Thermal Barriers

Thermal barriers are used in the closeout areas between various components of the orbiter and TPS, such as the forward and aft RCS, rudder/speed brake, nose and main landing gear doors, crew ingress and egress hatch, vent doors, external tank umbilical doors, vertical stabilizer/aft fuselage interface, payload bay doors, wing leading edge RCC/HRSI interface, and nose cap and HRSI interface. The various materials used are white AB312 ceramic alumina borosilica fibers or black-pigmented AB312 ceramic fiber cloth braided around an inner tubular spring made from Inconel 750 wire with silica fibers within the tube, alumina mat, quartz thread and Macor machinable ceramic.

Where surface pressure gradients would cause cross flow of boundary layer air within the intertile gaps, tile gap fillers are provided to minimize heating. The tile gap filler materials consist of white AB312 fibers or a black-pigmented AB312 cloth cover containing alumina fibers. These materials are used around the leading edge of the forward fuselage nose cap, windshields and side hatch, wing, trailing edge of elevons, vertical stabilizer, rudder/speed brake, body flap and heat shield of the shuttle's main engines.

Fused silica threaded inserts and plugs are used in the tiles to provide access for door removal or panel attachment.