The failure of an unmanned Russian Soyuz booster during launch last week has thrown a wrench into International Space Station operations, with upcoming fights to and from the lab complex facing delays that likely will result in extended operations with a reduced crew of three, a senior NASA manager said today.
During the launch of an unmanned Progress supply capsule atop a Soyuz booster last Wednesday, a sudden loss of pressure downstream of a turbo-pump in the third-stage engine resulted in a computer-commanded shutdown 5 minutes and 20 seconds after liftoff from the Baikonur Cosmodrome in Kazakhstan.
The Progress capsule, loaded with 2.9 tons of supplies and equipment bound for the space station, never separated from the third stage and crashed in the remote Altai region near the Russian border with Mongolia and China. The spacecraft is believed to have broken up before impact, but as of this morning, Russian engineers had not yet located the wreckage, according to Mike Suffredini, the space station program manager at the Johnson Space Center in Houston.
If the rocket problem is not resolved in time to resume crewed Soyuz launches by mid-November, station managers could be forced to temporarily unman the huge complex.
While the space station can be operated from the ground without a crew on board, engineers hope it won't come to that because of the threat of failures that might require hands-on human intervention.
"We prefer not to operate in that condition without crew on board for an extended period of time just to make sure we don't end up in that situation," said Suffredini. "But assuming the systems keep operating, we can command the vehicle from the ground and operate it fine and remain on orbit indefinitely."
The loss of supplies will not have a significant impact on station operations thanks to the July flight of the shuttle Atlantis and earlier unmanned resupply missions. The station has enough supplies on board to operate until next summer without any additional manned or unmanned launchings.
But the third stage of the Progress Soyuz is virtually identical to the upper stage of the Soyuz used to launch Russian manned missions, and until the problem is resolved and modifications are made, manned flights to the space station are on hold.
At the time of the failure, the Russian manifest called for three of the station's six crew members to return to Earth September 8. The Russians planned to launch three fresh crew members--Anton Shkaplerov, Anatoly Ivanishin, and NASA flight engineer Dan Burbank--aboard the Soyuz TMA-22 spacecraft on September 22 to boost the lab crew back to six. Another unmanned Progress was scheduled for launch October 26.
But given the Progress failure, the three crew members who'd intended to return to Earth in early September likely will delay their departure and remain aboard the space station for an additional week or so. NASA managers favored keeping the crew aloft until late October to maximize science operations and to keep two U.S. astronauts on board as long as possible to protect against any failures of NASA components that might require a spacewalk. But daylight landing opportunities in Kazakhstan end around September 19 and do not become available again until around October 27. By that point, the crew's spacecraft will have been in orbit about 10 days beyond its certified 200-day limit.
Launch of Shkaplerov, Ivanishin, and Burbank will be delayed as well while Russian engineers evaluate the Progress failure. If possible, Russian planners would like to carry out two already-planned unmanned Soyuz fights before launching a crewed mission to make sure whatever fixes might be required will work properly.
"It's not a trivial thing," Suffredini said. "If you look at...risk assessments, some of the numbers are not insignificant. There is a greater risk of losing the ISS when it is unmanned than if it were manned. That's why, when we made our decision after the Columbia accident to keep the station manned, that is exactly why, because the risk increase is not insignificant."
But NASA managers say they are confident the Russians will resolve the Progress/Soyuz problem in time to prevent that worst-case scenario from playing out.
Asked if the Progress failure would heighten criticism of the Obama administration's post-shuttle space policy and the near-term lack of an operational U.S. manned rocket system, Suffredini said flight safety, not concern about public relations, was the team's only concern.
"If you think about it, (the Progress failure) was sort of a gift," he said. "We have the logistics on board to recover from it. It's going to tell us about an anomaly before we put humans on a similar vehicle. So really, this is a great opportunity for us to learn about an anomaly and resolve the anomaly without putting a crew at risk.
"Flying safely is much, much more important than anything else I can think about right this instant. I'm sure we'll have an opportunity to discuss any political implications if we spend a lot of time on the ground, but you know, we'll just have to deal with them because we're going to do what's the safest for the crew and the space station, which is a very big investment of our governments. Our job is to protect that investment, and that's exactly what we're going to do."