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.