AFRSI blankets replace the vast majority of the LRSI tiles. AFRSI consists of a low-density fibrous
silica batting that is made up of high-purity silica and 99.8-percent amorphous silica fibers (1 to 2 mils thick). This batting is sandwiched between an outer woven silica high-temperature fabric
and an inner woven glass lower temperature fabric. After the composite is sewn with silica thread, it has a quiltlike appearance. The AFRSI blankets are coated with a ceramic collodial silica and
high-purity silica fibers (referred to as C-9) that provide endurance. The AFRSI composite density is approximately 8 to 9 pounds per cubic foot and varies in thickness from 0.45 to 0.95 inch. The
thickness is determined by the heat load the blanket encounters during entry. The blankets are cut to the planform shape required and bonded directly to the orbiter by RTV silicon adhesive 0.20 inch
thick. The very thin glue line reduces weight and minimizes the thermal expansion during temperature changes. The sewn quilted fabric blanket is manufactured by Rockwell in 3- by 3-foot squares of
the proper thickness. The direct application of the blankets to the orbiter results in weight reduction, improved producibility and durability, reduced fabrication and installation cost, and reduced
installation schedule time.