Ballute Entry Systems for Lunar Return and Low-Earth-Orbit Return Missions

Abstract

This study investigates the feasibility of using ballutes for Earth entry at both lunar- and low-Earth-orbit return velocities. Multiple entry strategies were investigated using analysis methods suitable for conceptual design and assuming an Apollo-derived entry vehicle. Primary ballute size drivers are the thermal limitations and areal densities of the ballute material. Lunar-return entries that jettison the ballute after achieving low-Earth-orbit conditions were shown to reduce heating rates to within reusable thermal protection system limits. Deceleration was mitigated to approximately 4 g along a lunar-return trajectory when a moderate amount of lift was applied subsequent to ballute jettison. Investigation of a lower mass lunar-return cargo variant of the Crew Exploration Vehicle was shown to reduce ballute system mass and size. Ballute system mass as a percentage of the total entry mass was shown to be relatively independent of the entry mass for the range of lunar-return missions evaluated. However, material requirements indicate that continued technology development may be required for lunar-return system viability. Missions aimed at augmenting existing systems to provide downmass capability from the International Space Station showed promising results in terms of entry loads, required material areal densities, and ballute system mass and size.