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Breathing Easy on the Space Station

Breathing with Machines

A Science@NASA story by Patrick L. Barry

The oxygen that humans and animals breathe on Earth is produced by plants and other photosynthetic organisms such as algae.
The oxygen that humans and animals breathe on Earth is produced by plants and other photosynthetic organisms such as algae.

Hydrogen that's leftover from splitting water will be vented into space, at least at first. NASA engineers have left room in the ECLSS hardware racks for a machine that combines the hydrogen with excess carbon dioxide from the air in a chemical reaction that produces water and methane. The water would help replace the water used to make oxygen, and the methane would be vented to space.

"We're looking to close the loop completely, where everything will be (re)used," Roman said. Various uses for the methane are being considered, including expelling it to help provide the thrust necessary to maintain the Space Station's orbit.

At present, "all of the venting that goes overboard is designed to be non-propulsive," Perry said.

The ISS will also have large tanks of compressed oxygen mounted on the outside of the airlock module. These tanks will be the primary supply of oxygen for the U.S. segment of the ISS until the main life support systems arrive with Node 3 in 2005. After that, the tanks will serve as a backup oxygen supply.

Last week, while the crew were waiting for activation of a water electrolysis machine on the Zvezda Service Module, they breathed oxygen from "perchlorate candles," which produce O2 via chemical reactions inside a metal canister.

"You've got a metallic canister with this material (perchlorate) packed inside it," Perry explained. "They shove this canister into a reactor and then pull an igniter pin. Once the reaction starts, it continues to burn until it's all used." Each canister releases enough oxygen for one person for one day."

"It's really the same technology that's used in commercial aircraft," he continued. "When the oxygen mask drops down, they say to yank on it, which actuates the igniter pin. That's why you have to give it a tug to begin the flow of oxygen."


Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 04/07/2002
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