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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Flexible Plug Repair for Shuttle Wing Leading Edge

In response to the Columbia Accident Investigation Board report, a plug repair kit has been developed to enable astronauts to repair the space shuttle's wing leading edge (WLE) during orbit. The plug repair kit consists of several 17.78- cm-diameter carbon/silicon carbide (C/SiC) cover plates of various curvatures that can be attached to the refractory carbon-carbon WLE panels using a TZM refractory metal attach mechanism. The attach mechanism is inserted through the damage in the WLE panel and, as it is tightened, the cover plate flexes to conform to the curvature of the WLE panel within 0.050 mm. An astronaut installs the repair during an extravehicular activity (EVA). After installing the plug repair, edge gaps are checked and the perimeter of the repair is sealed using a proprietary material, developed to fill cracks and small holes in the WLE.

Camarda, Charles J.↗
DOE OSTI2024

Neutron Diffraction Residual Stress Study of a AA2219-T87 Self-Reacting Friction Stir Weld

2219-T87 is a precipitation hardenable aluminum-copper alloy which sees wide use in structural aerospace components. Thick panels of this alloy are joined via self-reacting friction welding (SRFSW); however, this thermomechanical process can result in significant loss of the alloy’s strengthening precipitates and large residual stresses which are detrimental to mechanical behavior and performance. High-resolution maps of the residual strain and stress states along the normal, transverse, and longitudinal directions of 2219-T87 SRFSW were obtained using neutron diffraction measurements. Residual stress had the highest tensile value in the heat-affected zone (HAZ) and the largest compressive stress in the base metal region of the normal and transverse directions. Line profile residual stress distributions displayed an “M”-shaped distribution in each direction with the longitudinal direction being the most pronounced while 2D residual stresses displayed an hourglass-shaped pattern. Further, average maximal longitudinal residual stress values ranged from 60.6 to 85.6% of yield. Microhardness testing across the transverse weld section produced a “V”-shaped curve with slight hardness recovery in the stir zone. Maximal and minimal microhardness values were observed in the base metal (154 HV) and thermomechanically affected zone (82 HV), respectively. Microstructural evolution was recorded using optical microscopy and showed decreasing grain size from the HAZ to the stir zone.

36 MATERIALS SCIENCE↗
NASA NTRS1977

Structural design significance of tension-tension fatigue data on composites

Constant cycle tension-tension fatigue and related static tension data have been generated on six single composite material/orientation combinations and twenty-one hybrid composite material/orientation combinations. Anomalies are related to the temperature rise and stopped interval creep, whereas endurance limit stresses (runouts) are associated with static proportional limit values, when they occur, and internal damage. The significance of these room temperature-dry data on the design allowables and weight of aerodynamic structueres is discussed. Such structures are helicopter rotor blades and wing and horizontal stabilizer lower surfaces. Typical criteria for turning these data into preliminary allowables are shown, as are examples of such allowables developed from the data. These values are then compared to those that might be used if the structures were made of metal.

Grimes, G. C.↗
NASA NTRS1988

Body weight of hypersonic aircraft, part 1

The load bearing body weight of wing-body and all-body hypersonic aircraft is estimated for a wide variety of structural materials and geometries. Variations of weight with key design and configuration parameters are presented and discussed. Both hot and cool structure approaches are considered in isotropic, organic composite, and metal matrix composite materials; structural shells are sandwich or skin-stringer. Conformal and pillow-tank designs are investigated for the all-body shape. The results identify the most promising hypersonic aircraft body structure design approaches and their weight trends. Geometric definition of vehicle shapes and structural analysis methods are presented in appendices.

Ardema, Mark D.↗
NASA NTRS1934

The torsional stiffness of thin duralumin shells subjected to large torques

This report gives a simple method of estimating the torsional stiffness of thin shells, such as box beams or stressed-skin wings under large torque loads. A general efficiency chart for shells in torsion is established, based on the assumption that the efficiency of the web sheet in resisting deformation decreases linearly with the average stress. The chart is used to calculate the torsional deflections of eight box beams, a test wing panel, and a complete wing; the results of the calculations are shown in comparison with the test results. The agreement is probably as good as might be expected considering the empirical nature of the method and the well-known dispersion between results of tests on thin sheet-metal structures.

Kuhn, Paul↗
NASA NTRS1994

Lamb Wave Response of Fatigued Composite Samples

Composite materials are being more widely used today by aerospace, automotive, sports equipment, and a number of other commercial industries because of their advantages over conventional metals. Composites have a high strength-to-weight ratio and can be constructed to meet specific design needs. Composite structures are already in use in secondary parts of the Douglas MD-11 and are planned to be used in the new MD-12X. Plans also exist for their use in primary and secondary structures on the Boeing 777. Douglas proposed MD-XX may also incorporate composite materials into primary structures such as the wings and tail. Use of composites in these structures offers weight savings, corrosion resistance, and improved aerodynamics. Additionally, composites have been used to repair cracks in many B-1Bs where traditional repair techniques were not very effective. Plans have also been made to reinforce all of the remaining B-1s with composite materials. Verification of the structural integrity of composite components is needed to insure safe operation of these aerospace vehicles. One aspect of the use of these composites is their response to fatigue. To track this progression of fatigue in aerospace structures, a convenient method to nondestructively monitor this damage needs to be developed. Traditional NDE techniques used on metals are not easily adaptable to composites due to the inhomogeneous and anisotropic nature of these materials. Finding an effective means of nondestructively monitoring fatigue damage is extremely important to the safety and reliability of such structures. Lamb waves offer one method of evaluating these composite materials. As a material is fatigued, the modulus degrades. Since the Lamb wave velocity can be related to the modulus of the material, an effective tool can be developed to monitor fatigue damage in composites by measuring the velocity of these waves. In this work, preliminary studies have been conducted which monitor fatigue damage in composite samples using strain gage measurements as well as Lamb wave velocity measurements. A description of the test samples is followed by the results of two different measurements of Lamb wave velocity. The first technique is a contact measurement done at a single frequency, while the second involves an immersion study of Lamb waves in which dispersion curves are obtained. The results of the Lamb wave monitoring of fatigue damage is compared to the damage progression measured by strain gages. The final section discusses the results and conclusions.

Seale, Michael↗
NASA NTRS1975

Joining and fabrication of metal-matrix composite materials

Manufacturing technology associated with developing fabrication processes to incorporate metal-matrix composites into flight hardware is studied. The joining of composite to itself and to titanium by innovative brazing, diffusion bonding, and adhesive bonding is examined. The effects of the fabrication processes on the material properties and their influence on the design of YF-12 wing panels are discussed.

Royster, D. M.↗
DOE OSTI2020

Atom femtosecond optical trap based on spectrally filtered laser radiation

We have examined the use of alkali metal (rubidium) vapour for spectral filtering of broadband pulsed laser light that is used to produce a femtosecond pulsed optical dipole trap. It has been shown that, even at large detuning of the centre emission frequency from the frequency of atomic transitions, spectral components present in the wings of the laser emission line are capable of heating localised atoms, thus reducing their lifetime in the atomic trap. Using atomic vapour for filtering the laser emission spectrum, we have suppressed its spectral components resulting in heating. This has made it possible to increase the lifetime of atoms in the pulsed optical dipole trap to a value comparable to their lifetime in an optical trap formed by narrow-band cw laser light. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2019

Potential Weight Benefits of IM7/8552 Hybrid Thin-Ply Composites for Aircraft Structures

Composite materials have increasingly been used for aerospace applications due to improved performance and reduced weight compared to their metallic counterparts. Inclusion of thin-ply material, plies with cured thickness half or less than standard-ply composites, have potential to improve performance and reduce structural weight further. The effect of thin-ply material on the weight of aircraft structure was investigated by examining wing cover weight reduction. To minimize the effects on manufacturing due to using thin plies, hybrid laminates were examined that used thin ±45-degree plies to replace their standard-ply counterparts in laminates. Compression after impact (CAI) tests were conducted to examine the possible weight savings that could be gained by increasing the design allowables that were used to size the wing upper cover of a semi-span test article. A large increase in CAI strength was observed for quasi-isotropic hybrid laminates, whereas less improvement was seen for hard hybrid laminates such as found in the wing cover. For laminates design by CAI strength, weight savings of about 13% were found using the hybrid hard laminates compared to the standard-ply laminates. Whether similar weight savings could be expected for structure sized using tension after impact allowables will have to be investigated further. Notched specimens were tested to examine possible weight savings using hybrid laminates in regions that are sized using discrete source damage requirements. As expected, the hybrid laminate had marginal improvements over the standard-ply laminate for compression with a notch present. The hybrid laminate, however, exhibited about 20% lower strength than the standard-ply laminate counterpart for tension with a notch. The failure mode of the hybrid specimens was a brittle, self-similar crack, which differs from the standard-ply specimens that failed by significant amounts of delamination and fiber splitting. In light of the apparent reduction in notched tensile strength, additional investigation is required to assess the use of hybrid laminates for areas containing discrete source damage, and their effect on weight of such regions.

Lovejoy, Andrew E.↗
NASA NTRS1978

The M-15-aircraft (samolot M-15)

The M-15 is an all-metal, semimonocoque, twin-tail-boom sesquiplane aircraft designed exclusively for agricultural support operations involving slow low-level flight. It is powered by a single Al-25 bypass turbojet engine used in the Yak-40 aircraft. Tanks for spraying chemicals are mounted between the lower and upper wings. Dimensions, weights, and performance data are tabulated.

Leiiecki, R.↗
NASA NTRS2004

FUSE Observations of LMC and SMC 03-4 Stars: Physical Parameters of the Hottest Stars

The goal of the project is to analyze the spectra of the most massive stars in our neighbor Galaxies, to determine the physical parameters of temperature, mass, gravity, and Luminosity, together with the stellar wind properties. For this purpose, FUSE spectra, HST spectra (uv and optical) and high quality optical spectra obtained with ground-based telescopes need to be analyzed wing modern NLTE model atmosphere techniques. The combination of the use of spectra from different wavelength regions is a fundamental aspect of the project. Each spectral domain adds complementary important to the process of the spectral analysis. In this way the comparison of stellar properties between galaxies of different metallicity will become more significant.

Kudrtizki, Rolf-Peter↗
DOE OSTI2022

Structural and mechanistic basis for redox sensing by the cyanobacterial transcription regulator RexT

Abstract Organisms have a myriad of strategies for sensing, responding to, and combating reactive oxygen species, which are unavoidable consequences of aerobic life. In the heterocystous cyanobacterium Nostoc sp. PCC 7120, one such strategy is the use of an ArsR-SmtB transcriptional regulator RexT that senses H 2 O 2 and upregulates expression of thioredoxin to maintain cellular redox homeostasis. Different from many other members of the ArsR-SmtB family which bind metal ions, RexT has been proposed to use disulfide bond formation as a trigger to bind and release DNA. Here, we present high-resolution crystal structures of RexT in the reduced and H 2 O 2 -treated states. These structures reveal that RexT showcases the ArsR-SmtB winged-helix-turn-helix fold and forms a vicinal disulfide bond to orchestrate a response to H 2 O 2 . The importance of the disulfide-forming Cys residues was corroborated using site-directed mutagenesis, mass spectrometry, and H 2 O 2 -consumption assays. Furthermore, an entrance channel for H 2 O 2 was identified and key residues implicated in H 2 O 2 activation were pinpointed. Finally, bioinformatics analysis of the ArsR-SmtB family indicates that the vicinal disulfide “redox switch” is a unique feature of cyanobacteria in the Nostocales order, presenting an interesting case where an ArsR-SmtB protein scaffold has been evolved to showcase peroxidatic activity and facilitate redox-based regulation.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1981

Opportunities for structural improvements for an advanced supersonic transport vehicle

The superplastically formed diffusion-bonded (SPF/DB) program has developed successfully and far enough to recommend that a major structural program to validate the weight and cost of SPF/DB sandwich titanium structure should be initiated. The NASA Langley study of wing and fuselage SPF/DB sandwich panels shows that this process is potentially structurally efficient. The Douglas SPF/DB expanded sandwich process that utilizes a welded core sheet that expands to face sheets proves to be very efficient. The theoretical weight optimization design charts for the wing and fuselage concepts were validated by small-scale tests. Mnay design applications were fabricated. Projecting the results of an SPF/DB sandwich airframe structure to a MDC AST design shows significant weight and cost savings. A 6 percent lower direct operating cost was calculated. A growth AST utilizing composites, metal matrices, and SPF/DB sandwich shows future promise for a post-1990 technology readiness. Titanium SPF/DB sandwich, compared to presently available aluminum structure, is superior for application to a Mach 2.2 supersonic transport.

Fischler, J. E.↗
NASA NTRS1981

Progress in supersonic cruise technology

It is reported that nine years of NASA research have yielded significant design solutions in such matters pertaining to large supersonic cruise vehicles as aerodynamics, structures, propulsion, noise reduction, takeoff and landing procedures, and advanced configuration concepts. Attention is given to the incremental performance gains achieved over the years (with the Concorde SST as baseline reference), arrow wing planform performance potential, superplastic forming/diffusion bonding of titanium alloy primary structures, advanced engine cycles, twin-fuselage high-capacity configurations, and the potential military payoff of SST research. It is concluded that the greatest promise for future research and development lies in fiber-reinforced, high-temperature metal structures and the twin-fuselage configuration.

Driver, C.↗
NASA NTRS1998

Application of Rapid Prototyping Methods to High-Speed Wind Tunnel Testing

This study was undertaken in MSFC's 14-Inch Trisonic Wind Tunnel to determine if rapid prototyping methods could be used in the design and manufacturing of high speed wind tunnel models in direct testing applications, and if these methods would reduce model design/fabrication time and cost while providing models of high enough fidelity to provide adequate aerodynamic data, and of sufficient strength to survive the test environment. Rapid prototyping methods utilized to construct wind tunnel models in a wing-body-tail configuration were: fused deposition method using both ABS plastic and PEEK as building materials, stereolithography using the photopolymer SL-5170, selective laser sintering using glass reinforced nylon, and laminated object manufacturing using plastic reinforced with glass and 'paper'. This study revealed good agreement between the SLA model, the metal model with an FDM-ABS nose, an SLA nose, and the metal model for most operating conditions, while the FDM-ABS data diverged at higher loading conditions. Data from the initial SLS model showed poor agreement due to problems in post-processing, resulting in a different configuration. A second SLS model was tested and showed relatively good agreement. It can be concluded that rapid prototyping models show promise in preliminary aerodynamic development studies at subsonic, transonic, and supersonic speeds.

Springer, A. M.↗
NASA NTRS1985

Orbit on demand - Structural analysis finds vertical launchers weigh less

Structural considerations arising from favored design concepts for the next generation on-demand launch vehicles are explored. The two emerging concepts are a two stage fully reusable vertical take-off vehicle (V-2) and a horizontal take-off, two stage subsonic boost launch vehicle (H-2-Sub). Both designs have an 1100 n. mi. cross-range capability, with the V-2 orbiter having small wings with winglets for hypersonic trim and the H-2-Sub requiring larger, swept wings. The rockets would be cryogenic, while airbreathing initial boosters would be either turbofans, turbojets and/or ramjets. Dynamic loading is lower in the launch of a V-2. The TPS is a critical factor due to thinner leading edges than on the Shuttle and may require heat-pipe cooling. Airframe structures made of metal matrix composites have passed finite element simulations of projected loads and can now undergo proof-of-concept tests, although whisker-reinforced materials may be superior once long-whisker technology is developed.

Taylor, A. H.↗
NASA NTRS1990

The hot DOA1 degenerate HZ 21 - A search for circumstellar/photospheric metals and peculiar absorption at He II

A high-resolution IUE spectrum of the hot DO1 degenerate HZ 21 was obtained by combining US1 + European 2 low-background observing shifts. The SWP image reveals a rich spectrum of interstellar absorption lines with an average velocity in the line of sight to HZ 21 of -30 km/s. However, there is no clear evidence of any highly or lowly ionized metal features which could be attributed to circumstellar, wind, or photospheric absorption. There is, however, a broad absorption trough at He II (1640) which was not unexpected, given the clear presence of He II (4686) absorption in this star's optical spectrum. The velocity width of He II (1640) appears consistent with photospheric absorption wings which appear to flank the geocoronal Ly-alpha emission feature. The He II (1640) feature reveals what appears to be a broad (310 km/s) emission reversal. Evidence is provided that the emission reversal is probably real.

Fritz, M. L.↗