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A detailed chemical kinetic model for N 2 -CH 4 -Ar mixtures is developed for nonequilibrium simulation of shock layers formed in front of probes entering Titan's atmosphere. The detailed kinetic model uses up-to-date chemical reaction mechanisms and reaction rates, and it is validated against existing shock tube experiments. A reduced kinetic model is also developed through sensitivity analysis of chemical reactions in the detailed model and reproduces the chemical kinetics of major species within the parameter space that may be encountered during Titan atmospheric entry. The reduced model, having fewer species and reactions than the detailed model, is better suited to coupled reacting computational fluid dynamics flowfield calculations. Nomenclature A = constant used in evaluating forward rate coefficient F = uncertainty factor for forward rate coefficient k f = forward rate coefficient n = temperature exponent used in evaluating forward rate coefficient p = pressure S X;r = sensitivity coefficient of X with respect to reaction r, defined in the text T = geometrically averaged temperature, TT v p T a = temperature constant in forward rate coefficient (activation temperature) T r = translational-rotational temperature T v = vibrational-electronic temperature u = x component of velocity

In the present study, radiation emanating from the freestream and shock-layer ow over a 15.24-cmdiam, at-faced cylinder model was measured in the NASA Ames Research Center's 20-MW Arcjet Facility. The test gas was a mixture of argon and air. Spatially resolved emission spectra were obtained over a 200-to 890-nm wavelength range using a charged-coupled device camera (1024 3 256 array) attached to a spectrograph. The optical system was calibrated using tungsten and deuterium radiation sources. Analytical tools were used to determine the following line-of-sight-averaged thermodynamic properties from the calibrated spectra: 1) rotational temperature of the freestream and 2) rotational, vibrational, electronic temperatures, and species number densities within the shock layer. An analysis was performed to estimate the uncertainty bounds of the determined properties. Nomenclature C = constant I = atomic line intensity, W /cm 3 L = optical path length, cm m = magni cation n = number density, cm 2 3 P = peak value of a band system, W /cm 2 mm 2 sr T = temperature, K W = area under a spectra, W /cm 2 sr x = distance from the model surface, mm u = characteristic temperature, K s = standard deviation Subscripts e = electronic r = rotational v = vibrational

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The high-pressure carbon monoxide (HiPco) technique for producing single-wall carbon nanotubes (SWNTs) is analyzed with the use of a chemical reaction model coupled with flow properties calculated along streamlines, calculated by the FLUENT code for pure carbon monoxide. Cold iron pentacarbonyl, diluted in CO at about 30 atmospheres, is injected into a conical mixing zone, where hot CO is also introduced via three jets at 30 degrees with respect to the axis. Hot CO decomposes the Fe(CO)5 to release atomic Fe. Then iron nucleates and forms clusters that catalyze the formation of SWNTs by a disproportionation reaction (Boudouard) of CO on Fe-containing clusters. Alternative nucleation rates are estimated from the theory of hard sphere collision dynamics with an activation energy barrier. The rate coefficient for carbon nanotube growth is estimated from activation energies in the literature. The calculated growth was found be about an order of magnitude greater than measured, regardless of the nucleation rate. A study of cluster formation in an incubation zone prior to injection into the reactor shows that direct dimer formation from Fe atoms is not as important as formation via an exchange reaction of Fe with CO in FeCO.