A contaminated spacesuit cooling system pump caused the water leak that put the life of astronaut Luca Parmitano at risk despite the engineers originally believing the leakage was nothing more than a ruptured drink bag.
Nasa has released results of the investigation into the July 2013 incident at a press conference on Wednesday, revealing an earlier oversight caused the Italian astronaut to nearly drown during a spacewalk.
On 16 July Luca Parmitano, performing a spacewalk with his American colleague Chris Cassidy, was forced to return into the International Space Station’s airlock after more than 1.5 litres of water spilled into his helmet, obstructing his vision and complicating his breathing.
However, it was not the first incident involving water leakage in Parmitano’s Nasa-manufactured spacesuit. Only one week earlier, on 9 July, he experienced a similar, though smaller, problem.
Back then, Nasa engineers attributed the leakage to a ruptured drink bag and left the incident without launching a proper investigation.
"Had the issue been discussed in more detail ... the team likely would have realised that the water experienced in (Parmitano's) helmet was 'out of family' and needed to be investigated further," said Nasa’s space station chief engineer Chris Hansen, who chaired the investigation.
As a result of this misinterpretation, Parmitano was allowed to perform the doomed spacewalk one week later with his broken spacesuit. The action had to be aborted after 45 minutes. By the time the astronaut, assisted by his colleague Cassidy, made it to the airlock, water had damaged the radio inside his helmet and he lost his communication channels.
Nasa has a history of critical technical oversights that cost lives in the past. In 2003, foam insulation falling off the space shuttle's fuel tank during launch caused wing damage that destroyed the Columbia as it glided through the atmosphere for landing, killing seven astronauts.
The 1986 Challenger accident, which also killed seven astronauts, was later blamed on a booster rocket seal that failed during its launch in cold weather.
"The message to all of us is to be really vigilant and to really communicate," said Nasa spaceflight chief William Gerstenmaier.
"We're not hiding this stuff. We're actually out trying to describe these things, describe where we can get better. I think that's how we prevent Columbias and Challengers," he said.
The 220-page report into the Parmitano accident includes 49 recommendations to improve safety protocols, training and communication. Nasa said it will implement the findings before scheduling its next series of spacewalks, targeted for this summer.