The water-repellent is indispensible for the ceramic heat shield of the space shuttles, which are built in Cape Canaveral in the subtropical climate of Florida. There, the year-round humidity can reach as high as 95 percent. Without the water-repellent finish, the ceramic shell would quickly soak up water, and the space shuttle would take on an incalculable amount of weight. Then as the altitude increases and the temperature drops, this water would freeze extremely fast, only to evaporate just as fast when the space shuttle leaves the earth’s atmosphere a few minutes after launch. This would cause cracks and breaks in the tiles.