Effect of thermally expanding surfaces on aerodynamic roll torques for cones.

An experimental and analytical study has been made of the aerodynamic roll torque on smoothly ablating, spinning cones. The tests, conducted in the Ames 3.5-Foot Hypersonic Wind Tunnel, indicated that the smoothly ablating model rolling at 0 deg angle of attack experiences roll damping, but when rolling at angle of attack an aerodynamic torque in the direction of spin arises if thermal expansion of the body surface occurs. An analysis of the spinning body at angle of attack is included to show how the relative importance of the ablator thermal expansion and the surface recession rate determines whether the motion is damped or undamped.