New requirements for a bigger cargo bay prompted a breakthrough in spacecraft design. The development of the reusable Shuttle sparked a revolutionary approach to space. The Shuttle, described as a butterfly on a bullet, departed on its maiden voyage in April 1981. It was an outstanding success but subsequent missions remained as dangerous as ever, as demonstrated by both the 1985 Challenger and 2003 Columbia Shuttle disasters. But the development of the International Space Station meant that the Shuttle could not be abandoned.