Abstract: Thermal protective materials suitable for use in a spacecraft include a substrate, such as carbon fibers or carbon felt, and cyanate ester resin or phthalonitrile resin, and cross-linkers. These thermal protective materials have a density of about 0.2 to about 0.35 g/cm3. Methods of making the thermal protective materials include mixing a cyanate ester resin or a phthalonitrile resin and a cross-linker to result in a resin solution, infusing the resin solution into a substrate, and curing the resin to result in the thermal protective material.

Abstract: A thermal protection system (TPS) for a space vehicle that undergoes partial or full ablation when the TPS is exposed to severe heating during entry into a planetary atmosphere. A first layer includes at least one of carbon, phenolic, silica, alumina and another oxide, low thermal conductivity fibers and yarns connecting two or more first layer sub-layers, is recession-resistant and has reduced porosity. A second layer has a smaller fiber fraction, reduced thermal conductivity and reduced density, and serves as a thermal insulator. The first layer may have partial or full insertion of a resin, or may have a surface densified, recession-resistant sub-layer. Values of a first subset of as many as eight environmental parameters can be used to characterize the space vehicle mission. A second subset of TPS parameters for the system is evaluated to identify whether an ablator system with these TPS values can survive the conditions associated with the first subset of environmental parameters.

Abstract: A method for preparing a flexible low-density thermal protection material, the method comprising providing a flexible substrate and a pyrolizable material impregnated therein. The thermal protection material remains flexible after impregnation and continues to remain flexible when the pyrolizable material is fully pyrolized.

Abstract: A low-density article comprising a flexible substrate and a pyrolizable material impregnated therein, methods of preparing, and devices using the article are disclosed. The pyrolizable material pyrolizes above 350 C and does not flow at temperatures below the pyrolysis temperature. The low-density article remains flexible after impregnation and continues to remain flexible when the pyrolizable material is fully pyrolized.

Abstract: A method for increasing density of a region of a porous, phenolic bonded (“PPB”) body adjacent to a selected surface to increase failure tensile strength of the adjacent region and/or to decrease surface recession at elevated temperatures. When the surface-densified PPB body is brought together with a substrate, having a higher failure tensile strength, to form a composite body with a PPB body/substrate interface, the location of tensile failure is moved to a location spaced apart from the interface, the failure tensile strength of the PPB body is increased, and surface recession of the material at elevated temperature is reduced. The method deposits and allows diffusion of a phenolic substance on the selected surface. The PPB body and the substrate may be heated and brought together to form the composite body. The phenolic substance is allowed to diffuse into the PPB body, to volatilize and to cure, to provide a processed body with an increased surface density.

Abstract: A tough ultra-high temperature ceramic (UHTC) composite comprises grains of UHTC matrix material, such as HfB2, ZrB2 or other metal boride, carbide, nitride, etc., surrounded by a uniform distribution of acicular high aspect ratio reinforcement ceramic rods or whiskers, such as of SiC, is formed from uniformly mixing a powder of the UHTC material and a pre-ceramic polymer selected to form the desired reinforcement species, then thermally consolidating the mixture by hot pressing. The acicular reinforcement rods may make up from 5 to 30 vol % of the resulting microstructure.

Abstract: Spacecraft heat shields are fabricated as one-piece assemblies using low-density ablative thermal protection materials. The heat shield assembly is built from modular pieces formed by ablative impregnation processing. Once the full-size heat shield is assembled from the modular blocks, heat treatment is used to bond the individual blocks together by facilitating polymeric cross-linking of impregnant material within and/or between each block.