The Thermal Protection System on the orbiter is its biggest defense to the heat encountered during re-entry. The orbiter must be able to withstand extreme temperatures and air deflections while coming back in. Every time the orbiter enters the atmosphere it loses several of these tiles, but as long as they don’t all come off in one spot the orbiter will be okay. These tiles are made of ceramic materials and must be able to withstand a temperature of nearly 3,000 oF. There are over 27,000 of these tiles on the shuttle, all just as important as the next.