"Prior to arriving on the station, the previous crew were out on a space walk and one of the astronauts had a failure with his cooling system and his helmet started filling up with water.
"That was clearly an emergency type of situation and they had to abort the mission and get him in as quickly as possible."
The 49-year-old said one of his first jobs when he boarded the ISS, was to fix that space suit.
It was a difficult because the suits were made during the space shuttle era and repairs were to be done on the ground.
"Little things like nuts and bolts can float away and that makes it more challenging."
He said no space walks were planned for his time on the ISS, but when the cooling system broke down, it became necessary to send astronauts out the hatch.
"The interesting part was when they called me up and said, 'OK you're going to go out on a space walk, but you're going to wear the suit that you just fixed'.
"That certainly makes you pause and think, OK I hope I did a good job."
Despite his initial concerns, his first space walk was a success and he now has a view of Earth he will never forget.
"Looking down at the earth is an incredible scene - a humbling experience."
His stories went down a treat with Dunedin school pupils at the Otago Museum Planetarium yesterday, when he gave a talk about space and life as an astronaut in a bid to inspire the next generation.
Col Hopkins also gave a public talk in the museum's Hutton Theatre last night, and will travel around Otago today, where he will explore the Otago Central Interplanetary Cycle Trail (a one-hundred-million-to-one scale model of the Solar System), officially open an exhibition of astrophotography in Naseby, speak at a Centre for Space Science Technology event in Alexandra, and a Catalyst Trust event in Queenstown.
He returns to Houston tomorrow.