Swimming with spacemen: training for spacewalks at NASA’s giant pool

Though the day dawns cool, the deck of NASA's Neutral Buoyancy Laboratory (NBL) remains warm—a side effect of keeping 6.2 million gallons of water at a constant 86°F. I stare down into the largest indoor body of water in the world and feel a surge of vertigo. Here, astronauts practice for spacewalk missions at the International Space Station (ISS), and today I'll watch them do it.

The pool measures 202 feet long, 101 feet wide, and 40 feet deep, extending 20 feet down from the elevated deck and then an additional 20 feet below the floor level. Its wall and floor are white, though they're smudged and darkened from years of repositioning model test stands. Spread throughout the water are life-sized component mock-ups of the ISS, looking exactly like some giant child's Tinker Toy set. Refraction causes the perspective to bend sharply away until it's obscured by the reflection of the ceilings and walls.

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