In what should have been the "home stretch" of their six-month orbital expedition, the crew of the international space station is struggling with new problems in their critical oxygen production system. Balky Russian equipment has been nursed along for months, but has now broken down again in a new and challenging "failure mode." And so far, all attempts to restart the equipment have failed.
Astronaut Mike Fincke and cosmonaut Gennady Padalka, who are scheduled to be relieved by a new crew in mid-October, are not in any imminent danger, and engineers remain confident that some combination of backup procedures and unprecedented in-flight repairs can keep the two breathing easy.
Without a quick resolution of this problem, however, the launch of the new crew would have to be postponed. While not a serious concern yet, the current crew then might have to set the station on "autopilot" and return to Earth by the end of October, leaving the station empty for the first time in four years.
Furthermore, this is just the latest in a series of unexpected glitches with the oxygen system. MSNBC.com has obtained internal NASA status reports and has talked with several high-ranking NASA space station officials. The picture that emerges is one of bouts of growing concern (but still short of alarm) interspersed with periods of relief and hope.
Series of failures
In the latest incident, a Sept. 8 NASA internal status report stated that “The Russian oxygen (O2) generator is still off.” This Elektron generator uses electrical power to split water molecules into breathable oxygen and waste hydrogen. Russian space stations have used such devices, each about the size of a water heater, for more than fifteen years.
New telemetry allowed Moscow Mission Control to rule out another recurrence of a recent familiar failure mode that involved gas inside a fluid container.
“The problem this time is apparently not with bubbles in the ‘Fluid Unit’,” the NASA report stated, “but with the unit's oxygen & hydrogen gas analyzer, which is a failure mode not seen before.” This followed the occurrence a week earlier of another never-before-seen failure of a valve switch.
Before this latest failure, U.S. and Russian operators had expected the unit to operate “for at least another few months” before breaking down completely.
In Houston, NASA spokesman Rob Navias confirmed Thursday that the unit was still down and that backup oxygen was being fed to the station from bottled supplies. “Moscow believes there is blockage in the oxygen line,” he said, “and Padalka believes he can get the manifold cleared out.”
This task was attempted Friday. After three tries the unit started up -- but then shut down again within an hour. Engineers in Moscow decided to wait until next week to try again.
The three Elektron units on board the space station are the last of their kind. The company that manufactured them has gone out of business, and the engineer who almost single-handedly made the final adjustments of flight units died several years ago. Reportedly he retained some "trade secret" about the final adjustments of the devices -- and it died with him.
One of these units is "hard broken," NASA sources say, but the other, while broken, was thought to be reparable using a jury-rigged bypass pump system sent up on a supply drone earlier this year. The crew installed that system on Wednesday, Navias said, in what might be considered the spaceflight equivalent to a heart-bypass operation. While the system hasn't been tested yet, Moscow now believes they have a working backup unit if the current unit cannot be restarted.
The current unit was installed earlier this year, and began experiencing unwanted bubbling and consequent automatic shutdowns about two months ago. The shutdowns have been growing more and more frequent. For the two previous units, the same pattern of more and more frequent shutdowns was followed by a hard failure. The unit’s design lifetime was originally one year.
Other oxygen sources
The two crewmen are breathing oxygen at a known rate, converting it to carbon dioxide, which is still being safely scrubbed from the air by Russian and U.S. devices. “With Elektron off,” the NASA report stated, “ISS [would] reach the lower O2 limit in the cabin air in 7 days.”
Further reduction in oxygen would simulate conditions on Earth where people live at high elevations above sea level. Eventually -– in another week or two –- there would not be enough oxygen to sustain consciousness.
Long before that level is reached, NASA would implement backup oxygen generation processes -- and, indeed, they already have. These processes, however, use up limited supplies. The virtue of the Elektron system is that it is a regenerative system that uses waste water, and can operate indefinitely (barring mechanical failure) as long as more water and electrical power is provided.
Currently, according to NASA cargo manifests, there are 62 lbs. (28 kg) of O2 in a tank on board the Progress freighter now docked at the space station, enough for 16 days. Also, the station has 84 solid-fuel oxygen generators, or "candles," and at one man-day per canister, this would supply another 42 days of oxygen. There is also oxygen in tanks on the U.S. airlock module, although if used, it would be very difficult to replenish. “They’re fat on gas,” Navias insisted.
The next robot resupply flight is now scheduled for Nov. 26, and additional expendable supplies could be sent up then. That flight's cargo manifest already has been modified to carry more "oxygen candles," and possibly even a new tank to carry 150 lbs. of oxygen.
The oxygen problems aren't a surprise. On August 9, an internal NASA status report stated that “the Elektron oxygen generator continues to be a major source of trouble. Three days later, another report called it “the leading trouble spot aboard the ISS.” That report continued: “Current efforts [in Moscow] merely focus on outlining and developing a more reliable procedure for reacting to the increasingly frequent failures.”
But help is on the way. “Three completely redesigned units are currently in production,” a NASA source said. The new devices will not use the liquid-gel electrolyte system that has led to all previous units eventually breaking down. Instead, they will rely on a solid polymer electrolyte.
Delivery of the first of these units is expected “in March or April of 2005”, the source continued. How fast they really can be completed, tested and flight-qualified remains an open question in the severely underfunded Russian space program.
In the longer term, NASA is examining the chance of speeding up a U.S.-built oxygen generator to have it available in four years, rather than the currently scheduled six years.