Astronaut Clayton Anderson floating aboard the space shuttle Discovery during the STS-131 mission in April 2010.
Following the other members of its fleet, the Space Shuttle Atlantis will retire in July. When it does, NASA will be left without any spacefaring vehicles. The next U.S. craft intended for human space travel, a "multi-purpose crew vehicle" fit to visit an asteroid by 2025, is, at this point, not much more than an artist's rendering.
What will U.S. astronauts do in the interim? How will NASA get them into space?
According to space agency representatives, some astronauts will stay on the ground to help with the planning and design of future missions and vehicles . Others will accept rides aboard Russia's Soyuz space capsules to and from the International Space Station (ISS ), where they'll work.
The shift to Soyuz flights isn't actually a huge shakeup for U.S. astronauts.
"NASA astronauts, as well as European astronauts and Japanese astronauts, have been flying to the ISS on Soyuz for a number of years now," said Joshua Buck, NASA's public affairs officer for space operations. NASA pays Russia's space agency for Soyuz seats.
The space station, an orbiting laboratory, continuously houses a crew of six from any of the spacefaring nations. Their six-month assignments are staggered so that three crewmembers are traded out every three months. [Read: What's It Like to Live In Space? ]
For several years, the Soyuz capsules have been solely responsible for delivering and returning the ISS crews. Meanwhile the space shuttles have served more as delivery trucks. "There have been manned missions that obviously went to the station to deliver supplies and cargo, but they were not carrying people who would stay," Buck told Life's Little Mysteries.
Just as they have been doing already, future ISS crews will train together at the Johnson Space Center in Houston, then complete their training in Russia before launching aboard the Soyuz from Kazakhstan in Central Asia.
The end of space-shuttle-to-ISS cargo deliveries will decrease the number of NASA astronauts required for space travel. According to Nicole Cloutier-Lemasters, the public affairs officer at Johnson Space Center, the extra astronauts who might previously have been training for ISS supply missions will take on other, ground-based roles, such as helping with research and design for future NASA vehicles. [Read: NASA Unveils New Spaceship for Deep Space Exploration]
"Because there is such a lead time on those future missions, there are a lot of milestones and a lot that goes into the initial work," Cloutier-Lemasters said. "So some of our astronauts will support the crew office, review designs such as instrument panel designs, and give feedback."
Another subset of astronauts, Cloutier-Lemasters said, "will move to other positions within the agency."