Mounting delays stress space station systems

There are currently 106 such canisters aboard the space station. While some may turn out not to be functional, this is still enough to provide the two-man crew with about 50 days of breathing air — more than enough to last until the next supply ship arrives with more oxygen bottles in about a month.

Each canister is loaded into a special chamber and activated by firing a spring-driven mechanical squib (there are two chambers aboard the station, but the squib mechanism in one of them has already broken). This initiates “thermal decomposition" of the material at an internal temperature of up to 900 degrees F, releasing oxygen — and about 800 watts of waste heat. (For comparison, an oven in a home gives off about 350 watts.)

The malfunction in February 1997 saw a torch-like flame burst from the front of the canister, filling the station modules with choking, blinding smoke and cutting off access to one of the station’s two bail-out capsules.

INTERACTIVE Space station timeline A step-by-step construction guide

Had the chemical canister been oriented in a slightly different direction, space engineers later realized, the flame would have quickly burned through the cardboard-thick aluminum hull and outrushing air would have briefly fanned the flames until the crew suffocated.

If for some reason the oxygen candles become unusable, or are used up before a new supply mission can be sent to the station, the crew has recourse to the fourth and last source of breathable air: oxygen tanks attached to the U.S. ‘Quest’ airlock. They are thought to contain about 362 pounds of gas, adequate for about 90 days of breathing.

Long range implications
As new questions arise about the expected repair schedule for the Elektron unit, some safety officials at NASA have privately questioned what this means for the space shuttle's key "safe haven" concept. Under return to flight guidelines, if something were to go wrong with a NASA space shuttle in the future, crews are supposed to camp out on the station until a rescue shuttle can be launched.

Had the shuttle been launched last week as originally hoped, the station would have had enough emergency oxygen on hand even without Elektron for the shuttle crew and the station crew to last until rescue. But as the shuttle is delayed into July, and perhaps even into September, the lack of a functioning oxygen generation system means the station crew is eating into consumable supplies that would otherwise have been available if the "safe haven" was needed.

Editor's note: Due to miscommunication during editing, an earlier version of this story said that Phillips would achieve a record for longest time spent in space by an American over the course of a career. The record is the longest time in the course of a single flight.

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