A sketch of the baseline nozzle contour is shown in Figure 2 . The supersonic area ratio is 100, and the subsonic area ratio is 35. Because the exit radius was fixed in all of the analyses, d controls the shape of the divergent portion of the nozzle. High values of d produce a bell-shaped contour while low values produce a more conical contour. The chamber temperature of 6,100deg.
R is the upper limit for a hafnium-carbide absorber.
The chamber pressure of 50 psia is limited by the yield stress of this material at the elevated temperature.6 The radiatively-cooled nozzle wall is maintained at a constant temperature of 2460deg. This combination of area ratio and chamber conditions produces an ideal, inviscid thrust of 1.05 lbf with the baseline nozzle. Several higher-order upwind and central differencing schemes can be chosen for spatial discretization. Various turbulence models and finite rate chemistry model options are also available in the code. An existing FDNS subprogram was modified to allow the user to specify the nozzle geometry, numerical grid, and calculate initial conditions based on an isentropic flow field.