AEROBRAKE DESIGN STUDIES FOR MANNED MARS MISSIONS

The vehicle's mass tractions that must be devoted to the aerobrakes, i ncluding the heatshields, have been computed for a high-speed manned M ars entry of 8.6 km/s and with a 5 Earth g deceleration limit. Blunt, low lift-to-drag (L/D) ratio configurations with ballistic coefficient s (m/C(D)A) of 100 and 200 kg/m2 have been studied. In addition, a del ta-winged vehicle, with a medium L/D and a ballistic coefficient of 37 5 kg/m2, has been studied. Both insulative, radiatively cooled heatshi elds and ablators have been considered. After adding heatshielding and optimizing the structure, the aerobrakes' total mass fractions (heats hield plus aerobrake mass divided by the vehicle's total mass) varied from about 15 to 13% for ballistic coefficients of 100 and 200 kg/m2, respectively, for the blunt shapes and was slightly under 17% for the winged vehicle. The winged vehicle's aerobrake mass fraction was somew hat greater because the former's much higher ballistic coefficient res ulted in more intense heating, thus requiring more thermal protection. The aerobrakes' mass fractions range from less than to slightly over the 15% value that is considered to make aerobraking indisputably supe rior to propulsive braking.