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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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Titan has a warm upper atmosphere. Whether it has a warm lower atmosphere and hot surface is an open question. This question is important not only from a purely scientific point of view, but also for assessing the viability of a Titan entry probe.
The possibility of identifying ground surface material by measuring the surface temperature at two different and significant times of the day was investigated for the case of hypothetical island whose rocky surface contained no vegetation and consisted of dolomite, clay, and granite. The thermal dynamics of the soil surface during a day in which atmospheric conditions were average for a latitude of about 40 deg to 50 deg were numerically simulated. The line of separation between zones of different materials was delineated by the range of temperature variation. Results show that the difference between maximum and minimum value of the temperature of ground surface during the day is linked to the thermal inertia value of the material of which the rock is formed.
Optical and electrical characterization of defects has been started in EFG ribbon grown in a system that will be used to test the stress model. Temperature and stress field modeling aimed at defining low stress growth configuration is also in progress, and results will be used to guide development of the experimental system. The baseline defect configuration for ribbon grown at speeds of approx. 1 cm/min consists of dislocation densities of the order of 10 to the 5th power to 10 to the 6th power/sq cm, as well as saucer type etch pits and line defects. All these defects are inhomogeneously distributed. EBIC measurements indicate that diffusion lengths are in the range 20 to 60 microns, and significant spatial inhomogeneities occur through the ribbon thickness. Growth speed changes in the range 0.7-1.0 cm/min do not produce significant variations in ribbon defect configurations.
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