This project is performing preliminary development of a Multifunctional Hot Structure (HOST) heat shield for planetary entry. Results of this development will determine the feasibility of the HOST heat shield to provide benefits over the conventional approach. Preliminary results indicate that both mass and volume savings are achievable with the HOST concept compared to a traditional heat shield design. The Multifunctional Hot Structure (HOST) heat shield concept is unique in integrating the function of the thermal protection system (TPS) with the primary load carrying structural component. An advanced carbon-carbon material system has been evaluated for the load carrying structure, which will be utilized on the outer mold line (OML) surface of the heat shield, and thus will operate as a hot structure exposed to the severe aerodynamic heating associated with planetary entry. Flexible, highly efficient blanket insulation has been sized for use underneath the hot structure to maintain desired internal temperatures. The approach is to develop a preliminary design to demonstrate feasibility of the concept. The preliminary results indicate that the concept has the potential to save both mass and volume with significantly less recession compared to traditional heat shield designs, and thus provide potential to enable new planetary missions. Initially, an earth return mission was evaluated using a spherical section type heat shield concept for a traditional earth entry capsule. Then a Mars entry sphere-cone concept was evaluated. Currently, a Mid-L/D concept for Mars entry is being studied. Results of this study should demonstrate the feasibility and advantages of the HOST concept, which may enable future planetary missions.