Sizing and Margins Assessment of Mars Science Laboratory Aeroshell Thermal Protection System

Abstract

The methodology employed for the thermal design and margins assessment of the Mars Science Laboratory aeroshell thermal protection system is reviewed. A new thermal margins policy was developed in the course of this work that provides additional rigor over previous methods. Because of a late change of thermal protection materials from the heritage super lightweight ablator 561V to phenolic impregnated carbon ablator, the design of the heat shield followed a nontraditional path in which the flight thickness was selected based on a mass (rather than thermal) limit. The material switch was followed by detailed thermal analyses that demonstrated that the baselined thickness was sufficient to provide adequate thermal protection to the vehicle without violating design requirements during a 3-sigma worst-case entry condition. The backshell material thickness was also finalized before the thermal sizing was completed, and the resulting analysis showed that there was more than sufficient material on the backshell. The parachute cone cover and backshell interface plate were the only major thermal protection system elements that followed a standard design process. Thermal sizing was performed for acreage and special features on the cone cover and interface plate, and the hardware was manufactured according to those analyses.