The hypersonic transitional ow aerodynamics of the Mars Microprobe capsules are simulated with the direct simulation Monte Carlo method. Calculations of axial, normal, and static pitching coef cients were obtained over an angle-of-attack range comparable to actual ight requirements. Comparisons are made with modi ed Newtonian and free-molecular ow calculations. Aerothermal results were also obtained for zero incidence entry conditions. The current aerodynamic results are shown to be in excellent agreement with Navier–Stokes results for small Knudsen number conditions. Peak heating conditions occur under rare ed conditions where the heating becomes a strong function of assumptions concerning surface catalytic activity.