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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Polysiloxane Scintillators for Efficient Neutron and Gamma-Ray Pulse Shape Discrimination

Plastic scintillators based on thermoplastics, such as polystyrene and poly(vinyl toluene) (PVT), are capable of neutron and γ radiation detection via pulse shape discrimination (PSD) when overdoped with select fluorescent molecules. This class of plastic scintillator has been extensively studied but is limited to applications suitable for thermoplastics. For applications requiring flexibility, scintillators composed of elastomers, such as polysiloxanes, offer an alternative to PVT scintillators. Polysiloxane scintillators are inherently flexible and have a short processing time on the order of 3 h in air and equivalent or better detection capability at reduced doping concentration (<5 wt %). This work presents polysiloxane-based scintillators, containing only 1–5 wt % of 2,5 diphenyl-oxazole (PPO) or 9,9-dimethyl-2-phenyl-9H-fluorene (PhF) as primary dopants and 9,9-dimethyl-2,7-distyryl-9H-fluorene (SFS) as a wavelength shifter. A 5 wt % PPO polysiloxane sample had improved neutron and gamma ray PSD and comparable light yield than EJ-299-33 tested under the same conditions, i.e., figure of merit (FoM) of 1.33 ± 0.03 at 450 keV ee and light yield of 94% relative to EJ-299-33. The 5 wt % PhF-polysiloxane sample had a higher light yield, 144% of EJ-299-33 but lower FoM under the same conditions (FoM of 1.09 ± 0.03). Furthermore, this work highlights the potential of polysiloxanes as a matrix for PSD capable plastic scintillators.

36 MATERIALS SCIENCE↗
NASA NTRS2018

Further Evaluation of Swept Wing Icing Scaling with Maximum Combined Cross Section Ice Shape Profiles

This study reports results from recent icing scaling tests conducted in the NASA Glenn Icing Research Tunnel (IRT) using recommended scaling methods that were developed for swept wing icing applications. The aluminum test articles used in this study were NACA 0012 Adjustable Sweep Airfoil Models. The reference and scale airfoils have a 36 inch and 15 inch chord measured normal to the leading edge, and a 60 inch and 24 inch span respectively. Reference tests were run with airspeeds of 100, 140.3 and 150 knot and MVD of 41.4, 44.4, 93 and 150 micron. All tests were set at 0⁰ angle of attack (AOA) and 30⁰ sweep angle. Results will be presented for stagnation freezing fractions ranging from 0.3 to 1.0. For non-dimensional reference & scale ice shape comparison, a new post-scanning ice shape digitization procedure was applied to extract 2-D "hand-tracing like" ice shape profiles, i.e. the Maximum Combined Cross Section or MCCS, at selected span-wise locations from the high fidelity 3-D scanned ice shapes obtained in the IRT. Preliminary assessment of ice shape comparison with MCCS showed that good scaling was achieved for the test conditions by using the recommended scaling methods developed for swept wing icing.

MCCS↗
DOE OSTI2024

Performance assessment of near-fault buildings subjected to physics-based simulated earthquake ground motions with fling step

The effects of the co-seismic static offset (known as fling step) and associated velocity pulses on civil structures have been difficult to study because the static offset is typically removed during the processing of earthquake ground motion records. Simulated ground motions contain fling features and require no processing; therefore, they create new opportunities for representing fling features in seismic hazard analysis and assessing their influence on the seismic demands on near-fault structures. We use physics-based fault rupture simulations to study the characteristics of ground motions with fling step and the sensitivity of the near-fault structural demands to strong fling features. We uncover that simulated ground motions with a large fling step tend to have higher spectral intensity than those without a fling step at the same rupture distance, especially at periods longer than 2 s. As a result, the structural demands on flexible buildings tend to be the most sensitive to the fling features. Statistical analysis suggests that the ground motion spectral shape (represented by spectral accelerations at multiple periods) is—in most cases—a sufficient predictor of the structural demands on near-fault low-rise and mid-rise buildings at locations that are susceptible to strong fling effects. Finally, ground motion record selection experiments reveal that representing the spectral shape features at periods that are most relevant to a given structure may be an effective strategy to reduce the bias in the estimated demands on near-fault long-period structures when the available database of records is considered deficient in fling features.

Fling step↗
DOE OSTI2025

Volatile traits expand the microbial playbook

Microbial metabolic functions are increasingly conceptualized as fitness-regulating traits. However, volatile compounds (the volatilome), despite their key roles in metabolism and ecology, are often overlooked in trait-based frameworks. We propose that volatile traits not only reflect ecological strategies but also shape them by mediating responses to selection pressures. Their volatility affects diffusion, substrate access, and interactions across space, conferring selective advantages as resources or waste products. We outline approaches to incorporate volatile traits into predictive models to improve understanding of microbial selection and community dynamics. Furthermore, this integration enables a more holistic view of microbial life by accounting for the ecological and evolutionary consequences of volatile-mediated processes.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

B/PS bulges in DESI Legacy edge-on galaxies – I. Sample building

ABSTRACT We present the biggest up-to-date sample of edge-on galaxies with boxy/peanut-shaped (B/PS) bulges and X-structures. The sample was prepared using images from the Dark Energy Spectroscopic Instrument (DESI) Legacy catalogue and contains about 2000 galaxies. To find suitable candidates in catalogue, we made the assumption that the residues (original images minus model) of galaxies with B/PS bulges should exhibit a characteristic X-shape. Galaxies with such features were selected by eye and then used as input data for a neural network training, which was applied to a bigger sample of edge-on galaxies. Using the available data and the photometric models from the literature, we investigated the observational and statistical properties of the sample created. Comparing the B/D ratios for galaxies with and without B/PS bulges, we found that the B/D ratio for galaxies from our sample is statistically higher, with typical values in the range ≈0.2–0.5 depending on the decomposition procedure. We studied how the opening angles φ of the X-structure and the length of its rays are distributed in the formed sample and found them to be consistent with previous measurements and predictions from N-body models, e.g. $\varphi \gtrsim 25{^\circ }$, but measured here for a much larger number of galaxies. We found a sharp increase in the B/PS bulge fraction for stellar masses log M⋆ ≳ 10.4, but for edge-on galaxies, which complements the results of previous works. The sample can be used in future work to test various bar models and their relationship with B/PS bulges, as well as to study their stability and evolution.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Hyper Suprime-Cam Year 3 results: Cosmology from galaxy clustering and weak lensing with HSC and SDSS using the minimal bias model

Here, we present cosmological parameter constraints from a blind joint analysis of three two-point correlation functions measured from the Year 3 Hyper Suprime-Cam (HSC-Y3) imaging data, covering about 416 deg 2 , and the SDSS DR11 spectroscopic galaxies spanning the redshift range [0.15, 0.70]. We subdivide the SDSS galaxies into three luminosity-cut, and therefore nearly volume-limited samples separated in redshift, each of which acts as a large-scale structure tracer characterized by the measurement of the projected correlation function, w p ⁡(R). We also use the measurements of the galaxy-galaxy weak-lensing signal Δ⁢Σ⁡(R) for each of these SDSS samples which act as lenses for a secure sample of source galaxies selected from the HSC-Y3 shape catalog based on their photometric redshifts. We combine these measurements with the cosmic shear correlation functions, ξ ± ⁡($\vartheta$) measured for our HSC source sample. We model these observables with the minimal bias model of the galaxy clustering observables in the context of a flat Λ⁢CDM cosmology. We use conservative scale cuts, R >12 and 8⁢ℎ -1 Mpc for Δ⁢Σ and w p , respectively, where the minimal bias model is valid, in addition to conservative prior on the residual bias in the mean redshift of the HSC photometric source galaxies. We present various validation tests of our model as well as analysis methods. Our baseline analysis yields S 8 = $0.77⁢5^{+0.043}_{-0.038}$ (68% C.I.) for the Λ⁢CDM model, after marginalizing over uncertainties in other parameters. Our value of S 8 is consistent with that from the Planck 2018 data, but the credible interval of our result is still relatively large. We show that various internal consistency tests based on different splits of the data are passed. Our results are statistically consistent with those of a companion paper, which extends this analysis to smaller scales with an emulator-based halo model, using Δ⁢Σ⁡(R) and w p ⁡(R) down to R >3 and 2⁢ℎ -1 Mpc, respectively.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1972

Analytical correlation of centrifugal compressor design geometry for maximum efficiency with specific speed

Centrifugal compressor performance was examined analytically to determine optimum geometry for various applications as characterized by specific speed. Seven specific losses were calculated for various combinations of inlet tip-exit diameter ratio, inlet hub-tip diameter ratio, blade exit backsweep, and inlet-tip absolute tangential velocity for solid body prewhirl. The losses considered were inlet guide vane loss, blade loading loss, skin friction loss, recirculation loss, disk friction loss, vaneless diffuser loss, and vaned diffuser loss. Maximum total efficiencies ranged from 0.497 to 0.868 for a specific speed range of 0.257 to 1.346. Curves of rotor exit absolute flow angle, inlet tip-exit diameter ratio, inlet hub-tip diameter ratio, head coefficient and blade exit backsweep are presented over a range of specific speeds for various inducer tip speeds to permit rapid selection of optimum compressor size and shape for a variety of applications.

Galvas, M. R.↗
NASA NTRS1977

Acoustic energy shaping

A suspended mass is shaped by melting all or a selected portion of the mass and applying acoustic energy in varying amounts to different portions of the mass. In one technique for forming an optical waveguide slug, a mass of oval section is suspended and only a portion along the middle of the cross-section is heated to a largely fluid consistency. Acoustic energy is applied to opposite edges of the oval mass to press the unheated opposite edge portions together so as to form bulges at the middle of the mass. In another technique for forming a ribbon of silicon for constructing solar cells, a cylindrical thread of silicon is drawn from a molten mass of silicon, and acoustic energy is applied to opposite sides of the molten thread to flatten it into a ribbon.

Wang, T. G.↗
NASA NTRS1980

Computations of the Magnus effect for slender bodies in supersonic flow

A recently reported Parabolized Navier-Stokes code has been employed to compute the supersonic flow field about spinning cone, ogive-cylinder, and boattailed bodies of revolution at moderate incidence. The computations were performed for flow conditions where extensive measurements for wall pressure, boundary layer velocity profiles and Magnus force had been obtained. Comparisons between the computational results and experiment indicate excellent agreement for angles of attack up to six degrees. The comparisons for Magnus effects show that the code accurately predicts the effects of body shape and Mach number for the selected models for Mach numbers in the range of 2-4.

Sturek, W. B.↗
NASA NTRS1983

An overview of two nonlinear supersonic wing design studies

The progress of two studies which apply nonlinear aerodynamics to supersonic wing design is reviewed. The first study employed a nonlinear potential flow code to design wings for high lift and low drag due to lift by employing a controlled leading-edge expansion in which the crossflow accelerates to supercritical conditions and decelerates through a weak shock. The second study utilized a modified linearized theory code to explore the concept of using 'attainable' leading-edge thrust as a guide for selecting a wing leading-edge shape (planform and radius) for maintaining attached flow and maximizing leading-edge thrust. Experimental and theoretical results obtained during the course of these two studies are discussed.

Miller, D. S.↗
NASA NTRS1985

Design and evaluation of control systems for large communications satellites

Control techniques for future large flexible spacecraft are developed. Control design and analysis are supported by a comprehensive CAD system. The proposed operational mobile communications satellite (OMSAT) featuring a 44 m offset fed antenna is used as target application. Requirements for satellite attitude control and communications beam pointing are defined. The following control methods are applied to the system: standard linear optimal regulator (LOR) with Luenberger observer, LOR/observer with selective spill-over suppression, frequency shaped LOR, LOR with closed-loop order reduction by cost decoupling, and robust servomechanism.

Steiber, M. E.↗
NASA NTRS1990

Segmentation, modeling and classification of the compact objects in a pile

The problem of interpreting dense range images obtained from the scene of a heap of man-made objects is discussed. A range image interpretation system consisting of segmentation, modeling, verification, and classification procedures is described. First, the range image is segmented into regions and reasoning is done about the physical support of these regions. Second, for each region several possible three-dimensional interpretations are made based on various scenarios of the objects physical support. Finally each interpretation is tested against the data for its consistency. The superquadric model is selected as the three-dimensional shape descriptor, plus tapering deformations along the major axis. Experimental results obtained from some complex range images of mail pieces are reported to demonstrate the soundness and the robustness of our approach.

Gupta, Alok↗
NASA NTRS1999

Retrieval of Mir Solar Array

A Russian solar array panel removed in November 1997 from the non-articulating photovoltaic array on the Mir core module was returned to Earth on STS-89 in January 1998. The panel had been exposed to low Earth orbit (LEO) for 10 years prior to retrieval. The retrieval provided a unique opportunity to study the effects of the LEO environment on a functional solar array. To take advantage of this opportunity, a team composed of members from RSC-Energia (Russia), the Boeing Company, and the following NASA Centers--Johnson Space Center, Kennedy Space Center, Langley Research Center, Marshall Space Flight Center, and Lewis Research Center--was put together to analyze the array. After post-retrieval inspections at the Spacehab Facility at Kennedy in Florida, the array was shipped to Lewis in Cleveland for electrical performance tests, closeup photodocumentation, and removal of selected solar cells and blanket material. With approval from RSC-Energia, five cell pairs and their accompanying blanket and mesh material, and samples of painted handrail materials were selected for removal on the basis of their ability to provide degradation information. Sites were selected that provided different sizes and shapes of micrometeoroid impacts and different levels of surface contamination. These materials were then distributed among the team for round robin testing.

Rutledge, Sharon K.↗
NASA NTRS2017

External Acoustic Liners for Multi-Functional Aircraft Noise Reduction

Acoustic liners for aircraft noise reduction include one or more chambers that are configured to provide a pressure-release surface such that the engine noise generation process is inhibited and/or absorb sound by converting the sound into heat energy. The size and shape of the chambers can be selected to inhibit the noise generation process and/or absorb sound at selected frequencies.

Jones, Michael G.↗
NASA NTRSDate not supplied

TPSAS-NF1676L-27111-DND

Rigid aeroshell systems are rapidly approaching the payload limit that current technology can deliver while fitting within the payload envelope of existing launch vehicles. The need for higher entry mass, landing elevation, and more controllability has pushed NASA to improve existing atmospheric entry technologies to further its scientific and exploration capabilities. Hypersonic Inflatable Aerodynamic Decelerators (HIADs) are an emerging technology that allows entry vehicles to deliver larger payloads to higher landing elevations by providing a larger aeroshell diameter than rigid aeroshells. HIADs offer new methods of entry vehicle trajectory control through shape morphing of the inflatable aeroshell. This dissertation explores different concepts of morphing a HIAD by assessing its structural integrity, aerodynamic performance, and systems integration. Analytical models are developed to predict the amount of force required to achieve a desired morphed shape, an actuator and sensor are selected based on performance requirements, and a controller is designed to morph the HIAD through Lift-to-Drag modulation. The actuator and sensor system and controller are then integrated into a small-scale development unit of a HIAD and experimental results are compared to numerical simulations. Conclusions and contributions of this research are presented along with a discussion on further research opportunities of Morphing HIADs.

Adam Milne Slagle↗
NASA NTRS2022

The Spectral-Timing Analysis of Cygnus X-1 With Insight-HXMT

Cygnus X-1, as the first discovered black hole binary, is a key source for understanding the mechanisms of state transitions, and the scenarios of accretion in extreme gravity fields. We present a spectral-timing analysis of observations taken with the Insight-HXMT mission, focusing on the spectral-state dependent timing properties in the broad energy range of 1–150 keV, thus extending previous RXTE-based studies to both lower and higher energies. Our main results are the following: a) We successfully use a simple empirical model to fit all spectra, confirming that the reflection component is stronger in the soft state than in the hard state; b) The evolution of the total fractional root mean square (rms) depends on the selected energy band and the spectral shape, which is a direct result of the evolution of the power spectral densities (PSDs); c) In the hard/intermediate state, we see clear short-term variability features and a positive correlation between central frequencies of the variability components and the soft photon index Γ(sub 1), also at energies above 15 keV. The power spectrum is dominated by red noise in the soft state instead. These behaviors can be traced to at least 90 keV; d) The coherence and the phase-lag spectra show different behaviors dependent on different spectral shapes.

Binary X-rays↗
NASA NTRSDate not supplied

Joining and Integration of Silicon Carbide-Based Ceramic Materials for Aerospace Applications: An Overview

In order to fully utilize silicon carbide-based ceramics and ceramic matrix composites (CMCs) for aerospace and ground based applications, advanced joining and integration technologies are critically needed for achieving large, complex shaped, and integrated components. Careful material selection of joining inter-layers needs to consider chemical and thermal compatibilities with the parent materials that are being joined. Also, optimization needs to be conducted to select the proper processing conditions for achieving robust joints that are well adhered, strong, uniform, crack free, and have minimal residual stresses. NASA GRC developed pressureless and pressure aided approaches for joining ceramics and CMCs include brazing, diffusion bonding, refractory eutectic phase joining, and Single-step Elevated Temperature (SET) Joining. For joining ceramics and CMCs to metals, several brazes have been utilized. Brazing approaches for joining ceramics and metals have also included tailored brazes with multiple interlayers and particle additions. An overview of the joining approaches will be provided. In addition, processing-microstructure-property relationships will be discussed.

Silicon carbide↗