Single-Stage Drag Modulation GNC Performance for Venus Aerocapture Demonstration

Abstract

The future of space exploration is heavily reliant on innovative Entry, Descent, and Landing (EDL) technologies. One such innovation involves aeroassist technology, mainly aerocapture, which involves a single pass through the upper atmosphere of a planetary body from an incoming hyperbolic trajectory to capture into an elliptical orbit. Previous aerocapture guidance studies focused on lift modulation using reaction-control system (RCS) thrusters. This paper investigates the guidance law performance of drag-modulated aerocapture for a single, discrete, jettison event. Venus is selected as the target planet to observe performance in the most challenging environment. Three different guidance algorithms are studied, including a deceleration curve-fit, a pure state-predictor, and a numerical predictor-corrector utilizing both bisection and Newton-Raphson root-finding methods. The performance is assessed using Monte Carlo simulation methods. The deceleration curve-fit achieves a capture rate of over 55% for a 2000km apoapsis target and 1000km tolerance. For an entry flight-path-angle (EFPA) of -5.2°, the predictive algorithm achieves a 50% capture rate within 100km and over 90% within 250km. Finally, at the same EFPA the NPC using a Newton method attains >80% capture rate for all β₂/β₁ > 6 within 100km tolerance targeting 10000km. The largest source of error for these systems is the atmospheric density variation downstream of the jettison event.