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Pirst, there was the Water Immersion Facility (WIF) installed in Bldg. 5 in 1966. Next, the WIF was moved to Bldg. 260, occupying a tank previously used to practice splashdowns and recoveries at sea. Then, in 1380, the WETF was born in Bldg. 29, a building that had previously held a centrifuge.
The NBL will be completed in June 1993. And it will be a first-of-a-kind.
Due to its 60-foot depth, astronauts will have to decompress following a training session. They will enter the pool from the surface to begin training, but they will leave through an underwater door in the side of the pool, 30 feet down. The door will lead to a more than three stories tall, 26-foot diameter, solid stainless steel exit chamber, half-filled with water and half-filled with a compressed atmosphere. Astronauts will exit the water there, doff their suits and then move through a common air lock to either of two decompression chambers, both capable of being used as medical facilities or as decompression and debriefing areas.
The decompression chambers are designed to take subjects to a pressure equal to 160 feet underwater, a requirement for treatment of decompression sickness, commonly called "the bends."
"The exit chamber permits us to decompress suited crewmen in their shirt sleeves," Hammersley said. "Without it, they would have to make long decompression stops at certain depths on the way up."
Scuba divers won't have to decompress; they will be rotated once an hour. And they'll breathe nitrox, a compressed air mixture consisting of about 40 percent oxygen, 60 percent nitrogen, instead of the standard 20 percent oxygen, 80 percent nitrogen compressed air in scuba tanks. The oxygen-rich nitrox will provide an additional safeguard against decompression sickness that can be caused by frequent deep dives.
The pool will be heated to 84 degrees, the optimum temperature for diving safety. Each of the 14 million gallons of water it holds will be filtered once every 24 hours, at a rate of 10,000 gallons per minute through filters that remove particles smaller than human red blood cells. A slower, 1,000 gallon-per-minute bank of filters will continually "polish" the water, removing particles as small as those that make up smoke.
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