Space exploration has taken some hits in the 21st century, with cuts to the U.S. and other international space program budgets. But with the Curiosity Rover on Mars as of August 2012 and plans to launch the "most powerful rocket in history," the Space Launch System (SLS) by 2017, NASA is still very much in the business of the future. After the planned, unmanned sendoff of the SLS in 2017, NASA intends to send a crew of up to four astronauts into space by 2021. This could be a return to the moon, with capabilities for missions on other planets [sources: Landau; NASA].