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NASA Technical Reports Server (NTRS) (686.401 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 321.858

  1. Biomechanical Modeling of the Deadlift Exercise to Improve the Efficacy of Resistive Exercise Microgravity Countermeasures

    Sheehan, C. C.; Thompson, W. K.; Funk, J. H.; Lewandowski, B. E.; Gallo, C. A.; Perusek, G. P.; Funk, N. W.; DeWitt, J. K.; Jagodnik, K. M.
    During long-duration spaceflight missions, astronauts exposure to microgravity without adequate countermeasures can result in losses of muscular strength and endurance, as well as loss of bone mass. As a countermeasure to this challenge, astronauts engage in resistive exercise during spaceflight to maintain their musculoskeletal function. The Hybrid Ultimate Lifting Kit (HULK) has been designed as a prototype exercise device for an exploration-class vehicle; the HULK features a much smaller footprint than previous devices such as the Advanced Resistive Exercise Device (ARED) on the International Space Station (ISS), which makes the HULK suitable for extended spaceflight missions in vehicles with limited...

  2. Spacecraft Mission Design for the Mitigation of the 2017 PDC Hypothetical Asteroid Threat

    Englander, Jacob A.; Lyzhoft, Joshua; Barbee, Brent W.; Chodas, Paul W.; Sarli, Bruno V.
    This paper presents a detailed mission design analysis results for the 2017 Planetary Defense Conference (PDC) Hypothetical Asteroid Impact Scenario, documented at https://cneos.jpl.nasa.gov/ pd/cs/pdc17/. The mission design includes campaigns for both reconnaissance (flyby or rendezvous) of the asteroid (to characterize it and the nature of the threat it poses to Earth) and mitigation of the asteroid, via kinetic impactor deflection, nuclear explosive device (NED) deflection, or NED disruption. Relevant scenario parameters are varied to assess the sensitivity of the design outcome, such as asteroid bulk density, asteroid diameter, momentum enhancement factor, spacecraft launch vehicle, and mitigation system type. Different trajectory...

  3. Spacecraft Mission Design for the Mitigation of the 2017 PDC Hypothetical Asteroid Threat

    Barbee, Brent W.; Sarli, Bruno V.; Englander, Jacob A.; Lyzhoft, Josh; Chodas, Paul W.
    This paper presents a detailed mission design analysis results for the 2017 Planetary Defense Conference (PDC) Hypothetical Asteroid Impact Scenario, documented at https:cneos.jpl.nasa.govpdcspdc17. The mission design includes campaigns for both reconnaissance (flyby or rendezvous) of the asteroid (to characterize it and the nature of the threat it poses to Earth) and mitigation of the asteroid, via kinetic impactor deflection, nuclear explosive device (NED) deflection, or NED disruption. Relevant scenario parameters are varied to assess the sensitivity of the design outcome, such as asteroid bulk density, asteroid diameter, momentum enhancement factor, spacecraft launch vehicle, and mitigation system type. Different trajectory types...

  4. Increased Jet Noise Due to a "Nominally Laminar" State of Nozzle Exit Boundary Layer

    Zaman, K. B. M. Q.
    A set of 2-in. diameter nozzles is used to investigate the effect of varying exit boundary layer state on the radiated noise from high-subsonic jets. It is confirmed that nozzles involving turbulent boundary layers are the quietest while nozzles involving a "nominally laminar" boundary layer are loud especially on the high-frequency side of the sound pressure level spectrum. The latter boundary layer state involves a "Blasius-like" mean velocity profile but higher turbulence intensities compared to those in the turbulent state. The higher turbulence in the initial region of the jet shear layer leads to increased high-frequency noise. The results strongly...

  5. Increased Jet Noise Due to a "Nominally Laminar" State of Nozzle Exit Boundary Layer

    Zaman, K. B. M. Q.
    A set of 2-inch diameter nozzles is used to investigate the effect of varying exit boundary layer state on the radiated noise from high-subsonic jets. It is confirmed that nozzles involving turbulent boundary layers are the quietest while nozzles involving a nominally-laminar boundary layer are loud especially on the high-frequency side of the sound pressure level spectrum. The latter boundary layer state involves a Blasius-like mean velocity profile but higher turbulence intensities compared to those in the turbulent state. The higher turbulence in the initial region of the jet shear layer leads to increased high-frequency noise. The results strongly suggest...

  6. Solar Coronal Jets: Overview and Update

    Sterling, Alphonse C.
    No abstract available

  7. Measurements of Cosmic-Ray Proton and Helium Spectra from the Bess-Polar Long-Duration Balloon Flights Over Antarctica

    Horikoshi, A.; Orito, R.; Hams, T.; Thakur, N.; Nozaki, M.; Abe, K.; Matsukawa, Y.; Kumazawa, T.; Itazaki, A.; Makida, Y.; Streitmatter, R. E.; Hasegawa, M.; Lee, M. H.; Sakai, K.; Matsuda, S.; Fuke, H.; Kim, K. C.; Haino, S.; Myers, Z.; Ormes, J. F.; Mitchell, J. W.; Matsumoto, K.; Kusumoto, A.; Sasaki, M.; Nishimura, J.
    The BESS-Polar Collaboration measured the energy spectra of cosmic-ray protons and helium during two long-duration balloon flights over Antarctica in December 2004 and December 2007, at substantially different levels of solar modulation. Proton and helium spectra probe the origin and propagation history of cosmic rays in the galaxy, and are essential to calculations of the expected spectra of cosmic-ray antiprotons, positrons, and electrons from interactions of primary cosmic-ray nuclei with the interstellar gas, and to calculations of atmospheric muons and neutrinos. We report absolute spectra at the top of the atmosphere for cosmic-ray protons in the kinetic energy range 0.2-160...

  8. Gravity Field of the Orientale Basin from the Gravity Recovery and Interior Laboratory (GRAIL) Mission

    McGovern, Patrick J.; Jansen, Johanna C.; Wieczorek, Mark A.; Andrews-Hanna, Jeffrey C.; Asmar, Sami W.; Lemoine, Frank G.; Solomon, Sean C.; Matsuyama, Isamu; Taylor, G. Jeffrey; Keane, James T.; Melosh, H. Jay; Head, James W.; Park, Ryan S.; Smith, David E.; Zuber, Maria T.; Kiefer, Walter S.; Watkins, Michael M.; Mazarico, Erwan; Goossens, Sander; Neumann, Gregory A.; Soderblom, Jason M.; Miljkovic, Katarina; Yuan, Dah-Ning; Williams, James G.; Johnson, Brandon C.; Nimmo, Francis; Phillips, Roger J.; Konopliv, Alexander S.
    Tracking by the GRAIL spacecraft has yielded a model of the gravitational field of the Orientale basin at 3-5-km horizontal resolution. The diameter of the basin excavation cavity closely matches that of the Inner Depression. A volume of at least (3.4 +/- 0.2) x10(exp 6) cu km of crustal material was removed and redistributed during basin formation; the outer edges of the zone of uplifted mantle slope downward and outward by 20deg-25deg. There is no preserved evidence of the transient crater that would reveal the basin's maximum volume, but its diameter may now be calculated from the observed structure to...

  9. Inland and Near Shore Water Profiles Derived from the High Altitude Multiple Altimeter Beam Experimental Lidar (MABEL)

    Jasinski, Michael F.; Stengel, Eric; Brunt, Kelly; Cook, William B.; Ondrusek, Michael; Stoll, Jeremy D.
    The Advanced Topographic Laser Altimeter System (ATLAS) on the Ice, Cloud, and Land Elevation Satellite (ICESat-2) mission is a six beam, low energy, high repetition rate, 532 nm laser transmitter with photon counting detectors. Although designed primarily for detecting height changes in icecaps, sea ice and vegetation, the polar-orbital satellite will observe global surface water during its designed three year life span, including inland water bodies, coasts, and open oceans. In preparation for the mission, an ICESat-2 prototype or the Multiple Altimeter Beam Experimental Lidar (MABEL), was built and flown on high altitude aircraft experiments over a range of inland...

  10. VEGGIE and the VEG-01 Hardware Validation Test

    Massa, Gioia
    This is a presentation to NASA HQ for a lunch-and-learn detailing the Veggie testing and results. Space Life and Physical Sciences plans to record this presentation and make it available for public display.

  11. Impacts of Interactive Stratospheric Chemistry on Antarctic and Southern Ocean Climate Change in the Goddard Earth Observing System Version 5 (GEOS-5)

    Perlwitz, Judith; Douglass, Anne R.; Newman, Paul A.; Li, Feng; Pawson, Steven; Vikhliaev, Yury V.; Waugh, Darryn W.
    Stratospheric ozone depletion plays a major role in driving climate change in the Southern Hemisphere. To date, many climate models prescribe the stratospheric ozone layer's evolution using monthly and zonally averaged ozone fields. However, the prescribed ozone underestimates Antarctic ozone depletion and lacks zonal asymmetries. In this study we investigate the impact of using interactive stratospheric chemistry instead of prescribed ozone on climate change simulations of the Antarctic and Southern Ocean. Two sets of 1960-2010 ensemble transient simulations are conducted with the coupled ocean version of the Goddard Earth Observing System Model, version 5: one with interactive stratospheric chemistry and...

  12. Plasma Observations During the Mars Atmospheric Plume Event of March-april 2012

    Holmstrom, M.; Opgenoorth, H. J.; Edberg, N. J. T.; Lester, M.; Hall, B. E. S.; Gurnett, D. A.; Witasse, O.; Sanchez-Cano, B.; Barabash, S.; Morgan, D. D.; Way, Michael Joseph; Andrews, D. J.; Ramstad, R.
    We present initial analysis and conclusions from plasma observations made during the reported Mars Dust plume event of March - April 2012. During this period, multiple independent amateur observers detected a localized, high-altitude plume over the Martian dawn terminator [Sanchez-Lavega7 et al., Nature, 2015, doi:10.1038nature14162], the origin of which remains to be explained. We report on in-situ measurements of ionospheric plasma density and solar wind parameters throughout this interval made by Mars Express, obtained over the surface region, but at the opposing terminator. We tentatively conclude that the formation and/or transport of this plume to the altitudes where it was...

  13. Preliminary Analysis of the Performance of the Landsat 8/OLI Land Surface Reflectance Product

    Claverie, Martin; Vermote, Eric; Franch, Belen; Justice, Chris
    The surface reflectance, i.e., satellite derived top of atmosphere (TOA) reflectance corrected for the temporally, spatially and spectrally varying scattering and absorbing effects of atmospheric gases and aerosols, is needed to monitor the land surface reliably. For this reason, the surface reflectance, and not TOA reflectance, is used to generate the greater majority of global land products, for example, from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) sensors. Even if atmospheric effects are minimized by sensor design, atmospheric effects are still challenging to correct. In particular, the strong impact of aerosols in the visible...

  14. Cryogenic Fluid Management Technology Development Roadmaps

    Stephens, J. R.; Johnson, W. L.
    Advancement in Cryogenic Fluid Management (CFM) Technologies is essential for achieving NASA's future long duration missions. Propulsion systems utilizing cryogens are necessary to achieve mission success. Current State Of the Art (SOA) CFM technologies enable cryogenic propellants to be stored for several hours. However, some envisioned mission architectures require cryogens to be stored for two years or longer. The fundamental roles of CFM technologies are long term storage of cryogens, propellant tank pressure control and propellant delivery. In the presence of heat, the cryogens will "boil-off" over time resulting in excessive pressure buildup, off-nominal propellant conditions, and propellant loss. To...

  15. Test and Analysis of Solid Rocket Motor Nozzle Ablative Materials

    Clayton, J. Louie
    Asbestos free solid motor internal insulation samples were tested at the MSFC Hyperthermal Facility. Objectives of the test were to gather data for analog characterization of ablative and in-depth thermal performance of rubber materials subject to high enthalpy/pressure flow conditions. Tests were conducted over a range of convective heat fluxes for both inert and chemically reactive sub-sonic free stream gas flow. Instrumentation included use of total calorimeters, thermocouples, and a surface pyrometer for surface temperature measurement. Post-test sample forensics involved measurement of eroded depth, charred depth, total sample weight loss, and documentation of the general condition of the eroded profile....

  16. Characterizing the 2016 Perseid Meteor Shower Outburst

    Moser, D. E.; Molau, S.; Stober, G.; Schult, C.; Ehlert, S. R.; Blaauw, R. C.; Kingery, A. M.
    The Perseid meteor shower has been observed for millennia and known for its visually spectacular meteors and occasional outbursts. The Perseids were expected to outburst in 2016, primarily due to particles released during the 1862 and 1479 revolutions of Comet Swift-Tuttle. NASA's Meteoroid Environment Office predicted the timing, strength and duration of the outburst for spacecraft risk using the MSFC Meteoroid Stream Model. A double peak was predicted, with an outburst displaying a ZHR of 210 +/- 50 at 00:30 UTC Aug 12, and a traditional peak approximately 12 hours later with rates still heightened from the outburst. Video, visual,...

  17. Luminous Efficiency of Hypervelocity Meteoroid Impacts on the Moon Derived from the 2015 Geminid Meteor Shower

    Ehlert, S. R.; Suggs, R. M.; Moser, D. E.
    Meteoroids cannot be observed directly because of their small size. In-situ measurements of the meteoroid environment are rare and have very small collecting areas. The Moon, in contrast, has a large collecting area and therefore can be used as a large meteoroid detector for gram-kilogram sized particles. Meteoroids striking the Moon create an impact flash observable by Earth-based telescopes. Their kinetic energy is converted to luminous energy with some unknown luminous efficiency (v), which is likely a function of meteoroid velocity (among other factors). This luminous efficiency is imperative to calculating the kinetic energy and mass of the meteoroid, as...

  18. The Velocity and Density Distribution of Earth-Intersecting Meteoroids: Implications for Environment Models

    Brown, P. G.; Blaauw, R. C.; Moorhead, A. V.; Cooke, W. J.; Campbell-Brown, M. D.; Moser, D. E.
    Meteoroids are known to damage spacecraft: they can crater or puncture components, disturb a spacecraft's attitude, and potentially create secondary electrical effects. Because the damage done depends on the speed, size, density, and direction of the impactor, accurate environment models are critical for mitigating meteoroid-related risks. Yet because meteoroid properties are derived from indirect observations such as meteors and impact craters, many characteristics of the meteoroid environment are uncertain. In this work, we present recent improvements to the meteoroid speed and density distributions. Our speed distribution is derived from observations made by the Canadian Meteor Orbit Radar. These observations are...

  19. A Comparison of Damaging Meteoroid and Orbital Debris Fluxes in Earth Orbit

    Cooke, William; Moorhead, Althea V.; Matney, Mark; Vavrin, Andrew
    Low Earth orbit is populated with a substantial amount of orbital debris, and it is usually assumed that the flux from these objects contributes to most of the hypervelocity particle risk to spacecraft in this region. The meteoroid flux is known to be dominant at very low altitudes (less than 300 km), where atmospheric drag rapidly removes debris, and at very high altitudes (beyond geostationary), where debris is practically non-existent. The vagueness of these boundaries and repeated questions from spacecraft projects have prompted this work, in which we compare the fluxes of meteoroids and orbital debris capable of producing a...

  20. Meteor Shower Forecasting for Spacecraft Operations

    Campbell-Brown, Margaret D.; Moorehead, Althea V.; Cooke, William J.
    Although sporadic meteoroids are a much greater hazard to spacecraft than shower meteoroids in general, meteor showers can significantly increase the risk of damage over short time periods. Because showers are brief, it is sometimes possible to mitigate the risk operationally, which requires accurate predictions of shower activity. NASA's Meteoroid Environment Office generates an annual meteor shower forecast that describes the variations in the near-Earth meteoroid flux produced by meteor showers, which presents the shower flux both in absolute terms and relative to the sporadic ux. The shower forecast incorporates model predictions of annual variations in shower activity and quotes...

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