The US Space Transportation System (STS) was intended to make space travel more efficient and less expensive because the shuttle could be flown back to Earth by a pilot and reused. NASA considered the STS shuttle to be the first aerospace vehicle since it took off like a rocket and landed on a runway like an airplane.
NASA estimates indicated that each shuttle would be capable of a minimum of 100 flights, and the solid rocket booster, casings, engine nozzles and parachutes for 20. The shuttle was designed to carry large, heavy payloads into space and had the capability of putting astronauts in a position where they could repair malfunctioning satellites in orbit or return them to Earth for a tune-up and relaunch. The shuttle's connection with satellites made it highly attractive considering how vital satellites have become in the modern world.
Besides reusability and high cargo capacity, the shuttle represented a technological advance in heat insulation. Earlier manned spacecraft used heat shields that flaked apart; pieces of the shield would carry heat away during the fiery reentry. Shields like those tended to be heavy and were obviously not reusable. The shuttle on the other hand was insulated by special silicon-based 100 square-inch (average) tiles, a lightweight material that could withstand temperatures up to 2,300┬║ F. You could actually hold your hand against one side of the tile while the other side was red-hot!
Typical shuttle flights lasted two to ten days and carried a two to eight person crew. Often scientists or technicians accompanied the astronauts. The shuttle flew 24 successful missions in five years, but the Challenger explosion in 1986 spelled the beginning of the end for the Space Transportation System.
