NASA ended the shuttle program last summer after a 30-year run to focus on destinations beyond low-Earth orbit. Private U.S. companies hope to pick up the slack, beginning with space station cargo and then, hopefully, astronauts. The first commercial cargo run, by Space Exploration Technologies Corp., is set to take place in just another few weeks.
For at least the next three to five years -- until commercial passenger craft are available in the United States -- NASA astronauts will have to hitch multimillion-dollar rides on Russian Soyuz capsules to get to the International Space Station.
Read more: Space shuttle Discovery makes final landing