Within its Entry, Descent and Landing Systems Analysis (EDL-SA) Project, NASA has been evaluating the technology investments required to enable human and large payload missions to Mars. In FY09 study was focused on Exploration-class cargo or crewed missions requiring 10 to 50 metric tons of landed payload. One of the deceleration concepts to achieve this goal employed a large Hypersonic Inflatable Aerodynamic Decelerator (HIAD). The HIAD would execute both aerocapture and atmospheric entry maneuvers at Mars and would therefore require a Thermal Protection System (TPS) capable of enduring dual heat pulse environments at high heat flux. This would most likely require an ablative TPS. At the time of the study, no flexible materials existed that met the estimated HIAD requirements. Based on current research, estimated flexible ablator material properties were created and used for a TPS sizing analysis of a dual heat pulse HIAD. These properties were used to perform HIAD TPS sizing analysis and additional trade studies. These studies demonstrate that the development of flexible ablators will lead to reasonable TPS masses for Hypersonic Inflatable Aerodynamic Decelerators.
NASA has been recently updating design reference missions for the human exploration of Mars and evaluating the technology investments required to do so. The first of these started in January 2007 and developed the Mars Design Reference Architecture 5.0 (DRA5). As part of DRA5, Thermal Protection System (TPS) sizing analysis was performed on a mid L/D rigid aeroshell undergoing a dual heat pulse (aerocapture and atmospheric entry) trajectory. The DRA5 TPS subteam determined that using traditional monolithic ablator systems would be mass expensive. They proposed a new dual-layer TPS concept utilizing an ablator atop a low thermal conductivity insulative substrate to address the issue. Using existing thermal response models for an ablator and insulative tile, preliminary hand analysis of the dual layer concept at a few key heating points indicated that the concept showed potential to reduce TPS masses and warranted further study. In FY09, the followon Entry, Descent and Landing Systems Analysis (EDL-SA) project continued by focusing on Exploration-class cargo or crewed missions requiring 10 to 50 metric tons of landed payload. The TPS subteam advanced the preliminary dual-layer TPS analysis by developing a new process and updated TPS sizing code to rapidly evaluate mass-optimized, full body sizing for a dual layer TPS that is capable of dual heat pulse performance. This paper describes the process and presents the results of the EDL-SA FY09 dual-layer TPS analyses on the rigid mid L/D aeroshell. Additionally, several trade studies were conducted with the sizing code to evaluate the impact of various design factors, assumptions and margins.
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