Aside from being the second-largest planet after Jupiter, Saturn is also the least dense. In fact, the planet’s density is so low that, if one could find a pool of water large enough, Saturn would actually float in it.
The Space Shuttle was the highlight of NASA’s Space Transport System’s reusability. Six shuttles were built, but only five ever went to orbit. STS Enterprise was used only for preliminary test flights and training.
The Space Transport System (also known as the Space Shuttle) revolutionized American spaceflight. Its design and development were greenlighted by President Richard Nixon in 1969, with flights beginning in the early 1980s.