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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 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
NASA NTRS2009

Static Aeroelastic Effects of Formation Flight for Slender Unswept Wings

The static aeroelastic equilibrium equations for slender, straight wings are modified to incorporate the effects of aerodynamically-coupled formation flight. A system of equations is developed by applying trim constraints and is solved for component lift distribution, trim angle-of-attack, and trim aileron deflection. The trim values are then used to calculate the elastic twist distribution of the wing box. This system of equations is applied to a formation of two gliders in trimmed flight. Structural and aerodynamic properties are assumed for the gliders, and solutions are calculated for flexible and rigid wings in solo and formation flight. It is shown for a sample application of two gliders in formation flight, that formation disturbances produce greater twist in the wingtip immersed in the vortex than for either the opposing wingtip or the wings of a similar airplane in solo flight. Changes in the lift distribution, resulting from wing twist, increase the performance benefits of formation flight. A flexible wing in formation flight will require greater aileron deflection to achieve roll trim than a rigid wing.

Hanson, Curtis E.↗
NASA NTRS1995

Pressure correlations at a fluid/structure interface

The structure of pressure-pressure correlations at the interface of an incompressible steady-state turbulent flow with a rigid boundary was investigated. For the sake of completeness, the absolute value of the correlation between two random varying functions is herein defined as a number greater than or equal to zero and less than or equal to unity which is a measure of that fraction of one of the functions that 'follows' the second function (or vice versa). It was found that the soughtafter correlations can be determined by consideration of the high Re Navier-Stokes equation, but that the complexity of boundary layer turbulence, in particular the inhomogeneity perpendicular to the boundary and the anisotropy due to convective flow gradients, makes the structure of said correlations extremely difficult to assess. One of the earlier researchers in this field described the quantity under present consideration as 'a quantity which is beyond assessment.' Nonetheless, it was found that under some rather simplifying assumptions the determination of the required structure necessitates the formulation of the related structure of second order two-point correlations of turbulent velocity gradients, as well as third order two-point correlations of velocity gradients. The presence of these latter gradients is due to the nonlinearity in the turbulence ('turbulence self-interaction'). Both of these correlations are scaled, although not similarly, by factors dependent upon the magnitude of the convective flow, which can be modeled using a log law approximation. Fourth order correlations, although present, can be ignored, since they constitute 'higher order terms.' In a slightly more complex situation, it was found that convective flow gradients also have to be incorporated. At the moment, no definitive algebraic information peculiar to pressure-pressure correlations is available in the most highly idealized cases.

Trevino, George↗
NASA NTRS1974

The response of many-storied structures under seismic actions

A seismic action which is characterized by the acceleration function of the seismic motion is analyzed. The equations of motion in the direction of the seismic action are determined for a completely rigid ground and for a ground with linear deformability characteristics (rotation deformability). The equation for the rotation motion is derived by considering elastic and viscoelastic properties of the foundation ground. The differential equations are written by treating the mechanical model of a many-storied structure as a fixed vertical beam with a uniformly distributed mass as well as with concentrated masses on each floor.

Munteanu, K.↗
NASA NTRS1987

A Numerical Model of Unsteady, Subsonic Aeroelastic Behavior

A method for predicting unsteady, subsonic aeroelastic responses was developed. The technique accounts for aerodynamic nonlinearities associated with angles of attack, vortex-dominated flow, static deformations, and unsteady behavior. The fluid and the wing together are treated as a single dynamical system, and the equations of motion for the structure and flow field are integrated simultaneously and interactively in the time domain. The method employs an iterative scheme based on a predictor-corrector technique. The aerodynamic loads are computed by the general unsteady vortex-lattice method and are determined simultaneously with the motion of the wing. Because the unsteady vortex-lattice method predicts the wake as part of the solution, the history of the motion is taken into account; hysteresis is predicted. Two models are used to demonstrate the technique: a rigid wing on an elastic support experiencing plunge and pitch about the elastic axis, and an elastic wing rigidly supported at the root chord experiencing spanwise bending and twisting. The method can be readily extended to account for structural nonlinearities and/or substitute aerodynamic load models. The time domain solution coupled with the unsteady vortex-lattice method provides the capability of graphically depicting wing and wake motion.

Strganac, Thomas W.↗
DOE OSTI2025

How do substituted phenyl-based cations affect the structure-property-stability relationship of low-dimensional perovskites?

Incorporating organic bulky cations in the precursor or post-treatment to achieve two-dimensional/three-dimensional (2D/3D) heterojunction is an effective strategy for enhancing the stability of perovskite materials. However, the issue of insufficient charge transport in 2D perovskites limits their development, and the fundamental mechanism of out-of-plane carrier transport remains unclear. This study designed and synthesized seven organic phenyl-core cations, differentiated at the 1- and 1,4-positions, and identified the impacts on the corresponding properties of the 2D crystalline perovskite. Shorter cations facilitated a more compact arrangement of adjacent inorganic layers, aligning to favor charge transport along the vertical direction. In addition, introducing high electronegativity led to increased intermolecular interactions, resulting in enhanced structural stability and improved phenyl ring π-orbital overlap and interlayer electron coupling, yielding efficient charge transport. Resilience to thermal stressing of the perovskite was strongly correlated with the carbon chain length of the spacer cations. Here, the increase in cation length and the reduction in the rigidity of the amino-terminal both aided in the dispersion of thermal stress in the inorganic framework. Additional hydrogen bonding also contributed to mitigating structural disorder.

14 SOLAR ENERGY↗
DOE OSTI2026

Adsorption of CO on gold: effect of coverage and surface deformations

Recent insights into the nature of catalysts under reactive conditions have motivated investigating heterogeneously catalyzed reactions with non-rigid surfaces. As an example system to revisit, CO interactions with gold have been a longstanding system of interest due to its structure sensitivity. In this work, we investigate coverage-dependent CO adsorption trends on terraces, steps, and kinks. Calculating differential binding energy and mean absolute displacement of the atomic structures as a function of CO coverage, we propose a deformation quenching mechanism that partially determines CO saturation coverage. Extending this analysis to consider CO partial pressure, we show a phase change in CO step occupation, which we highlight as a possible explanation for previously reported temperature-programmed desorption and Fourier-transform infrared reflection-absorption spectroscopy measurements. Furthermore, this work shows how adopting a non-rigid surface model can lead to additional insights which may be applied to other heterogeneously catalyzed systems.

Kavalsky, Lance [University of Wisconsin-Madison, ↗
DOE OSTI2024

Ultrafast structural dynamics of UV photoexcited cis , cis -1,3-cyclooctadiene observed with time-resolved electron diffraction

Conjugated diene molecules are highly reactive upon photoexcitation and can relax through multiple reaction channels that depend on the position of the double bonds and the degree of molecular rigidity. Understanding the photoinduced dynamics of these molecules is crucial for establishing general rules governing the relaxation and product formation. Here, in this study, we investigate the femtosecond time-resolved photoinduced excited-state structural dynamics of cis,cis-1,3-cyclooctadiene, a large-flexible cyclic conjugated diene molecule, upon excitation with 200 nm using mega-electron-volt ultrafast electron diffraction and trajectory surface hopping dynamics simulations. We tracked the photoinduced structural changes from the Franck–Condon region through the conical intersection seam to the ground state. Our findings revealed a novel primary reaction coordinate involving ring distortion, where the ring stretches along one axis and compresses along the perpendicular axis. The nuclear wavepacket remains compact along this reaction coordinate until it reaches the conical intersection seam, and it rapidly spreads as it approaches the ground state, where multiple products are formed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1992

Laboratory evaluation of two advanced suspension devices for ground vibration testing of large space structures

In order to provide the advanced suspension technology needed to allow ground test measurement of free-body modal parameters, two advanced suspension devices, one passive, the other active, are evaluated on the basis of laboratory testing of each device type with rigid and flexible payloads. Rigid-body tests show the basic behavior of the devices when they are uncoupled from a test article near their bandwidth. Flexible body tests show how suspension device dynamics couple with the dynamics of a representative large space structure. For the flexible body testing, targets for the free-body modal parameters are developed from test-verified analysis of the representative structure suspended in an orientation which is only mildly sensitive to suspension constraints.

Cooley, Victor M.↗
NASA NTRS1987

An approach to structure/control simultaneous optimization for large flexible spacecraft

This paper presents an approach to the simultaneous optimal design of a structure and control system for large flexible spacecrafts based on realistic objective function and constraints. The weight or total cost of structure and control system is minimized subject to constraints on the magnitude of response to a given disturbance involving both rigid-body and elastic modes. A nested optimization technique is developed to solve the combined problem. As an example, simple beam-like spacecraft under a steady-state white-noise disturbance force is investigated and some results of optimization are presented. In the numerical examples, the stiffness distribution, location of controller, and control gains are optimized. Direct feedback control and linear quadratic optimal controls laws are used with both inertial and noninertial disturbing force. It is shown that the total cost is sensitive to the overall structural stiffness, so that simultaneous optimization of the structure and control system is indeed useful.

Onoda, Junjiro↗
NASA NTRS1980

An improved output feedback control of flexible large space structures

A special output feedback control design technique for flexible large space structures is proposed. It is shown that the technique will increase both the damping and frequency of selected modes for more effective control. It is also able to effect integrated control of elastic and rigid-body modes and, in particular, closed-loop system stability and robustness to modal truncation and parameter variation. The technique is seen as marking an improvement over previous work concerning large space structures output feedback control.

Lin, Y. H.↗
DOE OSTI2025

Thermal and mechanical performance of gypsum composites containing fly ash cenosphere encapsulated phase change materials

Utilizing phase change materials (PCMs) within construction materials improves the thermal energy storage capabilities in the built environment. Notably, integrating PCMs into drywalls presents a promising avenue to reduce building energy use. However, incorporating PCMs into drywalls poses challenges, particularly reduced mechanical properties and workability limitations as it can adversely affect the hardening and cohesiveness of gypsum composites. To address these challenges, this study explores a novel strategy to incorporate PCMs into gypsum composites through fly ash cenosphere-encapsulated PCM, namely CenoPCM, aiming to enhance the mechanical properties and thermal conductivity over existing commercial counterparts. An experimental program was conducted to study the impact of the inclusion of CenoPCM on the mechanical and thermal performance of gypsum composites, and the results were compared to those of commercially available polymerencapsulated PCM benchmark (Micronal). The findings highlighted that PCM-charged samples exhibited up to 95.90 J/g (CenoPCM) of latent heat with 70 % CenoPCM loading. The results of mechanical tests also showed that CenoPCM outperformed its polymer-encapsulated counterpart, achieving 55 % higher mechanical strength on average. Here, this improvement is attributed to the rigid shell of fly ash cenosphere (FAC) serving as a PCM carrier, providing a skeleton-like structure to gypsum composites for higher load-bearing capacity. Additionally, hotbox tests demonstrated that the CenoPCM-charged wall panels yielded a 20 % higher thermal conductivity and a 22 % increased time lag compared to Micronal PCM-charged panels, indicating its potential to shift the peak load in buildings.

Ceno PCM↗
NASA NTRS1962

Some Applications of Detailed Wind Profile Data to Launch Vehicle Response Problems

The response of a launch vehicle to a number of detailed wind profiles has been determined. The wind profiles were measured by two techniques which are briefly described. One of these techniques uses an angle-of-attack sensor in conjunction with guidance data to measure the wind profile traversed by some particular launch vehicle. The other wind-measuring technique is a photographic triangulation method, whereby two cameras take simultaneous pictures of a vertical trail of smoke left by a launch vehicle or sounding rocket. The response of a vehicle flying these detailed profiles is compared with the response of the same vehicle flying through balloon-measured profiles. The response to the detailed wind profiles, relative t o the balloon-measured profiles, is characterized by the large excitation of the rigid pitch and elastic bending modes. This is found to cause higher loads on the launch vehicle structure. Established design criteria which utilize balloon measured wind profiles have arbitrarily accounted-for this increased load by adding a load due to some type of discrete gust.

LAUNCH VEHICLE↗
NASA NTRS1981

A theoretical interpretation of Forbush decreases

An analysis is presented of the intensity variations of relativistic cosmic rays, at 1 AU, which are associated with the passage of a flare shock wave. The magnitude and time profile obtained is similar to that observed in flare-induced Forbush decreases, and the principal cause of the energy reduction is an increase in adiabatic cooling of the arriving particles due to prolonged containment behind the compressed field of the flare shock wave. The large decreases calculated for the smaller diffusion coefficients are inconsistent with observation, implying larger mean free paths than those traditionally assumed at these rigidities. The method presented may be used to study intensity variations associated with other large-scale structures of the interplanetary field, such as corotating interaction regions.

Gall, R.↗
NASA NTRS1986

An investigation of empennage buffeting

Progress in the investigation of empennage buffeting in reviewed. In summary, the following tasks were accomplished: relevant literatures was reviewed; equations for calculating structural response were formulated; root-mean-square values of root bending moment for a 65-degree rigid delta wing were calculated and compared with data; and a water-tunnel test program for an F-18 model was completed.

Lan, C. E.↗
NASA NTRS1992

Model of a rotating magnetic cloud

The possibility that magnetic clouds rotate while they propagate antisunward was investigated. Magnetic clouds are modeled as magnetic flux ropes which rotate rigidly about the axis of symmetry. An ideal magnetohydrodynamic model, in which the evolution of the magnetic structure is related to the time evolution of the angular frequency, is developed. A class of 'separable' magnetic fields is employed to reduce the problem to a nonlinear ordinary differential equation for the evolution function, and it is solved numerically. The corresponding effective potential gives rise to two modes of evolution--expansion and oscillation--depending on the energy and on the value of a dimensionless parameter, k. Parameter k depends on the gas pressure, the ratio of the magnetic field components, and the frequency of rotation. There is a critical value of k, k(sub c), above which the oscillatory regime disappears and the flux rope invariably expands, regardless of the energy. Below k(sub c) the energy determines whether the configuration is confined or unbounded. Rotation always helps expansion by lowering the potential barrier. A data example was studied and features which are interpreted as signatures of rotation are presented. The angular speed is comparable to the Alfven speed, and the core of the rotating cloud completes on average one full revolution every three days at 1 AU. The parameter k is calculated from observations, and it is found to be close to, but below, critical. Only three out of the nine clouds examined showed signatures of rotation. Theoretical analysis suggests that close to the Sun rotation effects may play a more important role in the evolution of magnetic clouds than 1 AU.

Farrugia, C. J.↗
NASA NTRS1994

Estimating lithospheric properties at Atla Regio, Venus

Magellan spehrical harmonic gravity and topography models are used to estimate lithospheric properties at Alta Regio, Venus, a proposed hotspot with dynamic support from mantle plume(s). Global spherical harmonic and local representations of the gravity field share common properties in the Atla region interms of their spectral behavior over a wavelength band from approximately 2100 to approximately 700 km. The estimated free-air admittance spectrum displays a rather featureless long-wavelength portion followed by a sharp rise at wavelengths shorter than about 1000 km. This sharp rise requires significant flexural support of short-wavelength structures. The Bouguer coherence also displays a sharp drop in this wavelength band, indicating a finite flexural rigidity of the lithosphere. A simple model for lithospheric loading from above and below is introduced (D. W. Forsyth, 1985) with four parameters: f, the ratio of bottom loading to top loading; z(sub m), crustal thickness; z(sub l) depth to bottom loading source; and T(sub e) elastic lithosphere thickness. A dual-mode compensation model is introduced in which the shorter wavelengths (lambda approximately less than 1000 km) might be explained best by a predominance of top loading by the large shield volcanoes Maat Mons, Ozza Mons, and Sapas Mons, and the longer wavelengths (lambda approximately greater than 1500 km) might be explained best by a deep depth of compensation, possibly representing bottom loading by a dynamic source. A Monte Carlo inversion technique is introduced to thoroughly search out the four-space of the model parameters and to examine parameter correlation in the solutions. Venus either is a considerabe deficient in heat sources relative to Earth, or the thermal lithosphere is overthickened in response to an earlier episode of significant heat loss from the planet.

Phillips, Roger J.↗
NASA NTRS1997

"TPSX: Thermal Protection System Expert and Material Property Database"

The Thermal Protection Branch at NASA Ames Research Center has developed a computer program for storing, organizing, and accessing information about thermal protection materials. The program, called Thermal Protection Systems Expert and Material Property Database, or TPSX, is available for the Microsoft Windows operating system. An "on-line" version is also accessible on the World Wide Web. TPSX is designed to be a high-quality source for TPS material properties presented in a convenient, easily accessible form for use by engineers and researchers in the field of high-speed vehicle design. Data can be displayed and printed in several formats. An information window displays a brief description of the material with properties at standard pressure and temperature. A spread sheet window displays complete, detailed property information. Properties which are a function of temperature and/or pressure can be displayed as graphs. In any display the data can be converted from English to SI units with the click of a button. Two material databases included with TPSX are: 1) materials used and/or developed by the Thermal Protection Branch at NASA Ames Research Center, and 2) a database compiled by NASA Johnson Space Center 9JSC). The Ames database contains over 60 advanced TPS materials including flexible blankets, rigid ceramic tiles, and ultra-high temperature ceramics. The JSC database contains over 130 insulative and structural materials. The Ames database is periodically updated and expanded as required to include newly developed materials and material property refinements.

Squire, Thomas H.↗
NASA NTRS2004

Do Integrins Mediate the Skeletal Response to Altered Loading?

In vivo experiments were performed to examine the role of B1 integrin in skeletal adaptation to reduced and increased loading. Transgenic mice were generated with a dominant negative form of the B1 integrin cytoplasmic domain with expression driven by the osteocalcin promoter (pOCb1DN). This fragment consists of the transmembrane and intracellular domains and interferes with endogenous integrin signalling in vitro. This promoter targets expression of the transgene to mature bone cells. Expression of the transgene was confirmed by immunoprecipitation and western blotting. Reduced loading was generated by hindlimb suspension and increased loading the resumption of normal loading following hindlimb suspension. Two groups of female 35-day old mice were examined: poCb1DN transgenic mice (TG) and wild-type littermate controls (WT). Animals were hindlimb suspended for 1 week (HU, n = l0/gp) or 4 weeks (HU, n = 4 - 7/gp) or suspended for 4 weeks followed by reloading by normal ambulation for 4 weeks (RL, n = l0/gp). Age-matched controls (CT) were pairfed based on the HU food intake. The protocols were approved by the NASA Ames Research Center IACUC. Upon completion of the experimental protocol, body mass was recorded and tissues of interest removed and analyzed following standard procedures. Femoral whole bone structural behavior was measured in torsion to failure to obtain whole bone strength (failure torque) and torsional rigidity. Ash content (ash) and fraction (% ash) were determined for the tibia. Total ash is indicative of bone size whereas %ash is a material property. Tibial curvature was measured from microradiographs. For each experiment, the effects of genotype (TG, WT) and treatment (CT, HU/RL) were assessed by two-factor ANOVA followed by the Tukey-Kramer posthoc to identify significant differences at an alpha level of 0.05. Our goal was to understand differences resulting from altered integrin function in the adaptation to altered loading.

vanderMeulen, Marjolein C. H.↗