Astronauts may need to take the unprecedented step of temporarily abandoning the International Space Station if a launch accident last week in Russia prevents new crews from flying there this fall.
Until officials figure out what went wrong with Russia's Soyuz rockets, there will be no way to launch any more astronauts before the current residents have to leave in mid-November.
The unsettling predicament comes just weeks after NASA's final space shuttle flight.
"We have plenty of options," NASA's space station program manager, Mike Suffredini, assured reporters Monday. "We'll focus on crew safety as we always do."
Abandoning the space station, even for a short period, would be a last resort for the world's five space agencies that have spent decades working on the project. Astronauts have been living aboard the space station since 2000, and the goal is to keep it going until 2020.
Suffredini said flight controllers could keep a deserted space station operating indefinitely, as long as all major systems are working properly. The risk to the station goes up, however, if no one is on board to fix equipment breakdowns.
Six astronauts from three countries are living on the orbiting complex. Three are due to leave next month; the other three are supposed to check out in mid-November. They can't stay any longer because of spacecraft and landing restrictions.
The Sept. 22 launch of the next crew -- the first to fly in this post-shuttle era -- already has been delayed indefinitely. Russia's Soyuz spacecraft have been the sole means of getting full-time station residents up and down for two years.
To keep the orbiting outpost with a full staff of six for as long as possible, the one American and two Russians due to return to Earth on Sept. 8 will remain on board at least an extra week.
As for supplies, the space station is well stocked and could go until next summer, Suffredini said. Atlantis dropped off a year's supply of goods just last month on the final space shuttle voyage. The unmanned Russian craft destroyed Wednesday was carrying 3 tons of supplies.
The Soyuz has been extremely reliable over the decades; this was the first failure in 44 Russian supply hauls for the space station. Even with such a good track record, many in and outside NASA were concerned about retiring the space shuttles before a replacement was ready to fly astronauts.
Russian officials have set up an investigation team for the launch accident. Until it comes up with a cause and a repair plan, the launch and landing schedules remain in question.
One or two unmanned Soyuz launches are on tap for October, one commercial and the other another space station supply run. Those would serve as important test flights before putting humans on board, Suffredini said.