Study of Mechanical and Thermal Behavior of Polymeric Ablator Using MD

The thermal protection materials used for spacecraft heat shields are subjected to various thermal and mechanical loads during an atmospheric entry which can threaten the structural integrity of the system. This paper describes the development of a molecular dynamics approach to understand the mechanical and thermal behavior of high temperature polymers. One such material PICA has successfully flown on the Stardust spacecraft and is the TPS material chosen for the Mars Science Laboratory (MSL) and SpaceX Dragon spacecraft. Although such polymers have good structural properties at moderate temperature,they became structurally weak at extreme region of temperature and loads. In order to thoroughly understand the response of materials under extreme mechanical and thermal loads it is necessary to investigate atomistic mechanisms of deformation and pyrolysis. MD Simulations are presented to compute the thermal expansion coefficients, stress-strain response,to determine the pyrolysis gas composition entering the char layer from the virgin material, and to identify the main reaction pathways for the interaction between the pyrolysis gases at temperature varying from 500-1500K.