Willingness to accept as routine minor amounts of water in a space-walking astronaut's helmet and a misdiagnosis of a previous water leak helped set the stage for an incident last summer that could have cost an International Space Station crew member his life, according to an analysis of the event.

In a 122-page report released Wednesday, a mishap investigation board identified a range of causes for the near-tragedy, including organizational causes that carried echoes of accident reports that followed the loss of the shuttles Challenger and Columbia and their crews in 1986 and 2003.

About 44 minutes into a 6.5-hour spacewalk last July, Italian astronaut Luca Parmitano noted that water was building up inside his helmet – the second consecutive spacewalk during which he reported the problem. Twenty-three minutes later, he and partner Chris Cassidy were ordered to end the spacewalk.

"The good news was that Luca was very close to the air lock when this happened," said Chris Hansen, space-station chief engineer and head of the board, during a briefing Wednesday that outlined the findings. "When we terminated the EVA, Luca had a pretty close path to the air lock."

Still, as Parmitano worked his way back to the air lock, water covered his eyes, filled his ears, disrupted communications, and eventually began to enter his nose, making it difficult for him to breathe. Later, when crew mates removed his helmet, they found that it contained at least 1.5 quarts of water.

NASA officials immediately set up the five-member mishap investigation board to uncover the broader causes behind the incident, even as a team of engineers at the Johnson Space Center worked to find the precise mechanical cause for the buildup of water.

Engineers traced the leak to a fan-and-pump assembly that is part of a system that extracts moisture from the air inside the suit and returns it to the suit's water-based cooling system. Contaminants clogged holes that would have carried the water to the cooling system after it was extracted from the air. The water backed up and flowed into the suit's air-circulation system, which sent it into Parmitano's helmet. The specific cause of the contamination is still under investigation.

Investigators noted that the ground team was slow to respond to Parmitano's initial report of water collecting in his helmet. Because the team wasn't aware that the water-separation system could fail in the way that it did, they didn't recognize how serious the situation was at that early stage.

That lack of awareness in turn stemmed from a misdiagnosis of a similar leak in the same suit when Parmitano used it during a spacewalk about a week earlier, according to the report.

At the time, the ground team concluded that the water came from a leaky drinking bag the astronauts wear inside the suits on their chests – although the investigators noted that no one could explain the basis for that conclusion. And at the time, no one challenged the leaky-bag hypothesis.

Investigators insisted they found no evidence of intimidation or an unwillingness to raise safety concerns. But tight schedules and a desire to ensure that crew members spent the maximum amount of time tending science experiments did play a role, the investigators found.

For instance, a detailed probe of the first major leak would have derailed preparations for the second spacewalk. Because a consensus had emerged that a leaky drinking bag was at fault, several members of the ground team told the panel that a more-detailed investigation was unlikely to yield results that would justify the time and expense of conducting it, and so none was conducted.

Investigators also identified deeper causes, one of which involved what some accident-investigation specialists have dubbed the "normalization of deviance" – small malfunctions that appear so often that eventually they are accepted as normal.

In this case, small water leaks had been observed in space-suit helmets for years, despite the knowledge that the water could form a film on the inside of a helmet, fogging the visor or reacting with antifogging chemicals on the visor in ways that irritate eyes.

When Parmitano first reported that water was gathering in his helmet during the second July spacewalk, the ground team discussed these effects, the investigators found. But because these conditions had come to be accepted as normal, no one expected a more-hazardous condition to emerge.

Investigators offered a broad range of recommendations to improve the way the ISS program handles this and similar issues in the future, many of which already are being implemented, NASA officials say.

While the ISS team performs at a very high level day in and day out, the report is sobering, they add.

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"The station has been operating for 15 years, and the suit has been around for 35 years. We have quite a bit of experience with the suit and the station," said Michael Suffredini, NASA's space-station program manager.

In its broadest sense the mishap investigation board's report is saying "that we always have to be very, very vigilant," he said. The ISS team needs to remember "to think twice about something that we think we understand."