(Georgia Institute of Technology, 2011-06)
Kazemba, Cole D.; McGuire, Mary Kathleen; Howard, Austin; Clark, Ian G.; Braun, Robert D.
With the goal of landing high-mass cargo or crewed missions on Mars, NASA has been developing new thermal protection technologies with enhanced capability and reduced mass compared to traditional approaches. Two examples of new thermal protection system (TPS) concepts are dual layer and flexible TPS. Each of these systems introduces unique challenges along with potential performance enhancements. Traditional monolithic ablative TPS, which have been flown on every Mars robotic mission to date, use a single layer of ablative material. The new dual layer TPS concepts utilize an insulating layer of material beneath an ablative layer to increase efficiency and save mass. A study was conducted on the dual layer system to identify sensitivities in performance to uncertainties in material properties and aerothermal environments. A performance metric which is independent of the system construction was developed in order to directly compare the abilities and benefits between the traditional, dual layer and eventually, flexible systems. Using a custom MATLAB code enveloping the Fully Implicit Ablation and Thermal Response Program (FIAT), the required TPS areal mass was calculated for several different parametric scenarios. Overall TPS areal mass was found to be most sensitive to the constraining allowable temperature in each system and aerothermal heat transfer augmentation (attributed here to material surface roughness). From these preliminary results it was found that the nominal dual layer TPS construction investigated could produce improvements over a traditional TPS in the specified performance metric between 14-36%, depending on the flight environments and total integrated heat load expected.