The successful explortion of space requires a system that will reliably transport payloads into space and return back to earth; without subjecting them an uncomfortable or hazardous environment. In other words, the space crafts and its pay loads have to be recovered safely into the earth.
Description of Space Shuttles and its Advancements
The space shuttle used at older times were not re-usable. So NASA invented re-usable space shuttle that could launch like a rocket but deliver and land like an aeroplane. Now NASA is planning to launch a series of air-breathing planes that would replace the space shuttle.
A Brief History Of The Space Shuttle
Near the end of the Apollo space program, NASA officials were looking at the future of the American space program. At that time, the rockets used to place astronauts and equipment in outer space was one-shot disposable rockets. What they needed was a reliable, but less expensive, rocket, perhaps one that was reusable. The idea of a reusable "space shuttle" that could launch like a rocket but deliver and land like an airplane was appealing and would be a great technical achievement.
NASA began design, cost and engineering studies on a space shuttle. Many aerospace companies also explored the concepts. In 1972 NASA announced that it would develop a reusable space shuttle or space transportation programme (STS).NASA decided that the shuttle would consist of an orbiter attached to solid rocket boosters and an external fuel tank because this design was considered safer and more cost effective. At that time, spacecraft used ablative heat shields that would burn away as the spacecraft re-entered the Earth's atmosphere.
However, to be reusable, a different strategy would have to be used. The designers of the space shuttle came up with an idea to cover the space shuttle with many insulating ceramic tiles that could absorb the heat of re-entry without harming the astronauts.