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Low-Temperature Reusable Surface Insulation Tiles

The LRSI tiles are of the same construction and have the same basic functions as the 99.8-percent-pure silica HRSI tiles, but they are thinner (0.2 to 1.4 inches) than HRSI tiles. Thickness is determined by the heat load encountered during entry. The 99.8-percent-pure silica LRSI tiles are manufactured in the same manner as the 99.8-percent-pure silica HRSI tiles, except that the tiles are 8- by 8-inch squares and have a white optical and moisture-resistant coating applied 10 mils thick to the top and sides. In addition, the white coating provides on-orbit thermal control for the orbiter. The coating is made of silica compounds with shiny aluminum oxide to obtain optical properties. The coated 99.8-percent-pure silica LRSI tiles are treated with bulk waterproofing similar to the HRSI tiles. LRSI tiles are installed on the orbiter in the same manner as the HRSI tiles. The LRSI tile has a surface emittance of 0.8 and a solar absorptance of 0.32.

Because of evidence of plasma flow on the lower wing trailing edge and elevon leading edge tiles (wing/elevon cove) at the outboard elevon tip and inboard elevon, the LRSI tiles are replaced FRCI-12 and HRSI 22 tiles along with gap fillers on Discovery (OV-103) and Atlantis (OV-104). On Columbia (OV-102), only gap fillers are being installed in this area.

Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 04/07/2002
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