Space station commander Andrey Borizenko, cosmonaut Alexander Samokutyayev and NASA astronaut Ronald Garan had been set to return to Earth on Sept. 8, leaving three crewmates to staff the outpost until replacements arrived around two weeks later.
But the Russian Soyuz rockets used to fly crews to the station have a nearly identical upper-stage motor as the ones used on Russian cargo ships, the last of which failed to reach orbit following launch on Aug. 24.
The Progress cargo ship burned up in the atmosphere and the debris crashed in Siberia. Crew flights to the space station have been suspended until the cause of the accident is determined.
“I can’t imagine the Soyuz flying (Sept. 21). That’s pretty much off the table,” NASA space station program manager Mike Suffredini told reporters during a conference call on Monday.
Keeping Borizenko, Garan and Samokutyayev in orbit will buy more time to resolve the problem, though Suffredini said the crew most likely will return to Earth mid-September. Return dates are dictated by the six-month lifespan of the Soyuz capsules docked at the station, and so that landings occur during daylight in Kazakhstan.
That would leave incoming station commander Mike Fossum, cosmonaut Sergei Volkov and Japanese astronaut Satoshi Furukawa to staff the outpost, a $100 billion project of 16 nations, until their scheduled return in mid-November.
If a replacement crew is not launched before then, the station will be left untended for the first time since Nov. 2, 2000, when the first live-aboard crew arrived.
The station could survive unmanned, with many experiments including the Alpha Magnetic Spectrometer particle detector continuing to operate.
Human research experiments, however, would end, as would flexibility to handle station maintenance and operations.
“We can command the vehicle from the ground and operate it fine and remain on orbit indefinitely,” Suffredini said.
Following the final US space shuttle flight in July, the station has enough supplies to last until next summer, despite the loss of 3 tons of cargo in the botched launch.
The shuttles’ retirement is not a factor in the current situation with the station, Suffredini said.
Soyuz capsules are always needed at the outpost to serve as lifeboats, and none will be launched until the cause of the Progress launch failure is found and fixed.
The United States turned over all crew transportation to Russia, at a cost of more than $50 million per person.
Boeing Co, Space Exploration Technologies and Sierra Nevada Corp. are among the companies NASA is backing to try to develop commercial human orbital space transportation services.
UScargo supply ships operated by Space Exploration Technologies and Orbital Sciences Corp. are scheduled to begin deliveries next year.