**4.2 Flow field over vehicle at angle of attack**

Figure 10 shows the Mach contour plots over the OREX and Apollo modules. For the sake of brevity we are presenting windward and leeward sides flow field over OREX with smooth and without smooth shoulder, ARD, Apollo II and spherical-cone configurations are shown at M = 10.0 and at angle of attack 10.0 degree in Fig. 10. The Mach contour plots display the flow field in the windward and the leeward side of the capsules. A shock wave stands in front of the reentry blunt body and forms a region of subsonic flow around the stagnation region. Characteristic features of the flow field around the blunt body at high speed, such as bow shock wave ahead of the capsule and the expansion waves on the shoulder of the capsules. The bow shock wave follows the body contour and the fore body is entirely subsonic up to the corner tangency point of the ARD, the Apollo and the OREX where the sonic line is located. In the case of the spherically blunted cone-flare module, the sonic line is located at the junction of the sphere cone as seen in the Mach contour plots. The flow expands at the base corner. The flow field over the reentry modules became complicated due to the presence of corner at the shoulder and the base shell of the capsule as delineated in the Mach contour plots. Detailed flow field analysis is presented in (Mehta 2007). It is found at the transonic flow cases that a steady state solution could not be achieved due to unsteady nature of the base flow. Table 5 shows the aerodynamic drag numerically computed for COMET and Beagle-2 reentry modules.

Fig. 10. Mach contour plots over reentry capsules at M = 6.0 and angle of attack 5 deg.


Table 5. Numerically computed aerodynamic drag coefficient.
