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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

The impact of CFD on development test facilities - A National Research Council projection

The results of a National Research Council study on the effect that advances in computational fluid dynamics (CFD) will have on conventional aeronautical ground testing are reported. Current CFD capabilities include the depiction of linearized inviscid flows and a boundary layer, initial use of Euler coordinates using supercomputers to automatically generate a grid, research and development on Reynolds-averaged Navier-Stokes (N-S) equations, and preliminary research on solutions to the full N-S equations. Improvements in the range of CFD usage is dependent on the development of more powerful supercomputers, exceeding even the projected abilities of the NASA Numerical Aerodynamic Simulator (1 BFLOP/sec). Full representation of the Re-averaged N-S equations will require over one million grid points, a computing level predicted to be available in 15 yr. Present capabilities allow identification of data anomalies, confirmation of data accuracy, and adequateness of model design in wind tunnel trials. Account can be taken of the wall effects and the Re in any flight regime during simulation. CFD can actually be more accurate than instrumented tests, since all points in a flow can be modeled with CFD, while they cannot all be monitored with instrumentation in a wind tunnel.

Korkegi, R. H.↗
DOE OSTI2024

Stress-hybrid virtual element method on six-noded triangular meshes for compressible and nearly-incompressible linear elasticity

In this paper, we present a first-order Stress-Hybrid Virtual Element Method (SH-VEM) on six-noded triangular meshes for linear plane elasticity. Here, we adopt the Hellinger–Reissner variational principle to construct a weak equilibrium condition and a stress based projection operator. In each element, the stress projection operator is expressed in terms of the nodal displacements, which leads to a displacement based formulation. This stress-hybrid approach assumes a globally continuous displacement field while the stress field is discontinuous across each element. The stress field is initially represented by divergence-free tensor polynomials based on Airy stress functions, but we also present a formulation that uses a penalty term to enforce the element equilibrium conditions, referred to as the Penalty Stress-Hybrid Virtual Element Method (PSH-VEM). Numerical results are presented for PSH-VEM and SH-VEM, and we compare their convergence to the composite triangle FEM and B-bar VEM on benchmark problems in linear elasticity. The SH-VEM converges optimally in the L 2 norm of the displacement, energy seminorm, and the L 2 norm of hydrostatic stress. Furthermore, the results reveal that PSH-VEM converges in most cases at a faster rate than the expected optimal rate, but it requires the selection of a suitably chosen penalty parameter.

42 ENGINEERING↗
NASA NTRS1995

Effects of target fragmentation on evaluation of LET spectra from space radiation in low-earth orbit (LEO) environment: impact on SEU predictions

Recent improvements in the radiation transport code HZETRN/BRYNTRN and galactic cosmic ray environmental model have provided an opportunity to investigate the effects of target fragmentation on estimates of single event upset (SEU) rates for spacecraft memory devices. Since target fragments are mostly of very low energy, an SEU prediction model has been derived in terms of particle energy rather than linear energy transfer (LET) to account for nonlinear relationship between range and energy. Predictions are made for SEU rates observed on two Shuttle flights, each at low and high inclination orbit. Corrections due to track structure effects are made for both high energy ions with track structure larger than device sensitive volume and for low energy ions with dense track where charge recombination is important. Results indicate contributions from target fragments are relatively important at large shield depths (or any thick structure material) and at low inclination orbit. Consequently, a more consistent set of predictions for upset rates observed in these two flights is reached when compared to an earlier analysis with CREME model. It is also observed that the errors produced by assuming linear relationship in range and energy in the earlier analysis have fortuitously canceled out the errors for not considering target fragmentation and track structure effects.

STS-51 Shuttle Project↗
DOE OSTI2022

Large-Scale Optimization with Linear Equality Constraints Using Reduced Compact Representation

For optimization problems with linear equality constraints, we prove that the (1,1) block of the inverse KKT matrix remains unchanged when projected onto the nullspace of the constraint matrix. In this work, we develop reduced compact representations of the limited-memory inverse BFGS Hessian to compute search directions efficiently when the constraint Jacobian is sparse. Orthogonal projections are implemented by a sparse QR factorization or a preconditioned LSQR iteration. In numerical experiments two proposed trust-region algorithms improve in computation times, often significantly, compared to previous implementations of related algorithms and compared to IPOPT.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1989

A graphics package for meteorological data, version 1.5

A plotting package has been developed to simplify the task of plotting meteorological data. The calling sequences and examples of high level yet flexible routines which allow contouring, vectors and shading of cylindrical, polar, orthographic and Mollweide (egg) projections are given. Routines are also included for contouring pressure-latitude and pressure-longitude fields with linear or log scales in pressure (interpolation to fixed grid interval is done automatically). Also included is a fairly general line plotting routine. The present version (1.5) produces plots on WMS laser printers and uses graphics primitives from WOLFPLOT.

Moorthi, Shrinivas↗
NASA NTRS1992

Summary of the NASA Lewis component technology program for Stirling power converters

An update is presented on the NASA Lewis Stirling component technology program. The component technology program has been organized as part of the NASA Lewis effort to develop Stirling converter technology for space power applications. The Stirling space power project is part of the High Capacity Power element of the NASA Civil Space Technology Initiative (CSTI). Lewis is also providing technical management of a DOE funded project to develop Stirling converter systems for distributed dish solar terrestrial power applications. The primary contractors for the space power and solar terrestrial projects develop component technologies directly related to their project goals. This Lewis component technology program, while coordinated with these main projects, is aimed at longer term issues, advanced technologies, and independent assessments. Topics to be discussed include bearings, linear alternators, controls and load interaction, materials/life assessment, and heat exchangers.

Thieme, Lanny G.↗
NASA NTRS2002

Dosimetric results from the Mir orbital station

The Mir Orbital Station provided a unique platform on which to carry out a variety of space radiation dosimetry measurements. A number of experiments were conducted using a combination of passive detectors on the interior of the Mir during 1996-97. Thermoluminescent detectors were used to measure absorbed dose. CR-39 plastic nuclear track detectors were used to measure the LET spectra > or =5 keV.microm(-1). Results from TLDs and CR-39 PNTDs were combined to determine total dose and dose equivalent. Mean dose rate was found to decrease while mean dose equivalent rate and average quality factor increased with increasing shielding. Secondary particles from proton-induced target fragmentation interactions, not primary HZE particles, were found to be the largest contributor to the LET spectrum above 100 keV.microm(-1). During the 1997 measurements, mean quality factor was found to vary from 1.7 to 2.1 as a function of location within the Mir.

long duration↗
NASA NTRS1999

Mathematical model to estimate risk of calcium-containing renal stones

BACKGROUND/AIMS: Astronauts exposed to microgravity during the course of spaceflight undergo physiologic changes that alter the urinary environment so as to increase the risk of renal stone formation. This study was undertaken to identify a simple method with which to evaluate the potential risk of renal stone development during spaceflight. METHOD: We used a large database of urinary risk factors obtained from 323 astronauts before and after spaceflight to generate a mathematical model with which to predict the urinary supersaturation of calcium stone forming salts. RESULT: This model, which involves the fewest possible analytical variables (urinary calcium, citrate, oxalate, phosphorus, and total volume), reliably and accurately predicted the urinary supersaturation of the calcium stone forming salts when compared to results obtained from a group of 6 astronauts who collected urine during flight. CONCLUSIONS: The use of this model will simplify both routine medical monitoring during spaceflight as well as the evaluation of countermeasures designed to minimize renal stone development. This model also can be used for Earth-based applications in which access to analytical resources is limited.

NASA Center JSC↗
NASA NTRSDate not supplied

Status and Predicted Performance for the AstroPIC Integrated Photonic Coronagraph

Integrated photonics is a promising coronagraph technology option for exoplanet-imaging missions like NASA’s Habitable Worlds Observatory flagship. It is theoretically capable of achieving better performance than traditional bulk-optic coronagraphs because arrays of integrated interferometers can be combined to implement any linear operator. However, photonic coronagraphs require significant maturation to be ready for a space telescope mission. The AstroPIC project is advancing this technology by developing a proof-of-concept integrated photonic coronagraph based on silicon photonic integrated circuit (PIC) technology. Specifically, the AstroPIC program is investigating the impact of a PIC coronagraph on the predicted scientific yield of the upcoming Habitable Worlds Observatory (HWO) mission concept. In this talk, we will present the current status of the AstroPIC design, including the layout of the most recent PIC. We will also present on the status of simulations that predict the performance of the instrument and feed into scientific yield estimations for HWO Exoploratory Analytic Cases (EACs) 1-3. Finally, we will present the status of the development of a PIC testbed at NASA Ames and results from preliminary PIC laboratory testing at Stanford.

Photonics↗
NASA NTRS2005

Protograph based LDPC codes with minimum distance linearly growing with block size

We propose several LDPC code constructions that simultaneously achieve good threshold and error floor performance. Minimum distance is shown to grow linearly with block size (similar to regular codes of variable degree at least 3) by considering ensemble average weight enumerators. Our constructions are based on projected graph, or protograph, structures that support high-speed decoder implementations. As with irregular ensembles, our constructions are sensitive to the proportion of degree-2 variable nodes. A code with too few such nodes tends to have an iterative decoding threshold that is far from the capacity threshold. A code with too many such nodes tends to not exhibit a minimum distance that grows linearly in block length. In this paper we also show that precoding can be used to lower the threshold of regular LDPC codes. The decoding thresholds of the proposed codes, which have linearly increasing minimum distance in block size, outperform that of regular LDPC codes. Furthermore, a family of low to high rate codes, with thresholds that adhere closely to their respective channel capacity thresholds, is presented. Simulation results for a few example codes show that the proposed codes have low error floors as well as good threshold SNFt performance.

minimum decoding↗
DOE OSTI2023

Alfvén eigenmode stability in a JET afterglow deuterium plasma and projections to deuterium–tritium plasmas

Abstract The performance of fusion devices relies strongly on the good confinement of energetic particles (EPs). Therefore, the investigation of EP transport by magnetohydrodynamic instabilities is one of the key aspects in the development of plasma scenarios. Alfvénic instabilities in particular can lead to significant losses of alpha particles that are essential for plasma self-heating. A so-called afterglow scheme has been developed to study the destabilization of Alfvén eigenmodes (AEs) by alpha particles and associated EP transport in the JET tokamak. In this work, the linear stability of AEs is discussed for the partial afterglow phase in a JET deuterium plasma discharge and for the full afterglow phase in a projected deuterium–tritium (DT) plasma. Thanks to recent upgrades in the tokamak transport code TRANSP, one can account for the contributions of different EP species to mode stability. Analysis of deuterium plasmas shows that AE growth rates are extremely sensitive to the energy and distribution of fast ions. An increase in fast ion energy can lead to more unstable AEs. In the afterglow phase of projected DT plasmas, it is EPs that mostly drive the AEs. However, the drive by alpha particles is comparable to that by beam ions and their contribution to the net growth rate might be hard to separate. According to the discussed projections, the destabilization of AEs might be ineffective because the background plasma damping significantly exceeds the EP drive. In this case, the development of an alternative plasma scenario that allows us to overcome such damping would be required in future experiments.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Materials Data on Pd2O by Materials Project

Pd2O is Cuprite structured and crystallizes in the cubic Pn-3m space group. The structure is three-dimensional. Pd is bonded in a linear geometry to two equivalent O atoms. Both Pd–O bond lengths are 1.97 Å. O is bonded to four equivalent Pd atoms to form corner-sharing OPd4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr2O by Materials Project

Zr2O is Cuprite structured and crystallizes in the cubic Pn-3m space group. The structure is three-dimensional. Zr is bonded in a linear geometry to two equivalent O atoms. Both Zr–O bond lengths are 2.11 Å. O is bonded to four equivalent Zr atoms to form corner-sharing OZr4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ag2O by Materials Project

Ag2O is Cuprite structured and crystallizes in the cubic Pn-3m space group. The structure is three-dimensional. Ag1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Ag–O bond lengths are 2.10 Å. O2- is bonded to four equivalent Ag1+ atoms to form corner-sharing OAg4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cu2O by Materials Project

Cu2O is Cuprite structured and crystallizes in the cubic Pn-3m space group. The structure is three-dimensional. Cu1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Cu–O bond lengths are 1.86 Å. O2- is bonded to four equivalent Cu1+ atoms to form corner-sharing OCu4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pb2O by Materials Project

Pb2O is Cuprite structured and crystallizes in the cubic Pn-3m space group. The structure is three-dimensional. Pb is bonded in a linear geometry to two equivalent O atoms. Both Pb–O bond lengths are 2.37 Å. O is bonded to four equivalent Pb atoms to form corner-sharing OPb4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PH9AuC3ClO3 by Materials Project

AuC3PH9O3Cl crystallizes in the orthorhombic Pbca space group. The structure is zero-dimensional and consists of eight akos030621936 molecules. Au1- is bonded in a linear geometry to one P5+ and one Cl1- atom. The Au–P bond length is 2.24 Å. The Au–Cl bond length is 2.34 Å. There are three inequivalent C2- sites. In the first C2- site, C2- is bonded to three H1+ and one O2- atom to form CH3O tetrahedra that share a cornercorner with one PAuO3 tetrahedra. All C–H bond lengths are 1.10 Å. The C–O bond length is 1.46 Å. In the second C2- site, C2- is bonded to three H1+ and one O2- atom to form CH3O tetrahedra that share a cornercorner with one PAuO3 tetrahedra. All C–H bond lengths are 1.10 Å. The C–O bond length is 1.46 Å. In the third C2- site, C2- is bonded to three H1+ and one O2- atom to form CH3O tetrahedra that share a cornercorner with one PAuO3 tetrahedra. There is one shorter (1.09 Å) and two longer (1.10 Å) C–H bond length. The C–O bond length is 1.46 Å. P5+ is bonded to one Au1- and three O2- atoms to form distorted PAuO3 tetrahedra that share corners with three CH3O tetrahedra. There is two shorter (1.60 Å) and one longer (1.61 Å) P–O bond length. There are nine inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to one C2- and one P5+ atom. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to one C2- and one P5+ atom. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to one C2- and one P5+ atom. Cl1- is bonded in a single-bond geometry to one Au1- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PH9AuC3S3Cl by Materials Project

AuC3PH9S3Cl crystallizes in the orthorhombic Pbca space group. The structure is zero-dimensional and consists of eight AuC3PH9S3Cl clusters. Au1- is bonded in a linear geometry to one P5+ and one Cl1- atom. The Au–P bond length is 2.27 Å. The Au–Cl bond length is 2.34 Å. There are three inequivalent C2- sites. In the first C2- site, C2- is bonded in a trigonal non-coplanar geometry to three H1+ and one S2- atom. There is one shorter (1.09 Å) and two longer (1.10 Å) C–H bond length. The C–S bond length is 1.82 Å. In the second C2- site, C2- is bonded in a trigonal non-coplanar geometry to three H1+ and one S2- atom. There is one shorter (1.09 Å) and two longer (1.10 Å) C–H bond length. The C–S bond length is 1.82 Å. In the third C2- site, C2- is bonded in a trigonal non-coplanar geometry to three H1+ and one S2- atom. There is one shorter (1.09 Å) and two longer (1.10 Å) C–H bond length. The C–S bond length is 1.82 Å. P5+ is bonded in a tetrahedral geometry to one Au1- and three S2- atoms. There are two shorter (2.10 Å) and one longer (2.11 Å) P–S bond lengths. There are nine inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded in a water-like geometry to one C2- and one P5+ atom. In the second S2- site, S2- is bonded in a water-like geometry to one C2- and one P5+ atom. In the third S2- site, S2- is bonded in a water-like geometry to one C2- and one P5+ atom. Cl1- is bonded in a single-bond geometry to one Au1- atom.

36 MATERIALS SCIENCE↗