(Georgia Institute of Technology, 2019-06-10)
Sidor, Adam Thomas
Conformal ablators, first introduced in the early 2000s under the NASA Hypersonics Project, are a type of rigid ablative thermal protection system that uses flexible, rather than rigid, fibrous substrates. These materials are impregnated with resin in a mold to yield a part that is close to the final geometry and requires little post-process machining (a near net shape part). The lack of fiber connectivity through the thickness enables the TPS to tolerate larger strains than comparable rigid substrate ablators facilitating larger tiles and installation on most aeroshells without strain isolation. Reduced part count and simplified integration drive reductions in labor, cost and complexity –advancements which are enabling for planetary and human missions. Conformal ablators are currently fabricated using an open liquid impregnation process adapted from a technique developed for Lightweight Ceramic Ablators, such as Phenolic Impregnated Carbon Ablator, which leads to design and manufacturing inefficiencies. This work advanced a new manufacturing technique for conformal ablators, vacuum infusion processing, that reduces resin consumption and streamlines clean up. The closed process also eliminates an expensive atmosphere-controlled oven or vacuum chamber. A design methodology, centered around a simulation of the mold filling process, was developed to tailor a conformal ablative heatshield to vacuum infusion processing. A constitutive model, combining properties of individual components, was formulated to estimate the properties of the composite TPS material. The methodology leverages this model, integrated with material selection, tile layout, and the mold filling simulation, to automate a conceptual conformal heatshield design. The approach allows rapid iteration on TPS composition and manufacturing constraints.
(Georgia Institute of Technology, 2019-05-03)
Ali, Hisham K.
Proposed missions such as a Mars sample return mission and a human mission to Mars require landed payload masses in excess of any previous Mars mission. Whether human or robotic, these missions present numerous engineering challenges due to their increased mass and complexity. To overcome these challenges, new technologies must be developed, and existing technologies advanced. Resource utilization technologies are particularly critical in this effort. This thesis aims to study the reclamation and harnessing of vehicle kinetic energy through magnetohydrodynamic (MHD) interaction with the high temperature entry plasma. Potential mission designs, power generation and power storage configurations are explored, as well as uses for the reclaimed energy. Furthermore, the impact and utility of MHD flow interaction for vehicle control is assessed. The state of the art for analysis of MHD equipped planetary entry systems is advanced, with the specific goals including: development of performance analysis capabilities for potential MHD equipped systems, identification of systems or configurations that show promise as effective uses of MHD power generation, experimental designs for developing technologies applicable to MHD power generation systems, assessment of MHD flow interaction and beneficial use for entry vehicle control through drag modulation, and increasing the technology readiness level of MHD power generation architectures for entry, descent and landing.