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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Carbon composites in space vehicle structures

Recent developments in the technology of carbon or graphite filaments now provide the designer with greatly improved materials offering high specific strength and modulus. Besides these advantages are properties which are distinctly useful for space applications and which provide feasibility for missions not obtainable by other means. Current applications include major and secondary structures of communications satellites. A number of R & D projects are exploring carbon-fiber application to rocket engine motor cases, advanced antenna systems, and space shuttle components. Future system studies are being made, based on the successful application of carbon fibers for orbiting space telescope assemblies, orbital transfer vehicles, and very large deployable energy generation systems. Continued technology development is needed in analysis, material standards, and advanced structural concepts to exploit the full potential of carbon filaments in composite materials.

Mayer, N. J.↗
NASA NTRS1995

Vibroacoustic Response of Pad Structures to Space Shuttle Launch Acoustic Loads

This paper presents a deterministic theory for the random vibration problem for predicting the response of structures in the low-frequency range (0 to 20 hertz) of launch transients. Also presented are some innovative ways to characterize noise and highlights of ongoing test-analysis correlation efforts titled the Verification Test Article (VETA) project.

Margasahayam, R. N.↗
NASA NTRS1992

Sensor filter designs for large flexible spacecraft

Traditional control methods may excite flexible modes causing degraded performance or instability of large flexible space structures (LFSS). Control techniques developed for control of LFSS requires a numerical model of the structure and some knowledge of model error. This will be increasingly difficult with the complex space structures planned for the future. If filters could be used to condition the sensor output, control design would be less demanding. This paper is presented in viewgraph format.

Nimmo, Nancy A.↗
NASA NTRS2004

Analytical and Experimental Characterization of Gravity Induced Deformations In Subscale Gossamer Structures

The development of gossamer space structures such as solar sails and sunshields presents many challenges due to their large size and extreme flexibility. The post-deployment structural geometry exhibited during ground testing may significantly depart from the in-space configuration due to the presence of gravity-induced deformations (gravity sag) of lightly preloaded membranes. This paper describes a study carried out to characterize gravity sag in two subscale gossamer structures: a single quadrant from a 2 m, 4 quadrant square solar sail and a 1.7 m membrane layer from a multi-layer sunshield The behavior of the test articles was studied over a range of preloads and in several orientations with respect to gravity. An experimental study was carried out to measure the global surface profiles using photogrammetry, and nonlinear finite element analysis was used to predict the behavior of the test articles. Comparison of measured and predicted surface profiles shows that the finite dement analysis qualitatively predicts deformed shapes comparable to those observed in the laboratory. Quantitatively, finite element analysis predictions for peak gravity-induced deformations in both test articles were within 10% of measured values. Results from this study provide increased insight into gravity sag behavior in gossamer structures, and demonstrates the potential to analytically predict gravity-induced deformations to within reasonable accuracy.

Johnston, John D.↗
NASA NTRS1990

Measurement of structure motion by means of a moving light sheet

The elaboration of an optical system which measures the displacement and velocity of large flexible space structures is reviewed. The motion-measuring system, comprised of a laser, optics, motorized mirror, two photodiodes and electronics, is designed to allow feedback for configuration control of flexible structures. A motor or scanner is employed to sweep the light sheet. The range of motion was shown to be 2 inches, and information was received at a rate of 30 Hz. The uncertainty in displacement measurement was better than +0.01 inch from a distance of 16 feet. The results are considered to be very good for two scanning light sheet systems. Higher sample rates and a more constant speed would improve the rotating mirror option, and the accuracy and range of the scanning mirror option could be upgraded as well. Both setups are shown to be viable noncontact measuring methods for the displacement and velocity of large space structures.

Tcheng, Ping↗
NASA NTRS1994

Composite Load Spectra for Select Space Propulsion Structural Components

Generic load models are described with multiple levels of progressive sophistication to simulate the composite (combined) load spectra (CLS) that are induced in space propulsion system components, representative of Space Shuttle Main Engines (SSME), such as transfer ducts, turbine blades and liquid oxygen (LOX) posts. These generic (coupled) models combine the deterministic models for composite load dynamic, acoustic, high-pressure and high rotational speed, etc., load simulation using statistically varying coefficients. These coefficients are then determined using advanced probabilistic simulation methods with and without strategically selected experimental data. The entire simulation process is included in a CLS computer code. Applications of the computer code to various components in conjunction with the PSAM (Probabilistic Structural Analysis Method) to perform probabilistic load evaluation and life prediction evaluations are also described to illustrate the effectiveness of the coupled model approach.

Ho, Hing W.↗
NASA NTRS1987

Composite load spectra for select space propulsion structural components

The objective of this program is to develop generic load models to simulate the composite load spectra (CLS) that are induced in space propulsion system components representative of the space shuttle main engines (SSME). These models are being developed through describing individual component loads with an appropriate mix of deterministic and state-of-the-art probabilistic models that are related to key generic variables. Combinations of the individual loads are used to synthesize the composite loads spectra. A second approach for developing the composite loads spectra load model simulation, the option portion of the contract will develop coupled models which combine the individual load models. Statistically varying coefficients of the physical models will be used to obtain the composite load spectra.

Newell, J. F.↗
NASA NTRS1989

Composite load spectra for select space propulsion structural components

The objective of the Composite Load Spectra (CLS) project is to build a knowledge based system to synthesize probabilistic loads for selected space propulsion engine components. The knowledge based system has a load expert system module and a load calculation module. The load expert system provides load information and the load calculation module generates the probabilistic load distributions. The engine loads are divided into 4 broad classes: the engine independent loads, the engine system dependent load, the component local independent loads and the component loads. These classes are defined and illustrated.

Ho, H.↗
NASA NTRS1991

Methods for evaluating the predictive accuracy of structural dynamic models

Modeling uncertainty is defined in terms of the difference between predicted and measured eigenvalues and eigenvectors. Data compiled from 22 sets of analysis/test results was used to create statistical databases for large truss-type space structures and both pretest and posttest models of conventional satellite-type space structures. Modeling uncertainty is propagated through the model to produce intervals of uncertainty on frequency response functions, both amplitude and phase. This methodology was used successfully to evaluate the predictive accuracy of several structures, including the NASA CSI Evolutionary Structure tested at Langley Research Center. Test measurements for this structure were within + one-sigma intervals of predicted accuracy for the most part, demonstrating the validity of the methodology and computer code.

Hasselman, Timothy K.↗
DOE OSTI2013

Ternary rare-earth ruthenium and iridium germanides RE{sub 3}M{sub 2}Ge{sub 3} (RE=Y, Gd–Tm, Lu; M=Ru, Ir)

Through arc-melting reactions of the elements and annealing at 800 °C, the ternary rare-earth germanides RE{sub 3}Ru{sub 2}Ge{sub 3} and RE{sub 3}Ir{sub 2}Ge{sub 3} have been prepared for most of the smaller RE components (RE=Y, Gd–Tm, Lu). In the iridium-containing reactions, the new phases RE{sub 2}IrGe{sub 2} were also generally formed as by-products. Powder X-ray diffraction revealed orthorhombic Hf{sub 3}Ni{sub 2}Si{sub 3}-type structures (space group Cmcm, Z=4) for RE{sub 3}M{sub 2}Ge{sub 3} (M=Ru, Ir) and monoclinic Sc{sub 2}CoSi{sub 2}-type structures (space group C2/m, Z=4) for RE{sub 2}IrGe{sub 2}. Full crystal structures were determined by single-crystal X-ray diffraction for all members of RE{sub 3}Ru{sub 2}Ge{sub 3} (a=4.2477(6) Å, b=10.7672(16) Å, c=13.894(2) Å for RE=Y; a=4.2610(3)–4.2045(8) Å, b=10.9103(8)–10.561(2) Å, c=14.0263(10)–13.639(3) Å in the progression of RE from Gd to Lu) and for Tb{sub 3}Ir{sub 2}Ge{sub 3} (a=4.2937(3) Å, b=10.4868(7) Å, c=14.2373(10) Å). Both structures can be described in terms of CrB- and ThCr{sub 2}Si{sub 2}-type slabs built from Ge-centred trigonal prisms. However, band structure calculations on Y{sub 3}Ru{sub 2}Ge{sub 3} support an alternative description for RE{sub 3}M{sub 2}Ge{sub 3} based on [M{sub 2}Ge{sub 3}] layers built from linked MGe{sub 4} tetrahedra, which emphasizes the strong M–Ge covalent bonds present. The temperature dependence of the electrical resistivity of RE{sub 3}Ru{sub 2}Ge{sub 3} generally indicates metallic behaviour but with low-temperature transitions visible for some members (RE=Gd, Tb, Dy) that are probably associated with magnetic ordering of the RE atoms. Anomalously, Y{sub 3}Ru{sub 2}Ge{sub 3} exhibits semiconductor-like behaviour of uncertain origin. Magnetic measurements on Dy{sub 3}Ru{sub 2}Ge{sub 3} reveal antiferromagnetic ordering at 3 K and several unusual field-dependent transitions suggestive of complex spin reorientation processes. - Graphical abstract: RE{sub 3}M{sub 2}Ge{sub 3} (M=Ru, Ir) adopts the Hf{sub 3}Ni{sub 2}Si{sub 3}-type structure containing slabs built up from Ge-centred trigonal prisms. - Highlights: • Crystal structures of RE{sub 3}Ru{sub 2}Ge{sub 3} (RE=Y, Gd–Tm, Lu) and Tb{sub 3}Ir{sub 2}Ge{sub 3} were determined. • Strong M–Ge covalent bonds were confirmed by band structure calculations. • Most RE{sub 3}Ru{sub 2}Ge{sub 3} members except Y{sub 3}Ru{sub 2}Ge{sub 3} exhibit metallic behaviour. • Dy{sub 3}Ru{sub 2}Ge{sub 3} displays unusual field-dependent magnetic transitions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1990

Spacecraft dynamics characterization and control system failure detection

Two important aspects of the control of large space structures are studied: the modeling of deployed or erected structures including nonlinear joint characteristics; and the detection and isolation of failures of the components of control systems for large space structures. The emphasis in the first task is on efficient representation of the dynamics of large and complex structures having a great many joints. The initial emphasis in the second task is on experimental evaluation of FDI methodologies using ground-based facilities in place at NASA Langley Research Center and Marshall Space Flight Center. The progress to date on both research tasks is summarized.

Vandervelde, Wallace E.↗
DOE OSTI2012

Crystal growth and physical properties of SrCu 2 As 2 , SrCu 2 Sb 2 , and BaCu 2 Sb 2

Here we report the growth of single crystals of SrCu 2 As 2 , SrCu 2 Sb 2 , SrCu 2 (As 0.84 Sb 0.16 ) 2 , and BaCu 2 Sb 2 using the self-flux technique and their structural, magnetic, thermal, and transport properties that were investigated by powder x-ray diffraction (XRD), magnetic susceptibility χ, specific heat Cp, and electrical resistivity ρ measurements versus temperature T from 1.8 to 350 K. Rietveld refinements of XRD patterns for crushed crystals confirm that SrCu 2 As 2 crystallizes in the ThCr 2 Si 2 -type body-centered tetragonal structure (space group I4/mmm) and SrCu 2 Sb 2 crystallizes in the CaBe 2 Ge 2 -type primitive tetragonal structure (space group P4/nmm). However, as reported previously, BaCu 2 Sb 2 is found to have a large unit cell consisting of three blocks. Here a ThCr 2 Si 2 -type block is sandwiched between two CaBe 2 Ge 2 -type blocks along the c axis with an overall symmetry of I4/mmm, as reported, but likely with a monoclinic distortion. The χ data of all these compounds are diamagnetic and reveal nearly T-independent anisotropic behavior. The χ of SrCu 2 As 2 is found to be larger in the ab plane than along the c axis, as also previously reported for pure and doped BaFe 2 As 2 , whereas the χ values of SrCu 2 Sb 2 and BaCu 2 Sb 2 are larger along the c axis. This difference in anisotropy appears to arise from the differences between the crystal structures. The finite values of the Sommerfeld linear specific heat coefficients γ and the T dependences of ρ reveal metallic character of all four compounds. The electronic and magnetic properties indicate that these compounds are sp metals with Cu in the nonmagnetic 3d 10 electronic configuration corresponding to the oxidation state Cu +1 , as previously predicted theoretically for SrCu 2 As 2 by Singh. We present a brief review of theoretical and experimental work on the doping character of transition metals for Fe in BaFe 2 As 2 . The As–As covalent interlayer bond distances in the collapsed-tetragonal (Ca,Sr,Ba)Cu 2 As 2 compounds are much shorter than the nonbonding As–As distances in BaFe 2 As 2 . Thus, the electronic character of the Cu and the strength of the As–As interlayer bonding are both expected to drastically change between weakly Cu-substituted BaFe 2 As 2 and pure BaCu 2 As 2 , perhaps via a first-order lattice instability such as a miscibility gap in the Ba(Fe 1-x Cu x ) 2 As 2 system.

36 MATERIALS SCIENCE↗
NASA NTRS1984

Identification and control of structures in space

The derivation of the equations of motion for the Spacecraft Control Laboratory Experiment (SCOLE) is reported and the equations of motion of a similar structure orbiting the earth are also derived. The structure is assumed to undergo large rigid-body maneuvers and small elastic deformations. A perturbation approach is proposed whereby the quantities defining the rigid-body maneuver are assumed to be relatively large, with the elastic deformations and deviations from the rigid-body maneuver being relatively small. The perturbation equations have the form of linear equations with time-dependent coefficients. An active control technique can then be formulated to permit maneuvering of the spacecraft and simultaneously suppressing the elastic vibration.

Meirovitch, L.↗
NASA NTRSDate not supplied

Modeling Effort of TriTruss Modular Structure for In-Space Assembled Telescope Foundational Structure

The TriTruss is a novel and innovative structural module developed by researchers at the NASA Langley Research Center to construct modular structures which can be assembled on-orbit for future persistent missions, including in-space assembled telescopes and platforms for science and communications. The TriTruss offers unique modular structural features including compact packaging for launch, the possibility of staged packaging, simple robotic deployment and assembly, and design versatility for specific space mission applications. This paper presents the modeling and analysis procedure for the TriTruss modular structure and the predicted frequency response of an In-Space Assembled Telescope’s (iSAT) primary reflector.

Structural Modeling↗
DOE OSTI2015

Antiferromagnetism in EuCu 2 As 2 and EuCu 1.82 Sb 2 single crystals

Single crystals of EuCu 2 As 2 and EuCu 2 Sb 2 were grown from CuAs and CuSb self-flux, respectively. The crystallographic, magnetic, thermal, and electronic transport properties of the single crystals were investigated by room-temperature x-ray diffraction (XRD), magnetic susceptibility χ versus temperature T, isothermal magnetization M versus magnetic field H, specific heat C p (T), and electrical resistivity ρ(T) measurements. EuCu 2 As 2 crystallizes in the body-centered tetragonal ThCr 2 Si 2 -type structure (space group I4/mmm), whereas EuCu 2 Sb 2 crystallizes in the related primitive tetragonal CaBe 2 Ge 2 -type structure (space group P4/nmm). The energy-dispersive x-ray spectroscopy and XRD data for the EuCu 2 Sb 2 crystals showed the presence of vacancies on the Cu sites, yielding the actual composition EuCu 1.82 Sb 2 . The ρ(T) and C p (T) data reveal metallic character for both EuCu 2 As 2 and EuCu 1.82 Sb 2 . Antiferromagnetic (AFM) ordering is indicated from the χ(T),C p (T), and ρ(T) data for both EuCu 2 As 2 (T N = 17.5 K) and EuCu 1.82 Sb 2 (T N = 5.1 K). In EuCu 1.82 Sb 2 , the ordered-state χ(T) and M(H) data suggest either a collinear A-type AFM ordering of Eu +2 spins S = 7/2 or a planar noncollinear AFM structure, with the ordered moments oriented in the tetragonal ab plane in either case. This ordered-moment orientation for the A-type AFM is consistent with calculations with magnetic dipole interactions. As a result, the anisotropic χ(T) and isothermal M(H) data for EuCu 2 As 2 , also containing Eu +2 spins S = 7/2, strongly deviate from the predictions of molecular field theory for collinear AFM ordering and the AFM structure appears to be both noncollinear and noncoplanar.

36 MATERIALS SCIENCE↗
NASA NTRS2002

Photogrammetry Methodology Development for Gossamer Spacecraft Structures

Photogrammetry--the science of calculating 3D object coordinates from images-is a flexible and robust approach for measuring the static and dynamic characteristics of future ultralightweight and inflatable space structures (a.k.a., Gossamer structures), such as large membrane reflectors, solar sails, and thin-film solar arrays. Shape and dynamic measurements are required to validate new structural modeling techniques and corresponding analytical models for these unconventional systems. This paper summarizes experiences at NASA Langley Research Center over the past three years to develop or adapt photogrammetry methods for the specific problem of measuring Gossamer space structures. Turnkey industrial photogrammetry systems were not considered a cost-effective choice for this basic research effort because of their high purchase and maintenance costs. Instead, this research uses mainly off-the-shelf digital-camera and software technologies that are affordable to most organizations and provide acceptable accuracy.

Pappa, Richard S.↗
NASA NTRS1985

Space station rotational equations of motion

Dynamic equations of motion are developed which describe the rotational motion for a large space structure having rotating appendages. The presence of the appendages produce torque coupling terms which are dependent on the inertia properties of the appendages and the rotational rates for both the space structure and the appendages. These equations were formulated to incorporate into the Space Station Attitude Control and Stabilization Test Bed to accurately describe the influence rotating solar arrays and thermal radiators have on the dynamic behavior of the Space Station.

Rheinfurth, M. H.↗