Entry flight aerodynamics from Apollo mission AS-202

Abstract

Inertial-platform accelerations and attitudeswere used with trajectory data to calculate the flight aerodynamic characteristics of the entry configuration (command module).The flight results, in the form of aerodynamic angles, force coefficients, and coefficient ratios, were compared with trimmed wind-tunnel data predictions and with wind-tunnel data adjusted to the flight angle of attack.The comparisons showed the flight trim angle of attack to be higher than predicted at the initial high-Machnumber, low-Reynolds-number entry conditions, resulting in a correspondingly low (18 percent) liftto-drag ratio.Both flight angle of attack and liftto-drag ratio were essentially linear down to the high -supersonic -Mach-number region where there was good agreement with the predicted values.The areas of poor agreement were caused by poor trimangle predictions and not by poor wind-tunnel resultant force data. .'D, G aerodynamic lift coefficient relative to the ground, perpendicular to VA, and in the orbital plane 'L, G 'L, RG ' N 'N, R 'Y 'Y, G d 2 y, G resultant, or total, aerodynamic l i f t coefficient, -*z qms aerodynamic body axis normal-force coefficient,aerodynamic body axis resultant, o r total, normal-force coefficient, 2 Mach number.The flight total normal-force coefficient is very scattered, showing fair agreement (varying up to 15 percent) with hybrid data for the entire flight.