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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 1,189 records · Page 66

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NASA NTRS1987

Advances and trends in computational structural mechanics

The development status and applicational range of techniques in computational structural mechanics (CSM) are evaluated with a view to advances in computational models for material behavior, discrete-element technology, quality assessment, the control of numerical simulations of structural response, hybrid analysis techniques, techniques for large-scale optimization, and the impact of new computing systems on CSM. Primary pacers of CSM development encompass prediction and analysis of novel materials for structural components, computational strategies for large-scale structural calculations, and the assessment of response prediction reliability together with its adaptive improvement.

Noor, Ahmed K.↗

NASA NTRS1988

Composite piston

A composite piston structure is disclosed which provides a simple and reliable means for joining a carbon-carbon or ceramic piston cap with a metallic piston body. Attachment is achieved by means of a special geometry which compensates for differences in thermal expansion without complicated mechanical fastening devices. The shape employs a flange created by opposed frustoconical shapes with coincident vertices intersecting on the radial centerline of the piston in order to retain the piston cap. The use of carbon-carbon for the piston cap material allows a close fit between the piston and a cylinder wall, eliminating the need for piston rings. The elimination of extra mechanical parts of previous composite pistons provides a lightweight composite piston capable of extended high temperature operation.

Taylor, Allan H.↗

NASA NTRS1990

Advanced tube-bundle rocket thrust chamber

An advanced rocket thrust chamber for future space application is described along with an improved method of fabrication. Potential benefits of the concept are improved cyclic life, reusability, and performance. Performance improvements are anticipated because of the enhanced heat transfer into the coolant which will enable higher chamber pressure in expander cycle engines. Cyclic life, reusability and reliability improvements are anticipated because of the enhanced structural compliance inherent in the construction. The method of construction involves the forming of the combustion chamber with a tube-bundle of high conductivity copper or copper alloy tubes, and the bonding of these tubes by an electroforming operation. Further, the method of fabrication reduces chamber complexity by incorporating manifolds, jackets, and structural stiffeners while having the potential for thrust chamber cost and weight reduction.

Kazaroff, John M.↗

NASA NTRS1990

Advanced tube-bundle rocket thrust chamber

Kazaroff, John M.↗

NASA NTRS1990

The effect of nitric acid exposure on Galileo spacecraft titanium alloy Ti-6Al-4V propellant tanks

The Ti-6Al-4V-constructed retropropulsion-module tanks of the Galileo spacecraft were purged with nitrogen tetroxide in order to wait out a major launch rescheduling; nitric acid is among the residual products of such an operation. A test program was conducted on representative samples to ascertain the fracture toughness and stress corrosion threshold of the tanks' material, in view of Space Shuttle safety and mission-reliability requirements. It was found that the tanks' structural integrity was not degraded by nitric acid exposure.

Hsieh, Cheng↗

NASA NTRS1923

Air resistance measurements on actual airplane parts

For the calculation of the parasite resistance of an airplane, a knowledge of the resistance of the individual structural and accessory parts is necessary. The most reliable basis for this is given by tests with actual airplane parts at airspeeds which occur in practice. The data given here relate to the landing gear of a Siemanms-Schuckert DI airplane; the landing gear of a 'Luftfahrzeug-Gesellschaft' airplane (type Roland Dlla); landing gear of a 'Flugzeugbau Friedrichshafen' G airplane; a machine gun, and the exhaust manifold of a 269 HP engine.

Weiselsberger, C↗

NASA NTRS1937

Further Studies of Flame Movement and Pressure Development in an Engine Cylinder

This report describes an investigation using a stroboscopic apparatus for observing flame movement through a large number of small windows distributed over the head of a spark-ignition engine in following flame spread with combustion chambers of different shapes at two engine speed and for a variety of spark-plug locations including single and twin ignition. The principal factors influencing flame movement in the engine are discussed, and the lack of reliable information regarding their separate effects upon the structure of the flame and its speed of propagation are emphasized.

Marvin, Charles F , Jr↗

NASA NTRS1993

Investigation of spectral analysis techniques for randomly sampled velocimetry data

It is well known that velocimetry (LV) generates individual realization velocity data that are randomly or unevenly sampled in time. Spectral analysis of such data to obtain the turbulence spectra, and hence turbulence scales information, requires special techniques. The 'slotting' technique of Mayo et al, also described by Roberts and Ajmani, and the 'Direct Transform' method of Gaster and Roberts are well known in the LV community. The slotting technique is faster than the direct transform method in computation. There are practical limitations, however, as to how a high frequency and accurate estimate can be made for a given mean sampling rate. These high frequency estimates are important in obtaining the microscale information of turbulence structure. It was found from previous studies that reliable spectral estimates can be made up to about the mean sampling frequency (mean data rate) or less. If the data were evenly samples, the frequency range would be half the sampling frequency (i.e. up to Nyquist frequency); otherwise, aliasing problem would occur. The mean data rate and the sample size (total number of points) basically limit the frequency range. Also, there are large variabilities or errors associated with the high frequency estimates from randomly sampled signals. Roberts and Ajmani proposed certain pre-filtering techniques to reduce these variabilities, but at the cost of low frequency estimates. The prefiltering acts as a high-pass filter. Further, Shapiro and Silverman showed theoretically that, for Poisson sampled signals, it is possible to obtain alias-free spectral estimates far beyond the mean sampling frequency. But the question is, how far? During his tenure under 1993 NASA-ASEE Summer Faculty Fellowship Program, the author investigated from his studies on the spectral analysis techniques for randomly sampled signals that the spectral estimates can be enhanced or improved up to about 4-5 times the mean sampling frequency by using a suitable prefiltering technique. But, this increased bandwidth comes at the cost of the lower frequency estimates. The studies further showed that large data sets of the order of 100,000 points, or more, high data rates, and Poisson sampling are very crucial for obtaining reliable spectral estimates from randomly sampled data, such as LV data. Some of the results of the current study are presented.

Sree, Dave↗

NASA NTRS1996

Least Squares Best Fit Method for the Three Parameter Weibull Distribution: Analysis of Tensile and Bend Specimens with Volume or Surface Flaw Failure

Material characterization parameters obtained from naturally flawed specimens are necessary for reliability evaluation of non-deterministic advanced ceramic structural components. The least squares best fit method is applied to the three parameter uniaxial Weibull model to obtain the material parameters from experimental tests on volume or surface flawed specimens subjected to pure tension, pure bending, four point or three point loading. Several illustrative example problems are provided.

Gross, Bernard↗

NASA NTRS1996

Large-Eddy Simulation of Flow Around a NACA 4412 Airfoil Using Unstructured Grids

Large-eddy simulation (LES) has matured to the point where application to complex flows is described. The extension to higher Reynolds numbers leads to an impractical number of grid points with existing structured-grid methods. Furthermore, most real world flows are rather difficult to represent geometrically with structured grids. Unstructured-grid methods offer a release from both of these constraints. However, just as it took many years for structured-grid methods to be well understood and reliable tools for LES, unstructured-grid methods must be carefully studied before we can expect them to attain their full potential.

Jansen, Kenneth↗

NASA NTRS2000

Probabilistic Structural Analysis of the Solid Rocket Booster Aft Skirt External Fitting Modification

NASA has funded several major programs (the Probabilistic Structural Analysis Methods Project is an example) to develop probabilistic structural analysis methods and tools for engineers to apply in the design and assessment of aerospace hardware. A probabilistic finite element software code, known as Numerical Evaluation of Stochastic Structures Under Stress, is used to determine the reliability of a critical weld of the Space Shuttle solid rocket booster aft skirt. An external bracket modification to the aft skirt provides a comparison basis for examining the details of the probabilistic analysis and its contributions to the design process. Also, analysis findings are compared with measured Space Shuttle flight data.

Townsend, John S.↗

NASA NTRS1999

MEMS Reliability Assurance Guidelines for Space Applications

This guide is a reference for understanding the various aspects of microelectromechanical systems, or MEMS, with an emphasis on device reliability. Material properties, failure mechanisms, processing techniques, device structures, and packaging techniques common to MEMS are addressed in detail. Design and qualification methodologies provide the reader with the means to develop suitable qualification plans for the insertion of MEMS into the space environment.

Stark, Brian↗

NASA NTRS2001

National Rocket Propulsion Materials Plan: A NASA, Department of Defense, and Industry Partnership

NASA, Department of Defense, and rocket propulsion industry representatives are working together to create a national rocket propulsion materials development roadmap. This "living document" will facilitate collaboration among the partners, leveraging of resources, and will be a highly effective tool for technology development planning. The structuring of the roadmap, and development plan, which will combine the significant efforts of the Integrated High Payoff Rocket Propulsion Technology (IHPRPT) Program, and NASA's Integrated Space Transportation Plan (ISTP), is being lead by the IHPRPT Materials Working Group (IMWG). The IHPRPT Program is a joint DoD, NASA, and industry effort to dramatically improve the nation's rocket propulsion capabilities. This phased program is structured with increasingly challenging goals focused on performance, reliability, and cost to effectively double rocket propulsion capabilities by 2010. The IHPRPT program is focused on three propulsion application areas: Boost and Orbit Transfer (both liquid rocket engines and solid rocket motors), Tactical, and Spacecraft. Critical to the success of this initiative is the development and application of advanced materials, processes, and manufacturing technologies. NASA's ISTP is a comprehensive strategy focusing on the aggressive safety, reliability, and affordability goals for future space transportation systems established by the agency. Key elements of this plan are the 2 nd and 3 d Generation Reusable Launch Vehicles (RLV). The affordability and safety goals of these generational systems are, respectively, 10X cheaper and 100X safer by 2010, and 100X cheaper and 10,000X safer by 2025. Accomplishment of these goals requires dramatic and sustained breakthroughs, particularly in the development and the application of advanced material systems. The presentation will provide an overview of the IHPRPT materials initiatives, NASA's 2nd and 3 rd Generation RLV propulsion materials projects, and the approach for the development of the national rocket propulsion materials roadmap.

Clinton, Raymond G., Jr.↗

NASA NTRS1997

Advanced High-Temperature Engine Materials Technology Progresses

The objective of the Advanced High Temperature Engine Materials Technology Program (HITEMP) at the NASA Lewis Research Center is to generate technology for advanced materials and structural analysis that will increase fuel economy, improve reliability, extend life, and reduce operating costs for 21st century civil propulsion systems. The primary focus is on fan and compressor materials (polymer-matrix composites - PMC's), compressor and turbine materials (superalloys, and metal-matrix and intermetallic-matrix composites - MMC's and IMC's), and turbine materials (ceramic-matrix composites - CMC's). These advanced materials are being developed in-house by Lewis researchers and on grants and contracts.

Source record↗

NASA NTRS2005

Cyclic Spin Testing of Superalloy Disks With a Dual Grain Microstructure

An aggressive cyclic spin test program was run to verify the reliability of superalloy disks with a dual grain structure, fine grain bore and coarse grain rim, utilizing a disk design with web holes bisecting the grain size transition zone. Results of these tests were compared with conventional disks with uniform grain structures. Analysis of the test results indicated the cyclic performance of disks with a dual grain structure could be estimated to a level of accuracy which does not appear to prohibit the use of this technology in advanced gas turbine engines, although further refinement of lifing methodology is clearly warranted.

Gayda, John↗

NASA NTRS2005

Materials Challenges in Space Exploration

The new vision of space exploration encompasses a broad range of human and robotic missions to the Moon, Mars and beyond. Extended human space travel requires high reliability and high performance systems for propulsion, vehicle structures, thermal and radiation protection, crew habitats and health monitoring. Advanced materials and processing technologies are necessary to meet the exploration mission requirements. Materials and processing technologies must be sufficiently mature before they can be inserted into a development program leading to an exploration mission. Exploration will be more affordable by in-situ utilization of materials on the Moon and Mars.

Vickers, John↗

NASA NTRS2005

Strategies and Approaches to TPS Design

Thermal protection systems (TPS) insulate planetary probes and Earth re-entry vehicles from the aerothermal heating experienced during hypersonic deceleration to the planet s surface. The systems are typically designed with some additional capability to compensate for both variations in the TPS material and for uncertainties in the heating environment. This additional capability, or robustness, also provides a surge capability for operating under abnormal severe conditions for a short period of time, and for unexpected events, such as meteoroid impact damage, that would detract from the nominal performance. Strategies and approaches to developing robust designs must also minimize mass because an extra kilogram of TPS displaces one kilogram of payload. Because aircraft structures must be optimized for minimum mass, reliability-based design approaches for mechanical components exist that minimize mass. Adapting these existing approaches to TPS component design takes advantage of the extensive work, knowledge, and experience from nearly fifty years of reliability-based design of mechanical components. A Non-Dimensional Load Interference (NDLI) method for calculating the thermal reliability of TPS components is presented in this lecture and applied to several examples. A sensitivity analysis from an existing numerical simulation of a carbon phenolic TPS provides insight into the effects of the various design parameters, and is used to demonstrate how sensitivity analysis may be used with NDLI to develop reliability-based designs of TPS components.

Paul Kolodziej↗

NASA NTRS2006

High-Resolution Inspection of the Space Shuttle External Tank Spray-on-Foam Insulation (SOFI) using Focused Millimeter Waves at D-Band (150 GHz)

Space Shuttle Columbia's catastrophic failure has been attributed to a piece of spray-on-foam insulation (SOFI) that was dislodged from the external tank and struck the leading edge of the left wing. A piece of SOFI was also dislodged in the recent Space Shuttle Discovery's flight. Clearly, there is a great and urgent need to inspect the external tank SOFI and other similar insulating structures (including the acreage heat tile) in a reliable and robust fashion. In the past two years, millimeter wave nondestructive testing methods, using both real and synthetic focusing techniques, have shown great potential for this purpose. Recently obtained real-focused images from several different and complex SOFI panels have demonstrated the utility of these methods as being viable, robust, repeatable, simple, portable and effective. D-band frequency range which covers a frequency spectrum of 110- 170 GHz is well-suited for this purpose given the nature of the foam which causes significant scattering at much higher frequencies. This paper presents the results of using continuous-wave (CW) reflectometry conducted on several typical and complex SOFI panes at 150 GHz.

Kharkovsky, S.↗