The Federal Space Agency postponed the next manned mission to the International Space Station by at least a month Monday, and Russian and U.S. space officials said any further delay might force astronauts to leave the station unmanned for the first time in a decade.
The Federal Space Agency announced its decision to allow time for safety checks to be made following the crash of an unmanned cargo craft ferrying food and fuel to the space station on Aug. 24.
It set no new dates for the missions in a brief statement. But Interfax said three of the six crew members would now return to Earth around Sept. 16, instead of Sept. 8, and replacements would blast off in late October or early November instead of Sept. 22.
"If for any reason we will not be able to deliver the crew before the end of November, we will need to review all possibilities, including leaving the station unmanned," said Alexei Krasnov, who is in charge of manned flights at the Federal Space Agency, Interfax reported.
Interfax quoted an unidentified space official as saying the Federal Space Agency would carry out two test launches of its unmanned Soyuz rocket before sending the next astronauts into space.
NASA space station program manager Mike Suffredini said in a conference call with reporters Monday that flight controllers could keep a deserted space station operating indefinitely.
"We can command the vehicle from the ground, operate it fine and remain in orbit indefinitely," Suffredini said.
Many experiments, including the Alpha Magnetic Spectrometer particle detector, also could continue to operate. Human research experiments, however, would end, as would flexibility to handle station maintenance and operations.
The International Space Station, an orbiting research laboratory that is a $100 billion project involving five space agencies, has been permanently manned for more than a decade.
The next launch of crew members to the space station will be the first since the U.S. space agency NASA retired its 30-year shuttle program in July. This has caused concern at NASA as it now relies entirely on Russian craft to send people into space.
But Suffredini said the shuttles' retirement is not a factor in the current situation with the station.
Following the final U.S. space shuttle flight last month, the station has enough supplies to last until next summer, despite the loss of 3 tons of cargo in the botched launch.
Russian space officials hope the announcement of safety checks will increase confidence following the crash, in which a Soyuz-U craft failed to reach orbit and burned up in the atmosphere shortly after launch.
The Soyuz-U, whose failure was caused by an apparent problem with the rocket's upper-stage motor, closely resembles the Soyuz-FG used to transport astronauts to the orbital station.
"These delays and checks are normal following such a failure. I think they will manage to get a craft to the space station to avoid it being unmanned," said Igor Lissov, editor of monthly space journal Novosti Kosmonavtiki.
"You can run the space station from Earth but you can't do it as well as when it is manned," he added, but declined to speculate how long it could be left unmanned.
NASA said last week the six astronauts in orbit had enough food and water for months. But bringing astronauts back to Earth would be safer before winter starts in Kazakhstan, where they would touch down.
The station is manned by U.S. astronauts Ron Garan and Mike Fossum, Japan's Satoshi Furukawa and Russian cosmonauts Sergei Volkov, Alexander Samokutyayev and mission commander Andrei Borisenko.
Borisenko, Samokutyayev and Garan are due to end their mission.
Last week's failure was an embarrassment for the space industry after a series of costly botched launches. Media reports put the cumulative recent losses at more than $553 million.
Prime Minister Vladimir Putin has ordered an overhaul of safety checks on Russia's rockets, while a pro-Kremlin lawmaker said the State Duma would review whether "systemic problems or just bad luck" were to blame for the failures.