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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Crystal Lattice Controlled SiGe Thermoelectric Materials with High Figure of Merit

Direct energy conversion between thermal and electrical energy, based on thermoelectric (TE) effect, has the potential to recover waste heat and convert it to provide clean electric power. The energy conversion efficiency is related to the thermoelectric figure of merit ZT expressed as ZT=S(exp 2)(sigma)T/Kappa, T is temperature, S is the Seebeck coefficient, sigma is conductance and Kappa is thermal conductivity. For a lower thermal conductivity Kappa and high power factor (S(exp 2)(sigma)), our current strategy is the development of rhombohedrally strained single crystalline SiGe materials that are highly [111]-oriented twinned. The development of a SiGe "twin lattice structure (TLS)" plays a key role in phonon scattering. The TLS increases the electrical conductivity and decreases thermal conductivity due to phonon scattering at stacking faults generated from the 60 X rotated primary twin structure. To develop high performance materials, the substrate temperature, chamber working pressure, and DC sputtering power are controlled for the aligned growth production of SiGe layer and TLS on a c-plane sapphire. Additionally, a new elevated temperature thermoelectric characterization system, that measures the thermal diffusivity and Seebeck effect nondestructively, was developed. The material properties were characterized at various temperatures and optimized process conditions were experimentally determined. The present paper encompasses the technical discussions toward the development of thermoelectric materials and the measurement techniques.

Kim, Hyun-Jung↗
NASA NTRS1977

Leading edge protection for composite blades

A laminated filament composite structure, such as an airfoil for use in an environment in which it is subjected to both foreign object impact and bending is provided with improved leading edge protection. At least one fine wire mesh layer is partially bonded within the composite structure along its neutral bending axis. A portion of the wire mesh layer extends beyond the neutral bending axis and partially around the leading edge where it is bonded to the outer periphery of the primary composite structure. The wire mesh is clad with a metal such as nickel to provide an improved leading edge protective device which is firmly anchored within the composite structure. Also described is a novel method of constructing a composite airfoil so as to further minimize the possibility of losing the leading edge protective device due to delamination caused by impact and bending.

Brantley, J. W.↗
NASA NTRS1979

The NASA Aircraft Energy Efficiency program

A review is provided of the goals, objectives, and recent progress in each of six aircraft energy efficiency programs aimed at improved propulsive, aerodynamic and structural efficiency for future transport aircraft. Attention is given to engine component improvement, an energy efficient turbofan engine, advanced turboprops, revolutionary gains in aerodynamic efficiency for aircraft of the late 1990s, laminar flow control, and composite primary aircraft structures.

Klineberg, J. M.↗
NASA NTRS1972

Testing for hydrogen embrittlement: Primary and secondary influences

An overview is presented of the hydrogen embrittlement process, both internal as well as external, to make more clear the type of parameters which must be considered in the selection of a test method and test procedure, so that the resulting data may be meaningfully applied to real engineering structures. Three primary influences on the embrittlement process are considered: (1) the original location and form of the hydrogen, (2) the transport reactions involved in the transport of hydrogen from its origin to some point where it can interact with the metal to cause embrittlement, and (3) the embrittlement interaction itself. A few secondary influences on the embrittlement process are also discussed.

Nelson, H. G.↗
NASA NTRS2014

Optimization of a Lunar Pallet Lander Reinforcement Structure Using a Genetic Algorithm

In this paper, a unique system level spacecraft design optimization will be presented. A Genetic Algorithm is used to design the global pattern of the reinforcing structure, while a gradient routine is used to adequately stiffen the sub-structure. The system level structural design includes determining the optimal physical location (and number) of reinforcing beams of a lunar pallet lander deck structure. Design of the substructure includes determining placement of secondary stiffeners and the number of rivets required for assembly.. In this optimization, several considerations are taken into account. The primary objective was to raise the primary natural frequencies of the structure such that the Pallet Lander primary structure does not significantly couple with the launch vehicle. A secondary objective is to determine how to properly stiffen the reinforcing beams so that the beam web resists the shear buckling load imparted by the spacecraft components mounted to the pallet lander deck during launch and landing. A third objective is that the calculated stress does not exceed the allowable strength of the material. These design requirements must be met while, minimizing the overall mass of the spacecraft. The final paper will discuss how the optimization was implemented as well as the results. While driven by optimization algorithms, the primary purpose of this effort was to demonstrate the capability of genetic algorithms to enable design automation in the preliminary design cycle. By developing a routine that can automatically generate designs through the use of Finite Element Analysis, considerable design efficiencies, both in time and overall product, can be obtained over more traditional brute force design methods.

Burt, Adam↗
NASA NTRS1982

Composite structural materials

The promise of filamentary composite materials, whose development may be considered as entering its second generation, continues to generate intense interest and applications activity. Fiber reinforced composite materials offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been achieved since the initial developments in the mid 1960's. Rather limited applications to primary aircraft structure have been made, however, mainly in a material-substitution mode on military aircraft, except for a few experiments currently underway on large passenger airplanes in commercial operation. To fulfill the promise of composite materials completely requires a strong technology base. NASA and AFOSR recognize the present state of the art to be such that to fully exploit composites in sophisticated aerospace structures, the technology base must be improved. This, in turn, calls for expanding fundamental knowledge and the means by which it can be successfully applied in design and manufacture.

Ansell, G. S.↗
NASA NTRS1978

A study on the utilization of advanced composites in commercial aircraft wing structure: Executive summary

The overall wing study objectives are to study and plan the effort by commercial transport aircraft manufacturers to accomplish the transition from current conventional materials and practices to extensive use of advanced composites in wings of aircraft that will enter service in the 1985-1990 time period. Specific wing study objectives are to define the technology and data needed to support an aircraft manufacturer's commitment to utilize composites primary wing structure in future production aircraft and to develop plans for a composite wing technology program which will provide the needed technology and data.

Watts, D. J.↗
NASA NTRS2014

OCCAMS: Optically Controlled and Corrected Active Meta-Material Space Structures

Telescopes require sub-wavelength figure (shape) error in order to achieve acceptable Strehl ratios. Traditional methods of achieving this require rigid and therefore heavy mirrors and reaction structures as well as proportionally heavy and expensive spacecraft busses and launch vehicles. This effectively limits the diameter and therefore resolution and collecting area of space optics. Large diameter telescopes must either be heavy or actively controlled. Space telescopes of the size proposed for missions such as TPF (Terrestrial Planet Finder), TPI (Terrestrial Planet Imager), etc. will likely require large active primaries and structures and corrective optics to implement downstream wavefront control. We propose a novel viable enabling technology. High resolution space imaging requires the production of lightweight large aperture optics subject to design tradespace constraints based on nanometer physical tolerances, low system aerial density, high control authority, suitable thermal and mechanical properties, deployment capability, launch vehicle volume constraints, as well as production cost and schedule risk mitigation. Segmented systems impose additional requirements on segment alignment, wavefront phasing, and telescope mass with increased edge diffraction. Photons weigh nothing. Why must even small space telescopes "weigh" tons? Our team is working to demonstrate that they do not, by leveraging 15 years of effort and a novel advanced concept.The ultimate research goal is to refine technology to produce a mission capable ultra-lightweight membrane optic whose shape can be remotely controlled using a laser beam. Using our novel optically-controlled molecular actuators allows substitution of optically-induced control for rigidity and mirror mass. In analogy with noise-canceling headphones, this technique also potentially provides a way to excite vibratory modes to couple with and damp out normal modes of oscillation induced by slewing, other motion and thermal changes, thus allowing a robust response to repointing of a large aperture.

Astronomy↗
NASA NTRS1977

Shuttle Experimental Radar for Geological Exploration (SERGE); antenna and integration concept definition study

The baseline configuration defined has the SERGE antenna panel array mounted on the OFT-2 pallet sufficiently high in the bay that negligible amounts of radiation from the beam are reflected from orbiter surfaces into the shuttle payload bay. The array is symmetrically mounted to the pallet along the array long dimension with the pallet at the center. It utilizes a graphite epoxy trusswork support structure. The antenna panels are of SEASAT engineering model design and construction. The antenna array has 7 panels and a 7-way naturally tapered coax corporate feed system. The performance of the system is predicted to exceed 33 db gain, have -15 db sidelobes in the E-plane and even lower in the H-plane, and have and E-plane beamwidth less than 2.2 deg, all within performance specification. The primary support structure is predicted to exceed the specified greater than 25 hertz fundamental frequency, although individual panels will have hertz fundamental frequency.

Kierein, J. W.↗
NASA NTRS1983

Design and analysis of composite structures with stress concentrations

An overview of an analytic procedure which can be used to provide comprehensive stress and strength analysis of composite structures with stress concentrations is given. The methodology provides designer/analysts with a user-oriented procedure which, within acceptable engineering accuracy, accounts for the effects of a wide range of application design variables. The procedure permits the strength of arbitrary laminate constructions under general bearing/bypass load conditions to be predicted with only unnotched unidirectional strength and stiffness input data required. Included is a brief discussion of the relevancy of this analysis to the design of primary aircraft structure; an overview of the analytic procedure with theory/test correlations; and an example of the use and interaction of this strength analysis relative to the design of high-load transfer bolted composite joints.

Garbo, S. P.↗
NASA NTRS1973

Service evaluation of aircraft composite structural components

The advantages of the use of composite materials in structural applications have been identified in numerous engineering studies. Technology development programs are underway to correct known deficiencies and to provide needed improvements. However, in the final analysis, flight service programs are necessary to develop broader acceptance of, and confidence in, any new class of materials such as composites. Such flight programs, initiated by NASA Langley Research Center, are reviewed. These programs which include the selectively reinforced metal and the all-composite concepts applied to both secondary and primary aircraft structural components, are described and current status is indicated.

Brooks, W. A., Jr.↗
NASA NTRS1973

Service evaluation of aircraft composite structural components

The advantages of the use of composite materials in structural applications have been identified in numerous engineering studies. Technology development programs are underway to correct known deficiencies and to provide needed improvements. However, in the final analysis, flight service programs are necessary to develop broader acceptance of, and confidence in, any new class of materials such as composites. Such flight programs, initiated by NASA Langley Research Center, will be reviewed in the proposed paper. These programs, which include the selectively reinforced metal and the all-composite concepts applied to both secondary and primary aircraft structural components, will be described and current status will be indicated.

Brooks, W. A., Jr.↗
NASA NTRS1991

RTM: Cost-effective processing of composite structures

Resin transfer molding (RTM) is a promising method for cost effective fabrication of high strength, low weight composite structures from textile preforms. In this process, dry fibers are placed in a mold, resin is introduced either by vacuum infusion or pressure, and the part is cured. RTM has been used in many industries, including automotive, recreation, and aerospace. Each of the industries has different requirements of material strength, weight, reliability, environmental resistance, cost, and production rate. These requirements drive the selection of fibers and resins, fiber volume fractions, fiber orientations, mold design, and processing equipment. Research is made into applying RTM to primary aircraft structures which require high strength and stiffness at low density. The material requirements are discussed of various industries, along with methods of orienting and distributing fibers, mold configurations, and processing parameters. Processing and material parameters such as resin viscosity, perform compaction and permeability, and tool design concepts are discussed. Experimental methods to measure preform compaction and permeability are presented.

Hasko, Greg↗
NASA NTRS2016

Fabricating with Crystalline Si to Improve Superconducting Detector Performance

We built and measured radio-frequency (RF) loss tangent, tan δ, evaluation structures using float-zone quality silicon-on-insulator (SOI) wafers with 5 μm thick device layers. Superconducting Nb components were fabricated on both sides of the SOI Si device layer. Our main goals were to develop a robust fabrication for using crystalline Si (c-Si) dielectric layers with superconducting Nb components in a wafer bonding process and to confirm that tan δ with c-Si dielectric layers was reduced at RF frequencies compared to devices fabricated with amorphous dielectrics, such as SiO2 and SixNy, where tan δ ~ 10(exp -3). Our primary test structure used a Nb coplanar waveguide (CPW) readout structure capacitively coupled to LC resonators, where the capacitors were defined as parallel-plate capacitors on both sides of a c-Si device layer using a wafer bonding process with benzocyclobutene (BCB) wafer bonding adhesive. Our control experiment, to determine the intrinsic tan δ in the SOI device layer without wafer bonding, also used Nb CPW readout coupled to LC resonators; however, the parallel-plate capacitors were fabricated on both sides of the Si device layer using a deep reactive ion etch (DRIE) to access the c-Si underside through the buried oxide and handle Si layers in the SOI wafers. We found that our wafer bonded devices demonstrated F· δ = (8 +/- 2) × 10(exp -5), where F is the filling fraction of two-level states (TLS). For the control experiment, F· δ = (2.0 +/- 0.6) × 10(exp -5), and we discuss what may be degrading the performance in the wafer bonded devices as compared to the control devices.

Beyer, A. D↗
NASA NTRS2016

Fabricating with Crystalline Si to Improve Superconducting Detector Performance

We built and measured radio-frequency (RF) loss tangent, tan d, evaluation structures using float-zone quality silicon-on-insulator (SOI) wafers with 5 µ m thick device layers. Superconducting Nb components were fabricated on both sides of the SOI Si device layer. Our main goals were to develop a robust fabrication for using crystalline Si (c-Si) dielectric layers with superconducting Nb components in a wafer bonding process and to confirm that tan d with c-Si dielectric layers was reduced at RF frequencies compared to devices fabricated with amorphous dielectrics, such as SiO2 and SixNy, where tan d ~ 10-3. Our primary test structure used a Nb coplanar waveguide (CPW) readout structure capacitively coupled to LC resonators, where the capacitors were defined as parallel-plate capacitors on both sides of a c-Si device layer using a wafer bonding process with benzocyclobutene (BCB) wafer bonding adhesive. Our control experiment, to determine the intrinsic tan d in the SOI device layer without wafer bonding, also used Nb CPW readout coupled to LC resonators; however, the parallel-plate capacitors were fabricated on both sides of the Si device layer using a deep reactive ion etch (DRIE) to access the c-Si underside through the buried oxide and handle Si layers in the SOI wafers. We found that our wafer bonded devices demonstrated F· d = (8 ± 2) × 10-5, where F is the filling fraction of two-level states (TLS). For the control experiment, F· d = (2.0 ± 0.6) × 10-5, and we discuss what may be degrading the performance in the wafer bonded devices as compared to the control devices.

Beyer, A D↗
NASA NTRS2002

Arc Jet Testing of the TIRS Cover Thermal Protection System for Mars Exploration Rover

This paper summarizes the arc jet test results of the Mars Exploration Rover (MER) Silicone Impregnated Reusable Ceramic Ablator (SIRCA) Transverse Impulse Rocket System (TIRS) Cover test series in the Panel Test Facility (PTF) at NASA Ames Research Center (ARC). NASA ARC performed aerothermal environment analyses, TPS sizing and thermal response analyses, and arc jet testing to evaluate the MER SIRCA TIRS Cover design and interface to the aeroshell structure. The primary objective of this arc jet test series was to evaluate specific design details of the SIRCA TIRS Cover interface to the MER aeroshell under simulated atmospheric entry heating conditions. Four test articles were tested in an arc jet environment with various sea] configurations. The test condition was designed to match the predicted peak flight heat load at the gap region between the SIRCA and the backshell TPS material, SLA-561S, and resulted in an over-test (with respect to heat flux and heat load) for the apex region of the SIRCA TIRS Cover. The resulting pressure differential was as much as twenty times that predicted for the flight case, depending on the location, and there was no post-test visual evidence of over-heating or damage to the seal, bracket, or backshell structure. The exposed titanium bolts were in good condition at post-test and showed only a small amount of oxidation at the leading edge locations. Repeatable thermocouple data were obtained and SIRCA thermal response analyses were compared to applicable thermocouple data. For the apex region of the SIRCA TIRS Cover, a one-dimensional thermal response prediction proved overly conservative, as there were strong multi-dimensional conduction effects evident from the thermocouple data. The one-dimensional thermal response prediction compared well with the thermocouple data for the leading edge "lip" region at the bolt location. In general, the test results yield confidence in the baseline seal design to prevent hot gas ingestion at the bracket and composite aeroshell structure interface.

Szalai, Christine E.↗
NASA NTRS2017

Tack Measurements of Prepreg Tape at Variable Temperature and Humidity

NASA’s Advanced Composites Project has established the goal of achieving a 30 percent reduction in the timeline for certification of primary composite structures for application on commercial aircraft. Prepreg tack is one of several critical parameters affecting composite manufacturing by automated fiber placement (AFP). Tack plays a central role in the prevention of wrinkles and puckers that can occur during AFP, thus knowledge of tack variation arising from a myriad of manufacturing and environmental conditions is imperative for the prediction of defects during AFP. A full design of experiments was performed to experimentally characterize tack on 0.25-inch slit-tape tow IM7/8552-1 prepreg using probe tack testing. Several process parameters (contact force, contact time, retraction speed, and probe diameter) as well as environmental parameters (temperature and humidity) were varied such that the entire parameter space could be efficiently evaluated. Mid-point experimental conditions (i.e., parameters not at either extrema) were included to enable prediction of curvature in relationships and repeat measurements were performed to characterize experimental error. Collectively, these experiments enable determination of primary dependencies as well as multi-parameter relationships. Slit-tape tow samples were mounted to the bottom plate of a rheometer parallel plate fixture using a jig to prevent modification of the active area to be interrogated with the top plate, a polished stainless steel probe, during tack testing. The probe surface was slowly brought into contact with the pre-preg surface until a pre-determined normal force was achieved (2-30 newtons). After a specified dwell time (0.02-10 seconds), during which the probe substrate interaction was maintained under displacement control, the probe was retracted from the surface (0.1-50 millimeters per second). Initial results indicated a clear dependence of tack strength on several parameters, with a particularly strong dependence on temperature and humidity. Although an increase in either of these parameters reduces tack strength, a maximum in tack was predicted to occur under conditions of low temperature and moderate humidity.

Wohl, Christopher↗
NASA NTRS1969

Hydrodynamics of a new concept of primary containment by energy absorption

Fluid dynamical analysis for idealized reactors system with spherical symmetry determines the effect which the destructive component of a nuclear accident produces on primary containment structures. Steel strands surrounding the reactor cavity in the biological shield exhibit plastic deformation to achieve the energy absorption.

Fistedis, S. H.↗