Trajectory Optimization of Two-phase Mars Aerocapture Using the hp-Adaptive Pseudospectral Method

The research on aerocapture and aeromaneuver for the Mars mission has long been studied due to its fuel advantage. In this paper, a two-phase aerocapture insertion scheme is proposed, which consists of two atmospheric flights and two Kepler orbital flights. On this basis, the optimal control problem of two phases is constructed with the bank angle, the impulse at the apoapsis and the insertion impulse as the control variables. The detailed derivation of the complex interior point constraint and the endpoint constraint is given. After that, the optimization problem is solved using pseudospectral method numerically. Compared with the traditional single-phase aerocapture scheme, it is found that the two-phase aerocapture has lower peaks of heating rate, dynamic pressure, and load factor, which means lower protection cost and fuel consumption cost for Mars mission.