Toughened Unipiece Fibrous Reinforced Oxidation-resistant Composite (TUFROC) is a tiled Thermal Protection System (TPS) suitable for reusable entry heating at 2900+ °F and with single use potential up to at least 3600 °F. TUFROC was initially developed for NASA's X-37 project and ultimately resulted in use on the Air Force X-37B as the wing leading edge (WLE) of the vehicle. TUFROC has similar high temperature capability compared with carbon/carbon, but is manufactured at an order of magnitude lower cost & faster schedule.

A spray-on coating was developed for use on the shuttle wing tiles to obtain data that could be correlated with computational fluid dynamics (CFD) solutions to better understand the effect of chemical heating on a fore-body heat shield having a turbulent boundary layer during planetary entry at hypersonic speed. The selection of a spray-on coating was conducted in two Phases 1) screening tests to select the catalytic coating formulation and 2) surface property determination using both arc-jet and side-arm facilities at NASA Ames Research Center. Comparison of the predicted surface temperature profile over a flat-plate with measured values obtained during arc-jet exposure (Phase I study) was used to validate the surface properties obtained during Phase II.

This paper describes the performance of advanced ceramic coatings being developed for future spacecraft. The goal of this research was to optimize optical properties while minimizing the coating thermochemical instability during high-speed entry into the earth's atmosphere. Effects of composition, permeability, particle size, and thickness of these coatings on the optical properties were studied in aeroconvectively heated environments at enthalpies between 23.3 MJ/Kg and 35.0 MJ/Kg and surface temperatures in excess of 1500 K.

This paper describes the dimensional stability of ceramic coated thermal protection materials developed for use on advanced entry vehicles. Dimensional stability of these ceramic materials were studied as a function of temperature and pressure during exposure to simulated atmospheric entry in an arc-jet facility.

The need for improved ceramic coatings compatible with new low density reusable surface insulation (RSI) material for Advanced Atmospheric Entry Spacecraft has stimulated research on higher temperature capability coatings. The paper discusses the use of overlays and compositional modifications to improve the baseline (RCG) coating. Stability of composition and morphology of these coatings are described relative to radiant and convective heating environments.

Thermal conductivity for a family of fibrous, refractory composite insulations are characterized through the use of an engineering model and arc-jet data. The model defines the composite as a uniform pore material using measured physical and mechanical properties. Efficiency parameters assigned to the solid and radiation conduction terms in the thermal conductivity equation were found to be dependent only on solid volume fraction and porosity.

Laminated composite insulations developed for potential use on advanced spacecraft operating between geosynchronous and low earth orbits were tested in an aerothermodynamic environment simulating an AOTV aerobraking maneuver (altitude 82.3 km and velocity = 9.0 km/s). Comparisons are discussed between these data and predictions of in-depth temperature response using dynamic thermal conductivity values to 2000K.

TUFROC (Toughened Uni-piece Fibrous Reinforced Oxidation-resistant Composite) has been developed as a new thermal protection system (TPS) material for wing leading edge and nose cap applications. The composite withstands temperatures up to 1,970 K, and consists of a toughened, high-temperature surface cap and a low-thermal-conductivity base, and is applicable to both sharp and blunt leading edge vehicles. This extends the possible application of fibrous insulation to the wing leading edge and/or nose cap on a hypersonic vehicle. The lightweight system comprises a treated carbonaceous cap composed of ROCCI (Refractory Oxidation-resistant Ceramic Carbon Insulation), which provides dimensional stability to the outer mold line, while the fibrous base material provides maximum thermal insulation for the vehicle structure.

7 Hot-film sensors, consisting of a metallic film on an electrically nonconductive substrate, have been used to measure skin friction as far back as 1931. A hot film is maintained at an elevated temperature relative to the local flow by passing an electrical current through it. The power required to maintain the specified temperature depends on the rate at which heat is transferred to the flow. The heattransfer rate correlates to the velocity gradient at the surface, and hence, with skin friction. The hot-film skin friction measurement method is most thoroughly developed for steady-state conditions, but additional issues arise under transient conditions. Fabricating hot-film substrates using low-thermal-conductivity ceramics can offer advantages over traditional quartz or polyester-film substrates. First, a low conductivity substrate increases the fraction of heat convected away by the fluid, thus increasing sensitivity to changes in flow conditions. Furthermore, the two-part, composite nature of the substrate allows the installation of thermocouple junctions just below the hot film, which can provide an estimate of the conduction heat loss.

Silica (LI-900) Reusable Surface Insulation (RSI) tile have been used on the majority of the Shuttle since its initial flight. Its overall performance with Reaction Cured Glass (RCG) coating applied will be reviewed. Improvements in insulations, Fibrous Refractory Composite Insulation (FRCI-12) and Alumina Enhanced Thermal Barrier (AETB-8) and coatings/surface treatments such as Toughened Uni-Piece Fibrous Insulation (TUFI) have been developed and successfully applied. The performance of these enhancements on the Shuttle Orbiters over the past few years along with the next version of tile materials, High Efficiency Tantalum-based Ceramic (HETC) with even broader applicability will also be discussed.

This viewgraph presentation provides an overview of the Space Shuttle Thermal Protection System (TPS) and the various products incorporated in the TPS. There are three tile systems which include pure silica, fibrous refractory composite insulation (FRCI), and alumina enhanced thermal barrier (AETB). Coating systems include reaction cured glass (RCG) and toughened uni-piece insulation (TUFI). The microstructures of these systems are explored as are the manufacturing processes associated with each. Microstructural investigation using methods such as automated X-ray spectral image analysis (AXSIA) is a crucial part of understanding the mechanical nature of these systems.