High Heat Flux Block Ablator-In-Honeycomb Heat Shield Using Ablator/Aerogel-Filled Foam

Ultramet and ARA Ablatives Laboratory previously developed and demonstrated advanced foam-reinforced carbon/phenolic ablators that offer substantially increased high heat flux performance and reduced weight relative to conventional ablators. The structure consisted of an ablator-filled foam front surface backed by Ultramet's highly insulating aerogel-filled foam. Arcjet testing was performed at NASA ARC to heat flux levels exceeding 1000 W/cm2, with the results showing a significantly reduced ablation rate compared to conventional chopped fiber ablators, and ablation behavior comparable to FM5055 at just one-third the density. It is apparent that the foam helps retain the char layer by physical reinforcement and/or that the network of interconnected passages allows pyrolysis gases to escape with less disruption of the char layer. In 2008, NASA ARC contracted ARA to perform initial development of a new TPS design involving integration of fully cured mid-density ablator blocks within a structural honeycomb reinforcement. The block ablator-in-honeycomb heat shield is envisioned to provide high atmospheric entry reliability due to the structural attachment integrity provided by the honeycomb lattice in the ablative material layer. Any ablator failure such as cracking or char layer delamination is anticipated to occur within individual honeycomb cells rather than over large areas. The architecture is anticipated to have broad potential application for missions that involve large-vehicle entries into planetary atmospheres. Multiple block layers can be used within individual honeycomb cells, such as an outer high-density ablator layer with lightweight insulation underneath. This concept was analytically shown to have significant mass advantages over a traditional through-thickness ablator approach. Ultramet's ablator/aerogel-filled foams have very good potential for this application, and the Ultramet-ARA team will establish initial feasibility in this project.