Two NASA astronauts who were stuck on the International Space Station for nine months are returning to Earth aboard SpaceX's Crew Dragon spaceship.The astronauts, Butch Wilmore and Suni Williams, were originally launched into space by Boeing's Starliner spaceship for a demonstration mission.The Starliner experienced engine glitches and was sent back to Earth empty, while Wilmore and Williams stayed on the ISS.The astronauts are expected to splash down off the coast of Florida after a fiery plummet back to Earth.