About five years from now, a modified Dragon spacecraft will begin to fire its Draco thrusters, pushing the International Space Station out of its orbit and sending the largest object humans have built in space inexorably to the bottom of the Pacific Ocean.
And then what?
China's Tiangong Space Station will still be going strong. NASA, however, faces a serious risk of losing its foothold in low-Earth orbit. Space agency leaders have long recognized this and nearly half a decade ago awarded about $500 million to four different companies to begin working on "commercial" space stations to fill the void.
