SEARCH · Search NASA

Results for “elemental profiling”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11

All sources NASA NTRS DOE OSTI

NASA NTRS1979

Evaluation and auger analysis of a zinc-dialkyl-dithiophosphate antiwear additive in several diester lubricants

The wear of pure iron in sliding contact with hardened M-2 tool steel was measured for a series of synthetic diester fluids, both with and without a zinc dialkyl dithiophosphate (ZDP) antiwear additive, as test lubricants. Selected wear scars were analyzed by an Auger emission spectroscopy (AES) depth profiling technique in order to assess the surface film elemental composition. The ZDP was an effective antiwear additive for all the diesters except dibutyl oxalate and dibutyl sebacate. The high wear measured for the additive-containing oxalate was related to corrosion; the higher wear measured for the additive-containing sebacate was due to an oxygen interaction. The AES of dibutyl sebacate surfaces run in dry air and in dry nitrogen showed large differences only in the amount of oxygen present. The AES of worn surfaces where the additive was effective showed no zinc, only a little phosphorus, and large amounts of sulfur.

Brainard, W. A.↗

NASA NTRS1993

Small hydrogen/oxygen rocket flowfield behavior from heat flux measurements

The mixing and heat transfer phenomena in small rocket flow fields with fuel film cooling is not well understood. An instrumented, water-cooled chamber with a gaseous hydrogen/gaseous oxygen injector was used to gather steady-state inner and outer wall temperature profiles. The chamber was tested at 414 kPa (60 psia) chamber pressure, from mixture ratios of 3.41 to 8.36. Sixty percent of the fuel was used for film cooling. These temperature profiles were used as boundary conditions in a finite element analysis program, MSC/NASTRAN, to calculate the local radial and axial heat fluxes in the chamber wall. The normal heat fluxes were then calculated and used as a diagnostic of the rocket's flow field behavior. The normal heat fluxes determined were on the order of 1.0 to 3.0 MW/meters squared (0.6 to 1.8 Btu/sec-inches squared). In the cases where mixture ratio was 5 or above, there was a sharp local heat flux maximum in the barrel section of the chamber. This local maximum seems to indicate a reduction or breakdown of the fuel film cooling layer, possibly due to increased mixing in the shear layer between the film and core flows. However, the flow was thought to be completely laminar, as the throat Reynolds numbers were below 50,000 for all the cases. The increased mixing in the shear layer in the higher mixture ratio cases appeared not to be due to the transition of the flow from laminar to turbulent, but rather due to increased reactions between the hydrogen film and oxidizer-rich core flows.

Reed, Brian D.↗

NASA NTRS2010

Human Spaceflight Trajectory Operations: A Case Study from STS-132/ULF4

Prior to the launch of the STS-132/ULF4 mission, the International Space Station (ISS) Flight Control Team was alerted to the approach of a space debris with a predicted time of closest approach approximately 1 hr after Space Shuttle docking. As a result, the ISS team considered performing a collision avoidance maneuver prior to the Space Shuttle s approach. The purpose of this presentation will be to use this case study to illustrate best practices of the human spaceflight trajectory operations team. The presentation will begin with an overview of the roles of the real-time ISS and Space Shuttle trajectory flight control teams. Then, the STS-132/ULF4 case study will be used to illustrate the issues and lessons learned involved in performing Space Shuttle rendezvous maneuver planning and execution. Specific elements of the STS-132 Space Shuttle rendezvous maneuver profile that can be used to provide mission assurance in cases of trajectory uncertainty will be described and discussed. Additionally, this case study will be used to provide context for identifying lessons learned in an operational environment that requires technical and decision-making coordination between two control center teams with two potentially maneuvering space vehicles.

Cutri-Kohart, Rebecca↗

NASA NTRS2010

Multipoint Geospace Science in 3D: The Paired Ionosphere-Thermosphere Orbiters(PITO) Mission

The science enabled by the Paired Ionosphere-Thermosphere Orbiters (PITO) mission is described and discussed. PITO has been designed to provide the concurrent, three-dimensional, multipoint measurements needed to advance geospace science while staying within a stringent resource envelope. The mission utilizes a pair of orbiting vehicles in eccentric, high-inclination, coplanar orbits. The orbits have arguments of perigee that differ by 180 degrees and are phased such that one vehicle is at perigee (~200 km) while the second is at apogee (~2000 km). Half an orbit later, the vehicles switch positions. Three complementary types of measurements exploit this scenario: local, in-situ measurements on both satellites, two-dimensional imaging from the higher satellite, and vertical sounders. The main idea is that two-dimensional context information for the low-altitude measurements is obtained by the high altitude imagers, while information on the third dimension is provided by vertical profiling. Such an observation system is capable of providing elements of global coverage, regional coverage, and concurrent coverage in three dimensions. Science goals are presented, as are the results of a detailed implementation plan, including several trade studies on key elements of the mission. The conclusion is that the mission would enable significant new understanding of the ionosphere-thermosphere system within a resource envelope that is consistent with that of NASA's Medium Explorer (MIDEX) line of science missions.

Clemmons, J.↗

NASA NTRS2016

Predictive Lateral Logic for Numerical Entry Guidance Algorithms

Recent entry guidance algorithm development123 has tended to focus on numerical integration of trajectories onboard in order to evaluate candidate bank profiles. Such methods enjoy benefits such as flexibility to varying mission profiles and improved robustness to large dispersions. A common element across many of these modern entry guidance algorithms is a reliance upon the concept of Apollo heritage lateral error (or azimuth error) deadbands in which the number of bank reversals to be performed is non-deterministic. This paper presents a closed-loop bank reversal method that operates with a fixed number of bank reversals defined prior to flight. However, this number of bank reversals can be modified at any point, including in flight, based on contingencies such as fuel leaks where propellant usage must be minimized.

Smith, Kelly M.↗

NASA NTRS2022

Analysis of Eight Magnetic Chemically Peculiar Stars With Rotational Modulation

Since the end of 2018, the Transiting Exoplanet Survey Satellite (TESS) has provided stellar photometry to the astronomical community. We have used TESS data to study rotational modulation in the light curves of a sample of chemically peculiar stars with measured large-scale magnetic fields (mCP stars). In general, mCP stars show inhomogeneous distributions of elements in their atmospheres that lead to spectroscopic (line profile) and photometric (light curve) variations commensurate with the rotational period. We analyzed the available TESS data from 50 sectors for eight targets after post-processing them in order to minimize systematic instrumental trends. Analysis of the light curves allowed us to determine rotational periods for all eight of our targets. For each star, we provide a phase diagram calculated using the derived period from the light curves and from the available measurements of the disc-averaged longitudinal magnetic field B(sub z). In most cases, the phased light curve and B(sub z) measurements show consistent variability. Using our rotation periods, and global stellar parameters derived from fitting Balmer line profiles, and from Geneva and Strömgren–Crawford photometry, we determined the equatorial rotational velocities and calculated the respective critical rotational fractions v(sub eq)/v(crit). We have shown from our sample that the critical rotational fraction decreases with stellar age, at a rate consistent with the magnetic braking observed in the larger population of mCP stars.

Chemically peculiar stars↗

NASA NTRS2017

Precision Pointing for the Wide-Field Infrared Survey Telescope (WFIRST)

The Wide-Field Infrared Survey Telescope (WFIRST) mission, scheduled for a mid-2020's launch, is currently in its definition phase. The mission is designed to investigate essential questions in the areas of dark energy, exoplanets, and infrared astrophysics. WFIRST will use a 2.4-meter primary telescope (same size as the Hubble Space Telescope's primary mirror) and two instruments: the Wide Field Instrument (WFI) and the Coronagraph Instrument (CGI). In order to ad-dress the critical science requirements, the WFIRST mission will conduct large-scale surveys of the infrared sky, requiring both agility and precision pointing (11.6 milli-arcsec stability, 14 milli-arcsec jitter). This paper describes some of the challenges this mission profile presents to the GNC subsystem, and some of the design elements chosen to accommodate those challenges. The high-galactic-latitude survey is characterized by 3-minute observations separated by slews ranging from 0.025 deg to 0.8 deg. The need for observation efficiency drives the slew and settle process to be as rapid as possible. A description of the shaped slew profile chosen to minimize excitation of structural oscillation, and the handoff from star tracker-gyro control to fine guidance sensor control is detailed. Also presented is the fine guidance sensor (FGS), which is integral with the primary instrument (WFI). The FGS is capable of tracking up to 18 guide stars, enabling robust FGS acquisition and precision pointing. To avoid excitation of observatory structural jitter, reaction wheel speeds are operationally maintained within set limits. In addition, the wheel balance law is designed to maintain 1-Hz separation between the wheel speeds to avoid reinforcing jitter excitation at any particular frequency. The wheel balance law and operational implications are described. Finally, the candidate GNC hardware suite needed to meet the requirements of the mission is presented.

Stoneking, Eric↗

DOE OSTI2026

HLW Melter Refractory Thermal Finite Element Analysis using ANSYS

The objective of this calculation is to provide thermal profiles, heat dissipation and refractory thermal expansion results from changes to inputs/assumptions related to optimization of margins and conservatisms (described in Section 3).

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

NASA NTRS2017

Transition Induced by a Streamwise Array of Roughness Elements on a Supersonic Flat Plate

Roughness is unavoidable on practical high-speed vehicles, so it is critical to determine its impact on boundary layer transition. The flow field downstream of a streamwise array of cylindrical roughness elements is probed with hot-wire anemometry in this experiment. Mean flow distortion is examined in several measurement planes in the wake of the cylindrical roughness using the streak strength profiles and contour plots of the mass flux and total temperature. The roughness element heights and spacings were varied and their instability modes were examined. Cylindrical roughness elements approximately 140 micron tall produce an odd instability mode that grows weakly with downstream distance in the measurement range of this experiment. Cylindrical roughness elements approximately 280 micron tall produce an even instability mode that grows, becomes nonlinear, and then breaks down. Transition onset remains constant relative to the most downstream roughness in the streamwise array when the 280 micron roughness elements are spaced 2 diameters apart. Transition onset occurs at an earlier upstream location relative to the most downstream roughness in the streamwise array when the roughness elements are spaced 4 diameters appear to recover before the next downstream roughness element, so the location of transition shifts with the location of the most downstream roughness element in the array. When the rough- apart. The wake behind roughness elements spaced 2 diameters apart do not ness elements are spaced 4 diameters apart, the flow behind the first roughness element has enough space to recover before feeding into the second roughness element, and thus, moves transition forward.

Chou, Amanda↗

DOE OSTI2026

Effects of interstitial oxygen on ω transformations and twin formation in bcc NbTaTiHf multi-principal element alloy from first-principles

Transformation- and twinning-induced plasticity (TRIP and TWIP) have been reported to contribute to the low-temperature deformation of some body-centered cubic (bcc) multi-principal element alloys (MPEAs) containing large fractions of group IV transition metals. The influence of interstitial solutes on the mechanisms underlying these forms of plasticity, however, remains unclear. Using first-principles calculations, we study the effects of interstitial O atoms on the relative stability of bcc and ω phases and on unstable and twin boundary stacking fault energy profiles in a representative bcc MPEA with high group-IV elemental fraction: NbTaTiHf. We find that O additions generally promote the relaxation of ω configurations back to their parent bcc structure, therefore inhibiting ω transformation. Calculations of the Rice parameter for bulk bcc and phases, as well as bcc-ω interfaces, further show that ω formation is a potent embrittlement factor, an effect that is enhanced by O additions, suggesting that the formation of bcc-ω interfaces is energetically preferred over the formation of the bulk ω phase. By contrast, the Rice parameter for twin boundaries indicates that these interfaces do not embrittle the material, even with O atoms at twin boundaries, providing a more favorable pathway for plastic deformation compared to ω transformation.

Density functional theory↗

NASA NTRS1989

Ionization and thermal equilibrium models for O star winds based on time-independent radiation-driven wind theory

Ab initio ionization and thermal equilibrium models are calculated for the winds of O stars using the results of steady state radiation-driven wind theory to determine the input parameters. Self-consistent methods are used for the roles of H, He, and the most abundant heavy elements in both the statistical and the thermal equilibrium. The model grid was chosen to encompass all O spectral subtypes and the full range of luminosity classes. Results of earlier modeling of O star winds by Klein and Castor (1978) are reproduced and used to motivate improvements in the treatment of the hydrogen equilibrium. The wind temperature profile is revealed to be sensitive to gross changes in the heavy element abundances, but insensitive to other factors considered such as the mass-loss rate and velocity law. The reduced wind temperatures obtained in observing the luminosity dependence of the Si IV lambda 1397 wind absorption profile are shown to eliminate any prospect of explaining the observed O VI lambda 1036 line profiles in terms of time-independent radiation-driven wind theory.

Drew, J. E.↗

NASA NTRS2010

Sensing device with whisker elements

A sensing device includes an elongated whisker element having a flexible cantilever region and a base region where a change in moment or curvature is generated by bending of the cantilever region when it contacts an object. One or more sensor elements cooperatively associated with the whisker element provide one or more output signals that is/are representative of two orthogonal components of change in moment or curvature at the whisker base region to permit determination of object distance, fluid velocity profile, or object contour (shape) with accounting for lateral slip of the whisker element and frictional characteristics of the object. Multiple sensing devices can be arranged in arrays in a manner to sense object contour without or with adjustment for lateral slip.

Hartmann, Mitra J.↗

NASA NTRS2013

Sensing Device with Whisker Elements

Hartmann, Mitra J.↗

DOE OSTI2024

A cell type-aware framework for nominating non-coding variants in Mendelian regulatory disorders

Abstract Unsolved Mendelian cases often lack obvious pathogenic coding variants, suggesting potential non-coding etiologies. Here, we present a single cell multi-omic framework integrating embryonic mouse chromatin accessibility, histone modification, and gene expression assays to discover cranial motor neuron (cMN)cis-regulatory elements and subsequently nominate candidate non-coding variants in the congenital cranial dysinnervation disorders (CCDDs), a set of Mendelian disorders altering cMN development. We generate single cell epigenomic profiles for ~86,000 cMNs and related cell types, identifying ~250,000 accessible regulatory elements with cognate gene predictions for ~145,000 putative enhancers. We evaluate enhancer activity for 59 elements using an in vivo transgenic assay and validate 44 (75%), demonstrating that single cell accessibility can be a strong predictor of enhancer activity. Applying our cMN atlas to 899 whole genome sequences from 270 genetically unsolved CCDD pedigrees, we achieve significant reduction in our variant search space and nominate candidate variants predicted to regulate known CCDD disease genesMAFB, PHOX2A, CHN1, andEBF3– as well as candidates in recurrently mutated enhancers through peak- and gene-centric allelic aggregation. This work delivers non-coding variant discoveries of relevance to CCDDs and a generalizable framework for nominating non-coding variants of potentially high functional impact in other Mendelian disorders.

Science & Technology - Other Topics↗

DOE OSTI2025

Finite element analysis of the impact of beam heating mode in molten salt corrosion experiments employing simultaneous ion irradiation

Finite element analysis was used to investigate the temperature and stress profiles that develop in 316L stainless steel membranes being irradiated using different proton beam conditions in contact with a molten salt environment. It was shown that in addition to a nonuniform irradiation profile, a focused 2 MeV proton beam leads to very strong temperature and stress gradients in the membrane, introducing highly localized driving forces that complicate and even compromise the integrity and reliability of the experimental results of corrosion studies. Here, the use of a focused beam in corrosion studies can create experimental artifacts that may misrepresent the true corrosion behavior. In contrast, the use of a rastered beam is shown to distribute the protons and resulting radiation damage uniformly across the membrane face, and more importantly, results in temperature and stress profiles that are not only very uniform but are of much lower magnitude. The use of a rastered beam during molten salt corrosion experiments is therefore recommended to achieve uniform damage rates, thereby reducing both gradients and magnitudes of the temperature and stress distributions.

43 - PARTICLE ACCELERATORS↗

NASA NTRS1995

Elemental and charge state composition of the fast solar wind observed with SMS instruments on WIND

The elemental composition and charge state distributions of heavy ions of the solar wind provide essential information about: (1) atom-ion separation processes in the solar atmosphere leading to the 'FIP effect' (the overabundance of low First Ionization potential (FIP) elements in the solar wind compared to the photosphere); and (2) coronal temperature profiles, as well as mechanisms which heat the corona and accelerate the solar wind. This information is required for solar wind acceleration models. The SWICS instrument on Ulysses measures for all solar wind flow conditions the relative abundance of about 8 elements and 20 charge states of the solar wind. Furthermore, the Ulysses high-latitude orbit provides an unprecedented look at the solar wind from the polar coronal holes near solar minimum conditions. The MASS instrument on the WIND spacecraft is a high-mass resolution solar wind ion mass spectrometer that will provide routinely not only the abundances and charge state of all elements easily measured with SWICS, but also of N, Mg, S. The MASS sensor was fully operational at the end of 1994 and has sampled the in-ecliptic solar wind composition in both the slow and the corotating fast streams. This unique combination of SWICS on Ulysses and MASS on WIND allows us to view for the first time the solar wind from two regions of the large coronal hole. Observations with SWICS in the coronal hole wind: (1) indicate that the FIP effect is small; and (2) allow us determine the altitude of the maximum in the electron temperature profile, and indicate a maximum temperature of approximately 1.5 MK. New results from the SMS instruments on Wind will be compared with results from SWICS on Ulysses.

Gloeckler, G.↗

NASA NTRS1997

Prediction of High-Lift Flows using Turbulent Closure Models

The flow over two different multi-element airfoil configurations is computed using linear eddy viscosity turbulence models and a nonlinear explicit algebraic stress model. A subset of recently-measured transition locations using hot film on a McDonnell Douglas configuration is presented, and the effect of transition location on the computed solutions is explored. Deficiencies in wake profile computations are found to be attributable in large part to poor boundary layer prediction on the generating element, and not necessarily inadequate turbulence modeling in the wake. Using measured transition locations for the main element improves the prediction of its boundary layer thickness, skin friction, and wake profile shape. However, using measured transition locations on the slat still yields poor slat wake predictions. The computation of the slat flow field represents a key roadblock to successful predictions of multi-element flows. In general, the nonlinear explicit algebraic stress turbulence model gives very similar results to the linear eddy viscosity models.

Rumsey, Christopher L.↗

NASA NTRS1985

Dynamic models of flux tubes in the interpretation of polarization measurements

Recent observations of Stokes parameter profiles indicate the presence of mass motions with large velocity gradients associated with small-scale magnetic elements. Dynamic models of flux tubes were used in order to interpret observations of unresolved elements. It is clear that the physical picture of the dynamic models will be quite different from the hydrostatic ones since there is a strong coupling between the magnetic and the velocity field. Polarization measurements have to be interpreted in terms of dynamic models. Two-D steady flow solutions in slender magnetic tubes have been worked out. It was found that the main properties of the intensity line profiles as well as the asymmetries of the V Stokes profiles can be explained best in terms of magnetic elements with moderate field strength.

Ribes-Nesme, E.↗