A part of the space shuttle's thermal protection system (TPS) to protect the vehicle's surface from heat caused by atmospheric friction during re-entry. Besides thermal tiles, some surface insulation is composed of a felt reusable surface insulation (FRSI) of coated Nomex cloth to protect the upper fuselage and an advanced flexible reusable surface insulation (AFRSI), consisting of a quilted blanket of silica fibre, for some other areas.