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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Space Shuttle thermal protection system | 3/5 | https://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system | reference | science, encyclopedia | 2026-05-05T13:22:37.256899+00:00 | kb-cron |
==== Low-temperature reusable surface insulation (LRSI) ==== White in color, these covered the upper wing near the leading edge. They were also used in selected areas of the forward, mid, and aft fuselage, vertical tail, and the OMS/RCS pods. These tiles protected areas where reentry temperatures are below 1,200 °F (649 °C). The LRSI tiles were manufactured in the same manner as the HRSI tiles, except that the tiles were 8 by 8 inches (20 by 20 cm) square and had a white RCG coating made of silica compounds with shiny aluminium oxide. The white color was by design and helped to manage heat on orbit when the orbiter was exposed to direct sunlight. These tiles were reusable for up to 100 missions with refurbishment (100 missions was also the design lifetime of each orbiter). They were carefully inspected in the Orbiter Processing Facility after each mission, and damaged or worn tiles were immediately replaced before the next mission. Fabric sheets known as gap fillers were also inserted between tiles where necessary. These allowed for a snug fit between tiles, preventing excess plasma from penetrating between them, yet allowing for thermal expansion and flexing of the underlying vehicle skin. Prior to the introduction of FIB blankets, LRSI tiles occupied all of the areas now covered by the blankets, including the upper fuselage and the whole surface of the OMS pods. This TPS configuration was only used on Columbia and Challenger.
=== Non-tile TPS ===
==== Flexible Insulation Blankets/Advanced Flexible Reusable Insulation (FIB/AFRSI) ==== Developed after the initial delivery of Columbia and first used on the OMS pods of Challenger. This white low-density fibrous silica batting material had a quilt-like appearance, and replaced the vast majority of the LRSI tiles. They required much less maintenance than LRSI tiles yet had about the same thermal properties. After their limited use on Challenger, they were used much more extensively beginning with Discovery and replaced many of the LRSI tiles on Columbia after the loss of Challenger.
==== Reinforced carbon-carbon (RCC) ====
The light gray material which withstood reentry temperatures up to 1,510 °C (2,750 °F) protected the wing leading edges and nose cap. Each of the orbiters' wings had 22 RCC panels about 1⁄4 to 1⁄2 inch (6.4 to 12.7 mm) thick. T-seals between each panel allowed for thermal expansion and lateral movement between these panels and the wing. RCC was a laminated composite material made from carbon fibres impregnated with a phenolic resin. After curing at high temperature in an autoclave, the laminate was pyrolized to convert the resin to pure carbon. This was then impregnated with furfural alcohol in a vacuum chamber, then cured and pyrolized again to convert the furfural alcohol to carbon. This process was repeated three times until the desired carbon-carbon properties were achieved. To provide oxidation resistance for reuse capability, the outer layers of the RCC were coated with silicon carbide. The silicon-carbide coating protected the carbon-carbon from oxidation. The RCC was highly resistant to fatigue loading that was experienced during ascent and entry. It was stronger than the tiles and was also used around the socket of the forward attach point of the orbiter to the External Tank to accommodate the shock loads of the explosive bolt detonation. RCC was the only TPS material that also served as structural support for part of the orbiter's aerodynamic shape: the wing leading edges and the nose cap. All other TPS components (tiles and blankets) were mounted onto structural materials that supported them, mainly the aluminium frame and skin of the orbiter.
==== Nomex Felt Reusable Surface Insulation (FRSI) ==== This white, flexible fabric offered protection at up to 371 °C (700 °F). FRSI covered the orbiter's upper wing surfaces, upper payload bay doors, portions of the OMS/RCS pods, and aft fuselage.
==== Gap fillers ==== Gap fillers were placed at doors and moving surfaces to minimize heating by preventing the formation of vortices. Doors and moving surfaces created open gaps in the heat protection system that had to be protected from heat. Some of these gaps were safe, but there were some areas on the heat shield where surface pressure gradients caused a crossflow of boundary layer air in those gaps. The filler materials were made of either white AB312 fibers or black AB312 cloth covers (which contain alumina fibers). These materials were used around the leading edge of the nose cap, windshields, side hatch, wing, trailing edge of elevons, vertical stabilizer, the rudder/speed brake, body flap, and heat shield of the shuttle's main engines. On STS-114, some of this material was dislodged and determined to pose a potential safety risk. It was possible that the gap filler could cause turbulent airflow further down the fuselage, which would result in much higher heating, potentially damaging the orbiter. The cloth was removed during a spacewalk during the mission.
=== Weight considerations ===
While reinforced carbon–carbon had the best heat protection characteristics, it was also much heavier than the silica tiles and FIBs, so it was limited to relatively small areas. In general the goal was to use the lightest weight insulation consistent with the required thermal protection. Density of each TPS type:
Total area and weight of each TPS type (used on Orbiter 102, pre-1996):
== Early TPS problems ==
=== Slow tile application ===