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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 1,801 records · Page 100
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Determination of functional collective motions in a protein at atomic resolution using coherent neutron scattering

Protein function often depends on global, collective internal motions. However, the simultaneous quantitative experimental determination of the forms, amplitudes, and time scales of these motions has remained elusive. We demonstrate that a complete description of these large-scale dynamic modes can be obtained using coherent neutron-scattering experiments on perdeuterated samples. With this approach, a microscopic relationship between the structure, dynamics, and function in a protein, cytochrome P450cam, is established. The approach developed here should be of general applicability to protein systems.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1982

Development of methodology for horizontal axis wind turbine dynamic analysis

Horizontal axis wind turbine dynamics were studied. The following findings are summarized: (1) review of the MOSTAS computer programs for dynamic analysis of horizontal axis wind turbines; (2) review of various analysis methods for rotating systems with periodic coefficients; (3) review of structural dynamics analysis tools for large wind turbine; (4) experiments for yaw characteristics of a rotating rotor; (5) development of a finite element model for rotors; (6) development of simple models for aeroelastics; and (7) development of simple models for stability and response of wind turbines on flexible towers.

Dugundji, J.↗
NASA NTRS1990

Advances and trends in computational structures technology

The major goals of computational structures technology (CST) are outlined, and recent advances in CST are examined. These include computational material modeling, stochastic-based modeling, computational methods for articulated structural dynamics, strategies and numerical algorithms for new computing systems, multidisciplinary analysis and optimization. The role of CST in the future development of structures technology and the multidisciplinary design of future flight vehicles is addressed, and the future directions of CST research in the prediction of failures of structural components, the solution of large-scale structural problems, and quality assessment and control of numerical simulations are discussed.

Noor, A. K.↗
NASA NTRS1993

Experimental unsteady pressures at flutter on the Supercritical Wing Benchmark Model

This paper describes selected results from the flutter testing of the Supercritical Wing (SW) model. This model is a rigid semispan wing having a rectangular planform and a supercritical airfoil shape. The model was flutter tested in the Langley Transonic Dynamics Tunnel (TDT) as part of the Benchmark Models Program, a multi-year wind tunnel activity currently being conducted by the Structural Dynamics Division of NASA Langley Research Center. The primary objective of this program is to assist in the development and evaluation of aeroelastic computational fluid dynamics codes. The SW is the second of a series of three similar models which are designed to be flutter tested in the TDT on a flexible mount known as the Pitch and Plunge Apparatus. Data sets acquired with these models, including simultaneous unsteady surface pressures and model response data, are meant to be used for correlation with analytical codes. Presented in this report are experimental flutter boundaries and corresponding steady and unsteady pressure distribution data acquired over two model chords located at the 60 and 95 percent span stations.

Dansberry, Bryan E.↗
NASA NTRS1990

Configuration design sensitivity analysis of built-up structures

In the design of complex built-up structures that are made of truss, beam, membrane, shell, and solid, there are five different kinds of design variables: material property, sizing, shape, configuration, and topological variables. Previous research has shown that the improvement in performances obtained by altering the configuration of structural components can be much more significant than those obtained when the geometry is assumed to be fixed. Using the variational approach, a unified design sensitivity was developed for the first three kinds of design variables, and was further extended recently in many structural analysis problems such as nonlinear, structural dynamics, and frequency response analysis. A continuum design sensitivity analysis method is developed for the configuration design variable of built-up structures.

Choi, Kyung K.↗
NASA NTRS2005

Review of NASA In-Space Propulsion Technology Program Inflatable Decelerator Investments

The NASA In-Space Propulsion Technology (ISPT) Program is managed by the NASA Headquarters Science Mission Directorate and is implemented by the Marshall Space Flight Center in Huntsville, Alabama. The ISPT objective is to fund development of promising in-space propulsion technologies that can decrease flight times, decrease cost, or increase delivered payload mass for future science missions. Before ISPT will invest in a technology, the Technology Readiness Level (TRL) of the concept must be estimated to be at TRL 3. A TRL 3 signifies that the technical community agrees that the feasibility of the concept has been proven through experiment or analysis. One of the highest priority technology investments for ISPT is Aerocapture. The aerocapture maneuver uses a planetary atmosphere to reduce or alter the speed of a vehicle allowing for quick, propellantless (or using very little propellant) orbit capture. The atmosphere is used as a brake, transferring the energy associated with the vehicle's high speed into thermal energy. The ISPT Aerocapture Technology Area (ATA) is currently investing in the development of advanced lightweight ablative thermal protection systems, high temperature composite structures, and heat-flux sensors for rigid aeroshells. The heritage of rigid aeroshells extends back to the Apollo era and this technology will most likely be used by the first generation aerocapture vehicle. As a second generation aerocapture technology, ISPT is investing in three inflatable aerodynamic decelerator concepts for planetary aerocapture. They are: trailing ballute (balloon-parachute), attached afterbody ballute, and an inflatable aeroshell. ISPT also leverages the NASA Small Business Innovative Research Program for additional inflatable decelerator technology development. In mid-2004 ISPT requested an independent review of the three inflatable decelerator technologies funded directly by ISPT to validate the TRL and to identify technology maturation concerns. An independent panel with expertise in advanced thin film materials, aerothermodynamics, trajectory design, and inflatable structures was convened to assess the ISPT investments. The panel considered all major technical subsystems including materials, aerothermodynamics, structural dynamics, packaging, and inflation systems. The panel assessed the overall technology readiness of inflatable decelerators to be a 3 and identified fluid- structure interaction, aeroheating, and structural adhesives to be of highest technical concern.

Richardson, E. H.↗
NASA NTRS2006

Dynamics of Orbital Masses in an Unbalanced Rotor

Historically, orbital masses have been used as automatic balancers in rotating machines. However, in these applications, the masses are free to move and rotate with the rotor from zero to operating speeds. For gas turbine applications it is desirable for the orbital masses to be fixed and unmoving, until their release from a sudden unbalance at the operating speed, such as occurs from a blade-out event. The objective of this work is to develop the dynamical equations of motion for orbital masses on a rotating shaft. In subsequent work these equations will be incorporated into a rotor structural dynamics computer code and the feasibility of attenuating rotor unbalance response with orbital masses will be investigated.

Gallardo, Vicente↗
NASA NTRS2012

Structural Verification of the First Orbital Wonder of the World - The Structural Testing and Analysis of the International Space Station (ISS)

The International Space Station (ISS) can be considered one of the structural engineering wonders of the world. On par with the World Trade Center, the Colossus of Rhodes, the Statue of Liberty, the Great Pyramids, the Petronas towers and the Burj Khalifa skyscraper of Dubai, the ambition and scope of the ISS structural design, verification and assembly effort is a truly global success story. With its on-orbit life projected to be from its beginning in 1998 to the year 2020 (and perhaps beyond), all of those who participated in its development can consider themselves part of an historic engineering achievement representing all of humanity. The structural design and verification of the ISS could be the subject of many scholarly papers. Several papers have been written on the structural dynamic characterization of the ISS once it was assembled on-orbit [1], but the ground-based activities required to assure structural integrity and structural life of the individual elements from delivery to orbit through assembly and planned on-orbit operations have never been totally summarized. This paper is intended to give the reader an overview of some of the key decisions made during the structural verification planning for the elements of the U.S. On-Orbit Segment (USOS) as well as to summarize the many structural tests and structural analyses that were performed on its major elements. An effort is made for this paper to be summarily comprehensive, but as with all knowledge capture efforts of this kind, there are bound to be errors of omission. Should the reader discover any of these, please feel free to contact the principal author. The ISS (Figure 1) is composed of pre-integrated truss segments and pressurized elements supplied by NASA, the Russian Federal Space Agency (RSA), the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA). Each of these elements was delivered to orbit by a launch vehicle and connected to one another either robotically or autonomously. The primary structure of each element was assembled and verified by teams of responsible structural engineers within and among their respective agencies and agency contractors.

Zipay, John J.↗
NASA NTRS1997

National Transonic Facility Model and Tunnel Vibrations

Since coming online in 1984, the National Transonic Facility (NTF) cryogenic wind tunnel at the NASA Langley Research Center has provided unique high Reynolds number testing capability. While turbulence levels in the tunnel, expressed in terms of percent dynamic pressure, are typical of other transonic wind tunnels, the significantly increased load levels utilized to achieve flight Reynolds numbers, in conjunction with the unique structural design requirements for cryogenic operation, have brought forward the issue of model and model support structure vibrations. This paper reports new experimental measurements documenting aerodynamic and structural dynamics processes involved in such vibrations experienced in the NTF. In particular, evidence of local un-steady airloads developed about the model support strut is shown and related to well documented acoustic features known as "Parker" modes. Two-dimensional unsteady viscous computations illustrate this model support structure loading mechanism.

Edwards, John W.↗
DOE OSTI2020

Structural evidence for a dynamic metallocofactor during N 2 reduction by Mo-nitrogenase

The enzyme nitrogenase uses a suite of complex metallocofactors to reduce dinitrogen (N 2 ) to ammonia. Mechanistic details of this reaction remain sparse. We report a 1.83-angstrom crystal structure of the nitrogenase molybdenum-iron (MoFe) protein captured under physiological N 2 turnover conditions. This structure reveals asymmetric displacements of the cofactor belt sulfurs (S2B or S3A and S5A) with distinct dinitrogen species in the two αβ dimers of the protein. The sulfur-displaced sites are distinct in the ability of protein ligands to donate protons to the bound dinitrogen species, as well as the elongation of either the Mo–O5 (carboxyl) or Mo–O7 (hydroxyl) distance that switches the Mo-homocitrate ligation from bidentate to monodentate. These results highlight the dynamic nature of the cofactor during catalysis and provide evidence for participation of all belt-sulfur sites in this process.

Science & Technology - Other Topics↗
DOE OSTI2017

Atomic-level structural correlations across the morphotropic phase boundary of a ferroelectric solid solution: xBiMg 1/2 Ti 1/2 O 3 -(1$-$x)PbTiO 3

Revelation of unequivocal structural information at the atomic level for complex systems is uniquely important for deeper and generic understanding of the structure property connections and a key challenge in materials science. Here in this paper we report an experimental study of the local structure by applying total elastic scattering and Raman scattering analyses to an important non-relaxor ferroelectric solid solution exhibiting the so-called composition-induced morphotropic phase boundary (MPB), where concomitant enhancement of physical properties have been detected. The powerful combination of static and dynamic structural probes enabled us to derive direct correspondence between the atomic-level structural correlations and reported properties. The atomic pair distribution functions obtained from the neutron total scattering experiments were analysed through big-box atom-modelling implementing reverse Monte Carlo method, from which distributions of magnitudes and directions of off-centred cationic displacements were extracted. We found that an enhanced randomness of the displacement-directions for all ferroelectrically active cations combined with a strong dynamical coupling between the A- and B-site cations of the perovskite structure, can explain the abrupt amplification of piezoelectric response of the system near MPB. Finally, altogether this provides a more fundamental basis in inferring structure-property connections in similar systems including important implications in designing novel and bespoke materials.

36 MATERIALS SCIENCE↗
NASA NTRS1974

Dynamics computation methodology applied to railcar vibrations

The analytical models discussed present typical examples of analyses performed to optimize vehicle parameters and solve specific engineering problems. Subjects investigated include: (1) car body structural dynamics, (2) vehicle dynamic motions and loads, and (3) truck equalization.

Vlaminck, R. R.↗
DOE OSTI2025

From sequence to protein structure and conformational dynamics with artificial intelligence/machine learning

The 2024 Nobel Prize in Chemistry was awarded in part for de novo protein structure prediction using AlphaFold2, an artificial intelligence/machine learning (AI/ML) model trained on vast amounts of sequence and three-dimensional structure data. AlphaFold2 and related models, including RoseTTAFold and ESMFold, employ specialized neural network architectures driven by attention mechanisms to infer relationships between sequence and structure. At a fundamental level, these AI/ML models operate on the long-standing hypothesis that the structure of a protein is determined by its amino acid sequence. More recently, AlphaFold2 has been adapted for the prediction of multiple protein conformations by subsampling multiple sequence alignments. Herein, we provide an overview of the deterministic relationship between sequence and structure, which was hypothesized over half a century ago with profound implications for the biological sciences ever since. We postulate that protein conformational dynamics are also determined, at least in part, by amino acid sequence and that this relationship may be leveraged for construction of AI/ML models dedicated to predicting protein conformational ensembles. Accordingly, we describe a conceptual model architecture, which may be trained on sequence data in combination with conformationally sensitive structural information, coming primarily from nuclear magnetic resonance (NMR) spectroscopy. Notwithstanding certain limitations in this context, NMR offers abundant structural heterogeneity conducive to conformational ensemble prediction. As NMR and other data continue to accumulate, sequence-informed prediction of protein structural dynamics with AI/ML has the potential to emerge as a transformative capability across the biological sciences.

Artificial intelligence↗
DOE OSTI2017

Polarized XANES Monitors Femtosecond Structural Evolution of Photoexcited Vitamin B 12

Ultrafast, polarization-selective time-resolved X-ray absorption near-edge structure (XANES) was used to characterize the photochemistry of vitamin B 12 , cyanocobalamin (CNCbl), in solution. Cobalamins are important biological cofactors involved in methyl transfer, radical rearrangement, and light-activated gene regulation, while also holding promise as light-activated agents for spatiotemporal controlled delivery of therapeutics. We introduce polarized femtosecond XANES, combined with UV–visible spectroscopy, to reveal sequential structural evolution of CNCbl in the excited electronic state. Femtosecond polarized XANES provides the crucial structural dynamics link between computed potential energy surfaces and optical transient absorption spectroscopy. Polarization selectivity can be used to uniquely identify electronic contributions and structural changes, even in isotropic samples when well-defined electronic transitions are excited. Our XANES measurements reveal that the structural changes upon photoexcitation occur mainly in the axial direction, where elongation of the axial Co–CN bond and Co–N Im bond on a 110 fs time scale is followed by corrin ring relaxation on a 260 fs time scale. In conclusion, these observations expose features of the potential energy surfaces controlling cobalamin reactivity and deactivation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Tetrahedral triple-Q magnetic ordering and large spontaneous Hall conductivity in the metallic triangular antiferromagnet Co 1/3 TaS 2

The triangular lattice antiferromagnet (TLAF) has been the standard paradigm of frustrated magnetism for several decades. The most common magnetic ordering in insulating TLAFs is the 120° structure. However, a new triple-Q chiral ordering can emerge in metallic TLAFs, representing the short wavelength limit of magnetic skyrmion crystals. We report the metallic TLAF Co 1 / 3 TaS 2 as the first example of tetrahedral triple-Q magnetic ordering with the associated topological Hall effect (non-zero σ xy (H = 0)). We also present a theoretical framework that describes the emergence of this magnetic ground state, which is further supported by the electronic structure measured by angle-resolved photoemission spectroscopy. Additionally, our measurements of the inelastic neutron scattering cross section are consistent with the calculated dynamical structure factor of the tetrahedral triple-Q state.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Statistical inference of collision frequencies from x-ray Thomson scattering spectra

Thomson scattering spectra measure the response of plasma particles to incident radiation. In warm dense matter, which is opaque to visible light, x-ray Thomson scattering (XRTS) enables a detailed probe of the electron distribution and has been used as a diagnostic for electron temperature, density, and plasma ionization. In this work, we examine the sensitivities of inelastic XRTS signatures to modeling details, including the dynamic collision frequency and the electronic density of states. Applying verified Monte Carlo inversion methods to dynamic structure factors obtained from time-dependent density functional theory, we assess the utility of XRTS signals as a way to inform the dynamic collision frequency, especially its direct-current limit, which is directly related to the electrical conductivity.

Collision frequency↗
NASA NTRS1979

Crash simulation of composite and aluminum helicopter fuselages using a finite-element program

This paper describes a mathematical investigation of the crash-impact responses of an all-composite helicopter cockpit section incorporating an energy absorbing concept and one of conventional aluminum construction, using the Grumman DYCAST finite-element nonlinear structural dynamics computer program. The overall objective of this initial investigation was to explore the application of DYCAST to the design of future helicopter structures. The specific purposes are to assess the value of the finite-element code as a crashworthiness design analysis tool, and to compare the responses of the two fuselage sections. The results indicate that the finite-element simulation is a powerful analysis tool, providing sufficient detail to evaluate individual structural components, and that the crashworthiness of an all-composite cockpit section could be enhanced with energy-absorbing concepts

Winter, R.↗
NASA NTRS1988

Effects of model deficiencies on parameter estimation

Reliable structural dynamic models will be required as a basis for deriving the reduced-order plant models used in control systems for large space structures. Ground vibration testing and model verification will play an important role in the development of these models; however, fundamental differences between the space environment and earth environment, as well as variations in structural properties due to as-built conditions, will make on-orbit identification essential. The efficiency, and perhaps even the success, of on-orbit identification will depend on having a valid model of the structure. It is envisioned that the identification process will primarily involve parametric methods. Given a correct model, a variety of estimation algorithms may be used to estimate parameter values. This paper explores the effects of modeling errors and model deficiencies on parameter estimation by reviewing previous case histories. The effects depend at least to some extent on the estimation algorithm being used. Bayesian estimation was used in the case histories presented here. It is therefore conceivable that the behavior of an estimation algorithm might be useful in detecting and possibly even diagnosing deficiencies. In practice, the task is complicated by the presence of systematic errors in experimental procedures and data processing and in the use of the estimation procedures themselves.

Hasselman, T. K.↗

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