Comparison of Lift and Drag Modulation Control for Ice Giant Aerocapture Missions

TL;DR

This paper compares lift and drag modulation control methods for ice giant aerocapture missions, highlighting their advantages and challenges in terms of entry corridor width, control authority, and thermal conditions.

Contribution

It provides a detailed analysis of lift versus drag modulation control strategies, emphasizing their implications for future outer Solar System missions.

Findings

Lift modulation nearly doubles entry corridor width compared to drag modulation.

Lift modulation allows continuous trajectory adjustment during flight.

Drag modulation offers more benign aero-thermal conditions but less post-jettison control.

Abstract

Aerocapture is an orbit insertion technique which uses atmospheric drag from a single pass to decelerate a spacecraft. Compared to conventional propulsive insertion, aerocapture can impart large velocity changes to the spacecraft with almost no propellant. At the far reaches of the outer Solar System, the ice giants remain the last class of planets to be explored using orbiters. Their enormous heliocentric distance presents significant mission design challenges, particularly the large $\Delta$V required for orbit insertion. This makes aerocapture an attractive method of orbit insertion, but also challenging due to the comparatively large navigation and atmospheric uncertainties. The present study performs a comparison of the lift and drag modulation control and their implications for future missions. Lift modulation provides nearly twice the entry corridor width as drag modulation, and can thus accommodate larger uncertainties. Lift modulation offers continuous control throughout the flight enabling it to adjust the trajectory in response to the actual density profile encountered. Drag modulation offers much more benign aero-thermal conditions compared to lift modulation. With drag modulation, there is no control authority after the drag skirt jettison making the vehicle more susceptible to exit state errors from density variations encountered after the jettison event.