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To stay cool during reentry, the bottom black surface of the Space Shuttle is coated with over 24,000 tiles made from silica fibers, or high quality sand that has been microwaved at 2350 degrees. The upper surface does not experience as much heat from reentry and is made mostly of woven silicon blankets whitewashed with a silica-aluminum oxide mixture. Approximately 30-100 tiles are replaced before every mission to make sure that they can properly protect the Shuttle. In order to stay warm while in space, the Shuttle simply redirects heat from the electronic equipment onboard to keep vital equipment protected.