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Continuous wave hydrogen-fluoride lasers designed to yield high mass to power utilization efficiency contain active medium inhomogeneities which have the potential of introducing large correlated medium aberrations.Reduction of the magnitude of the correlated medium aberrations by proper orientation of adjacent laser nozzle modules are investigated using geometric and diffractive wave optics analysis.Two significantly different high mass efficiency designs were examined, the axisymmetric and hypersonic wedge.Detailed gas dynamic calculations were made to estimate the index of refraction variations in these three -dimensional mixing, reacting and lasing flowfields. The geometric and diffractive wave analyses were performed to establish the optical path differences (OPD's) introduced by multiple rows of the basic nozzle array unit. Comparisons between the geometric and diffractive analyses showed that the geometric treatment would place an upper limit on the OPD's to be expected from multiple nozzle arrays. Alignment of rows of the axisymmetric nozzle array with the lasing axis was found to have a catastrophic effect on the beam quality of the device. However, by properly skewing the rows of nozzles, it was possible to reduce the degradation in beam quality.Similarly, worst case orientations for the hypersonic wedge array were identified and skewing of the trailing edge of the hypersonic wedge with respect to the optical axis was shown to significantly minimize beam quality degradation.

Solutions of the second order longitudinal curvature boundary layer equations near the stagnation point of a two-dimensional circular cylinder are presented. Four cases corresponding to 1 first order locally similar solutions, 2 first order nonsimilar solutions, 3 second order locally similar solutions, and 4 second order nonsimilar solutions are considered. For each of the four cases, results for four different altitudes are given. The only second order effect considered is longitudinal curvature. Based on the numerical results, it is concluded that similarity and curvature assumptions can alter the skin friction calculations significantly. The heat transfer calculations are much less sensitive to the various assumptions, at least for the cases studied in this paper.