Astronauts Tim Kopra (NASA) and Tim Peake (ESA) prematurely ended their spacewalk outside the International Space Station on Friday afternoon after Kopra reported a small water bubble had formed inside his helmet.
The duo had been nearly five hours into a planned six hour spacewalk when Kopra noticed the water in his helmet. The main objective of the historic spacewalk (it was the first to include a British national) was to replace a voltage regulator that had caused a power outage at the station last November. According to Kopra, the water bubble was about four inches long and growing in thickness when Mission Control in Houston terminated the spacewalk.
Kopra and Peake had already successfully completed the main objective of the spacewalk by restoring the ISS to full power when the decision was made to return to the ISS. Once inside, fellow ISS astronauts helped Team Tim doff their spacesuits after which they measured the water which was in Kopra's helmet. According to Space Station commander Scott Kelly, Kopra's helmet contained about 15 cubic centimeters of water.
The decision was no doubt made in light of a similar, albeit more severe, incident that occurred to astronaut Luca Parmitano in 2013. While on a spacewalk with Chris Cassidy, Parmitano noticed his helmet was beginning to rapidly fill with a "funny tasting" water, which began to get in his eyes, mouth and ears. He later described his terrifying brush with drowning in space in a blog post:
I 'feel' that something is wrong. The unexpected sensation of water at the back of my neck surprises me—and I'm in a place where I'd rather not be surprised. As I move back along my route towards the airlock, I become more and more certain that the water is increasing. I feel it covering the sponge on my earphones and I wonder whether I'll lose audio contact.
The water has also almost completely covered the front of my visor, sticking to it and obscuring my vision. I turn 'upside-down', two things happen: the Sun sets, and my ability to see – already compromised by the water – completely vanishes, making my eyes useless; but worse than that, the water covers my nose – a really awful sensation that I make worse by my vain attempts to move the water by shaking my head. By now, the upper part of the helmet is full of water and I can't even be sure that the next time I breathe I will fill my lungs with air and not liquid. To make matters worse, I realize that I can't even understand which direction I should head in to get back to the airlock.
Parmitano made it back to the airlock just in the nick of time. When his helmet was removed his ISS colleagues measured over 1 liter of water in his helmet, which makes the 15 cubic centimeters of water in Kopra's helmet seem paltry in comparison. NASA agreed, writing that "the crew was never in any danger" and that Friday's situation was not an emergency, but simply a case where it was better to be safe than sorry.
The suit Kopra was wearing was actually the same as the one worn by Parmitano when he nearly drowned. The suit had since been refurbished and used on multiple space walks (the most recent instance was a month prior to Friday's incident) without any problems. In Parmitano's case, the cause of the leak was a faulty Water Separator Pilot Tube, which allowed water to leak into the suit's ventilation loop. The origin of the water in Kopra's helmet has yet to be ascertained.
In the aftermath of the Parmitano incident NASA added some new precautions for spacewalks, including adding absorbent pads to the suit's helmet, to help stave off similar close-calls in the future. According to NASA, data from Kopra's spacewalk, including how much water was absorbed by the helmet pads, is already being studied by engineers to determine the source of the water leak.