Pitch Control During Autonomous Aerobraking for Near-Term Mars Exploration

Abstract

Conventional aerobraking requires propellant to dump the spacecraft's angular momentum and to maintain attitude control during the atmospheric flythrough. We consider how reaction wheels can be used to control the spacecraft's pitch during each atmospheric flythrough and to reduce angular momentum simultaneously. Control laws are developed for minimum onboard instrumentation (where the only state information are the angular rates of the spacecraft and the reaction wheels) to compensate for large variations in entry time and atmospheric density. Simulations indicate that pitch attitude and angular momentum can be controlled with reaction wheels alone, thus saving precious propellant while significantly increasing the timing margin for sequencing.