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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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Long-term aging of elastomers: Chemical stress relaxation of fluorosilicone rubber and other studies

Aerospace applications of elastomers are considered, including: propellant binders, bladder materials for liquid propellant expulsion systems, and fuel tank sealants for high-speed aircraft. A comprehensive molecular theory for mechanical properties of these materials has been developed but has only been tested experimentally in cases where chemical degradation processes are excluded. Hence, a study is being conducted to ascertain the nature, extent, and rate of chemical changes that take place in some elastomers of interest. Chemical changes that may take place in the fluorosilicone elastomer, LS 420, which is regarded as a fuel and high-temperature-resistant rubber are investigated. The kinetic analysis of the chemical stress relaxation and gel permeation chromatography studies comprise the major portion of the report.

Kalfayan, S. H.↗
NASA NTRS1972

Size frequency distribution of Martian craters and relative age of light and dark terrains.

Light and dark terrains in and around Meridiani Sinus, mapped on the imagery from Mariner 6 and Mariner 7, were found to have significantly different cumulative size frequency distributions of craters. The light terrain on a mosaic of frames 6N11, 6N13, and 6N19 has a greater proportion of large craters and a lesser proportion of smaller craters than the dark terrain on the same frames. The light terrain is interpreted to be generally older than the dark terrain. The filling or partial filling of the smaller craters on the light terrain by surface detritus is suggested. Several wide-angle frames have remarkably similar cumulative crater size frequency distributions that may be representative of a large portion of the Martian surface.

Woronow, A.↗
NASA NTRS1972

The relative age of the transition zone between Hellas and the Martian cratered terrain.

Consideration of the relationships of craters to scarps and ridges and of the antiquity of Hellas relative to the cratered terrain. Scarps and ridges in the transition zone between Hellas and the cratered terrain both postdate and predate large craters. It appears that there are a number of craters which are older than the transition zone structures, which in turn are presumably related in some way to the formation of Hellas. Sharp et al. (1971) have suggested impact, large-scale volcanic explosion, or subsidence for the origin of Hellas. Volcanic explosion seems the least likely explanation, for the resulting deficiency of mass beneath Hellas should induce later isostatic rebound, contrary to observations of the transition zone which imply subsidence relatively late in the history of the Martian surface. An origin of Hellas by impact with later isostatic subsidence (because of a dense mass under its floor, as suggested by Sharp et al.) to account for the characteristics of the transition zone seems to be the best model, and may also account for the featureless floor of the basin.

Thorman, C. H.↗
NASA NTRS1972

Long Term Aging of Elastomers: Chemorheology of Viton B Fluorocarbon Elastomer

The continuation of a study to ascertain the nature, extent, and the rate of chemical changes that take place in certain selected elastomers is reported. Under discussion is Viton B, regarded as a temperature and fuel resistant fluorocarbon rubber. The kinetic analysis of the chemical stress relaxation, and infrared and gel permeation chromatography analysis results are discussed.

Kalfayan, S. H.↗
NASA NTRS1973

Distinguishing major lithologic types in rocks of precambrian age in central Wyoming using multilevel sensing, with a chapter on possible economic significance of iron formation discovered by use of aircraft images in the Granite Mountains of Wyoming

The author has identified the following significant results. Information obtained by remote sensing from three altitude levels: ERTS-1 (565 miles), U-2 (60,000 feet), and C-130 aircraft (15,000 feet) illustrates the possible application of multilevel sensing in mineral exploration. Distinction can be made between rocks of greenstone belts and rocks of granite-granite gneiss areas by using ERTS-1 imagery in portions of the Precambrian of central Wyoming. Study of low altitude color and color infrared photographs of the mafic terrain revealed the presence of metasedimentary rocks with distinct layers that were interpreted as amphibolite by photogeologic techniques. Some of the amphibolite layers were found to be iron formation when examined in the field. To our knowledge this occurrence of iron formation has not been previously reported in the literature.

Houston, R. S.↗