Luca Parmitano gives interview relating the terrifying moments when his spacesuit helmet began to fill with water

The Italian astronaut who nearly drowned in his helmet during a spacewalk on 16 July has shared more details about the experience, revealing how he frantically tried to devise a plan to save himself.

Luca Parmitano wrote in his blog, posted on Tuesday, that he stopped being able to see when water began sloshing around inside his helmet when he was outside the International Space Station.

"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," the former test pilot wrote. "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."

Parmitano, 36, a major in the Italian Air Force making just his second spacewalk, was unsure which direction to head in to reach the station's hatch. He tried to contact his spacewalk partner, American Christopher Cassidy, and mission control, but no one could hear him.

"I'm alone. I frantically think of a plan. It's vital that I get inside as quickly as possible," he wrote.

Parmitano realised that Cassidy – making his way back to the airlock by a different route – could come to get him. "But how much time do I have? It's impossible to know," he wrote.

That's when Parmitano remembered his safety cable. He used the cable recoil mechanism and its 1.4kg of force to pull himself back to the hatch. On the way back, he pondered what he would do if the water reached his mouth. The only idea he had, he said, was to open the safety valve on his helmet and let out some of the water.

"But making a 'hole' in my spacesuit really would be a last resort," he wrote.

Parmitano said it seemed like an eternity – not just a few minutes – until he peered through "the curtain of water before my eyes" and spotted the hatch. Cassidy was close behind. The astronauts inside quickly began repressurising the airlock to get to the spacewalkers.

"The water is now inside my ears and I'm completely cut off," he recalled.

He tried to stay as still as possible to keep the water from moving inside his helmet. He knew that because of the repressurisation, he could always open his helmet if the water overwhelmed him. "I'll probably lose consciousness, but in any case, that would be better than drowning inside the helmet," he wrote.

Cassidy squeezed his glove. Parmitano managed to give the universal OK sign.

"Finally, with an unexpected wave of relief," Parmitano saw the internal door open, and the crew pulled him out and his helmet off.

He remembers thanking his crewmates "without hearing their words because my ears and nose will still be full of water for a few minutes more".

Nasa has traced the problem to his spacesuit backpack, which is full of life-support equipment. But the precise cause is still unknown as the investigation continues into possibly the closest call ever during an American-led spacewalk. Nasa has suspended all US spacewalks until the problem is resolved.

The Russians will stage their second spacewalk in less than a week this Thursday to prepare for the arrival of a new lab by the end of this year. The two countries' suits are different.

More than a month has passed since the 16 July spacewalk and it's given Parmitano time to reflect on the dangers surrounding him. The first-time space flier will return to Earth in November.

"Space is a harsh, inhospitable frontier and we are explorers, not colonisers," he wrote. "The skills of our engineers and the technology surrounding us make things appear simple when they are not, and perhaps we forget this sometimes. Better not to forget."