DRAG AND STABILITY OF VARIOUS MARS ENTRY CONFIGURATIONS

Abstract

An experimental free-flight program has been conducted in the ballistics ranges at the U. S. Naval Ordnance Laboratory (NOL) to investigate the aerodynamic characteristics of various blunt forebody configurations for possible use as Mars entry probes. These configurations were a blunted 120-deg cone, a blunted 140-deg cone, a spherical segment and two tension shells of different slenderness. The drag coefficient and static and dynamic stability coefficients were determined in air and CF4 atmospheres for Mach numbers from 0.6 to 13 and Reynolds numbers between 3 × 104 and 3.3 × 106. It was found that the drag coefficients for the 140-deg cone, the spherical segment and the blunter tension shell configurations in air were higher than for the 120-deg cone and the more slender tension shell. In a CF4 atmosphere, the tension shell shapes and the 140-deg cones had larger increases in the drag coefficients than the other configurations over their corresponding values in air. The dependence of the drag coefficient on the amount of yaw during the flight has been determined for each configuration. All configurations were statically stable in both atmospheres. The dynamic stability coefficients indicate a stabilizing effect throughout the supersonic Mach number range in air, while destabilizing coefficients were measured in the transonic region and in some tests in CF4.