Aerocapture Performance Analysis for a Neptune Mission Using a Heritage Blunt-Body Aeroshell

Abstract

The large navigation and atmospheric uncertainties at Neptune have historically driven the need for a mid-lift-to-drag L/D vehicle with L/D of 0.6--0.8. All 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 long pole for Neptune aerocapture, as the development and testing of a new entry vehicle incurs significant cost, risk, and time. Techniques which may allow Neptune aerocapture to be performed using heritage low-L/D blunt-body aeroshells are investigated, and obviate the need for mid-L/D aeroshells. A navigation study is performed to quantify the delivery errors, and a new guidance algorithm with on-board density estimation is developed to accommodate atmospheric uncertainties. Monte Carlo simulation is used to analyze aerocapture performance of a vehicle with L/D = 0.4. One hundred percent of the cases captured successfully and show a 99.87% probability of achieving the desired science orbit with a total of 396 m/s propulsive Delta V budget, even with worst-case atmospheric uncertainties.