Feasibility and Performance Analysis of Neptune Aerocapture Using Heritage Blunt Body Aeroshells (Pre-print)

Abstract

Large navigation and atmospheric uncertainties have historically driven the need for a mid-lift-to-drag L/D vehicle with L/D of 0.6--0.8 for aerocapture at Neptune. Most planetary entry vehicles flown to date are low-L/D blunt-body aeroshells with L/D less than 0.4. The lack of a heritage mid-L/D aeroshell presents a major hurdle for Neptune aerocapture, as the development a new entry vehicle incurs significant time and investment. Techniques which may allow Neptune aerocapture to be feasible using heritage low-L/D blunt-body aeroshells are investigated that obviate the need for mid-L/D aeroshells. A navigation study is performed to quantify the delivery errors, and a new guidance algorithm with onboard density estimation is developed to accommodate large atmospheric uncertainties. Monte Carlo simulation results indicate that the reduced navigation uncertainty and improved guidance scheme enable a blunt-body aeroshell with L/D = 0.3--0.4 to perform aerocapture at Neptune. The expected heat rate is within the capabilities of existing thermal protection system materials.