Deceleration control system for aerobraking and skipout to orbit at Mars.

Abstract

Aerobraking into a planetary atmosphere generally involves less weight penalty than thrust deceleration. This investigation determines if a deceleration- command roll control system on a lifting body can provide entry corridors for the aerobraking maneuver at Mars consistent with achievable approach guidance accuracy. Results are presented varying Mars atmosphere, L/D, nte/CnA., control system parameters, and entry speed. For example, with Fe = 7 km/sec and a thin atmosphere (VM — 8), the corridor varies from 50 km at L/D = 0.3 to 300 km at L/D = 1.0. If the atmosphere is unknown a priori (within presently accepted limits) minimum L/D somewhat greater than 0.3 is required. Thus, for lifting capsules the control system provides corridors requiring onboard guidance, whereas for lifting bodies (L/D > 1) Earth-based guidance might be adequate. System effectiveness is relatively insensitive to control parameter variation. Nomenclature A = vehicle reference area a = deceleration B = radial distance from planet center to hyperbolic asymptote (impact parameter) CD, CL = drag and lift coefficients, respectively c = feedback coefficient ge = acceleration of gravity at Earth surface