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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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The author has identified the following significant results. The most significant achievement thus far includes the successful charting of high probability fishing areas from LANDSAT MSS data and the successful simulation of an operational satellite system to provide tactical information for the commercial harvest of menhaden.
Technical nondestructive evaluation approaches to the determination of fastener integrity were assessed. Existing instruments and methods used to measure stress or strain were examined, with particular interest in fastener shank stress. Industry procedures being followed were evaluated to establish fastener integrity criteria.
Retaining ring and fine wire secure nuts or screws reliably. Retainer is easy to assemble and to disassemble, even in confined areas.
A test program was initiated at the Jet Propulsion Laboratory to experimentally determine the cyclic fatigue life of pre-cracked A286 stainless steel fasteners which just survived a proof test to a prescribed fraction of their ultimate tensile strength. The functional dependency of the cyclic fatigue life of a fastener on the fatigue stress (mean and alternating stresses), fastener size, material tensile strength, and proof load was formulated using the NASA/FLAGRO computer program. It was found that proof load has the strongest effect on fatigue life, while the mean stress has the least effect. The fastener size only has a minor effect, but the alternating stress range has a strong influence on the fatigue life of fasteners. Limited experimental verification of the hypothesized functional relationship is provided in this program for the effect of proof load and fastener size in addition to the analytic verification.
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Silicon carbide (SiC) fiber is a material that may be used in advanced thermal protection systems (TPS) for future aerospace vehicles. SiC fiber's mechanical properties depend greatly on the presence or absence of sizing and its microstructure. In this research, silicon dioxide is found to be present on the surface of the fiber. Electron Spectroscopy for Chemical Analysis (ESCA) and Scanning Electron Microscopy (SEM) show that a thin oxide layer (SiO2) exists on the as-received fibers, and the oxide thickness increases when the fibers are exposed to high temperature. ESCA also reveals no evidence of Si-C bonding on the fiber surface on both as-received and heat treated fibers. The silicon oxide layer is thought to signal the decomposition of SiC bonds and may be partially responsible for the degradation in the breaking strength observed at temperatures above 400 C. The variation in electrical resistivity of the fibers with increasing temperature indicates a transition to a higher band gap material at 350 to 600 C. This is consistent with a decomposition of SiC involving silicon oxide formation.
The investigation was made for the purpose of ascertaining the notch sensitivity of flat strips of light alloy with cylindrical holes under initial tension stress, with special attention to the change in notch-effect factors with the number of load cycles. Then the studies were extended to similar flat strips with pin-loaded holes (tension lugs). This report deals with fatigue tests under initial tension load on flat test specimens of 3116.5 duralumin and AZM 3510.1 electron with plain unloaded and pin-loaded holes (tension lugs) of different forms.
The Link Monitor and Control Operator Assistant prototype (LMCOA) is a state-of-the-art, semiautomated monitor and control system based on an object-oriented design. The purpose of the LMCOA prototyping effort is to both investigate new technology (such as artificial intelligence) to support automation and to evaluate advances in information systems toward developing systems that take advantage of the technology. The emergence of object-oriented design methodology has enabled a major change in how software is designed and developed. This paper describes how the object-oriented approach was used to design and implement the LMCOA and the results of operational testing. The LMCOA is implemented on a NeXT workstation using the Mach operating system and the Objective-C programming language.
The first solar plane we developed at AeroVironment was named the Gossamer Penguin. The word "gossamer" was an apt description of the appearance of this strange-looking aircraft that had a structural weight of only 54 pounds, with a wing span of 71 feet. Much was sacrificed to save weight and maximize span, and this presented serious problems when handling the aircraft on the ground. The Penguin was barely strong enough to stay together in the light winds and low turbulence of the early and low turbulence of the early morning. Moving the Penguin back to the hangar at the end of a morning flight was much like walking a 71-foot span kite home from the park.
This viewgraph presentation reviews the many parts of the JPL mission planning process that the project manager has to work with. Some of them are: NASA & JPL's institutional requirements, the mission systems design requirements, the science interactions, the technical interactions, financial requirements, verification and validation, safety and mission assurance, and independent assessment, review and reporting.
No abstract available
An apparatus includes a shaft, a device, a fastener, and an anti-rotation clip. The shaft is configured for rotation. The device is mounted on, and surrounds at least a portion of, the shaft, and has first and second protrusions that are formed on one side and are spaced apart to define a tab space. The fastener is rotationally mounted relative to the shaft, and includes a tab slot formed in its outer surface that extends radially inwardly and is disposed radially inwardly of the tab space. The anti-rotation clip includes a main body portion and a head portion that has a first tab portion and a second tab portion. At least a portion the main body portion is disposed between the device and the fastener, the first tab is disposed in the tab space, and the second tab is disposed in the tab slot.
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Development of the Program to Optimize Simulated Trajectories (POST) began in the 1970s. Since then, it has become widely utilized across NASA, industry, and academia to solve a variety of atmospheric ascent and entry problems. Its successor, POST2, has undergone many upgrades since its release in the 1990s. Recently, there has been an increasing desire to take advantage of the advances in parallel computing for both offline and online systems. Thus, modifications were made to allow POST2 to simulate multiple trajectories simultaneously without adversely affecting results. This capability is leveraged to calculate optimization solutions in parallel as opposed to sequentially. A demonstration of the benefits is presented using a small set of POST2 regression tests, as well as a project simulating a human-scale Lunar lander.
Development of the Program to Optimize Simulated Trajectories (POST) began in the 1970s. Since then, it has become widely utilized across NASA, industry, and academia to solve a variety of atmospheric ascent and entry problems. Its successor, POST2, has undergone many upgrades since its release in the 1990s. Recently, there has been an increasing desire to take advantage of the advances in parallel computing for both offline and online systems. Thus, modifications were made to allow POST2 to simulate multiple trajectories simultaneously without adversely affecting results. This capability is leveraged to calculate optimization solutions in parallel as opposed to sequentially. A demonstration of the benefits is presented using a small set of POST2 regression tests, as well as a project simulating a human-scale Lunar lander.
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