Effects of Water Phase Change on the Material Response of Low-Density Carbon-Phenolic Ablators

During atmospheric entry, the shock layer in front of a spacecraft converts a large amount of kinetic energy into heat. To protect the vehicle from this extreme heat, thermal protection systems (TPSs) are used. One option for TPS material is a low-density ablator, made of a porous carbon-fiber preform impregnated with a phenolic resin. Through various complex mechanisms, this class of material uses the incoming heat to trigger chemical reactions that will reduce the surface heat flux [1] as well as reduce the conversion of energy to thermal energy [2,3]. The phenolic impregnate carbon ablator (PICA) [4] developed by NASA belongs to this class of materials. PICS was successfully used on various entry vehicles such as the Stardust Sample Return Capsule [5], SpaceX's Dragon spacecraft (using a variant branded PICA-X) [6], and more recently the Mars Science Laboratory (MSL) entry spacecraft [7].