Manned exploration missions to Mars may involve aerodynamic braking from hyperbolic approach speeds both at Mars and Earth. Atmospheric penetration at the anticipated approach velocities will subject entry vehicles to extreme thermal environments. The associated heat shielding requirements will be of major importance in selecting an optimum mission course. In the hyperbolic entry situation, complicated interactions exist among the aerothermal phenomena that are commonly neglected or at least treated independently. Significant advances in the aerothermal technology are required to ensure efficient and reliable heat-shield designs. The problem of defining thermal protection requirements for Mars-mission entry vehicles was studied by Lockheed Missiles Space Company for NASA under Contract NAS 2-1798. This report describes the scope of the study and briefly summarizes the principal results. A comprehensive review of the investigation is presented in the final report.