Evaluation of Main Parameters in Re-Entry Trajectories

The selection of the descending path for re-entry vehicles presents serious challenges for the designer. Basic requirements in terms of flight mechanics, dealing with initial and terminal conditions, have to match strict requirements related to the survivability of the re-entering body, in terms of structural integrity as well as in terms of thermal input and accepted temperature raise. The possibility of aero-braking assistance, allowed only if the targeted celestial body is surrounded by an atmosphere, increases the degrees of freedom available to the designer. The paper focuses on this special case, looking for an evaluation of the critical parameters (maximum load factor, maximum thermal ux) with respect to the flight dynamics of the trajectory. The initial step is represented by a procedure proposed by Broglio to approximately identify the initial conditions for suitable descent trajectories as function of a limited number of parameters. The solutions do not depend explicitly on the shape of the body, and the approximations involved are quite reasonable, as shown by a comparison with purely numerical integration. The present papers builds on this approach by modifying the analytical process to better handle the ight phases close to the deceleration peak, which are the most critical ones. Some examples are included to show the advantages of the proposed approach