Recursos de colección

NASA Technical Reports Server (NTRS) (685.125 recursos)

The NTRS is a valuable resource for students, educators, researchers, and the public for access to NASA's current and historical technical literature since it was first released in 1994. NTRS provides access to approximately 500K aerospace related citations, 90K full-text online documents, and 111K images and videos. NTRS numbers continues to grow over time as new scientific and technical information (STI) is created or funded by NASA. The type of information found in NTRS include: conference papers, images, journal articles, photos, meeting papers, movies, patents, research reports, and technical videos.

Mostrando recursos 41 - 60 de 320.544

  1. What is Eating Ozone? Thermal Reactions between SO2 And O3: Implications for Icy Environments

    Loeffler, Mark J.; Hudson, Reggie L.
    Laboratory studies are presented, showing for the first time that thermally driven reactions in solid H2O+SO2+O3 mixtures can occur below 150 K, with the main sulfur-containing product being bisulfate (HSO4(-)). Using a technique not previously applied to the low-temperature kinetics of either interstellar or solar system ice analogs, we estimate an activation energy of 32 kJ per mol for HSO4(-) formation. These results show that at the temperatures of the Jovian satellites, SO2 and O3 will efficiently react making detection of these molecules in the same vicinity unlikely. Our results also explain why O3 has not been detected on Callisto...

  2. Investigation of Deuterium Loaded Materials Subject to X-Ray Exposure

    Pines, Vladimir; Becks, Michael D.; Daniels, Christopher C.; Steinetz, Bruce M.; Chait, Arnon; Hendricks, Robert C.; Pines, Marianna; Martin, Richard E.; Benyo, Theresa L.; Kamm, Tracy R.; Penney, Nicholas; Forsley, Lawrence P.
    Results are presented from an exploratory study involving x-ray irradiation of select deuterated materials. Titanium deuteride plus deuterated polyethylene, deuterated polyethylene alone, and for control, hydrogen-based polyethylene samples and nondeuterated titanium samples were exposed to x-ray irradiation. These samples were exposed to various energy levels from 65 to 280 kV with prescribed electron flux from 500 to 9000 A impinging on a tungsten braking target, with total exposure times ranging from 55 to 280 min. Gamma activity was measured using a high-purity germanium (HPGe) detector, and for all samples no gamma activity above background was detected. Alpha and beta activities...

  3. Effects of Spaceflight on Venous and Arterial Compliance

    Ribeiro, L. C.; Macias, B. R.; Lee, S. M. C.; Stenger, M. B.; Laurie, S. S.; Ploutz-Snyder, R.; Platts, S. H.; Martin, D. S.
    The visual impairment and intracranial pressure (VIIP) syndrome is a spaceflight-associated set of symptoms affecting more than 50% of American astronauts who have flown International Space Station (ISS) missions. VIIP is defined primarily by visual acuity deficits and anatomical changes to eye structures (e.g. optic disc edema, choroidal folds, and globe flattening) and is hypothesized to be related to elevated intracranial pressure secondary to a cephalad fluid shift. However, ocular symptoms have not been replicated in subjects completing prolonged bed rest, a well-accepted spaceflight analog. Altered vascular compliance along with spaceflight factors such as diet, radiation exposure, or environmental factors...

  4. Estimation of Optimum Stimulus Amplitude for Balance Training using Electrical Stimulation of the Vestibular System

    Rosenberg, M. J.; Bloomberg, J. J.; De Dios, Y. E.; Goel, R.; Mulavara, A. P.; Cohen, H. S.
    Sensorimotor changes such as posture and gait instabilities can affect the functional performance of astronauts after gravitational transitions. Sensorimotor Adaptability (SA) training can help alleviate decrements on exposure to novel sensorimotor environments based on the concept of 'learning to learn' by exposure to varying sensory challenges during posture and locomotion tasks (Bloomberg 2015). Supra-threshold Stochastic Vestibular Stimulation (SVS) can be used to provide one of many challenges by disrupting vestibular inputs. In this scenario, the central nervous system can be trained to utilize veridical information from other sensory inputs, such as vision and somatosensory inputs, for posture and locomotion control....

  5. The Functional Task Test: Results from the One-Year Mission

    Ploutz-Snyder, L. L.; Lee, S. M. C.; May-Phillips, T.; Taylor, L. C.; Stenger, M. B.; Reschke, M. F.; Feiveson, A. H.; Laurie, S.; Batson, C. D.; Mulavara, A. P.; Kofman, I. S.; Buxton, R. E.; Peters, B. T.; Ryder, J. W.; Bloomberg, J. J; Wood, S. J.; Miller, C. A.
    Exposure to the microgravity conditions of spaceflight causes astronauts to experience alterations in multiple physiological systems including sensorimotor disturbances, cardiovascular deconditioning, and loss of muscle mass and strength. Some or all of these changes might affect the ability of crewmembers to perform critical mission tasks immediately after landing on a planetary surface. The goal of our recently completed Functional Task Test (FTT) study was to determine the effects of spaceflight on functional tests that are representative of high priority exploration mission tasks and to identify the key underlying physiological factors that contribute to decrements in performance. The FTT is comprised...

  6. Field Test: Results from the One Year Mission

    Mulavara, A. P.; Kitov, V. V.; Lee, S. M. C.; Stenger, M. B.; Taylor, L. C.; Laurie, S. S.; Reschke, M. F.; Holden, K. L.; Kozlovskaya, I. B.; Rosenberg, M. J. F.; Cerisano, J. M.; Bloomberg, J. J.; De Dios, Y.; Fomina, E. V.; Feiveson, A. H.; Gadd, N. E.; Kofman, I. S.; Lysova, N. Yu; Wood, S. J.; Peters, B. T.; Ribeiro, C.; Rukavishnikov, I. V.; Phillips, T.; Tomilovskaya, E. S.; Fisher, E. A.; Miller, C. A.
    The One Year Mission was designed to aid in determining the effect that extending the duration on orbit aboard the International Space Station (ISS) would have on a number of biological and physiological systems. Two crewmembers were selected to participate in this endeavor, one U.S. On-Orbit Segment (USOS) astronaut and one Russian cosmonaut. The Neuroscience and Cardiovascular and Vision Laboratories at the Johnson Space Center and the Sensory-Motor and Countermeasures Division within the Institute for Biomedical Problems were selected to investigate vestibular, sensorimotor and cardiovascular function with the two long-duration crewmembers using the established methodology developed for the Field Test...

  7. Effects of Acute Exposures to Carbon Dioxide upon Cognitive Functions

    Satish, U.; Basner, M.; Lam, C. W.; Scully, R. R.; Ryder, V. E.; Alexander, D. J.; Young, M.
    Carbon dioxide (CO2) originates from human metabolism and typically remains about 10-fold higher in concentration on the International Space Station (ISS) than at the earth's surface. There have been recurring complaints by crew members of episodes of "mental viscosity" adversely affecting their performance, and there is evidence from the ISS that associates CO2 levels with reports of headaches by crewmembers. Consequently, flight rules have been employed to control CO2 below 3 mm Hg, which is well below the existing Spacecraft Maximum Allowable Concentration (SMAC) of 10 mm Hg for 24-hour exposures, and 5.3 mm Hg for exposures of 7 to...

  8. Detection of DNA Damage by Space Radiation in Human Fibroblasts Flown on the International Space Station

    Wu, Honglu; Feiveson, Alan; Gaza, Ramona; Lu, Tao; Wang, Huichen; Karouia, Fathi; Stodieck, Louis; Stoffle, Nicholas; Wong, Michael; Rohde, Larry; Zhang, Ye; Wilson, Bobby
    Although charged particles in space have been detected with radiation detectors on board spacecraft since the discovery of the Van Allen Belts, reports on the effects of direct exposure to space radiation in biological systems have been limited. Measurement of biological effects of space radiation is challenging due to the low dose and low dose rate nature of the radiation environment, and due to the difficulty in distinguishing the radiation effects from microgravity and other space environmental factors. In astronauts, only a few changes, such as increased chromosome aberrations in their lymphocytes and early onset of cataracts, are attributed primarily...

  9. HRP Chief Scientist's Office: Conducting Research to Enable Deep Space Exploration

    McFather, J. C.; Savelev, I.; Charles, J. B.; Haven, C. P.; Fogarty, J.; Vega, L.; Cromwell, R. L.
    The HRP Chief Scientist's Office sets the scientific agenda for the Human Research Program. As NASA plans for deep space exploration, HRP is conducting research to ensure the health of astronauts, and optimize human performance during extended duration missions. To accomplish this research, HRP solicits for proposals within the U.S., collaborates with agencies both domestically and abroad, and makes optimal use of ISS resources in support of human research. This session will expand on these topics and provide an opportunity for questions and discussion with the HRP Chief Scientist. Presentations in this session will include: NRA solicitations - process improvements...

  10. NASA Space Radiation Protection Strategies: Risk Assessment and Permissible Exposure Limits

    Huff, J. L.; Patel, Z. S.; Simonsen, L. C.
    Permissible exposure limits (PELs) for short-term and career astronaut exposures to space radiation have been set and approved by NASA with the goal of protecting astronauts against health risks associated with ionizing radiation exposure. Short term PELs are intended to prevent clinically significant deterministic health effects, including performance decrements, which could threaten astronaut health and jeopardize mission success. Career PELs are implemented to control late occurring health effects, including a 3% risk of exposure induced death (REID) from cancer, and dose limits are used to prevent cardiovascular and central nervous system diseases. For radiation protection, meeting the cancer PEL is...

  11. Getting to the Heart of Cardiovascular Risk Assessment in Astronauts for Exploration Class Missions

    Shavers, M. R.; Chappell, L.; Huff, J. L.; Semones, E. J.; Milder, C. M.; Simonsen, L. C.; Elgart, S. R.; Patel, Z. S.
    Since the beginning of manned spaceflight, NASA has recognized the potential risk of cardiovascular decrements due to stressors in the space environment. Of particular concern is the effect of space radiation on cardiovascular disease since astronauts will be exposed to higher levels of galactic cosmic rays outside the Earth's protective magnetosphere. To date, only a few studies have examined the effects of heavy ion radiation on cardiovascular disease, and at lower, space-relevant doses, the association between radiation exposure and cardiovascular pathology is more varied and unclear. Furthermore, other spaceflight conditions such as microgravity, circadian shifts, and confinement stress pose unique...

  12. One Giant Leap to Protect All Mankind: An Overview of the Lunar Receiving Laboratory

    Hayes, Judith; Dooling, Jackson
    Motivation. In 1961, President John F. Kennedy charged the nation "to land a man on the moon and return him safely to Earth." Eight years later, the Apollo 11 astronauts splashed down in the Pacific Ocean after this first 8-day journey to the moon. As humans had never ventured to another extraterrestrial body, the U.S. government noted the great uncertainty associated with the unknown exposures related to this historic mission. Overview. With this uncertainty in mind, a newly formed Interagency Committee on Back Contamination (ICBC) was established to review the potential for lunar contaminants and establish the prevention of their...

  13. Behavioral Assessment of Spaceflight Effects on Neurocognitive Performance: Extent and Longevity

    Kreutzberg, G. A.; Wood, S. J.; Campbell, D. J.; Kofman, I. S.; Seidler, R. D.; Bloomberg, J. J.; Taylor, L. C.; Gadd, N. E.; De Dios, Y. E.; Mulavara, A. P.; Peters, B. T.
    Exposure to the microgravity environment during spaceflight missions impacts crewmembers' sensorimotor function. Bock et al. [1] studied the cognitive demands of human sensorimotor performance and dual tasking during long duration missions and concluded that both stress and scarcity of cognitive resources required for sensorimotor adaptation may be responsible for these deficits during spaceflight. Therefore, in consideration of the health and performance of crewmembers in- and post-flight, we are conducting this study to investigate the effects of spaceflight on the extent, longevity and neural bases of sensorimotor, cognitive, and neural changes. The data presented will focus on the behavioral measures that...

  14. Characterization of Variability Sources Associated with Measuring Inspired Carbon Dioxide in Spacesuits

    Fricker, John; Abercromby, Andrew; Bekdash, Omar; Meginnis, Ian; Norcross, Jason
    No abstract available

  15. Evaluation of an Impedance Threshold Device as a VIIP Countermeasure

    Macias, Brandon; Stenger, Michael; Danielson, Richard; Johnston, Smith; Hargens, Alan; Garcia, Kathleen; Sargsyan, Ashot; Kemp, David; Ebert, Douglas
    Visual Impairment/Intracranial Pressure (VIIP) is a top human spaceflight risk for which NASA does not currently have a proven mitigation strategy. Thigh cuffs and lower body negative pressure (LBNP) devices have been or are currently being evaluated as a means to reduce VIIP signs and symptoms, but these methods alone may not provide sufficient relief of cephalic venous congestion and VIIP symptoms. Additionally, current LBNP devices are too large and cumbersome for their systematic use as a countermeasure. Therefore, a novel approach is needed that is easy to implement and provides specific relief of symptoms. This investigation will evaluate an...

  16. Assessment of Intraocular and Systemic Vasculature Pressure Parameters in Simulated Microgravity with Thigh Cuff Countermeasure

    Tepelus, Tudor; Sadda, Jaya; Liu, John; Lee, Stuart M. C.; Sadda, Srinivas; Balasubramanian, Siva; Huang, Alex S.; Macias, Brandon R.; Laurie, Steve S.; Stenger, Michael B.
    Changes in vision have been well documented among astronauts during and after long-duration space flight. One hypothesis is that the space flight induced headward fluid alters posterior ocular pressure and volume and may contribute to visual acuity decrements. Therefore, we evaluated venoconstrictive thigh cuffs as a potential countermeasure to the headward fluid shift-induced effects on intraocular pressure (IOP) and cephalic vascular pressure and volumes.

  17. Laser Communications Relay Demonstration (LCRD) Update and the Path Towards Optical Relay Operations

    Edwards, Bernard L.; Staren, John W.; Israel, David J.
    This paper provides a concept for an evolution of NASA's optical communications near Earth relay architecture. NASA's Laser Communications Relay Demonstration (LCRD), a joint project between NASA's Goddard Space Flight Center (GSFC), the Jet Propulsion Laboratory - California Institute of Technology (JPL), and the Massachusetts Institute of Technology Lincoln Laboratory (MIT LL). LCRD will provide a minimum of two years of high data rate optical communications service experiments in geosynchronous orbit (GEO), following launch in 2019. This paper will provide an update of the LCRD mission status and planned capabilities and experiments, followed by a discussion of the path from...

  18. Lightweight and High-Resolution Astronomical X-Ray Optics Using Single Crystal Silicon

    Kolodziejczak, J. J.; Chan, K. W.; Olsen, L. G.; Saha, T. T.; Gaskin, J. A.; Biskach, M. P.; Zhang, William W.; O'Dell, S. L.; Jones, W. D.; Carter, J. M.; Allgood, K. D.
    Lightweight and high-resolution astronomical x-ray optics using single crystal silicon.

  19. Development and Utilization of Space Fission Power and Propulsion Systems

    Mitchell, Sonny; Kelley, Anthony; Aschenbrenner, Ken; Houts, Mike
    No abstract available

  20. Estimating Consequences of MMOD Penetrations on ISS

    Lear, D.; Evans, H.; Christiansen, E.; Hyde, James
    The threat from micrometeoroid and orbital debris (MMOD) impacts on space vehicles is often quantified in terms of the probability of no penetration (PNP). However, for large spacecraft, especially those with multiple compartments, a penetration may have a number of possible outcomes. The extent of the damage (diameter of hole, crack length or penetration depth), the location of the damage relative to critical equipment or crew, crew response, and even the time of day of the penetration are among the many factors that can affect the outcome. For the International Space Station (ISS), a Monte-Carlo style software code called Manned...

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