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.
Cernan, ultimately, didn't lose consciousness; he did, however, lose some of his sight. The space-walker's body heat and the sweat it generated fogged up the helmet of his suit. Suddenly, Cernan was seeing the spaceship before him as if through a frosted window. And he had no means of fading the fog. NASA aborted the EVA -- and, as a result of Cernan's experience, began applying anti-fogging chemicals to the interior surfaces of the spacesuit helmets that would follow.
Anti-fogging chemicals, however, don't do much to prevent liquid from seeping into helmets from elsewhere in the suit -- as seems to have happened to Parmitano. In 2004, halfway through a standard spacewalk, the cosmonaut Alexander Kaleri startled Mission Control in Moscow with an announcement: "It's amazing. I have rain inside the helmet," he said. The "full condensation" he was experiencing was accompanied, alarmingly, by a rise in Kaleri's suit temperature -- which would not prove to be hazardous, but which would offer immediate evidence of a suit malfunction. Ground Control aborted the spacewalk -- though it had to repeat the decision multiple times before Kaleri and his fellow spacewalker, the American Mike Foale, acquiesced: both had planned to retire after the mission, and were reluctant to bring their final spacewalking experiences to premature ends.
Sometimes, however, in-helmet moisture is more of an annoyance than an EVA-aborting danger. Space walks being long and, as Cernan demonstrated, arduous endeavors, NASA has sometimes seen fit to provide astronauts with snacks to keep them energized during their EVAs. Chris Hadfield recalled one such experiment -- with snack bars. The bars were made of the same dried fruit paste as Fruit Roll-Ups, and they were positioned within the helmet so that astronauts, the thinking went, could bend their heads down, take a bite of the stuff, and go about their space-walking. The catch was that the bars were mounted, as it happened, next to the helmets' drinking tubes -- and those tubes tend to leak. Just a little bit. But enough to render the fruit bar, Hadfield noted, a "gooey mass." So "we just stopped using them."
It may well have been a leaky drinking tube -- the same kind that undried the dried fruit -- that aborted Parmitano's spacewalk this morning. Parmitano, for his part, is convinced that the liquid was something other than drinking water. As Chris Cassidy told Mission Control: "To him, the water clearly did not taste like our normal drinking water." To which a Parmitano, newly dried and newly smiling, chimed in: "Just so you know, I'm alive and I can answer those questions, too."