NASA has recently announced the selection of four veteran astronauts who will be the first to fly aboard U.S. commercial space flights to the International Space Station; this move is considered an interim step to an eventual mission to Mars.

NASA has advanced the mission of commercial spacecraft being built by SpaceX and Boeing by naming four of its veteran astronauts to lead those inaugural flights. 
Sunita Williams, Robert Behnken, Douglas Hurley, and Eric Boe will be the first to fly to space on vehicles contracted out to private firms, not built by the&nb