Trajectory and Attitude Simulation for Mars Aerocapture and Aerobraking

A combined strategy of aerocapture and aerobraking is presented to achieve a near-circular orbit, starting from ah yperbolic trajectory, without requiring an orbital insertion burn. Aerothermodynamic force, moment, and heat flux calculations employ a Maxwellian free-molecular flow model, with Knudsen-number-based interpolations for the transition regime. The six-degree-of-freedom motion model, including quaternion-based attitude dynamics, allows stability and sensitivity analyses for the atmospheric passes. A spacecraft model with two large panels suitable for Earth aerocapture is considered. Minor orbit-correction burns at the apoapsis are provided after each pass for manipulating the periapsis for the next pass to meet the desired aerobraking corridor. It is observed that an initial orbit of eccentricity 1.6 and relative entry velocity of 12 km/s at 300-km altitude can be reduced to an orbit with an eccentricity of 0.02, using a total of six atmospheric passes, without exceeding the peak convective heat flux constraint for the spacecraft or requiring an orbit insertion burn. This result has considerable importance fo rl ow-Earth-orbit space-tug captures and Mars missions, wherein the strategy proposed will lead to significant savings in spacecraft propellant mass during the orbit insertion and, subsequently, orbit circularization.