The crew of the International Space Station (ISS) yesterday repaired one of its principal oxygen production units with new parts delivered over the weekend by an unmanned Progress supply ship. The failure of the onboard Elektron electrolysis machine in mid-September had prompted the American space agency to issue the first Spacecraft Emergency in the eight-year history of the ISS. In this month's news analysis article "Breathing Easy in Space Is Never Easy", our contributing editor on space technology, James Oberg, offers an insightful backgrounder on the nature of the emergency and the implications it posed to both the space station and the space shuttle program.
"The crew has replaced several parts of Elektron and put it back to work," Russian Federal Space Agency spokesman Valery Lyndin told the Associated Press. "Elektron has been working smoothly since Tuesday." The Elektron is the main producer of oxygen on the ISS. It uses electrolysis to turn surplus water into oxygen, dumping the useless hydrogen into space. It was shut down on 18 September after a visit by the crew of Space Shuttle Atlantis (see "The Popular ISS Motel"). When the crew reactivated the system the next day, just prior to the docking of a Soyuz transport carrying replacement crew members and an American space tourist, they smelled a noxious odor and turned it off again.
According to Oberg, they were smelling gas, potassium hydroxide, from the overheating of the chemicals used in the purification process the Elektron uses, which caused the system's rubber seals to begin melting, as well. Initially, the gases were interpreted by ground controllers to indicate a fire was occurring. Onboard inspection, however, confirmed a subsequent analysis of an overheating problem. Oberg writes:
The re-supply ship brought new sensors and a new valve—the old one is believed to have a burned-out solenoid, probably as a result of the overheating—and on Monday the crew members put them in, but to no avail. [A cosmonaut] told Moscow Mission Control that the unit appeared jammed with free-floating air bubbles much larger than desired, a problem encountered often in the past. He will spend the rest of the week trying to remedy it, and then he will activate the unit, coaxing it along as gently as possible. Success will be achieved not when the unit starts up, but when it continues to run for more than a few hours before its control system shuts it down.
Oberg notes that the overarching problem with the oxygen generators for NASA is its impact on future space shuttle flights. If the new crew—Russian cosmonaut Mikhail Tyurin, American astronaut Michael Lopez-Alegria, and German astronaut Thomas Reiter—can not sustain operation of the Elektron, then the resumption of shuttle flights will either have to be postponed from its scheduled start in December or the "safe-haven rule"—which dictates that that the ISS must be able to support a crew of as many as ten for up to a month in the event of potentially catastrophic damage to a shuttle requiring a complicated rescue scenario—will have to be adapted. Oberg explains that there are various other units onboard the ISS that could be hooked up, including the U.S. Oxygen Generation System delivered on a shuttle flight last summer, which still needs its water supply lines to be delivered. He observes:
The Catch-22 is that only a shuttle flight can reliably restore enough oxygen capacity for the station to host a stranded shuttle crew, yet without that capacity, no shuttle can safely fly.
For the time being, though, according to Moscow, the problem of keeping the oxygen flowing routinely is beginning to be addressed. We'll see, in the next few days, whether repair work on the vital unit will result in reliably sustainable operation. As Oberg writes, "Success will be achieved not when the unit starts up, but when it continues to run for more than a few hours before its control system shuts it down."