NASA Technical Reports Server (NTRS)
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.
Simulated Time Lags of Hinode/XRT and SDO/AIA Lightcurves as an Indication of Loop Heating Scenario - Alexander, C. E.; Winebarger, A. R.; Lionello, R.
The precise nature of the heating mechanism in coronal loops is still a matter of enormous research. We present the results from a 1D hydrodynamic loop simulation of a coronal loop which was run using different parameters such as loops length (50, 200 and 500 Mm), maximum temperature reached (3MK and 10 MK0, and abundances. For each scenario the model outputs were used to calculate the corresponding lightcurves as seen by XRT/Be-thin and various EUV AIA channels. The lag time between the peak of these lightcurves was computed and tested using cross-correlation and plotted as a function of loop length.
Application of Suomi-NPP Green Vegetation Fraction and NUCAPS for Improving Regional Numerical Weather Prediction - Srikishen, Jayanthi; Case, Jonathan L.; Berndt, Emily B.; Zavodsky, Bradley T.
The NASA SPoRT Center is working to incorporate SuomiNPP products into its research and transition activities to improve regional numerical weather prediction (NWP). Specifically, SPoRT seeks to utilize two data products from NOAA/NESDIS: (1) daily global VIIRS green vegetation fraction (GVF), and (2) NOAA Unique CrIS and ATMS Processing System (NUCAPS) temperature and moisture retrieved profiles. The goal of (1) is to improve the representation of vegetation in the Noah land surface model (LSM) over existing climatological GVF datasets in order to improve the landatmosphere energy exchanges in NWP models and produce better temperature, moisture, and precipitation forecasts. The goal...
Probability of US Heat Waves Affected by a Subseasonal Planetary Wave Pattern - Teng, Haiyan; Branstator, Grant; Wang, Hailan; Washington, Warren M.; Meehl, Gerald A.
Heat waves are thought to result from subseasonal atmospheric variability. Atmospheric phenomena driven by tropical convection, such as the Asian monsoon, have been considered potential sources of predictability on subseasonal timescales. Mid-latitude atmospheric dynamics have been considered too chaotic to allow significant prediction skill of lead times beyond the typical 10-day range of weather forecasts. Here we use a 12,000-year integration of an atmospheric general circulation model to identify a pattern of subseasonal atmospheric variability that can help improve forecast skill for heat waves in the United States. We find that heat waves tend to be preceded by 15-20 days...
An Intercomparison of Tropospheric Ozone Retrievals Derived from Two Aura Instruments and Measurements in Western North America in 2006 - Wargan, K.; Doughty, D. C.; Stajner, I.; Hui, W. C. J.; Schoeberl, M. R.; Thompson, A. M.
Two recently developed methods for quantifying tropospheric ozone abundances based on Aura data, the Trajectoryenhanced Tropospheric Ozone Residual (TTOR) and an assimilation of Aura data into Goddard Earth Observing System Version 4 (ASM), are compared to ozone measurements from ozonesonde data collected in April-May 2006 during the INTEX Ozonesonde Network Study 2006 (IONS06) campaign. Both techniques use Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) observations. Statistics on column ozone amounts for both products are presented. In general, the assimilation compares better to sonde integrated ozone to 200 hPa (28.6% difference for TTOR versus 2.7% difference for ASM), and...
Direct Measurement of Dust Attenuation in z approx. 1.5 Star-Forming Galaxies from 3D-HST: Implications for Dust Geometry and Star Formation Rates - Franx, Marijn; Rix, Hans-Walter; Kriek, Mariska; Nelson, Erica J.; Tease, Katherine Whitaker; Brammer, Gabriel B; Wuyts, Stijn; Schreiber, Natascha M. Foerster; Fumagalli, Mattia; Conroy, Charlie; VanDokkum, Pieter G.; Skelton, Rosalind E.; Lundren, Britt; Price, Sedona H.; Momcheva, Ivelina
The nature of dust in distant galaxies is not well understood, and until recently few direct dust measurements have been possible. We investigate dust in distant star-forming galaxies using near-infrared grism spectra of the 3D-HST survey combined with archival multi-wavelength photometry. These data allow us to make a direct comparison between dust towards star-forming regions (measured using Balmer decrements) and the integrated dust properties (derived by comparing spectral energy distributions [SEDs] with stellar population and dust models) for a statistically significant sample of distant galaxies. We select a sample of 163 galaxies between 1.36< or = z< or = 1.5...
High-Lift OVERFLOW Analysis of the DLR-F11 Wind Tunnel Model - Pulliam, Thomas H.; Sclafani, Anthony J.
In response to the 2nd AIAA CFD High Lift Prediction Workshop, the DLR-F11 wind tunnel model is analyzed using the Reynolds-averaged Navier-Stokes flow solver OVERFLOW. A series of overset grids for a bracket-off landing configuration is constructed and analyzed as part of a general grid refinement study. This high Reynolds number (15.1 million) analysis is done at multiple angles-of-attack to evaluate grid resolution effects at operational lift levels as well as near stall. A quadratic constitutive relation recently added to OVERFLOW for improved solution accuracy is utilized for side-of-body separation issues at low angles-of-attack and outboard wing separation at stall...
DNS of Flows over Periodic Hills using a Discontinuous-Galerkin Spectral-Element Method - Murman, Scott M.; Diosady, Laslo T.
Direct numerical simulation (DNS) of turbulent compressible flows is performed using a higher-order space-time discontinuous-Galerkin finite-element method. The numerical scheme is validated by performing DNS of the evolution of the Taylor-Green vortex and turbulent flow in a channel. The higher-order method is shown to provide increased accuracy relative to low-order methods at a given number of degrees of freedom. The turbulent flow over a periodic array of hills in a channel is simulated at Reynolds number 10,595 using an 8th-order scheme in space and a 4th-order scheme in time. These results are validated against previous large eddy simulation (LES) results....
Time-Spectral Rotorcraft Simulations on Overset Grids - Leffell, Joshua I.; Murman, Scott M.; Pulliam, Thomas H.
The Time-Spectral method is derived as a Fourier collocation scheme and applied to NASA's overset Reynolds-averaged Navier-Stokes (RANS) solver OVERFLOW. The paper outlines the Time-Spectral OVERFLOWimplementation. Successful low-speed laminar plunging NACA 0012 airfoil simulations demonstrate the capability of the Time-Spectral method to resolve the highly-vortical wakes typical of more expensive three-dimensional rotorcraft configurations. Dealiasing, in the form of spectral vanishing viscosity (SVV), facilitates the convergence of Time-Spectral calculations of high-frequency flows. Finally, simulations of the isolated V-22 Osprey tiltrotor for both hover and forward (edgewise) flight validate the three-dimensional Time-Spectral OVERFLOW implementation. The Time-Spectral hover simulation matches the time-accurate calculation...
LAVA Simulations for the AIAA Sonic Boom Prediction Workshop - Sozer, Emre; Housman, Jeffrey A.; Kiris, Cetin C.; Moini-Yekta , Shayan
Computational simulations using the Launch Ascent and Vehicle Aerodynamics (LAVA) framework are presented for the First AIAA Sonic Boom Prediction Workshop test cases. The framework is utilized with both structured overset and unstructured meshing approaches. The three workshop test cases include an axisymmetric body, a Delta Wing-Body model, and a complete low-boom supersonic transport concept. Solution sensitivity to mesh type and sizing, and several numerical convective flux discretization choices are presented and discussed. Favorable comparison between the computational simulations and experimental data of nearand mid-field pressure signatures were obtained.
EDSN Development Lessons Learned - Sanchez, Hugo S.; Hanson, John; Chartres, James
The Edison Demonstration of Smallsat Networks (EDSN) is a technology demonstration mission that provides a proof of concept for a constellation or swarm of satellites performing coordinated activities. Networked swarms of small spacecraft will open new horizons in astronomy, Earth observations and solar physics. Their range of applications include the formation of synthetic aperture radars for Earth sensing systems, large aperture observatories for next generation telescopes and the collection of spatially distributed measurements of time varying systems, probing the Earths magnetosphere, Earth-Sun interactions and the Earths geopotential. EDSN is a swarm of eight 1.5U Cubesats with crosslink, downlink and science...
Modular Pulsed Plasma Electric Propulsion System for Cubesats - Gazulla, Oriol Tintore; Agasid, Elwood; Lukas, Joseph; Haque, Sumadra; Keidar, Michael; Mai, Nghia; Uribe, Eddie; Perez, Andres Dono; Teel, George Lewis
Current capabilities of CubeSats must be improved in order to perform more ambitious missions. Electric propulsion systems will play a key role due to their large specific impulse. Compared to other propulsion alternatives, their simplicity allows an easier miniaturization and manufacturing of autonomous modules into the nano and pico-satellite platform. Pulsed Plasma Thrusters (PPTs) appear as one of the most promising technologies for the near term. The utilization of solid and non-volatile propellants, their low power requirements and their proven reliability in the large scale make them great candidates for rapid implementation. The main challenges are the integration and miniaturization...
Enabling Electric Propulsion for Flight - Ginn, Starr
Description of current ARMD projects; Team Seedling project AFRC and LaRC 31ft distributed electric propulsion wing on truck bed up 75 miles per hour for coefficient of lift validation. Convergent Aeronautic Solutions project (new ARMD reorg), sub-project Convergent Electric Propulsion Technologies AFRC, LaRC and GRC, re-winging a 4 passenger Tecnam aircraft with a 31ft distributed electric propulsion wing. Advanced Air Transport Technologies (Fixed Wing), Hybrid Electric Research Theme, developing a series hybrid ironbird and flight sim to study integration and performance challenges in preparation for a 1-2 MW flight project.
Propulsion Electric Grid Simulator (PEGS) for Future Turboelectric Distributed Propulsion Aircraft - Choi, Benjamin B.; Morrison, Carlos; Brown, Gerald V.; Dever, Timothy
NASA Glenn Research Center, in collaboration with the aerospace industry and academia, has begun the development of technology for a future hybrid-wing body electric airplane with a turboelectric distributed propulsion (TeDP) system. It is essential to design a subscale system to emulate the TeDP power grid, which would enable rapid analysis and demonstration of the proof-of-concept of the TeDP electrical system. This paper describes how small electrical machines with their controllers can emulate all the components in a TeDP power train. The whole system model in Matlab/Simulink was first developed and tested in simulation, and the simulation results showed that...
Development and Validation of Linear Alternator Models for the Advanced Stirling Convertor - Lewandowski, Edward; Metscher, Jonathan F.
Two models of the linear alternator of the Advanced Stirling Convertor (ASC) have been developed using the Sage 1-D modeling software package. The first model relates the piston motion to electric current by means of a motor constant. The second uses electromagnetic model components to model the magnetic circuit of the alternator. The models are tuned and validated using test data and compared against each other. Results show both models can be tuned to achieve results within 7% of ASC test data under normal operating conditions. Using Sage enables the creation of a complete ASC model to be developed and...
Test Program for Stirling Radioisotope Generator Hardware at NASA Glenn Research Center - Bolotin, Gary S.; Oriti, Salvatore M.; Lewandowski, Edward J.
Stirling-based energy conversion technology has demonstrated the potential of high efficiency and low mass power systems for future space missions. This capability is beneficial, if not essential, to making certain deep space missions possible. Significant progress was made developing the Advanced Stirling Radioisotope Generator (ASRG), a 140-watt radioisotope power system. A variety of flight-like hardware, including Stirling convertors, controllers, and housings, was designed and built under the ASRG flight development project. To support future Stirling-based power system development NASA has proposals that, if funded, will allow this hardware to go on test at the NASA Glenn Research Center (GRC). While...
Development of NASA's Small Fission Power System for Science and Human Exploration - Creasy, John; Robinson, Chris; Mason, Lee; Poston, David I.; Gibson, Marc A.; McClure, Patrick R.; Bowman, Cheryl
Exploration of our solar system has brought great knowledge to our nation's scientific and engineering community over the past several decades. As we expand our visions to explore new, more challenging destinations, we must also expand our technology base to support these new missions. NASA's Space Technology Mission Directorate is tasked with developing these technologies for future mission infusion and continues to seek answers to many existing technology gaps. One such technology gap is related to compact power systems (greater than 1 kWe) that provide abundant power for several years where solar energy is unavailable or inadequate. Below 1 kWe,...
NASA Glenn Research Center Support of the ASRG Project - Wilson, Scott D.; Wong, Wayne A.
A high efficiency radioisotope power system is being developed for long-duration NASA space science missions. The U.S. Department of Energy (DOE) managed a flight contract with Lockheed Martin Space Systems Company (LMSSC) to build Advanced Stirling Radioisotope Generators (ASRGs), with support from NASA Glenn Research Center (GRC). Sunpower Inc. held two parallel contracts to produce Advanced Stirling Convertors (ASCs), one with DOELockheed Martin to produce ASC-F flight units, and one with GRC for the production of ASC-E3 engineering unit pathfinders that are built to the flight design. In support of those contracts, GRC provided testing, materials expertise, government furnished equipment,...