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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

Initial Sensorimotor and Cardiovascular Data Acquired from Soyuz Landings: Establishing a Functional Performance Recovery Time Constant

INTRODUCTION Testing of crew responses following long-duration flights has not been previously possible until a minimum of more than 24 hours after landing. As a result, it has not been possible to determine the trend of the early recovery process, nor has it been possible to accurately assess the full impact of the decrements associated with long-duration flight. To overcome these limitations, both the Russian and U.S. programs have implemented joint testing at the Soyuz landing site. This International Space Station research effort has been identified as the functional Field Test, and represents data collect on NASA, Russian, European Space Agency, and Japanese Aerospace Exploration Agency crews. RESEARCH The primary goal of this research is to determine functional abilities associated with long-duration space flight crews beginning as soon after landing as possible on the day of landing (typically within 1 to 1.5 hours). This goal has both sensorimotor and cardiovascular elements. To date, a total of 15 subjects have participated in a 'pilot' version of the full 'field test'. The full version of the 'field test' will assess functional sensorimotor measurements included hand/eye coordination, standing from a seated position (sit-to-stand), walking normally without falling, measurement of dynamic visual acuity, discriminating different forces generated with the hands (both strength and ability to judge just noticeable differences of force), standing from a prone position, coordinated walking involving tandem heel-to-toe placement (tested with eyes both closed and open), walking normally while avoiding obstacles of differing heights, and determining postural ataxia while standing (measurement of quiet stance). Sensorimotor performance has been obtained using video records, and data from body worn inertial sensors. The cardiovascular portion of the investigation has measured blood pressure and heart rate during a timed stand test in conjunction with postural ataxia testing (quiet stance sway) as well as cardiovascular responses during sensorimotor testing on all of the above measures. We have also collected motion sickness data associated with each of the postflight tests. When possible rudimentary cerebellar assessment was undertaken. In addition to the immediate post-landing collection of data, postflight data has been acquired twice more within 24 hours after landing and measurements continue until sensorimotor and cardiovascular responses have returned to preflight normative values (approximately 60 days postflight). SUMMARY The level of functional deficit observed in the crew tested to date is more severe than expected, clearly triggered by the acquisition of gravity loads immediately after landing when the demands for crew intervention in response to emergency operations will be greatest. Measureable performance parameters such as ability to perform a seat egress, recover from a fall or the ability to see clearly when walking, and related physiologic data (orthostatic responses) are required to provide an evidence base for characterizing programmatic risks and the degree of variability among crewmembers for exploration missions where the crew will be unassisted after landing. Overall, these early functional and related physiologic measurements will allow the estimation of nonlinear sensorimotor and cardiovascular recovery trends that have not been previously captured.

Reschke, M. F.↗
DOE OSTI2021

Investigation of Gallium–Boron Spin-On Codoping for poly-Si/SiO x Passivating Contacts

A doping technique for p-type poly-Si/SiOx passivating contacts using a spin-on method for different mixtures of Ga and B glass solutions is presented. Effects of solution mixing ratios on the contact performance (implied open circuit voltage iV oc , contact resistivity ..rho..c) are investigated. For all as-annealed samples at different drive-in temperatures, increasing the percentage of Ga in the solution shows a decrement in iV oc (from ~680 to ~610 mV) and increment in ..rho..c (from ~3 to ~800 mO cm 2 ). After a hydrogenation treatment by depositing a SiN x /AlO x stack followed by forming gas annealing, all samples show improved iVoc (~700 mV with Ga-B co-doped, and ~720 mV with all Ga). Interestingly, when co-doping Ga with B, even a small amount of B in the mixing solution shows negative effects on the surface passivation. Active and total dopant profiles obtained by electrical capacitance voltage and secondary-ion mass spectrometry measurements, respectively, reveal a relatively low percentage of electrically-active Ga and B in the poly-Si and Si layers. Overall, these results help understand the different features of the two dopants: a low ρ c with B, a good passivation with Ga, their degree of activation inside the poly-Si and Si layers, and the annealing effects.

14 SOLAR ENERGY↗
NASA NTRS2006

Space Life Sciences at NASA: Spaceflight Health Policy and Standards

In January 2005, the President proposed a new initiative, the Vision for Space Exploration. To accomplish the goals within the vision for space exploration, physicians and researchers at Johnson Space Center are establishing spaceflight health standards. These standards include fitness for duty criteria (FFD), permissible exposure limits (PELs), and permissible outcome limits (POLs). POLs delineate an acceptable maximum decrement or change in a physiological or behavioral parameter, as the result of exposure to the space environment. For example cardiovascular fitness for duty standards might be a measurable clinical parameter minimum that allows successful performance of all required duties. An example of a permissible exposure limit for radiation might be the quantifiable limit of exposure over a given length of time (e.g. life time radiation exposure). An example of a permissible outcome limit might be the length of microgravity exposure that would minimize bone loss. The purpose of spaceflight health standards is to promote operational and vehicle design requirements, aid in medical decision making during space missions, and guide the development of countermeasures. Standards will be based on scientific and clinical evidence including research findings, lessons learned from previous space missions, studies conducted in space analog environments, current standards of medical practices, risk management data, and expert recommendations. To focus the research community on the needs for exploration missions, NASA has developed the Bioastronautics Roadmap. The Bioastronautics Roadmap, NASA's approach to identification of risks to human space flight, revised baseline was released in February 2005. This document was reviewed by the Institute of Medicine in November 2004 and the final report was received in October 2005. The roadmap defines the most important research and operational needs that will be used to set policy, standards (define acceptable risk), and implement an overall Risk Management and Analysis process. Currently NASA is drafting spaceflight health standards for neurosensory alterations, space radiation exposure, behavioral health, muscle atrophy, cardiovascular fitness, immunological compromise, bone demineralization, and nutrition.

Davis, Jeffrey R.↗
NASA NTRS1999

Quantitative EEG Monitoring of Vigilance: Effects of Sleep Deprivation, Circadian Phase and Sympathetic Activation

Shuttle astronauts typically sleep only 6 to 6.5 hours per day while in orbit. This sleep loss is related to recurrent sleep cycle shifting--due to mission-dependent orbital mechanics and mission duration requirements-- and associated circadian displacement of sleep, the operational demands of space flight, noise and space motion sickness. Such sleep schedules are known to produce poor subjective sleep quality, daytime sleepiness, reduced attention, negative mood, slower reaction times, and impaired daytime alertness. Countermeasures to allow crew members to obtain an adequate amount of sleep and maintain adequate levels of neurobehavioral performance are being developed and investigated. However, it is necessary to develop methods that allow effective and attainable in-flight monitoring of vigilance to evaluate the effectiveness of these countermeasures and to detect and predict online critical decrements in alertness/performance. There is growing evidence to indicate that sleep loss and associated decrements in neurobehavioral function are reflected in the spectral composition of the electroencephalogram (EEG) during wakefulness as well as in the incidence of slow eye movements recorded by the electro-oculogram (EOG). Further-more, our preliminary data indicated that these changes in the EEG during wakefulness are more pronounced when subjects are in a supine posture, which mimics some of the physiologic effects of microgravity. Therefore, we evaluate the following hypotheses: (1) that during a 40-hour period of wakefulness (i.e., one night of total sleep deprivation) neurobehavioral function deteriorates, the incidence of slow eye-movements and EEG power density in the theta frequencies increases especially in frontal areas of the brain; (2) that the sleep deprivation induced deterioration of neurobehavioral function and changes in the incidence of slow eye movements and the spectral composition of the EEG are more pronounced when subjects are in a supine position; and (3) that based on assessment of slow-eye movements and quantitative on-line topographical analyses of EEG during wakefulness an EEG and or EOG parameter can be derived/constructed which accurately predicts changes in neurobehavioral function.

Dijk, Derk-Jan↗
NASA NTRS1950

Effect of Ram-jet Pressure Pulsations on Supersonic-diffuser Performance

Experimental study of effects of combustion roughness and controlled mechanical oscillations on diffuser operation was conducted on an 8-inch ram jet at Mach number 1.87. Within experimental accuracy, the optimum mean combustion-chamber static pressure occurred when the maximum instantaneous static pressure equalled the optimum steady-flow value and the corresponding decrement in optimum mean static pressure was equal to one-half the total amplitude of the pressure pulsations. A marked attenuation of amplitude of cold-buzz pressure fluctuations was effected over limited range of subcritical diffuser operation by means of properly tuned rotating disk located in combustion chamber.

Connors, James F↗
NASA NTRS1974

Effect of bed rest and exercise on body balance

A battery of 11 body balance tests was administered to 7 men before and after 14 days of bedrest. Seven men who had not undergone bed rest served as controls. During bed rest, each subject underwent daily either isotonic, isometric, or no leg exercise. The results showed that, for the bed-rested no exercise, isotonic exercise, and isometric exercise groups, 2 weeks of bed rest produces significant body balance decrements on 3, 4, and 5 of the 11 tests, respectively. Daily leg exercise did not prevent the debilitating effects of bed rest on body balance. After bed rest, balance skill was relearned rapidly so that in most tests, performance had reached prebed-rest levels by the third recovery day. These data suggest that balance impairment is not due to loss of muscular strength in the legs but, perhaps, to a bed-rest-related change in the neurally coded information to postural control centers.

Haines, R. F.↗
NASA NTRS1987

Measuring pilot workload in a motion base simulator. III - Synchronous secondary task

This experiment continues earlier research of Kantowitz et al. (1983) conducted in a GAT-1 motion-base trainer to evaluate choice-reaction secondary tasks as measures of pilot work load. The earlier work used an asynchronous secondary task presented every 22 sec regardless of flying performance. The present experiment uses a synchronous task presented only when a critical event occurred on the flying task. Both two- and four-choice visual secondary tasks were investigated. Analysis of primary flying-task results showed no decrement in error for altitude, indicating that the key assumption necessary for using a choice secondary task was satisfied. Reaction times showed significant differences between 'easy' and 'hard' flight scenarios as well as the ability to discriminate among flight tasks.

Kantowitz, Barry H.↗
NASA NTRS2011

Impact of Virtual Environments on Sensorimotor Coordination and User Safety

One critical unresolved issue related to the safe use of virtual environments (VEs) is maladaptive sensorimotor coordination following exposure to VEs. Moving visual displays used in VEs, especially in the absence of concordant vestibular signals leads to adaptive responses during VE exposure, but maladaptive responses following return to the normal environment. In the current set of investigations, we examined the effect of HMD and dome VE displays on eye-head-hand coordination, gaze holding and postural equilibrium. Subjects (61) performed a navigation and a pick and place task. Further, we compared 30 min and 60 min exposures across 3 days (each separated by 1 day). A subset of these results will be presented. In general, we found significant decrements in all three measures following exposure to the VEs. In addition, we found that these disturbances generally recovered within 1-2 hrs and decreased across days. These findings suggest the need for post-VE monitoring of sensorimotor coordination and for developing a set of recommendations for users concerning activities that are safe to engage in following use of a VE.

Harm, Deborah L.↗
DOE OSTI2020

Prototype for Unclassified Algorithm

Continuing previous efforts to investigate and develop the Unclassified Radioisotope Algorithm, the goal of the FY19-FY20 effort was to develop a prototype detector system which uses the algorithm to confirm warhead attributes related to the presence of either weapons grade plutonium (WGPu) or highly enriched uranium (HEU). The final deliverable is a prototype attribute measurement system built with common, commercially available gamma radiation detector components, capable of confirming the presence of specific, complex radioactive sources of interest, without the collection and storage of gamma energy spectra. This is accomplished by processing each gamma pulse as it is received, applying weight values based on the energy and incrementing or decrementing scalar counters which can be compared with expected values to determine if the measured source is consistent with WGPu or HEU. This report documents the design of the prototype system as well as the development of the algorithm and performance testing results. While the previously conceptualized, simple algorithm resulted in a prohibitive amount of false positives, the goal for a simple attribute measurement system capable of verifying Ba-133 and Ra-226 (weapons grade plutonium and highly enriched uranium surrogate testing sources) at over 95% accuracy with sub 5% false positive rate was demonstrated.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
NASA NTRS2001

Effects of Three-Day Bed Rest on Physiological Responses to Graded Exercise in Endurance Athletes, Body Builders and Sedentary Men

To test the hypotheses that short-term bed rest (BR) deconditioning influences metabolic, cardiorespiratory and neurohormonal responses to exercise and that these effects depend on the subjects' training status 12 sedentary men, and 10 endurance- and 10 strength-trained athletes were submitted to three-day BR. Before and after BR they performed incremental exercise test until volitional exhaustion. Respiratory gas exchange and HR were recorded continuously and stroke volume (SV) was measured at submaximal loads. Blood was taken for lactate [LA], adrenaline [A], noradrenaline, [NA], renting activity (PRA), growth hormone [hGH], testosterone and cortisol determination. Reduction of peak oxygen uptake (VO2peak) after BR was greater in the endurance athletes (than in the remaining groups (17 % vs. 100%). Decrements in VO2peak correlated positively with the initial values (r = 0.73, p less than 0.001). Resting and exercise respiratory exchange ratios were increased in athletes. Cardiac output was unchanged by BR in all groups, but exercise HR was increased and SV diminished in the sedentary subjects. The submaximal [LA] and [LA] thresholds were decreased the in endurance athletes from 71 to 60 %VO2 peak (p less than 0.001); they also had an earlier increase in [NA], and an attenuated increase in [hGH), and accentuated PRA and cortisol elevations during exercise. These effects were insignificant in the remaining subjects. In conclusion: reduction of exercise performance and modifications in neurohormonal response to exercise after BR depend on the previous level and mode of physical training, being the most pronounced in the endurance athletes.

Smorawinski, J.↗
NASA NTRS2001

Effects of Three-Day Bed Rest on Physiological Responses to Graded Exercise in Endurance Athletes, Body Builders and Sedentary Men

To test the hypotheses that short-term bed rest (BR) deconditioning influences metabolic, cardiorespiratory and neurohormonal responses to exercise and that these effects depend on the subjects' training status, 12 sedentary men, and 10 endurance- and 10 strength-trained athletes were submitted to three-day BR. Before and after BR they performed incremental exercise tests until volitional exhaustion. Respiratory gas exchange and HR were recorded continuously and stroke volume (SV) was measured at submaximal loads. Blood was taken for lactate [LA], adrenaline [A], noradrenaline [NA], renin activity (PRA), growth hormone [hGH], testosterone and cortisol determination. Reduction of peak oxygen uptake (V02peak) after BR was greater in the endurance athletes than in the remaining groups (17 % vs. 10%). Decrements in VO2peak correlated positively with the initial values (r = 0.73, p is less than 0.001). Resting and exercise respiratory exchange ratios were increased in athletes. Cardiac output was unchanged by BR in all groups, but exercise HR was increased and SV diminished in the sedentary subjects. The submaximal [LA] and [LA] thresholds were decreased the in endurance athletes from 71 to 60% V02 peak (p is less than0.001), they also had an earlier increase in [NA], an attenuated increase in [hGH], and accentuated PRA and cortisol elevations during exercise. These effects were insignificant in the remaining subjects. In conclusion: reduction of exercise performance and modifications in neurohormonal response to exercise after BR depend on the previous level and mode of physical training, being the most pronounced in the endurance athletes.

Smorawinski, J.↗
NASA NTRS2011

Acquisition of Skill Proficiency Over Multiple Sessions of a Novel Rover Simulation

Following long-duration exploration transits, adaptive changes in sensorimotor function may impair the crew's ability to safely perform manual control tasks such as operating pressurized rovers. Postflight performance will also be influenced by the level of preflight skill proficiency they have attained. The purpose of this study was to characterize the acquisition of skills in a motion-based rover simulation over multiple sessions, and to investigate the effects of varying the simulation scenarios. METHODS: Twenty healthy subjects were tested in 5 sessions, with 1-3 days between sessions. Each session consisted of a serial presentation of 8 discrete tasks to be completed as quickly and accurately as possible. Each task consisted of 1) perspective-taking, using a map that defined a docking target, 2) navigation toward the target around a Martian outpost, and 3) docking a side hatch of the rover to a visually guided target. The simulator utilized a Stewart-type motion base (CKAS, Australia), single-seat cabin with triple scene projection covering 150 deg horizontal by 50 deg vertical, and joystick controller. Subjects were randomly assigned to a control group (tasks identical in the first 4 sessions) or a varied-practice group. The dependent variables for each task included accuracy toward the target and time to completion. RESULTS: The greatest improvements in time to completion occurred during the docking phase. The varied-practice group showed more improvement in perspective-taking accuracy. Perspective-taking accuracy was also affected by the relative orientation of the rover to the docking target. Skill acquisition was correlated with self-ratings of previous gaming experience. DISCUSSION: Varying task selection and difficulty will optimize the preflight acquisition of skills when performing novel operational tasks. Simulation of operational manual control will provide functionally relevant evidence regarding the impact of sensorimotor adaptation on early surface operations and what countermeasures are needed. Learning Objective: The use of a motion-based simulation to investigate decrements in the proficiency to operate pressurized rovers during early surface operations of space exploration missions, along with the acquisition of skill proficiency needed during the preflight phase of the mission.

Dean, S. L.↗
NASA NTRS2005

Postural Control Disturbances Produced By Exposure to HMD and Dome Vr Systems

Two critical and unresolved human factors issues in VR systems are: 1) potential "cybersickness", a form of motion sickness which is experienced in virtual worlds, and 2) maladaptive sensorimotor performance following exposure to VR systems. Interestingly, these aftereffects are often quite similar to adaptive sensorimotor responses observed in astronauts during and/or following space flight. Most astronauts and cosmonauts experience perceptual and sensorimotor disturbances during and following space flight. All astronauts exhibit decrements in postural control following space flight. It has been suggested that training in virtual reality (VR) may be an effective countermeasure for minimizing perceptual and/or sensorimotor disturbances. People adapt to consistent, sustained alterations of sensory input such as those produced by microgravity, and experimentally-produced stimulus rearrangements (e.g., reversing prisms, magnifying lenses, flight simulators, and VR systems). Adaptation is revealed by aftereffects including perceptual disturbances and sensorimotor control disturbances. The purpose of the current study was to compare disturbances in postural control produced by dome and head-mounted virtual environment displays. Individuals recovered from motion sickness and the detrimental effects of exposure to virtual reality on postural control within one hour. Sickness severity and initial decrements in postural equilibrium decreases over days, which suggests that subjects become dual-adapted over time. These findings provide some direction for developing training schedules for VR users that facilitate adaptation, and address safety concerns about aftereffects.

Harm, D. L.↗
NASA NTRS2001

Effects of 3-day bed rest on physiological responses to graded exercise in athletes and sedentary men

To test the hypotheses that short-term bed-rest (BR) deconditioning influences metabolic, cardiorespiratory, and neurohormonal responses to exercise and that these effects depend on the subjects' training status, 12 sedentary men and 10 endurance- and 10 strength-trained athletes were submitted to 3-day BR. Before and after BR they performed incremental exercise test until volitional exhaustion. Respiratory gas exchange and heart rate (HR) were recorded continuously, and stroke volume (SV) was measured at submaximal loads. Blood was taken for lactate concentration ([LA]), epinephrine concentration ([Epi]), norepinephrine concentration ([NE]), plasma renin activity (PRA), human growth hormone concentration ([hGH]), testosterone, and cortisol determination. Reduction of peak oxygen uptake (VO(2 peak)) after BR was greater in the endurance athletes than in the remaining groups (17 vs. 10%). Decrements in VO(2 peak) correlated positively with the initial values (r = 0.73, P < 0.001). Resting and exercise respiratory exchange ratios were increased in athletes. Cardiac output was unchanged by BR in all groups, but exercise HR was increased and SV diminished in the sedentary subjects. The submaximal [LA] and [LA] thresholds were decreased in the endurance athletes from 71 to 60% VO(2 peak) (P < 0.001); they also had an earlier increase in [NE], an attenuated increase in [hGH], and accentuated PRA and cortisol elevations during exercise. These effects were insignificant in the remaining subjects. In conclusion, reduction of exercise performance and modifications in neurohormonal response to exercise after BR depend on the previous level and mode of physical training, being the most pronounced in the endurance athletes.

NASA Center ARC↗
NASA NTRS1976

YF-16 flight flutter test procedures

The Random Decrement technique (Randomdec) was incorporated in procedures for flight testing of the YF-16 lightweight fighter prototype. Damping values obtained substantiate the adequacy of the flutter margin of safety. To confirm the structural modes which were being excited, a spectral analysis of each channel was performed using the AFFTC time/data 1923/50 time series analyzer. Inflight test procedure included the careful monitoring of strip charts, three axis pulses, rolls, and pullups.

Brignac, W. J.↗
NASA NTRS1977

The effects of prolonged exposure to weightlessness on postural equilibrium

A postflight postural equilibrium rail tests on spacecrews was used to prove a pronounced decrement in ability to maintain an upright posture after prolonged exposure to weightlessness. Support for the hypothesis that central neural reorganization occurs in response to environmental change is obtained when postflight decrease in stability on the rails and the time course for recovery are compared with preflight performance.

Homick, J. L.↗
NASA NTRS2016

Novel Musculoskeletal Loading System for Small Exercise Devices

Long duration spaceflight places astronauts at increased risk for muscle strain and bone fracture upon return to a 1-g or partial gravity environment. Functionally limiting decrements in musculoskeletal health are likely during Mars proving-ground and Earth-independent missions given extended transit times and the vehicle limitations for exercise devices (low-mass, small volume, little to no power). This is particularly alarming for exploration missions because astronauts will be required to perform novel and physically demanding tasks (i.e. vehicle egress, exploration, and habitat building activities) on unfamiliar terrain. Accordingly, NASA's exploration roadmap identifies the need for development of small exercise equipment that can prevent musculoskeletal atrophy and has the ability to assess musculoskeletal health at multiple time points during long-duration missions.

Downs, Meghan↗
DOE OSTI2023

A heat flux sensor leveraging the transverse Seebeck effect in elemental antimony

Certain configurations of anisotropic single crystal materials can generate a thermoelectric voltage orthogonal to an induced temperature gradient. This phenomenon is known as the Transverse Seebeck Effect (TSE) and can be leveraged to fabricate simple and robust heat flux sensors. Only a small number of materials have been considered as TSE-based transducers and, among these, few have been developed into sensors with ruggedization against chemical and mechanical degradation. Here, we report on the fabrication and characterization of a rugged TSE-based heat flux sensor using prismatic antimony single crystals. The heat flux sensor was tested under static and dynamic heating scenarios. The sensor has a linear responsivity of 16.8 µV/(W/cm2) to heat fluxes spanning more than two orders of magnitude and a time constant of 4.4 s. The sensor’s response to localized heating, probed with a laser scanning technique, validated that the transduction mechanism is primarily the TSE by ruling out a sizable contribution from the conventional Seebeck effect. Finite element analysis corroborated that components used in the sensor package are the primary determinants of the time constant and the decrement of the responsivity from its theoretical maximum. Design principles that may be applied to elicit a faster transient response or higher responsivity are proposed. Furthermore, the results establish single crystal antimony as a promising transducer material for heat flux measurement systems and demonstrate potential effects of ruggedization on sensor performance.

36 MATERIALS SCIENCE↗