Ultima Thule

In ancient times the northernmost region of the habitable world - hence, any distant, unknown or mysterious land.

Sunday, July 16, 2006

Flushed with excitement -- shuttle astronauts deliver a breath of fresh air to the Space Station

By Aussiegirl

But does it come with a Glade air-freshener? Shuttle astronauts delivered a unique piece of machinery to the International Space Station -- a device that turns astronaut pee into oxygen. I'm stumped for further comment.

Wired News: Don't Flush It -- Breathe It Don't Flush It -- Breathe It

This week's space shuttle mission will bring a breath of fresh air to the International Space Station with the delivery and installation of a new device from NASA that can turn astronaut pee into oxygen.

NASA's Oxygen Generation System, or OGS, is essentially a copycat of Russia's Elektron, which uses electrolysis to turn purified urine into breathable air and has been used on the space station for the past six years. The new setup offers an important backup for the existing systems, experts said, and a chance to test technology that could prove instrumental for deep-space exploration and colonization.

"Russia tends to operate the Elektrons as long as possible, far beyond their planned lifetimes," said Robert Ash, an aeronautical engineer and amateur space historian. "When an Elektron fails, one of the backup oxygen sources must be used until the Elektron is repaired or a replacement is sent up. If there's an additional source of oxygen then that adds more backup capacity and increases safety. In addition, the U.S. oxygen generators will permit the size of the crew to be increased from three to six. But the more important long-term reason is recycling air and water will be critical for U.S. missions to the moon and Mars in the future. The space station is a good place to check out equipment under realistic conditions."

The current shuttle mission is carrying the refrigerator-size OGS, but it won't be put into use until a urine-water recovery system is launched on a future shuttle mission. That system will use a vacuum-distillation system to remove the dissolved solids in urine so the resulting water is pure enough to put into the OGS. A prototype of the vacuum-distillation system was tested on the space shuttle Columbia's last mission in January 2003.

The devices could hold the key to a major hurdle for extended space travel and off-planet colonization. The topic has been in the spotlight recently following remarks from physicist Stephen Hawking and ex-astronaut John Young suggesting that mankind must plot an escape from Earth in order to fend off extinction by environmental catastrophe.

Bringing oxygen into space is a costly logistical puzzle.

Each day the human body needs 1.5 pounds of oxygen. For space missions of less than three weeks, the best solution is large containers of liquid oxygen. But for long missions, like extended stays on space stations, it isn't practical to keep the oxygen below the super-cold 297 degrees Fahrenheit needed to keep it liquid. And every pound of oxygen you have to carry up from Earth is a pound of payload that could be used for something else.

According to Ash, Russia started to use Solid Fuel Oxygen Generators, or SFOGs (pronounced "ess fogs"), on its Salyut space stations in the 1970s. The same units were used to generate oxygen on non-nuclear submarines. The canisters are filled with lithium perchlorate. When ignited, the oxygen candles burn with an intense flame and give off 1.74 pounds of oxygen. After the candle is burned out, all that's left is some lithium chloride ash. These systems are generally considered extremely reliable, but a problem with an SFOG on the Mir space station on Feb. 23, 1997, resulted in an out-of-control fire that lasted for almost 15 minutes.

In an interview shortly after he returned from Mir, astronaut Jerry Linenger recalled, "It was a 2-foot-long flame torch." Because the fire had its own source of oxygen, it couldn't be snuffed out; all Linenger and commander Valeri Korzun could do was spray fire extinguishers on the bulkhead nearby to keep its temperature as cool as possible and hope it wouldn't collapse.

Russian investigators believe a contaminated seal was the culprit in this case and it was just an unlucky break: You ignite 1,000 matches, one of them might burn you by accident. SFOGs continue to be used on the International Space Station as a backup oxygen source.

An alternative to SFOGs is to bring oxygen to the space station in compressed air bottles. But the bulky tanks are heavy and don't carry much oxygen. Russia's Elektron turned out to be a better solution when it was used on Mir in the mid-1980s. About the size of a scuba tank, the Elektron takes the space station's waste water and uses electrolysis to split it into hydrogen and oxygen. The hydrogen is dumped overboard, while the oxygen is added to the crew cabin.


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