of water vapor on the helmet visor. An additional investigation predicted the suit purge flow rate required to provide sufficient convective cooling to keep the crew member comfortable. This paper summarizes the results of these evaluations.

Navarro, Moses↗
NASA NTRS2023

Developing a Hybrid Space Suit Simulator as a Research Tool for Assessing Extravehicular Activity Relevant Workload

Suited testing time is limited and hard to come by, expensive, and requires a whole team to operate and monitor the suit; however, pressurized spacesuits are not always necessary for initial developmental efforts or assessment of informatics. The Human Physiology, Performance, Protection & Operations Laboratory (H-3PO) at NASA Johnson Space Center (JSC) is developing a Hybrid Space Suit Simulator (HS3) to support characterization of human performance during planetary surface exploration analogs. The primary goal of HS3 is to create a low cost, modular, and unpressurized suit simulator for use as a research tool which provides relevant physical and cognitive workload approximations with EVA-like immersion during planetary extravehicular activity (EVA) simulations. HS3 consists of a soft suit, communication, thermal control, gloves, boots, helmet, and integrated bioinformatics/sensors. The modular design of HS3 allows it to be modified to support test objectives as needed. HS3 enables H-3PO and NASA to complete critical human health and performance testing to address open risks and knowledge gaps in a timely, repeatable, and controlled manner. Four engineering runs were completed with HS3 as a baseline for capability. General workload was assessed while traversing on a passive treadmill and conducting geology tasks. Liquid cooling temperature, suit temperature, and metabolic rates were collected during one extended three-hour engineering run. For the duration of the engineering run the suit temperature was 26.6 ± 1.58 °C while suit humidity was 53.7 ± 5.11 %. Helmet temperature was higher than suit temperature at 27.8 ± 1.58 °C. Helmet humidity was lower than average suit humidity at 50.12 ± 11.3 °C. The liquid cooling temperature remained stable at 22.4 ± 1.62 °C. Resting metabolic rate was 597 ± 88 BTU/hr while metabolic rate increased during traverse tasks at 1500 ± 319 BTU/hr and geology tasks at 921 ± 129 BTU/hr. Following the engineering runs, a characterization study will be conducted. The subjects will perform EVA-like scenarios in both a shirtsleeve only and donned HS3, consisting of EVA task circuit focused on traversing, geological rock sampling, and task board manipulation. The characterization study will provide data capability for implementing HS3 in analog EVA testing environments.

Monica Hew↗
NASA NTRSDate not supplied

Updates and Correlation of EMU System-Level Model (SINDA EMU)

During United States Extravehicular Activity 80 (US EVA 80), water was observed in the helmet of an Extravehicular Mobility Unit (EMU) during cabin repressurization. One of the primary methods of determining the likely cause of this failure was through a comparison of EVA 80 to other historical EVAs using an analytical approach. The Systems Improved Numerical Differential Analysis EMU model (SINDA EMU) is a system-level model of the EMU that was used in this investigation. SINDA EMU was initially developed and correlated to test data in the 1980s. Since its conception, SINDA EMU has been continually adjusted based on new test data and changes to the EMU design. To support the water in the helmet investigation, SINDA EMU needed to be further updated and recorrelated to ensure accurate results. These changes included changing the primary carbon dioxide (CO2) removal technology, implementing logic to allow for re-evaporation of sweat runoff from the liquid cooling and ventilation garment (LCVG), and improving the transient modeling capabilities. To validate the implementation of these adjustments, SINDA EMU was correlated to test data from the 1990s and human-in-the-loop (HITL) testing from 2014. These updates and correlation efforts proved that SINDA EMU is an effective tool for investigating the EVA 80 water in the helmet failure event.

Noah Lial Andersen↗
NASA NTRSDate not supplied

Extravehicular Mobility Unit System-Level Model (SINDA EMU) Usage for Operational Mitigations in Support of US EVA 80

During United States Extravehicular Activity 80 (US EVA 80), water was observed in the helmet of an Extravehicular Mobility Unit (EMU) during cabin repressurization. Through a comparative analysis and Test, Teardown, and Evaluation (TT&E) of this EMU, the most likely cause of the US EVA 80 water failure was determined to be sublimator carryover caused by a comparatively high latent load (water vapor production by the crewmember). High latent load can be reduced by the crewmember adjusting the thermal control valve (TCV) setting on the EMU to prevent the onset of significant sweating. To reduce the risk of high latent load leading to water in the helmet, a potential warning system was developed using the Systems Improved Numerical Differencing Analyzer EMU model (SINDA EMU). The goal of this warning system is to alert the crewmember when they are producing a high latent load and recommend adjustment of the TCV to increase cooling. This warning system was designed to ensure high risk conditions are avoided while simultaneously preventing a system that warns the crewmember too frequently. Theoretical tests of the warning system through modeling calculated that if the warning system were used during US EVA 80, the total latent load could have been reduced by up to 33% which would have significantly reduced the risk of water in the helmet. This analysis also investigated the effectiveness of the warning system on EVAs that occurred after US EVA 80.

Noah Andersen↗
NASA NTRS1971

Experiment T002: Manual navigation sightings

Navigation-type measurements through the window of the stabilized Gemini 12 spacecraft by the use of a hand-held sextant are reported. The major objectives were as follows: (1) to evaluate the ability of the crewmen to make accurate navigational measurements by the use of simple instruments in an authentic space flight environment; (2) to evaluate the operational feasibility of the measurement techniques by the use of the pressure suit with the helmet off and with the helmet on and the visor closed; (3) to evaluate operational problems associated with the spacecraft environment; and (4) to validate ground based simulation techniques by comparison of the inflight results with base line data obtained by the pilot by the use of simulators and celestial targets from ground based observatories.

Smith, D.↗
NASA NTRS1971

Experimental system for the control of surgically induced infections, operating and maintenance instructions D203613-004

An experimental portable system used to control surgically induced infections is described. The system consists of a portable clean room comprised of a laminar flow filter system consistent with Federal standards; a helmet-shoulder pad assembly; a communication system; a helmet ventilation system; a transparent walled enclosure; and surgical gowns. Guidelines for the set up and operation of such equipment are given along with corrective steps to use in case of system malfunctions. Cleaning procedures, maintenance requirements, and disassembly and transfer particulars are included.

Tevebaugh, M. D.↗