Co-authors​ :

 Hiroya TANIGUCHI , Yutaro ARAI (JAPAN), Yasuo KOGO (JAPAN) 

The ablator is a thermal protection system for re-entry vehicles and is composed of carbon-based substrate and impregnated resin. During re-entry, components of the vehicles are exposed to harsh environment owing to severe aerodynamic heating. Ablator can protect the components during re-entry because the decomposition of resin is an endothermic reaction and gas evolved by decomposition of resin and oxidation of carbon prevents the increase of temperature for the components. Phenolic impregnated carbon ablator (PICA) composed of carbon felt and phenolic resin is well known as a typical ablator. On the other hand, mechanical erosion and low compressive strength are often considered problematic. Recently, the authors have fabricated phenol monolith, which is a porous phenolic resin with three dimensional networked structures by phase separation method. By the carbonization of phenol monolith, carbon monolith with similar networked structure have been obtained. Although the density of carbon monolith (0.34-0.51g/cm3) is higher than that of PICA (0.16-0.31g/cm3), the compressive strength of carbon monolith is ~60-270MPa and it is much higher than PICA (~0.25-8.5MPa). To fabricate an ablator utilizing the high strength of carbon monolith, we have prepared carbon monolith ablator (CMA) by impregnation of acrylic resin into carbon monolith. The ablation behavior of CMA has been evaluated by arc-wind tunnel test, which can simulate atmospheric re-entry environments and samples are exposed to high enthalpy flow during arc-jet. The surface of CMA was exposed to the high enthalpy flow with the heat flux of 2~6MW/m2 at 30s and the surface temperature reached ~3000℃. The result revealed that the ablation rate for CMA is similar or lower than PICA and CMA is an attractive candidate for an advanced thermal protection system. On the other hand, the internal temperature at 20mm depth from surface reached >350℃ during arc-jet test and the prevention of thermal conduction during arc-jet is required for an advanced ablator. In the present study, we have prepared ZrO2 nanoparticle-dispersed carbon monoliths (denoted as ZCM) with different content of ZrO2 particles as a substrate for an ablator because the melting point of ZrO2 is ~2700℃ and this endothermic process is expected to prevent the increase in surface temperature. The mechanical properties of ZCM have been evaluated by compression test. Furthermore, ablation behaviors of ZCM also have been evaluated by arc-jet facility. In this presentation, the relationship between ZrO2 content, mechanical properties, and ablation behavior of ZCM will be discussed.