Imagine you're an astronaut. Imagine you're on a spacewalk. Imagine, in other words, that you are whirling above the Earth at more than 17,000 miles an hour, the only thing between you and the deadly vacuum of space a padded suit, a hardened helmet, and an umbilical tether that you hope is really, really strong.
Now imagine that your helmet, suddenly, starts filling with liquid. At first you think it's sweat, condensing as it leaves your skin. But then more liquid starts to seep in. You think it's water. But you're not entirely sure. And there's more of it, and more of it, clinging to your face, clogging your ears, covering your eyes.
Pretty much the stuff of nightmares, right? The air in your helmet -- the thing most precious, because most limited, in a spacewalk -- is suddenly competing for space with something else. And you don't know, exactly, what that something else actually is. The only thing you know for sure is that more and more of it is surrounding you. And your helmet is not getting any bigger.
Well, that living nightmare just happened to one of the people living on the International Space Station. This morning, Italian astronaut Luca Parmitano was conducting, with the American Chris Cassidy, a routine spacewalk to repair cables on the exterior of the Station. Things were going normally when, suddenly, Parmitano alerted Cassidy and his crewmates to his suddenly-moisture-filled helmet. At first, Parmitano thought the mystery liquid was, indeed, sweat: work done in the confines of a spacesuit, after all, requires a great deal of exertion. But there was too much of it. It had to be something else. "It's a lot of water," Parmitano said.
And this was not a small problem. Recall that an astronaut's spacesuit is a spaceship for one, an astronaut's only lifeline back to the Station and, with it, the Earth. Recall as well that, in microgravity, liquid doesn't pool -- it floats. It clings. At one point, per one account, "there was so much water inside Parmitano's ears and around his face that he couldn't hear or speak to communicate with the other astronauts."
"Squeeze my hand if you're fine," Cassidy said to Parmitano.
There was no squeeze. NASA abruptly aborted the spacewalk, and the crew pulled Parmitano back into the Station, freeing him from his suit. The first order of business: toweling off his face and head. "He looks miserable, but is OK," the crew told Mission Control after they'd dried him off, balls of water flying away as they did so.
The crew, and Mission Control, are still trying to determine the cause of the liquid incursion. Cassidy, for his part, suspects it was water seeping from Parmitano's drink bag. He said it looked like a half-liter -- about 2 cups -- of water had leaked out into Parmitano's helmet.
Parmitano, it turns out, is only the latest astronaut to experience the waking nightmare that is the liquid-filled helmet. As early as 1966, during the second-ever U.S. EVA, astronaut Gene Cernan experienced a similar problem. Space-walking was new back then, and NASA, it seems, had underestimated exactly how much work -- "work" in the sense of "manual labor" -- would be required of the astronaut doing the space walk. "Lord, I was tired," Cernan would later recall of that early EVA. "My heart was motoring at about 155 beats per minute, I was sweating like a pig, the pickle was a pest, and I had yet to begin any real work." At one point, as the walk progressed, Cernan's heart rate shot up to 195 beats per minute -- and flight surgeons began fearing that he would pass out from the exertion.