Enhanced Aerocapture Guidance Framework Using Augmented Bank Angle Modulation

Aerocapture involves converting a hyperbolicapproach trajectory into a captured orbit utilizing the aerodynamic forces generated via a single atmospheric pass. Aerocapture guidance systems must be robust to significant environmental variations and modeling uncertainty, particularly regarding atmospheric properties and delivery conditions. Recent work has shown that controlling both bank angle and angle of attack, a strategy called augmented bank angle modulation (ABAM), can improve robustness to entry state and atmospheric uncertainties. This work derives optimal control solutions for an aerocapture vehicle using ABAM. First, the problem is formulated using a linear aerodynamic model, and closed-form control profiles are derived using Pontryagin’s minimum principle. To increase modeling fidelity, a quadratic aerodynamic model is considered, and the solution is obtained directly using the optimality conditions. Both formulations are solved numerically using Gauss pseudospectral methods to validate the analytic solutions. This work then introduces a novel aerocapture guidance algorithm, augmented bank angle modulation guidance plus (ABAMGuid+), which indirectly minimizes propellant usage by mimicking the structure of the optimal control solution, enabling efficient guidance by reducing the problem complexity. Extensive Monte Carlo simulations of a Uranus aerocapture mission demonstrate that ABAMGuid+ increases capture success rates and reduces postcapture propellant requirements relative to previous methods.