Nasa could have prevented last summer's near-drowning of a spacewalking astronaut at the International Space Station, an investigation panel has concluded.
Italian astronaut Luca Parmitano's helmet filled with water during his second spacewalk on July 16. He barely made it back inside alive.
But according to the panel's report, his helmet also had leaked one week earlier at the end of his first spacewalk.
The panel said the space station team misdiagnosed the first failure and should have delayed the second spacewalk until the problem was understood.
"This event was not properly investigated," said Chris Hansen, Nasa's chief space station engineer and chairman of the investigation board created by the space agency after the close call.
"There was a lack of understanding in the severity of the event," Hansen said during a news conference Wednesday (NZT Thursday).
Space station officials presumed the leak was from a water drink bag in the suit when, in fact, that was not the culprit, he noted.
Investigators said Parmitano's "calm demeanour" during the incident quite possibly saved his life. Now 37, Parmitano was a former test pilot and an officer in the Italian Air Force. He was on his first space mission and returned to Earth in November.
The precise cause of the water leakage was still under review.
Contamination clogged several small holes in a pump mechanism inside Parmitano's spacesuit, part of its cooling system, and water ended up in the helmet, Hansen noted. Engineers did not yet know the source of the aluminum silicate contamination.
Nasa almost ended up with another disaster following Parmitano's close call. The day after his near drowning, the astronauts used a vacuum cleaner to dry the spacesuit and accidentally sucked oxygen out of a tank.
"The hazardous mix of electricity and pure O2" could have sparked a fire, the report stated.
Mission Control had aborted the spacewalk once the water began to rise to alarming levels in Parmitano's helmet; the spacewalk by Parmitano and American astronaut Chris Cassidy lasted one and a half hours, versus the anticipated six hours.
So much water filled Parmitano's helmet - an estimated 1.5 litres - that he could barely see and could not hear or speak. He said he made his way back into the space station by relying on the position of his safety tether.
Nasa was contrite following the release of the report, saying it could and would do better.
"We're taking it very seriously," said space station programme manager Mike Suffredini.
He hoped the engineering investigation was wrapped up by year's end.
Bill Gerstenmaier, head of Nasa's human exploration and operations mission, said the spacewalk probably should have ended quicker on July 16.
"We can all improve and do better," Gerstenmaier said.
US spacewalks were put on hold after the incident. An exception was made right before Christmas so two US astronauts could repair a crippled cooling system at the orbiting outpost. As a precaution, they had snorkels in their suits and water-absorbent pads in their helmets, but there were no problems.
Six men currently reside on the space station - three Russians, two Americans and one Japanese.
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