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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Common Warm Dust Temperatures Around Main Sequence Stars

We compare the properties of warm dust emission from a sample of main-sequence A-type stars (B8-A7) to those of dust around solar-type stars (F5-KO) with similar Spitzer Space Telescope Infrared Spectrograph/MIPS data and similar ages. Both samples include stars with sources with infrared spectral energy distributions that show evidence of multiple components. Over the range of stellar types considered, we obtain nearly the same characteristic dust temperatures (∼ 190 K and ∼60 K for the inner and outer dust components, respectively)-slightly above the ice evaporation temperature for the inner belts. The warm inner dust temperature is readily explained if populations of small grains are being released by sublimation of ice from icy planetesimals. Evaporation of low-eccentricity icy bodies at ∼ 150 K can deposit particles into an inner/warm belt, where the small grains are heated to dust Temperatures of -190 K. Alternatively, enhanced collisional processing of an asteroid belt-like system of parent planetesimals just interior to the snow line may account for the observed uniformity in dust temperature. The similarity in temperature of the warmer dust across our B8-KO stellar sample strongly suggests that dust-producing planetesimals are not found at similar radial locations around all stars, but that dust production is favored at a characteristic temperature horizon.

Morales, Farisa↗
NASA NTRS2017

MIL-HDBK-338-Environmental Conversion Table Correction

In reliability analysis for space launch vehicles, limited data is frequently a challenge due to the pure number of launches. A common solution is to use surrogate historical data of similar components from other industries (military data). The operating environment of the common data may be different from that of the necessary target analysis. The military electronic design handbook (MIL-HDBK-338) has a table for converting Mean Time Between Failure (MTBF) data from one environment to another. However, the table has some discrepancies and rounding of complementary conversions; namely going from environment A to B does not given the same result as going from B to A. This presentation will show the discrepancies in the original conversation table, the greater than expected magnitude, the problem with the updated published table and a suggested corrected table to reference when doing MTBF data environment conversion.

Hark, Frank↗
DOE OSTI2021

Simulations of Events for the LUX-ZEPLIN (LZ) Dark Matter Experiment

The LUX-ZEPLIN dark matter search aims to achieve a sensitivity to the WIMP-nucleon spin-independent cross-section down to (1–2) ×10−12 pb at a WIMP mass of 40 GeV/ c 2 . This paper describes the simulations framework that, along with radioactivity measurements, was used to support this projection, and also to provide mock data for validating reconstruction and analysis software. Of particular note are the event generators, which allow us to model the background radiation, and the detector response physics used in the production of raw signals, which can be converted into digitized waveforms similar to data from the operational detector. Inclusion of the detector response allows us to process simulated data using the same analysis routines as developed to process the experimental data.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS2013

Trajectory Reconstruction and Uncertainty Analysis Using Mars Science Laboratory Pre-Flight Scale Model Aeroballistic Testing

As part of the Mars Science Laboratory (MSL) trajectory reconstruction effort at NASA Langley Research Center, free-flight aeroballistic experiments of instrumented MSL scale models was conducted at Aberdeen Proving Ground in Maryland. The models carried an inertial measurement unit (IMU) and a flush air data system (FADS) similar to the MSL Entry Atmospheric Data System (MEADS) that provided data types similar to those from the MSL entry. Multiple sources of redundant data were available, including tracking radar and on-board magnetometers. These experimental data enabled the testing and validation of the various tools and methodologies that will be used for MSL trajectory reconstruction. The aerodynamic parameters Mach number, angle of attack, and sideslip angle were estimated using minimum variance with a priori to combine the pressure data and pre-flight computational fluid dynamics (CFD) data. Both linear and non-linear pressure model terms were also estimated for each pressure transducer as a measure of the errors introduced by CFD and transducer calibration. Parameter uncertainties were estimated using a "consider parameters" approach.

Lugo, Rafael A.↗
DOE OSTI2020

Open Science principles for accelerating trait-based science across the Tree of Life

Synthesizing trait observations and knowledge across the Tree of Life remains a grand challenge for biodiversity science. Species traits are widely used in ecological and evolutionary science, and new data and methods have proliferated rapidly. Yet accessing and integrating disparate data sources remains a considerable challenge, slowing progress toward a global synthesis to integrate trait data across organisms. Trait science needs a vision for achieving global integration across all organisms. In this perspective, we outline how the adoption of key Open Science principles—open data, open source and open methods—is transforming trait science, increasing transparency, democratizing access and accelerating global synthesis. To enhance widespread adoption of these principles, we introduce the Open Traits Network (OTN), a global, decentralized community welcoming all researchers and institutions pursuing the collaborative goal of standardizing and integrating trait data across organisms. We demonstrate how adherence to Open Science principles is key to the OTN community and outline five activities that can accelerate the synthesis of trait data across the Tree of Life, thereby facilitating rapid advances to address scientific inquiries and environmental issues. Lessons learned along the path to a global synthesis of trait data will provide a framework for addressing similarly complex data science and informatics challenges.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1989

The acoustics of a small-scale helicopter rotor in hover

A 2.1 m diameter, 1/6-scale model helicopter main rotor was tested in hover in the test section of the NASA Ames 40- by 80-foot wind tunnel. Performance and noise data on a small-scale rotor at various thrust coefficients and tip Mach numbers were obtained for comparison with existing data on similar full-scale helicopter rotors. These data form part of a data base to permit the estimation of scaling effects on various rotor noise mechanisms. Another objective was to contribute to a data base that will permit the estimation of facility effects on acoustic testing. Acoustic 1/3-octave-band spectra are presented, together with variations of overall acoustic levels with rotor performance, microphone distance, and directivity angle.

Kitaplioglu, Cahit↗
NASA NTRS2012

Does Ocean Color Data Assimilation Improve Estimates of Global Ocean Inorganic Carbon?

Ocean color data assimilation has been shown to dramatically improve chlorophyll abundances and distributions globally and regionally in the oceans. Chlorophyll is a proxy for phytoplankton biomass (which is explicitly defined in a model), and is related to the inorganic carbon cycle through the interactions of the organic carbon (particulate and dissolved) and through primary production where inorganic carbon is directly taken out of the system. Does ocean color data assimilation, whose effects on estimates of chlorophyll are demonstrable, trickle through the simulated ocean carbon system to produce improved estimates of inorganic carbon? Our emphasis here is dissolved inorganic carbon, pC02, and the air-sea flux. We use a sequential data assimilation method that assimilates chlorophyll directly and indirectly changes nutrient concentrations in a multi-variate approach. The results are decidedly mixed. Dissolved organic carbon estimates from the assimilation model are not meaningfully different from free-run, or unassimilated results, and comparisons with in situ data are similar. pC02 estimates are generally worse after data assimilation, with global estimates diverging 6.4% from in situ data, while free-run estimates are only 4.7% higher. Basin correlations are, however, slightly improved: r increase from 0.78 to 0.79, and slope closer to unity at 0.94 compared to 0.86. In contrast, air-sea flux of C02 is noticeably improved after data assimilation. Global differences decline from -0.635 mol/m2/y (stronger model sink from the atmosphere) to -0.202 mol/m2/y. Basin correlations are slightly improved from r=O.77 to r=0.78, with slope closer to unity (from 0.93 to 0.99). The Equatorial Atlantic appears as a slight sink in the free-run, but is correctly represented as a moderate source in the assimilation model. However, the assimilation model shows the Antarctic to be a source, rather than a modest sink and the North Indian basin is represented incorrectly as a sink rather than the source indicated by the free-run model and data estimates.

Gregg, Watson↗
NASA NTRS1981

Manual versus digital Landsat analysis for delineating river flooding

It has been found that flood boundary information derived from Landsat images, acquired at different flood stages, could be used to develop an empirical model for estimating the extent of flooding on the basis of in situ measurements of river discharge. An investigation was undertaken to determine whether improved results might have been obtained through digital image analysis or by including other Landsat spectral bands. The study area encompasses a highly flood-prone reach of the Black River in Lewis County, NY. It was found that visual analysis of aerial photographs and a Landsat band 7 image gave similar results. Visual and digital analysis of Landsat band 7 data gave similar results, and digital analysis of Landsat band 7 data gave results which were at least as good as digital analysis of combinations of spectral bands.

Philipson, W. R.↗
NASA NTRS1988

C IV and Si IV in IUE spectra of normal B8-A0 stars: UV identified Be/Ae stars

Archival IUE high dispersion spectra of 42 B6-A2 stars within 200 pc were surveyed. Five of the program stars show significant C IV and Si IV absorption. All of the stars with detected C IV have v sin i less than or = 190 km/sec. Sharp absorption cores are present in Si II lambda 1533 in 3 of the objects, indicating that these are previously unrecognized shell stars. Three of the stars have variable or asymmetric C IV profiles which are consistent with the C IV and Si IV being produced in stellar winds. One star has C IV in the form of a shortward-shifted discrete absorption component, similar to those observed in Be stars. The data are compared with similar data for Be and B shell stars.

Chiu, Weihsueh A.↗
NASA NTRS1992

Lateral spread of sonic boom measurements from US Air Force boomfile flight tests

A series of sonic boom flight tests were conducted by the US Air Force at Edwards AFB in 1987 with current supersonic DOD aircraft. These tests involved 43 flights by various aircraft at different Mach number and altitude combinations. The measured peak overpressures to predicted values as a function of lateral distance are compared. Some of the flights are combined into five groups because of the varying profiles and the limited number of sonic booms obtained during this study. The peak overpressures and the lateral distances are normalized with respect to the Carlson method predicted centerline overpressures and lateral cutoff distances, respectively, to facilitate comparisons between sonic boom data from similar flight profiles. It is demonstrated that the data agrees with sonic boom theory and previous studies and adds to the existing sonic boom database by including sonic boom signatures, tracking, and weather data in a digital format.

Downing, J. Micah↗
NASA NTRS2022

Science Autonomy for Ocean Worlds Astrobiology: A Perspective

Astrobiology missions to ocean worlds in our solar system must overcome both scientific and technological challenges due to extreme temperature and radiation conditions, long communication times, and limited bandwidth. While such tools could not replace ground-based analysis by science and engineering teams, machine learning algorithms could enhance the science return of these missions through development of autonomous science capabilities. Examples of science autonomy include onboard data analysis and subsequent instrument optimization, data prioritization (for transmission), and real-time decision-making based on data analysis. Similar advances could be made to develop streamlined data processing software for rapid ground-based analyses. Here we discuss several ways machine learning and autonomy could be used for astrobiology missions, including landing site selection, prioritization and targeting of samples, classification of “features” (e.g., proposed biosignatures) and novelties (uncharacterized, “new” features, which may be of most interest to agnostic astrobiological investigations), and data transmission.

ocean worlds↗
DOE OSTI2024

Characterization of SimulCam, a standoff Raman system for scientific support of SuperCam operations on Mars

During the development activities of SuperCam Calibration Target, target intended for one of the two first Raman instruments to be deployed on another planetary body, our group developed a laboratory instrument that could simulate to some extent the Raman capabilities of one of such instruments and could provide data with similar quality. The use of this kind of laboratory instruments has demonstrated its utility in the evaluation of potential calibration targets or anticipating the science outcome that an instrument could provide. The present work describes our laboratory setup to support SuperCam, evaluating similarities between both instruments, despite of differences in the hardware. Evaluation of data gathered by SuperCam on Mars and the availability of one replica of SuperCam’s Calibration Target allowed the comparison on the same set of targets, demonstrating how similar Signal-to-Noise Ratio (SNR) could be achieved from both instruments. The higher energy per pulse on SimulCam is compensated by a greater analytical footprint and the use of smaller collection optics. The results show how spectra obtained at representative distances of SuperCam are comparable. Operational principles are also comparable in terms of time resolution, and close in terms of spectral resolution. This similarity has allowed different science support works using SimulCam data, as well as the support to Mars detections using our setup. We provide examples of this support that will be shared with the community in different papers, as well as examples of possible operations activities that could benefit from experiments performed with SimulCam. We show how this setup can complement the two laboratory replicas in Los Alamos and Toulouse in providing support data to different experiments.

47 OTHER INSTRUMENTATION↗
NASA NTRS2012

Atmospheric Effects of Energetic Particle Precipitation in the Arctic Winter 1978-1979 Revisited

The Limb Infrared Monitor of the Stratosphere (LIMS) measured polar stratospheric enhancements of NO2 mixing ratios due to energetic particle precipitation (EPP) in the Arctic winter of 1978-1979. Recently reprocessed LIMS data are compared to more recent measurements from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) and the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) to place the LIMS measurements in the context of current observations. The amount of NOx (NO + NO2) entering the stratosphere that has been created by EPP in the mesosphere and lower thermosphere (EPP-NOx) has been quantified for the 1978-1979 and 2002-2003 through 2008-2009 Arctic winters. The NO2 enhancements in the LIMS data are similar to those in MIPAS and ACE-FTS data in the Arctic winters of 2002-2003, 2004-2005, 2006-2007, and 2007-2008. The largest enhancement by far is in 2003-2004 (approximately 2.2 Gmol at 1500 K), which is attributed to a combination of elevated EPP and unusual dynamics that led to strong descent in the upper stratosphere/lower mesosphere in late winter. The enhancements in 2005-2006 and 2008-2009, during which large stratospheric NOx enhancements were caused by a dynamical situation similar to that in 2003 2004, are larger than in all the other years (except 2003-2004) at 3000 K. However, by 2000 K the enhancements in 2005-2006 (2008-2009) are on the same order of magnitude as (smaller than) all other years. These results highlight the importance of the timing of the descent in determining the potential of EPP-NOx for reaching the middle stratosphere.

Holt, L. A.↗