Without the space shuttles, NASA will rely on Russian Soyuz vehicles to ferry astronauts to and from the space station, which is slated to operate until at least 2020. The agency wants private American craft to take over this taxi service eventually, but that probably won't happen for at least four or five years.
For its part, NASA has begun shifting its focus beyond low-Earth orbit. Last year, President Barack Obama charged the space agency with sending astronauts to an asteroid by 2025, and then on to Mars by the mid-2030s.
As exciting as both of these exploration prospects are, they remain far off, both in space and time. Right now, most thoughts are with Atlantis as it streaks toward the space station, its final mission closing out the life of a spacecraft that came to represent a nation in many ways.
Over the years, the space shuttle became a symbol of America, its ambitious goals and its technological know-how, experts say.
"The shuttle became a very powerful icon," Roger Launius, space history curator at the National Air and Space Museum, told SPACE.com, "just as serviceable an icon as the astronauts landing on the moon, in terms of national prestige abroad and pride at home."