Many intricacies of space shuttle development are kept under wraps. But it’s no secret that borates played an integral part in keeping our astronauts safe.
Borates, which are used in glass of all types, coated the about 23,000 ceramic tiles on the underside of the space shuttle to help it withstand the thermal shock of reentry. Thermal shock occurs when temperatures change suddenly, as when the shuttle leaves the frigid temperatures of space and reenters Earth’s atmosphere at nearly 3,000 degrees Fahrenheit.
The reusable tiles, which are box-shaped and primarily composed of silica for its high melting point, are coated on five sides with a borate-containing glass that is typically black in color. In addition to heat resistance, the glass provides support to the tiles, which otherwise would be extremely lightweight and brittle.
The tiles were developed at NASA research facilities and select academic institutions. Bob Deal, retired technical director of Rio Tinto Borates (U.S. Borax), noted that the company provided technical consultation through its former entity, U.S. Borax Research Corporation.
If you would like to see a tile firsthand, we invite you to our Visitor Center in Boron, California. The showcased tile is on loan from NASA.