The effect of the ablation recession on the heat flux near a rudder gap interaction region was studied. High temperature thermal-chemical non-equilibrium numerical simulation was conducted for a plate-rudder configuration under typical hypersonic flow condition. The flow and aeroheating mechanism was analyzed for the rudder gap interaction region. The shape change caused by ablation recession was modeled and its effect on the flow structure and aeroheating mechanism was studied. Results indicated that the ablation recession changed the pressure distribution in the interaction region and decreased the spanwise pressure gradient

which inhibited the thickness reduction of the boundary layer by the cross-flow

and led to decrease of the heat flux in the interaction region. This heat flux decrease value was intensified as the ablation recession depth increased

which can reach 28.9% at a 5 mm recession depth.