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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Self-shadowing of orbiting trusses

The approach used to assess shadowing reductions on the heating of orbiting trusses involves determining the heating rates with slender member shadowing effects included and then obtaining the thermal response of the shadowed member. Steps taken to identify shadowers, find locations where shadowing occurs and calculate shadow intensity are listed. The finite element thermal structural analysis of cable stiffened space structure is delineated and the exact solution of the caternary problem is given. Typical cable surface heating rates are plotted. The structural analysis includes large deformation (nonlinear), thermal effect, and the pretension effect. Displacements and stresses are computed at different orbital positions for an orbit.

Mahaney, J.↗
NASA NTRS2011

Multidisciplinary Modeling Software for Analysis, Design, and Optimization of HRRLS Vehicles

The concept for Highly Reliable Reusable Launch Systems (HRRLS) under the NASA Hypersonics project is a two-stage-to-orbit, horizontal-take-off / horizontal-landing, (HTHL) architecture with an air-breathing first stage. The first stage vehicle is a slender body with an air-breathing propulsion system that is highly integrated with the airframe. The light weight slender body will deflect significantly during flight. This global deflection affects the flow over the vehicle and into the engine and thus the loads and moments on the vehicle. High-fidelity multi-disciplinary analyses that accounts for these fluid-structures-thermal interactions are required to accurately predict the vehicle loads and resultant response. These predictions of vehicle response to multi physics loads, calculated with fluid-structural-thermal interaction, are required in order to optimize the vehicle design over its full operating range. This contract with ResearchSouth addresses one of the primary objectives of the Vehicle Technology Integration (VTI) discipline: the development of high-fidelity multi-disciplinary analysis and optimization methods and tools for HRRLS vehicles. The primary goal of this effort is the development of an integrated software system that can be used for full-vehicle optimization. This goal was accomplished by: 1) integrating the master code, FEMAP, into the multidiscipline software network to direct the coupling to assure accurate fluid-structure-thermal interaction solutions; 2) loosely-coupling the Euler flow solver FEFLO to the available and proven aeroelasticity and large deformation (FEAP) code; 3) providing a coupled Euler-boundary layer capability for rapid viscous flow simulation; 4) developing and implementing improved Euler/RANS algorithms into the FEFLO CFD code to provide accurate shock capturing, skin friction, and heat-transfer predictions for HRRLS vehicles in hypersonic flow, 5) performing a Reynolds-averaged Navier-Stokes computation on an HRRLS configuration; 6) integrating the RANS solver with the FEAP code for coupled fluid-structure-thermal capability; and 7) integrating the existing NASA SRGULL propulsion flow path prediction software with the FEFLO software for quasi-3D propulsion flow path predictions, 8) improving and integrating into the network, an existing adjoint-based design optimization code.

Spradley, Lawrence W.↗
NASA NTRSDate not supplied

X-57 Mod III Wing Ground Vibration Test

The X-57 “Maxwell” all-electric experimental aircraft was an electric propulsion demonstrator developed by the National Aeronautics and Space Administration to inform airworthiness standards for electrified aircraft. The development of the X-57 aircraft was separated into configuration modifications culminating in a distributed electric propulsion flight demonstrator named Modification IV (a.k.a., Mod IV). One of these configurations, the X-57 Mod III aircraft, involved flight-testing of a long, slender, high-aspect-ratio wing with two electric motors located at the wingtips. The X-57 Mod III wing ground vibration test was performed in the Flight Loads Laboratory at the National Aeronautics and Space Administration Armstrong Flight Research Center to measure the structural dynamics properties of the newly developed wing, and to confirm airworthiness of the Mod III/IV aircraft. This paper describes the testing performed to acquire the modal data and the subsequent results from the test.

Samson Truong↗
NASA NTRS1993

Transition on a sharp cone at high enthalpy - New measurements in the shock tunnel T5 at GALCIT

An exploratory study of the laminar, transitional and turbulent boundary layer on a slender cone in hypervelocity flow was conducted in the high-enthalpy shock tunnel T5. A novel flow visualization technique using sodium seeding to increase the sensitivity of conventional interferometric techniques by resonant enhancement of the refractivity of the medium was developed to study its structure. The experiments were designed to cover a large range of specific reservoir enthalpy, ranging from the perfect-gas region to the range where significant oxygen and some nitrogen dissociation and recombination effects may be expected in the boundary layer. Surface heat flux measurements indicate that the transition Reynolds number is approximately the same as that observed in cold hypersonic flow in conventional continuous flow facilities, but significantly lower than that observed in 'quiet' tunnels. No significant effect of reservoir specific enthalpy on transition was observed. The heat flux distribution showed differences between the air and the nitrogen experiments in the laminar regime. These are consistent with the presence of recombination of oxygen at the wall. This view is supported by the fact that this effect is absent in the low-enthalpy region, where the heat flux distribution agrees with the similarity theory.

Germain, P.↗
NASA NTRS1980

Post-buckling behavior of a beam-column on a nonlinear elastic foundation with a gap

The structural behavior of an elastic beam-column placed with a gap between two nonlinearity elastic layers each resting on a rigid foundation was examined. The beam-column was laterally supported at both ends and subjected to a uniform transverse load and axial compression. Its slenderness was such that the axial compressive force exceeds the amount that would be necessary to buckle it as a simple supported column. The elastic layers were represented by an elastic foundation with a strongly nonlinear specific reaction taken as a rapidly increasing function of the layer compression. The analytical model developed simulated the entire pattern of the deflection and stress state including layer and end support reactions, under gradually increasing axial force.

Kuznetsov, E. N.↗
NASA NTRS2016

System Level Aerothermal Testing for the Adaptive Deployable Entry and Placement Technology (ADEPT)

The Adaptive Deployable Entry and Placement Technology (ADEPT), a mechanically deployable entry vehicle technology, has been under development at NASA since 2011. As part of the technical maturation of ADEPT, designs capable of delivering small payloads (10 kg) are being considered to rapidly mature sub 1 m deployed diameter designs. The unique capability of ADEPT for small payloads comes from its ability to stow within a slender volume and deploy to achieve a mass efficient drag surface with a high heat rate capability. The low ballistic coefficient results in entry heating and mechanical loads that can be met by a revolutionary three-dimensionally woven carbon fabric supported by a deployable skeleton structure. This carbon fabric has test proven capability as both primary structure and payload thermal protection system. In order to rapidly advance ADEPTs technical maturation, the project is developing test methods that enable thermostructural design requirement verification of ADEPT designs at the system level using ground test facilities. Results from these tests are also relevant to larger class missions and help us define areas of focused component level testing in order to mature material and thermal response design codes. The ability to ground test sub 1 m diameter ADEPT configurations at or near full-scale provides significant value to the rapid maturation of this class of deployable entry vehicles. This paper will summarize arc jet test results, highlight design challenges, provide a summary of lessons learned and discuss future test approaches based upon this methodology.

Hypersonic↗
NASA NTRS2014

ADEPT for Secondary Payloads

Deployable entry vehicles provide an enabling capability for large payloads at destinations across the solar system. The primary advantage of such systems derives from the fundamental limitation of available launch vehicle shroads preventing tried-and-true rigid aeroshell technology from being applied. However, little mission-pull exists for deployable entry vehicle technology for missions where the entry vehicle is the primary payload and can fit within available shrouds. The propensity toward applying rigid aeroshell technology is logical given that deployable concepts are higher risk and provide no marginal scientific benefit for missions where a rigid aeroshell is an option. A movement toward flying smaller spacecraft has emerged in recent years and is revealing novel applications for deployable entry vehicles as secondary payloads. Secondary payloads must minimize interference with the primary payload in order to ease accomodation. Advancements in small spacecraft technology have caught the attention of government entities who are now recognizing the high value proposition of small spacecraft for frequent, incremental technology development and science return rather than the traditional high cost and infrequent big-bang approaches. Worldwide, well over 200 small satellites (mass < 180 kg) have launched in recent years for such purposes as eduation, technology development, science, commerce, and defense. The Adaptable Deployable Entry and Placement Technology (ADEPT), a mechanically-deployable entry vehicle technology, has been under development at NASA since 2011. An Ames Center Innovation Fund (CIF) proposal was recently awarded to study ADEPT for EDL of small payloads. The unique capability of ADEPT for small science payloads comes from its ability to stow within a slender volume and deploy passively to achieve a mass-efficient drag surface with a high heat rate capability. The low ballistic coefficient results in entry heating and mechanical loads that can be met by a revolutionary three-dimensionally woven carbon fabric supported with rib structures. This carbon fabric has test-proven capability as both primary structure and payload thermal protection. This presentation will inform the EDL community of the capability of ADEPT for delivery of small secondary payloads as well as provide status of on-going technology development activities. Results of a mission applications study for secondary payloads to Mars and Venus will be presented. A primary goal of these mission design activities is to integrate high-value verification approaches wherever possible. For example, for some mission applications it is possible to test in NASA arc jet facilities at full-scale. This enables endto- end thermostructural requirement verification with a single test. Another important challenge that needs to be solved is the reliability of the decelerator to achieve the desired shape using simple passive mechanical actuators (such as springs) that do not require power from the primary payload for deployment. A configuration of ADEPT is being prototyped and used to evaluate the functionality and reliability of the deployment mechanism through bench-top testing. The prototype will then be tested in a low speed wind tunnel in late 2014 to evaluate aerodynamic load-carrying capability and deflected shape. Results of the deployment testing and status of wind tunnel test plans will be discussed.

Smith, B.↗
NASA NTRS1976

Unsteady aerodynamic flow field analysis of the space shuttle configuration. Part 1: Orbiter aerodynamics

An analysis of the steady and unsteady aerodynamics of the space shuttle orbiter has been performed. It is shown that slender wing theory can be modified to account for the effect of Mach number and leading edge roundness on both attached and separated flow loads. The orbiter unsteady aerodynamics can be computed by defining two equivalent slender wings, one for attached flow loads and another for the vortex-induced loads. It is found that the orbiter is in the transonic speed region subject to vortex-shock-boundary layer interactions that cause highly nonlinear or discontinuous load changes which can endanger the structural integrity of the orbiter wing and possibly cause snap roll problems. It is presently impossible to simulate these interactions in a wind tunnel test even in the static case. Thus, a well planned combined analytic and experimental approach is needed to solve the problem.

Ericsson, L. E.↗
NASA NTRS1984

Space structure vibration modes: How many exist? Which ones are important?

This report attempts to shed some light on the two issues raised in the title, namely, how many vibration modes does a real structure have, and which of these modes are important? The surprise-free answers to these two questions are, respectively, an infinite number and the first several modes. The author argues that the absurd subspace (all but the first billion modes) is not a strength of continuum modeling, but, in fact, a weakness. Partial differential equations are not real structures, only mathematical models. This note also explains (1) that the PDE model and the finite element model are, in fact, the same model, the latter being a numerical method for dealing with the former, (2) that modes may be selected on dynamical grounds other than frequency alone, and (3) that long slender rods are useful as primitive cases but dangerous to extrapolate from.

Hughes, P. C.↗
NASA NTRS1978

Dynamics of a flexible body in orbit

The equations of motion of an arbitrary flexible body in orbit are derived. The model includes the effects of gravity with all its higher harmonics. As a specific example, the motion of a long, slender, uniform beam in circular orbit is modeled. The example considers the inplane motion of the beam in orbit. In the case of planar motion with only flexural vibrations, the pitch motion is not influenced by the elastic motion of the beam. For large values of the square of the ratio of the structural modal frequency to the orbital angular rate the elastic motion is decoupled from the pitch motion. However, for small values of this ratio and small amplitude pitch motion, the elastic motion is governed by a Hill's 3-term equation. Numerical simulation of this equation indicates the possibilities of instability for very low values of the square of the ratio of the modal frequency to the orbit angular rate.

Kumar, V. K.↗
NASA NTRS1984

Simple theoretical models for composite rotor blades

The development of theoretical rotor blade structural models for designs based upon composite construction is discussed. Care was exercised to include a member of nonclassical effects that previous experience indicated would be potentially important to account for. A model, representative of the size of a main rotor blade, is analyzed in order to assess the importance of various influences. The findings of this model study suggest that for the slenderness and closed cell construction considered, the refinements are of little importance and a classical type theory is adequate. The potential of elastic tailoring is dramatically demonstrated, so the generality of arbitrary ply layup in the cell wall is needed to exploit this opportunity.

Valisetty, R. R.↗
NASA NTRS1996

Buckling and Postbuckling Behavior of Laminated Composite Plates With a Cutout

This paper addresses the effects of a cutout on the buckling and postbuckling behavior of rectangular plates made of advanced composite materials. An overview of past research is presented, and several key findings and behavioral characteristics are discussed. These findings include the effects of cutout size, shape, eccentricity, and orientation; plate aspect and slenderness ratios; loading and boundary conditions; and plate orthotropy and anisotropy. Some overall important findings of these studies are that plates that have a cutout can buckle at loads higher than the buckling loads for corresponding plates without a cutout and can exhibit substantial postbuckling load-carrying capability. In addition, laminate construction, coupled with cutout geometry, offers a viable means for tailoring structural response.

Nemeth, Michael P.↗
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 NTRS1980

Effect of orbital transfer loads on large platforms

A preliminary automated structural sizing procedure suitable for conceptual design and early tradeoff studies of large truss platforms configured for shuttle transportation to LEO is discussed as well as some orbital transfer design considerations. Platforms that are sized to withstand orbital transfer loads for the LEO to GEO maneuver are compared to platforms sized only for LEO application. It is concluded that for platforms supporting low mass distributed payloads, platform and strut frequency requirements are strong design drivers for LEO applications. The struts are found to be extremely slender, thinswalled, and of small diameter. If full advantage is to be taken of these minimum mass designs, a manufacturing capability must be developed for long straight struts. For platforms that are to be transferred from LEO to GEO in a deployed state, the orbital transfer loads become design drivers. However, even for an initial thrust-to-weight ratio equal to 0.1, a platform on the order of 100 m diameter appears packageable with its OTV in one shuttle flight, and larger platforms appear possible at lower thrust-to-weight ratios.

Walz, J. E.↗
NASA NTRS1984

Radar response from vegetation with nodal structure

Radar images from the SEASAT synthetic aperture radar (SAR) produced unusually high returns from corn and sorghum fields, which seem to indicate a correlation between nodal separation in the stalk and the wavelength of the radar. These images also show no difference in return from standing or harvested corn. Further investigation using images from the Shuttle Imaging Radar (SIR-A) substantiated these observations and showed a degradation of the high return with time after harvest. From portions of corn and sweet sorghum stalks that were sampled to measure stalk water content, it was determined that near and after maturity the water becomes more concentrated in the stalk nodes. The stalk then becomes a linear sequence of alternating dielectrics as opposed to a long slender cylinder with uniform dielectric properties.

Blanchard, B. J.↗
NASA NTRS1991

Investigation of vortex development on a pitching slender body of revolution

A computational study of the unsteady flow about a pitching 3.5 caliber tangent ogive forebody is presented. The flow is simulated using the full 3D unsteady Navier-Stokes equations and a time-accurate implicit algorithm. Comparison to available experimental data for a steady 20 deg case is presented as validation. Effects of grid resolution and a comparison of solutions using full Navier-Stokes and the thin-layer approximation are included. The forebody is simulated in a 'pitch-up to 20 deg and hold' maneuver, and two different pitch axis locations are used in the study. Examination of the unsteady vorticity field for the pitch-up cases reveals the formation of strong shear layers as the body decelerates, and their roll-up into vortical structures in a process similar to that observed in airfoil dynamic stall. Pronounced vortex/surface interactions are seen which produce multiple secondary separation regions, ejection of vorticity from the surface, and embedded regions of high suction.

Stanek, M. J.↗
NASA NTRS1975

ISOFINEL: Isoparametric finite element code for elastic analysis of two-dimensional bodies

A formulation is presented for the development of a finite element program for the elastic analysis of two-dimensional bodies using the eight-node isoparametric quadrilateral. The program solves for both plane stress and plane strain problems. The finite element formulation based on the isoparametric displacement functions is presented. The program structure is given in the form of flow diagrams with descriptions of the numerical procedure used to obtain the element stiffness matrix, and the solution method employed to solve for nodal displacements. Three numerical examples (a plate under uniaxial tension, a plate under pure shear, and a beam under pure bending) are presented to illustrate the capability and limitations of the element implementation. The first problem is solved exactly by the element, as predicted by the form of its displacement functions. In the other two problems the accuracy of the solution is highly dependent upon the slenderness of the element, the number of elements in the map, and the numerical integration scheme used to build the element stiffness matrix.

Marino, C.↗
NASA NTRS1984

Usefulness of multifrequency MST radar measurements, part 2.6B

Scattering of radio waves from atmospheric refractive-index irregularities induced by turbulence was invoked almost four decades ago to explain the characteristics of signals received on VHF/UHF ionospheric and tropospheric forward-scatter links. Due to the bistatic geometry of these links a slender, horizontally extended, common volume or cell is formed in space. The principal contribution to scattering arises from refractive-index fluctuations in this volume at the Bragg wave number K approx. sub B = K approx. sub i -k approx. sub s vectors. It has been surmised that the use of more than one frequency in probing the middle-atmosphere regions should help resolve several issues pertaining to the scattering mechanism. These issues are briefly re-examined in this note. The implications of the radar equation are discussed. The problems arising due to layered structure of turbulence and the choice of frequencies most suitable for multifrequency measurements are considered.

Rastogi, P. K.↗