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NASA Technical Reports Server (NTRS) (668,169 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.

NASA Center for AeroSpace Information (CASI) (513,494) NIX Images (81,938)


Mostrando recursos 1 - 20 de 302,134

1. Elastic Constants of Solids and Fluids with Initial Pressure via a Unified Approach Based on Equations-of-State - Cantrell, John H.
The second and third-order Brugger elastic constants are obtained for liquids and ideal gases having an initial hydrostatic pressure p(sub 1). For liquids the second-order elastic constants are C(sub 11) = A + p(sub 1), C(sub 12) = A -- p(sub 1), and the third-order constants are C(sub 111) = --(B + 5A + 3p(sub 1)), C(sub 112) = --(B + A -- p(sub 1)), and C(sub 123) = A -- B -- p1, where A and B are the Beyer expansion coefficients in the liquid equation of state. For ideal gases the second order constants are C(sub 11) =...

2. On the Effects of Modeling As-Manufactured Geometry: Toward Digital Twin - Ingraffea, Anthony; Heber, Gerd; Hochhalter, Jacob; Cerrone, Albert
Asimple, nonstandardized material test specimen,which fails along one of two different likely crack paths, is considered herein.The result of deviations in geometry on the order of tenths of amillimeter, this ambiguity in crack pathmotivates the consideration of asmanufactured component geometry in the design, assessment, and certification of structural systems.Herein, finite elementmodels of as-manufactured specimens are generated and subsequently analyzed to resolve the crack-path ambiguity. The consequence and benefit of such a "personalized" methodology is the prediction of a crack path for each specimen based on its as-manufactured geometry, rather than a distribution of possible specimen geometries or nominal geometry.The consideration...

3. Remote Sensing of Cloud Top Height from SEVIRI: Analysis of Eleven Current Retrieval Algorithms - Joro, S.; Francis, P. N.; Heidinger, A.; Meirink, J. F.; Platnick, S.; Kniffka, A.; Baum, B.; Hamann, U.; Minnis, P.; Lutz, H.-J.; Wind, G.; Lockhoff, M.; Le Gleau, H.; Bugliaro, L.; Bennartz, R.; Walther, A.; Thoss, A.; Palikonda, R.; Watts, P.; Roebeling, R.; Derrien, M.
The role of clouds remains the largest uncertainty in climate projections. They influence solar and thermal radiative transfer and the earth's water cycle. Therefore, there is an urgent need for accurate cloud observations to validate climate models and to monitor climate change. Passive satellite imagers measuring radiation at visible to thermal infrared (IR) wavelengths provide a wealth of information on cloud properties. Among others, the cloud top height (CTH) - a crucial parameter to estimate the thermal cloud radiative forcing - can be retrieved. In this paper we investigate the skill of ten current retrieval algorithms to estimate the CTH...

4. Comparison of Marine Boundary Layer Cloud Properties from CERES-MODIS Edition 4 and DOE ARM AMF Measurements at the Azores - Xi, Baike; Minnis, Patrick; Sun-Mack, Sunny; Dong, Xiquan
Marine boundary layer (MBL) cloud properties derived from the NASA Clouds and the Earth's Radiant Energy System (CERES) project using Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) data are compared with observations taken at the Department of Energy Atmospheric Radiation Measurement (ARM) Mobile Facility at the Azores (AMF-Azores) site from June 2009 through December 2010. Cloud properties derived from ARM ground-based observations were averaged over a 1 h interval centered at the satellite overpass time, while the CERES-MODIS (CM) results were averaged within a 30 km30 km grid box centered over the Azores site. A total of 63 daytime...

5. Reconciliation of Halogen-Induced Ozone Loss with the Total-Column Ozone Record - Wang, H. J.; von Clarmann, T.; Fioletov, V. E.; Reader, M. C.; Remsberg, E.; Plummer, D. A.; Scinocca, J. F.; Shepherd, T. G.; Hegglin, M. I.
The observed depletion of the ozone layer from the 1980s onwards is attributed to halogen source gases emitted by human activities. However, the precision of this attribution is complicated by year-to-year variations in meteorology, that is, dynamical variability, and by changes in tropospheric ozone concentrations. As such, key aspects of the total-column ozone record, which combines changes in both tropospheric and stratospheric ozone, remain unexplained, such as the apparent absence of a decline in total-column ozone levels before 1980, and of any long-term decline in total-column ozone levels in the tropics. Here we use a chemistry-climate model to estimate changes...

6. MDO and Cross-Disciplinary Practice in R&D: A Portrait of Principles and Current Practice - Papalambros, Panos Y.; Rivas McGowan, Anna-Maria; Baker, Wayne E.
For several decades, Multidisciplinary Design Optimization (MDO) has served an important role in aerospace engineering by incorporating physics based disciplinary models into integrated system or sub-system models for use in research, development, (R&D) and design. This paper examines MDO's role in facilitating the integration of the researchers from different single disciplines during R&D and early design of large-scale complex engineered systems (LaCES) such as aerospace systems. The findings in this paper are summarized from a larger study on interdisciplinary practices and perspectives that included considerable empirical data from surveys, interviews, and ethnography. The synthesized findings were derived by integrating the...

7. Hurricane Imaging Radiometer (HIRAD) - Jones, W. Linwood; Biswas, Sayak Krishna; Cecil, Daniel Joseph
No abstract available

8. Martian Chlorobenzene Identified by Curiosity in Yellowknife Bay: Evidence for the Preservation of Organics in a Mudstone on Mars - McAdam, A.; Mahaffy, P.; Martin, M.; Steele, A.; Squyres, S.; Brickenhoff, W.; DesMarais, D.; Stern, J.; Summons, R.; Glavin, Daniel P.; Pavlov, A.; Atreya, S.; Buch, A.; Grotzinger, J.; Freissinet, Caroline; Archer, D.; Eigenbrode, J.; Franz, H.; Malespin, C.; Brunner, A.; Miller, K.; Ming, D.; Conrad, P.; Kashyap, S.; Dworkin, J.
The Sample Analysis at Mars (SAM) instrument on the Curiosity rover is designed to determine the inventory of organic and inorganic volatiles thermally evolved from solid samples using a combination of evolved gas analysis (EGA), gas chromatography mass spectrometry (GCMS), and tunable laser spectroscopy. The first sample analyzed by SAM at the Rocknest (RN) aeolian deposit revealed chlorohydrocarbons derived primarily from reactions between a martian oxychlorine phase (e.g. perchlorate) and terrestrial carbon from N-methyl-N-(tert-butyldimethylsilyl) trifluoroacetamide (MTBSTFA) vapor present in the SAM instrument background. No conclusive evidence for martian chlorohydrocarbons in the RN sand was found. After RN, Curiosity traveled to...

9. Plume Collection Strategies for Icy World Sample Return - Williams, P.; Tsou, P.; Neveu, M.; Anbar, A. D.; Glavin, D. P.
Three icy worlds in the solar system display evidence of pluming activity. Water vapor and ice particles emanate from cracks near the south pole of Saturn's moon Enceladus. The plume gas contains simple hydrocarbons that could be fragments of larger, more complex organics. More recently, observations using the Hubble and Herschel space telescopes have hinted at transient water vapor plumes at Jupiter's moon Europa and the dwarf planet Ceres. Plume materials may be ejected directly from possible sub-surface oceans, at least on Enceladus. In such oceans, liquid water, organics, and energy may co-exist, making these environments habitable. The venting of...

10. Climate Change Effects on Agriculture: Economic Responses to Biophysical Shocks - Havlik, Petr; Elliott, Joshua; Nelson, Gerald C.; Fujimori, Shinichiro; Deryng, Delphine; Heyhoe, Edwina; Ahammad, Helal; Valin, Hugo; Hasegawa, Tomoko; Sands, Ronald D.
Agricultural production is sensitive to weather and thus directly affected by climate change. Plausible estimates of these climate change impacts require combined use of climate, crop, and economic models. Results from previous studies vary substantially due to differences in models, scenarios, and data. This paper is part of a collective effort to systematically integrate these three types of models. We focus on the economic component of the assessment, investigating how nine global economic models of agriculture represent endogenous responses to seven standardized climate change scenarios produced by two climate and five crop models. These responses include adjustments in yields, area,...

11. Data Recipes: Toward Creating How-To Knowledge Base for Earth Science Data - Shen, Suhung; Beaty, Tammy; Lynnes, Chris; Acker, James G.
Both the diversity and volume of Earth science data from satellites and numerical models are growing dramatically, due to an increasing population of measured physical parameters, and also an increasing variety of spatial and temporal resolutions for many data products. To further complicate matters, Earth science data delivered to data archive centers are commonly found in different formats and structures. NASA data centers, managed by the Earth Observing System Data and Information System (EOSDIS), have developed a rich and diverse set of data services and tools with features intended to simplify finding, downloading, and working with these data. Although most...

12. Alaska: Glaciers of Kenai Fjords National Park and Katmai National Park and Preserve - Hall, Dorothy K.; Chien, Janet Y. L.; Giffens, Bruce A.
There are hundreds of glaciers in Kenai Fjords National Park (KEFJ) and Katmai National Park and Preserve (KATM) covering over 2,276 sq km of park land (ca. 2000). There are two primary glacierized areas in KEFJ (the Harding Icefield and the Grewingk-Yalik Glacier Complex) and three primary glacierized areas in KATM (the Mt. Douglas area, the Kukak Volcano to Mt. Katmai area, and the Mt. Martin area). Most glaciers in these parks terminate on land, though a few terminate in lakes. Only KEFJ has tidewater glaciers, which terminate in the ocean. Glacier mapping and analysis of the change in glacier...

13. Multiple Absorption Components in the Post-Periastron He I P Cygni Absorption Troughs of Eta Carinae - Corcoran, Michael; Hamaguchi, Kenji; Moffat, Anthony; Groh, Jose; Teodoro, Mairan; Gull, Ted; Madura, Tom; Damineli, Augusto; Richardson, Noel D.; Russell, Christopher; St.-Jean, Lucas; Walter, Frederick M.
We have obtained more than 100 high spectral resolution (R approx. 90,000) spectra of the massive binary star eta Carinae since 2012 in an effort to continue our orbital and long-term echelle monitoring of this extreme binary (Richardson et al. 2010, AJ, 139, 1534) with the CHIRON spectrograph on the CTIO 1.5 m telescope (Tokovinin et al. 2013, PASP, 125, 1336) in the 4550-7500A region. We increased our monitoring efforts and observation frequency as the periastron event of 2014 has approached, and resumed observations in October. We note that since mid-October, we have observed unusual multiple absorption components in the...

14. A Systems Engineering Approach to Architecture Development - Di Pietro, David A.
Architecture development is often conducted prior to system concept design when there is a need to determine the best-value mix of systems that works collectively in specific scenarios and time frames to accomplish a set of mission area objectives. While multiple architecture frameworks exist, they often require use of unique taxonomies and data structures. In contrast, this paper characterizes architecture development using terminology widely understood within the systems engineering community. Using a notional civil space architecture example, it employs a multi-tier framework to describe the enterprise level architecture and illustrates how results of lower tier, mission area architectures integrate into...

15. Fundamentals for Team Based Rehearsals and the Differences Between Low Earth and Deep Space Missions - Cifuentes, Juan; Gomez-Rosa, Carlos; Wasiak, Francis; Alfonzo, Agustin
Presentation to be presented at the 2015 IEEE Aerospace Conference, Big Sky, Montana, March 7-14-2015.Rehearsals are mission level readiness tests that exercise personnel, operational process, and flight products, in a near flight like environment. The program is started 6-9 months prior to launch and is used to ensure the final as built system will meet mission goals (i.e. validation). On Deep Space missions you rehearse cruise activities post launch!Focus on critical activities to the mission, (i.e. propulsive maneuvers, instrument commissioning and any first time events or coordinating activities that involve major stakeholders).

16. Adjoint Methods for Adjusting Three-Dimensional Atmosphere and Surface Properties to Fit Multi-Angle Multi-Pixel Polarimetric Measurements - Cairns, Brian; Martin, William G.; Bal, Guillaume
This paper derives an efficient procedure for using the three-dimensional (3D) vector radiative transfer equation (VRTE) to adjust atmosphere and surface properties and improve their fit with multi-angle/multi-pixel radiometric and polarimetric measurements of scattered sunlight. The proposed adjoint method uses the 3D VRTE to compute the measurement misfit function and the adjoint 3D VRTE to compute its gradient with respect to all unknown parameters. In the remote sensing problems of interest, the scalar-valued misfit function quantifies agreement with data as a function of atmosphere and surface properties, and its gradient guides the search through this parameter space. Remote sensing of...

17. Lunar Flashlight: Mapping Lunar Surface Volatiles Using a Cubesat - Paige, David A.; Hayne, Paul O.; Paine, Christopher G.; Cohen, Barbara A.; Greenhagen, Benjamin T.
No abstract available

18. Features of Afterbody Radiative Heating for Earth Entry - Johnston, Christopher O.; Brandis, Aaron
Radiative heating is identified as a major contributor to afterbody heating for Earth entry capsules at velocities above 10 km/s. Because of rate-limited electron-ion recombination processes, a large fraction of the electronically-excited N and O atoms produced in the high temperature/pressure forebody remain as they expand into the afterbody region, which results in significant afterbody radiation. Large radiative heating sensitivities to electron-impact ionization rates and escape factors are identified. Ablation products from a forebody ablator are shown to increase the afterbody radiation by as much as 40%. The tangent-slab radiation transport approach is shown to over-predict the radiative flux by...

19. Modeling Increased Complexity and the Reliance on Automation: FLightdeck Automation Problems (FLAP) Model - Shih, Ann T.; Ancel, Ersin
This paper highlights the development of a model that is focused on the safety issue of increasing complexity and reliance on automation systems in transport category aircraft. Recent statistics show an increase in mishaps related to manual handling and automation errors due to pilot complacency and over-reliance on automation, loss of situational awareness, automation system failures and/or pilot deficiencies. Consequently, the aircraft can enter a state outside the flight envelope and/or air traffic safety margins which potentially can lead to loss-of-control (LOC), controlled-flight-into-terrain (CFIT), or runway excursion/confusion accidents, etc. The goal of this modeling effort is to provide NASA's Aviation...

20. A Next Generation Air Monitor: Combining Orion and ISS Requirements for a Common Major Constituent Analyzer - Burchfield, David E.; Tissandier, Michael; Lewis, John F.; Niu, William Hsein-Chi
The Major Constituent Analyzer (MCA) is a mass spectrometer-based instrument designed to provide critical monitoring of six major atmospheric constituents; nitrogen, oxygen, hydrogen, carbon dioxide, methane, and water vapor on-board the International Space Station. The analyzer has been an integral part of the Environmental Control and Life Support System (ECLSS) since the station went on-line. The Orion Air Monitor (OAM) was derived from the MCA and heavily optimized for reduced mass, lower power, faster water vapor response, and maintenance-free operation. The resulting OAM is approximately the size of the analyzer portion of the MCA, orbital-replacement unit 02 (ORU 02), while...

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