Analysis of Mars aerocapture with a deployable drag device

Aerocapture is a technique to perform orbital insertion by transforming an orbit from hyperbolic to elliptical by a single pass through the atmosphere of a planet. The possibility of inserting a probe in orbit around Mars using the atmospheric drag instead of a Mars Orbit Insertion manoeuvre, allows to save resources or increase the payload mass fraction. The main obstacle to the success of an aerocapture manoeuvre is represented by the high uncertainties in the parameters from which it depends. This explains why this technique has never been applied in a real mission. The objective of this work is to investigate the feasibility of aerocapture at Mars with a deployable drag device. The analysis is conducted in the framework of the feasibility study of the Small Mission to MarS (SMS) project, started within ESA's General Support Technology Programme (GSTP). The uncertainties that make aerocapture a risky manoeuvre derive mainly from Mars atmosphere uncertainties and navigation errors. The innovative design of the deployable drag device, whose opening and closing might be also modulated in flight, allows to achieve very low values of the ballistic coefficient, suitable for decelerating the spacecraft within the atmosphere for aerocapture or for entry, descent and landing. In the paper, a parametric analysis of the aerocapture performance is carried out by taking into account a wide range of uncertainty levels in Mars atmospheric density profile and the uncertainties in the value of the ballistic coefficient. Then, an application to a real mission scenario is conducted, by also considering an uncertainty in the targeting manoeuvre performed at Mars sphere of influence. The analyses indicate the strong influence of the atmospheric density and ballistic coefficient uncertainties that significantly restrict the solution space and limit solution distribution and continuity. However, results show that viable solutions for aerocapture can still be identified.